Study On Formation Mechanism Of High Strength Nodule In Evaporative Cooler Wall Of Converter Dry Dust Removal System

In order to avoid environmental pollution,many steel plants adopt the converter dry dust removal system for dust removal.The dry dust removal system has the advantages of high dust removal efficiency,low energy consumption,low operating cost,less occupation of land and easy recovery and treatment of smoke and dust.However,the wall of evaporative cooler in dry dedusting system of converter will form high-strength scales,which will hinder the flow of flue gas in evaporative cooler and affect the smooth running of converter dedusting equipment,thus affecting the steelmaking process.This problem has not been effectively solved.Therefore,in this paper,the chemical composition and element distribution of high-strength scales in evaporative cooler wall are tested,the forming conditions of scales are analyzed,and the experimental verification is carried out.Finally,the forming mechanism of high-strength scales is summarized,and the solutions to reduce the formation of scales are put forward.Firstly,by studying the physical and chemical properties of scales and dust removal dust,it was found that there were iron oxides,ZnFe₂O₄,ZnO,NaCl,KCl and other substances in the scales.At the same time,it was found that the content of Zn in the scales was more than twice as much as that in dust removal dust,and the intensity of the scales was higher.The main reason is that the zinc material is brought in by galvanized sheet in converter steelmaking process.At high temperature,zinc vapor is formed by gasification of zinc element.With the air flow entering the evaporative cooler,zinc vapor is liquefied and adhered to the wall of the evaporative cooler,oxidized to zinc oxide,and reacts with Fe₂O₃ in dust removal dust at 600?to form ZnFe₂O₄,which is the main reason for the formation of high-strength scale.In addition,low melting point substances NaCl and KCl adhere to the cooling stave to adsorb iron oxides in the dust,promote the solid-solid oxidation-reduction reaction between iron oxides,generate bonding and form scales.The experimental results show that the strength and bonding effect increase with the increase of NaCl,KCl,ZnO content and sintering time.Among them,the effect of ZnO is the most obvious.The main reason is that the content of ZnO affects the formation of ZnFe₂O₄.In addition,increasing sintering temperature can also enhance the strength and bonding effect of the scales.The most obvious enhancement effect of the experiments with zinc oxide is at 600 and 900 C.The main reason is that the formation of ZnFe₂O₄ begins at 600?,and the formation rate will be greatly increased at 900?.Through analysis and experimental verification,there are two ways to effectively reduce the formation of high-strength scaling in evaporative cooler wall:1.Controlling the content of NaCl,KCl and Zn entering the dust removal system;2.Reducing the production of ZnFe₂O₄ by controlling the temperature of evaporative cooler.