(41d) Sustainable Aluminium Production Process: Solid Wastes Mineralization and use of Hydrogen Enhanced Natural Gas as an Alternative Fuel

Carbon dioxide emissions from process industries such as aluminium pose a long-term challenge to sustainable industrial growth. A variety of solutions have been published on the menace of CO₂ emission most of which are either pre-treatment of fuels or post treatment of waste generated by the fuel. However, little has been done on the aspect of combining these two methods. Thus, the use of hydrogen enhanced natural gas (HENG) as an alternative fuel and the capturing of carbon dioxide by mineralization of wastes generated during aluminium production were evaluated. While the use of pure hydrogen can lead to zero emission, the challenge of implementing this idea is the need to build completely new facilities for hydrogen combustion and safe handling. The use of HENG will require very little or no modification to the existing facilities in the industry. In this study, aluminium production process was simulated using Aspen Plus by considering HENG as alternative energy source and placing a carbon capture and mineralization unit downstream of the production process. The feasibility of the carbon capture and mineralization unit was experimentally investigated using aluminium wastes slag that was collected from local aluminium industry. These samples were carbonated with a high pressure and high temperature reactor using mixture of CO₂ and N₂. The mineralization was carried out at various operating conditions of gas pressure from (1 to 5bar), temperature (25 to 90^oC), and reaction time (1 to 6 hours). Carbon mineralization was evaluated using dielectric permittivity, the TGA, XRF, and SEM-EDS. The results of the simulation showed that the use of HENG with 17mole% H₂ can lead to 19.65% increase in energy generation, and 21.69% decrease in CO₂ emission. Moreover, the results of SEM, corroborated by the XRF results, revealed the formation of flaky and clustered crystals of carbonates minerals. The results of TGA showed a distinctive carbonation profile which seems to be more pronounced at 5bar. Overall, synergistic use HENG and CO₂ mineralization using solid wastes from aluminium industries are potential candidates for achieving net zero production process.

Keywords: sustainable growth, process intensification, carbon mineralization, hydrogen enhanced natural gas, net zero emission.