钢铁行业典型烧结机污染物排放特征对比研究

钢铁工业排放是引起空气污染的重要原因之一，烧结工序又是钢铁行业中的排放大户.鉴于此，选取了一台工艺相对落后但仍在我国中西部地区大量存在的90 m2小型步进式烧结机和一台工艺较为先进的450 m2大型带式烧结机，对两台烧结机不同点位的SO₂、NO_x、颗粒物以及烟气Hg等进行实测，并对颗粒物中的元素、水溶性离子、OC和EC进行分析，从而获取不同技术水平、不同污控措施下烧结机污染物排放特征以及与2019年生态环境部办公厅印发的《关于推进实施钢铁行业超低排放的意见》中的超低排放限值之间的差距.结果表明:①烧结机头SO₂、NO_x、CO、颗粒物和烟气Hg排放浓度分别为54.69~123.04 mg/m3、187.28~312.58 mg/m3、6 746.04~7 790.83 mg/m3、11.04~19.93 mg/m3和78.97~2 537.07 ng/m3，烧结机尾颗粒物排放浓度为0.76~16.22 mg/m3，机头颗粒物以PM_2.5为主，占比为81.02%~91.49%，机尾颗粒物主要为PM₁₀，占比为71.17%~73.01%.烧结机头SO₂、NO_x、颗粒物以及烧结机尾颗粒物还需分别减排36.00%~71.55%、73.30%~84.00%、9.40%~49.82%和0~38.35%才能满足超低排放限值.②烧结颗粒物主要成分为K、Ca、Na、Mg、Fe、Cl-、SO₄2-、NH₄+、OC和EC等，其占比与烧结机类型、烧结原辅料以及污染物控制措施等因素有关，石灰石-石膏法脱硫后SO₄2-占比增加28.12%，活性炭移动床脱硫后EC占比增加2.15%.③布袋除尘器对烧结机不同粒径颗粒物和烟气Hg的脱除能力比双室五电场静电除尘器分别高出1.25%~5.06%和9.51%，活性炭移动床系统对烧结不同粒径颗粒物以及烟气Hg的去除效果分别比石灰石-石膏法脱硫系统高出9.40%~11.38%和4.31%.研究显示，不同工艺、不同污控措施烧结机大气污染物排放特征存在一定差异，SO₂、NO_x排放浓度与超低排放限值差距较大，烟尘排放浓度与超低排放限值差距较小. 

Comparative Study on Pollutant Emission Characteristics of Typical Sintering Machines in Iron and Steel Industry

Emissions from the iron and steel industry are one of the important causes of air pollution, and sintering is the most important air pollutants emission source in the iron and steel industry. This study chose a 90 m² small stepping sintering machine that is relatively backward but still exists in the central and western regions of China and a 450 m² large-scale belt sintering machine with advanced technology. Measure the SO₂, NO_x particulate matter and flue gas mercury at different points of the two sintering machines, and analyze the elements, water-soluble ions, OC, and EC in the particulates, so as to obtain the air pollutants emission characteristics about sintering machine with different process and pollution control measures and the gap with ultra-low emission limits which was included in the Opinions on Promoting the Implementation of Ultra Low Emissions in the Iron and Steel Industry issued by the General Office of the Ministry of Ecology and Environment of the People''s Republic of China in 2019. The results show that:(1) The mass concentration of SO₂, NO_x, CO, particulate matter and total Hg from the sintering machine head is 54.69-123.04 mg/m³, 187.28-312.58 mg/m³, 6746.04-7790.83 mg/m³, 11.04-19.93 mg/m³, and 78.97-2537.07 ng/m³. Concentration of particle matter from the sintering machine tail is 0.76-16.22 mg/m³. Particle from head is mainly PM_2.5, accounting for 81.02%-91.49%, and from tail is mainly PM₁₀, accounting for 71.17%-73.01%. The SO₂, NO_x, particulate matter from the head and particulate matter from the tail also need to reduce emissions by 36.00%-71.55%, 73.30%-84.00%, 9.40%-49.82% and 0-38.35% respectively to meet the ultra-low emission limit. (2) The main components of sintering particles are K, Ca, Na, Mg, Fe, Cl^-, SO₄^2-, NH₄⁺, OC and EC, etc. which proportion is related to the type of sintering machine, sintering raw and supplemental materials, and pollutant control measures. The proportion of SO₄^2- increased by 28.12% after limestone-gypsum desulfurization, and the proportion of EC increased by 2.15% after activated carbon moving bed desulfurization. (3) Bag filter''s removal ability of sintering particulate matter and Hg is 1.25%-5.06% and 9.51% higher than that of the electrostatic dust precipitators, respectively. The activated carbon moving bed system''s removal ability of sintering particulate matter and Hg is 9.40%-11.38% and 4.31% higher than that of limestone-gypsum desulfurization system, respectively. Studies show that the emission characteristics of air pollutants in different sintering machines with different pollution control measures and different process are quite different, the gap between SO₂ and NO_x and the ultra-low emission limit is large, and the difference between particulate matter and the ultra-low emission limit is small.