Experiment And Simulation Studies For Separating CO₂/N₂ By Dual-reflux Pressure Swing Adsorption Process

Carbon dioxide is a greenhouse gas,Climate change caused by carbon dioxide emissions is widely concerned.So we need to seek a highly efficient means to capture carbon dioxide,as well as recycling valuable by-products to reduce emissions costs,which are of great importance to control the greenhouse effect and energy efficient utilization.Pressure swing adsorption technology is a new type of gas separation and purification technology,which has the advantage of low energy consumption,less investment and easy operation and so on.But the traditional pressure swing adsorption technology can only product a single CO₂ gas.In order to make full use of gas resources and product two kinds of high purity products,we adopt DR PSA process,and the process used for separating CO₂/N₂ mixture has been studied by experiment and simulation.DR PSA process used for separating CO₂/N₂ mixture is studied to product two kinds of high purity products by experiment and simulation.On the one hand,the experimental results and simulation results are analyzed to verify the feasibility of the DR PSA process and the accuracy of the mathematical model.On the other hand,basic data are provided to PSA of capture CO₂ and prepared for the next optimization of DR PSA process.In this article,silica gel is a kind of adsorbent,which has good separation effect and characteristics of desorption for the CO₂/N₂ mixture.The static and dynamic adsorption quantity is measured by the characteristic experiment.In the dynamic experiment,the adsorption data of CO₂/N₂ mixture on silica gel obtained from the dynamic experiment are calculated to get gas separation factor and verify the good effect of silica gel for separating CO₂/N₂ mixture.In the static experiment,the CO₂/N₂adsorption quantity on silica gel is measured under different pressure and temperature.Then,the data are fitted to get the adsorption parameters by Extending Langmuir non-isotherm,these corresponding parameters are used to experiment and simulation of DR PSA process.Finally,a two-bed experimental device of DR PSA process is established to separate CO₂/N₂ mixture.The experiment mainly examines the operating variables of the feed position,method of equalizing-pressure,light component reflux flow rate and heavy product gas flow on the effect of the purity and recovery rate of the product gas.In chemical software Aspen Adsorption,the dynamic numerical model is used to simulate the DR PSA process.Experimental results and simulation results showed:the feed temperature is 298.15K,adsorption pressure 2.0bar（pabs）and desorption pressure 0.2bar.Under the optimal operating conditions that Z_f=0.4,the equalizing pressure of the bed top,Q_LR=0.408slpm and Q_HP=0.603slpm,96.8%of CO₂ could be recovered with purity of 95.6%via DR PSA process meanwhile the purity and recovery of light product N₂ were higher than 98%,energy consumption is 2.5MJ/kg CO₂.