Ultra-high CO2 capture efficiency from power plant using H2 gas stripping for integrating CO2 separation and conversion to methanol

Abstract

Carbon capture, utilization, and storage (CCUS) have emerged as a crucial strategy for mitigating the impact of climate change resulting from the use of fossil fuels. Among the various research endeavors focused on CO2 separation, the primary emphasis has been on capturing CO2 from the flue gas of natural gas-fired power plants, which typically contain a relatively low CO2 content, approximately 4%. In this study, a capture process employing methanol as a solvent and H2 as a stripping gas is utilized to minimize energy consumption in the recovery column. The captured CO2 is subsequently converted into methanol (MeOH). Despite the relatively low purity of the captured CO2, an impressive percentage of over 99% is successfully captured from the flue gas. This approach also takes advantage of the utilization of H2 gas stripping, which serves as one of the components for methanol synthesis in the CO2 hydrogenation reaction. Rate-based process simulation models for CO2 absorption by Monoethanolamine (MEA) and MeOH based- solvent were developed using Aspen Plus and provided a basis for a techno-economic analysis. Energy consumption of CO2 capture using MeOH solvent, at 6.32 MJ/kg CO2, is significantly lower compared to the energy consumption of MEA solvent, which stands at 15.9 MJ/kg CO2. Total exergy loss is greatly reduced to 61.77% compared to MEA-based solvent process. Furthermore, employing MeOH solvent results in a 6.12% cost reduction for the entire system, encompassing CO2 capture and methanol synthesis, when compared to MEA solvent. This cost reduction can be further increased to 15% by implementing heat integration. These findings highlight the promise of utilizing a methanol-based solvent and H2 gas stripping in CO2 capture processes. This approach not only delivers energy savings and cost reduction, but also provides an opportunity for converting capture CO2 into valuable a product such as methanol, thus advancing a more sustainable and economically feasible strategy for combating climate change. Keyword: CO2 capture, Hydrogen gas stripping, Physical absorption, Methanol synthesis, Techno- economic analysis, Exergy analysis