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A multi-stage fluidized bed system for continuous CO2 capture by means of temperature swing adsorption – First results from bench scale experiments

Schöny, Gerhard, Dietrich, Florian, Fuchs, Johannes, Pröll, Tobias, Hofbauer, Hermann
Powder technology 2017 v.316 pp. 519-527
adsorbents, adsorption, carbon dioxide, desorption, flue gas, fluidized beds, heat exchangers, heat transfer, powders, surface area, temperature
Most recently, the authors of this work introduced a reactor design for a new post-combustion CO2 capture process that is based on continuous temperature swing adsorption. The system comprises two interconnected multi-stage fluidized bed columns that enable counter-current contact of adsorbent and gas streams in the adsorption and desorption step. The system further allows for effective heat management through indirect heat exchange with the fluidized adsorbent material in each stage. Based on the proposed reactor design, a fully integrated bench scale unit (BSU) has been constructed and put into operation to study the process experimentally. The BSU is designed to capture 90% of the CO2 present in synthetic flue gas mixtures at a maximum capture rate of 35kgCO2,capt per day using amine-functionalized adsorbent materials. First results obtained from continuous CO2 capture experiments showed that the design capture targets can be reached with this unit. Despite the fact that only five fluidized bed adsorption stages were implemented, CO2 was not detected at the adsorber outlet during the initial minutes of the experiments, indicating that gas-solids contact is sufficient and adsorption kinetics are fast. However, in the initial CO2 capture experiments it was not possible to achieve the desired operating temperatures within the desorber and the CO2 capture capacity of the unit seemed to be limited by heat transfer. Installation of heat exchangers with a higher surface area entailed an improved capture performance. It was thus concluded that performance limitations of the TSA BSU lie within its heat transfer properties rather than within the prevailing adsorption conditions.