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.

Thermodynamic Simulation of CO2 Capture for an IGCC Power Plant using the Calcium Looping Cycle

“…They found that the carbonation conversions of two kinds of the natural limestones retained 0.23 and 0.11, respectively, after 60 cycles. The carbonation conversion of the modified limestone in the experiments discussed in this paper achieves 0.41 after 100 cycles, which is greater than those of the natural limestones during long-term cycles reported in literature [33]. In order to calculate the average carbonation conversion, the cyclic carbonation conversions of sorbents need to be summarized by mathematical equations.…”

“…The repetition tests demonstrate that both the natural and the modified limestones retain stable carbonation conversions after about 60 cycles, and the conversion of the latter is more than two times higher than that of the former. Lisbona et al [33] also investigated the different natural limestones. They found that the carbonation conversions of two kinds of the natural limestones retained 0.23 and 0.11, respectively, after 60 cycles.…”

Integration of a Ca looping system for CO2 capture in existing power plants

“…The use of more expensive synthetic sorbents reduce the optimum purged material well below 1%. 27 In this case, the amount of inert material in the Ca looping system (ash and deactivated sorbent) would dramatically increase the energy requirements in the calciner when introducing coal to drive sorbent calcination.…”

Use of steel slag for CO2 capture under realistic calcium-looping conditions

“…[22][23][24][25] In addition, several integration schemes have been proposed to further reduce the energy demand and minimize the penalty on global efficiency at still high capture efficiency. [26][27][28][29][30] On the other hand, lab-scale experiments demonstrate that limestone-derived CaO (lime) suffers a severe sintering at CaL conditions for CO 2 capture, which leads to a drastic drop of the CaO surface available for fast reaction-controlled carbonation in just a few cycles.…”