A Study On Gas/liquid Phases Transport Mechanism In CO₂ Absorption Process

CO2 emission has been continuously increasing in recent years and exacerbates the global warming,so the CO2 emission mitigation is of great benefit to the control of climate change.CCUS has increased carbon dioxide utilization on the basis of its carbon capture and sequestration technology,which includes three major categories of chemical utilization,bio-utilization and geological utilization.In the absence of CCUS,most climate models will not achieve the emission reduction targets because CCUS can reduce emissions by several times.Without CCUS,the estimated cost increase is as high as 138%on average.However,the CCUS demonstration projects in China have witnessed rapid development.From the perspective of quantity and storage scale,our country has become the second largest country following the United States.In the second chapter,the computational models of CO2 absorption aiming at the technical principle by aqueous ammonia solution in a random packed column are developed first,where the packing porosity obeys the normal,empirical profile,piecewise constant distributions.The hydrodynamic and mass transfer performances,as well as the CO2 removal efficiency are obtained by means of numerical simulation.The results in the third chapter show that the random packing with the porosity following the normal distribution leads to a better mass transfer performance,thus a high CO2 removal efficiency.More ammonia solution can form a bigger interfacial area,thus enhance the mass transfer performance.Then,on the basis of the random packing model with normal porosity distribution,the effects of ratio of height to diameter,gas inlet flow,liquid inlet flow,liquid phase volume fraction,gas phase volume fraction and temperature are verified.The optimum height-diameter ratio of the packed tower is 3,and the optimum absorption temperature is 20 ?.The forth chapter of this work also compares the CO2 absorption characteristics of MEA aqueous solution and ammonia solution under the same operating conditions,and it also concludes that the overall mass transfer coefficient of ammonia solution and CO2 removal efficiency is greater,and the absorption effect of CO2 is better.Finally,the mechanism and harm of ammonia slip are discussed in this paper,and the existing theoretical methods of ammonia slip inhibition at home and abroad are preliminarily integrated.