Study On The Emission Characteristics & The Law Of Diffusion And Migration Of Smoke And Dust In Iron And Steel Plant

In recent years,haze events have occurred frequently,and air pollution has become a prominent problem that puzzles China's society.Reducing particulate matter emissions is one of the main ways to effectively alleviate haze weather and improve urban air quality.Smoke and dust emitted from iron and steel plants as one of the sources of atmospheric particulates have become the focus of air pollution prevention and control work in China.However,at present,the understanding of the emission characteristics and the diffusion rule in the atmosphere of smoke and dust in steel plants are far less than the requirements of environmental sustainable development.In spite of the thorough research on the individual emission sources at home and abroad,the characteristics of the smoke dust from the iron and steel plant to the atmospheric environment and the pollution of the environment can not be fully understood.In view of this,this paper uses field sampling detection,laboratory analysis and simulation research to study the characteristics of smoke and dust emission in iron and steel plant and the law of diffusion and migration in atmospheric environment.It is of great theoretical and practical significance.The main research work and conclusions are as follows:(1)Using field testing and laboratory analysis methods,the sampling and analysis of smoke and dust in iron and steel plant were carried out systematically,and the mass concentration,particle size distribution and fingerprint characteristics of smoke and dust(morphology and chemical composition)were studied..Interviews and questionnaires were conducted to investigate nearly 100 steel plants and select the typical large iron and steel plant as research object,the total suspended particulate matter(TSP)and inhalable particulate matter(PM10)samples of 14 organized and 5 unorganized key emission sources in the steel production process under normal operating conditions were collected using the smoke dust tester and the PM10 classification sampler.The concentrations of smoke and dust emitted from various sources were obtained.The particle size distribution characteristics of smoke and dust from various sources were identified by laser particle size distribution instrument.The characteristics of smoke dust micromorphology of each emission source were studied by means of Scanning electron microscope with energy dispersive spectrometer(SEM-EDS),X ray fluorescence spectrometry(XRF)and inductively coupled plasma optical emission spectrometer(ICP-OES),and the composition of 29 elements of smoke dust in each emission source was quantitatively analyzed.The size range is 0.1?320 ?m,in which the dispersion of smoke dust at each point of the sintering process is high,and the size of the particle size is less than 10 ?m,accounting for 30%?40%.The particle size of the blast furnace tapping field and each discharge point of steelmaking process is mainly below 40 ?m,and the proportion of the particle size less than 10?m is 85%?95%.The morphology of smoke dust mainly consists of spherical particles,ultrafine particle aggregates and irregular lump or powder particles.(2)The emission factors and emissions of smoke and dust in iron and steel plant were calculated,the characteristics of smoke and dust emission were analyzed,and the latest emission level of smoke and dust in China's iron and steel plants was obtained.The emission factor of smoke and dust in iron and steel works is the most basic parameter reflecting the emission status of smoke and dust,and plays a vital role in the calculation of smoke and dust emissions.The smoke dust emission factors of the typical steel plant in China are calculated according to the characteristics of the smoke and dust emission and the results of the sampling analysis,and the contribution rate of key sources to the smoke dust emission factors of iron and steel plants is analyzed.Based on the calculation results of emission factors,the emissions of smoke and dust from iron and steel plants were further calculated,and the composition of smoke and dust emissions was analyzed.The emission factors of sintering process are the largest in each process,and the emission factors of TSP,PM10 and PM2.5 are 0.21kg/t sinter,0.12kg/t sinter and 0.06kg/t sinter.The emission of TSP,PM10 and PM2.5 of tonne steel is 0.59kg/t steel,0.37kg/t steel and 0.21kg/t steel respectively,and the total annual quality of the iron and steel works is 4217 t and PM10 accounts for 65.31%of the total annual emissions.The contribution rates of sintering process to annual emissions of TSP,PM10 and PM2.5 were 50.82%,48.22%and 45.63%respectively.(3)Combined with the current situation and development trend of China's iron and steel plants,the evaluation index system of smoke and dust emission is constructed,and the influencing factors of the evaluation index are deeply analyzed.The index system includes two types of indicators,namely,organized emissions and unorganized emissions.The organized emission targets are divided into four levels,namely,enterprises,processes,equipment and emission points.The mathematical relation of smoke and dust emission from organized and unorganized emission sources was established,and the main influencing factors such as resource energy consumption,particle size distribution and dust removal efficiency,product production and industrial structure,production equipment scale,and statistical week period of smoke dust were studied.Resources and energy consumption(including mineral resources,energy and air resources)have a decisive impact on the emission of smoke and dust.To reduce smoke and dust emissions,we must reduce the consumption of natural resources such as minerals,energy and air at the source.The higher the PM10 content in TSP is,the lower the dust removal efficiency is(?PM2.5<?PM10<?TSP),and the higher the quality of smoke and dust emission.It is suggested that environmental indicators(smoke and dust emission quality)be one of the main criteria for eliminating backward production capacity.(4)The diffusion and migration of smoke and dust in the surrounding environment of iron and steel plant was studied in depth by means of simulation.Based on the AERMOD diffusion model,the smoke and dust diffusion laws of organized emission sources in normal operating conditions,variation of source strength and unorganized emission sources in the absence of dust suppression measures and dust suppression measures were studied respectively.The effects of smoke dust on the surrounding environment in different statistical periods were evaluated.The mass concentration distribution and settlement of TSP and PM10 were predicted.The prediction results show that the strong sources of smoke and dust emissions and regional meteorological conditions are two key factors affecting their diffusion and migration.The mass concentration distribution is directly proportional to the emission quality of smoke and dust.The worst weather conditions are static wind and small wind conditions(wind speed less than 1.5 m/s)and F level atmospheric stability.The area with the largest influence of smoke dust diffusion on atmospheric environment is the 1 km range dominated by the emission source,and the maximum ground mass concentration and settlement are within this range.The annual average quality of the iron and steel plant is up to the standard,but the daily mean is over 5 times,and the suggestion that the emission limits of smoke and dust should be taken into account in the formulation of smoke and dust emission indicators.The annual total settlement of smoke and dust in iron and steel works is 164.34 t/(km2·a),and the average monthly settlement is 13.70 t/(km2·30d).