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DOE/FE/60177—2315

DOE/FE/ 6 0 1 7 7 — 2 3 1 5 DE87 008920

PYROLYSIS OF ASPHALT RIDGE TAR SAND

By T. F. Turner L. G. Nickerson

August 1986

Work Performed Under Cooperative Agreenent DE-FC21-83FE60177

For U.S. Department of Energy Office of Fossil Energy Morgantown Energy Technology Center Laramie Project Office Laramie, Wyoming

By Western Research Institute Laramie, Wyoming

SUMMARY Isothermal and nonisothermal pyrolysi's experiments have been inducted on Asphalt Ridge tar sand. Oil produced from the isothermal xperiments has a molecular weight of approximately 250 and has a ydrogen to carbon ratio between 1.7 and 1.9. Product oil composition jries slightly with reaction time. Results of thin layer hromatographic separation of the residual bitumen show that the ancentrations of saturates and aromatics in this bitumen decrease apidly with increasing reaction time while the concentrations of romatics and polars in this bitumen increase. Polars and polynuclear romatics are the dominant species in this bitumen. Nonisothermal data ave been analyzed using a distributed activation energy technique. hese tests show a distinct bimodal weight loss curve. The low emperature weight loss peak has a maximum about 275°C (527°F) and a irst order apparent activation energy below 10 kcal/mol. The high emperature peak has a maximum above 400°C (752"F) and an apparent ctivation energy of about 60 kcal/mol.

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INTRODUCTION The United States has an estimated tar sard resource of 54 billiV". barrels including measured and speculative resources (IOCC 1984). 3ecause of the United States' energy dependence, it is critical that efficient methods of recovery be developed for this substantial resource. Of special interest for the economies of the western states is that Utah contains approximately 36% of the U.S. tar sand resource. Much of the bitumen found in tar sand will have to be recovered by an in situ thermal treatment which lowers the viscosity of the bitumen allowing recovery by pumping. Two thermal treatment methods are steam and combustion drive techniques. In a steam drive process, high pressure, high temperature steam is injected into the formation through one or more injection wells while water and heavy oil are pumped at one or more prodjction wells. In a typical forward combustion process, permeability is established between injection and production wells, air is injected, and bitumen is ignited. The combustion front moves from injection to production well consuming the residual carbon produced in the cracking of the bitumen. Distillation, cracking and visbreaking generate mobile hydrocarbons which are collected at the production well. The quantities and properties of the products from thermal processes are dependent on the relative amounts of bitumen cracking and distillation. Therefore, the study of cracking kinetics is important to fully understand and utilize thermal processing of the resource. The cracking kinetics of the bitumen in tar sand has been studied by several researchers. Barbour et al. (1976) surveyed the cracking kinetics of several tar sand bitumens, including bitumens from the Asphalt Ridge, PR Spring, Tar Sand Triangle, and Sunnyside deposits in Utah and the Athabasca deposit in Alberta. Isothermal pyrolysis experiments were conducted on bitumen extracted from the raw tar sand. The resulting apparent actfvation energies for production of volatile materials were . between^33 and 35 kcal/mbl for all samples. Hayashitarn et.a].(1977) studied t;he Isothermal % crocking iTfnetics and product distribution ;«'%, ? ; issbclgted' with y'j?nl'^th'aba'sca "bitumen, .which was free of minerals and f wal^f1. 'They used !a four pseudo-component model to prejict ife;; : production and loss of distfllablfes, heavy oils',- aspha^t^e*'; m$ " /Wcoke. The apparent: activation energies for^ ithis^scliemeRanged f f ^ 4 ^ ^ 7 / ^ kc^l/mo]. forgthe; J$rm^(p;n "af coke jErqm^sBh^i^enes, to;,6?,^/kcaJ/m}}l for; fcfje ^formation/-of" hVavj ?ofls from -asphalteries. . T h e fojjjjiatjon of distiTTables had an apparent activation energy igf' 57/.5 .kcal/mdl, :a valu£ much higher than J!ie/en§rgy: measure^b/^a^fiiir^t ^1-^19761^ y-^ ^ 'm^ui^M^M^'1^^

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* ; •;'* Tsdt henna 1 : pyrol/sfs, e^xpeiM mentT' ;by • Phi 11 i ps et al. ^ 1985) on Athabasca'bitumen with ancf without sand showed that having sand present increased the yields of; coke and .^ases and decreased'the* apparent activation energies for 'the .fbtmatiori on' decomposition of six pseudocomponents. For example, the apparent activation energy for the formation of distillables in the presence of sand was 44.2 kcal/mol, but the energy without sand was 58.8 kcal/mol, indicating that sand acted as a catalyst for decomposition of bitumen. Clearly, it is important for the design or modeling of a process that kinetics data be available on the decomposition of bitumen in the presence of sand. No such data are available for the Utah tar sand resources. 1

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As part of the e f f o r t to understand and u t i l i z e the Utah tar sand resources; kinetic parameters, o i l properties, and product distributions were measured in laboratory scale experiments on Asphalt Ridge tar sand. In the experiments described in this report, bitumen was cracked isothermally in the temperature range 375-425°C (707-797'F) and nonisothermal ly in the temperature range 30-1200°C (86-2192'F) in the presence of sand. EXPERIMENTAL Isothermal Tar sand samples for the isothermal and nonisothermal experiments were prepared by f i r s t crushing and then s p l i t t i n g s u f f i c i e n t tar sand for the tests. Splitting and crushing were accomplished by mixing dry ice with the tar sand. Nominal forty gram aliquots were sealed tfttder nitrogen and stored in a refrigerated room. Small samples were removed for the nonisothermal tests. All isothermal tests were conducted in a reactor system (Figure 1) consisting of two para.iel u-tube reaction vessels and associated flow and heat control systems. In a typical tar sand pyrolysis experiment, twenty-gram samples of tar sand were inserted into each reactor, helium sweep gas lines were attached and a t h i r t y m i l l i l i t e r per minute sweep was started at five pounds of back pressure on each reactor system. The reaction vessels were rapidly heated by plunging them into a preheated laboratory sand bath. Condensible products ( o i l ) of the pyrolysis were collected in a dry ice trap common to both reaction vessels. Gases were analyzed using an on-line Hewlett Packard Model 5890 gas chromatograph f i t t e d with a Porppak N column. The pyrolysis reactions were quenched after a predetermined ryn timeby removing the reaction vessels from the sandbath and spraying t n e m Vvth l i q u i d carbon dioxide. By yarying the pestilence tinges. at each of the experimental temperatures, a matrix 6f jirp^jjct yi>fd£ and prpper^jiej: iyersus i residence time and temperature wis

Elemental analyses an0 simulated d i s t i l l a t i o n s were performed on the '.liquf.cLoil. collected .-in . theory ;|ce trajpv The'resjdual solid \n tfig feaction vessels„. was" ex^ra^tetj wi-tjv;,tgH*epe tp /remove 'any remaiaJo| bitumen. Tolueiie;insoluble organic material was assumed to b'e''

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