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

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.