Comparative Study On Pollutant Emission Characteristics Of Typical Sintering Machines In Iron And Steel Industry

At present,the prevention and control of air pollution in China is facing severe challenges.How to control pollution accurately is a major problem faced by environmentalists.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.However,there is still a lack of measured data on the emission characteristics of sintering machines with different production processes and different pollution control measures.It is difficult to provide source composition spectrum data for air quality modelling and particulat matter source apportionment,and it is difficult to provide scientific basis for accurate pollution control in the ecological environment department.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%-71.55%,73.3%-84%,9.4-49.82%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 9.4%-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_xand the ultra-low emission limit is large,and the difference between particulate matter and the ultra-low emission limit is small,but the limestone-gypsum system and activated carbon moving bed desulfurization system will introduce new components to varying degrees.The composition spectrum of the iron and steel sintering source should fully consider the influence of different processes and different pollution control measures in particulat matter source apportionment..