Conversion processes gasification

Coal can be converted to gas by several routes (2,6—11), but often a particular process is a combination of options chosen on the basis of the product desired, ie, low, medium, or high heat-value gas. In a very general sense, coal gas is the term appHed to the mixture of gaseous constituents that are produced during the thermal decomposition of coal at temperatures in excess of 500°C (>930°F), often in the absence of oxygen (air) (see Coal CONVERSION PROCESSES, gasification) (3). A soHd residue (coke, char), tars, and other Hquids are also produced in the process ... 

In this process, any sulfur present in the coal exits the gasifier as hydrogen sulfide which is removed by various processes such as a Hohnes-Stretford unit where the sulfide is absorbed and regenerated. The resulting sulfur is filtered out as a cake (39 wt %) which is sold as a valuable feedstock (see Coal CONVERSION PROCESSES, GASIFICATION SULFURREMOVAL AND RECOVERY). 

Gasification. Gasification converts soHd fuel, tars, and oils to gaseous products such as CO, H2, and CH that can be burned direcdy or used in synthesis gas (syngas) mixtures, ie, CO and mixtures for production of Hquid fuels and other chemicals (47,48) (see Coal conversion processes, gasification Euels, synthetic-gaseous fuel Hydrogen). 

Partial oxidation of heavy Hquid hydrocarbons requires somewhat simpler environmental controls. The principal source of particulates is carbon, or soot, formed by the high temperature of the oxidation step. The soot is scmbbed from the raw synthesis gas and either recycled back to the gasifier, or recovered as soHd peUitized fuel. Sulfur and condensate treatment is similar in principle to that required for coal gasification, although the amounts of potential poUutants generated is usually less (see Coal conversion processes, gasification). 

Sasol Fischer-Tropsch Process. 1-Propanol is one of the products from Sasol s Fischer-Tropsch process (7). Coal (qv) is gasified ia Lurgi reactors to produce synthesis gas (H2/CO). After separation from gas Hquids and purification, the synthesis gas is fed iato the Sasol Synthol plant where it is entrained with a powdered iron-based catalyst within the fluid-bed reactors. The exothermic Fischer-Tropsch reaction produces a mixture of hydrocarbons (qv) and oxygenates. The condensation products from the process consist of hydrocarbon Hquids and an aqueous stream that contains a mixture of ketones (qv) and alcohols. The ketones and alcohols are recovered and most of the alcohols are used for the blending of high octane gasoline. Some of the alcohol streams are further purified by distillation to yield pure 1-propanol and ethanol ia a multiunit plant, which has a total capacity of 25,000-30,000 t/yr (see Coal conversion processes, gasification). 

Gasification. Gasification of coal is used to provide gaseous fuels by surface and underground appHcations, Hquid fuels by indirect Hquefaction, ie, catalytic conversion of synthesis gas, and chemicals from conversion of synthesis gas. There are also appHcations in steelmaking (see Coal conversion PROCESSES, gasification). 

See Coal CONVERSION PROCESSES, gasification Fuels, synthetic. 

Gases - [AIRPOLLUTION CONTROLMETHODS] (Vol 1) - [COAL CONVERSION PROCESSES - GASIFICATION] (Void) -m air pollution models [ATMOSPITERIC MODELING] (Vol 3) -analysis by multiphoton ionization [SPECTROSCOPY, OPTICAL] (Vol 22) -as lubricants [LUBRICATION AND LUBRICANTS] (Vol 15) -sampling of [SAMPLING] (Vol 21) -sterile filtration [MICROBIAL AND VIRAL FILTRATION] (Supplement)... 

L. J. Shadle, D. A. Berry, and M. Syamlal, Coal conversion processes, gasification, Kirk-Othmer Encyclopedia of Chemical Technology, 5th Ed., John Wiley Sons, 2001. 

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