The clathrate process for pre-combustion capture of carbon dioxide employing a novel fixed bed reactor

Abstract

Carbon capture and storage (CCS) from large point sources such as power plants is one of the important options for reducing anthropogenic CO2 emissions. One such approach to reduce CO2 emissions is to capture CO2 prior to combustion. In a pre-combustion process, the fuel gas produced contains 40% CO2 and 60% H2 and comes out at a total pressure of 2.5-5 MPa. Some of the processes to capture CO2 from a pre-combustion fuel gas stream are absorption, adsorption, membrane separation, clathrate process and cryogenic distillation. Hydrate Based Separation (HBS) process is one of the relatively new approaches for separation of CO2 from the fuel gas mixture. The basis for the separation is the selective partition of CO2 between the hydrate phase and the gas phase. The clathrate hydrate process is environmental friendly and economically attractive. In this study a novel fixed bed reactor approach for the hydrate based separation process was employed to separate CO2 from a fuel gas mixture. Silica gel and silica sand were used as the medium in the fixed bed reactor and their performance on the separation was evaluated. Experiments were carried out at 9.0, 8.5 and 7.5 MPa and 274.15 K. In silica sand bed, water conversion up to 80% was achieved whereas in silica gel bed water conversion was low irrespective of the driving force. The initial rate of hydrate formation was faster in silica gel bed when compared to that of in silica sand bed. The hydrate crystals formed were decomposed by heating the system from 274.15K to 285.15K and the decomposed gas was collected separately in the reservoir. Almost 65% of the gas was recovered from both silica gel and silica sand bed within 3hr.