New Methods for ferrous raw materials characterization in electric steelmaking

425 p.In the siderurgical sector, the steel scrap is the most important raw material in electric steelmaking,contributing between 70% of the total production costs. It is well-known how the degree of which thescrap mix can be optimized, and also the degree of which the melting operation can be controlled andautomated, is limited by the knowledge of the properties of the scrap and other raw-materials in thecharge mix.Therefore, it is of strategic importance having accurate information about the scrap composition of thedifferent steel scrap types. In other words, knowing scrap characteristics is a key point in order to managethe steel-shop resources, optimize the scrap charge mix/composition at the electric arc furnace (EAF),increase the plant productivity, minimize the environmental footprint of steelmaking activities and tohave the lowest total cost of ownership of the plant.As a main objective of present doctoral thesis, the doctorate will provide new tools and methods of scrapcharacterization to increase the current recycling ration, through better knowledge of the quality of thescrap, and thus go in the direction of a 100% recycling ratio. In order to achieve it, two main workinglines were developed in present research. Firstly, it was analysed not only the different existingmethodologies for scrap characterization and EAF process optimization, but also to develop new methodsor combination of existing, Secondly, it was defined a general recommendations guide for implementingthese methods based on the specifics of each plant

Spent coffee grounds (SCGs): Thermal transformation and application in sustainable iron production

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

Copper contamination in end-of-life steel recycling, developing a new strategy from million-tonnes to milligrams

Increasing the share of scrap-based steel production is necessary to achieve CO2 emissions targets. However, the quality of recycled steel is compromised by contaminating elements, of which copper is the most pervasive. Copper from wiring and motors entangles with steel fragments during shredding and is not completely removed by magnetic separation. Beyond hand-picking, no commercial process exists for extraction, but copper in solution with steel segregates during hot rolling, causing surface cracking and defects that are unacceptable for high-quality flat products. This thesis characterizes copper in the global steel system, evaluates the energy requirements of possible extraction processes and presents experimental results to aid in the development of an efficient extraction technique. Copper contamination is currently managed by globally trading contaminated scrap to tolerant applications and by dilution with primary steel. An evaluation of copper in the global steel system is needed to develop long-term strategies, and this is presented in the first part of this thesis. The copper concentration of flows along the 2008 steel supply chain are estimated from a range of literature sources and compared with the maximum concentration that can be tolerated in all steel products. Quantities of final steel demand and scrap supply by sector from a global stock-saturation model are used to estimate the amount of copper in the future scrap supply, and the total amount tolerable. Assuming current scrap preparation continues, more copper will enter the steel cycle than can be tolerated by demanded products by 2050. This global constraint will set in sooner if primary production is cut to meet climate mitigation targets. Given the upcoming constraints, improved copper control is necessary. Various techniques for copper separation have been explored in laboratory trials, but as yet no attempt has been made to provide an integrated assessment of these options. The second part of this thesis presents a framework to define the full range of separation routes and evaluate their potential to remove copper, while estimating their energy and material input requirements. The thermodynamic, kinetic and technological constraints of the various techniques are analyzed to show that copper could be removed to below 0.1wt% (enabling the production of high-value flat products) with 5-20% of the melting energy in the electric arc furnace route. The above analysis reveals a promising and under-explored process route: preferential melting of copper from solid steel scrap, which could be integrated into conventional scrap re-melting with little additional energy. Previous investigations show removal of liquid copper is limited by its adherence to solid scrap. In the third part of this thesis, the individual and combined effects of several parameters (steel carbon content, initial surface oxidation and applied coatings) on the wetting behavior of liquid copper are observed with a heating microscope to understand if a process window to enable separation exists. The most significant factor was carbon content. On medium carbon steel substrates, copper spread rapidly, likely due to reduction of the oxide layer by carbon. Non-wetting copper droplets were observed on low carbon substrates in an inert atmosphere. This indicates a possible process window, but further investigation considering diverse, fragmented end-of-life scrap is needed. The scrap supply of all metals is expanding. The multi-scale, interdisciplinary method developed in this thesis could be applied to other metal systems to understand the constraints caused by contamination and identify key areas to develop efficient extraction processes, necessary to conserve resources and reduce CO2 emissions.Cambridge Trust International Scholarshi

Annual Report 2018-2019

It contains the statement of R&D works undertaken, achievement made and the expenditure by the laboratory during the financial year 2018-2019

Recovery of materials from recycling of spent furnace linings

The objective of this research study is to evaluate the technical feasibility of liberating metal entrapped in the spent melting furnace linings obtained from a non-ferrous metal producer and develop an economic technique to recycle all of the materials presently landfilled. Five to six million pounds of spent melting furnace linings are landfilled annually from this non-ferrous producer --Abstract, page iii