| China is a country with a large consumption of coal resources.A great deal of dust will be generated in the process of coal mining,storage,transportation and combustion,causing serious pollution to the environment.Respirable dust,especially PM2.5,is easily combined with harmful substances in the air such as heavy metals and organic hydrocarbon compounds.After entering the human body through the respiratory system,it deposits in the respiratory tract and alveoli,causing serious harm to the human body and attracting widespread attention from the society.Because of its economical practicability,chemical dust suppressant has broad development prospects.And chemical agglomeration technology can effectively enhance the removal performance of electrostatic precipitators for fine particles,and has the advantages of low cost,high efficiency and simple operation.Therefore,it has good industrial application value.Four kinds of polymer monomers with different chemical properties are selected for the fine particles produced by the unorganized emission of lignite open pit mine.Through the attenuation of crust hardness and anti-rain erosion experiment,guar gum was ascertained to be a monomer with excellent properties.Through the surface tension and contact angle experiments,Tween-20,Triton X-100,sodium dodecyl sulfate and sodium dodecylbenzene sulfonate were compared to determine which one has the best wetting property for lignite particles.Nonionic surfactant Triton X-100 was found to be the best.A crust type of lignite dust suppressant was developed by modifying guar gum with nonionic surfactant Triton X-100.The effects of monomer concentration and wind speed on the number concentration and size distribution of cured layer after wind erosion were investigated.The optimal dust suppressant formulation was guar gum at a mass concentration of 0.7%and Triton X-100 at 0.1%.It indicates that a protective layer with a certain thickness and strength is formed on the coal surface after the spraying of suppressant,and the hardness can reach 61.43 after 10 days.The solidified layer can resist the erosion of 15 m/s wind speed,and is enough to cope with the windy weather in the north.Furthermore,the number concentration decreases to 3.69×105cm-3,the peak of particulate number concentration appears at about 0.85?m.The removal efficiency of particulate matter in low size segment increases from 30.1%to 94.4%,and the inhibition efficiency of fine particles with a diameter of about 0.1?m increases by 64%.The results show that the suppressant has an obvious effect on restraining fine particle.And it is an easily available,environmental-friendly and high-efficiency dust suppressant for lignite mines.Four polymer reagents were selected as chemical agglomerating agents to investigate their wettability to fly ash and agglomeration performance.Furthermore,the influences of solution properties and nozzle pressure on the atomization characteristics of agglomerated solution were both studied.The results show that the polymer polymer was connected with the fly ash by hydrogen bonding,capillary force or viscous force to form a liquid-bridge force,which improved the particle size of the particles in the agglomerating solution.The larger the relative molecular weight of the polymer reagent,the better the agglomeration effect on the fly ash particles.The viscosity of the solution had a significant effect on its atomization properties.The solution with high viscosity could improve the atomization effect by increasing the gas phase pressure.However,as the viscosity increases,its reinforcing effect on breaking droplets was weakened.Among four solutions,polyacrylamide?PAM?had the worst atomization effect,while polymer emulsion polyacrylic acid?PAE?and styrene-butadiene emulsion?SBE?could maintain good atomization effect in a large concentration range.To explore the influence of agglomeration solution and its atomization performance on removing fly ash,sesbania gum?SBG?and styrene-butadiene emulsion?SBE?were selected to conduct the experiment via the coal-fired platform.The reduction efficiency of SBG solution for fine particles reached a maximum of 28.65%when the mass concentration was 0.3%,and decreased when the concentration exceeded 0.3%.At a concentration of 1%,the reduction efficiency was only 25.05%.For SBE solution,the reduction efficiency of the fine particles increases with the increase of mass concentration.However,as the concentration increased,the increase of the efficiency decreased.It indicates that the increase in the concentration is not conducive to the chemical agglomeration process,and the viscosity of solution has a direct influence on the chemical agglomeration performance.Since the viscosity of SBG solution was larger than that of SBE solution,its atomization performance was poorer,which was not conducive to the trapping of the fly ash by the agglomerated droplets.By testing the concentration of fine particles at the outlet of ESP,it was found that chemical agglomeration could increase the particle size at the inlet of ESP.In addition,it could effectively enhance the trapping and removal performance of ESP on fly ash,and reduced the concentration of fine particles at the outlet of ESP.SBE+TX-100 exhibits excellent chemical agglomeration performance. |
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