STEP-UP: SEWGS Technology platform Upgrade
Sorption-Enhance Water-Gas Shift (SEWGS) 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 temperatures. From its very conception, it has been clear that the technology has the potential to deliver very high performance in terms of efficiency, and to outperform existing state-of-the-art technologies.
The stepwise approach to the development of the process took place within both a national and international context, in collaboration with many industrial partners. The steps have been supported by CATO-1, CATO-2, the EOS consortium CAPTECH, and the EU projects CACHET and CAESAR.
This project took an efficient idea on paper to a bench-scale demonstration level. The tentative assumptions made in the initial phases turned out to be well defined, with the technology now showing not only paper efficiency, but also 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, both the Natural Gas Combined Cycle (NGCC) and the Integrated Gasification (IGCC) application have been extensively assessed. In the IGCC in particular, 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 focussed on: 1) IGCC-SEWGS, and 2) Blast Furnace Gas (BFG)-fuelled combined cycles, such as the IJmond 1 power plant. Technoeconomic assessments indicate that there is a 40% reduction in the costs of CO2 capture compared to base case technologies for BFG applications. This aligns with the main objective of SP1 in CATO-2 to reduce capture costs, which were an economic barrier to CCS implementation.
For the SEWGS development, ECN had two unique process development units that were financed by the CO2 Capture Project consortium (CCP-2, funded by seven major oil companies), with matching funding from CATO1 & 2. The test equipment used was a Single Column (left) and Multi Column unit (right) at ECN.
A new family of materials was recently 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 CO2 capacity of the sorbent almost doubled, and 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 ALKASORB reference sorbent there are still several stages of development that must be passed before these materials can be validated for use in SEWGS cycles in a pilot unit. Issues that need to be addressed on the materials side include:
- Verification of mechanical stability under full cyclic conditions
- Interaction with acidic components other than CO2
- Confirmed water-gas shift activity
- Optimisation of the compositional range of the new material class
- Optimisation of the pellet preparation method
On the technology side, there are also several issues that need to be addressed. These concern the implementation of the new materials 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 ALKASORB reference 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) are working together to further improve the economic feasibility of the SEWGS technology, i.e. to reduce the costs of avoided CO2, and providing proof of the viability of the new sorbent material is the next step. The new sorbent will be validated in the PDUs over 2,000 cycles under conditions representative for a BFG syngas stream. The sorbent will be produced at an industrial production site at tonne scale, so that no further scale-up issues are 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.
Technoeconomic assessments will conclude the STEP-UP project. Costs estimations of a full-scale SEWGS-1500 unit, long-term sorbent performance data, and mass-production sorbent costs, etc. will be used as input. The SEWGS-1500 unit is a single train designed to capture 1,500 tonnes of CO2/day. This will lay the groundwork in preparation for a pilot-scale demonstration in the near future.