A Multi Scale Modeling Study Of The Performance Of Adsorption Towers For CO₂ Capture

The removing of flue gas carbon dioxide is one of the significant measure to solve the problem of climate changing.There are few techniques on which current industrial purification systems are based.For that,adsorption is a favorable technology which is in a process of development.Here,multi-scale models have developed to simulate dynamics and hydrodynamics of gas mixtures(CO2 and H2)in a fixed bed adsorption column.Adsorption technologies have been applied that are known as pressure swing adsorption(PSA)and temperature swing adsorption(TSA)and to assess optimal operating conditions,the investigation of behavior or different variables have been done for reaction of adsorption and compared the results with the experimental data.PSA due to ease of operation,reliability and reproducibility,it usually takes priority over TSA ability.To develop breakthrough curves for CO2/H2 adsorption,a multi-scale model has been developed by solving the partial differential equations(PDEs)including equations of conservation,models for equations of state,equilibrium,thermodynamics and transport properties of described mathematical model using COMSOL multiphysics software including reactive pellet feature to describe the mass transfer in mesoporous and micro porous of sorbent pellets.At different operating conditions,the model established reasonably matched experimental literature data.The mixture of CO2 and H2 were selected as adsorbate while UiO-67/MCM-41 a hybrid type of MOF were selected as adsorbent.A linear driving force(LDF)model for adsorption kinetics has been applied to simulate the breakthrough curves of carbon dioxide and hydrogen.The mathematical model was used at various conditions and runs to estimate the breakthrough curves of CO2 using different capturing materials.The influence of operating conditions on the process of adsorption showed by the results of the PSA and TSA simulation.The use of LDF resulted in good fitting for all cases for the same value for mass transfer coefficient.The CO2 is adsorbed more when the velocity is low showed by the effect of the feed velocity on the bed CO2 concentration factor,the capacity of adsorption is increased at a lower feed velocity,higher the bed height and low feed concentration are conducive to fixed bed operation.Since CO2 adsorption is an exothermic process,the column temperature rises to ascend with CO2 concentration and temperature will decrease as the adsorption rate decreases.A linear driving force(LDF)approximation model has been presented for the simplification of the intraparticle diffusion/convection mass transfer models.By using this LDF approximation model presented simulations of breakthrough in fixed bed column containing different CO2/H2 feed mixtures compositions.Simulations performed at 298 K and three different pressures(5 bar,15 bar and 25 bar).The parameters of dynamic model that is mass transfer and heat transfer,fitted to an experiment are used to predict further simulations.In addition,the selection of isotherm model is considered.This work also contains the parametric analysis of CO2/H2 adsorption of mixture of gas.The study of parameters involves the effect of bed porosity,particle size and feed velocity on the breakthrough performance.The model simulations are performed in Comsol Multiphysics software.For the development,design and optimization of adsorption of a pressure swing,this study is a required step of CO2 and H2 separation in pre-combustion process for capturing of CO2,For example,combined cycle technology for integrated gasification.