Study On SO₂ And NO_x Control Technology In Lead Paste Smelting Furnace

Lead paste has been used to recover secondary metal resources due to its large quantity,high yield and many valuable metals.In industry,lead paste is mostly treated by fire method,but it will produce flue gas containing SO₂,NO_Xand other pollutants,which makes this technology face new challenges.In order to reduce the emission of pollutants,the recycled lead smelting industry often uses the high content of SO₂in the flue gas to prepare concentrated sulfuric acid to realize the reuse of flue gas.Washing and purification process is the key link of flue gas acid production process,mainly to remove smoke and dust and other impurities in the flue gas,at this time the acid fog in the flue gas is also washed into the wastewater,making the washing wastewater acidic,increasing the difficulty of treatment of the wastewater.The transformation of SO₂to SO₃will not only reduce the content of SO₂in the smelting flue gas,but also increase the formation of acid fog,which will affect the nature of the waste water in the flue gas purification process.Therefore,improving the concentration of SO₂in the flue gas,reducing the transformation of SO₂and inhibiting the production of NO_Xwill be more beneficial to the flue gas pollution control in the industry.In this paper,the control technology of SO₂and NO_Xproduced in the smelting process of lead paste is studied.The main research contents and conclusions are as follows:（1）The results of thermal stability and thermal decomposition kinetics of lead paste show that there are two weight loss stages in thermal decomposition of lead paste at 25℃～1200℃.The first weight loss stage occurs at 300℃～600℃,and the weight loss rate is 3.3%.The second stage of weightlessness occurs after 900℃,with a weight loss rate of 50.2%.The average activation energy of the lead paste in the first stage of thermal weightlessness is 158.32 k J/mol.The second stage of weightlessness is the main stage of the decomposition of lead sulfate and the release of SO₂.The average activation energy of the reaction in this stage is 158.32 k J/mol,and the solid phase decomposition mechanism conforms to the three-dimensional diffusion reaction model.（2）the lead paste pyrolysis characteristics of SO₂produces in the process of the research results show that the oxygen concentration,temperature,reaction time and four influencing factors of gas velocity,the oxygen concentration and temperature on SO₂generation and has the greatest effect in the transformation process,the temperature is 1300℃and oxygen concentration of 30%～40%,and is conducive to ascend in furnace SO₂concentration and reduce the production of SO₃.（3）The simulation study on the NO_Xgeneration behavior in the lead paste smelting furnace shows that oxygen concentration,temperature and oxygen injection speed all affect the NO_Xgeneration in the lead paste smelting furnace.When the temperature is1300℃,the oxygen concentration is 30%～50%,and the oxygen injection rate is greater than 220 m/s,the NO_Xgeneration in the furnace can be inhibited.The smelting conditions of increasing the concentration of SO₂and reducing the production of SO₃and NO_Xin the lead paste smelting furnace were proposed,and the optimization suggestions for the smelting process parameters of lead paste were put forward.The experimental results in lead paste smelting process show that under the conditions of temperature 1300℃,oxygen concentration 30%,and oxygen injection speed 240 m/s,the amount of acid pollution produced in the flue gas acid production process decreases and the sulfuric acid production increases,and the exhaust gas can be discharged up to standard after treatment.