Solid Sorbent Post-Combustion CO2 Capture in Subcritical PC Power Plant

Abstract

Existing coal fired power plants are expected to continue providing a significant portion of power generation and a majority of these are subcritical pulverized coal (PC) units which have higher CO2 emissions on a MWe basis due to their higher heat rates, while CO2 emissions are an increasing concern due to global pressure on limiting greenhouse gas accumulation in the atmosphere. Current state-of-the-art CO2 capture technology uses an aqueous amine solution to chemically absorb the CO2 from the flue gas and thus requires a large amount of energy for solvent regeneration. Novel solid sorbent based CO2 capture technologies are under development to capture the CO2 via physical adsorption and desorption, thereby consuming far less energy for the sorbent regeneration process. This present work is focused on retrofitting a subcritical PC power plant with solid sorbent post combustion CO2 capture technology. Thermal performance and costs are compared with an amine based CO2 capture plant as well as the plant with no CO2 capture. The design of the solid sorbent based CO2 capture system is optimized for integration to minimize plant modifications and the associated downtime. In an existing PC plant with a net power efficiency of 36.57%, use of the amine based capture reduces the net efficiency to 26.01% while with the solid sorbent based capture, the reduction in net efficiency is far less at 28.67% when 90% of the CO2 is captured. As a consequence, the increase in plant cooling duty is significantly lower for the solid sorbent CO2 capture case, with the water usage on a per MW basis being almost 17% lower than the amine based PC plant. The calculated levelized cost of electricity is increased from $60.5/MWh without CO2 capture to $124.3/MWh for amine based capture while that with the solid sorbent based capture is much lower at $115.8/MWh.