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Ascent Project
3 - Fast sorbent mediated water-gas shift

The main objective of the ASCENT project is the proof of concept of three different advanced CO2 capture process. One of these processes, the carbonated shift (C-SHIFT) has now been performed at the Imperial College London, partner of the project consortium, in a dedicated test-rig. The aim of C-SHIFT is to produce a fuel stream consisting of high temperature H2 and H2O stream, at a pressure above the compressor temperature of a gas turbine, with a CO2 capture efficiency greater that 90%. Alkali carbonate promoted Mg/Al-hydrotalcites (HTCs) and magnesium oxides were considered the most promising of the sorbent materials reviewed. In particular, high MgO containing Mg/Al-hydrotalcites impregnated with K2CO3 and high magnesium contents were identified as being strong candidates for high pressure, mid-temperature CO2 capture in the presence of large quantities of steam.

However, in the context of C-SHIFT, the cyclic performance information provided thus far is limited. There is a significant discrepancy between the long carbonation periods under which these materials have been investigated and the short residence time that the CO2 sorbent material is expected to reside within the proposed C-SHIFT carbonator (< 60 s). At present there are no published studies reporting either the uptake capacity or kinetics for the reaction between CO2 and HTC-derived materials over time scales relevant to C-SHIFT. The work performed recently at Imperial College within ASCENT project  aims to address this gap in the knowledge and provide information relating to the kinetics and capacities for CO2 uptake by K2CO3-promoted HTC-derived materials at conditions relevant to a C-SHIFT process. This has been achieved using a pressurised spouted fluidised bed reactor for pressure-swing operation at pressures up to 10-20 bar with large concentrations of steam. Fluidised beds are particularly suited for kinetic studies based on their superior heat and mass transfer characteristics when compared with other reactor configurations such as fixed beds and thermo-gravimetric analysis (TGA).

 The main achievements of this work package are mainly (i) the choice of lead sorbents according to shared criteria; (ii) modification of high-pressure fluidised bed reactor for P-Swing operation at the proof-of-concept scale. (iii) Proof-of-concept testing in fast high pressure fluidised bed reactor scanning over a wider range of conditions.

 A new C-SHIFT process configuration has been suggested.

Below, each of these topics have been described in more detail.

For further information visit the newsletter section.

CSHIFT proof-of-concept at the Imperial College of London Fixed bed test rig at the ECN lab for testing sour conditions

The research leading to these results has received funding from the European Union Seventh Framework Programme  FP7 under grant agreement n° 608512