Highly Efficient Generation of Energy from Waste and Biomass Using Microwave-Induced Plasma Gasification

Vecten, Simon (2021) Highly Efficient Generation of Energy from Waste and Biomass Using Microwave-Induced Plasma Gasification. PhD thesis, UNSPECIFIED.

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Abstract

It is urgent to develop sustainable solutions enabling the reduction of greenhouse gases emissions in order to mitigate the impact of climate change. In accordance with this, the present PhD thesis investigates the energy generation from biomass and waste in a microwave-induced plasma gasification system. The performance of the proposed process is investigated by means of modelling and empirical studies. A model developed in Aspen Plus highlights the benefit of plasma utilisation and its high energy density, which enables the supply of all the necessary energy for complete feedstock conversion with low inert gas dilution. The process can theoretically achieve high cold gas efficiency exceeding 76% whilst generating a syngas with high lower heating value in the range 9-12 MJ/Nm3, and that for the three plasma working gases studied (air, H2O and CO2). Experimental characterisation of the microwave – induced plasma torch demonstrates that it can generate an ideal environment for gasification with elevated temperatures and the presence of chemically reactive species. The thesis presents for the first time the experimental gasification of biomass in a moving-bed reactor with pure steam microwave-induced plasma at laboratory scale. Excellent results are achieved with near complete carbon conversion efficiency reaching 98.4% and the total biomass energy recovery in syngas. The syngas generated under pure steam plasma is rich in hydrogen with volume concentration exceeding 60% and presents a high lower heating value in the range 10.5-12 MJ/Nm3, which is in agreement with modelling results. The proposed microwave-induced plasma gasification process has the potential to efficiently convert biomass and waste into high quality fuel gas, which can then be used for fuels or electricity production. The process could become one of the numerous solutions for the substitution of fossil fuels and could find a place in the needed transition to a carbon neutral economy.