DESIGN OF A PLANT FOR THE DIRECT CAPTURE OF METHANE AND CARBON DIOXIDE FROM AIR TO PRODUCE SYNTHESIS GAS

Climate change is a long term difference in temperature and weather conditions.The two main greenhouse gases causing climate change are carbon dioxide (CO2) and methane (CH4) . In this research work, a plant was designed for the direct capture of methane and CO2 from air and for the production of synthesis gas through the dry reforming process using Aspen Adsorption and Aspen Plus as the simulation software. The feed stream consists of air stream (99.95% N2 , 0.05% CO2 and 0.00023% methane) , it was assumed that there was a pretreatment to remove oxygen using the catalytic combustion process, water vapour with a dehumidifier and argon and other trace gases using cryogenic distillation process. The process involves capturing CO2 and methane by passing it through a fixed adsorption bed with zeolite 13X in it which adsorbs the CO2 and methane . As the feed flows through the zeolite, CO2 and methane are trapped allowing nitrogen to pass through , this adsorption process runs for the first 1000s. To regenerate the zeolite, the pressure is being reduced and the adsorbed CO2 and methane is being released. This process is called desorption which runs for the next 1000s. The pressure swing adsorption process was used with a cycle organiser that immediately starts desorption after the adsorption process is complete. The CO2 and methane is preheated through a heat exchanger and then further heated in a furnace to the reaction temperature 500o C and then fed to the fixed bed reformer . The reactor effluent is further cooled down to room temperature and then sent to the syngas recovery section. In the syngas recovery section , the reactor effluent is flashed to recover syngas and separate water formed during the reaction.After the pressure swing adsorption process, A methane concentration of 0.00021% in the methane-rich stream and CO2 concentration of 0.048% in the CO2-rich stream was achieved. This indicates a successful separation. The adsorbent capacity for methane and CO2 was 0.000012mol/kg and 0.000036mol/kg respectively and it showed a selectivity of 3.0 for CO2 over methane. The economic feasibility was evaluated by calculating the total operating cost, raw material cost, utility costs, and total capital cost using Aspen Plus. This analysis helps in understanding the financial aspects of the process. The solid loading and breakthrough curves show the efficiency of the zeolite adsorbent. These curves indicate the saturation point and gas accumulation on the adsorbent. Large-scale renewable methane production using this process could achieve negative CO2 emissions, making a significant contribution to climate change mitigation.