Separation and capture of carbon dioxide from CO₂/H₂ syngas mixture using semi-clathrate hydrates

The relation between anthropogenic emissions of CO₂ and its increased levels in the atmosphere with global warming and climate change has been well established and accepted. Major portion of carbon dioxide released to the atmosphere, originates from combustion of fossil fuels. Integrated gasification combined cycle (IGCC) offers a promising fossil fuel technology considered as a clean coal-based process for power generation particularly if accompanied by precombustion capture. The latter includes separation of carbon dioxide from a synthesis gas mixture containing 40mol% CO₂ and 60mol% H₂.

A novel approach for capturing CO₂ from the above gas mixture is to use gas hydrate formation. This process is based on selective partition of CO₂ between hydrate phase and gas phase and has already been studied with promising results. However high-pressure requirement for hydrate formation is a major problem.

We have used semiclathrate formation from tetrabutylammonium bromide (TBAB) to experimentally investigate CO₂ capture from a mixture containing 40.2mol% of CO₂ and 59.8mol% of H₂. The results shows that in one stage of gas hydrate formation and dissociation, CO₂ can be enriched from 40mol% to 86mol% while the concentration of CO₂ in equilibrium gas phase is reduced to 18%. While separation efficiency of processes based on hydrates and semi-clathrates are comparable, the presence of TBAB improves the operating conditions significantly. Furthermore, CO₂ concentration could be increased to 96mol% by separating CO₂ in two stages.