TOSCO process

Two indirectly heated oil shale retorting technologies employing solid-to-solid heat transfer have been described in connection with coal pyrolysis. They are the TOSCOAL process, called the TOSCO process when used with oil shale, and the Lurgi-Ruhrgas process. The former process was fully developed before operations were terminated, and the latter has been commercialized in connection with coal devolatilization and hydrocarbon pyrolysis. 

Lenhart, A. F., The TOSCO Process-Economic Sensitivity to the Variables... 

The TOSCO-II process is capital intensive because it requires a large volume of heating gases and mechanically complex equipment the PARAHO and Union processes are also capital intensive because they have long residence time requirements that entail massive hardware. The PARAHO and Union processes are, however, heat efficient as a result of countercurrent shale and gas flow. But the TOSCO process, although having some degree of heat recovery, uses heat relatively inefficiently. 

In the Toscoal process (Carlson et al 1973,1975 Cartez andDaDelfa, 1981) (Figure 19.5), crushed coal is charged to a rotating drum which contains preheated ceramic balls whereupon the coal is decomposed to produce the usual liquid product, char, and gas (Table 19.2) The process is analogous to the Tosco process for producing overhead oil from oil shale with the added note that the char replaces the spent shale. 

The TOSCOAL Process. The Oil Shale Corp. (TOSCO) piloted the low temperature carbonization of Wyoming subbituminous coals over a two-year period in its 23 t/d pilot plant at Rocky Falls, Colorado (149). The principal objective was the upgrading of the heating value in order to reduce transportation costs on a heating value basis. Hence, the soHd char product from the process represented 50 wt % of the starting coal but had 80% of its heating value. 

F. B. Carlson, L. H. Yardumian, and M. T. Atwood, "The TOSCO AT, Process for Low Temperature Pyrolysis of Coal," paper presented at... 

B. L. SchuJman and P. A. White, "Pyrolysis of Scrap Tires Using the Tosco-11 Process— Progress Report," ACS Symposium Series No. 76, American Chemical Society, Washington, D.C., 1978. 

Other large-scale coal pyrolysis process developments were carried out by the Tosco Corp., with its TOSCO AT, process (36). Essentially a direct copy of Tosco s rotating kiln technology that was developed for pyrolysis of oil shale, this slow heating scheme achieved tar yields at maximum temperatures of 482—521°C that were essentially identical to those obtained by a Eischer assay. 

TOSCOAL [The Oil Shale Corporation] A low-temperature carbonization process for producing liquid fuels from oil shales. Developed by the Oil Shale Corporation in the 1960s. See TOSCO II. 

The process considered is the Colony hydrotreated shale oil plant using the TOSCO II pyrolysis retort (4). In this process raw shale, crushed to 1/2" or smaller, is contacted with hot ceramic balls in a rotating drum. Downstream of the retort the balls and spent shale are separated by screening. The balls are then transported by an elevator to a vessel in which they are reheated by direct contact with hot combustion gases. The heated balls are then recycled to the rotating retort. 

Schulman, B.L., P.A. White. Pyrolysis of Scrap Tires Using the Tosco II Process. American Chemical Society 0-8418-0434 9/78/47-076-274. September, 1978. 

BERNARD SHULMAN, Director of Research Development, Tosco Corporation In Bob Epperly s talk on the Donor Solvent process,... 

Whitcombe, J. A. Vawter, R. Glenn. The TOSCO-II Oil Shale Process, ... 

Nothing has been said of the spent shale SS-2 which was produced from the TOSCO II pilot plant. This is because it is diflBcult to say how representative the 50 lb of OS-1 is of the 100 tons of —1/2 in. mesh feedstock. TOSCO determined that the 100 tons assayed at 37-38 gal/ton of oil. The Fischer assays performed in this study yield a value of 39.8 gal/ton (16). The difference in oil yields is outside of analytical uncertainties (16). If OS-1 can be considered representative of the pilot plant feedstock, then the abundances of trace elements in SS-2 compared with those in OS-1 would give ER values greater than unity for all trace elements. The elements fiuorine and zinc in SS-2 have ER values of 1.05 and 1.17, respectively. Based on these results, it appears that the trace elements for which data are reported here are not mobilized during the TOSCO II process. 

Characterization of the typical full range liquids reveals oxygen concentrations of 1.9 wt % in the H-Coal liquid and 0.9 wt % in the TOSCO shale liquid. Processing problems are expected with nitrogen removal because greater than 70% of the nitrogen compounds are basic... 

The Fischer assay is a standardized laboratory test in which an oil shale sample is retorted at 500°C to determine its oil yield. It provides a measure of the grade of oil shale being processed. Commercial processes such as The Oil Shale Corporation s TOSCO II process give oil recoveries (synthetic crude or syncrude) of up to 100% of the Fischer assay. Oil and gas formation from... 

FIGURE 17.7 Diagram of the components of The Oil Shale Corporation s TOSCO II process for the retorting of mined oil shale for the production of synthetic crude. [From Hall and Yardumian [55], courtesy L. Yardumian.)... 

R.N. Hall and L.H. Yardumian, The Economics of Commercial Shale Production by the Tosco II Process, 61st Annu. Meet., Am. Inst. Chem. Eng. Los Angeles, 1968 (unpublished). 

In this work, we report kinetics for the thermal cracking of shale oil over shale. The data are most appropriate for thermal cracking inside large blocks during in-situ processing and in the TOSCO-II and Lurgi processes, where relatively low temperatures... 

---