IGCC ASU improvement- cryogenic pump +htr+turbine

[davefitz]

Regarding IGCC configurations, there appears to be a simple improvement to the process of cyrogenic air seperation that is not being pursued.

In the normal cryogenic cold box, the gaseous cryogens are transferred to outside process by passing thru heat exchangers ( which are also cooling the inlet compressed air stream).

A method which can be used to generate power ( to offset the compressor power) would be to instead extract liquid cryogen, compress it to 100 bar using a cryogenic pump ( above critical pressures), then heat the supercritical liquid and expnad it across a turbine. First it would be heated to near ambient by passing thru a modified heat exchanger ( suitable for 100 bar pressure) then further superheates using process steam ( or cooling compressor discharge air)to 500 F, then passing thru a turbine . The microturbines would be automatically synched to the grid using solid state devices ( as currently used in distributed generation microturbines).

My calcs show that if both the oxygen and nitrogen streams are used as a working fluid in this manner, then the compressor power can be completely offset ( asssumes the compressor and turbines are 85% efficient).

 

[bobster2003]

The efficiency of cryo air plants is to maximise the use of all available "cold" energy. You would not be able to simply remove the cryogenic liqud without upsetting the separation process. You would need to look at the overall process energy envelope and not separate it from the cryogenic process.

Also pure oxygen at 100bar would be quite dangerous. Have you looked at the risk involved?