Combustion of carbonaceous residues on spent oil sands in a transport reactor (Abstract)

A laboratory scale dense-phase transport reactor was designed, fabricated and constructed to study the combustion of carbonaceous residues on spent oil sands produced during the fluidized bed pyrolysis of oil sa.nds. A wide particle-size distribution group B coked sand, dp = 130 μm, was used for the hydrodynamic and combustion studies. The average minimum fluidization velocity, Umf• determined during a series of fluidization and defluidization experiments, was 1. 7 emfs. The transition velocities were determined in flow regime transition studies: (a) the plug slugging transition velocity, Urns· was 22 emfs; (b) the turbulent fluidization transition velocity, Uc, was 50 emfs; and (c) the refluxing pneumatic transport transition velocity, Uk, was 75 cm/s. Particle residence time distribution experiments indicated the average particle residence time in the reactor was approximately six minutes in the turbulent fluidization regime. The effects of process variables on the combustion of the coked sand were investigated. Coked sand combustion experiments at different superficial gas velocities indicated that there was an preferred superficial gas velocity, approximately 60 cm/s, at which the highest coke conversion was achieved. The results also indicated that CO production rate increased whereas co2 production rate decreased with increasing superficial gas velocity. Coke conversion increased with increasing combustion temperature but leveled off above 946 K. The coke conversion increased with decreasing solids feeding rate at a fixed temperature. Coked sand combustion with oxygen enriched air as the fluidizing gas indicated that using oxygen enriched combustion gas increased the coke conversion. Preliminary studies were conducted to evaluate the effect of gaseous swirl flow on coked sand combustion. Coke conversion increased with swirl flow at a fixed temperature and solid feed rate relative to fully developed plug flow through the reactor. It is expected that coked sand combustion could approach completion with a combination of induced swirl flow, higher combustion temperatures and oxygen enriched fluidizing gas.

COMBUSTION OF CARBONACEOUS RESIDUES ON SPENT OIL SANDS IN A TRANSPORT REACTOR By Hong Qing Tang A dissertation submitted to the f acuity of The University of Utah in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Chemical and Fuels Engineering The University of Utah August 1995 r ABSTRACT A laboratory scale dense-phase transport reactor was designed, fabricated and constructed to study the combustion of carbonaceous residues on spent oil sands produced during the fluidized bed pyrolysis of oil sa.nds. A wide particle-size distribution group B coked sand, dp = 130 μm, was used for the hydrodynamic and combustion studies. The average minimum fluidization velocity, Umf• determined during a series of fluidization and defluidization experiments, was 1. 7 emfs. The transition velocities were determined in flow regime transition studies: (a) the plug slugging transition velocity, Urns· was 22 emfs; (b) the turbulent fluidization transition velocity, Uc, was 50 emfs; and (c) the refluxing pneumatic transport transition velocity, Uk, was 75 cm/s. Particle residence time distribution experiments indicated the average particle residence time in the reactor was approximately six minutes in the turbulent fluidization regime. The effects of process variables on the combustion of the coked sand were investigated. Coked sand combustion experiments at different superficial gas velocities indicated that there was an preferred superficial gas velocity, approximately 60 cm/s, at which the highest coke conversion was achieved. The results also indicated that CO production rate increased whereas co2 production rate decreased with increasing superficial gas velocity. Coke conversion increased with increasing combustion temperature but leveled off above 946 K. The coke conversion increased with decreasing solids feeding rate at a fixed temperature. Coked sand combustion with oxygen enriched air as the fluidizing gas indicated that using oxygen enriched combustion gas increased the coke conversion. Preliminary studies were conducted to evaluate the effect of gaseous swirl flow on coked sand combustion. Coke conversion increased with swirl flow at a fixed temperature and solid feed rate relative to fully developed plug flow through the reactor. It is expected that coked sand combustion could approach completion with a combination of induced swirl flow, higher combustion temperatures and oxygen enriched fluidizing gas. v TABLE OF CONTENTS ABSTRACT................................................................................................... iv LIST OF TABLES.......................................................................................... ix LIST OF FIGURES . .......... ........... ....................... .. .. . . .. ............. ... .. .. . ....... ...... xi NOMENCLATURE ................................................. ....................... .... ........... xiv ACKNOWLEDGMENTS............................................................................... xvii CHAPTER 1 INTRODUCTION................................................................................ 1 1.1 Research Objectives ........... ..... .......... .. ....... .......... ..... ....... ...... 7 2 LITERATURE SURVEY..................................................................... 9 2.1 Oil Sand Resources................................................................. 9 2.2 Oil Sand Recovery Methods . ... . . . ... ... . . ....................... .. . .......... 1 O 2.2.1 In-Situ Bitumen Recovery Technologies .. . .. .. .... . .. .... .... 12 2.2.2 Surface Bitumen Recovery Methods............................ 16 2.3 Fluidized Bed Combustion ...................................................... 20 2.3.1 Comparison of Bubbling, Circulating and Pressurized Fluidized Bed Combustion ... ......... .. .. 22 2.3.2 Innovative Designs of FBC ........................................... 36 2.4 Fluidized Bed Incineration ....................................................... 38 2.5 Combustion Kinetics of Coke/Char on Spent Shale/Sand ..... 48 3 EXPERIMENTAL APPARATUS AND PROCEDURES................... 52 3.1 Coked Sand Feeder Design, Construction and Calibration . . . . . . .. .. .. . . . . . . . . . . . . . . . . .. .. .. . . . . . . . . .. . .. . . . . 52 3.2 Reactor Design and Construction .. . . . . .. . ..... .. .. . . ..... ... ...... ......... 64 3.2.1 Reactor Body................................................................ 64 3.2.2 Gas Distributor.............................................................. 65 3.2.3 Heating and Ignition Furnace........................................ 65 3.3 Air Supply and Preheating....................................................... 68 3.3.1 Mass Flow Control........................................................ 73 3.3.2 Air Preheating ..... ... ... .............. ..... .... . . ..... .... ........ ... .. ..... 7 4 3.4 Gas - Solid Separation .................... .......... ... . ... . . . ................ .. .. 7 4 3.5 Process Monitoring and Control.............................................. 77 3.5.1 Temperature Monitoring and Control............................ 77 3.5.2 Pressure Data Logging................................................. 78 3.5.3 Mass Flow Rate Data Logging..................................... 81 3.6 Combustion Experiment Operating Procedures..................... 86 3.7 Product Sampling and Analysis............................................... 95 3.7.1 Flue Gas Sampling and Analysis................................... 95 3.7.2 Burnt Sand Sampling and Analysis.............................. 100 3.8 Material Balance Calculations................................................. 104 4 RESULTS AND DISCUSSION.......................................................... 107 4.1 Solid Feed Material Preparation.............................................. 107 4.2 Hydrodynamic Studies............................................................. 108 4.2.1 Fluidization and Defluidization ... .. ... . . .. ..... ... .. . ...... .... ..... 112 4.2.2 Flow Regime Transition Studies................................... 123 4.2.3 Particle Residence Time Distribution Studies.............. 141 4.3 Combustion Studies .................................. ....................... ....... 153 4.3.1 Effect of Superficial Velocity on Coked Sand Combustion......................................... 154 4.3.2 Effect of Combustion Temperature on Coked Sand Combustion......................................... 165 4.3.3 Effect of Solids Feeding Rate on Coked Sand Combustion......................................... 171 4.3.4 Effect of 02 Concentration on Coked Sand Combustion......................................... 171 4.3.5 Effect of Swirling Flow on Coked Sand Combustion......................................... 175 4.4 Carbon Balances in the Laboratory-Scale Fluidized Bed Combustion Reactor . . ........ .... .. .. . .... .. .. .. ........ .. . 180 5 CONCLUSIONS................................................................................. 183 vii APPENDICES A TRANSPORT FLUIDIZED BED REACTOR DESIGN CALCULATIONS................................................................ 187 B THERMAL CONDUCTIVITY DETECTOR RESPONSE FACTOR DETERMINATION ... . . .. . ....... ............ .. ... . ...... 197 C EVALUATION OF COKE ANALYSIS DAT A..................................... 207 D EXPERIMENTAL DATA FOR COKED SAND COMBUSTION RUNS ..................................... 212 REFERENCES . ................ .. . ............... ..... .. .. . .. ............. ......... .. ................ .. .... 213 VITA............................................................................................................... 227 viii LIST OF TABLES Table Page 1. Typical Coked Sand Elemental Analyses.............................................. 6 2. Estimated Oil Sand Resources of Utah ................................................ , 11 3. Specifications of the Heating Elements . . . . ... . ...................... ...... ... .... ...... 68 4. Mass Flow Controller Calibration........................................................... 73 5. Sieve Analyses of Coked Sand Screened Through a Number 18 Sieve .. . .. .. .. . . .. . . . . . .. .. . . . . . .. . .. . . .. .. . . . . . . .... . 1 09 6. Coke Conversion as a Function of Superficial Gas Velocity at a Fixed Combustion Temperature and Solids Feeding Rate............ 155 7. Coke Conversion as a Function of Solids Feeding Rate at a Fixed Superficial Gas Velocity and Combustion Temperature .. .... 172 8. Effect of o2 Enrichment and Temperature on Coked Sand Combustion .. . . .. . . . . .. .... . .... ... . . .. . . . . . . .. . . .. . . .. .. . . .. . .. . . .. . .. . . .. . . 17 4 9. Effect of Swir1 on Coke Conversion....................................................... 181 81. Composition of the Standard Gas.......................................................... 198 82. GC Analytical Results for a Standard Gas Using Local Integrator........ 199 83. GC Analytical Results for a Standard Gas Using HP Integrator ........... 200 84. Response Factor Calculation for Scotty Standard Gas ........................ 202 85. Composition of the Certified Calibration Gas........................................ 202 86. GC Analytical Results of Scotty Certified Calibration Gas at Low Detector Sensitivity with HP Integrator....................................... 204 87. GC Analytical Results of Scotty Certified Calibration Gas at High Detector Sensitivity with HP Integrator...................................... 205 88. Response Factor Calculation for Scotty Certified Calibration Gas....... 206 C1. Coke Content Detennined by Muffle Furnace Combustion ................... 208 C2. Summary oft-test Results...................................................................... 210 x LIST OF FIGURES Figure Page 1. Oil Sand Bitumen Recovery Schemes ...................... ....... ..................... 5 2. Fluidization Regimes Employed in Fluidized Bed Reactors................... 24 3. Bubbling Fluidized Bed Reactor............................................................. 26 4. Circulating Fluidized Bed Reactor.......................................................... 29 5. Pressurized Fluidized Bed Combustion Reactor................................... 32 6. Bubbling Fluidized Bed Incinerator . ... ................ .. ......... .......... ... . ... ........ 42 7. Circulating Fluidized Bed Incinerator..................................................... 45 8. Schematic of Experimental Apparatus................................................... 54 9. Schematic of the Solids Feeder............................................................. 56 10. Cumulative Weight Fed versus Feeding Time at Various Controller Settings .... ..... .. .. .............. .. .. ... .. ... .. ... .. ...... .. .. .. . ..... 59 11. Feeding Rate versus Feeding Time at Various Speed Controller Settings..................................................... 61 12. Average Feeding Rate versus Feeder Controller Settings................... 63 13. Schematic of the Reactor....................................................................... 67 14. Wiring Diagram of Heating Elements ..................... ............................... 70 15. Flow Diagram of Air Supply System ...................................................... 72 16. Dual Cyclone Solids Separation System............................................... 76 17. Typical Temperature Profile . .. . . . . . .. ............ ......... .... ....... .. .... .. . . ...... ......... 80 18. Schematic of Pressure Data Logger Configuration............................... 83 19. Calibration of the Pressure Transducer................................................. 85 20. Schematic of Mass Flow Rate Data Logging System........................... 88 21 . Mass Flow Rate Calibration . . . . .. .. .. . . . .. . ... . . . . .... .. .. .. .. . ... . . . . .... . .. .. . . . .. .. .. .. . . . . 90 22. Typical Output from Mass Flow Rate Data Logging···························:·· 92 23. Schematic of the Flue Gas Sampling System....................................... 97 24. TGA Analysis of Coked Sand ..... ..... ...................................................... 103 25. Coked Sand Average Particle Size Distribution.................................... 111 26. Typical Fluidization and Defluidization Curves for Multi sized Particles . . ... .. ......... ... . . .. . . . .. . ......... .. . .. . . ... . ........... ......... ...... 114 27. Fluidization and Defluidization Pressure Drop versus Superficial Air Velocity for Multisized Coked Sands (H/D=2.5) ............................... 117 28. Fluidization and Defluidization Pressure Drop versus Superficial Air Velocity for Multisized Coked Sands (H/0=3.5) ............................... 119 29. Fluidization Pressure Drop versus Superficial Air Velocity for Multisized Coked Sands .......... ......................................................... 121 30. Typical Flow Regimes Observed in Gas-Solid Fluidized Beds............. 125 31. Pressure Drop versus Operation Time and Superficial Air Velocity............................................................................ 132 32. Standard Deviation for Pressure Drop versus Superficial Air Velocity............................................................................ 134 33. Standard Deviation for Pressure Drop versus Superficial Velocity at Different Temperatures ....................................................... 137 xii 34. Typical Particle Residence Time Distribution Curves in a Fluidized Bed with Constant Solids Feed ....................................... 144 35. Tracer Concentration versus Solid Particle Residence Time............... 147 . 36. Comparison of the Tracer and Coked Sand Particle Size Distributions............................................................. 149 37. Tracer Concentration versus Residence Time with KMn04 and KMn04 Coated Sand Tracers ........................................... 151 38. Coke Conversion versus Superficial Gas Velocity................................ 157 39. CO and co2 Concentrations versus Superficial Gas Velocity............. 160 40. CO and co2 Production Rate versus Superficial Gas Velocity ............ 162 41. Coke Conversion versus Combustion Temperature .. . . . . . . . .. . . . . . . . . . . . .. . . . .. 167 42. Test for the Kinetics of Coked Sand Combustion .................................. 170 43. Schematic of the Swir1 Blade Configuration ............. ..... ................. ....... 177 44. Swir1 Blade Position in the Reactor ........................................................ 179 xiii