Slag Quench Water

Slag/Water Slurry

FIGURE 5-35. Schematic diagram of the E-Gas gasifier. (From Ratafia-Brown, J. et al., Major Environmental Aspects of Gasification-Based Power Generation Technologies, Office of Fossil Energy, U.S. Department of Energy, Washington, D.C., December 2002.)

liquefaction, and direct liquefaction. In pyrolysis processes, the liquids are a by-product of coke production. The term liquefaction refers to the conversion of the coal to a product that is primarily a liquid. In indirect liquefaction, the coal is gasified into a mixture of carbon monoxide and hydrogen (i.e., syngas), which was discussed earlier. The syngas is then processed into liquid products using Fischer-Tropsch synthesis. In direct liquefaction, also referred to as coal hydrogenation, coal is mixed with a hydrogen-donor solvent and reacted with hydrogen or syngas under elevated pressures and temperatures to produce a liquid fuel. Indirect liquefaction is used quite extensively throughout the world, as illustrated in Table 5-8, while direct liquefaction has not been able to compete with other liquid or gaseous fuels. Liquefaction processes are technically feasible; Germany and South Africa—countries with abundant coal supplies but little or no petroleum resources—have demonstrated that a country can meet much of its liquid fuel needs through liquefaction. Germany did so during World War II, while South Africa became self-reliant during its years of apartheid which made it susceptible to oil embargoes. This section provides a brief history of the development



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