Abstract
Membrane gas separation for carbon capture has traditionally been focused on high pressure applications, such as pre-combustion capture and natural gas sweetening. Recently a membrane-cryogenic combined process has been shown to be cost competitive for post-combustion capture from coal fired power stations. Here, the membrane-cryogenic combined process is investigated for application to post-combustion carbon capture from the flue gas of a Natural Gas Combined Cycle (NGCC) process. This process involves a three-membrane process, where the combustion air is used as the sweep gas on the second membrane stage to recycle CO2 through the turbine. This ensures high CO2 recovery and also increases the CO2 partial pressure in the flue gas. The three-CO2-selective membrane process with liquefaction and O2-enrichment was found to have a cost of capture higher than the corresponding process for coal post-combustion capture. This was attributed to the large size and energy duty of the gas handling equipment, especially the feed blower, because of the high gas throughput in the system caused by significant CO2 recycling. In addition, the economics were uncompetitive compared to a modelled solvent absorption processes for NGCC.
Highlights
Recent design developments in membrane gas separation are moving this technology towards being economically competitive for post-combustion carbon capture from coal-fired power stations [1,2]
These competitive membrane process designs are extended to post-combustion capture from a Natural Gas Combined Cycle (NGCC) process, to evaluate the viability of membrane technology
Membrane-based carbon capture has only been considered for natural gas sweetening before NGCC [3] and for pre-combustion capture before the IGCC process [4], while post-combustion capture has only been studied in depth using solvent absorption [5,6,7,8,9], or as a novel Integrated Gasification Combined Cycle (IGCC) process with flue gas recycling [10]
Summary
Recent design developments in membrane gas separation are moving this technology towards being economically competitive for post-combustion carbon capture from coal-fired power stations [1,2]. Membrane-based carbon capture has only been considered for natural gas sweetening before NGCC [3] and for pre-combustion capture before the IGCC process [4], while post-combustion capture has only been studied in depth using solvent absorption [5,6,7,8,9], or as a novel Integrated Gasification Combined Cycle (IGCC) process with flue gas recycling [10]. This is because for NGCC the flue gas has a low CO2 partial pressure which has previously been seen as a limitation for membrane gas separation. Sweep gas on the second membrane stage is Technologies 2016, 4, 14; doi:10.3390/technologies4020014 www.mdpi.com/journal/technologies
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