Reactor Types and Processes

Some mention must also be made here of the reactor types that have been used for coal gasification processes. 

Reactors may also be designed to operate either at atmospheric pressure or at high pressure. In the latter type of operation, the hydrogasification process is optimized and the quality of the product gas (in terms of heat, or Btu, content) is improved. In addition, the reactor size may be reduced and the need to pressurize the gas before it is introduced into a pipeline is eliminated (if a high-heat-content gas is to be the ultimate product). However, high-pressure systems may have problems associated with the introduction of the coal into the reactor. 

FIGURE 20.4 General chemistry of the various gasification systems. 

FIGURE 20.6 Countercurrent descending-bed reactor (From Meyers, R.A., Ed., Coal Handbook, Marcel Dekker Inc., New York, 1981). 

As the coal descends, it is reacted first by devolatilization using the sensible heat from the rising gas, then hydrogenated by the hydrogen in the reactant gas, and finally burned to an ash. The reactions are, therefore, carried out in a countercurrent fashion. 

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