Science

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  • (2022) Biswal, Smitirupa
    Thesis
    The iron and steel industry is one of the prominent industrial sectors in the world since steel is a vital material with a wide range of applications in our daily lives. There will be a gradual improvement in the living standards, infrastructure and economic growth of developing nations with time. All these will necessitate the demand for steel, and it is essential to meet the same but in an environmentally friendly and sustainable way. The ferrous industries are associated with various issues like extensive greenhouse gas emissions, energy-intensive processes and heavy reliance on fossil fuels and natural resources. At the same time, concern regarding waste generation and its management is taking up the momentum and calls are being made for recycling and green recovery. Reuse of waste materials in the manufacturing process could make the industries circular economy resilient. The Ph.D. research work is based on this notion and involves a novel approach of utilizing a bio-based waste material called spent coffee grounds (SCGs) for application in ironmaking. The research work involved the use of SCGs to produce iron from iron oxide as an alternative to coal/coke. Thermal transformation study of SCGs were carried out in the temperature range of 400 °C to 900 °C. The transformed sample obtained at 400 °C, called T-SCGS (transformed-spent coffee grounds), was preferred for the reduction study in the research work due to presence of optimal amount of volatile matter and fixed carbon. This observation was further validated with better high temperature reduction performance in comparison with metallurgical coke (MC) and SCGs (as-received form). Detailed study regarding solid-state (800-1200 °C) and molten-state (1550 °C) reduction processes were carried out with no-flux and fluxed composite pellets of iron oxide and T-SCGs. Use of T-SCGs for iron recovery from electric arc furnace (EAF) slag was also studied. T-SCGs have both hydrogen and carbon in their molecular structure and reaction of in-situ hydrogen with iron oxide will release the by-product of H2O therefore, helping in reduction of CO2 emissions. Hydrogen is known to be a kinetically better reducing agent than carbon thus, improving reaction efficiency and decreasing energy consumption. Overall, the waste source of SCGs when transformed to a suitable form has the potential to be used as an alternative to coal/coke for sustainable iron production such as in solid-state direct reduction as well as smelting reduction processes and also aiding in the novel concept of circular economy.

  • (2022) Nur-A-Tomal, Md. Shahruk
    Thesis
    Plastic revolutionised the world, but meantime generates a substantial amount of waste plastics. However, plastics are generally non-biodegradable and hence remain in the environment for a very long time. Most plastics are not discarded properly, these wastes either end up in the landfills or left in the environment which can end up in water systems including oceans. Alternatively, plastics are burned to remove from premises or to recover energy. Today it is well established that if waste plastics are not deal properly, they can pose a great risk to both the people and the environment and at the same time a lot of valuable materials will be lost. However, only a small percentage of waste plastic is currently recycled due to the limitations of recycling and reprocessing technology, which requires massive infrastructure and normally is not economically feasible and environmentally sustainable. To overcome these challenges, several easy-to-operate and less cost incentive processes have been evaluated throughout this PhD project. This project first began by investigating the effect of reprocessing on polymer, which is important to develop efficient and effective recycling processes. At the next step a simple process that required fewer steps has been developed to utilise waste hard plastics as feedstock to produce new plastic products whilst retaining the original properties and colour of input waste plastics. Then, two novel processes have been demonstrated for another two types of problematic waste plastic (fishing net and flexible plastic packaging). In the final part of this research, three-dimensional (3D) printing, an advanced method of manufacturing, has been employed to transform waste plastics from toys into products. All produced plastics from the proposed methods showed good mechanical performances as virgin material. Life cycle assessment indicated that the processes could reduce greenhouse gas emission, fossil fuel depletion and ecotoxicity. Considering the conclusions of this project, different methods demonstrated in this thesis can manage and transform a wide range of waste plastics (from hard to soft) into high-quality plastics. They are not limited to the case studied waste plastics rather they have the potential to deal with other similar kinds of waste plastic. Overall, this research will create value for waste plastics, and in turn, speed up their collection and recycling.

  • (2023) Hemati, Sepideh
    Thesis
    The increasing production and disposal of end-of-life vehicles (ELVs) pose considerable environmental challenges due to the pollutants emitted throughout their lifecycle. Automotive shredder residue (ASR), the residual waste after de-pollution and dismantling of automobiles, contains diverse materials, including valuable metals, requiring economic recycling and efficient recovery techniques. This research evaluates an innovative route of selective thermal transformation of ASR and waste glass to produce nano-silicon carbide (SiC), a metallic fraction as byproducts. Furthermore, it focuses on recovering metal values by thermal transformation of ASR into high-value products. The study comprehensively investigates the thermal transformation processes to extract metals and produce valuable metallurgical compounds from ASR. The research highlights the economic and environmental benefits of the proposed transformation process, paving the way for sustainable recycling practices of ASR and reducing reliance on primary sources. The kinetics of SiC synthesis from ASR and waste glass were assessed, and the insights demonstrated significant energy savings compared to traditional methods. The understanding of the SiC formation kinetics from ASR and waste glass served to be helpful in examining the nature of the reaction and controlling variables determining the rate kinetics of decomposition of the reactant. In addition, a potential method of utilising metallic fractions derived from ASR in micromanufacturing is explored. The metallic fraction, rich in Fe, Cu, Al, Ca, and Si, was used as the feed material to develop a metallic alloy for contemporary applications. The valorisation route revealed promising results of recovering the metal fraction from ASR, thereby facilitating the development of different alloys with remarkable properties from secondary sources.