Oil shale pyrolysis: benchscale experimental studies and modeling

Oil shale is a complex material that is composed of organic matter, mineral matrix and trace amount of bound and/or unbound water. The endothermic decomposition of the organic matter generates liquid and gaseous products. The yield and the desired quality of the product (shale oil) are controlled by the operational conditions. Pyrolysis of a small batch of finely ground oil shale provides chemically controlled intrinsic kinetic rate of organic decomposition. Pyrolysis of large size block/core samples is governed by temperature distributions and the time required for product expulsion. Heat and mass transfer considerations influence the distribution of products and alter the yield and quality. The experimental studies on oil shale pyrolysis performed in this work were designed to understand the relevant coupled phenomena at multiple scales. Oil shale in the Mahogany zone of the Green River formation was used in all experiments. Experiments were conducted at four scales, powdered samples (100 mesh) and core samples of ¾", 1" and 2.5" diameters. Batch, semibatch and continuous flow pyrolysis experiments were designed to study the effect of temperature (300°C to 500°C), heating rate (1°C/min to 10°C/min), pressure (ambient and 500 psi) and size of the sample on product formation. Comprehensive analyses were performed on reactants and products - liquid, gas and spent shale. The activation energies of organic decomposition derived from advanced isoconversional method were in the range of 93 to 245 kJ/mol with an uncertainty of about 10%. Lighter hydrocarbons evolved slightly earlier and their amounts were higher in comparison to heavier hydrocarbons. Higher heating rates generated more alkenes compared to respective alkanes and as the carbon number increased, this ratio decreased. Oil yield decreased and the amount of coke formed increased as the sample size and/or pressure increased. Higher temperature, higher heating rate and low pressure favored more oil yield. The quality of oil improved with an increase in the temperature, pressure and size of the sample. A model in COMSOL multiphysics platform was developed. A general kinetic model was integrated with important physical and chemical phenomena that occur during pyrolysis. The secondary reactions of coking and cracking in the product phase were addressed. The multiscale experimental data generated and the models developed, provide an understanding of the simultaneous effects of chemical kinetics, heat and mass transfers on oil quality and yield. The comprehensive data collected in this study will help advance the move to large scale oil production from the pyrolysis of shale.

OIL SHALE PYROLYSIS: BENCHSCALE EXPERIMENTAL STUDIES AND MODELING by Pankaj Tiwari A dissertation submitted to the faculty of The University of Utah in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Chemical Engineering The University of Utah August 2012Copyright ©Pankaj Tiwari 2012 All Rights Reserved The University of Utah Graduate School STATEMENT OF DISSERTATION APPROVAL The dissertation of Pankaj Tiwari has been approved by the following supervisory committee members: Milind D. Deo , Chair 5/30/2012 Eric G. Eddings , Member 5/30/2012 Edward M. Trujillo , Member 5/30/2012 Hong Y. Sohn , Member 5/30/2012 Edward M. Eyring , Member 5/30/2012 and by JoAnn Lighty , Chair of the Department of Chemical Engineering and by Charles A. Wight, Dean of The Graduate School. ABSTRACT Oil shale is a complex material that is composed of organic matter, mineral matrix and trace amount of bound and/or unbound water. The endothermic decomposition of the organic matter generates liquid and gaseous products. The yield and the desired quality of the product (shale oil) are controlled by the operational conditions. Pyrolysis of a small batch of finely ground oil shale provides chemically controlled intrinsic kinetic rate of organic decomposition. Pyrolysis of large size block/core samples is governed by temperature distributions and the time required for product expulsion. Heat and mass transfer considerations influence the distribution of products and alter the yield and quality. The experimental studies on oil shale pyrolysis performed in this work were designed to understand the relevant coupled phenomena at multiple scales. Oil shale in the Mahogany zone of the Green River formation was used in all experiments. Experiments were conducted at four scales, powdered samples (100 mesh) and core samples of ¾", 1" and 2.5" diameters. Batch, semibatch and continuous flow pyrolysis experiments were designed to study the effect of temperature (300°C to 500°C), heating rate (1°C/min to 10°C/min), pressure (ambient and 500 psi) and size of the sample on product formation. Comprehensive analyses were performed on reactants and products - liquid, gas and spent shale. The activation energies of organic decomposition derived from advanced isoconversional method were in the range of 93 to 245 kJ/mol with an uncertainty of about 10%. Lighter hydrocarbons evolved slightly earlier and their amounts were higher in comparison to heavier hydrocarbons. Higher heating rates generated more alkenes compared iv to respective alkanes and as the carbon number increased, this ratio decreased. Oil yield decreased and the amount of coke formed increased as the sample size and/or pressure increased. Higher temperature, higher heating rate and low pressure favored more oil yield. The quality of oil improved with an increase in the temperature, pressure and size of the sample. A model in COMSOL multiphysics platform was developed. A general kinetic model was integrated with important physical and chemical phenomena that occur during pyrolysis. The secondary reactions of coking and cracking in the product phase were addressed. The multiscale experimental data generated and the models developed, provide an understanding of the simultaneous effects of chemical kinetics, heat and mass transfers on oil quality and yield. The comprehensive data collected in this study will help advance the move to large scale oil production from the pyrolysis of shale. To My FamilyTABLE OF CONTENTS ABSTRACT…………………………………………...…………………………………iii LIST OF TABLES……………………………………….….……………………………ix LIST OF FIGURES………………………………………………………………..…… xii ABBREVIATIONS..………………………………………………………………… ...xx NOMENCLATURE………………………………………………………………..…..xxii ACKNOWLEDGMENTS……………………………………………………………...xxv 1. INTRODUCTION .......................................................................................................... 1 1.1. Research Objectives ................................................................................................. 3 1.2. Background .............................................................................................................. 4 1.3. Significance of the Research and Original Contribution .......................................... 7 1.4. Thesis Outline ........................................................................................................... 8 2. LITERATURE REVIEW ............................................................................................. 10 2.1. Oil Shale Pyrolysis Process .................................................................................... 10 2.2. Mechanism of Oil Shale Pyrolysis and Product Formation ................................... 13 2.3. Complexity Involved in the Process ...................................................................... 16 2.4. Kinetic Analysis of Organic Decomposition ......................................................... 17 2.4.1. Isothermal and Nonisothermal Kinetic Studies ............................................... 20 2.5. Compositional Analysis of Pyrolysis Products ...................................................... 21 2.6. Effect of Operational Parameters on Oil Shale Pyrolysis ...................................... 26 2.7. Modeling of Oil Shale Pyrolysis ............................................................................ 30 2.8. Hydrous Pyrolysis .................................................................................................. 32 3. EXPERIMENTAL METHODS AND ANALYTICAL TECHNIQUES ..................... 33 3.1 Experimental Section .............................................................................................. 33 3.1.1. Material............................................................................................................ 33 3.1.2. Experimental Procedure .................................................................................. 34 3.2. Analytical Techniques ............................................................................................ 43 vii 3.2.1. Material Characterization ................................................................................ 43 3.2.2. Compositional Analysis................................................................................... 45 3.2.3. Physical Properties Estimation ........................................................................ 49 4. RAW MATERIAL CHARACTERIZATION .............................................................. 51 4.1. Elemental Analysis ................................................................................................. 51 4.2. Thermal Gravimetric Analysis ............................................................................... 51 4.3. X- Ray Diffraction Analysis .................................................................................. 55 4.4. TGA-DSC Analysis................................................................................................ 57 4.5. High Pressure TGA Pyrolysis ................................................................................ 57 5. KINETIC ANALYSIS OF OIL SHALE PYROLYSIS TGA DATA .......................... 61 5.1. Nonisothermal TGA Pyrolysis of Oil Shale ........................................................... 61 5.2. Kinetic Analysis - Advanced Isoconversional Methods........................................ 64 5.2.1. Kinetic Analysis - Advanced Parameter Fitting Approaches ......................... 67 5.3. Kinetic Analysis Results - Advanced Isoconversional Methods ........................... 67 5.3.1. Kinetic Analysis Results- Advanced Parameter Fitting Models .................... 73 5.3.2. Comparison of the Different Kinetic Models Used ......................................... 75 5.4. Kinetics of Isothermal Decomposition ................................................................... 80 5.5. Pyrolysis Kinetics of Different Oil Shales ............................................................. 83 6. COMPOSITIONAL AND KINETIC ANALYSIS USING TGA-MS ......................... 84 6.1. TGMS Analysis of Powdered Oil Shale (PO) ........................................................ 85 6.2. Derivation of Kinetic Parameters ........................................................................... 94 7. MULTISCALE PYROLYSIS AND BULK PRODUCT ANALYSIS ........................ 98 7.1. Pyrolysis of Powdered Samples ............................................................................. 98 7.1.1. Batch Pyrolysis of Powdered Samples ............................................................ 98 7.1.2. Semibatch Pyrolysis of Powdered Samples .................................................. 102 7.1.3. Continuous Flow Pyrolysis of Powdered Samples ........................................ 106 7.2. Pyrolysis of 3/4" Core Samples ........................................................................... 107 7.2.1. Continuous Flow Pyrolysis of ¾" Core - Effect of Temperature ................. 107 7.3. Pyrolysis of 1" Core Samples............................................................................... 122 7.4. Pyrolysis of 2.5" Core Samples ........................................................................... 128 7.5. Summary of Multiscale (benchscale) Pyrolysis ................................................... 132 8. OIL SHALE PYROLYSIS: HYDROUS TREATMENT .......................................... 137 8.1. Pyrolysis of Water-Soaked Oil Shale Samples .................................................... 137 8.2. Hydrous and Anhydrous Pyrolysis ....................................................................... 140 8.3. Analyses of Water Phase ...................................................................................... 144 viii 9. HETEROGENITY IN THE RAW MATERIAL ........................................................ 148 9.1. Material Characterization ..................................................................................... 148 9.2. Pyrolysis of GR Core Samples ............................................................................. 149 9.3. TGA Pyrolysis of Isolated Kerogen ..................................................................... 154 10. MATHEMATICAL MODELING OF OIL SHALE PYROLYSIS ......................... 157 10.1. Modeling Framework ......................................................................................... 157 10.2. Governing Equations and Solution Methodology .............................................. 159 10.3. Model Results and Observations ........................................................................ 164 10.4. Summary of the Model Results .......................................................................... 171 11. CONCLUSIONS AND FUTURE WORK ............................................................... 172 11.1. Conclusions ........................................................................................................ 172 11.2. Future Work ....................................................................................................... 177 A. TGA ANALYSES OF OIL SHALE……………………………………………......179 B. KINETIC EXPRESSION: CONVENTIONAL MODELS……...……………...…..185 C. EXPERIMENTAL DATA…………………………….. …………………………..197 D. TEMPERATURE AND PRESSURE PROFILES………………………………….203 E. PHYSICAL PROPERTIES OF SHALE OILS………..…………………................209 F. GLOSSARY………………………………………………………………………...210 REFERENCES ............................................................................................................... 213 LIST OF TABLES Table Page 2- 1 Reaction network (organic, water and mineral reactions) during the pyrolysis of oil shale. ........................................................................................................... 14 3- 1 List of the oil shale samples and scales (size) used to study the pyrolysis process with different apparatus. .......................................................................... 36 3- 2 List of the experimental apparatus, configurations and conditions used to study the pyrolysis process. .................................................................................. 36 3- 3 Operating conditions of gas chromatography for cool on column injection (GC 6890) and split injection (GC 6890). ............................................................ 47 4- 1 Elemental analysis of oil shales. .......................................................................... 51 4- 2 Minerals present in oil shales (weight percent of the total identified crystal minerals). .............................................................................................................. 56 5- 1 Analysis criteria for the nonisothermal TGA pyrolysis data. .............................. 63 5- 2 Parameters obtained using selected kinetic models available in kinetic05. ......... 74 5- 3 Time required to achieve the complete conversion of the organic matter during true and thermal induction (100°C/min) isothermal pyrolysis ................. 82 6- 1 TGA-MS experimental conditions, total compounds were analyzed and observations. ......................................................................................................... 86 6- 2 Compounds targeted in the mass spectroscopic analysis. .................................... 87 7- 1 Experimental conditions and summary of the results during continuous flow pyrolysis of sample #1 (PO). UO represents unreacted organics and Min denotes minerals in the spent shale analysis. ..................................................... 106 7- 2 Significant compounds identified using GCMS in the oil produced at 400°C. . 112 7- 3 TGA analysis of spent shales from the pyrolysis of ¾" cores (First set). .......... 113 7- 4 CHNSO analysis of raw oil shale (OS), spent shale (SS) and shale oil (SO). ... 113 x 7- 5 Summary of the nonisothermal pyrolysis of 1" core oil shale samples. ............ 122 7- 6 Experimental conditions and results from the pyrolysis of 2.5" core samples. .............................................................................................................. 128 7- 7 Overall mass balance of the pyrolysis process at two scales, ¾" core and 2.5" core. The experiments were performed under isothermal conditions for 24 hrs. ................................................................................................................. 134 8- 1 Analytical results for total organic carbon (TOC) and oil and grease (OnG). ... 145 8- 2 Volatile hydrocarbon compounds targeted using GC-MS. ................................ 146 8- 3 Semivolatile hydrocarbon compounds targeted using GC-MS. ......................... 147 9- 1 TGA analysis (weight loss) of Skyline 16 (GR) samples. ................................. 148 9- 2 Elemental analysis (CHNS) of Skyline 16 (GR) samples. ................................. 149 10- 1 Elements and molecular weight data used in constructing the multistep step reaction mechanism. ........................................................................................... 162 A- 1 List of the experiments performed with TGA in different environments. ......... 181 A- 2 The TGA onset points (weight loss and temperatures) for organic decomposition of oil shale in three different environments (N2, Air, and CO2). ............................................................................................. 182 B- 1 Isothermal TGA data for N2 environment (pyrolysis) and data analysis using the integral method. .................................................................................. 188 B- 2 Isothermal TGA data for air environment (combustion) and data analysis using the integral method. .................................................................................. 189 B- 3 Analysis of the nonisothermal TGA pyrolysis data using the differential method. ............................................................................................................... 189 B- 4 Nonisothermal TGA data for air environment (combustion). ............................ 189 B- 5 Kinetic parameters for nonisothermal combustion data for single step and two step (first peak and second peak) mechanisms using the differential method. ............................................................................................................... 191 B- 6 Kinetic parameters using the integral method. ................................................... 192 B- 7 Kinetic parameters - distribution of activation energies as a function of conversion obtained using the Friedman approach. ........................................... 193 B- 8 Kinetic parameters using maximum rate method. .............................................. 194 xi C- 1 Summary of HPTGA (ambient and high pressure) pyrolysis of sample #1 (PO) and sample #2 (CO). .................................................................................. 197 C- 2 Summary of the high pressure TGA experiments performed with sample #1 oil shale at BYU. ................................................................................................ 197 C- 3 Summary of the batch pyrolysis of sample #1 (PO) samples and TGA analysis of spent shales. ..................................................................................... 198 C- 4 Summary of the pressurized (500 psi) batch pyrolysis of sample #1 (PO) samples and TGA analysis of spent shales. ....................................................... 198 C- 5 Summary of the semibatch pyrolysis of sample #1 (PO) samples. .................... 199 C- 6 Summary of the isothermal pyrolysis of ¾" core (sample #2) experiments under ambient pressure. Temperature of the center of the core was used as controlling probe to supply the heat. .................................................................. 200 C- 7 Summary of the experimental conditions and results of ambient and pressure pyrolysis of ¾" core (sample #2) samples. ........................................................ 200 C- 8 Summry of the batch pyrolysis of ¾" core oil shale. ........................................ 201 C- 9 Summry of the hydoys batch pyrolysis of ¾" core oil shale. ........................... 201 C- 10 Summary of the GR core samples pyrolysis. ..................................................... 202 C- 11 TGA analyses of isolated kerogen pyrolysis at three heating rates followed by combustion. ................................................................................................... 202 E- 1 Physical properties of the shale oils. .................................................................. 209 LIST OF FIGURES Figure Page 2- 1 The simplest mechanism of oil shale pyrolysis. ................................................... 14 3- 1 Schematic of the experimental setup to study the effect of operational parameters on yield and quality of the product distribution................................. 39 3- 2 Images of the experimental setup to study the effect of operational parameters on yield and quality of the product distribution at different size of sample......... 39 3- 3 Schematic of temperature distribution measurements during the pyrolysis of large size (2.5") sample. ....................................................................................... 41 4-1 TGA pyrolysis of sample #1 (PO) at heating rate of 20°C/min. Data are quite reproducible .......................................................................................................... 52 4- 2 Pyrolysis of different sections of core sample (sample #2) at different heating rates in N2 environment. ....................................................................................... 53 4- 3 Pyrolysis of the uniformly mixed powdered of core oil shale (sample #2) at 10°C/min in N2 environment ................................................................................ 54 4- 4 Bulk XRD results of Green River oil shale (sample #1). Y-axis displays X-ray counts, and the X-axis degrees 2 theta. Figure shows, from top to bottom, observed (gray) and calculated (dots) bulk XRD patterns, the difference pattern (black). The peak location for each mineral is omitted from the graph for visual clarity. ........................................................................................ 55 4- 5 Bulk XRD results of Green River oil shale (sample #2). The y-axis displays X-ray counts, and the x-axis degrees 2 theta. Figure shows, from top to bottom, observed (blue) and calculated (red) bulk XRD patterns, the difference pattern (grey), and peak locations for each mineral (color coded by mineral, see legend/results at upper right). ............................................................................... 56 4- 6 Schematic of the different stage TGA analyses to estimate the organic and coke in the spent shale. The data show the TGA analyses performed with sample #1 (PO) and intermediate sampling was conducted to perform elemental analyses. ............................................................................................... 58 xiii 4- 7 Schematic diagram of high pressure TGA pyrolysis. Purge and balance gases were passed from the bottom and a back pressure regulator was used to maintain the high pressure environment in the furnace chamber......................... 59 4- 8 Weight loss profiles at ambient and high pressure (500 psi) during HPTGA pyrolysis of sample #1 (PO) and crushed sample #2 (CO). ................................. 59 5- 1 Nonisothermal TGA pyrolysis thermograms: rates go from 0.5°C/min to 50°C/min. The solid lines are weight curves and the dashed lines are derivatives. The arrow indicates that the rates increase as we go from bottom to top. In the derivative curves, the highest peaks for the highest rate used. The second set of derivative peaks is due to mineral decomposition. ................. 62 5- 2 Distribution of activation energies for pyrolysis of Green River oil shale (sample #1) calculated using the advanced isoconversional method. The uncertainties in activation energy values are shown for different number of heating rates considered and for different combinations. As all of the heating rates are used, uncertainties are reduced over the entire conversion range (d). ... 68 5- 3 Distribution of kinetic parameters with extent of conversion [(a) Activation energy (b) A·f(α)] determined using the advanced isoconversional method. All of the seven rates were used in calculating the kinetic parameters. Uncertainties in activation energy values are also shown. ................................... 69 5- 4 Comparison of kinetic parameters from advanced isoconversional and the Friedman method. The kinetic model is assumed to be first order for this comparison. .......................................................................................................... 70 5- 5 Constable plots for Friedman and advanced isoconversional kinetic parameters. ........................................................................................................... 71 5- 6 Experimental and simulated conversion profiles at different heating rates using the advanced isoconversional method. MATLAB based computational method described in the text was used. ................................................................ 72 5- 7 Simulated conversion profiles at extrapolated constant heating rates using two different initial temperatures. Continuous lines show profiles with T0 = 100°C and dotted lines depict extrapolation with T0 calculated from Equation 5.8). ....................................................................................................... 73 5- 8 Distribution of activation energies from discrete reactivity models (Case 1-3 as described in the text). ...................................................................... 75 5- 9 Comparison of different kinetic models at 10°C/min [panel (a) conversion and panel (b) reaction rate]. ................................................................................. 76 xiv 5- 10 Comparison of different kinetic models based on sum of root mean square (RMS) residues. In all these calculation, 100 experimental data points were used. RMS is summed over all of the seven experimental heating rates. ............ 77 5- 11 Comparison of different kinetic models at a heating rate of 100°C/min [(a) conversion and (b) reaction rate]. It is seen that under fast pyrolysis conditions, model of choice does have significant impact on predictions. .......... 78 5- 12 Comparison of the conversion profiles from different kinetic models at a heating rate of 0.01°C/min. The rates for insitu operations are usually slower than 0.01°C/min. At these slow rates, also choice of the model used is important in understanding the rate of conversion of oil shale. ........................... 78 5- 13 Comparison of the experimental and simulated conversion profiles under isothermal pyrolysis. ............................................................................................ 81 5- 14 Simulated conversion profiles under true isothermal pyrolysis. .......................... 82 5- 15 Thermograms of sample #1 (PO) and sample #2 (CO) at heating rate of 20°C/min. ............................................................................................................. 83 6- 1 TGA-MS weight loss and derivative curves for the two lower heating rates. ..... 88 6- 2 TGA-MS weight loss and derivative curves for the two higher heating rates. .... 88 6- 3 Evolution signals of different types of compounds at a heating rate of 10°C/min. ............................................................................................................. 89 6- 4 Ion current signals for different compounds of the same carbon number. ........... 90 6- 5 Concentration indices of different species at 5°C/min as calculated from areas of the peaks. The areas cannot be directly related to true concentrations in a mass spectrometer. ........................................................................................ 91 6- 6 Concentrations of different species at 10°C/min. ................................................ 92 6- 7 The ratio of relative areas of ion current response for different products under different heating rates. .......................................................................................... 93 6- 8 Distribution of activation energy of overall organic weight loss with conversion determined using the TGA-MS data. ................................................. 95 6- 9 Formation of naphtha, (a) weight loss curves of oil shale leading to the formation of the naphtha fraction and (b) distribution of activation energy for the formation of naphtha. ..................................................................................... 96 xv 6- 10 Formation of benzene, (a) weight loss curves of oil shale leading to the formation of the benzene and (b) distribution of activation energy for the formation of benzene. ........................................................................................... 97 6- 11 Formation of aliphatic-C8, (a) weight loss curves of oil shale leading to the formation of the aliphatic-C8 and (b) distribution of activation energy for the formation of aliphatic-C8. ............................................................................... 97 7- 1 Batch pyrolysis of sample #1, (a) weight loss and (b) unreacted organics during the process. 500°C data for 6 hrs is actually for 30 mins. ........................ 99 7- 2 Results from the batch pyrolysis of the sample #1 (PO) under initial pressure of 500 psi. ............................................................................................ 100 7- 3 Comparison of the ambient and pressurized batch pyrolysis of sample #1. ...... 101 7- 4 Semibatch pyrolysis of sample #1 at different temperatures and durations, (a) weight loss, (b) oil yield, (c) unreacted organics and (d) amount of coke formed during the process. ................................................................................. 103 7- 5 Oil to coke ratio (weight %) during the semibatch pyrolysis of sample #1. ...... 105 7- 6 The oil yield at different temperatures during the continious flow pyrolysis of sample #1 (PO) at heating rate of 10°C/min. ................................................. 107 7- 7 The weight loss percent and oil yield from the isothermal pyrolysis of ¾" core samples. Second set is repeated experiments under the same conditions and denoted as Temperature _R. ........................................................................ 108 7- 8 Comparison of the chromatographs for produced oil from pyrolysis of ¾" core samples at isothermal temperatures. ........................................................... 109 7- 9 Normal alkanes and non normal alkanes distribution the oil samples. The y axis is weight percent and the x axis is carbon number. .................................... 110 7- 10 Percent of the total n-alkane, non n-alkane and residue in shale oil samples. The second set is the repeated experiments and denoted by _R. ....................... 110 7- 11 Schematic of the experimental setup for ¾" core pyrolysis. .............................. 114 7- 12 Effect of temperature and pressure: (a) weight loss, (b) oil yield, (c) unreacted organics and (d) amount of coke formed during isothermal pyrolysis of ¾" core. .......................................................................................... 115 7- 13 Effect of temperature and pressure on weight loss, oil yield, unreacted organics and formation of coke under nonisothermal conditions. ..................... 116 xvi 7- 14 Effect of temperature, heating rate and pressure on distribution of organic matter in oil yield and coke. The calculation is based on weight loss. .............. 117 7- 15 The ratio of oil to coke during core pyrolysis (a) isothermal and (b) nonisothermal conditions. The y axis is ratio of oil to coke and the x axis is sample ID. .......................................................................................................... 117 7- 16 TGA analysis of the spent shale from the pyrolysis of ¾" core under isothermal temperatures, 300°C, 400°C and 500°C, and 500 psi pressure. ....... 118 7- 17 Chromatograms of the oil produced at pressure of 500 psi during isothermal at 500°C (Blue) and nonisothermal at 1°C/min experiments. ............................ 120 7- 18 Single carbon number distribution of the shale oils produced under different conditions. .......................................................................................................... 121 7- 19 The representation of SCN distribution in oil fractions. It is assumed that 100 % oil eluted from GC (pseudo SIMDIS analysis). ...................................... 121 7- 20 Ratio of the amount of condensable and noncondensable gases evolved at different experimental conditions. ..................................................................... 122 7- 21 The yield of the oil produced at different temperatures during the pyrolysis of 1" core (sample# 2) at 1°C/min. The data after 500°C point are for isothermal hold time (2 hrs). .............................................................................. 123 7- 22 Grade of the oil samples collected during the pyrolysis of 1" core (sample #2) at heating rate of 1°C/min. ............................................................. 125 7- 23 Grade of the oil samples collected during the pyrolysis of 1" core (sample #2) at heating rate of 5°C/min. ............................................................. 125 7- 24 Grade of the oil samples collected during the pyrolysis of 1" core (sample #2) at heating rate of 10°C/min. ........................................................... 126 7- 25 The distribution of gaseous hydrocarbons in the samples collected at different temperatures during the experiment of 1" core at heating rate of 5°C/min. The chromatograms for 500°C_2hrs is for the sample at the end of the experiment. ............................................................................................... 127 7- 26 The amount of the oil (yield) produced at different times during the pyrolysis of 2.5" core at 350°C and 500 psi....................................................... 129 7- 27 The amount of the oil (yield) produced at different times during the pyrolysis of 2.5" core at 500°C and ambient pressure. ...................................... 130 7- 28 Classification of the oil samples into oil grades. ................................................ 131 xvii 7- 29 The distribution of the hydrocarbon gases produced at different times during the pyrolysis of 2.5" core at 500°C and ambient pressure. ..................... 131 7- 30 Single carbon number distribution of the chromatograms obtained for oils of two different scales pyrolysis. The x axis is carbon number and the y axis is weight percent of SCN. ........................................................................... 135 7- 31 Images of the spent shale from the pyrolysis of two different scales under same condition ................................................................................................... 135 8- 1 Effect of water soaking on TGA onset points and comparison of water soaked (5 months) pyrolysis with anhydrous pyrolysis at two heating rates, 5°C/min and 10°C/min. ...................................................................................... 138 8- 2 Flame ionization detector chromatogram of a product from hydrous (142 days water soaked) pyrolysis at 400°C for 24 hrs. .................................... 140 8- 3 Comparison of expanded chromatograms of products from water soaked (142 days) and nonhydrous pyrolysis at 400°C for 24 hrs. ................................ 141 8- 4 Total ion spectra of the liquid products using GCMS. (a) 10 days water soaked sample pyrolyzed at 450°C. (b) 142 days water soaked sample pyrolyzed at 400°C. (c) Ordinary pyrolysis at 400°C. ....................................... 142 8- 5 Weight loss, unreacted organic and coke percent from the pyrolysis of ¾" core samples. ...................................................................................................... 142 8- 6 FID chromatograms of the gaseous products produced from hydrous pyrolysis. ............................................................................................................ 144 9- 1 GR core sections subjected to isothermal pyrolysis under different temperatures. ...................................................................................................... 150 9- 2 The percent of weight loss, oil yield and gas loss during isothermal pyrolysis of GR core sections. Y axis represents the data in weight percent. ................... 151 9- 3 The weight percent of unreacted organic and coke in the spent shales from isothermal pyrolysis of GR core sections. Y axis represents the data in weight percent. ................................................................................................... 151 9- 4 Images of the spent shales from the pyrolysis of GR core samples. .................. 152 9- 5 Gas chromatograms of the oil produced at 500°C from GR-1, GR-2 and GR-3 oil shales. .................................................................................................. 153 9- 6 Oil fractions based on single carbon distribution of the shale oils produced from GR samples at 500°C. ............................................................................... 154 xviii 9- 7 Effect of the pyrolysis (425°C) on GR-1 sample. .............................................. 155 9- 8 Effect of the pyrolysis (500°C) on GR-1 sample. .............................................. 155 9- 9 Comparison of the organic matter decomposition onset points during the pyrolysis (10°C/min in N2 environment) of isolated kerogen (extracted) and original raw oil shale from the same source (GR-1). ......................................... 156 10- 1 Schematic of the model design to simulate the coupled multiphysics involved in the thermal treatment of oil shale. .................................................................. 158 10- 2 Schematic of experimental approach and identical simulation environment. The variation is in the r direction only. .............................................................. 159 10- 3 Kerogen decomposition (single particle) and product formation profiles using single step mechanism under (a) isothermal (400°C) and (b) nonisothermal (10°C/min). ................................................................................. 165 10- 4 Kerogen decomsposition (single particle) and product formation profiles using two step mechanism under (a) isothermal (400°C) and (b) nonisothermal (10°C/min). ................................................................................. 165 10- 5 Single particle (TGA scheme in batch mode) of kerogen decomposes to different products using multiple step reactions mechanism under (a) isothermal (400°C) and (b) nonisothermal (10°C/min) pyrolysis. The small window shows the material profiles at long time scale (a log scale). ................ 166 10- 6 Schematic of the application of the heat to the source material via surface heating and center heating. ................................................................................. 167 10- 7 Isothermal (400°C) surface heating, (a) distribution of temperature and (b) rate of heavy oil formation in different sections of the core. ............................. 168 10- 8 Effect of convection on product formation rates. ............................................... 169 10- 9 Average total flux of the fluid products from the surface of the core during (a) surface heating and (b) center heating schemes. .......................................... 170 A- 1 Pyrolysis (N2) of powdered oil shale with different particle size ranges from minus 70 mesh to plus 200 mesh. ...................................................................... 180 A- 2 Pyrolysis (N2) of powdered oil shale with different flow rates of nitrogen. ...... 180 A- 3 The TGA curves for organic decomposition of oil shale in three different environments (N2, Air, and CO2) and at two different heating rates, 5°C/min and 20°C/min. .................................................................................................... 182 xix A- 4 Comparison of the pyrolysis of sample #1 (PO) and sample #2 (CO) at three heating rates. ...................................................................................................... 183 A- 5 Pyrolysis of GR kerogens at heating rates of 5°C/min, 10°C/min and 20°C/min. (a) GR-1 kerogen, (b) GR-2 Kerogen and (c) GR-3 kerogen. Pyrolysis was followed by combustion at 10°C/min. ........................................ 184 B- 1 Isothermal TGA curves in the N2 environment (pyrolysis). .............................. 186 B- 2 Isothermal TGA curves in air environment (combustion). ................................ 187 B- 3 Nonisothermal TGA combustion. Rates go from 0.5oC/min to 50oC/min. ........ 187 B- 4 Activation energies for the pyrolysis of oil shale using conventional methods. ............................................................................................................. 195 B- 5 Goodness of the fit using (a) the differential method and (b) integral method on pyrolysis data. .................................................................................................... 196 D- 1 Pressure and temperature profiles during the batch pyrolysis of powdered (sample #1) oil shale (Table C-3). ...................................................................... 203 D- 2 Pressure generated at different temperature during the batch pressurized pyrolysis of powdered (sample #1) samples and temperature profiles. S is the rector surface temperature and C is the temperature at the center of the sample (Table C-4). ............................................................................................ 204 D- 3 Temperature profiles for the pyrolysis of ¾" core (sample #2) samples (Table C-7). ........................................................................................................ 205 D- 4 Temperature profiles for the pyrolysis of 1" core (sample #2) at three heating rates (Table 7-5). ................................................................................... 206 D- 5 Temperature profiles during the pyrolysis of 2.5" core (sample #2) samples (Table 7-6). ........................................................................................... 207 D- 6 Pressure generated at different temperature during the batch pyrolysis of 3/4" core oil shale at different temperatures (Table C-8). The x axis is time in min and y axis is pressure in psi. ................................................................... 208 D- 7 Increase in the pressure during batch hydrous pyrolysis experiments at different temperatures. The x axis is time in min and y axis is pressure in psi. . 208 ABBREVIATIONS ASTM American Society for Testing and Materials BPR Back Pressure Regulator BT Batch Pyrolysis CB Combustion (Air Environment) CF Continuous Flow Pyrolysis CHNS Carbon Hydrogen Nitrogen Sulfur -Elemental Analysis CO Core Oil Shale CP Core Powdered CT Computed Tomography FID Flame Ionization Detector FTIR Fourier Transform-Infrared spectroscopy GC Gas Chromatography GC-MS Gas Chromatography- Mass Spectrometry GR Green River Oil Shale from Skyline 16 location ISO Isothermal HP High Pressure Pyrolysis HR Heating Rate HY Hydrous Pyrolysis HO Heavy Oil HPTGA High Pressure Thermal gravimetric Analysis xxi LO Light Oil MW Molecular Weight NISO Non-Isothermal OS Oil shale PO Powdered oil shale PY Pyrolysis (Nitrogen Environment) RMS Root Mean Square SCN Single Carbon Number SG Shale Gas SO Shale Oil SS Spent Shale SB Semi-batch Pyrolysis TCD Thermal Conductivity Detector TGA Thermal Gravimetric Analysis TC Temperature Control TCC Temperature Control from Center of the Sample TCO Total Organic Carbon TGA-DSC Thermal Gravimetric Analysis-Differential Scanning Calorimetry TGA-MS Thermal Gravimetric Analysis- Mass Spectrometry TIC Total Ion Chromatogram WS Water Soaked Sample WAT Wax Appearance Temperature XRD X-Ray Diffraction Analysis NOMENCLATURE A Preexponential (Frequency) Factor [min-1] a'1 Constant [1.1275] Constant [1.149e-4] α Conversion β Heating Rate Constant [3.6667e-7] Constant [-0.01843] Ci Mass/Concentration of Component i cO Concentration of oil [mol/m3] Cp Heat capacity [ J/(kg×K)] DAB Diffusion Coefficient of A in B (10-50 m2/s) Dp Average Pore Diameter [50×10-6 meter] E Activation Energy [kJ/mol] Eα Activation Energy at Conversion α ε Porosity of Oil Shale f(α) Reaction Model ƒ (T) Temperature Dependency of the Reaction Rate Grade_OS Grade of Oil Shale = 30 [gallon/ton] I Integral symbol xxiii k Rate Constant K Thermal Conductivity [W/(m×K)] Kp Permeability [mili darcy] Org Organic content of the material [initially, 0.18 wt% unit less] M Molar Mass N Number of Heating Rates p Pressure Q Heat Source (Heat Absorbed by Reactions) Qm Mass Source R Gas Constant [8.314 kJ/(mol× K)] Rho_org Density of Organic Material [1050 [kg/m3] Rho_rock Density of Rock (other than organic) Material [2700 [kg/m3] ri Reaction Rate of Component i r Radial Coordinate T Temperature [°C or K] T0 Initial Temperature Tmax Temperature when Reaction Rate is Maximum t Time (second (s)/ minute (min)/ hour (hr)) u Velocity Vector μ Viscosity ρ Density ρos Density of Oil Shale [kg/m3] W0 Initial Weight of the Sample Wt Weight of the Sample at time, t xxiv W∞ Weight of the Sample at the End of the Experiment xK Conversion of Kerogen ΔH Heat of Reaction p Pressure Gradient T Temperature Gradient ACKNOWLEDGMENTS I would like to express my sincere thanks and gratitude to Professor Milind D. Deo for his invaluable guidance and support throughout the period of my doctoral work. Working with him provided an enriching experience to my academic endeavor at the University of Utah. His encouragement and support were instrumental in the completion of my dissertation. Sincere thanks are also extended to the members of my supervisory committee, Dr. Eric G. Eddings, Dr. Edward M. Trujillo, Dr. Edward M. Eyring and Dr. Hong Y. Sohn, for their invaluable help during the course of my work through discussions and their input to this dissertation. The funding for this project was made available through U.S. Department of Energy, project number DE-FE0001243. The samples were provided by Utah Geological Survey. I also would like to acknowledge the efforts of my colleagues at the Petroleum Research Center and their contribution to this work. I wish to thank my family members for their love and support throughout this endeavor. Special thanks are due to my parents who have always believed in me and have always provided their encouragement and support for every move in my life. Finally, special thanks are also due to my friends in Salt Lake City, Naveen, Surya, Prashanth, Jake, Madhu and Palash, and my lovely friend Pinki for providing me with a family away from home. 1. INTRODUCTION With the rapid rise in energy requirements, a strong need to search for alternative fuels to furnish future energy demand is quintessential. Alternative fuels can be generated from various sources, such as bioenergy, wind, solar, nuclear, etc. Oil shale and oil sands can contribute significantly to energy requirements by producing unconventional oils through thermal treatment. Oil shale can be exploited as a viable source to produce oil and gas by pyrolysis and electricity by direct combustion. The technologies for oil shale development need to be improved for the process to be economically feasible. Oil shale is a complex heterogeneous material that contains significant quantities of organic matter, with kerogen being the principal component. Kerogen is a complex compound with a high molecular weight. During thermal retorting, kerogen decomposes and releases liquid (shale oil) and gaseous products. This decomposition process requires heat input. The source of heat input might emit greenhouse gases. Hence, pyrolysis of oil shale is questionable due to economic and environmental constraints. The concept of obtaining useful hydrocarbons from oil shale is not new, and extraction has been in practice since the 14th century. The first patent for a shale oil extraction process was granted during the 17th century [1]. Historically, the cost of oil derived from oil shale has been significantly higher than conventional oil. The development of efficient technologies to derive oil from oil shale might reduce its cost [2]. The oil shale industry has gone through a revolution of sorts. After the oil crisis in the 1970s, a great deal of effort was spent on research and development and on pilot scale 2 technologies. Extensive research was conducted both in on-surface and in-situ production methods. Even though some large pilot underground retorting operations were performed, the on-surface (mining and processing) methods were closest to full scale (~10,000 barrels/day) commercial implementation. Oil prices collapsed in the early and mid-1980s, which led to the total discontinuation of oil shale research and development programs. Recently, crude oil prices have again risen to levels that may make shale-based oil production commercially viable. The interest of governments and industries in developing the technologies for oil shale as an alternative to conventional oil may contribute to reduce the cost of production significantly. There has been active research on the production of oil from oil shale since 1913 [3]. Currently, most of the commercial methods in operation or under development are direct heating retorts. In-situ production technologies have seen a significant revival with recent advancements in understanding the inherent technical logistics of the process. This involves a slow thermal pyrolysis of the organic matter in shale which leads to a light oil product that would not require additional thermal upgrading. The variability in composition and geologic setting of worldwide oil shale deposits affects the applicability of various technologies. Water content, minerals, and organic maturity (amount and H/C ratio) vary with source rocks causing different product distribution when subjected to retorting conditions [4]. Despite the application of existing technologies, some key fundamental questions concerning kerogen decomposition, the quality and yield of the generated oil remain unanswered. Improved knowledge of detailed kerogen decomposition mechanisms, kinetic rates, and product compositions are required to efficiently design and optimize the processes. The process of scaling up the laboratory 3 data to field scale for large production by insitu and exsitu means is not yet well established. 1.1. Research Objectives A detailed study of the pyrolysis process at different scales provides data that can generate the information needed for developing kinetic rate models for predicting kerogen decomposition and product composition. Heat and mass transfer resistances affect the rates and product compositions depending on the process configuration. An understanding of the pyrolysis process at different experimental scales aids in efficient formulation of the process at field scale. Development of a kinetic model for these phenomena and the development of a possible mechanistic pathway for the generation of products are required to optimize the effects of operational parameters. The goal of this study is to provide a comprehensive understanding of the kinetics of the oil shale pyrolysis process. This understanding includes the development of a kinetic model to represent the compositional distribution of products obtained from a large pool of experimental conditions. The emphasis of this research is on a bench scale understanding of the tradeoff between simplicity (the macro mechanism of the product formation) and complexity (the detailed micro chemistry) involved in the decomposition process. The principal goal of this research is to evaluate the kinetics and dependency of product composition on the scale and operating conditions. The research in this study is focused on the multiscale thermal pyrolysis of oil shale. Experimental studies conducted were under a wide range of operating conditions. A mathematical model simulating the 4 complex physical and chemical process was developed in a multiphysics simulation suite, COMSOL. The following activities were carried out to achieve this goal:  Thermal treatment of oil shale with thermal gravimetric analysis (TGA) and understand the kinetics.  Use of the best available kinetic models for the complex material decomposition.  Conduct TGA and bench scale experiments on cores of different sizes to understand the conversion of kerogen to oil  Obtain product distribution under different conditions.  Multiscale pyrolysis to address the multiphysics issues involved.  Conduct experiments at high temperature (with different heating rates) and high pressure, emulating insitu conditions.  Develop a comprehensive model which combines, heat and mass transport mechanisms along with reaction kinetics. 1.2. Background Fast depleting conventional oil reserves may be substituted by the vast resources of petroleum generating source rock known as oil shale. There are significant resources of oil shale in the western United States, which if exploited in an environmentally responsible manner, would provide secure access to transportation fuels. Oil shale is a compact sedimentary rock that contains organic matter laminated with a complex mineral matrix. The organic matter undergoes chemical decomposition on thermal heating or retorting to produce volatile matter. The generated volatile products are both lighter gases 5 as well as condensable higher boiling point substances known as shale oil. Shale oil is an oil-like liquid that can be used to produce transportation fuels. Oil shale may contain small amounts of bound and/or unbound water. During the decomposition of organic material in oil shale several coupled processes occur simultaneously and regulate the distribution of the products. The yield and desired quality of the shale oil is controlled by the operational parameters to which the raw oil shale is exposed. The distribution of the products from oil shale retorting depend on the composition of the source material [4-6], the temperature-time history [7, 8], pressure [9-11], residence time (secondary reaction) [12, 13] and presence of other reactants such as water [14-17], methane [18], oxygen [19] carbon dioxide [20] , and a host of other factors. Because of the chemical composition of the oil produced, moderate to significant upgrading (nitrogen removal and/or hydrogen addition) may be required to convert the oil into a refinery feedstock [21-23]. Worldwide recoverable reserves of oil shale have been estimated at about 2.8 to 3.3 trillion barrels of shale oil [24]. The largest known and most studied oil shale deposits are in the Green River Formation, which is spread among the states of Colorado, Utah, and Wyoming [2, 25, 26]. The Green River Formation reserves could yield 1.5 to 1.8 trillion barrels of shale oil. The oil produced from Green River Formation promise a significant domestic oil source [25, 27]. The Mahogany zone in the Green River Formation region is an organically rich deposit (10-15 weight % organic) of type-1 kerogen [28]. The decomposition of kerogen produces more than 15 gallons of oil per ton of oil shale source rock, according to the Fischer Assay method [2, 28, 29]. 6 The knowledge necessary for the commercial implementation of a process to produce oil from oil shale is growing due to extensive research efforts. The thermal treatment of oil shale can be carried out in surface reactors (exsitu mode) in controlled settings or in-situ under prevailing geologic conditions. Mining the source material to the surface and then retorting are the major steps in exsitu (surface) processing, while in-situ processes are performed underground where the source material is originally deposited. Each mode has certain advantages and drawbacks. Controlling the process parameters is more difficult in insitu processes than in exsitu processes. But, on the other hand, it has been reported that the oil produced in an insitu process is better quality and may be used as a direct feedstock for a petroleum refinery. The yield and quality of the products generated vary significantly with differing heating conditions. The time-temperature history to which the organic matter in the shale (kerogen) is subjected to is important in all of these configurations. The configuration in which the reacting materials are placed is also important in establishing the product amounts and compositions. In most reactor (exsitu) or in-situ configurations, the products evolved undergo secondary reactions. The operational parameters determine the yield and the oil quality, which in turn directly impact the economic and environmental aspects of the process. Producing shale oil with desirable characteristics (low heteroatom content and molecular weight, and high hydrogen content) requires an understanding of the decomposition mechanisms and kinetic parameters associated with kerogen decomposition. Kinetic parameters include activation energy E, preexponential factor A, and the reaction model ƒ(α), also known as kinetic triplet, which describe the progress of the reaction. Determining the kinetics of the decomposition and the rates of products formation will help guide process development. 7 Technologies have been proposed for feasible commercial development of the process. Currently, many major oil companies are applying different technologies to develop these processes. For example, Shell has developed their InSitu Conversion Process (ICP) technology (on a pilot scale) [30], ExxonMobil has developed the ElectroFrac process [31], and Chevron has developed the CRUSH process [32]. Other production activities include Redleaf's confined capsule retorting, AMSO's CCRTM in-situ process, and the retorting of targeted organic matter by radio frequency heating. 1.3. Significance of the Research and Original Contribution Extensive research has been carried out on the recovery of oil from oil shale by different means over the last eighty years. However, certain issues, in particular concerning decomposition mechanisms and associated kinetics, remain inconclusive, either due to contrary findings, or due to limitations with the data. Studying the compositional and material characteristics of each phase generated in the process, would help develop a better understanding of this complex reaction set. The framework for creating distribution of activation energy based kinetic models exists in the literature. The generalized methodology for scaling up data from the laboratory to industrial or field scales has not been reported in published literature. The purpose of this research is to generate oil shale specific kinetics using the distribution of activation energy methodology, understand the compositional aspects and create generalized scale up procedures. The research needed for both surface and subsurface processing were reported in this work. A study was conducted to address the issues of oil production by pyrolyzing the oil shale in the laboratory. Detailed kinetics were examined. Apart from grain-scale samples used in TGA, the cores of different 8 diameters were studied to understand scale up effects. Experiments were conducted at pressures close to the in-situ processes. The detailed compositional analyses of the products were performed. A multiphysics model for the formation of the product component was established. The reaction network was constrained based on material and elemental balances. This work provides a comprehensive laboratory data set to improve existing compositional simulators. This study would also resolve the existing ambiguity on the physics of this process and also would significantly improve the accuracy of existing compositional simulators by providing a comprehensive kinetic data set. The outcome of this research advances the understanding of reaction mechanisms, product evolution rates, and the kinetics of the pyrolysis products generated from complex material, kerogen in oil shale. 1.4. Thesis Outline Chapter 2 contains a comprehensive literature review on oil shale pyrolysis, kinetic studies and compositional analysis, and then a review of modeling efforts. Chapter 3 outlines the experimental setup, analysis and the characterization protocols for the reactants and the products. This section also summarizes the experimental procedures. The characterization of the raw material is summarized in Chapter 4. Chapter 5 discusses the results of the detailed thermal gravimetric analysis (TGA) kinetic studies of organic decomposition. The compositional analysis of the evolved products and their kinetics using thermal gravimetric analysis-mass spectrometry (TGA-MS) are discussed in Chapter 6. The results of mutiscale pyrolysis of oil shale pyrolysis under a wide range of operational parameters and experimental configurations are summarized in Chapter 7. 9 The studies of hydrous treatment of oil shale pyrolysis and the heterogeneity in the raw samples are included in Chapter 8 and Chapter 9, respectively. The results of a generalized mathematical model simulating this complex multiphysics process are summarized in Chapter 10. Chapter 11 contains a comprehensive summary of study and recommendations for future work. 2. LITERATURE REVIEW The extent of the literature on oil shale retorting is comprehensive and covers various approaches for the production of shale oil including compositional analysis of materials (raw shale, products formed and spent shale), development of mechanisms and kinetic parameters as well as the effects of retorting conditions on the product distribution. However, due to the very complex nature of the organic matter in oil shale, unraveling the kinetics has not been straightforward. An accurate kinetic model that is able to adequately represent the mechanism of kerogen conversion to generated products is necessary. 2.1. Oil Shale Pyrolysis Process Oil shale is a wide variety of compact, laminated, complex and heterogeneous sedimentary rock material that contains organic matter, mineral matrix and small amount of bound and/or unbound water [33]. The main constituent of the organic part of the shale is kerogen which, in some publications is approximated as C200H300SN5O11 [34]. Pure kerogen is not considered to be a chemical compound of fixed composition and properties. It is a heterogeneous mixture of organic matter derived from materials such as spore exines, algae, resins, cuticles and woody fragments [33]. Rich oil shale contains about 10 weight percent kerogen. The kerogen portion of the organic matter is insoluble in ordinary solvents. Oil shale also contains a small percentage of bitumen which is a benzene-soluble organic material naturally present in the oil shale. This soluble material 11 (natural bitumen) normally amounts to only 8 to 10% by weight of the total organic matter present [35]. The common understanding is that kerogen, which is a cross linked high molecular weight solid, breaks down and undergoes chemical decomposition into products when subjected to thermal heating or retorting. Producing oil from oil shale requires heating out of contact with air in a process called pyrolysis. Pyrolysis, which is carried out in an inert atmosphere, is likely to exhibit different characteristics than combustion, which is carried out in the presence of air. Oil shale pyrolysis is analogous to what happens on a geological time scale to produce conventional oil. The production of oil from oil shale is considered unconventional because the material is being artificially and thermally treated at a much faster rate. Upon supplying the energy (heat) to the source rock, the decomposition rate of the organic portion in the shale is accelerated and produces volatile materials. This volatile material ranges from light organic and inorganic gases to very heavy liquid including bitumen. The condensation of the evolved products yields shale oil. Because of hydrogen deficiency, a significant portion of kerogen is converted to char/coke, a carbonaceous residue. Carbonaceous residue is a benzene insoluble portion of the kerogen that remains in the spent shale [36]. The potential products evolve when kerogen reaches a definitive temperature. This reaction continues to completion with appropriate temperature and/or time. The necessary temperatures for oil shale retorting mentioned in the literature are 300°C- 550°C for laboratory conditions [33, 37]. The temperature can be lower if the duration of the experiment is long, or on the contrary to reduce the time required, the temperature can be increased. The compositional form of kerogen in shale is such a complicated 12 heterogeneous mixture of organic compounds that the sequence of several reactions that take place to produce numerous chemical compounds are mostly unknown [27]. Some investigations have led to the conclusion that the kerogen exhibits properties of pyro-bitumen and, upon heating, decomposes by a consecutive reaction into bitumen. The bitumen does not vaporize but remains in the shale [33] and may behave as a solvent for the remaining organic matter [35]. Upon subsequent heating, this bitumen decomposes or cracks to oil, gas, and a carbonaceous residue [38, 39]. Few studies were also reported on the extraction of the soluble bitumen [3] and insoluble kerogen [40] from oil shale and their pyrolysis processes. Frank and Goodier [40] reported that the primary products from the extracted kerogen in the temperature range of 300°C to 350°C were formed without producing any oil. At higher temperatures, the decomposition was much faster and said to resemble that of a cracking process. Hubbard and Robinson [33] studied Colorado (Parachute and Rifle) oil shale samples with different amounts of organic material, at different temperatures (350o-525oC) and atmospheric pressure in the absence of oxygen. The samples were extracted (removal of naturally present bitumen) and only insoluble organic material in the oil shale was studied. They found that the soluble organic material (bitumen) in the raw oil shale has no appreciable effect upon the rate of thermal decomposition of kerogen. Extracted kerogens from oil shale of different sources follow comparatively the same reaction rate at corresponding temperatures. Allred [35] reinterpreted the Hubbard and Robinson data and concluded stating that the bitumen has a catalytic or solvent action on kerogen decomposition. 13 2.2. Mechanism of Oil Shale Pyrolysis and Product Formation The definitive knowledge of the chemical structure of kerogen is not known. It is assumed that kerogen is largely a material of high molecular weight consisting mainly of a loosely interconnected structure of partly unsaturated chains and rings. The rupture of cross-linkage of these interconnected structures occurs first and then true thermal decomposition follows [41]. The complexity of the decomposition during the oil shale pyrolysis was hypothesized based on experimental observations and measurements, such as bitumen formation as an intermediate and subsequent reactions [33]. Analysis of the compositions of the products is important for understanding the competitive reaction mechanisms. There are several reactions that occur during oil shale pyrolysis. Table 2-1 summarizes a list of the reaction networks that may represent the overall decomposition process of oil shale [42]. Rajeshwar et al. [43] listed various mechanisms proposed for oil shale retorting in the literature. The most common pyrolysis decomposition mechanism can be explained in two steps: primary pyrolysis, followed by secondary pyrolysis as shown in Figure 2-1 [27]. All these reactions progress with competitive reaction mechanisms and with different rates that depend on the conditions of pyrolysis process. The gas products include very light hydrocarbons and inorganic gases, CO2 and H2, while the oil is a mixture of condensable hydrocarbons (heavy and light oils) in vapor-liquid equilibrium. The fraction of oil in vapor and liquid phases depends on the boiling point distribution of the mixture components and pyrolysis temperature and pressure [27]. The water may also be generated from other sources such as free water and bound water from organic and mineral decomposition. The rates of competitive reactions depend primarily on the time-temperature history and on other process parameters that 14 Table 2- 1: Reaction network (organic, water and mineral reactions) during the pyrolysis of oil shale. Figure 2- 1: The simplest mechanism of oil shale pyrolysis. are responsible for the secondary reactions. Secondary pyrolysis refers to the decomposition of the primary products due to coking (liquid phase oil to coke), cracking (vapor phase oil to light gases), and further decomposition of the char and carbon residue to gas. Oil coking takes place when the generated oil has a long residence time. The presence of the significant aromatic components in the oil makes it hydrogen deficient and susceptible to coking [13]. Burnham and Happe [13] hypothesized that the carbon residue may also form from a material that loses minor fragments but retains its basic three dimensional structure during pyrolysis. Burnham and Singleton [9] reported that Organic phase reaction Reactant Products Primary Pyrolysis Kerogen Oil(l) + Gas (v) + H2 (v) +CH4(v) + CO2(v) + H2O (v) + Char(s) Secondary Pyrolysis Char H2 (v) + CH4(v) + ROC (s) +ROH(s) Carbon Gasification ROC(s) +CO2(v) CO(v) Oil degradation Oil (l) H2(v) + CH4(v) ROC(s) +Coke (s) Oil Distillation/Condensation Oil (l) Oil(v) Water-gas Shift CO(v) + H2O (v) CO2(v)+ H2(v) Bound water loss H2O(s) H2O(v) Mineral reactions Dolomite decomposition MgCa(CO3)2(s) CaCO3 (s) + MgO(s) + CO2 (v) Calcite decomposition CaCO3(s) +SiO2(s) Ca2SiO4(s) + CaO(s) + CO2(v) Organic matter Oil l,g + Char + Gas + H2O Coke Gas Oil Gas Carbonaceous residue 15 enough hydrogen is available from coke formation to saturate the products formed by cracking of the large normal and cyclic hydrocarbons. Fausett and Mikinis [44] have proposed a mechanism in which kerogen pyrolysis can be considered simply as a conversion of most of the aliphatic carbon to oil, while most of the aromatic carbon is converted directly to a carbon residue. Although these workers acknowledged that other reactions such as conversion of aromatic carbon to oil and coking of oil to carbon residue may also occur. There are a few more complex reaction mechanisms reported in the literature. These address the effect of the mineral matrix and its inorganic products formed on organic matter decomposition mechanisms [45-47], diffusion controlled kinetics [48] and free radical mechanisms [49, 50]. Galan and Smith [48] determined the influence of transport effects (heat and mass) on the observed rate of thermal decomposition of kerogen of Colorado shale (Anvil point mine) in a TGA type apparatus. They concluded that if the particle size was greater than about 0.4 x10-3 m and if there are more than two to three layers of particles, the transport of heat and mass through intra-particle, particle to bulk fluid, and interparticle, influenced the rate of decomposition. Charlesworth [49] proposed a more complex temperature dependent diffusion mechanisms which follows the following steps; 1-Diffusion controlled reactions, 2- Phase boundary controlled processes, 3- Nucleation controlled processes, 4- Reaction with nucleation and linear growth of nuclei, and 5- Processes governed by nucleation and bulk growth of nuclei which may occur during pyrolysis. 16 2.3. Complexity Involved in the Process The parental source rock is complex and impermeable. During thermal treatment products are formed. Voids and fissures are generated as the converted kerogen moves out of its original site due to thermal expansion and volatility. This provides an interconnecting network and an internal porosity and permeability in the shale [18]. The coke formed may fuse the porous network. Galan and Smith [48] reported the influence of heat and mass transports. There is a possibility of intraparticle diffusion limiting the generation rate, and the rate controlling step may change as the decomposition progresses. These rate-control transport phenomena also favor the residence time conditions for secondary reactions. Depending on the processing condition, the oil produced may be degraded into less desirable products: coke and gas [51]. The heterogeneity of reactant molecules may produce different amounts of desired products generated from different segments, which influence the reactivity distributed around the complex mechanism. During the pyrolysis of large particles/blocks of oil shale, several coupled physical and chemical phenomena occur simultaneously, such as heat transfer, chemical reaction kinetics, multiphase flow, phase changes, and mineral alteration and interaction. These processes are highly coupled and interrelated. The changes in the physical properties (density, heat capacity, permeability, porosity, etc.) due to the local thermodynamic conditions may also alter the product distribution. Isolating each phenomenon accurately is impractical. For example, the chemical reaction kinetics of oil shale pyrolysis are quite complex. Several hundred products are formed during decomposition. The distribution of these products (vapor or liquid) and their formation 17 rates depend on the local conditions. Attempts to address some of these issues during experimental and modeling investigation of Colorado and other oil shales' retorting were reported in the literature [37, 42, 52]. 2.4. Kinetic Analysis of Organic Decomposition Reliable kinetic data are essential for the accurate mathematical modeling of various on-surface and in-situ oil shale processes. The rate of the individual reaction in a complex reaction network is different at different temperature profiles (heating rates) because of time and temperature history the material is exposed to. The appropriate mechanism for representing the decomposition kinetics is uncertain. The simplest representation is a global reaction mechanism. However, oil shales have different origins and geological environments resulting in different compositions. They may behave differently when subjected to pyrolysis conditions, and consequently the proposed mechanisms and derived kinetics vary. Analysis of the oil shale pyrolysis has appeared in the literature; Colorado oil shale (Green River Formation) [48, 53, 54], Spanish oil shale (Puetrollano) [6], Chinese oil shales [55-57], Pakistani oil shale [58], Jordanian oil shale [20], Moroccan oil shale [59], etc. Elemental analysis and pyrolysis kinetics of oil shales from all over the world were summarized by Nuttal et al. [4] who observed that there were considerable variations in the kinetic parameters of the different shales. A number of researchers have derived relatively simple but effective kinetic expressions for oil evolution during the pyrolysis of Green River and other oil shales based on first-order reaction [60, 61], consecutive first-order reactions [33], parallel first-order reactions [62], and logistic or autocatalytic mechanisms [35]. Campbell et al. [61] postulated a first-order 18 decomposition mechanism for the pyrolysis of Colorado oil shale and reported an activation energy of 214.4 kJ/mol and a frequency factor of 2.8E13 s-1. Leavitt et al. [62] proposed two parallel first-order lumped reactions and, obtained activation energies of 191.02 kJ/mol for temperature above 350°C and 87 kJ/mol for temperature below 350°C. A controversial two-step mechanism has also been proposed by Braun and Rothman [36]. The kinetic analysis round table [63-67] convened to study the kinetics of reactions involving complex solid materials concluded that it was inappropriate to use a single heating rate and a prescribed kinetic model to derive kinetic parameters. The basic flaw in methods which followed this procedure was that they resulted in activation energies that were heating rate dependent. By using a variety of computational methods, the panel observed that isoconversion and multi heating methods were particularly useful in describing kinetics of complex material reactions [63]. Burnham and Braun [68] reviewed various kinetic analysis approaches for obtaining kinetic parameters for reactions involving complex materials. They argued for the use of well chosen models that are able to fit the data and extrapolate beyond the time-temperature range of the data. For complex materials such as kerogen, generalized distributed reactivity models were found to be suitable. When studying the oil shale pyrolysis data, Burnham and Braun [68] used modified Friedman and the modified Coats and Redfern methods while also employing the discrete activation energy model. Burnhan and Dihn [69] also compared the isoconversional methods to models obtained using nonlinear parameter estimation. They concluded that reactivity distribution of parallel reactions involving complex materials can be modeled effectively using either the isoconversional methods or 19 parameter fitting approaches; however, they observed that the isoconversional methods are fundamentally inappropriate for use in modeling competing reactions. It is argued [70] that the variation in activation energy for the decomposition of a complex material is caused by the fact that the overall rate measured by thermal analysis is a combination of the rates of several parallel reactions, each of which has its own energy barrier, and hence an activation energy. The effective activation energy derived from these global rate measurements becomes a function of the individual activation energies. Burnham [14, 71] has argued convincingly by using multiple sets of data that this two step decomposition mechanism is not appropriate for oil shale pyrolysis. More complex kinetic analysis procedures have also been used in deriving kinetics of decomposition of oil shales [5, 72-74]. It has also been reported that kinetics parameters obtained using one apparatus do not agree well with those derived using a different system. Burnham [71] notes that these differences are primarily due to the use of poor kinetic analysis methods. Most of these studies recommended the use of distributed reactivity or similar methods, where the reaction rate is inherently independent of heating rates. Variations in the application of these concepts exist in the literature [69, 75-77], particularly in the manner in which the equations are solved. One the first applications of the isoconversion method, based on the differential form of the rate equation [78] is the Friedman method. Modifications and applications to different complex materials have been reported [68, 75, 79]. A general application of this concept is the postulation of a model-free isoconversional method [80], where a functional form of the reaction model is not 20 presupposed. Extensions of this basic theory in the form of advanced isoconversional method have been applied to a number of complex solid materials [79, 81, 82]. A comprehensive suite of kinetic analysis models based on the concepts discussed by Burnham and Braun [68] is available for use (Kinetic05). 2.4.1. Isothermal and Nonisothermal Kinetic Studies A kinetic model should be coherent under isothermal and nonisothermal conditions. The overall mechanism of decomposition is independent of the temperature and reaction progress. Kinetics should not depend on the methods used for its derivation. Hence, nonisothermal kinetics is obliged to give the same results as isothermal kinetics. However, comparison of isothermal and nonisothermal data can be tainted by some uncontrolled experimental factor according to the Parametric Sensitivity of Thermal Analysis (PSTA) principle [66]. Thakur and Nuttal [59] reported that at lower temperatures, rates of isothermal decomposition are equivalent to those obtained under nonisothermal conditions with high heating rates (>50OC/min). In high temperature isothermal experiments, the thermal induction period is sufficient to decompose a significant amount. Braun and Rothman [36] recognized this fact and reanalyzed the results of Hubbard and Robinson [33] by making corrections to account for the thermal induction period. Other researchers [34, 48] also determined the intrinsic kinetics of Colorado oil pyrolysis by incorporating the induction period. Campbell et al. [27] performed combined kinetic analysis of isothermal and nonisothermal TGA measurements on oil shale data. 21 2.5. Compositional Analysis of Pyrolysis Products There has been some published work on the compositional information of the products of oil shale pyrolysis. Campbell et al. [27] deduced mechanisms of the formation of different products, oil and gas, but did not focus on the detailed chemistry of the formation of different components. Most of the studies focused on the compositional analysis of the bulk products collected during or after the completion of the experiment at different conditions [5, 7, 14, 27]. Analysis of products as they are formed using online techniques provides additional information about mechanisms of product formation. Compositional measurements of products have been performed using both online gas chromatography (GC) and online gas chromatography combined with mass spectrometry (GC-MS). Burnham and Ward [50] analyzed noncondensable gases evolved during pyrolysis using the online flame ionization detector (FID) (C2 and C3 hydrocarbons) and thermal conductivity detector (H2, N2 and CO). They proposed a free radical mechanism to study the alkene/alkane evolution. Chalesworth [8, 49] studied the pyrolysis of two Australian oil shales and monitored the products using an online GC-FID. Alkene to alkane ratios and kinetic parameters for selected organic compounds were reported. Espitalie et al. [83] studied the kinetics of hydrocarbon evolution produced from the pyrolysis of type II and III kerogens using online GC-FID, and grouped them into C1, C2-C5, C6-C15, C15+ classes. They concluded that the Tmax (temperature at which the rate of product evolution is highest) values for each class of compounds increased as the molecular weight of the class decreased. Programmed pyrolysis-gas chromatography of artificially matured Green River kerogen was also reported [84]. 22 The use of mass spectrometry (MS) to identify compounds from the pyrolysis of oil shale is not new. Both offline and online analyses have been used. It was shown that a complex molecule like porphyrin survives retorting temperatures, but attached alkyl and other compounds break off and evolve separately [85]. Shale oil derived from a novel perchloroethylene extraction scheme was analyzed by a number of analytical methods, including tandem mass spectrometry [86]. The principal components found in the extracted oil from Indiana oil shale (Devonian member) were hydrogen rich paraffins and cycloparaffins, having a carbon number range extending to approximately C35+. The benzene concentration in the extracted oil was reported to be 3.94 volume percent. Lee [87] summarized detailed compositional analyses of produced oils from seven different oil shale sources and identified approximately 173 compounds using mass spectrometry. Several different types of compounds ranging from a carbon number of five (pentane) to 37 (heptatricontane) were identified. The compound types included alkanes, alkenes, alkynes, cyclic saturated compounds and aromatics. Oils produced from different sources and under different conditions differed in alkane to alkene ratios and other key parameters. Greenwood and George [88] performed the GC-MS analysis on solvent extracted hydrocarbon fraction of Tasmanite oil shale to study the mass spectral characterization of several C19 and C20 tricylcic terpanes in the oil. Online MS analyses have also been reported. Hydrocarbons and inorganic compounds up to 200 atomic mass units were observed by Steck et al. [89] using online mass spectrometric analyses of the pyrolysis of Colorado oil shale. The temperature range studied was divided into three zones, 25-350°C, 350-450°C and 450-1250°C and at higher temperatures, compounds with a greater degree of unsaturation were observed. 23 Chakravarty et al. [90] pyrolyzed micro-scale samples of four different oil shales and their kerogens. The compositions of the pyrolysis products did not vary significantly when oil shale or kerogens were used as feed. The variation in the total ion chromatograms (TIC) of the products was possibly due to the variations in the raw material composition. A significant body of work on oil shale pyrolysis with associated compositional and kinetic analysis was compiled at the Lawrence Livermore National Laboratory (LLNL). Campbell et al. [91, 92] studied the kinetics of the evolution of various gas species, CO2, CO, H2, and hydrocarbons (CH4, C2 and C3) on the pyrolysis of Colorado oil shale using a mass spectrometer (Finnegan model-3200 quadrupole) at heating rates ranging from 0.5 to 4°C/min. They considered the pyrolysis temperature from 25 to 900°C and reported that the change in the distribution and amount of the evolved components depended on the heating rate. First order reaction was assumed and kinetic expressions for some of the compounds were reported. Huss and Burnham [93] conducted similar studies to measure the rates of evolution of the light gases (CO2, CO and H2, CH4 and C2 and C3 hydrocarbons) during the pyrolysis of seven Colorado oil shale samples. They analyzed the gases in the pyrolysis temperature range 200-500°C. Tmax of these components were used to derive the kinetic parameters. In a later study with oil shales from saline zones in the Green River formation, Burnham et al. [94] reported decomposition kinetics of several minerals in addition to kinetics of pyrolysis by using online GC-MS. Oh et al. [95] studied real-time evolution of over 30 species by means of a triple quadrupole mass spectrometry (TQMS) to monitor the evolution of water and naphtha up 24 to C9 from five different shales. They reported that the exact Tmax varies with shale and, to a lesser extent, with the molecular weight of the species. The higher molecular weight hydrocarbons have lower Tmax than the low molecular weight species. A single first order reaction model with the Gaussian-distributed activation energy was applied to ethane and total hydrocarbon evolution rates. Activation energy distributions for single hydrocarbons were narrower than for mixtures. Reynold at el. [96] studied the kinetics of oil generation of several oil shales and petroleum source rocks of marine and lacustrian origin. They used programmed-temperature pyrolysis at various heating rates, from room temperature to 900°C and analyzed the products using TQMS. Tmax depended on the sample and the species evolving. Nonhydrocarbon gas formation, particularly H2S, CO2, CO, and H2O was highly dependent on the mineral matrix and mineral matrix-kerogen interactions of the shale. Burnham et al. [97] determined the rates of product evolution during pyrolysis of several petroleum source rocks and isolated kerogens by nonisothermal techniques including Rock Eval pyrolysis and pyrolysis-MS/MS. Burnham et al. [98] used Py-TQMS (Pyromat; a pyrolysis furnace connected to a triple quadrupole mass spectrometer) to understand the maturity of the rock material and evolution rate profiles of light hydrocarbons. The generation rates of methane, ethane and hydrogen gases were compared along with Rock Eval -Tmax of overall products for different sources oil shales. Burnham [99] also studied Bakken oil shale decomposition in detail with different instruments (including Py-TQMS) and reported the organic and inorganic gases 25 generation rates by mass spectrometry. He was able to derive an activation energy of decomposition of about 217 kJ/mol. Braun at el. [100] conducted TQMS analysis of the pyrolysis products of seven oil shales, and petroleum source rocks at heating rates of 1°C/min and 10°C/min to monitor volatile compounds evolution. Kinetic parameters were determined for evolution of hydrocarbons and of various heteroatomic species using the Gaussian distribution method. Activation energies for benezene formation (211.96 kJ/mol) and other light gases were reported. Mass spectroscopic studies have also been conducted to look at the formation of specific heteroatomic species. Ammonia (NH3) evolution during pyrolysis of three Green River formation shales and one Eastern (Devonian) shale was studied using TQMS [101]. Oh et al. [102] reported the decomposition of buddingtonite mineral in the Green River oil shale and monitored the evolution of H2, NH3, H2O, N2 and CO2. Wong et al. [103] used the TQMS setup for the kinetics studies of 10 sulfur species produced from the pyrolysis of raw shales and acid treated shales. Wong and Cowford [104] used a triple quadrupole MS/MS to study high explosives and sulfur-containing pyrolysis gases from oil shale. In addition to the work at LLNL, Meuzelaar et al. [105] studied Py-MS (Pyrolysis followed by online mass spectrometry) of oil shale kerogens and separated alginites of different geological and depositional origins. Oils from Torbanite shale were rich in straight chain hydrocarbons; carboxylic acids dominated the product from Tasmanite, while the Colorado shale oil contained significant amounts of branched chain aliphatic and sulfur compounds. Combined TGA-MS analysis was reported by Khan [106] on 26 selected gaseous products (CO2 and H2O) produced during the study of weathering and preoxidation of eastern (Colorado) and western (Kentucky) oil shales. Marshall et al. [47] also used a TGA-MS unit to study the generation kinetics of key components (CO2, H2O and CH4) during Australian oil shale decomposition. They explained the inflection in the TGA weight loss by different sequential mechanisms such as, moisture loss, organic and mineral decompositions. 2.6. Effect of Operational Parameters on Oil Shale Pyrolysis The pyrolysis conditions such as temperature, heating rate, sweep gas compositions and flow rate, size of the particle and the pressure regulate the product distribution as well as the composition. The study of the combined effect of many factors on oil yield is important in the recovery of shale oil [41]. The yield of the pyrolysis product may also be affected by the raw material composition. However, Stout et al. [107] reported that it is not the organic content in oil shale but the secondary reactions in the oil phase which affects the oil yield. A similar conclusion was reported by Mikien and Maclel [108] for the presence of aromatic carbons in the residual of retorted shale from several geological formations by analyzing the 13 NMR data. The pyrolysis parameters affect the oil quality simultaneously and it was reported that the effects are not additive [9, 41]. The reported results on the effect of pyrolysis conditions in the literature are contradictory. Hill et al. [18] summarized that the cracking of kerogen at minimum decomposition temperature produces primary products with a relatively low molecular weight. These product molecules are sufficiently stable and do not undergo polymerization. At higher temperature, secondary cracking and polymerization reactions 27 occur producing the usual higher pour point and low gravity material. Secondary reactions, cracking and coking, control the distribution of the collected products. Secondary reactions depend not only on the pressure but also on the temperature/heating rate and flow rate of the sweep gas. High temperature pyrolysis offers a low residence time for the oil produced (causing less coking), but exposes the oil to high temperatures (causing more cracking) [52]. But, the opposite is true for low temperature pyrolysis. The dependence of oil yield on the heating rate has been attributed to a competition between evaporation, and the coking and cracking of the oil [13]. The effect of oil cracking on yield is less important when compared to oil coking [9]. Condensation and polymerization are other possibilities for changes in the quality of oil produced [9]. The studies of the organic residue in the spent shales showed that the samples yielding decomposition products contained less organic residue than the samples that had been heated longer at the same temperature [33]. The particle size is important in the pyrolysis of oil shale. The effects of heating rate, temperature and holding time on the pyrolysis of different particle sizes have been reported in the literature. The increase in the size of the particle increases the transport resistance. The effects of size under different operating temperature on oil and gas production rates were interpreted by taking into consideration different physical process occurring during the pyrolysis [109-111]. Charlesworth [49] studied the pyrolysis rate of different particle sizes and concluded that the rate of heat transfer is more important than any physical transport phenomenon as the particle size increases. Torrente and Galan [6] found that transport affected the observed rate when the heating rates are higher (more 28 than 10°C/min). However, they did not observe significant effects of heat and mass transport on the kinetic parameters. The high flow rate of sweep gas, or reduced pressure increases the oil yield by aiding oil evaporation and thereby reducing the liquid phase coking reactions [5, 10, 11]. Higher pressure and lower heating rates during pyrolysis cause a decrease in the oil yield [9]. Carbonate decomposition is also possible at high temperatures. This might fuse the spent shale resulting in a less permeable or porous network in the shale [18]. The loss in oil yield is due to reactions in the liberated oil [107, 112]. The oil degradation process occurs mainly in the liquid phase not in the vapor phase [27, 98, 112]. The decrease of oil yield under high pressure may also be caused by the slow diffusion of oil from the mineral matrix [41]. Burnham and Singleton [9] reported that the chemical mechanism affecting oil yield and composition are somewhat different at higher pressures. The alkene/alkane ratio in the oil decreases with both decreased heating rate and increased pressures [9]. Chalesworth [8, 49] studied the infrared absorbance results during the progress of pyrolysis process and concluded that the destruction of a significant number of the functional groups containing heteroatoms occurs very early in the pyrolysis. The predominant species in the vapors at short contact times or low temperatures are aromatics, isoprenoids, and saturated cyclic and branched compounds. In the middle and later stages of the reaction, the major components in the vapor are 1-alkenes and n-alkanes. The l-alkene to n-alkane ratios depend on the pyrolysis temperature, the type of oil shale, and to a lesser extent on the degree of conversion. The individual 1-alkene to n-alkane ratios were reported to be high at short times and at low conversions. This was 29 interpreted in terms of the thermal destruction of specific functional groups, particularly esters and amides. He also suggested that the reaction leading to the alkanes occurs mostly within the kerogen rather than in the gaseous phase. Burnham and Happe [13] analyzed NMR data of five Green River shale oils to predict the aromaticity and yield of liquid product. They reported that slow heating rates cause hetroaromatic compounds in the oil to be converted to coke, and excessive temperature cause aliphatic moieties to crack to gas. The distribution of aromatic carbon depends on pyrolysis conditions. Marshall et al. [47] also reported a correlation of aromaticity with the yield of volatiles. However, they concluded that during cooling the rearrangement of the products can occur and yield products with varying degree of quality. Noble et al. [113] demonstrated that increasing pressure significantly retards all aspects of the organic matter decomposition. Pressure affects not only the fractional distribution of liquid and vapor of the primary oil but also the degree of oil degradation during secondary reactions. At elevated pressures the rate of thermal cracking increases and significant decrease in specific gravity occurs. Bae [41] reported that the rate is retarded at elevated pressures and polymerization reactions accelerate. Higher pressure reduces the oil yield significantly and produces a large volume of light hydrocarbon gas. The oil produced under high pressure contains higher aromaticity and lower pour point and sulfur and nitrogen do not change significantly [41]. He also reported that the variation in different aspects of oil shale pyrolysis is not significant at pressures higher than 500 psig. Burnham and Singleton [9] reported oil yield, compositions, and rate of evolution from Green River oil shale (Anvil Point mine) for heating rates from 1o-30 100oC/hr and pressures of 1.5 and 27 atm. They concluded that higher pressures and lower heating rates during pyrolysis cause a decrease in oil yield. The oil produced under high pressure was reported to be mixture of lower boiling point substances. Voge and Good [114] reported that the rate constant increases at elevated pressures while the activation energy of overall first order kinetics of Colorado oil shale was relatively constant over various pressures. A similar conclusion was reported by other researchers on the effect of elevated pressure [113, 115] and reduced pressure, vacuum [10], on the activation energy of organic matter decomposition process. 2.7. Modeling of Oil Shale Pyrolysis The decomposition process requires heat input. Several interrelated physical and chemical phenomena occur simultaneously, such as heat transfer, chemical reaction kinetics, multiphase flow, phase changes, and mineral alteration and interaction. Oil shale pyrolysis involves all three phases- liquid, gas and solid. In addition, there is an aqueous phase also involved. Currently, there is no thermal simulator available that includes all the coupled physical processes necessary to effectively model in-situ oil shale conversion [116]. Numerous mathematical models of oil shale thermal treatments have been developed over the last few decades. These models address the oil shale pyrolysis using a rather simpler model to very complicated coupled model. Reservoir Thermal Simulator (STARS) from Computer Modeling Group (CMG) [117] and CKT (model developed at the Petroleum Engineering Research Center, University of Utah) [118], adequately simulate the oil shale thermal treatment to a certain level of complexity. Granoff and Nuttall [119] studied pyrolysis kinetics for single particles (12.7 mm diameter cylinders and spheres) of 22 gal/ton oil shale and developed two mathematical 31 models; shrinking core and homogeneous. They reported that the shrinking core model describes the observed pyrolysis process very well at high temperatures while the nonisothermal homogeneous model applies well to low temperature pyrolysis. The homogeneous model was found to be preferable as it matched the high and the low temperature conversion curves. The models PYROL [120] and PMOD [121] were developed by Lawrence Livermore National Laboratory (LLNL) which include many possible reaction pathways, and constrain the product distribution based on the material and elemental balance. The governing equations for PYROL consist of the time derivatives of 150 variables. These ordinary differential equations are expressed in terms of 100 chemical reaction rates and 32 vaporization/condensation relations. A modified Redlich-Kwong-Soave equation of state is used in calculating the vapor/liquid equilibria and PVT behavior [120]. PMOD [121] is a computer program to model chemical reactions, which are constructed interactively by supplying the empirical formula of the reactants and products and desired reactions. PMOD calculates stoichiometric coefficients which conserve elemental balance. For pressure driven expulsions this model uses the Redlich-Kwong-Soave (RKS) equation of state calculations for an assumed single hydrocarbon phase. A global model for the generation of oil and gas from petroleum source rocks was also presented by Braun and Burnham [122]. This model consists of 13 chemical species and 10 reactions and incorporates alternative mechanistic pathways for type I and type II kerogens. A model developed by Parker at al. [42] includes kerogen pyrolysis, oil coking, residual carbon gasification, carbonate mineral decomposition, water gas shift reaction, 32 and phase equilibria reactions (Table 2-1). Fractured rock was modeled consisting of fracture porosity in which advective and dispersive gas and heat transfer occur and the rock matrix in which diffusive mass transport and thermal conduction occur. They focused on the development and testing of more efficient formulations to simulate heat and mass transfer processes in rubbelized oil shale during in-situ retorting. They noted that the heat and mass transfer rates between permeable fracture porosity and low permeability rock matrix are limited by thermal and mass transport properties of the oil shale. Exxon's electro-frac process model was studied by Symington et al. [116]. They examined the impact of varying process parameters such as heating geometry, size, spacing, total heat input and heating duration using screening tools and basin modeling. A complex Shell Genex model for oil generation and diffusion limited expulsion for 23 lumped species was also reported [123]. In this model, the rate-limiting step of primary migration is considered to be the slow diffusion of the petroleum through the kerogen itself. 2.8. Hydrous Pyrolysis Hydrous pyrolysis involves heating organic-rich rocks in the presence of liquid water [15, 16]. Liquid oil is generated and expelled from the rock and accumulates on the water surface within the reactor. When water is associated with the shale, the pyrolysis process has the potential of producing water [124]. A steady stream of water loss before and after 400°C is because of water formed during thermal loss of organic as water and through some mineral dehydration [47, 124]. The application of water vapor, a source of hydrogen and oxygen, in surface retorting of oil shale has been shown to improve the quality of the oil product [14, 16]. 3. EXPERIMENTAL METHODS AND ANALYTICAL TECHNIQUES This section details the experimental apparatus and various analytical standard techniques used in this research. The general view of the experimental section is described in the first part (section 3.1). A high pressure experimental system was installed to perform multiscale (sanples of different size) pyrolysis. Specific modifications in the experimental setup are mentioned in the chapters where the results obtained are discussed. The second part of this section, Section 3.2, includes the details of analytical instruments that were used for the raw material and product characterizations. Some of these analytical techniques and experimental setups used standard procedures and methods and some of them were developed during this research. 3.1 Experimental Section 3.1.1. Material The oil shale samples used in this study were collected from different locations. The samples were from the Mahogany zone of the Green River formation and were provided by the Utah Geological Survey (UGS). The samples were designated as sample #1 (powdered oil shale (PO)) and sample #2 (core oil shale (CO)). This nomenclature was adopted throughout this dissertation study to represent these samples. The oil shale samples were crushed and dried for 4 hrs at 100°C to remove the inherent moisture, if any. There was no significant weight loss observed during drying and hence the samples were used as received. The samples were screened to 100 mesh size (1.49 x10-4 m) for 34 the raw material characterization. Another set of samples was used from the fresh core drilling of skyline 16 locations and these samples were titled as GR (Green River) samples. 3.1.2. Experimental Procedure Pyrolysis of the fine powdered and small amounts of oil shale provides chemically controlled intrinsic kinetic rate of organic decomposition. Pyrolysis of large size block/core illustrates the distribution of temperature and product generation profiles across the sample. Heat and mass transfer factors influence the distribution of products. Secondary reactions, coking and cracking, in liquid and vapor phases are important and alter the yield and quality of the desired product. The following tasks were designed to study the effects of the operational parameters on the decomposition mechanisms, and on the generation rates of different products. Task 1: Thermal gravimetric analysis (TGA) of the powdered oil shale  Kinetic modeling and validating the intrinsic rate. Task-2: Thermal gravimetric analysis mass spectrometry (TGA-MS) study of the powdered oil shale samples  Continuous monitoring of the targeted components in the generated products.  Study of the compositional analysis and kinetics. Task-3: Multiscale pyrolysis in batch, semibatch and continuous modes  Conduct experiments to study the thermal behavior and product distribution.  Estimate the effect of the transport resistances on yield and quality of the products. 35  Perform pyrolysis under elevated pressure.  Study the secondary reactions (coking and cracking). Task-5: Analytical analyses of bulk products  Perform compositional analyses to study the quality and yield of the products, material balances.  Obtain single carbon number distribution, alkane/nonalkene ratios and residue in oils produced.  Ratio of the products (oil to coke, and noncondensable to condensable gases).  Physical property estimations of the products such as density, viscosity, pour point, etc. In order to accomplish these tasks an experimental matrix was designed and several process configurations were examined. Experiments were performed at four scales; grain size (powdered of finer than 100 mesh) and core samples of ¾", 1" and 2.5" diameters. The apparatuses used for the samples are summarized in Table 3-1. Batch, semibatch and continuous flow pyrolysis experiments were designed to capture the effect of temperature (300°C to 500°C), heating rates (1°C/min to 10°C/min), pressure (ambient and 500 psi) and sample sizes on product formation. The products obtained were condensed vapors (liquids), noncondensable gases, and solid residue (spent shale). The overview of the different reactors, experiment assembly and experimental conditions are listed in Table 3-2. In addition to the tasks mentioned above, hydrous treatment of oil shale pyrolysis and the heterogeneity within the samples were also studied. The results from these experiments are discussed in separate chapters. 36 Table 3- 1: List of the oil shale samples and scales (size) used to study the pyrolysis process with different apparatus. Table 3- 2: List of the experimental apparatus, configurations and conditions used to study the pyrolysis process. Reactors 1" Swagelok 1.25" Swagelok 1.25" Flange 3" Flange Samples Powder 3/4" Core 1" Core 2.5" Core Experiments Batch Semibatch Continuous Liquid collection Condenser Receiver Periodic samples Direct Temperature control Reactor surface Core surface Center of Core Temp program Isothermal Nonisothermal Pressure Ambient 500 psi 3.1.2.1. Thermal Gravimetric Analysis (TGA) Thermal gravimetric analysis (TGA) is a well-known technique to monitor the progress of chemical processes as weight changes. A TGA device (Q500) from TA Instruments was used. This TGA is rated for 1000°C and total of 100ml/min of sweep/reacting and balance gases. The center part of the TGA is a furnace which is electrically heated and allows for a good control of the temperature (under isothermal and nonisothermal temperature programs). A maximum heating rate, 100°C/min, and minimum 0.1°C/min can be employed. The TGA was heated via electric heating elements in the furnace vessel. An accurate control on mass flow rate and ramping heating rate Oil shale sample Scale Apparatus Sample #1 Powder TGA TGA-MS HPTGA Reactor Sample #2 Powder TGA HPTGA Reactor 3/4" Reactor 1" Reactor 2.5" Reactor GR Powder TGA 1" Reactor 37 provide the reproducibility in the data. A thermocouple with four ports measured and controlled the temperature just above the sample basket. TGA experiments were conducted with approximately 20 milligrams of samples in a platinum basket. The basket was suspended from a thin wire attached to a microbalance. Curie point calibration of metals to determine and to adjust the offset in the temperature was carried out using ASTM E 1582 [125]. The calibration of the empty basket and standard sample of calcium oxalate was performed periodically to account for the buoyancy and other instrumental factors affecting the real data generation. The TGA furnace was purged with an inert gas for approximately 15 mins prior to any experiment. For all the experiments, the flow rate of balance gas (N2) was kept constant at 40 ml/min while the purge gas (N2) flow rate was 60 ml/min. The sizes of the particles used along with other conditions employed were specifically designed to reduce the heat and mass transport effects. 3.1.2.2. Thermal Gravimetric Analysis Mass Spectrometry (TGA-MS) A thermal gravimetric analysis mass spectrometry (TGA-MS) instrument was used for inline compositional analysis of the products formed during pyrolysis. TGA-MS affords the opportunity to obtain compositional information while the decomposition is being measured quantitatively. A TGA instrument (TA Instruments Q500) coupled with a mass spectrometer (Thermostat model GSD 301 T3 from Pfeiffer Vacuum) was used. This machine uses the TGA principle and procedure as mentioned in section 3.1.2.1 for TGA apparatus (TGA Q500). The TGA furnace chamber outlet was connected to the MS instrument through a hot capillary column heated to 150°C. Total flow rate of nitrogen was 100 ml/min (90 ml/min as purge and 10 ml/min as balance gas). A maximum of 63 compounds can be analyzed in a single run with this instrument. Compounds of about 38 300 atomic mass units were targeted in the mass spectrometric analyses. The components of the vapor product were identified by single ion monitoring response of mass spectrometry based on molecular weight. 3.1.2.3. High Pressure Thermal Gravimetric Analysis (HPTGA) The high pressure TGA pyrolysis experiments were performed using a Cahn TherMax 500 high-pressure thermo gravimetric analyzer from Thermo Fischer. This instrument is rated up to 1100°C under ambient pressure and 1000°C at 1000 psi and up to a 100 gram sample. A quartz crucible (18 mm diameter and 20 mm height) was used to load the sample. The crucible was suspended from a ceramic coil attached to a microbalance. The furnace and balance were purged with N2 prior to each experiment. Mass data were recorded approximately every second. The buoyancy effect was corrected by using the empty basket data. 3.1.2.4. Multiscale Pyrolysis: Reactor Pyrolysis The experimental matrix was designed to address the effect of active parameters such as temperatures, heating rates, pressures, and scale on pyrolysis products. A schematic of the experimental setup is shown in Figure 3-1. This set up was designed and built for high pressure experiments. This system is fully automated and capable of performing the experiments at different scales (size of the sample). The images of the system are depicted in Figure 3-2. The left panel shows the condenser and autosampler assembly while right panel depicts the reactor position. A simpler form of this setup was also used to perform the experiments, especially for batch, semibatch and ambient pressure conditions. 39 Figure 3- 1: Schematic of the experimental setup to study the effect of operational parameters on yield and quality of the product distribution. Figure 3- 2: Images of the experimental setup to study the effect of operational parameters on yield and quality of the product distribution at different size of sample. N2preheatingP1Ts2T1Reactor with sample, heater and insulatorBPRCompressedN2Tank-1RotameterTs1Check valveBack pressure regulatorPressure relief valveVent lineP2N2line to pressurize the autosamplersCompressedN2Tank-2Gas samplingLiquid samplingMF-2CondensersV1V4MF-1Mass flow meterV2V3V6V7V8V9V10Mass flow meter 2V3540 Four different types of reactors were used (Table 3-1). All the reactors are made of 316 stainless steel rated to 4000 psi at 600°C. The Swagelok reactors, 1" diameter (6" long) and 1.25" diameter (12" long) were equipped with high pressure Swagelok fittings on each end. The flange reactors, 1.25" diameter (8" long) and 3" diameter (10" long) were sealed using graphite flange at both ends. The reactors of 1" diameter and 1.25" diameter were heated with heating tapes while for the 3" diameter reactor, a ceramic heater band was used. The reactor assembly was insulated with self-adhesive high temperature silicon tape and glass wool along the reactor assembly and the fittings. The flange reactors had addition holes to measure the temperature within the core sample. The thermocouples were inserted in the core (approximately 0.6" deep) via drilling a hole of the size of the thermocouple (1/8" diameter). Figure 3-3 shows the positions of the temperature measurement probes (at 5 locations) with 2.5" core samples in 3" reactor. This flange reactor was designed to measure the temperature at three locations (TC-1, TC-4 and TC-5) within the core sample. The Swagelok reactors provide the means to measure the temperature at two locations (TC-1 and TC-5). The temperature of the process was controlled using a bench-top temperature controller with SPECVIEW as the interface via K-type thermocouples. The measuring temperatures and flow readings of mass flow meters were recorded using Labview interface. A Swagelok back pressure regulator (BPR) was used on the outlet line to maintain the process pressure. The metal tube which connects the reactor outlet to back pressure regulator was heated at 200°C. The temperature of condensers was maintained using a Brookfield TC501 programmable temperature bath with controller. The position of the 12 port autosampler was regulated using a VCOM interface. 41 TC-3 TC-4 TC-5 TC-2 TC-1 2.5" Figure 3- 3: Schematic of temperature distribution measurements during the pyrolysis of large size (2.5") sample. Nitrogen was used to purge the reactor, sweep the products (100 ml/min) in open system pyrolysis and to pressurize the system for high pressure experiments. The resulting spent shale and oil were weighed. The isothermal pyrolysis runs were conducted by using a rate of 100°C/min to achieve the desired stable temperature. The amount of noncondensable gases (gas loss) was estimated by material balance, difference of weight loss and oil yield. A sampling protocol for gas and liquid samples was set up to collect the fractions of the fluid product at different times and temperatures during the continuous flow (open reactor) pyrolysis. The gaseous products were collected in a tedlar bag of 1 liter capacity. Gas chromatography analyses were conducted on collected oil and gas samples without further treatment. Batch experiments (closed system) were conducted under initial ambient and pressure, 500 psi. The sample was fed in the reactor and purged with nitrogen to displace the air in the reactor. To perform the batch pyrolysis, the reactor assembly was sealed at both the ends and the pressure measurements were recorded as the reaction progressed. TC-1: Center of the core TC-2: 0.75" from center of the core TC-3: 1" from the center of the core TC-4: Core surface (or annulus) and TC-5: Reactor surface 42 After the pyrolysis, the reactor assembly was cooled down to room temperature and samples were collected through a needle valve. The semibatch (autogenous) pyrolysis involves no sweep gas. The products were allowed to escape from the top of the reactor as they formed due to autogenous pressure and were collected in the chilled condenser maintained at -6°C using acetone and ice in a bath. The continuous flow experiments, also known as open system pyrolysis, were designed to collect the products as they are formed using a sweep gas, nitrogen. The nitrogen gas was heated to the process heating rate and temperature before passing through the center of the reactor. The products were swept out from the reactor with the nitrogen and then passed through the condenser. Periodic sampling of the products was carried out. The aim of these experiments was the collection of the liquid and gaseous samples at different time intervals and subsequent analyses of the samples to obtain the distribution of the products. Specific modifications were also made in the experimental setup as per the need of the experiments. For example, the control of the heat supply, to maintain the process temperature, was controlled using TC-1 (center of the core) or TC-5 (surface of the reactor) thermocouple, and a setup to minimize the dead volume was built. In some of the ambient pressure experiments, a receiver was used to collect the heavy fraction of liquid, which otherwise would plug the condenser assembly. The modifications are discussed in the study appropriately. The experimental conditions and results are summarized in Appendix C for all the experiments discussed in Chapter 4. There was a temperature gradient across the large 43 size shale upon applying the heat from external sources. Therefore the different sections of the shale were at different temperatures. The temperature and pressure profiles (batch pyrolysis) are shown in Appendix D. 3.2. Analytical Techniques This section describes the procedures and principles which were applied to analyze the raw and product materials. Raw material characterization was conducted using elemental analysis (CHNSO), thermal gravimetric analysis (TGA) and X-ray diffraction (XRD) analysis. Thermal gravimetric coupled with Mass spectrometry (TGA-MS) was used to perform the compositional analysis of the products formed during the pyrolysis process. The bulk fluid products, gas and liquid, of the pyrolysis process were analyzed using gas chromatography (GC) and gas chromatography mass spectrometry (GCMS). A TGA-DSC (Differential scanning calorimetric) instrument is used to estimate unreacted organic and coke formation in spent shales. Fourier transformation infrared spectroscopy (FTIR), densitometer and rheometer were used to estimate the physical properties of the oils produced. 3.2.1. Material Characterization The total organic matter contains in the oil shale samples of different origin; geological depth and horizon were suspected. Thus, it becomes important to understand the raw material and the variability which exists in different samples. Elemental analysis (CHNSO), TGA (weight loss due to organics and decomposable minerals) and XRD (minerals) analyses were conducted to characterize the oil shale samples used in this research work. 44 3.2.1.1. Elemental Analysis The elemental analyses of the samples were performed using LECO CHNS-932 for CHNS (carbon, hydrogen, nitrogen, sulfur and oxygen) and VTF-900 for oxygen analysis in the samples. LECO analyzer (LECO Corp., St. Joseph, Michigan) used IR and thermal conductivity detectors to determine the percentage of elements in the sample. A combustion method was employed to measure C, H, N, S content. A CHNS run uses approximately 2 mg of sample. A separate oxygen analysis also requires the same amount of the sample. Standard materials, sulfamethazine (C12H12N4O2S) acetanilide (C8H9NO) along with blank air runs were used to calibrate the instrument periodically. All the samples were duplicated several times and the results were averaged to determine the percentage of the elements in the sample. 3.2.1.2. X- Ray Diffraction (XRD) Analysis X-ray diffraction (XRD) analyses of the crushed oil shale samples and separated clay fractions were performed using a Bruker D8 Advance X-ray diffractometer. Phase quantification was performed using the Reitveld method and the TOPAS software. The following operating parameters were used when analyzing the powdered samples: Cu-K-α radiation at 40 kV and 40 mA, 0.02o2θ step size, 0.4 and 0.6 seconds per step, for clay and bulk samples respectively. Clay samples were examined from 2 to 45o 2θ, and the bulk from 4 to 65o 2θ. The instrument was equipped with a detector (lynx eye) which collects data over 2.6 mm, rather than at a point. Rietveld method calculates intensities from a model of the crystalline structure and fit to the observed X-ray powder pattern by a least squares refinement. The samples were ground in a micronizing mill until they were fine enough to pass through a 325 mesh screen (particle size < 44 micrometers). The 45 clay fraction from each sample was separated from the bulk by using prticle sedimentation. The fraction used for the bulk analysis was rolled approximately 50 times to randomly orient the mineral grains before being scanned. The air dried and glycolated scan patterns were compared to determine if expandable clays were present. The amount of the identified clay minerals were determined by using the Rietveld refinement of the bulk scans. 3.2.2. Compositional Analysis A Thermal Gravimetric Analysis Mass Spectrometry (TGA-MS) instrument was used for inline compositional analysis of the products formed during pyrolysis (Section 3.1.2.2). Gas chromatography (GC) and gas chromatography combined with mass spectrometry (GC-MS) analyses were performed to characterize the bulk products, liquid and gas collected from reactor pyrolysis. Spent shale analyses were performed with thermal gravimetric analysis differential scanning calorimetry (TGA-DSC) and LECO elemental analyzer instruments. 3.2.2.1. Gas Chromatography (GC) GC was used for qualitative as well as quantitative analysis in this study. Fluid products, liquid and gas, from the pyrolysis were analyzed using Gas chromatography. Agilent GC HP 5890 and GC HP 6890 were used in this study. GC 5890 used cool on column injection assembly while with GC HP 6890, split injection were carried out. As the hydrocarbons are the main products of interest, a conventional flame ionization detector (FID) was employed in most gas chromatographs. Few analyses of gaseous products were performed with thermal conductivity detector (TCD) followed by FID detector assembly to identify the composition of inorganic and very light hydrocarbons. 46 Oil samples were analyzed using the principle of High Temperature Gas Chromatography (HTGC) to obtain retention time information for the hydrocarbons and residual calculation [126]. The GC simulated distillation (GC-SIMDIS) analysis was also performed on the liquid samples. The procedure provides the weight percent of a given SCN as well as the weight percent of n-alkane and non n-alkane portions for each SCN. The GC-SIMDIS method is intended to simulate the true boiling point (TBP) method by providing single carbon number (SCN) distributions. GC-SIMDIS was used to obtain a single carbon number (SCN) distribution of the sample up to carbon number C44.The samples were prepared according to the ASTM-5703 [127] standard using dichloromethane (DCM) solvent. DCM is selected as the solvent because it dissolves hydrocarbons (oil) well and also has a lower boiling point (40°C) that helps in separating the signal in chromatogram. Two SIMDIS samples were prepared for each sample analyzed. One sample was diluted with DCM. An internal standard (HP part no 5080-8723), a mixture of normal paraffins , C14 to C17, was added to the other sample followed by dilution with DCM. The sample injections (0.2μl) were performed by the autosampler (HP-7683). Restek MXT-1(steel coated fused silica capillary) column (dimension, 30m x 0.28 mm x 0.1μm) with stationary phase of cross bonded dimethyl polysiloxane was used for the liquid sample analyses. The operating conditions of the gas chromatography for the GC-SIMDIS method are summarized in Table 3-3. The FID detector responses were manually integrated. The integrated area under the curve for each carbon number peak was used to determine the SCN distribution. A retention time table, developed by analyzing a laboratory standard containing normal paraffin ranging from C12 to C60 was used to identify the n-alkane peaks for each SCN. 47 Table 3- 3: Operating conditions of gas chromatography for cool on column injection (GC 6890) and split injection (GC6890). Oven Initial Temperature 30°C Ramp Rate 10°C/min Final Temperature 410°C Isothermal 10 mins at 410°C Inlet Carrier Gas Helium at 1ml/min, constant flow Temperature Tracked over (3°C over oven temperature) for cool on column injection 350°C for split injection with split ratio (20:1) Detector Temperature 450°C Flows Air- 450 ml/min Hydrogen- 40 ml/min Nitrogen-45 ml/min The procedure was described in detail in the standard test method ASTM D 5307 [127] and Neer and Deo [126]. Several standard samples were used to calibrate the chromatograms. The changes in the conditions of gas chromatography for both liquid and gas samples over the time period of this research were calibrated using the standards periodically, especially, each time before running the batch of the samples. A MATLAB program was developed to classify the chromatogram in SCN, normal alkane and non normal alkane, and residual calculation. 3.2.2.2. Gas Chromatography Mass Spectrometry (GC-MS) A GC-MS equipment from Agilent was used in this study. The machine is an assembly of Agilent GC-6890 and a triple quadrupole MS (5397N). A 60 meter long capillary column, HP-5 (5% phenyl methyl siloxane) of J&W Scientific was used. The transfer line temperature was kept at 280°C. The program of GC operation was the same as described in the section 3.2.2.1. Several standard normal paraffin samples were used to 48 judge the predictability of the of library match from National Institute Standard and Technology (NIST) for the peaks detected by MS. 3.2.2.3 Thermal Gravimetric Analysis and Differential Scanning Calorimetry (TGA-DSC) The spent shale obtained from the pyrolysis of oil shale may contain unreacted organic and the coke formed during the process. A combined TGA-DSC unit, SDT Q 600, from TA Instruments was used to characterize the spent shale and estimate the unreacted organic and coke. TGA Q-600 works on the same principle as TGA Q-500. The thermograms of DSC were used to judge the energy input, endothermic, organic and mineral decomposition, and exothermic, coke burning. The experimental scheme of different stages was designed to separate the weight losses of the organic matter, mineral matter and of the coke formation. Initially, pyrolysis till 500°C (stage-1) was carried out for organic decomposition, followed by the second pyrolysis up to 900°C or 1000°C (stage-2) for mineral decompositions and then without opening the TGA chamber, the furnace was cooled down to 400°C and the remaining material was combusted from 400°C to 900°C or 600°C (stage-3) to estimate the amount of coke. A heating rate of 10°C/min was used for these analyses. It is hypothesized that in the first pyrolysis, only organic, in the second pyrolysis, only minerals and in the combustion process, only carbon residue material (coke) contributes to the weight loss. It was also hypothesized that coke was formed only durin