Question

In modern integrated gasification combined cycle (IGCC) coal-fed power plants, oxygen is produced via cryogenic separation of air and is fed to the IGCC plant along with coal. The separation of oxygen from air is expensive; what reason(s) can you give for doing this?

Answer 1

IGCC

 

In modern IGCC plants, coal is partially oxidized (gasified) to produce synthesis gas CO + H2 and other compounds. Prior to combusting the synthesis gas in a turbine, it must be “cleaned” or H2S and CO2 (if carbon capture is to be employed.) Both H2S and CO2 are acid gases that are removed by one of a variety of physical or chemical absorption schemes. By removing nitrogen from the air, the raw synthesis gas stream is much smaller making the acid gas removal much easier. In fact, when CO2 removal is required IGCC is the preferred technology, i.e. the cheapest.