(462g) Preconcentration of Methane By Vacuum-Temperature Swing Adsorption for Removal from Air
AIChE Annual Meeting
2023
2023 AIChE Annual Meeting
Separations Division
Adsorption for Negative Emissions
Wednesday, November 8, 2023 - 5:18pm to 5:36pm
The continual increase in atmospheric concentrations of greenhouse gases is a substantial driver of global warming and climate change. The intergovernmental panel on climate change (IPCC) in its sixth assessment report clearly highlighted the significant contributions of non-CO2 greenhouses such as methane (CH4) on global warming and their role in meeting climate neutrality by 2050. While the atmospheric concentrations of CO2 have increased by about 50% since preindustrial times, the CH4 concentrations in the atmosphere, although much lower than CO2, have more than doubled (~2 ppm vs 722 ppb) during the same period. Particularly, agriculture activities related to dairy cattle, manure, etc., are the dominant global source of anthropogenic methane emissions. Since the emissions at these sources are mostly in confined areas, the CH4 concentrations found are higher than in the air, typically around 10 â 1000 ppm. With over 25 times more global warming potency (due to its high radiative efficiency) compared to CO2 over a 100-year horizon, removing CH4 from the atmosphere or other diluted sources is very beneficial and presents an opportunity of slowing down climate change. Unlike CO2 which has to be separated from air, CH4 is reactive and can be removed by converting it to CO2 or other products. However, the ultra-dilute concentrations of CH4 in the air make it extremely challenging to directly remove CH4 in the conversion process. To tackle this challenge, one option can be focusing only on mitigating CH4 emissions with increased concentrations at agricultural sources or the other route is to preconcentrate CH4 in the air from ppm to % levels to facilitate the conversion. The latter option further accounts for the removal of historical CH4 emissions.
This study considers the second option where the feasibility of preconcentrating CH4 in the air or from very dilute sources to a few % levels is examined using vacuum-temperature swing adsorption processes before CH4 conversion. The proposed concept involves the simultaneous enrichment of CH4 and CO2 from air, which can be easily integrated with direct air capture (DAC) systems downstream. The process design methodology used herein is based on detailed process simulations and optimizations with an emphasis on minimizing energy consumption and maximizing the productivity of the process. The details of the process and the adsorbents along with the optimized results will be presented at the meeting.