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Thermal kinetics study of paper and plastic waste gasification

Al-Moftah, Ahmad Mohamed S H 2022. Thermal kinetics study of paper and plastic waste gasification. PhD Thesis, Cardiff University.
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Abstract

This thesis focuses on studying the thermal kinetics behaviour of Subcoal™ gasification using fixed bed thermogravimetric analysis (TGA) and bubbling fluidised bed gasifier reactor (BFBGR). Applying this fundamental study to a modern scenario, the current situation of Municipal Solid Waste (MSW) management and the environmental impact of utilising Solid Recovered Fuel (SRF) gasification technology to produce more environmentally friendly electricity in Qatar is investigated. Novel kinetic parameters of Subcoal™ pyrolysis, carbon dioxide (CO2) gasification, and combustion at various heating rates without catalyst were obtained in TGA using a model free method. The TGA curves showed that the thermal degradation of Subcoal™ comprises three main processes: dehydration, devolatilisation, and char and ash formation. Nevertheless, substantial variance in activation energy (E_a) was noted between the four stages of thermal decomposition of Subcoal™ on all experiments. The results showed that Kissinger-Akahira-Sunose (KAS), Tang (TA), and Starink (ST) are more accurate mathematical methods than Ozawa–Flynn–Wall (OFW) method. The effect of olivine and dolomite loadings on kinetic parameters of Subcoal™ pyrolysis, CO2 gasification and combustion has been investigated using Coats-Redfern (CR) model fitting method. Among the 19 mechanism models, second order chemical reaction model (G15) was the best linearity for pyrolysis, while third order chemical reaction model (G14) was the best linearity for CO2 gasification and combustion with dolomite 15 wt.%. First life cycle assessment of SRF air gasification was also conducted using the Recipe2016 model considering five environmental impact categories and four scenarios in Qatar. It considered alternative methods to reduce MSW landfills and produce sustainable energy in line with Qatar’s national vision for 2030. The introduction of the SRF gasification reduced climate change-causing emissions by 41.3% because of production of renewable electricity. Thermal gasification behaviour of Subcoal™ pellet and pulverised pellet were also investigated in BFBGR. The producer gas parameters were used to investigate the performance of gasification at different conditions. The findings showed that the increase in temperature enhances the performance of gasification of both SubcoalTM types. Moreover, the optimum gasification temperature tested for SubcoalTM was 750 ºC at equivalence ratio (ER)=0.15. In terms of catalyst effects, the addition of dolomite showed better performance in catalysing the gasification reactions compared to olivine under the same conditions. The Pulverised Subcoal™ pellet performed better than Subcoal™ pellet for gasification due to a shorter reaction time. The Subcoal™ pellet size reduction enhances the conversion efficiency and reduces char formation.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Biomass, Gasification , Qatar National Vision 2030, Kinetics , Life cycle assessment, Fluidised bed gasifier reactor ,
Date of First Compliant Deposit: 3 August 2022
Last Modified: 05 Jan 2024 06:18
URI: https://orca.cardiff.ac.uk/id/eprint/151656

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