A systemic study for enhanced waste heat recovery and renewable energy integration towards decarbonizing the aluminium industry

The aluminium remelting industry relies on natural gas to transform recycled aluminium into aluminium feedstock, entailing significant atmospheric emissions. Hydric resources are also affected as they are used as sinks of waste heat from the casting process. Enhanced waste heat recovery and renewable energy integration may play an important role in decarbonizing the energy requirements of the aluminium production and increase the revenues of the industrial site. Using biomass to replace fossil fuel via thermal gasification may also help to decentralize energy supply and diversify the energy inputs to heavy industries traditionally dependent on natural gas. Carbon abatement units along with power-to-gas systems may also aid offsetting the seasonal availability and prices of electricity and fuel. Yet, due to the nature of the heat exchanging interfaces in aluminium plants, the energy integration is more challenging compared to conventional chemical plants. Thus, a systematic study is used to determine the most suitable options to deliver the energy requirements to an aluminium plant, without significantly impacting its operational feasibility, especially in scenarios of seasonal prices. In this way, the arrangement with minimum investment cost that meets the energy demands of the industrial aluminium remelting can be determined. As a result, hard to decarbonize heavy industries require breakthrough approaches for a proper management of waste heat recovery, cogeneration and carbon abatement technologies. Higher costs of natural gas will favor electrification of heating supply in a more efficient and environmentally friendly way. The carbon tax is an important factor that may boost the deployment of carbon abatement technologies and more efficient energy conversion systems, although may not be enough for reducing the risk perception. Electricity imported is used in the plant to drive the auxiliary aluminium remelting processes. A fraction of electricity can be stored in a seasonal way (short and long term) so that it can be used in a power-to-gas-to-heat approach. This process is more expensive capex-wise. Installing a novel CO2-based district heating network may increase efficiency, as the amount of power consumed is much lower than the heat supply using fired heaters (harvest energy from environment).