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CLIMIT-Forskning, utvikling og demo av CO2-håndtering

innovative sorbents for the sorbent enhanced water-gas shift process

Alternative title: innovative sorbenter for sorbent fremmet vann-gass skift prosessen

Awarded: NOK 8.8 mill.

The main goal in the iSEWGS project was to develop CO2 sorbents in order to improve the efficiency and economics of a process for hydrogen production. In the process we have worked with (the sorbent enhanced water-gas shift (SEWGS) process) hydrogen is separated from a carbon-containing fuel before it is used in the production of electricity or chemicals, i.e. a pre-combustion process. First, the fuel (natural-gas, bio-gas, oil or coal) is converted to syngas (CO+H2) which is subsequently reacted over a catalyst with steam to form CO2 and more hydrogen. In this stage, the sorbent, which is present in the reactor, reacts and captures CO2 and the reaction is driven towards more hydrogen. The captured CO2 remains in the reactor and a hydrogen rich gas is the product. When the sorbent is filled with CO2 it must be regenerated at 350-400 C. In this step CO2 is liberated and is taken further for transport and storage. The benefits with this process is among other that the produced hydrogen is hot (350-400 C) and comes at elevated pressures (20-30 atm.) Even if the SEWGS process is rather efficient today it has been identified that better and more robust sorbents should be developed in order to compete with processes where the CO2 is captured after e.g. combustion. The most important sorbents today for this process are layered hydroxides (clay minerals) that contains magnesium, aluminium and with some added potassium. We therefore started the project to understand and modify these. One of the main challenges in this project was to prepare a sorbent better than state of the art sorbent. Another important goal was to establish how the sorbents actually operates during industrial conditions. Such insight will likely enable us to prepare significantly improved sorbents. In order to study the sorbents in detail, we applied synchrotron X-ray facilities in Grenoble to map the sorbent's structure when they are in use at relevant industrial conditions. From these studies we developed a hypothesis on what could be the active component under reactive conditions. Based on this insight, we prepared new sorbents related to the original ones that can be relevant as sorbents for the SEWGS process. From this work we have come much closer to understand what the active components in our materials are. We have also developed a new series of sorbent materials where one of the samples has been long term tested at industrial conditions. This sorbent shows improved properties compared to standard reference sorbents. The improvement in the SEWGS process have been estimated through process modelling to be about 10% at certain conditions.

Significant improvements in both cost and energy efficiency for CO2 capture by pre-combustion sorbent enhanced water-gas shift (SEWGS) process can be obtained by using sorbents having increased cyclic sorption capacity compared to state-of-art. In the present project, the competence on the preparation and deep understanding of hydrotalcites, their structures and transformations at the University of Oslo will be coupled with long term experience on sorption phenomena and the development of sorption based processes at SINTEF. Together, the two groups will prepare and evaluate new hydrotalcite based sorbents for the SEWGS process. Mechanistic understanding of the sorbent function as well as long term testing at relevant conditions will be carried out giving direction towards improved sorbents and processes. To assure industrial relevance to the work, Energy research Centre of the Netherlands (ECN) and Politecnico di Milano (POLIMI), who have been major players in the development of SEWGS technology, will participate as project partner. ECN will contribute with relevant long term testing of the best sorbents providing data that will be used in the benchmarking of the SEWGS process utilizing the novel sorbents, while POLIMI will contribute with process benchmarking. The project is planned for a three year period involving one post doc at the university of Oslo and relevant staff at SINTEF, ECN and POLIMI.

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CLIMIT-Forskning, utvikling og demo av CO2-håndtering