Research On Corrosion Mechanism And Predictive Model Of Heat Exchangers In Waste To Energy Plant

With the rapid development of China's economy and the continuous advancement of urbanization,the size of cities the population of cities has continued to increase,and the municipal solid waste has also increased.Waste incineration power generation technology is slowly replacing traditional landfill treatment methods and becoming a new method of harmless waste treatment because it meets the principles of recycling,harmlessness,and reduction of waste treatment,and has the advantages of rapid capacity reduction and energy recycling.However,due to the complex composition of municipal solid waste,the flue gas generated from waste incineration contains a lot of corrosive gases,such as HCl,SO₂,H₂S,and a large number of low-melting alkali metal salt particles such as Na and K salts.Corrosive gases and alkali metal salts are deposited on the heating surface,which causes high-temperature corrosion,ash deposition,and slagging on the heating surface of waste incineration.With the continuous improvement of boiler parameters,the corrosion,ash deposition and slagging of the heating surface of the waste incineration boiler become more and more serious,and even the heating surface will burst.In view of the above problems,this article designed orthogonal experiments in the laboratory to simulate the flue gas environment in the waste incinerator to investigate the influence of various factors on the corrosion of the heating surface,and ranked the effects of each factor from large to small according to the results of the orthogonal experiment.Based on laboratory research,on-site sampling and analysis of waste incinerators were conducted to investigate the corrosion status of various high-temperature heating surfaces and the surface structure and element composition of the corrosion layer.The results of laboratory corrosion weight gain were fitted,and a gray system model and regression model for each operating condition were established to determine the relationship between the amount of corrosion and temperature,metal materials,HCl concentration,SO₂ concentration,and O₂ concentration.The main conclusions are as follows:The effects of temperature,metal material,HCl concentration,SO₂ concentration,and O₂ concentration on the corrosion weight gains were orthogonally tested,and the following rule was obtained:The influence of each factor on the index can be ranked according to the significance,which from large to low were temperature,metal material,SO₂ concentration,O₂ concentration,and HCl concentration.The corrosion resistance of spraying materials is related to environmental factors,but because the experimental conditions of the four groups of experiments are completely different,it cannot be completely determined which factor plays a decisive role.that Inconel686Inconel 625,Inconel 622 are used as surfacing layers,and 12Cr1MOV is used as the base material,the material's corrosion weight gain rate is still very different;it can be considered that the order of the corrosion resistance of the existing three materials from high to low is Inconel 622,Inconel625,Inconel 686.The results of on-site sampling analysis show that the main form of corrosion in high-temperature reheaters is the high-temperature corrosion of S,and the products are mostly metal sulfates,forming low-melting eutectic sulfate mixtures,while the main forms of corrosion in high-temperature superheaters are The main products of high temperature corrosion of Cl are FeCl₂,CaCl₂;the main form of Low temperature reheater‘s corrosion is oxidative corrosion of metal Fe,and the main products are Fe₂O_3,etc.The presence of S and Cl in the waste incinerator will cause corresponding corrosion reactions to occur.This pattern is related to temperature.Cl corrosion mainly occurs in the temperature range of 520?to 610??High temperature reheater?,and S corrosion mainly occurs in the temperature range of 600?to 670??High temperature superheater?.When S and Cl exist at the same time,it may be a mutual inhibition of the occurrence of corrosion;the alkali metal element K in the waste incineration flue has a certain promotion effect on the occurrence of Cl corrosion;the occurrence of S and Cl corrosion reactions may be related to the cracks or pores on the oxide layer.Corrosion Elements react directly with the metal matrix through cracks or pores.The grey system theory was used to fit the measurement results of the laboratory orthogonal experiments.The experimental data were fitted by the GM?1,1?model and the grey linear regression model method,and the fitting results were comprehensively synthesized.Finally,a nonlinear regression prediction model of the final corrosion weight gain results under various conditions is established by EXCEL regression fitting.The obtained correlation coefficient is 0.96,and the average value of the relative error of the model is 14%.The model fit is relatively high.