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The most common technology for postcombustion of CO 2 capture is the amine solvent scrubber. The energy consumption for capturing CO 2 from flue gases using amine solvent technology is 15-30% of the power plant electricity production. Hence, there is a need to develop more efficient methods of removing CO 2 . A circulating fluidized bed using sodium or potassium carbonates is potentially such a process, as their high decomposition pressures allow regeneration at low temperatures using waste heat rather than steam from the power plant. But equilibrium data for the sorbents require the use of several cooled stages to achieve high CO 2 conversions. Here, a method of computing such a number of stages for a given CO 2 conversion was developed using multiphase computational fluid dynamics. It was found that it required six equilibrium stages to remove 96% of CO 2 with the initial mole fraction of 0.15 in a sorption riser. V C 2017 American Institute of Chemical Engineers AIChE J, 63: 5267-5279, 2017 CO 2 capture conceptsState of the art of CO 2 capture technologies for existing fossil energy power plants are limited to amine absorbers. 16 They have been used for removal of CO 2 from natural gas for Correspondence concerning this article should be addressed to P. Piumsomboon at pornpote.p@chula.ac.th. Figure 6. Grid selection and simulation validation.(a) Grid selection study. (b) Comparison to the experiments. 39 [Color figure can be viewed at wileyonlinelibrary.com] 5272 Figure 13. Transient CO 2 capture.(a) Removal percent of CO 2. (b) Thermal sensitivity to CO 2 sorption. [Color figure can be viewed at wileyonlinelibrary.com] 5276

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A 1 m in diameter and 3.55 m tall fluidized bed riser internally with water tubes, which required six equilibrium stage of riser-sorber for capturing about 95% of CO 2 emitted from a coal power plant, were designed to replace the multisingle risers. At the optimum operating condition, the temperature of the cooling tubes in the bottom, the middle and the top of the riser were kept constant values at 50, 40, and 308C, respectively. The hot water (578C) from lowest exchanger section can be used to preheat the spent sorbent for the regeneration in a downer. The rest of the heat for the regenertion is obtained from the stack gas (100-1308C). This new concept promises to reduce the energy consumption for CO 2 removal from flue gas. The only energy requirement is for pumping fluid and fluidizing particles in the bed.