My colleague Kyle Nicol and I recently had the opportunity to visit the Pilot-scale Advanced CO2-Capture Technology (PACT) facility near Sheffield, which forms an important part of the UK CCS Research Centre. Set up in 2012 with government support (via DECC/UKCCRSC/EPSRC), the PACT facilities are a collaborative activity between a number of UK universities, utilities, and manufacturers to conduct carbon capture research at the pilot-scale, forming an important bridge between the lab and industrial-scale projects. Besides the core facility in Beighton, two satellite sites are operating at Cranfield and Edinburgh Universities, all under the direction of Leeds University’s Professor Mohamed Pourkashanian.
Also of Leeds University, Dr Bill Nimmo, whom I first met at the OCC3 oxyfuel conference in Spain, was kind enough to show us around the site. The core facility houses a post combustion capture plant, a 330kW CHP gas micro turbine, and a 250 kWt pulverised fuel combustion rig which can also operate in oxyfuel mode. Flue gases fed to the post combustion plant can be taken from the turbine or the solid fuel rig, or even synthetically generated from cryogenic tanks stored onsite, allowing simulation of flue gas compositions from a given power plant or research on the impact of individual species. Using a standard solvent, the capture plant can remove up to one tonne of CO2 per day from these gas mixtures, but the rig has primarily been used for testing and benchmarking the increasing number of designer capture solvents being produced. The process consists of an initial quench and an alkaline scrub for SOx removal, followed by contact with the capture solvent in an adsorption tower filled with packing which enhances the gas-liquid interaction. Having selectively reacted with the CO2 in the flue gas, the solvent is pumped to a desorber column and thermally regenerated to release a nearly pure CO2 stream.
With my review of recent developments in oxyfuel technologies soon to be published, the oxyfuel capability of the combustion rig was of particular interest to me. Using a downsized version of a commercial Doosan low NOx burner, the rig can also fire natural gas, biomass, or blends of solid fuels, and is currently being used for oxyfuel biomass tests as part of the EPSRC’s Biocap project. Flue gas from the rig is filtered hot before being recycled back to the burner, while pure oxygen is added in controlled proportions to the primary, secondary, and overfire air streams. This pilot is also able to make valuable use of synthesised flue gases, which can mimic different flue gas recycle conditions with varying temperature or levels of water vapour. As flame stability and heat transfer characteristics are a key concern in oxyfuel combustion, the rig is equipped with 2D and 3D cameras and heat flux probes which can produce detailed experimental data for validation of CFD models.
Running remarkably quietly during our visit, the gas turbine is a commercial ‘Turbec’ unit which can generate around 100 kW of electrical power and 160 kW of heat. A principal challenge with post combustion capture from gas turbines is the low concentrations of CO2 they produce, so new tailor-made solvents are being tested on the unit, as well as trialling of exhaust gas recycle which also helps to push up the CO2 concentration.
Besides a number of academic projects, the research conducted at the site can range from industrial contracts and collaborations to technical consultancy and operator or student training. The level of interest and number of research applications attracted by the facility in the relatively short time it’s been operational are an encouraging sign for CCS research in the UK, and knowledge gained from these units will play a role in establishing CCS as a commercial reality in the UK and worldwide.
Further information can be obtained from Dr Kris Milkowski, PACT business development manager, T: +44 (0) 113 343 7626 M: +44 (0) 7785708392 E: [email protected]