Integration of a Ca-looping system for CO2 capture in an existing power plant

This work analyses a Ca-looping system that uses CaO as regenerable sorbent to capture CO2 from the flue gases generated in an existing supercritical power plant. The CO2 is captured by CaO in a CFB carbonator while coal oxycombustion provides the energy required to regenerate the sorbent. Part of the energy introduced into the calciner can be transferred to a new supercritical steam cycle to generate additional power. Two case studies based on a scenario of low solid circulation rate between reactors have been integrated with the new supercritical steam cycle. Efficiency penalties, mainly associated with the energy consumption of the ASU, CO2 compressor and auxiliaries, can be as low as 7.5 percentage points of net efficiency when working with low CaCO3 make-up flows and integrating the Ca-looping with a cement plant that makes use of the solid purge. 70 % of the CO2 generated in the existing plant is captured under these conditions, with an overall CO2 capture in the process over 86 %. Different scenarios with high circulation rates between reactors could be also proposed to achieve a determined CO2 capture efficiency. In this case the optimal thermal integration for the new scenarios should be evaluated as the energy availability in the process streams and the consumptions of the main equipments in the process would be different. (C) 2011 Published by Elsevier Ltd.