Achieving Carbon Neutrality in the Global Aluminum Industry

In the 21st century, sustainability is widely regarded as the new corporate culture, and leading manufacturing companies (Toyota, GE, and Alcoa) and service companies (Google and Federal Express) are striving towards carbon neutrality. The current carbon footprint of the global aluminum industry is estimated at 500 million metric tonnes carbon dioxide equivalent (CO_2eq), representing about 1.7% of global emissions from all sources. For the global aluminum industry, carbon neutrality is defined as a state where the total “in-use” CO_2eq saved from all products in current use, including incremental process efficiency improvements, recycling, and urban mining activities, equals the CO_2eq expended to produce the global output of aluminum. This paper outlines an integrated and quantifiable plan for achieving “carbon neutrality” in the global aluminum industry by advocating five actionable steps: (1) increase use of “green” electrical energy grid by 8%, (2) reduce process energy needs by 16%, (3) deploy 35% of products in “in-use” energy saving applications, (4) divert 6.1 million metric tonnes/year from landfills, and (5) mine 4.5 million metric tonnes/year from aluminum-rich “urban mines.” Since it takes 20 times more energy to make aluminum from bauxite ore than to recycle it from scrap, the global aluminum industry could set a reasonable, self-imposed energy/carbon neutrality goal to incrementally increase the supply of recycled aluminum by at least 1.05 metric tonnes for every tonne of incremental production via primary aluminum smelter capacity. Furthermore, the aluminum industry can and should take a global leadership position by actively developing internationally accepted and approved carbon footprint credit protocols.     

Applying fundamental data to reduce the carbon dioxide footprint of aluminum smelters

The aluminum smelting process is a strong emitter of CO₂ with three major contributions: that arising from electrical energy generation and its utilization, the process conversion contribution linked with anode consumption and anode production, and the greenhouse gas equivalents of the intermittent perfluorocarbon (PFC) emissions. Fundamental studies of alumina solubility, the electrochemical mechanism for triggering the onset of PFC emissions, and the importance of both mixing and current density on the speed of termination of anode effects, help define better paths for process operation. In conjunction with advising prebake aluminum smelters on process optimization, the authors have successfully tested the differences in theory and practice, and applied fundamentals in the operating environment to change some of the installed control strategies, termination mechanisms, and work practices. These changes have improved performance and reduced the CO₂ footprint. The overall process reductions achieved exceed 2.24 million tonnes of CO₂ equivalents per year in smelters producing less than 3 million tonnes of aluminum per year. Barry Welch is a part-time visiting professor at the University of New South Wales as well as an industry consultant; Martin Iffert is managing director at Trimet Aluminum AG; and Maria Skyllas-Kazacos is Professor Emeritus of Chemical Sciences and Engineering at the University of New South Wales, where she continues to supervise research in aluminum reduction.     

Energy-Efficient and Low-GHG-Emission “Thiometallurgy”

Extractive metallurgy has used free or combined sulfur as both the raw material and the energy material in carrying out economical manufacture of several metals in millions of tons per year quantities over the past century. This has controlled carbon emissions in an unintentional fashion and out of necessity as the ores in many cases have been sulfides to start with. And the benefits of heat generation by the sulfides reacting with oxygen in the process steps have avoided the use of carbon as a fuel in providing the reaction temperatures. In this article, we will show the inherent benefits of “thiometallurgy,” which uses sulfur in the extraction of metals in alleviating CO₂ and water vapor–greenhouse gas (GHG) emissions, as well as its ability to provide a cost-effective energy material solution. Such solutions are not only applicable to existing base metal production but, as the authors will show, also are applicable to newer processes in the production of other metals and chemicals, such as alkaline earth metals, titanium, and to an extent aluminum in an indirect fashion. Iron ores can also be treated with thiometallurgy to meet the ULCOS criterion of ultra-low carbon dioxide steel being studied in Europe. The concept of generating “thiopower” as an alternative energy approach is also introduced by the authors.     

Creating the 2020 Tokyo Olympic Medals from Electronic Scrap: Sustainability Analysis

For the upcoming 2020 Olympic Games, which are to be held in Tokyo, Japan, it has been proposed that recycled metal from electronic waste should be used to create the gold, silver, and bronze medals that will be awarded to athletes from around the world. This work is aimed at exploring the feasibility of this goal, quantifying the required electronic waste, identifying the limiting material constraints, and addressing a selection of sustainability metrics. The results show that 2.5–13.8% of Japan’s available electronic waste would be required to create the medals, depending on the composition of the collected electronics and the processing yields. The environmental benefits from this venture are identified as being a savings of approximately 4.5–5.1 TJ of energy, which is equivalent to CO₂ emissions reductions of approximately 420 metric tons. Additionally, qualitative potential benefits to environment, human health, economic recovery of valuable materials, and supply stability are considered.     

伊朗铝工业

本文对伊朗铝工业的现状和未来发展规划进行了阐述。伊朗是一个资源非常丰富的国家，有许多发展原铝生产的有利条件。目前伊朗有两座电解铝厂和一座产能为30万t的氧化铝厂，原铝的产量达到了16．75万t。2004年伊朗的原铝产量将达到23万t，2005年将达到50万t。伊朗计划在2009年，使本国的原铝产量达到100万t，氧化铝产量达到220万t，生石油焦产量达到40万t。     

Energy-conscious flow shop scheduling under time-of-use electricity tariffs

A time-indexed integer programming formulation is developed and used to identify manufacturing schedules that minimize electricity cost and the carbon footprint under time-of-use tariffs without compromising production throughput. The approach is demonstrated using a flow shop with 8 process steps operating on a typical summer day. Results suggest that shifting electricity usage from on-peak hours to mid-peak hours or off-peak hours, while reducing electricity cost may increase CO₂ emissions in regions where the grid base load is met with electricity from coal-fired power plants. The trade-off between minimizing electricity cost and reducing CO₂ emissions is shown via a Pareto frontier.     

铝材在太阳能光伏发电装备中的应用

太阳能光伏发电是一种再生的无污染的新能源,挤压铝材是制造这种发电装备有竞争力的可选材料,电池板框架、支柱、支撑杆、拉杆等都可以用铝合金制造。太阳能光伏发电装备铝材可用6061、6063、6082铝合金挤压,平均铝材用量约60 t/MW,减排二氧化碳933 kt/MW。我国云南昆明石林太阳能发电站一期已于2010年5月并网发电,亚洲第一大,仅次于美国及西班牙早些时候建成的。截至2009年底,全球太阳能光伏发电系统装机容量已超过1GW。目前妨碍太阳能大发展的主要障碍是造价过高,建设成本约8 000元/kW。     

Hot profile extrusion of AA-6060 aluminum chips

Analyses of energy consumption in manufacturing processes have shown that most of the energy is needed for the production of material such as aluminum or steel and not for further manufacturing steps like forming or cutting. To reduce energy consumption and also a reduction of CO₂ emissions in manufacturing processes, a reduction of the amount of primary material, made from first melting after mining, as well as secondary material, made from melting of recycled scrap material, is needed. In this work, the re-use of aluminum AA-6060 scrap based on milling and turning chips, by direct hot extrusion is presented. To prevent further use of primary aluminum or melting of the chips the process aims at using compacted chips as billet material. The production of the chips as well as the compaction of billets, the extrusion process and the properties of the final profile is presented. In addition to the use of chips based on one alloy the mixture and extrusion of aluminum and SiC particles is presented. The investigations have shown that using billets made of AA-6060 chips can lead to similar mechanical and microstructural properties as using of conventional cast aluminum billets. Investigations on an additional cutting or drilling of the extruded profiles have shown even improved properties due to a reduced chip length.     

铝铸件的世界市场

介绍了铝铸件在世界市场中得到广泛应用的情况;阐明了近期西方市场形势及对未来的预测;指出铝铸造行业如何进行结构调整以适应未来扩大生产能力的要求;预期世界市场中铝铸件的年产量将从近期的不足７００万ｔ上升到２０１４年的１２００万ｔ的水准。     

Technological, Economic, and Environmental Optimization of Aluminum Recycling

The four strategic directions (referring to the entire life cycle of aluminum) are as follows: production, primary use, recycling, and reuse. Thus, in this work, the following are analyzed and optimized: reducing greenhouse gas emissions from aluminum production, increasing energy efficiency in aluminum production, maximizing used-product collection, recycling, and reusing. According to the energetic balance at the gaseous environment level, the conductive transfer model is also analyzed through the finished elements method. Several principles of modeling and optimization are presented and analyzed: the principle of analogy, the principle of concepts, and the principle of hierarchization. Based on these principles, an original diagram model is designed together with the corresponding logic diagram. This article also presents and analyzes the main benefits of aluminum recycling and reuse. Recycling and reuse of aluminum have the main advantage that it requires only about 5% of energy consumed to produce it from bauxite. The aluminum recycling and production process causes the emission of pollutants such as dioxides and furans, hydrogen chloride, and particulate matter. To control these emissions, aluminum recyclers are required to comply with the National Emission Standards for Hazardous Air Pollutants for Secondary Aluminum Production. The results of technological, economic, and ecological optimization of aluminum recycling are based on the criteria function’s evaluation in the modeling system.     

Residues recycling: Reducing costs and helping the environment

The aluminum production chain from bauxite to primary aluminum includes refining using the Bayer process, and smelting through electrolysis. This production chain produces two main solid residues, red mud at the refinery and spent pot lining at the smelter. The use of these residues as raw material for other industrial processes can save large amounts of energy, reduce the overall environmental impact, and even improve the emissions of other processes. This paper shows the results of ten years of co-processing of spent pot lining in the cement industry in Brazil and the efforts to develop technologies to reduce the reactivity and use the red mud as raw material for several different processes. This approach, although engineering intensive, can reduce C0₂ emissions and save huge amounts of wasted energy in transport and processing when compared with dedicated recycling or neutralizing processes.     

Discrete lot-sizing and scheduling problems considering renewable energy and CO<Subscript>2</Subscript> emissions

Scheduling research increasingly focuses on reducing carbon emissions. Curbing carbon emissions during production and operation processes based on renewable energy sources is thus of priority concern. Therefore, this study analyzes two variants of the discrete lot-sizing and scheduling problem (DLSP): (1) a bi-objective DLSP in which renewable energy is considered and earliness tardiness and CO₂ emissions are minimized simultaneously; (2) a DLSP in which renewable energy is considered and earliness tardiness is minimized, subject to a constraint on the CO₂ emissions. Non-dominated solutions for the bi-objective DLSP are subsequently derived using the lexicographic weighted Tchebycheff (LWT) method. Experimental results clearly demonstrate that the LWT method is superior to the conventionally used weighted-sum method. In terms of practical applications, guidelines on how to set the number of periods, battery capacity, and carbon emissions constraints are also studied. Results of this study have significant managerial implications for actual production.     

Materials for global carbon dioxide recycling

CO₂ emissions, which induce global warming, increase with the development of economic activity. It is impossible to decrease the CO₂ emissions by suppression of the economic activity. Global CO₂ recycling can solve this problem. The global CO₂ recycling consists of three district: The electricity is generated by solar cells on deserts. At desert coasts, the electricity is used for H₂ production by seawater electrolysis and H₂ is used for CH₄ production by the reaction with CO₂. CH₄ which is the main component of liquefied natural gas is liquefied and transported to energy consuming districts where CO₂ is recovered, liquefied and transported to the desert coasts. A CO₂ recycling plant for substantiation of our idea has been built on the roof of the Institute for Materials Research in 1996. Key materials necessary for the global CO₂ recycling are the anode and cathode for seawater electrolysis and the catalyst for CO₂ conversion. All of them have been tailored by us. They have very high activity and selectivity for necessary reactions in addition to excellent durability. A pilot plant consisting of minimum units in an industrial scale is going to be built in three years.     

Method for the application of deep reinforcement learning for optimised control of industrial energy supply systems by the example of a central cooling system

This paper presents a method for data- and model-driven control optimisation for industrial energy supply systems (IESS) by means of deep reinforcement learning (DRL). The method consists of five steps, including system boundary definition and data accumulation, system modelling and validation, implementation of DRL algorithms, performance comparison and adaptation or application of the control strategy. The method is successfully applied to a simulation of an industrial cooling system using the PPO (proximal policy optimisation) algorithm. Significant reductions in electricity cost by 3% to 17% as well as reductions in CO₂ emissions by 2% to 11% are achieved. The DRL-based control strategy is interpreted and three main reasons for the performance increase are identified. The DRL controller reduces energy cost by utilizing the storage capacity of the cooling system and moving electricity demand to times of lower prices. Additionally, the DRL-based control strategy for cooling towers as well as compression chillers reduces electricity cost and wear-related cost alike.     

An Overview of Opportunities for Waste Heat Recovery and Thermal Integration in the Primary Aluminum Industry

Efficient smelters currently consume roughly 13?MWh of electricity per ton of aluminum, while roughly half of that energy is lost as thermal waste. Although waste heat is abundant, current thermal integration in primary aluminum facilities remains limited. This is due to both the low quality of waste heat available and the shortage of potential uses within reasonable distance of identified waste heat sources. In this article, we present a mapping of both heat dissipation processes and heat demands around a sample facility (Alcoa Deschambault Quebec smelter). Our primary aim is to report opportunities for heat recovery and integration in the primary aluminum industry. We consider potential heat-to-sink pairings individually and assess their thermodynamic potential for producing energy savings.     

Updating a 1950s-generation aluminum smelter

Hindalco’s aluminum electrolysis cells were initially installed in 1962, and the technology was based on 1950s-generation pots. Although Hindalco expanded its aluminums melting capacity from 20,000 tonnes per year to 175,000 tonnes per year, the basic design of the pots remained unchanged. In view of energy price increases, and to keep pace with the latest developments in aluminum smelting technology, Hindalco undertook efforts to modernize its facilities. In spite of numerous constraints, the Hindalco smelter has been able to achieve performance nearly equivalent to that of 1980s-generation pots by retrofitting new technologies. This has resulted in considerable savings in electrical energy consumption and raw materials usage.     

我国铝工业发展之管见

根据铝工业的生产特点，以合理利用能源为中心，阐述了铝工业企业优化组合的意义。优化组合后，初步估计吨铝产品可节省480元的生产费用；以年产342．7万t原铝计，每年可节省生产费用的16．45亿元人民币，从而提高了社会效益和企业的经济效益。根据我国的铝资源情况，提出了解决电工用铝的途径。     

Potential Applications of Concentrated Solar Thermal Technologies in the Australian Minerals Processing and Extractive Metallurgical Industry

The Australian minerals processing and extractive metallurgy industries are responsible for about 20% of Australia’s total greenhouse gas (GHG) emissions. This article reviews the potential applications of concentrated solar thermal (CST) energy in the Australian minerals processing industry to reduce this impact. Integrating CST energy into these industries would reduce their reliance upon conventional fossil fuels and reduce GHG emissions. As CST technologies become more widely deployed and cheaper, and as fuel prices rise, CST energy will progressively become more competitive with conventional energy sources. Some of the applications identified in this article are expected to become commercially competitive provided the costs for pollution abatement and GHG mitigation are internalized. The areas of potential for CST integration identified in this study can be classed as either medium/low-temperature or high-temperature applications. The most promising medium/low-grade applications are electricity generation and low grade heating of liquids. Electricity generation with CST energy—also known as concentrated solar power—has the greatest potential to reduce GHG emissions out of all the potential applications identified because of the 24/7 dispatchability when integrated with thermal storage. High-temperature applications identified include the thermal decomposition of alumina and the calcination of limestone to lime in solar kilns, as well as the production of syngas from natural gas and carbonaceous materials for various metallurgical processes including nickel and direct reduced iron production. Hybridization and integration with thermal storage could enable CST to sustain these energy-intensive metallurgical processes continuously. High-temperature applications are the focus of this paper.     

Iron Ore Developments Surge in West Africa

The first ton of iron ore from West Africa was shipped in 1951. Since then, exports have exceeded 4 million tons per year. This article reviews the present status of iron ore mining in West Africa, which is predicted to attain a capacity of 40 to 50 million tons by 1970.     

多孔CoCrNi中熵合金的制备和吸能特性分析

本文采用粉末烧结-溶解法成功制备了孔隙率为63%~78%,孔径1.3~2.2mm的多孔CoCrNi中熵合金,借助SEM和XRD对试样的孔形貌和物相组成进行分析,并对试样进行轴向准静态压缩实验研究。结果表明：多孔CoCrNi中熵合金的弹性模量和屈服平台应力均随孔隙率、孔径的增大而减小;相对孔隙率而言,孔径对力学性能的影响程度较低;不同孔隙率的多孔CoCrNi中熵合金其致密应变下单位体积的能量吸收值为34.8~14.3MJ/m₃^,约为泡沫铝的3.8倍,且5种孔隙率的理想吸能效率(I)都接近0.8,说明该多孔CoCrNi中熵合金有潜力成为一种理想的吸能材料。