Coal-to-oil process

Fig. 19.24. Block flow diagram of Sasol s coal-to-oil process. (Reprinted from Encyclopedia of Chemical Processing Design, pp. 310, 320, by courtesy of Marcel Dekker, Inc., 1979.)...

SASOL in South Africa developed its F-T coal-to-oil process after World War 11. Its Sasolburg plant began liquid fiiel production in 1955, a second plant at Segunda (SASOL Two) opened in 1980, and a third plant SASOL Three in 1982. By 2001 SASOL was providing 29 percent of South Africa s motor fuel requirements, both gasoline and diesel, as well as industrial chemicals. 

Liquefaction. Liquefaction of coal to oil was first accompHshed in 1914. Hydrogen was placed with a paste of coal, heavy oil, and a small amount of iron oxide catalyst at 450° and 20 MPa (200 atm) in stirred autoclaves. This process was developed by the I. G. Earbenindustrie AG to give commercial quaUty gasoline as the principal product. Twelve hydrogenation plants were operated during World War II to make Hquid fuels (see CoAL... 

The investments shown are estimated for an urban midcontinent location. As mentioned above, the estimate for the boiler plant is based on coal-fired burners with attendant stack gas sulfur dioxide (SC ) removal facilities. As indicated on Table XX, no allowance is made for (a) coal resource costs, (b) coal mining or handling, (c) conversion of coal to oil by SRC-II process, (d) SRC-II oil transportation to, or (e) refined product distribution and transportation from the refinery. These additional costs are not required to evaluate refinery processing costs. However, they should be included if it is desired to determine the overall economics of a specific synthetic crude oil refining project. 

The same catalyst was used at the United States Bureau of Mines Coal to Oil Demonstration Plant, Louisiana, Missouri, for the process-... 

While many studies indicate that pyrrhotites are probably involved in the liquefaction process, the exact mechanism by which pyrrhotite catalyzes the conversion of coal to oil is not clear. Based on the works of Thomas et al. (1 ) and Derbyshire et al., (13) one can suggest that a possible role of pyrrhotite is as a hydrogenation catalyst. However, more work is necessary on the surface properties of the pyrrhotites and the interaction with model compounds before a definite catalytic mechanism can be proposed. 

At the end of World War II, widespread fear of petroleum shortages led to the authorization of the U.S. Bureau of Mines to initiate a large research and development program on fossil fuel-to-oil processes. A laboratory was established at Bruceton, Pa., under the direction of the late Henry H. Storch (1). Dr. Storch was an authority on catalysis and coal and an outstanding research administrator. This chapter is dedicated to his memory. 

Cited from Forbes and O Beirne, op. cit. (25), p. 456. Royal Dutch/Shell, in common with ICI and Standard Oil of New Jersey, also became closely involved with I.G. Farben in negotiations over high pressure processes for coal to oil conversion. This and other aspects of high pressure industrial chemistry during the interwar period are reviewed in Anthony S. Travis, The High Pressure Chemists (Wembley Brent Schools Industry Project, 1984). 

The overall coal to oil conversion occurs in three stages (1) mining of coal, (2) preparation of synthesis gas, and (3) the Fischer-Tropsch synthesis along with downstream processing. According to Dry (1990), the second and third stages contribute 23 and 30% of the total capital investment, respectively. 

The optimum yield of liquid product is obtained in the coal-to-liquids process at approximately 1075 F. A typical product distribution for coal-to-liquida processing using this coal is 56% char, 35% tar, 7% gas, and 2% water. The residence time for this process is also kept as short as possible which maximizes the yield and prevents further cracking of the liquid product. The effect of flash pyrolysis on the liquid yield is shown by the fact that the tar and light oil yield for this coal from... 

Coal and Coke Gasification, An important process for the gasification of coal and coke is the Lurgi process, used in South Africa at the coal to oil plant and also used in Europe. This process requires the use of coke or a noncaking coal and oxygen the product gas usually is high in methane. The reaction... 

Produced from Co l. Estimates of the cost of producing methanol from coal have been made by the U.S. Department of Energy (DOE) (12,17) and they are more uncertain than those using natural gas. Experience in coal-to-methanol faciUties of the type and size that would offer the most competitive product is limited. The projected costs of coal-derived methanol are considerably higher than those of methanol produced from natural gas. The cost of the production faciUty accounts for most of the increase (11). Coal-derived methanol is not expected to compete with gasoline unless oil prices exceed 0.31/L ( 50/bbl). Successful development of lower cost entrained gasification technologies could reduce the cost so as to make coal-derived methanol competitive at oil prices as low as 0.25/L ( 40/bbl) (17) (see Coal conversion processes). 

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