Techno-economic assessment of integrated steam cleaning and recovery from alumina calcination

This study evaluates the techno-economic viability of integrated steam recovery from various alumina calcination pathways. A novel recovery flowsheet is developed to enable fine particle removal prior to mechanical vapour recompression (MVR) system, allowing efficient recovery of both diluted and high-concentration steam. Four scenarios were evaluated: recovery of diluted steam from either natural gas/air or H 2 /air combustion (Scenarios 1 and 2), and recovery of high-concentration steam from either fully electrified calcination (Scenario 3) or H 2 in oxygen-steam (oxy-steam) combustion (Scenario 4). All the scenarios were modelled in Aspen Plus to assess technical performance, and economic feasibility. Scenario 4 achieves the highest recovery rate at 0.86 t steam /t Al2O3 , followed by 0.64 t steam /t Al2O3 for Scenario 3 and 0.54–0.55 t steam /t Al2O3 for Scenarios 1 and 2. High-concentration steam recovery is more energy efficient, requiring 0.54 GJ/t steam of electricity (9% for particle removal, 91% for compression) compared with 0.71 GJ/t steam (5% for gas separation, 95% for compression) for diluted steam from air-based calcination. Integrating steam recovery from calcination with existing natural gas boilers (the “A” Scenarios) reduces steam-generation energy use by 21–36% and CO 2 emissions by 27–43% relative to a baseline of 6.63 GJ/t Al2O3 . Replacing natural gas boilers with electric boilers (the “B” Scenarios) enables zero direct on-site emissions from steam supply and delivers an additional 15% reduction in energy consumption. Economically, Scenario 4A achieves the greatest benefit, lowering the levelised cost of decarbonised steam (LCOS B ) by 26% compared with natural gas boilers with carbon capture and storage cost. Overall, the results demonstrate that integrating steam recovery enables substantial improvements in energy efficiency and CO₂ reduction, with high-concentration steam recovery provides superior thermodynamic and economic performance over conventional air-based systems.