Design And Numerical Simulation Of Key Equipment For CO₂ Absorption By Liquid-Liquid Phase Change Solvents

CO₂ capture technology is an important method to alleviate global warming.The chemical absorption method is a relatively mature capture technology,but the excessive energy consumption of regeneration limits the development and application.In recent years,the phase change absorber proposed by the researchers has a phase separation phenomenon after CO₂ loading,and CO₂ is enriched in one phase.Therefore,it is only necessary to heat regeneration of the rich liquid phase,which can reduce the energy consumption for regeneration and has a large energy saving potential.However,most of the current research is limited to the phase change absorbent development and performance test analysis of small test experiments.How to accelerate the industrial production application of phase change absorbent is particularly important.Based on the basic research on phase change absorbent,including the developed mainstream phase change absorbent,previous experimental research process and absorption phase change mechanism,it is proposed to absorb CO₂ with MEA and n-propanol solution as phase change absorption system.Key equipment design scheme for pilot test:SD-type static mixer with liquid-liquid two-phase mixing and gas-liquid multi-phase reaction spray tower device.On this basis,the three-dimensional numerical model of key equipment was established respectively.The simulation results provided reference and guidance for the design and process operation parameters of the decarbonization pilot test equipment for phase change solvent system.Firstly,in order to solve the problem of mixing the solution of the depleted liquid and the rich liquid after regeneration in the process cycle,an SD static mixer was designed,and the Mixture multi-phase flow model was used to calculate the liquid-liquid two-phase flow field.Velocity distribution,phase fraction distribution,and pressure drop variation.The results show that the two-phase fluid has a good mixing effect after flowing through the mixer,which provides a good prerequisite for the next step of gas-liquid heterogeneous reaction.Subsequently,the Euler-Lagrange model was used to set the boundary conditions in the Fluent software for flow field simulation.The gas flow distribution uniformity and pressure drop were used as the evaluation criteria,and the gas phase velocity field and pressure field were used for description and analysis.?1?Single-phase flow in the state of unsprayed empty tower:The distribution of continuous phase in the tower at different inlet speeds of flue gas was investigated,and the appropriate flue gas velocity was initially determined to be 0.15 m/s.?2?Multi-phase flow in the spray state:the dispersion of the droplets has a certain rectification effect with respect to the gas phase distribution in the tower,but the internal flow field motion becomes more complicated and the pressure drop increases significantly.?3?In order to improve the decarbonization efficiency,the parameters of the droplet diameter,the flue gas velocity,the liquid-gas ratio,the spray velocity,and the spray angle are changed respectively by optimizing the process operation parameters.The results show:when the droplet diameter is 0.15 mm,the particle size distribution in the tower is uniform,which can meet the simulation conditions;and that under a single influencing factor:the gas velocity is 0.155 m/s,the liquid-gas ratio is 2 L/m³,the spray speed is 4 m/s,the spray angle is 50°,the gas phase is uniform The distribution of the performance is better;among them,the increase of the liquid-gas ratio is the most significant effect on the pressure drop in the tower,and the optimum value of the flue gas velocity determined in the presence or absence of the spray is basically close.Finally,based on the difference between the processes of the liquid-liquid phase change absorbent and the traditional chemical absorbent decarbonization,analyze the requirements of the control system for the absorption process of the pilot test,and an intelligent gas flowmeter device was designed.