The invention relates to a method and a system for converting carbon dioxide into chemical feedstocks.
Along with power generation, conventional fossil fuel combustion generates various chemical by-products, such as nitrogen-, carbon- and sulphur oxides which exit the boiler or combustion chamber in the form of flue gas. In the past it was acceptable to allow flue gas to discharge from power plants and industrial facilities directly into the atmosphere without further treatment. However, with increasing evidence about environmental damage linked to, for example, the acidification of the atmosphere as a result of sulfur oxide emissions and the risk of adverse climate change from global warming due to greenhouse gas emissions, flue gas treatment to mitigate emissions with pollution abatement techniques is becoming more important. Conventional technologies for flue gas treatment involve resource and energy intensive processes which increase considerably operating costs. Carbon capture technologies focus on preventing carbon dioxide from entering the atmosphere. In the case of emissions from industrial applications, abatement methods of various maturity levels exist presently to capture carbon dioxide and to recover it as a concentrated stream that is amenable to geological sequestration or as a raw material for industrial processes. Commercial post-combustion carbon dioxide capture systems currently in operation involve carbon dioxide absorption with aqueous monoethanolamine MEA. MEA can be used in aqueous solutions for scrubbing certain acidic gases such carbon dioxide. The process takes place in tall columns known as scrubbers in which a turbulent flow promotes a rapid carbon dioxide transfer from gas to liquid. Differences in density make it easy to separate the emerging gas and liquid. To recover the captured carbon dioxide, the loaded solvent is pumped to a stripper in which it is exposed to hotter carbon dioxide free gas, typically steam. Upon heating, carbon dioxide is desorbed. The stripped liquid is pumped back to the scrubber while the mixture of steam and carbon dioxide is cooled to condense the steam, leaving behind high-purity carbon dioxide suitable for compression and, after transportation to an appropriate site, sequestration as described for example by Howard Herzog, Jerry Meldon, Alan Hatton, Advanced Post Combustion carbon dioxide capture, April 2009 (http://web.mitedu/mitei/docs/reports/herzog-meldon-hatton.pdf). Accordingly, isolating of carbon dioxide from a flue gas and using the isolated carbon dioxide for further processing is known. In a conventional combustion system fuel such as carbon is burned in a burning stage with an exothermic reaction to generate energy and the carbon dioxide forming reaction products of the reaction can be isolated from the flue gas emitted by the combustion system.
However, conventional combustion systems do not use the generated carbon dioxide to produce valuable fine chemical products which could be used as chemical starting materials in further synthetic processes. Conventional post-combustion carbon dioxide capture systems, as used in power plants and in particular coal fired power plants CFPP, focus on isolating carbon dioxide in the flue gas without using the separated carbon dioxide as a chemical compound which could be used in further synthetic processes.