Coal gasification is defined as a process, in which coal is converted to gaseous products. When coal is fed into a gasification reactor and heated up, it mainly undergoes pyrolysis reactions in which gases, volatile tar components and char are formed (see Fig. B.3). Coal gasification is generally done with oxygen of 95% purity, at high temperatures and elevated pressures. It is used for the production of hydrogen or hydrogen-rich gas products. Gasification reactions are:
Basically, all types of coal can be gasified to produce hydrogen, although certain limitations associated with the gasification process or the characteristics of the coal have to be respected. The coal gasification process is complicated because of the need of handling solids including transport, size reduction and removing large amounts of ash. The handling operations for solids significantly affect the cost of hydrogen production.
Figure B.3 Process flow sheet for hydrogen production from coal gasification 
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