Chemical looping combustion

Chemical looping combustion (CLC) is a technological process typically employing a dual fluidized bed system.

[4] The gain in efficiency is possible due to the enhanced reversibility of the two redox reactions; in traditional single stage combustion, the release of a fuel's energy occurs in a highly irreversible manner - departing considerably from equilibrium.

[5] Some additional heat exchange with the environment is required to satisfy the second law; theoretically, for a reversible process, the heat exchange is related to the standard state entropy change, ΔSo, of the primary hydrocarbon oxidation reaction as follows: However, for most hydrocarbons, ΔSo is a small value and, as a result, an engine of high overall efficiency is theoretically possible.

[6] Although proposed as a means of increasing efficiency, in recent years, interest has been shown in CLC as a carbon capture technique.

This gives CLC clear benefits when compared with competing carbon capture technologies, as the latter generally involve a significant energy penalty associated with either post combustion scrubbing systems or the work input required for air separation plants.

[11][12] A continuous 200-hour demonstration results of a 25 kWth CDCL sub-pilot unit indicated nearly 100% coal conversion to CO2 with no carbon carryover to the air reactor.

[21] This is helpful for achieving high gas conversion, and especially when using solid fuels, where slow steam gasification of char can be avoided.

CLOU operation with solid fuels shows high performance[22][23] Chemical Looping can also be used to produce hydrogen in Chemical-Looping Reforming (CLR) processes.

[7][27][28] In summary, CLC can achieve both an increase in power station efficiency simultaneously with low energy penalty carbon capture.