Assessment of the Environmental Impact of Residual and Critical Elements in Steel:Removal, Recovery and Substitution

SUSTAIN （www.sustainsteel.ac.uk）是斯旺西大学、华威大学和谢菲尔德大学与英国钢铁行业合作的一个令人兴奋的3500万英镑的合作项目。该项目将与SUSTAIN“零废物、碳中和钢铁制造”中心的第一个重大挑战相关联，该中心的目标是使钢铁制造脱碳，因此与先进金属DTC保持一致。在钢铁生产中大幅增加废钢的使用已成为英国钢铁工业的一项战略决策。这是由政府在2050年之前将工业二氧化碳排放量减少80%的强制性目标推动的，也是由当前的废钢供应过剩和未来十年预计的数量增长推动的。与这种方法相关的挑战很多。废钢使用量增加带来的第一个挑战是从废钢中遗留下来的杂质（残余元素），这些杂质会严重影响钢的加工和钢产品的使用性能。这意味着目前大量的废钢被降级为低等级的钢铁产品。废料与其他材料混合时也会造成问题，其化学成分可能因其来源和先前加工的程度而异。去除残留元素的机制确实存在，但这些机制可能是能源密集型的。正在提出新的清除机制，但这些机制对环境的影响尚不确定。在炼钢过程中使用废钢引起的第二个重要问题（尽管这个问题并非电炼钢实践所独有）是从产品寿命结束时或在制造过程中回收关键元素。从资源效率、供应链和成本的角度来看，如果元素被归类为关键或战略重要性，这个问题就会变得更加重要。最后，从供应链、经济和道德的角度考虑，钢铁产品中这些关键或具有重要战略意义的元素的替换是必须的。许多钢铁产品都有潜在的替代品和替代品，但在做出充分知情的决定之前，量化使用这些替代品对环境的影响至关重要。因此，该项目的主要目的是评估(i)经济上可行的去除机制和关键残留元素（如锡、铅、镍、锌和铜）的限制；（ii）残留和/或关键元素（如铌）回收机制的环境影响；（iii）替代钢铁产品中的残留和/或关键元素的环境影响。评估这类影响的最广泛使用和接受的技术是生命周期评估（LCA）。生命周期分析是一种系统的技术，用于分析产品在整个生命周期链的各个阶段的环境因素和潜在影响。使用LCA方法，本研究将评估去除残余元素的策略，评估在钢的生命周期中保持合金元素“在循环中”的策略，例如通过更好地分离废料和采用技术进步来提高回收过程中关键资源的产量/回收率，并评估其在资源效率背景下的潜力。最后将评估替代或替换一些钢铁产品中关键元素的影响。收集有关当前（和预测）钢铁产品再循环率的数据将是该项目的一个重要组成部分，并将采用全生命周期方法来得出切实可行的结论，并可对资源效率高的钢铁工业的绩效作出积极贡献。

SUSTAIN (www.sustainsteel.ac.uk) is an exciting £35M collaborative project between the Universities of Swansea, Warwick and Sheffield working in partnership with the UK steel industry. This project will link to the first grand challenge in the SUSTAIN Hub of 'Zero Waste, Carbon Neutral Steel and Ironmaking' with the aim of decarbonizing iron and steel manufacturing, and so aligns to the Advanced Metallics DTC.Significantly increasing the use of steel scrap in steel production has become a strategic decision for the UK steel industry. This is driven by the government compulsory target of reducing CO2 emissions by 80% before 2050 for industry and is motivated by the current over-supply of steel scrap and its projected growth in quantity over the next decade. There are a number of challenges associated with this approach. The first challenge for the increased use of scrap is the impurities (residual elements) inherited from the steel scrap that can strongly influence the processing of the steel and the in-service properties of steel products. This means that a lot of current scrap recycled steel is down-cycled to lower grade steel products. Scrap can also cause problems when it is mixed with other materials, and its chemical composition can vary depending on its origin and the degree of previous processing. Mechanisms for removal of residual elements do exist, but these can be energy intensive. New removal mechanisms are being proposed, but the environmental impact of these are uncertain.The second important issue arising from the use of scrap in the steelmaking process (although this problem is not unique to electric steelmaking practices) is the recovery of key elements from a product at the end of its life, or during the manufacturing process. This issue becomes even more important from a resource efficiency, supply chain and cost perspective if the element is classed as critical or strategically important. Finally, replacement or substitution of these critical or strategically important elements in steel products is something that will be required for a number of supply-chain, economic and ethical reasons. There are potential replacements and alternatives for many steel products, but quantifying the environmental impact of using these replacements is vital before fully informed decisions can be made. The principal aims of this project therefore are to assess (i) the economically feasible removal mechanisms and limits for key residual elements such as tin, lead, nickel, zinc and copper(ii) the environmental impact of recovery mechanisms for residual and or critical elements such as niobium(iii) the environmental impact of substituting residual and/or critical elements in steel productsThe most widely used and accepted technique to assess this type of impact is Life Cycle Assessment (LCA). An LCA is a systematic technique used to analyse the environmental aspects and potential impacts associated with a product at all stages across the life cycle chain. Using LCA methodologies, this study will assess strategies for removing residual elements, assess strategies for keeping alloying elements 'in the loop' through the life-cycle of steel, by for example better segregation of scrap and the adoption of technical advances to improve the yield / recovery of key resources during the recycling process, and assessing their potential in a resource efficiency context, and finally will assess the impact of substituting or replacing critical elements in a number of steel products. The collection of data e.g. on current (and predicted) recycling rates of steel products will be an important element of the project and a full life cycle approach will be adopted in reaching conclusions that are practical and can make a positive contribution to the performance of a resource efficient steel industry.