Study On The Application Of Control Strategy For Air Distribution And Flue Gas Oxygen Content In Brick Tunnel Kiln

The brick and tile industry is my country’s traditional industry and one of the basic industries of my country’s building materials industry.As the country implements energy conservation and emission reduction policies for non-electric industries,the environmental protection standards of the brick and tile industry have become increasingly strict,and the brick tunnel kiln has developed rapidly in recent years.As an industrial furnace with high degree of automation,high output and good working conditions,it was widely used in industries such as bricks and tiles,refractory materials and ceramics.However,the low thermal efficiency of the tunnel kiln and the high oxygen content of the flue gas have severely restricted the development of the tunnel kiln.At present,the flue-heat separation system has a significant effect in controlling the oxygen content of the flue gas of the tunnel kiln.This paper takes the brick tunnel kiln with an annual output of 60 million pieces as the research object,uses numerical simulation method to carry out the numerical simulation analysis of the brick tunnel kiln,and verifies the reliability of the numerical simulation through field measurement.The control effect of the smoke-heat separation system was compared and analyzed through the numerical simulation results of the smoke-free heat separation tunnel kiln and the smoke-heat separation system tunnel kiln.The various influencing factors of the flue-heat separation system are studied.On this basis,the influence weights of the various influencing factors of the flue-heat separation system are obtained through orthogonal experiments,and the control of the flue-heat separation system is proposed on the basis of orthogonal experiments.Method,carried out on-site operation test.The main conclusions drawn from this paper are:（1）Combining with the type of brick sintering furnace recommended by the national industrial policy（tunnel kiln）,the basic structure,working principle and technological process of the tunnel kiln are described.Combined with the compilation of the"Brick and Tile Industry Air Pollutant Emission Standards",the reasons for the current excessive emission of pollutants by brick and tile enterprises are analyzed,and the necessity of controlling the oxygen content of the flue gas and the control methods are analyzed.According to the analysis of the current research status of tunnel kilns at home and abroad,the research method of numerical simulation is determined in this paper,and the feasibility of smoke-heat separation is analyzed and verified according to the brick production process,and the evaluation index of smoke-heat separation system is proposed.（2）According to the actual situation of the brick tunnel kiln,the bricks in the kiln are simplified by the equivalent drag coefficient method to simplify the bricks into porous media areas.The porous media parameters of the bricks are determined by Darcy’s law and the porous media parameters are corrected.（3）The numerical simulation method of the tunnel kiln smoke and heat separation system was verified through field tests,and the field test data was numerically simulated.The numerical simulation results are in good agreement with the field test.Numerical simulation results compared with field test data have a negative deviation of 14.12%for exhaust air volume,a negative deviation of 0.48%for temperature,a positive deviation of 12.38%for waste heat extraction,and a positive deviation of 2.14%for temperature,laying the foundation for the orthogonal experiment to determine the control strategy.The smoke-heat separation tunnel kiln and the smoke-heat separation system tunnel kiln smoke exhaust system are compared,and the results show that the smoke-heat separation system can reduce the exhaust air volume by about 50%,which is basically consistent with the engineering practice results.The flue-heat separation system reduces the heat loss of the exhaust gas of 7.74×105k Cal·h-1,which is of guiding significance for controlling the oxygen content of the flue gas and improving the overall thermal efficiency of the brick and tile enterprise.（4）Through the single-factor numerical simulation test on the influencing factors of the smoke-heat separation system:exhaust fan,waste heat fan,quench fan and cooling fan,the test results are analyzed,and the results show that:Reducing the pressure of the exhaust fan is beneficial to reduce the oxygen content of the flue gas and increase the waste heat to extract heat;increasing the pressure of the waste heat fan is beneficial to increase the amount of waste heat extraction and reduce the oxygen content of the flue gas;improve emergency cooling fan air flow will help improve the heat out of the heat,do not help to reduce flue gas oxygen content;improve the cooling fan air flow will help improve the heat out of the heat,it does not help to reduce flue gas oxygen content.（5）Design four factors and five levels orthogonal experiment,the effects of various factors on the exhaust air flow and heat extraction and heat significance of optimum operating parameters program,based on this,a strategy for regulating and controlling the oxygen content of the tunnel kiln flue gas was formulated,and field operation tests were carried out.The research results showed that:Effect on the exhaust air volume of the right weight factors order of A>C>B>D,i.e.impact pressure exhaust fan maximum weighting factor is 0.58;four factors influence of heat extraction is a weighting factor sequence C>D>A>B,i.e.,affect the amount of air chiller acute weighting factor up to 0.75;the optimal operation plan for each influencing factor is test number five,that is,the test plan is A₁B₅C₅D₅;Formulated a control strategy that only adjusts the factors that have a significant impact on the oxygen content of the flue gas while ensuring the normal production of the tunnel kiln,and controls the oxygen content of the flue gas at a lower level,the on-site operation of the regulation strategy is that the oxygen content of the flue gas is reduced from 18.24%before regulation to 16.57%～17.12%,and the flue gas volume is reduced from 24000 Nm³?h^-1 to 19000 Nm³?h^-1～20000 Nm³?h^-1.After the tunnel kiln exhaust fan operation optimization and adjustment,tunnel kiln has been stable operation for six months,stability control flue gas oxygen content of 16%to 17%,the level of air pollution control to the domestic industry with the advanced level.