| Absorption is an important method for gas separation. It has been widely used in environment protection, low-carbon chemicals manufacturing and new energy resource utilizing. To develop an appropriate absorbent is the primary achievement of the absorption technology. High efficient absorption is the key point to increase the facility output, decrease the energy consumption and product comprehensive cost.A focus on theoretical basis of developing new absorbent was studied in the paper, and novel absorbents for CO2 system and ethylene system were under researching as well. On the basis of energy correlation between thermodynamic properties and molecule interactions, the thermodynamic criterions of absorbent selection were investigated. Through measuring the data of vapor-liquid phase equilibrium (VLE) and simulating the gas absorption processes, this evaluation method of absorbent is proven. The main contents are shown as follows.Firstly, two thermodynamic criterions for absorbent selection were proposed by analyzing and evaluating thermodynamic characteristic behaviors of VLE in absorption process, i.e. the appropriate absorbent can be selected by the extrema value of the excess Gibbs function (GEmax) and the absorption potential(ψi) for a binary system of absolute-gas and absorbent. The less the system GEmax value is, the more significant the absorption effect will be; on the other hand, it can be evaluated by the absorption potential of the gas-absolute. Namely, the bigger theψi value is, the more significant the absorption effect will be. Meanwhile, the GEmax value and theψi value can be estimated by UNIFAC model.Base on the above research, the absorbents for CO2 system and C2H4 system were chosen accordingly. By analysis and comparison, alcohols and esters have a good absorption effect for CO2 system, especially, formate esters have a much more better performance than other esters; esters, ethers and ketones have a good effect for C2H4 system. For the series of aromatic hydrocarbons, from toluene, xyluene to trimethylbenzene, theψi value was significantly increasing, but the GEmax value was singnificantly decreasing.Secondly, the experimental apparatus has been set up to measure VLE data using static equilibrium method. The VLE data of CO2+butyl ether system was determined and correlated by the Peng-Robinson equations of state, then the binary interaction parameter (ky) was reduced, kij= 0.0401. The VLE measurements and data correlations for C2H4+toluene system and C2H4+1,3,5-trimethylbenzene system were performed respectively. By analysing the VLE experimental results and the reference data of CO2 systems and C2H4 systems, it was validated the absorption performance evaluations using the GEmaxvalue and theψi value proposed by this work. Namely, the less of the GEmax value, or the bigger of theψi value, the less y1/x1 is, and the bigger gas solubility is in the absorbents.Finally, the theoretical proposal of the paper has been validated as well by following research. The absorption processes of CO2 system and C2H4 system have been simulated by adopting Aspen Plus software and the VLE model parameters obtained from this work. The simulation result for the syngas purifying process by butyl ether absorbent shows that the CO2 content of purified gas can be lower than 0.4%, the CO2 content of off-gas can be up to 95.37% or more, the CO2 recovery ratio for feed-stock can be more than 86%, appearing excellent separating results; whilst the energy consumption was much less than present technologies by Rectisol absorbent and Selexol absorbent. The simulation result for the C2H4 recovering process by 1,3,5-trimethylbenzene absorbent shows that the process has lower operating pressure of absorbing and desorbing, less lose of absorbent and less energy consumption, compared with the patent process using LPG as absorbent.
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