A flexible CO2 capture system for backup power plants using Ca(OH)2/CaCO3 solid storage

Abstract

CO2 capture technologies are required to address intermittent sources of CO2, such as the natural gas combined cycle (NGCC) used for backup power applications. The high reactivity of Ca(OH)2 powder facilitates the design of low cost carbonators to capture diluted CO2 (typically below 4%v in NGCC flue gases) as CaCO3. By storing CaCO3 and Ca(OH)2 it is possible to decouple the CO2 capture step in the carbonator from the oxy-calciner/hydrator block in which Ca(OH)2 is regenerated and CO2 extracted. This facilitates the integration of CO2 capture elements in backup power systems. Simulations of the completely integrated backup power plant with and without capture indicated that for a NGCC capacity factor (CF) of 0.1, the thermal capacity of the oxy-calciner was just 2% of the gross power output of the NGCC gas turbine. Capture efficiencies of 90% can be reached without modifying the operating conditions of the gas power plant, while achieving a global efficiency of 38% for the system with CO2 capture. A basic economic analysis indicated that the proposed scheme would lead to a cost of CO2 avoided of approximately 200 $ per tCO2, making it suitable for retrofitting natural gas-based power plants.