Effect of Oxygen Enrichment on Flow Field, Temperature, and Gas Concentration Profile Inside a Pilot-Scale Rotary Hearth Furnace

Effect of oxygen enrichment on flow field, temperature, concentration distribution, emission, and fuel economy has been studied inside a pilot-scale Rotary Hearth Furnace (RHF) for two separate conditions with or without varying the fuel amount. In varying fuel condition (when amount of fuel is reduced with oxygen enrichment to maintain the flame temperature constant), the fuel consumption was reduced by 14.9 pct, when oxygen enrichment in increased from 21 to 35 pct. Under this condition, the high-temperature zone showed a shift, more towards the upstream of the flame with an increase in the oxygen enrichment and led to a decrease in heat transfer towards the bottom part of the furnace, not desirable for pellet reduction at the bottom. In case of constant fuel (fuel volume remaining constant irrespective of oxygen enrichment), the high-temperature zone spreads away from the burner and such shift progressively becomes more with an increase in the oxygen enrichment. More importantly, in this case, efficiency heat transfer from the top to the bottom of the furnace increased with oxygen enrichment. Specific CO₂emission per ton of DRI produced showed a sharp decrease with an increase in oxygen enrichment, mainly in fuel varying condition. In contrast, the emission remained more or less similar in fuel constant condition.