Why is this research needed?
BECCS means bio-energy with CCS, which involves growing and harvesting a crop like miscanthus or willow (for virgin biomass). Biowastes like waste wood could also be used, in order to then burn and generate energy from. The CO2 is captured from the flue gases. This means that the CO2 that was absorbed during the growth of the plant is captured and stored, meaning that low-to-zero emissions are achieved, and potentially net negative emissions are possible, which can sigifncatly aid in the decarbonisation of the energy sector.
BECCS is critical for achieving UK and global carbon reduction commitments and the Hub Bio-CAP-UK project has demonstrated the importance of practical trials to build industrial confidence in the technology. Using the PACT facilities we have investigated a range of biomass fuels coupled with different CCS technologies, including post-combustion and oxy-fuel methods. This is vital for scaling up projects so they can be used on a larger, commercial scale and make a real world impact on emissions reductions. This research project investigates the impurities in the fuels that can detrimentally impact the capture process and will devise strategies to limit the adverse effects these can have.
What is this research investigating?
Pilot testing will performed using the TERC facilities to demonstrate, for greenfield applications, the potential of oxy-fuel capture technology for increased waste fuel flexibility, and, for retrofits, process integration at the pilot scale. Oxy-fuel technologies cover a range of options that enable biomass combustion in a N2-free environment – we focus on oxy-combustion, where the fuel is fired in an O2-CO2 mix (an oxygen-enriched environment) rather than in air, which means there is little/no nitrogen dilution of the flue gases. The results in an easier clean-up process, mostly condensing out moisture and removing trace species. Individual types of waste fuels are not likely to be available in vast quantities in specific regions and transporting these fuels large distances is often not economical. Waste fuel flexibility therefore refers to the efficient and practical use of different types of waste materials in the same plant, e.g. cofiring, fuel-switching, etc. Ideally this would be non-treated wood and wood products, although chemically-treated and processed wood products may be used, depending on the contamination levels.
This will utilise our 240 kW grate-fired boiler burning Solid Recovered (waste) Fuel (SRF) integrated with our onsite 150 kW solvent-based PCC plant, both of which are fully instrumented. Extensive analysis of combustion gases, metal aerosols and particulate formation will identity key species and pollutants from the combustion process and their impact on the solvents and operation of the solvent-based carbon capture plant in waste-to-energy (WtE) conditions.
Data and samples from previous projects by the applicants (for example, Bioenergy Supergen, Bio-Cap-UKCCSRC) will inform the tests under a range of real operating conditions (air/oxy-firing) to evaluate the impact of alkali/transition/heavy metals and other species on:
• the oxidative degradation of CO2 capture solvents and corrosion within the capture plant, initiated, catalysed and aggravated by transition metal carryover and
• possible contamination of the high-purity captured CO2 stream with a range of inorganic elements.
What does the research hope to achieve?
This research will enable better understanding of the partitioning of elements from the combustion of these waste fuels under a range of realistic pilot scale conditions, leading to the formation of comprehensive and novel datasets on the fates of specific elements.
The data will enable us to determine where these species end up (for example, in the ash vs. in the flue gas) and therefore quantify their impacts in terms of operation for both the combustion plant (deposition in terms of slagging/fouling) and the capture plant (the solvent degradation mentioned above). This will in turn inform the mitigation methods that may be required, which could include fuel pre-treatments to remove key problematic species (including washing/leaching, hydrothermal carbonisation or steam explosion), additional flue gas treatments (such as high-efficiency filtering of sub-micron particles that are enriched with metals) or modifications to the operation of either/both parts of the plant. This would aid the scale-up and deployment of the technology so such technical problems and operational issues can be identified and dealt with at a pilot-scale, prior to commercial roll-out.