Novel and efficient microwave plasma furnace for processing and syngas production

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ssues with the scale up of atmospheric pressure Microwave (MW) Plasma Processing, achieving high efficiencies and longevity of components, was identified by a Lancaster Chemical Engineering PhD project using MW plasma torches for the gasification of organic waste.Inspired by STFC funded research, principally Cockcroft Institute grants (2009-2022) STG008248/1 and ST/P002056/1, a solution was proposed by the Lancaster RF accelerator engineers allowing plasmas to be struck in large diameter unlined Nickel steel pipes with greatly reduced wall losses and no tendency for the plasma to track back to the generator. Proof of principle was demonstrated by a subsequent undergraduate project. A patent application has been made. The innovation is to use a mode converter to generate a low loss transverse electric mode where the electric field is parallel to the walls. This allows a non radiating cut to be made in the waveguide that allows the walls to find their own potential limiting electron diffusion to the walls. The cut also stops the plasma tracking back to the generator.The initial experimental work with a fully energised plasma, was not initially planned as part of the undergraduate project, the project was to develop the mode converter and undertake cold testing. As the mode converter worked perfectly, we borrowed equipment to undertake a hot test. The available test time was only a few hours and as the microwave choke for the gap has not been developed, it was deemed that the level of microwave leakage was such that the experiment should be terminated. The plasma was run for about 30 minutes, it was very stable and the bare aluminium walls for the plasma vessel did not become excessively hot indicating low losses to the walls.In this project we plan initially to complete the development of the choke so the plasma can be run without microwave leakage. We will then characterise the plasma and understand how it can be used to process a range of feedstocks. Industrial companies will be sort who may want to use the technology and will be invited to submit samples for investigation. The aims might be for gasification, waste destruction, plasma synthesis or surface modification. Gasification of waste is likely to be an important technology targeting net zero greenhouse gas emission. We believe that microwave plasma gasification offers an advantage for certain toxic waste streams.Optimisation work will also be undertaken.