Fundamental Study On The Removal Of Zinc Oxide From Blast Furnace Dust By Low Temperature Carbonthermal Reduction

Iron and steel industry of the blast furnace dust contains rich iron and carbon,it is the most common ways of utilization as the sintering burden to return to the blast furnace,recycling is easy to cause many times more than 0.5%of zinc content in sintering material,more than zinc blast furnace load,not only can reduce the gas utilization efficiency,can also lead to the blast furnace of nodules,reduce the useful service life of blast furnace,Therefore,the blast furnace dust needs to be dezinc treated before being used as sintering raw material for reprocessing.Therefore,the efficient resource utilization of blast furnace dust is an urgent problem to be solved in the iron and steel industry.From the technical means and commercialization degree,rotary kiln technology is the most widely used.However,the high-temperature operation of the rotary kiln process at 1300°C will not only lead to high energy consumption,but also lead to the formation of low melting point compounds,which will damage the rotary kiln lining.The key of dezinc in rotary kiln lies in the reduction of zinc oxide by carbothermal process,which is completed by CO reduction of zinc oxide and carbon gasification reaction.Both of them are gas-solid reactions,and the content of CO and CO₂ in the gas phase is closely related to the reaction rate.In view of these problems in rotary kiln process,the gas release behavior in the process of reducing zinc oxide under different conditions was studied firstly.Taking the decarbonized blast furnace dust as the research object,the effects of temperature and dezincification rate on the morphology and particle size of the residue after decarbonization were investigated.The main conclusions are as follows:（1）In the reaction process of carbonaceous materials with zinc oxide,the faster the CO release rate,the higher the gasification activity of carbonaceous materials,the higher the dezincification quantity;The CO release rate can be increased by decreasing the particle size of raw materials,increasing the molar ratio of C to Zn O,decreasing the mass of raw materials and decreasing the bulk density of raw materials.Using high active carbon material,decreasing carrier gas flow rate and increasing carbon content in raw material can reduce the initial reaction temperature of carbon thermal reduction of zinc oxide.（2）After decarburization,the blast furnace dust contains a large amount of Fe elements,as well as a large amount of Zn,Al,Ca and Si elements.The main phases are Fe₂O₃ and Fe₃O₄.The particle size mainly ranges from 0.2 to 185μm,and 90%of the particle size is less than 51.3μm.（3）In the process of reducing blast furnace dust by corn cob coke,the particle size of residue after reaction increases with the increase of dezincification rate.At the same dezincification rate and different temperatures,the lower the heating rate is,the lower the terminal temperature is D10 and D50 decrease with the slowing of the heating rate,and the particles with smaller particle size are reacted first.The carbon thermal reduction reaction starts from the surface of the blast furnace dust particles to generate voids,and then reacts to the interior,where whisker iron is generated on the surface of the particles.（4）The macroscopic kinetics of dezinc of blast furnace dust was established.The reaction kinetics model was D₃（three-dimensional diffusion model）,the reaction rate was controlled by diffusion steps,the apparent activation energy was 358.90 k J·mol^-1,and the pre-exponential factor was 6.73E+15 min^-1.The kinetic equation was as follows:（?）...