Recovery and upgrading of oil from Utah tar sands

The University of Utah tar sands research and development program has progressed well in its second year of the current three-year contract. The program has advanced significantly toward its long-term objectives. The long-term objectives of this program remain the development of scientific and engineering data required for the commercialization of domestic tar sands. Areas that have been given research attention are bitumen upgrading, thermal recovery by fluidized bed retort, thermal recovery by an energy efficient heat pipe process, and water-assisted separation of bitumen from ore. In the area of bitumen upgrading, substantial progress was made in understanding the chemistry of upgrading bitumen to distillate products. A reaction network for hydropyrolysis was proposed and verified using model compounds and petroleum distillates. The model is based on the carbon-type description of the bitumen. The principal reactions in hydropyrolysis are cracking of paraffins and naphthenes, dealkylation of aromatics, cracking of naphthenoaromatics, hydrogenation of aromatics, and dehydrogenation of naphthenes to form aromatics. Reaction kinetics of each of these reactions were studied. A very important finding was that the dealkylation reactions are fast reactions and are directly related to the hydrogen-atom concentration in the reaction system. The hydrogen-atom concentration can be estimated through an index developed based on propane and propyleneconcentrations. Hydrogen consumption was determined as a function of the various reactions taking place that require hydrogen. In this analysis, it was found that most of the hydrogen is required for the non-condensible gas production. Thus, it has been reaffirmed that optimum conditions for hydropyrolysis will constitute those conditions which produce the maximum amount of liquid with the greatest liquid quality. The results of this work will greatly assist the engineering design phase for the third year of the project. 3 Studies of thermal recovery of bitumen using fluidized-bed technology have also progressed well. A four-inch reactor has been designed and partially fabricated under the second year of this funding. This reactor design is based in part on a kinetic model which was produced from the small scale reactor. This model contains the reaction rate constants for the reactions of bitumen, heavy oil, and light oil to the various gaseous, liquid and coke products. Both a numerical and an analytical solution were obtained for the reaction network. Fluidized-bed retorting of tar sands continues to show promise as an operable and viable method for recovering values from tar sands. Process design, economic evaluation, and thermodynamic analysis were completed for the University of Utah two-stage thermal recovery process. In this process, thermal energy for heating the feedstock is obtained from the energy released by combustion in the lower bed. Economic analysis were conducted for a 50,000 and a 15,000 bbl/day plant for feedstocks containing 8, 10, and 12% bitumen. Costs for the 50,000 bbl/day plant case were $16.32/bbl for the 8% bitumen case, and $9.44/bbl for the 12% bitumen case. Capital costs were $418,000,000 and $343,000,000 for the two cases, respectively. Capital investment per unit capacity is relatively insensitive to plant size between 50,000 and 15,000 bbl/day because multiple units of maximum size equipment are necessary in most sections of the plant. Details of the economic evaluation are contained in the body of the report. In the modified hot water separation technology research, a better understanding was obtained in the area of the mechanism of displacement of bitumen from the surface of the sand. A fundamental study of the adhesion energy associated with the bitumen solid interface was initiated to further understand this mechanism. This analysis involved the measurement of the surface tension of bitumen solutions at various temperatures, and the measurement of the contact and angle between the sand surface and the bitumen. The hot water process was also studied in a low-shear force field. The results from the development of this low-shear digestion procedure are expected to be of significance in 4 the commercialization of the hot-water process. Under the low-shear conditions, ultimate recovery was found to be in excess of 90%. Percent of bitumen in the concentrate remains at an acceptable level except for certain cases at lower temperatures. Low shear conditions are expected to result in reduced energy requirements at the commercial level. Progress in our second year has been sufficient that renewed attention is now being paid to the ultimate tasks of comparative analysis of various technologies and technology selection. In the third phase of our current contract period, efforts will be made to establish a basis whereby such a study can commence. Process selection and final engineering design data will be the subject of work during the next contract period.