The Sorption-Enhance Water-Gas Shift (SEWSG) technology is a pre-combustion CO2 capture technology that combines the necessary water-gas shift step in pre-combustion processing with the separation of CO2 at high temperature. From its very conception, it has been clear that the technology has the potential to deliver very high performance in terms of efficiency, and the potential to outperform existing state-of-the-art technologies.
The stepwise approach to development of the process has occurred within both a national and international context, in collaboration with many industrial partners. The steps taken in this continuous development have been supported by CATO-1, CATO-2, the EOS consortium CAPTECH and the EU projects CACHET and CAESAR.
These project have taken an efficient idea on paper to a bench-scale demonstration in which the tentative assumptions made in the initial phases have turned out to be well defined with the technology now showing not only paper efficiency, but demonstrated experimental efficiency. SEWGS has shown itself to be a platform technology for syngas processing within both the power and chemical sectors. In the former sector both the Natural Gas Combined Cycle (NGCC) and the Integrated Gasification (IGCC) application have been assessed extensively. In particular in the IGCC, SEWGS has been shown to have clear benefits over conventional pre-combustion capture technology. Another promising application of the SEWGS technology is power production from blast furnace top gas. Therefore, SEWGS development within CATO-2 has been focussed on 1) IGCC-SEWGS) and 2) Blast Furnace Gas (BFG) fuelled combined cycles such as the IJmond 1 power plant. Technoeconomic assessments indicate there is a reduction in costs for CO2 capture of 40% compared to base case technologies for BFG applications. This aligns with the main objectives of SP1 in the CATO-2 to reduce the costs of capture, an economic barrier to CCS implementation.
For the SEWGS development ECN has two unique process development units that were financed by the CO2 Capture Project consortium (CCP-2, funded by 7 major oil companies) with matching funding from CATO1 & 2. Test equipment used: Single Column (left) and Multi Column unit (right) at ECN. Recently, a new family of materials has been discovered for use in the SEWGS with significantly improved performance compared to the reference materials The reference material called ALKASORB was used to deliver the proof of concept of the SEWGS technology and in long term testing under relevant conditions in the two PDU’s. The improvements that considerably enhance the performance of the SEWGS system are two-fold: i) the capacity for CO2 of the sorbent has almost doubled ii) the materials have been shown to maintain performance under very low steam conditions. The new class of materials have only been tested in small batches for several hundred cycles under model conditions. Compared to the reference ALKASORB sorbent there are still several stages of development to be passed before these material can be validated for use in SEWGS cycles in a pilot unit. Issues that need to be addressed on the material side include:
- Verification of mechanical stability under full cyclic conditions
- Interaction with sour components other than CO2
- Confirmed water-gas shift activity
- Optimisation of compositional range of the new material class
- Optimisation of pellet preparation method
On the technology side there are also several issues that need to be addressed concerning the implementation of the new material in the various applications identified for which this platform technology could be applicable:
- Improvements in overall system performance due to the improved material
- Improvements in SEWGS cycle efficiency due to improved material
In blast furnace gas applications, the reference ALKASORB sorbent has been tested in cycles that show improved capture efficiency, but the new class of materials has yet to be tested under such robust conditions. Using the new family of materials will result in a smaller footprint of the SEWGS unit, which will reduce the auxiliary steam input for regeneration of the sorbent materials and lead to higher capture efficiencies (in terms of both thermodynamic efficiency and amount of CO2 captured) compared to state-of-the-art solutions. In the STEP-UP project Kisuma Chemicals BV (sorbent manufacturer), Tata steel (user) and ECN (technology owner) work together to further improve the economic feasibility of the SEWGS technology i.e. reduce the costs of CO2 avoided in which providing proof of the viability of the new sorbent material is the next step. The new sorbent will be validated in the PDU’s with 2000 cycles under conditions representative for a BFG syn gas stream. The sorbent will be produced at an industrial production site, at the tonne scale, such that further scale-up issues will no longer be expected. The production process will be optimised in terms of producing a material with the optimal Mg-Al-K composition, and pellet density and porosity.
The techno- economic assessments will conclude the STEP-UP project. Costs estimations of a full scale SEWGS-1500 unit, the long term performance data of the sorbent, the mass production sorbent costs etc. will be used as input. The SEWGS-1500 unit is a single train designed to capture 1500 tonne CO2/day. This will all lay the groundwork in preparation of a pilot-scale demonstration in the near future.