Removal of Carbon Dioxide from Natural Gas Using a Zeolite-Based Pressure Swing Adsorption Process
摘要
Natural gas processing consists of pretreatment, acid gas removal, N2 rejection, and distillation. Among these, acid gas removal requires significant energy, and thus, there is a need for efficient CO2 separation technology to replace conventional amine scrubbing. To develop CO2-adsorption technology for natural gas, a vacuum pressure swing adsorption (VPSA) process was developed using a Cu-modified zeolite adsorbent. Adsorption isotherms for CO2, N2, and CH4 on the Cu-modified zeolite adsorbent were measured, and adsorption equilibrium parameters were estimated using dual-site Langmuir isotherms. Single-component breakthrough experiments subsequently were performed and mass transfer rate parameters were estimated using these measured dynamic data, yielding values of 0.35, 0.5, and 0.5 s−1 for CO2, N2, and CH4, respectively. The VPSA process based on the modified Skarstrom cycle was constructed, and for feed conditions of CH4, CO2, and N2 ratio of 80, 10, and 10 vol%, the CO2 recovery and CH4 recovery rates were confirmed to be 70.1% and 90.0%, respectively. Subsequently, multi-objective optimization was performed on CO2 recovery and CH4 recovery to obtain the Pareto frontier curve. The results indicated that achieving a CO2 removal rate of over 90% yields a CH4 recovery rate of 85%.