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烧结烟气低能耗脱硝工艺技术现状与展望

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

  • 摘要: 钢铁行业烧结工序NOx低能耗治理是实现减污降碳协同的关键环节。传统选择性催化还原脱硝工艺需将脱硫后降低至100~150 ℃的烟气补热至280~320 ℃,以满足催化要求,该过程消耗大量高炉煤气并导致显著碳排放。针对这一难题,近年来低能耗脱硝技术围绕“降低选择性催化还原脱硝(selective catalytic reduction,SCR)反应温度”与“利用烟气内源热替代外源热”2条路径取得重要进展。基于国内外文献调研与工业工程案例分析,本文系统梳理了低温SCR催化剂开发、活性炭高效净化-低温SCR耦合、贵金属CO催化-SCR耦合以及过渡金属CO催化-SCR耦合4条技术路线的原理、应用现状与经济性。结果表明,低温SCR催化剂可在150~200 ℃实现高效脱硝,配合前置活性炭高效脱硫除尘,可大幅降低甚至消除补热能耗;CO催化-SCR耦合技术利用烧结烟气中高质量浓度CO(6 000~10 000 mg/m3) 催化氧化的强放热效应为脱硝提供热补偿,CO脱除效率大于70%,煤气节约率达63%~100%。然而,低温SCR催化剂在含水含硫复杂工况下的长期稳定性仍是核心瓶颈,非贵金属CO催化剂的抗中毒性能也尚未达到工业化要求。未来低温SCR催化剂需向更高抗硫抗水性和使用寿命方向突破;CO催化-SCR耦合将从单一功能催化剂向双功能一体化催化剂演进,在单一床层内实现CO氧化与SCR脱硝的高效协同;非贵金属催化剂有望逐步替代贵金属,进一步降低成本,推动低能耗脱硝技术在钢铁行业的规模化应用。

     

    Abstract: Low-energy NOx 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.

     

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