The chemical reactions of gasification can progress to different extents depending on the gasification conditions like temperature and pressure and the feedstock used.
Combustion reactions take place in a gasification process, but, in comparison with conventional combustion which uses a stoichiometric excess of oxidant, gasification typically uses one-fifth to one-third of the theoretical oxidant. This only partially oxidizes the carbon feedstock.
As a "partial oxidation" process, the major combustible products of gasification are carbon monoxide CO and hydrogen, with only a minor portion of the carbon completely oxidized to carbon dioxide CO 2. The heat produced by the partial oxidation provides most of the energy required to drive the endothermic gasification reactions.
Within a gasification process, the major chemical reactions are those involving carbon, CO, CO 2 , hydrogen H 2 , water steam and methane CH 4 , as follows:. With the above, the combustion reactions are essentially carried out to completion under normal gasification operating conditions.
Nitrogen chemically bound in the feed generally converts to gaseous nitrogen N 2 , with some ammonia NH 3 , and a small amount forming hydrogen cyanide HCN. Chlorine is primary converted to hydrogen chloride HCl.
Production of dihydrogen,water gas, coal gasification,water-gas shift reaction
Detailed Gasification Chemistry. Within a gasification process, the major chemical reactions are those involving carbon, CO, CO 2 , hydrogen H 2 , water steam and methane CH 4 , as follows: The combustion reactions: 1. The table summarizes the main transformations of solid fuel constituents to gaseous species in both gasification and combustion.
This shows clearly the marked differences between gasification resulting in syngas and combustion resulting in exhaust gas.