Research into material recovery techniques and the utilisation of solid fuels in an industrial context

This thesis covers two main areas of investigation, the production and recovery of process dusts formed in the steelmaking industry, and secondly the study of the utilisation of coals for injection in a blast furnace and during co-firing with biomass in a utility boiler. These are linked by an overall aim to research the environmental and economic sustainability of industrial processes through increased process efficiency, decreased environmental impacts, and increased recovery of waste. It comprises a summary of the research contribution from six first-author peer reviewed journal publications and nine supplementary contributions for the submission of a PhD by published works. Process dust research was carried out on a 300t vessel requiring the development of a novel industrial scale isokinetic sampling methodology, capable of sampling frequently enough to measure and analyse mass flow profiles and zinc mass contamination profiles at a higher level of detail than in prior research. A new understanding of the impact of inprocess iron ore additions and waste oxide additions were correlated with additional dust and zinc mass peaks. This methodology was also used to prove that a new process change involving a galvanised scrap holding stage could be applied to successfully reduce the zinc contamination. Research into a modified hydrometallurgical leaching method for blast furnace dust gave high zinc extraction, but with low iron extraction, by the novel utilisation of the substituent group effect of carboxylic acid leaching. Further research also identified that improvements in the zinc extraction selectivity could be achieved using a non-aqueous solvent to utilise the Lewis acid effect. In terms of solid fuel utilisation, factors such as the physical properties, cost, and availability result in end users blending coals to meet their needs. The use of higher volatile matter coals was found to benefit blends with low volatile coal in the context of the blast furnace, but research conducted on a 500MW utility boiler showed that carbon monoxide and dust levels increase. Although grinding coals to a pulverised specification has been proved to benefit utilisation, new findings show that the additional grinding alters the surface chemistry and reactivity of many coals and was related to reduced burnouts compared to some larger particle size specifications. Research on industrial processes is challenging, but these papers aim to address sustainability issues in terms of the efficient use and recovery of materials.