ECN publication
Water gas shift membrane reactor for CO2 emission reduction and hydrogen production
Published by: Publication date:
ECN Energy Efficiency in Industry 18-1-2007
ECN report number: Document type:
ECN-M--07-006 Conference Paper
Number of pages: Full text:
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Presented at: 6th Netherlands Process Technology Symposium (NPS6), Veldhoven, The Netherlands, 24-25 oktober 2006.

The use of water gas shift membrane reactors for carbon dioxide sequestration in fossil fuel fired energy production plants has been studied for more than a decade. In general CO2 emission reduction is possible at the cost of the efficiency of electricity production. Here we present a water gas shift (WGS) membrane reactor concept in which CO2 capture at a refinery is combined with the production of hydrogen as energy source and of pure hydrogen that can be used as chemical feedstock. A base case refinery process has been chosen in which several unit operations, e.g. heaters, boilers and furnaces, produce flue gas containing CO2. A feasibility study into the removal of CO2 from these flue gases using the conventional amine absorption process as best available technology has been performed [1]. Based upon this study a new process using a WGS membrane reactor is proposed in which syngas is converted into a hydrogen rich and a CO2 rich stream. This hydrogen stream is used as fuel gas for the existing refinery heaters, boilers and furnaces and the process is suggested as an improved CO2 capture alternative [2]. In the present study this WGS membrane reactor process has been modified further by using two WGS membrane reactors in series. One reactor is for the production of chemical feedstock grade hydrogen and one for a hydrogen rich fuel gas stream. This new process still meets the energy demands of the refinery and, of course, the CO2 capture demands set. A modelling study has been performed using ASPEN+ flowsheeting calculations. A WGS membrane reactor model has been implemented in ASPEN+ and was combined with gas separation data of inorganic membranes for hydrogen separation. It has been found that a membrane selectivity of at least 100 is needed for obtaining a hydrogen stream with a purity of 97.5 mol.% and meeting the hydrogen and carbon recovery demands. A total membrane area of 16,750 m2 is needed for the refinery, which has a total energy demand of approximately 800 MW. Economic calculations show that a feasible process can be obtained that could compete with the CO2 capture option using the amine absorption technology. The economics, however, very much depend on energy and hydrogen prices. Flowsheeting reults have shown that by using a ceramic membrane based water gas shift process the energy demand of a refinery can be combined with a carbon recovery of >90% and the production of chemical grade hydrogen.

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