Performance comparison of three adsorption cycles for CF4 recovery from waste gas using 13X zeolite

Abstract

CF4 is one of the most influential greenhouse gases. With the development of the microelectronics industry, the emission of CF4 waste gas increases sharply. The adsorption method for CF4 recovery from waste gas can bring both environmental and economic benefits. However, most of the existing studies on the CF4 recovery by adsorption focus on the properties of adsorbents, and the related studies on the recovery cycle are just starting. But the better cycle performance can be got only by considering the characteristics of the cycle. In this paper, the molecular simulation method of Grand Canonical Monte Carlo is used to calculate the adsorption equilibrium isotherm of CF4 on zeolite 13X. An equilibrium model of the adsorption cycle is developed, and the cycle performance of temperature swing adsorption (TSA), pressure and temperature swing adsorption (PTSA) and vacuum and temperature swing adsorption process (VTSA) are optimized. The relationship between evaluation index (purity, recovery rate, exergy efficiency) is analyzed. The optimal performance of the three cycles is compared. It is found that the adsorption temperatures corresponding to the optimal Pareto solutions of the three cycles are all around 273 K. In the solution set of optimal cycle performance of the three cycles, the purity and recovery rate show a nearly linear positive correlation. Both the purity and the recovery rate are in a competitive relationship with the exergy efficiency. In the VTSA cycle, when the purity is greater than 0.795, the exergy efficiency drops rapidly as the purity increases. The optimal value of the performance index of each cycle is sorted as VTSA > PTSA > TSA. Only an increase in CF4 adsorption capacity within 6 times can increase the optimal purity and exergy efficiency by around 0.15, but it can only increase the recovery rate by 0.03.