Fu C., Gundersen T., 2012, Integrating the Compression Heat in Oxy-combustion Power Plants with CO2 Capture, Chemical Engineering Transactions, 29, 781-786.
Oxy-combustion is a competitive technology to enable the capture of CO2 from fossil fuel based power plants. Cryogenic air separation is the only commercially available technology for large volume O2 production that can be applied for oxy-combustion plants. The considerable energy consumption in the air separation units is the main challenge to implement oxy-combustion technology. The compression heat in the air compression process is generally removed by cooling water. The water coolers are responsible for 17.6 % of the total exergy losses in an air separation unit. This paper investigates the possibilities of integrating the compression heat from the air separation unit with the steam cycle. The compression process of the air is studied in two cases: adiabatic (one-stage) compression and three-stage compression with interstage cooling. A decomposed methodology has been developed for studying the heat balance in the boiler feedwater heaters in the steam cycle. The Grand Composite Curve is applied to determine the heat demand and thus the amount of steam extraction. For a coal based oxy-combustion power plant with a gross power output of 792 MW, the thermal efficiency increases with 0.47 % points (net power increases by 8.8 MW) by heat integration in the adiabatic compression case.
