Abstract
In the presented work, 2 simple processes for carbon dioxide (CO2) capture and utilisation have been combined to form a whole systems approach to carbon capture and utilisation (CCU). The first stage utilises a pressure swing adsorption (PSA) system, which offers many benefits over current amine technologies. It was found that high selectivity can be achieved with rapid adsorption/desorption times whilst employing a cheap, durable sorbent that exhibits no sorbent losses and is easily regenerated by simple pressure drops. The PSA system is capable capturing and upgrading the CO2 concentration of a waste gas stream from 12.5% to a range of higher purities. As many CCU end processes have some tolerance towards impurities in the feed, in the form of nitrogen (N¬2) for example, this is highly advantageous for this PSA system since CO2 purities in excess of 80% can be achieved with only a few steps and minimal energy input. Non-thermal plasma is one such technology that can tolerate, and even benefit from, small N2 impurities in the feed, therefore a 100% pure CO2 stream is not required. The second stage of this process deploys a nanosecond pulsed corona discharge reactor to split the captured CO2 into carbon monoxide (CO), which can then be used as a chemical feedstock for other syntheses. Corona discharge has proven industrial applications for gas cleaning and the benefit of pulsed power reduces the energy consumption of the system. The wire-in-cylinder geometry concentrates the volume of gas treated into the area of high electric field. Previous work has suggested that moderate conversions can be achieved (9%), compared to other non-thermal plasma methods, but with higher energy efficiencies (>60%).
Highlights
Research into carbon dioxide capture and recovery for geological storage (CCS) as a greenhouse mitigation technique has seen a rise in interest over recent years
After capture the CO2 is released and passed through a pulsed corona discharge reactor wherein electron initiated dissociation converts the CO2 to carbon monoxide (CO), other products are formed but as the aim of this paper is to provide a proof of concept the detailed kinetical pathway is not discussed further
It is likely that CO2 desorption rate is a function of the system pressure, and as the pressure drops, the weak interactions formed between the molecules and the surface of the sorbent are continually broken as the pressure is reduced with the most weakly bound molecules leaving the system first
Summary
Research into carbon dioxide capture and recovery for geological storage (CCS) as a greenhouse mitigation technique has seen a rise in interest over recent years. Targeted large point source emitters such as power stations would benefit from the convenience of a post-combustion capture process due to the ease of retrofitting. Technologies such as cryogenics, membrane separation, and algal-based systems are all potential options; they are currently in their infancy and not considered economically viable at this stage (Yang et al, 2008; MacDowell et al, 2010; Bhown and Freeman, 2011). TSA process generally produce a humid stream of pure CO2 which will require drying before it can be stored or utilized as an intermediate; this drying step is very energy intensive. PSA has many advantages over traditional systems in that it has a much smaller plant footprint, can accept changing feed compositions and is a stop–start technology making it very flexible with regard to the plant that is supplying it
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