CALCULATED ALUMINUM OXIDATION RATES DURING ROTARY FURNACE MELTING THROUGH FLUE GAS ANALYSIS - PART TWO

Continuous flue gas composition measurements (CO, CO2, O2, H2) were made for four rotary aluminum melt furnace heats, with air/oxy/gas combustion. In many cases, during rotary furnace aluminum melting, the furnace atmosphere becomes increasingly reducing (higher CO and H2, lower O2 and CO2) as the heat progresses. This suggests that aluminum is being oxidized. For these four heats, melting, aluminum chips, the measured flue gas CO, CO2, O2 and H2 compositions were utilized, along with C, H and O balance equations, to calculate instantaneous aluminum oxidation rates throughout the heat. Calculated total aluminum oxidation loss ranged from 0.5% to 1.4%. Instantaneous oxidation rates are significantly higher at the end of each heat, corresponding to highest temperature just before tapping. Oxidation rate correlates most strongly with measured flue gas temperature, and does not seem to correlate with % O2 participation or % excess oxidizer from the burner settings.