Chemical looping combustion

Chemical looping combustion (CLC) is a technological process typically employing a dual fluidized bed system (circulating fluidized bed process) where a metal oxide is employed as a bed material providing the oxygen for combustion in the fuel reactor. The reduced metal is then transferred to the second bed (air reactor) and re-oxidized before being reintroduced back to the fuel reactor completing the loop.

Isolation of the fuel from air simplifies the number of chemical reactions in combustion. Employing oxygen without nitrogen and the trace gases found in air eliminates the primary source for the formation of nitrogen oxide (NO
x), producing a flue gas composed primarily of carbon dioxide and water vapor; other trace pollutants depend on the fuel selected.

Chemical looping combustion (CLC) uses two or more reactions to perform the oxidation of hydrocarbon based fuels. In its simplest form, an oxygen carrying species (normally a metal) is first oxidised in air forming an oxide. This oxide is then reduced using a hydrocarbon as reducer in a second reaction. As an example, a nickel based system burning pure carbon would involve the two redox reactions:

2Ni(s) + O
2(g) → 2NiO(s)

 

 

 

 

C(s) + 2NiO(s) → CO
2(g) + 2Ni(s)

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