Integration of Carbonate CO₂Capture Cycle and Coal-Fired Power Plants. A Comparative Study for Different Sorbents

Abstract

Lately, an outstanding research interest for CO2 capture sorption/desorption looping systems is the improvement of sorbents reactivity and durability. In particular, in calcium-looping cycles the control of sintering processes in the sorbent by thermal pretreatments, doped limestone, or dolomite have deserved excellent works and have shown good experimental results. Also, synthetic sorbents have been tested and demonstrate a lasting capture capacity. Nevertheless, in most cases this long-term conversion enhancement increases the cost of the sorbent and, thus, the system operation and CO2 capture cost. Therefore, any comparison among sorbents will be accurate if both chemical and economical considerations are taken into account in the assessment. In this work, a common basis for sorbent comparison is presented. The integration of the sorbent cost and its chemical and mechanical performance have been studied for different options. The energetic and economical characteristics of several high temperature sorbents have been checked in a CO2 looping cycle applied to an existing coal-fired electrical generation power plant. The aim is to compare the cost of avoided CO2 as a function of average conversion of solid population and cost for different sorbents. Despite excellent conversion results, the unit cost of the sorbent is crucial to maintain the CO2 looping concept as economically attractive. High cost sorbents, even if their residual activity remains at a high level, will be preferred to operate in systems fed with inert-free fuels, that is, natural gas, instead of applications operating with coal. Both their low cost and long-term performance make thermally pretreated limestones competitive sorbents for carbonation/calcination cycles.