Energy Efficient Aluminium Cast House (CastAl)

WP1: Recover total energy Continuous work for energy optimisation of melting furnaces at Hydro Foundry alloy casthouse Sunndalsora has led to a large decrease in energy consumption. The energy usage for one casting centre was reduced from 2662 kWh/mt cold metal in April 2013 to 1400 kWh/mt cold metal, by November in 2014. The yearly saving for energy was about 4 MNOK per year. Further work at the Sunndal primary metal foundry alloy casthouse has reduced the energy to 1100 kWh/mt cold metal which is further improvement of about 1.2 MNOK peryear. Best available practice developed on how to run primary metal casthouse furnace efficiently and being communicated to different casthouses in Hydro. With electromagnetic stirring at Granges casthouse the following improvements realised Energy saving 15% = 105 kWh/MT, cost 0.5 SEK/kWh, tonnage 25 000 MT, Total 1.31 MSEK per year. Dross saving 22% = 140 MT/y, metal loss 12 SEK/kg, Total 1.68 MSEK per year. Total saving with EMS approximately 3 MSEK per year. WP2: Optimisation of operation and control Continuous measurement of off-gasses at Granges casthouse Sweden performed and the results analysed. Results indicate variations in gas composition due to burner power, furnace pressure, and contaminations on re-melted aluminium. The largest uncertainties were again from the leakages from the exhaust gas pipe. Therefore, the desired relationship between the furnace atmosphere and the melt loss per charge could not be established. The results are confusing because the measured ratio of H2O to CO2 concentration seems to be too high as compared to theoretical ratio for combustion of propane (fuel). The sensor was recalibrated by NEO in July, but showed same values afterwards. SINTEF used a separate FTIR-apparatus (Gasmet) to check the measurements (CO2, H2O, O2) in August and Ferronova checked them again early September (CO2 and O2). From experience, H2O is a difficult gas molecule to measure; it sticks to every surface, even with temperatures above dew-point. It is also likely that the point-measurements (SINTEF's FTIR and Ferronova) are not affected by gas flow in the pipe as compared to NEO which is an average measurement across the off-gas channel. Now we know the variation in atmosphere composition during complete charges for various alloys in an oxy-fuel fired furnace. WP3: Increasing metal yield Oxidation of aluminium alloys (Mn, Mg, Fe+Mg, Fe+Mn, 6082.50) in industrial furnace atmosphere preformed. Interesting findings: Oxidation of aluminium alloys (Mn, Mg, Fe+Mg, Fe+Mn, 6082.50) in industrial furnace atmosphere. The results show that Little oxidation is observed for Mg <0.01%, but significant bigger oxidation for Mg>0.6%. Fe enhances oxidation, but less than that of Mg. The relative amount of Mg oxidation shadows the effect of Fe Mn give very little oxidation, around 0.03% in 14h. CO2 does not behave as inert gas. CO2 and O2 both encourage oxidation, and sometimes CO2>O2 Ar and N2 behave as inert gases for lower Mg alloy, but not for 1.3Mg ( N2>Ar) Oxide skin strength measurements of aluminium alloys (Mn, Mg, Fe+Mg, Fe+Mn, 6082.50) in industrial furnace atmosphere performed. The experiments with adjusted atmosphere indicate that both CO2 and water vapour affect the oxide skin strength compared to dry air. For most alloys, the temperature and atmosphere seems to have larger impact on the increase in oxide skin strength than the alloy composition. More measurements are needed for verification of conclusions. Closed chamber for apparatus build and tested. Tests performed in adjusted gas composition and humidity. Main findings are: 1 ? 5% Mn does not contribute to oxide skin strength Fe + Mn may lower oxide skin strengh CO2 seems to lower oxide skin strength Fe + Mg seems to lower oxide skin strenth H2O seems to increase oxide skin strength WP4: Utilisation of generated knowledge The best available practice for metal content in dross established and communicated to the industrial partners. The results obtained so far were presented and discussed in a project meeting on the 03.12.2014.

CastAl aims to demonstrate selected techniques to determine energy losses, preheating of metal, increased recycling amount, new monitoring and control of melting furnace and lower dross formation, resulting in yield increase and reduced energy consumption to approximately 500 kWh/t by 2014. Hydro and SAPA will collaborate with Sintef and NTNU to: -Determine heat losses over complete process line -Define optimized parameters and conditions for preheating and melting of pure and scrap Al in optimal atmos phere in casthouses, enabling lower energy consumption and lower metal loss -Optimise operation and control through measuring and monitoring equipment in cast houses -Investigate several parameters for process optimisation to increase metal yield -Opti mize and implement best practice on furnaces for pre-heating of scrap, leading to reduced energy consumption -Transfer knowledge relating to energy efficiency and yield as efficiently as possible into existing processes within Hydro/SAPA.