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The effects of the sorption and the regeneration temperatures on the performance of a novel rapid thermal swing chemisorption (RTSC) process (Lee and Sircar in AIChE J. 54:2293–2302, ) for removal and recovery of CO2 from an industrial flue gas without pre-compression, pre-drying, or pre-cooling of the gas were mathematically simulated. The process directly produced a nearly pure, compressed CO2 by-product stream which will facilitate its subsequent sequestration. Na2O promoted alumina was used as the CO2 selective chemisorbent, and the preferred temperatures were found to be, respectively, 150 and 450 °C for the sorption and regeneration steps of the process. The specific cyclic CO2 production capacity of the process and the pressure of the by-product CO2 gas were substantially increased over those previously achieved by using the sorption and regeneration temperature of, respectively, 200 and 500 °C (Lee and Sircar in AIChE J. 54:2293–2302, ). The net compressed CO2 recovery from the flue gas (∼92%) did not change. However, substantially different amounts of high and low pressure steam purges were necessary for comparable degree of desorption of CO2. A first pass estimation of the capital and the operating costs of the RTSC process was carried out for a relatively moderate size application (flue gas clean up and CO2 recovery from a ∼80 MW coal fired power plant). Both costs were substantially lower than those for a conventional absorption process using MEA as the CO2 solvent (Desideri and Paolucci in Energy Convers. Manag. 40:1899–1915, ). [ABSTRACT FROM AUTHOR]

Abstract: Sorption enhanced water gas shift (SEWGS) reaction is a process concept, which simultaneously carries out the gas phase water gas shift (WGS) reaction (CO+H2O↔CO2+H2) and selective chemisorption of the byproduct CO2 from the gas phase reaction zone for direct production of essentially pure H2 in a single unit operation. A packed bed sorber-reactor containing an admixture of a WGS catalyst and a CO2 chermisorbent is used in the process. The concept circumvents the thermodynamic limitation of the WGS reaction and enhances the rate of reaction for H2 production. In this study, the SEWGS reaction concept was successfully demonstrated by both experiment and numerical simulation using K2CO3-promoted hydrotalcite as the CO2 sorbent. Numerical model simulations were also carried out to investigate the effects of various operating conditions of SEWGS reaction on the process performance. In general, higher H2O/CO feed ratio, higher fraction of sorbent (chemisorbent ratio in the sorber-reactor), and lower operating temperature favor both H2 productivity and CO conversion. Higher reaction pressure increases H2 productivity but decreases CO conversion. [Copyright &y& Elsevier]

Abstract: The performance of a novel thermal swing sorption-enhanced reaction (TSSER) concept for simultaneous production of fuel-cell grade hydrogen and compressed carbon dioxide as a by-product from a synthesis gas feed is simulated using Na2O promoted alumina as a CO2 chemisorbent in the process. The process simultaneously carries out the water gas shift (WGS) reaction and removal of CO2 from the reaction zone by chemisorption in a single unit. Periodic regeneration of the chemisorbent is achieved by using the principles of thermal swing adsorption employing super-heated steam purge. Recently measured equilibrium and kinetic data for chemisorption and desorption of CO2 on the promoted alumina using conventional column dynamic tests as well as new experimental data demonstrating the concept of sorption-enhanced WGS reaction using the material are reviewed. The simulated performance of the TSSER process employing this material as a chemisorbent is compared with the process performance using K2CO3 promoted hydrotalcite as the chemisorbent. The promoted alumina exhibited (i) ∼15% lower H2 productivity at a slightly reduced CO to H2 conversion, and (ii) comparable compressed CO2 productivity at a higher CO2 recovery, albeit at a relatively lower product pressure. However, the steam duty for regeneration of the chemisorbent was reduced by ∼50% for the promoted alumina. [Copyright &y& Elsevier]