WGS membrane reactor for CO2 emission control

The potential of the WGS membrane reactor in CO2 control in IGCC installations has been studied in greater detail [57]. The possibilities of the reactor and demands set for the membranes have been determined by carefully assessing the process integration options, by experimental membrane characterisation and by using a membrane reactor model. 

Various possible process flow schemes have been proposed. The CO2 removal generally takes place from the cocil gas [56]. Conventional approaches generally consist of a separate multistage water-gas shift (WGS) conversion of the fuel gas, followed by a low temperature CO2 removal process. Hydrogen is 

Hydrogen from the membrane reactor is converted in a gas turbine with a high efficiency. The process efficiency will increase when the hydrogen production (CO conversion) and recovery (on the permeate side) from the membrane reactor is raised. CO2 abatement increases with increasing recovery of carbon components on the retentate side of the membrane. The performance of the reactor can be measured in terms of these three parameters. The boundary conditions for the membrane reactor in the total system depends upon final 

Inorganic membrane development is still in progress [57] (see also Section 14.2.2). Microporous silica membranes have been developed at several universities and research institutes. Membrane selectivities of 15 and 20 for the separation of H2 from CO2 have been reported. Even higher selectivities for H2 arid CO, CH4 and N2 have been measured [20,57]. Most measurements reported in the literature have been performed on a laboratory scale. However, it has been shown that it is possible to upscale these microporous ceramic membranes to, at least, bench scale [31,57]. With other membranes such as noble (Pd) metal membranes and dense ceramic membranes very high and almost infinite selectivities for hydrogen are possible [58]. The permeation of these membranes is generally smaller than the permeation of microporous membranes. 

Microporous carbon membranes have been developed [59] but their possibilities in high temperature hydrogen separation are still unclear, although it is believed that there are opportunities. Scaling-up of these membranes seems possible from a technical point of view. All these membrane types are potentially suitable for application in the WGS membrane reactor concept, provided their endurance is sufficient. 

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