ETRIC – Effective Thermal Reclaiming Integrated with Capture
Why is this research needed?
Best Available Technology Reviews for amine post-combustion capture undertaken by the applicants for the Environment Agency have shown that maintaining the capture solvent at stable and acceptable purity levels indefinitely during operation is a key factor for both minimising operating costs and achieving satisfactory environmental emissions.
Two basic approaches exist to maintain a stable solvent composition:
a) Separation of clean solvent from the circulating mixture (reclaiming),
b) Separation of impurities from the circulating mixture (cleaning).
Option b) is often also, inappropriately, called reclaiming, but is clearly a fundamentally different approach and is limited in effectiveness as an extremely heterogeneous mix of impurities will be present after a period of extended operation that no single, or even multiple, cleaning methods are likely to be able to fully remove.
Detailed public domain information suggests, however, that a near-complete cut between clean solvent and impurities in a thermal reclaiming process is feasible for MEA but reported tests have been undertaken over a short period, unlike the actual industrial practice of semi-continuous reclaiming, and at low operating pressures (atmospheric or below). It is known, however, that if the reclaimer is vented into the stripper then all of the energy used can be recovered (i.e. only the higher temperature of the energy results in a, slight, electricity output penalty for a power plant). As a result, such a fully integrated reclaimer can be run at very high rates.
What is not known, however, is the difference in reclaimer performance between atmospheric/vacuum operation and operation at stripper pressure (typically 1-3 barg), nor do direct measurements appear generally to have been reported on the amounts of non-amine components (i.e. degradation products) carried over with the MEA from thermal reclaimers. Instead, measurements are reported for the circulating solvent inventory after a period of reclaiming, which will inevitably lead to uncertainty as to whether the residual amounts of degradation products present were simply not removed because of insufficient time or whether they could not be removed because they co-evaporated in significant quantities with the MEA.
This project will therefore address these questions directly through lab-scale reclaiming tests at atmospheric and elevated pressures using equipment developed in the previous UKCCSRC PCC-CARER project, very importantly using samples from the Tata Chemicals Europe commercial capture plant that will contain entirely realistic mixtures of degradation products from operation. As well as using, for the first time in published laboratory reclaiming tests, samples obtained over a period of up to a year from an operating CCGT plant, the ETRIC project will also capture and characterise the reclaimed MEA directly, allowing trace impurity levels that cannot be reclaimed to be assessed, in addition to characterization measurements on the ‘dirty’ amine being reclaimed and the reclaimer residue.
What is this research investigating?
The objectives of the project are to determine the effect of reclaiming conditions (temperature/pressure/water/caustic/blowdown rates) on thermal reclaimer performance when processing Tata Chemicals Europe used MEA samples, including direct measurements of other impurities coming over with the MEA/water vapour/CO2 product.
Samples and test results will include:
- Existing MEA sample from the Tata Chemicals 100 t/day unit and two future samples, selected based on analysis over the period of the project – these will be characterised to see what is there and if it can all be removed by thermal reclaiming at baseline conditions of atmospheric pressure and 130C
- Results from other reclaiming runs at atmospheric pressure and higher and lower temperatures
- Results from other reclaiming runs at elevated pressure in the range 1-3 barg
- Two-stage reclaiming: possible options for the second (batch) stage following c) above
Deliverables from the project will be reported through the project’s Industrial Engagement Panel, the ongoing BAT Review process, UKCCSRC conferences and other channels, LinkedIn articles, scientific papers and proceedings.
What does the research hope to achieve?
Beneficiaries for this work include:
- Society as a whole – improving CCS operation (by reducing costs from better solvent management and improving environmental performance) will make a significant contribution to achieving net-zero GHG emission targets.
- UK government policy-makers and regulators – this work will make a direct contribution to helping CCS deliver UK domestic greenhouse gas emission targets and the project will communicate directly with the Department for Energy Security and Net Zero CCUS team and the Environment Agency to disseminate the results in the contexts of improved performance and regulation of amine post-combustion capture. It will also contribute to the UK’s international profile on CCS, including through collaboration with international organisation partners such as the International Test Center Network and the UK-China CCS Centre.
- UK industry and its customers for electricity, hydrogen and other decarbonised manufactured products will benefit from well-evidenced research on how solvent reclaiming can better be undertaken with the widely-applicable post-combustion capture amine technology.
- Other researchers will be able to build on the experimental results obtained, for example in improving process model performance.
- Industry and researchers will also benefit from the results and the demonstration of the use of the lab-scale thermal reclaiming equipment and analysis methods.
For industry, the results from the project will indicate the likely trade-offs between reclaiming separation efficiency and solvent recovery levels and reclaimer operating pressure and other parameters (e.g. water feed rates, caustic addition, time/temperature histories). This will allow current and future thermal reclaimer design to be optimised, possibly including through hybrid approaches with a higher-pressure first stage and a lower-pressure second stage.
The results from the project are expected to find immediate application in the Tata Chemicals plant and other small MEA units being planned in the UK and elsewhere, and in plans for larger CCGT capture units using MEA or other thermally reclaimable solvents. As well as Tata Chemicals Europe, the project’s Industrial Engagement Panel has received offers of participation from Bechtel, RWE, SSE and Uniper, confirming the widespread interest in the proposed work, as well as giving a ready and rapid route for dissemination to ongoing UK and overseas CCS deployment using similar gas turbine flue gases.
This research is ongoing. Outputs will be shared below as they become available.