| The iron and steel industry is one of the major sources of waste gas pollution among each industrial department in China.The emission amount of waste gas from iron and steel enterprises every year adds up to 1,200 billion cubic meters,among which particulate is the major pollutant that exerts crucial influence on both environment and human health.Hence,the research of emission characteristics of particulates from iron and steel enterprises is of positive significance to understand the emission rules of pollutants from iron and steel enterprises,effectively control and manage pollutant emission,and technically and administratively promote the improvement on pollutant emission status of iron and steel enterprises.In the light of the typicality of iron and steel industry in national industries,the present paper selected the processes of sintering and iron-making in iron and steel industry as the object,fabricated detailed research plan after comprehensively analyzing the prior research status and outcomes, measured in certain enterprises having certain scale and typical processing apparatus and waste gas treatment apparatus,and researched the emission characteristics of particulates based on the measured data.The present research employed a fixed-source inhalable particulate sampling system mainly on ELPI with trapping particle size 0.03μm at minimum and 10μm at maximum.Verified by the measurement,the sampling system could better cover the particle size range of particulates from the typical process of iron and steel industry,and be effectively applied to the sampling and measurement of particulates from the iron and steel industry.Under normal conditions,the measured emission concentrations of dust from three emission points of machine head and machine tail of sintering plant and tapping field of iron-making plant were 4.8 mg/m3,9.93 mg/m3,and 9.5mg/m3,far lower than the emission limits of National Standard, indicating a good emission result. According to the measured emission concentrations,the paper calculated the dust production amounts of unit product at the three characteristic emission points:1.031 kg/t sinter,6.490 kg/t sinter, and 4.415 kg/t iron,and emission amounts:0.026 kg/t sinter,0.019 kg/t sinter,and 0.032 kg/t iron, and further researched the particulate production amounts and emission amounts of unit product in terms of particle size,wherein the amounts of PM10 produced were 0.528 kg/t for sinter,0.507 kg/t sinter,and 0.209 kg/t iron,and the emission amounts of PM10 were 0.025 kg/t sinter,0.008 kg/t sinter,and 0.016 kg/t iron,and the production amounts of PM2.5 were 0.451 kg/t sinter,0.402 kg/t sinter,and 0.180 kg/t iron,and the emission amounts of PM2.5 were 0.022 kg/t sinter,0.007 kg/t sinter,and 0.014 kg/t iron.It was therefore concluded that the percentages of PM10 in production amount of dust at the three characteristic points were 51.23%,7.81%,and 4.74%,and those of PM10 in emission amount were 99.38%,43.20%,and 50.84%,and that the rates of PM2.5 in production amount of dust at the three characteristic points were 43.73%,6.20%,and 4.09%,and those of PM2.5 in emission amount were 85.00%,36.46%,and 45.68%.These data reflected the rate of each particle size in particulates from the characteristic process of iron and steel enterprises,and could be used as the basic reference data for calculating pollutant emission factors of the iron and steel industry.Based on the research of fractional collection efficiency at each point,the collection efficiencies of PM2.5,PM10,and dust in particulates from machine head of sintering plant were 96.55%,96.56%, and 98.22%,those from machine tail were 98.30%,98.41%,and 99.71%,and those from tapping field of iron-making plant were 93.20%,93.38%,and 99.39%.All of the points disclosed the rule of collection efficiency:PM2.5＜PM10＜dust.The paper also concluded the effect and contribution of different fractional collection efficiencies via fractional research.The particle size distribution of particulates from iron and steel enterprises had its own significant characteristic that the mass percentages of PM2.5 in PM10 after the dust collectors of machine head and machine tail of sintering plant were 85.61%and 84.38%,and that after the dust collector of tapping field of iron-making plant was 89.70%,i.e.,the major particulate from typical process of iron and steel enterprises was PM2.5.Judged from the chemical component analysis of the particulates from the three characteristic points,the major components of each characteristic point were substantially the same,all comprising Fe,Si,Ca,K,Al,Na,SO42-,Cl-,and high-ratio organic carbon,but the contents of each component at each point varied in ordering,which was dependent on the process and related parameters corresponding to each emission point.Via the above research from macroscopically to microscopically,the present paper induced and concluded the basic characteristics of particulate emission of iron and steel enterprises from the three aspects covering the emission concentration of particulates and the collection efficiency characteristics of typical dust collectors,the particle size distribution characteristics of particulates, and the distribution characteristics of each component of particulates,thereby laying the necessary theoretical foundation for further researching the emission factors of iron and steel enterprises and establishing pollutant lists of iron and steel enterprises. |
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