Current status and prospects of low-energy denitrification process technology for sintering flue gas

Low-energy NO_x abatement in the sintering process of the iron and steel industry is a key step toward achieving the synergy between pollution reduction and carbon reduction. In the conventional selective catalytic reduction denitrification process, the flue gas, which drops to 100-150 ℃ after desulfurization, must be reheated to 280-320 ℃ to meet the catalyst activity requirements. This reheating process consumes a large amount of blast furnace gas and results in significant carbon emissions. To address this challenge, significant progress has been made in recent years in low-energy denitrification technologies, following two main pathways, "lowering the selective catalytic reduction（SCR） reaction temperature" and "replacing external heating with internal heat sources from the flue gas itself". Based on a review of domestic and international literature and analyses of industrial engineering cases, four technical routes, i.e., low-temperature SCR catalyst development, activated carbon high-efficiency purification coupled with low-temperature SCR, precious metal CO catalytic-SCR coupling, and transition metal CO catalytic-SCR coupling, are systematically reviewed in terms of their principles, application status, and economic performance. The results indicate that low-temperature SCR catalysts can achieve high denitrification efficiency at 150-200 ℃, and when combined with upstream activated carbon desulfurization and dust removal, the reheating energy consumption can be substantially reduced or even eliminated. The CO catalytic-SCR coupling technology utilizes the strong exothermic effect of catalytic oxidation of CO, which exists at high mass concentrations （6 000-10 000 mg/m³） in sintering flue gas, to provide heat compensation for denitrification, achieving CO removal efficiencies exceeding 70% and gas savings of 63%-100%. However, the long-term stability of low-temperature SCR catalysts under SO₂ and H₂O containing complex flue gas conditions remains a core bottleneck, and the poison resistance of non-precious metal CO catalysts has not yet reached the requirements for industrial application. Future development should focus on improving the sulfur and water resistance and service life of low-temperature SCR catalysts, advancing CO catalytic-SCR coupling from single-function catalysts toward bifunctional integrated catalysts that enable synergistic CO oxidation and SCR denitrification within a single catalyst bed, and gradually replacing precious metals with non-precious metal catalysts to further reduce costs and promote the large-scale application of low-energy denitrification technologies in the steel industry.