Review of measures for improved energy efficiency in production-related processes in the aluminium industry – From electrolysis to recycling

Abstract

The aluminium industry is facing a challenge in meeting the goal of halved greenhouse gas emissions by 2050, while the demand for aluminium is estimated to increase 2-3 times by the same year. Energy efficiency will play an important part in achieving the goal. The paper's aim was to investigate possible production-related energy efficiency measures in the aluminium industry. Mining of bauxite and production of alumina from bauxite are not included in the study. In total, 52 measures were identified through a literature review. Electrolysis in primary aluminium production, recycling and general measures constituted the majority of the 52 measures. This can be explained by the high energy intensity of electrolysis, the relatively wide applicability of the general measures and the fact that all aluminium passes through either electrolysis or recycling. Electrolysis shows a higher number of emerging/novel measures compared to the other processes, which can also be explained by its high energy intensity. Processing aluminium with extrusion, rolling, casting (shape-casting and casting of ingots, slabs and billets), heat treatment and anodising will also benefit from energy efficiency. However, these processes showed relatively fewer measures, which might be explained by the fact that to some extent, these processes are not as energy demanding compared, for example, to electrolysis. In many cases, the presented measures can be combined, which implies that the best practice should be to combine the measures. There may also be a future prospect of achieving carbon-neutral and coal-independent electrolysis. Secondary aluminium production will be increasingly important for meeting the increasing demand for aluminium with respect to environmental and economic concerns and strengthened competitiveness. Focusing on increased production capacity, recovery yields and energy efficiency in secondary production will be pivotal. Further research and development will be required for those measures designated as novel or emerging.

Barriers to and Drivers for Improved Energy Efficiency in the Swedish Aluminium Industry and Aluminium Casting Foundries

“…Aluminium can be produced either from primary or secondary sources. The production of primary aluminium starts with the mining of aluminium ore, bauxite [34]. Bauxite is refined to aluminium oxide, also called alumina, which is then electrically reduced in the electrolytic process called the Hall-Héroult process to produce pure aluminium [34].…”

“…The production of primary aluminium starts with the mining of aluminium ore, bauxite [34]. Bauxite is refined to aluminium oxide, also called alumina, which is then electrically reduced in the electrolytic process called the Hall-Héroult process to produce pure aluminium [34]. Holding furnaces are used when adding alloying elements to the aluminium [34] to achieve the desired properties of the metal.…”

“…Holding furnaces are used when adding alloying elements to the aluminium [34] to achieve the desired properties of the metal. Secondary aluminium is produced by melting post-consumer scrap [34]. Alloying elements and/or pure aluminium are added to the metal to ensure that the proportions of different elements in the alloy are within desired limits.…”

“…Both primary and secondary aluminium are cast into ingots, slabs, or billets [34] depending on the application. Profile extrusion uses hydraulic pressure to push a preheated billet through a steel die to produce an elongated shape with a uniform cross-section [34]. Rolling uses counter-rotating steel rolls to reduce the thickness of slabs to produce aluminium sheets with a desired thickness [34].…”

“…Profile extrusion uses hydraulic pressure to push a preheated billet through a steel die to produce an elongated shape with a uniform cross-section [34]. Rolling uses counter-rotating steel rolls to reduce the thickness of slabs to produce aluminium sheets with a desired thickness [34]. In foundries, shape casting is used to produce components of desired shapes by pouring molten aluminium into moulds, and there are different methods that can be used for this [34].…”