Natural Gas Fired Combined Cycles With Low CO2 Emissions

Abstract

This paper assesses performances and economic viability of CO2 removal by chemical absorption from the flue gases of natural gas-fired Combined Cycles, more specifically for two configurations: one where CO2 is removed ahead of the stack without modifying the power cycle; the other where part of the flue gases is recirculated to the gas turbine, thereby reducing the flow to be treated by chemical absorption. In both cases sequestered CO2 is made available at conditions suitable to storage into deep oceanic waters. Performances and cost of electricity are evaluated for systems based on large, heavy-duty turbines representative of state-of-the-art “FA” technology. Carbon sequestration reduces net plant efficiency and power output by about 10 percent and increases the cost of electricity from 36 to about 50 mills/kWh. Flue gas recirculation warrants slightly higher efficiencies and lower costs. CO2 removal is eventually compared with other strategies for the reduction of CO2 emissions, like switching existing coal-fired steam plants to natural gas or replacing existing steam plants with conventional CCs. At current fuel prices the latter appears the option of choice, with a cost of about $25 per tonn of avoided CO2 emission. [S0742-4795(00)02803-9]