Modeling, Simulation and Optimization of a Carbon Capture Process Through a TSA Column

By capturing carbon dioxide from biomass flue gases, energy processes with negative carbon footprint are achieved. Among carbon capture methods, the fluidized temperature swing adsorption (TSA) column is a promising low-pressure alternative, but it has been developed on small scales. This work aims to model, simulate and optimize a fluidized TSA multi-stage equilibrium system to obtain a cost estimate and a conceptual design for future process scale up. A mathematical model described adsorption in multiple stages, each with a heat exchanger, coupled to the desorption operation. The model was based on elementary macroscopic molar and energy balances, coupled to pressure drops in a fluidized bed designed to operate close to the minimum fluidization velocity, and coupled to thermodynamics of adsorption equilibrium of a mixture of carbon dioxide and nitrogen in solid sorbents (the Toth equilibrium isotherm was used). The complete fluidized TSA process has been optimized to minimize costs, considering equilibrium in each stage. The optimal configuration for heat exchangers was determined and a unit cost for carbon dioxide capture was estimated. It was found that a small number of stages is required to meet captured carbon specification at 95% molar purity, while process cost per metric ton of CO2 was within range of other capture technologies. These findings show that the methodology developed here is useful for guiding the conceptual design of fluidized TSA process for carbon capture.