Basic Research Of Carbon Dioxide Absorption Process In Aqueous Solutions Of Methyl-di-ethanolamine And N-(2-aminoethyl)-ethanolamine

CO₂ capture is an issue that attacts wide attention around the world.Chemical absorption method based on amine solvents is the main method in decarburization.Engineering problems such as high viscosity,blistering fast,solvent degradation,high energy consumption in desorption always emerge in using single amine solvent.Therefore,the mixture of amine solvents has received widely attention in these days.Many industrial sovents in the market are the mixture of 2?5 kinds of alcohol amines,combined with activators and anti-foaming agent.It is very difficult to predict the thermodynamic properties and reaction kinetics of mixture amines,all of these make the design and operation of many decarburization units lack reliable design basis.Molecular simulation technique can predict the thermodynamic properties of sovents and reaction kinetic can be also calculated by using molecular simulation software.This work carried out around a new-builded decarburization unit,which use a patent solvent as its absorbent.The solvent is a mixture of methyl-di-ethanolamine?MDEA?and N-?2-aminoethyl?-ethanolamine?AEEA?.The ratio of AEEA:MDEA is around 7:3 and a small amount of piperazine?PZ?is used as activator.Molecular simulation is used to predict the vapor-liquid equilibrium and reaction kinetics in this work.The simulation results are used in software Aspen plus 10 to simulate the primary parameters for the new industrial device.In this paper,software COSMO-therm X is used to predict the density,p Ka value,VLE data,vaporization enthalpy of amine and excess enthalpy of alkylamine-water system.The initial simulation result of density and equilibrium vapor pressures of pure alkylamine are deviates with the experiment result.After correction,a high precision result can be got.The accuracy of the simulation result of p Ka value is not enough,but it can provide a method to screen the solvent.The calculation result of vaporization enthalpy is and excess enthalpy agree well with the experiment result.Software Gaussian 09 is used to study the reaction kinetics of carbon dioxide absorption in aqueous solution of AEEA and MDEA.According to the‘zwitterion mechanism',aminocarboxylic acid mechanism and‘three moculars mechnism',possible reactions in the absorption and desorption process are studied in this paper and a micro-kinetic model is set for the system.The reaction rate constant can be fit by experiments.Aspen plus simulator is used to simulate the absorption and desorption process,97.69%of CO₂ in the feed gas is removed and CO₂ contnet in the purified gas is 1.28%.