Examining low nitrogen oxides combustion in iron ore sintering: Utilization of reductants

Enhancing the reduction of carbon and nitrogen gaseous oxides in the iron ore sintering process is crucial for steel plants to meet ultra-low emission standards. The progress of technologies targeting low nitrogen oxide emissions in sintering is analyzed, focusing on gas-phase and gas-solid reactions. The primary source of nitrogen oxides in sintering is the oxidation of nitrogen-containing char. The presence of low oxygen and high temperatures near the carbon particles in the combustion zone encourages the decrease of nitrogen oxides. The capacity of ammonia, methane, hydrogen, and carbon monoxide to reduce nitrogen oxides was investigated. Injecting gaseous reductants above the sintering bed reduces solid fuel consumption and pollutants. Injecting steam also provides effective results. The cost-effective steam will pass through the combustion zone for the water-gas shift reaction, thus promoting the reduction of nitrogen by hydrogen. Nitrogen oxides heterogeneous reduction occurs primarily over char and low-valent iron oxides. Paying close attention to the removal of nitrogen oxides with the aid of iron oxides in sintering is essential. Regulating the fuel granulation could optimize the formation of calcium ferrite around combustion. Carbon oxidation and nitrogen reduction can be improved with the redox of calcium ferrite. Its final reduction product, the oxygen-deficient ferrite with highly dispersed metallic iron with calcium oxide, stabilizes in catalysis in the reducing atmosphere and can impede the suppression of oxygen. As an economically beneficial measure, fuel modification by adding oxygen-deficient ferrite was suggested to work in tandem to reduce carbon and nitrogen oxides in the process control.