Mechanism And Suppression Method Of Dust Accreting In Copper Flash Converting Furnace

Due to the advantages of large capacity,low energy consumption,high degree of automation and environmental protection,the double flash furnace copper smelting process has become one of the preferred processes for new copper smelters at home and abroad in recent years.In the industrial production process of flash converting furnace,the high dust rate and the characteristics of easy adhesion of dust cause the continuous accumulation of dust on the inner wall of the flue gas system to form accretions,which will block the flue and reduce the dust collection efficiency in serious cases,affecting the normal production.However,the composition and phase characteristics of the flue dust of the converting furnace are different from the matte smelting flue dust,and the related research work on its bonding behavior is rarely reported.Therefore,the research on the bonding mechanism and the suppression technology of the flash converting furnace dust is carried out.The stable operation of the converting process is of great significance.In this paper,flash converting furnace dust and furnace structure are the main research objects,combined with on-site sampling,theoretical simulation calculations,and laboratory tests,etc.,to analyze the composition and phase characteristics and the dynamic change law of the dust exhaust process,and clarify the adhesion of dust.The formation mechanism of furnace junctions and possible furnace junction suppression methods are proposed.The main conclusions are as follows:（1）The analysis and test results of the dust samples at each position of the dust exhaust path show that,the morphology of the dust samples at each position of the sedimentation tank and electrostatic precipitator is mainly spherical or quasi-spherical,and the particle size distribution is normal.The dust enter the sedimentation tank from the reaction tower,the phase is mainly liquid Cu₂O or liquid CuFe_xO_y and solid Cu₂O coexisting core-shell structure,mixed with a small amount of volatile impurity elements such as Pb,Zn,As,etc.The dust particle size range is 0.5-300μm.When the dust enters the rising flue,the temperature decreases,the solid Cu₂O increases,and the liquid CuFe_xO_y decreases,dust particle size range 0.2-80μm.The dust enters the waste heat boiler,the temperature decreases drastically,and the volatile impurity elements such as Pb,Zn,As are easily aggregated and precipitated,and the large dust particles settle,and the dust particles are oxidized and sulfided reaction,part of Cu₂O produces Cu O or Cu O·Cu SO₄ intermediate product,the particle size of the dust particles is larger,and there are more large agglomerated particles.When the dust enter the electrostatic precipitator,the temperature continues to decrease,and the dust particles are completely sulfated,basically Cu SO₄,and the fine dust particles are settled and collected in the electrostatic precipitator.The dusts are spherical,small and uniform in size,ranging from 1-10μm.（2）The test results of dusts and accretions sample detection,thermodynamic simulation calculation of the dusts cooling process,and experimental research on the melting characteristics of dusts and accretions show that,the dust phase of the rising flue is mainly a core-shell structure with liquid CuFe_xO_y and solid Cu₂O coexisting.At the interface between the rising flue and the waste heat boiler,the temperature drops,the solid Cu₂O increases,and the liquid CuFe_xO_y on the surface of the Cu₂O particles decreases.The dusts has not completely solidified into a solid state,Pb,Zn,As and other volatile impurity elements on the surface of the dusts particles are precipitated on the surface.At the same time,due to the turning of the dusts,the collision probability of the dust is greatly increased.The semi-molten dust adheres to the water wall through thermal migration and inertial migration,forming an initial layer,the initial layer is made of continuously adhering and migrating dust particles.The dust cannot flow down naturally,and it continues to stick and grow over time,forming accretions that is difficult to clean.The accretions interface continuously moves to the center of the flue gas,and the heat release rate of the dust at different positions is different,a temperature gradient is formed inside the accretions,and different phase transition processes occur.（3）Thoughts on suppression measures for accretions and experimental research results.There are two main methods to suppress the formation of the rising accretions:One is to reduce the production of liquid CuFe_xO_y in the outer layer of the dust particles,so that the dust particles become completely solid,and the adhesion of the dust is reduced,and a bonding layer cannot be formed on the inner wall of the flue,and accretions cannot be accumulated and grown.Such as lowering the temperature,adding inhibitors and so on.When the temperature is below 1100℃,the Cu and Fe oxides in the dusts cannot react to form liquid CuFe O₂.Adding Mg O as an inhibitor to the dust,Mg O reacts with the dust to form Mg Fe₂O₄,which replaces the liquid CuFe O₂ in the dust.Adding a mixed inhibitor of Mg O and Cr₂O₃ to the dust is similar to the reaction of adding Mg O as an inhibitor,and at the same time,a small amount of Mg Cr₂O₄ and Mg Fe₂O₄ solid solution are generated.The second is to increase the liquid state of the outer layer of the dusts particles,and the increase of the liquid phase increases the fluidity of the dusts particles.With the accumulation of the dusts particles,the dust naturally flows down into the sedimentation tank below,and cannot accumulate and grow on the inner wall of the ascending flue.For example,adding a Ca O inhibitor to the dust,Ca O acts as a flux to lower the melting point of Cu₂O,the partially melted Cu₂O is mutually soluble with the liquid CuFe_xO_y in the accretions.