Toscoal Process

Production of Liquids from As-Mined Wyodak Coal by the Toscoal Process 

Source Carlson, F.B. et al., Preprints. Symposium on Clean Fuels from Coal II, Institute of Gas Technology, Chicago, IL, 1975, p. 504. 

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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. 

Properties. Results for the operation using subbituminous coal from the Wyodad mine near Gillette, Wyoming, are shown in Table 13. Char yields decreased with increasing temperature, and oil yields increased. The Fischer assay laboratory method closely approximated the yields and product assays that were obtained with the TOSCOAL process. 

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

One process that was developed but not commercialized was the TOSCOAL process, in which crushed coal is fed to a horizontal rotating kiln. There it is heated by hot ceramic balls to between 425 and 540°C. The hydrocarbons, water vapor, and gases are drawn off, and the char is separated from the ceramic balls in a revolving drum with holes in it. The ceramic balls are reheated in a separate furnace by burning some of the product gas. 

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. 

Pyrolysis conditions determine the extent to which the coal is carbonized and the nature of the liquid and gaseous products. Coal pyrolysis processes are generally classified as low temperature (<700°C), medium temperature (700-900°C), or high temperature (>900°C). A number of reviews on advanced pyrolysis processes are available.30-31 Two highly developed pyrolysis processes were the COED process, developed by FMC Corporation, which used a series of fluidized beds operating at successively higher temperatures, and the TOSCOAL process, which used a horizontal rotating kiln. 

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. 

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. 

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