Experimental Study On Combustion Characteristics Of High-concentration Chemical Waste Liquid And Flame Characteristics Of Single Droplet Based On OH-PLIF Technology

Due to the continuous expansion of the petrochemical industry in recent years,the disposal of chemical waste liquid has become a key area of National Pollution Control,and many chemical industries are increasingly under pressure to reduce emissions.In the process of producing methionine,a large amount of acrylic acid waste liquid is produced.The industrial method for processing high-concentration acrylic acid waste liquid is mainly incineration.In a burner that burns waste liquid,the atomization,evaporation,and combustion of droplets are critical.Studying the sub-process of single waste liquid droplet combustion becomes the basic research of waste liquid spray combustion.Previous studies have not carried out in-depth research on the pyrolysis and combustion processes of typical chemical waste liquids.In this paper,the typical chemical waste liquids produced by methionine production enterprises are used as research objects.The elemental composition of waste liquid and ash are measured by XPS and XRF.Under the inert atmosphere(nitrogen)and oxidizing atmosphere(dry air),the thermogravimetric test study is carried out to analyze the pyrolysis and combustion characteristics of the chemical waste liquid with temperature,which provided a basis for the calculation of the heat transfer in the furnace when the burner was designed.Because there is no systematic research on the combustion of typical waste liquid droplets in the current literature,a droplet combustion test system based on OH-PLIF technology and can control the atmosphere of high temperature heat source is designed,which can capture the concentration and distribution of OH group in the combustion process.Through the single-drop OH-PLIF experiment,we focus on the effects of waste liquid properties and high-temperature environmental atmosphere on the single-drop combustion process.The research results show that the representative component of the waste liquid is sodium acrylate,and the contents of N and S elements are low;the ignition temperature of this high-concentration chemical waste liquid solids is 370 ℃,the ignition temperature is relatively low,and the ignition performance is good;The solid content of waste liquid pyrolysis and combustion reaction rate is maximum at 450℃;the ash melting temperature of waste liquid is low,and the slag droplets on the furnace wall are easy to slag during burning.The fluorescence intensity increases rapidly from the ignition point to the maximum light during the droplet combustion.The intensity value fluctuates with a larger light intensity value,and then gradually fades to a smaller range;the larger the droplet volume is,the larger the surface area of the droplet becomes,the lower the evaporation rate,the longer the ignition delay period,the more the organic matter in the same longitudinal direction,the reaction zone is concentrated in a smaller range,and the chemical reaction intensity in this range is more vigorous;the greater the droplet concentration,the smaller the difference of water vapor between the droplet surface and the hot atmosphere gas flow,the smaller the droplet evaporation rate.The higher the chemical activity of the upstream reaction zone,the lower the probability of the reactants diffusing downstream,the lower the flame height,and the brighter the flame;the hot atmosphere flow rate around the droplet will accelerate the droplet heat transfer,accelerate the droplet ignition and affect the flame shape,showing a "slim and tall" appearance;with the increase environment of flow rate of the thermal atmosphere,the stagnation period shortens first and then tends to be smooth,the heat exchange with the thermal is more intense,and the droplet evaporation and combustion rate are accelerated,but excessive flow rate may disturb the original proper state;the increase in the temperature of the hot atmosphere will accelerate Brownian motion,the internal temperature gradient is more uniform,and the organic matter in the droplets also accelerates the cracking and evaporation,thereby shortening the stagnation period and burning of the droplets.At the end of the period,the flame brightness increases;increasing the O2 concentration in the accompanying gas has little effect on the stagnation period,while the burnout period becomes shorter,the area and height of the flame surface decrease,and the average flame brightness increases.