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Title: Life cycle assessment and the design of a thermal cracking process for the reuse of mixed plastic waste
Author: Gear, Matthew
ISNI:       0000 0004 7431 5654
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2018
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It is well accepted that the technical, financial and environmental performance of a chemical process is largely determined during design. Therefore, the development of tools that integrate environmental considerations would enable the design of more environmentally friendly processes at a lower cost. This research investigates how Life Cycle Assessment (LCA) can be applied at any stage in the design process to produce useful information for design, not just after the plant is operating, which is the norm for LCA. The tools have been applied to the development of a novel process (the RT7000): thermal cracking of mixed plastic waste to produce several hydrocarbon products with the potential to displace crude oil, naphtha, or refinery wax or be used as a fuel. To allow LCA to guide the design process, a toolkit methodology was developed including comparisons of design changes, hotspot analysis, identification of key impact categories, environmental break-even analysis, and decision analysis using ternary diagrams. The results of applying these tools justified continuing with the development by confirming that the novel process is likely to be a better environmental option than landfill or incineration. At the later stages of design, advanced tools such as process simulations become attractive and allow a more accurate estimation of material and energy flows. A simulation of the RT7000 in Aspen Plus® was developed that provided data for a wide range of feed compositions. The RT7000 continued to have lower environmental impact to incineration offering a saving equivalent to 969-1305 kgCO2/tonne plastic processed. It was also ascertained that variation in feed composition does influence environmental performance, but not enough to affect the outcomes of decision making. The general approaches used in this work to assess the RT7000 should be applicable to the development of any new process. Benefits and insights similar to those obtained in the case study can realistically be expected when these methodologies are applied to any new processes. Therefore the results have been published in the Journal of Cleaner Production (Gear et al., 2018).
Supervisor: Thorpe, Rex ; Sadhukhan, Jhuma ; Clift, Roland ; Seville, Jonathan Sponsor: EPSRC ; Recycling Technologies Ltd
Qualification Name: Thesis (Eng.D.) Qualification Level: Doctoral