Reducing water usage with rotary regenerative gas/gas heat exchangers in natural gas-fired power plants with post-combustion carbon capture

It is possible to greatly mitigate the increase of water usage associated with the addition of carbon capture to fossil fuel power generation. This article presents a first-of-a-kind feasibility study of a series of technology options with rotary regenerative gas/gas heat exchangers for the management of the water balance around post-combustion carbon capture process integrated with CCGT (Combined Cycle Gas Turbine) plants with and without EGR (exhaust gas recirculation). Hybrid cooling configurations with a gas/gas heat exchanger upstream of the direct contact cooler reduce cooling and process water demand by 67% and 35% respectively compared to a wet system where the flue gas is primarily cooled prior to the absorber in larger direct contact coolers. The CO2-depleted gas stream is then reheated above 70 °C with enough buoyancy to rise through the stack. Dry air-cooled configurations, relying on ambient air as the cooling medium, eliminate the use of process and cooling water prior to the absorber and the temperature of the flue gas entering the absorber is unchanged. Rotary regenerative heat exchangers do not introduce significant additional pressure drop and gas leakage from a high CO2 concentration stream to a stream with lower concentration can be minimized to acceptable levels with available strategies using a purge and a scavenging slipstream from the higher pressure flow.