Gasifier reactor design

The last two reactions are usually performed simultaneously. The second reaction supplies then the heat necessary for the first, strongly endothermic reaction. There are very interesting catalytic problems in coal gasification, as well as challenging engineering problems in the gasifier-reactor design. 

Cyclonic filters (and closely related designs such as U-tubes) are employed as an initial gas cleanup step in most gasifier systems because they are effective and relatively inexpensive to operate. In circulating fluidized-bed or entrained-bed gasifiers, cyclones are an integral part of the reactor design, providing for separation of the bed material and other particulates from the gas stream. 

There are three fundamental reactor types (1) a gasifier reactor, (2) a devolatilizer, and (3) a hydrogasifier (Figure 20.4) with the choice of a particular design depending on the ultimate product gas desired. 

The heat required for gasification is essentially supplied by the partial oxidation of the coal. Overall, the gasification reactions are exothermic, so waste heat boilers often are used at the gasifier effluent. The temperature, and therefore composition, of the product gas is dependent upon the amount of oxidant and steam, as well as the design of the reactor that each gasification process utilizes. 

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