Recovery of light hydrocarbons from natural gas by vacuum pressure swing adsorption process

Abstract

Vacuum pressure swing adsorption process was developed for light hydrocarbons recovery from natural gas in this study. Silica gel has been selected as adsorbents used in adsorption process because of its appropriate adsorption capacity and easier regeneration. Three kinds of cycle configurations were developed and evaluated for the extraction of light hydrocarbons from low pressure natural gas on the basis of six bed VPSA process, meanwhile effects of operating parameters on VPSA process performances were investigated. Results demonstrated that C-VPSA process with co-current blowdown step could be able to improve the enrichment ratio of light hydrocarbons in heavy product stream significantly in comparison with B-VPSA process only with counter-current blowdown step. Further enhancing in enrichment ratio of light hydrocarbons in heavy product stream was capable to be achieved by R-VPSA process with heavy product stream reflux, but its energy consumption for light hydrocarbons recovery was much higher than that of C-VPSA process and B-VPSA process. Therefore, the C-VPSA process has been considered to be a good option for light hydrocarbons recovery, in which the best case demonstrated that the enrichment ratio of light hydrocarbons in heavy product stream could achieve 5.06 without sacrifice of quality of light product stream. Moreover, the energy consumption of C-VPSA process was 4.93 kJ per mole light hydrocarbons, which was one-third of energy consumption of R-VPSA process.