Study On The Strength And Heat Transfer Characteristics Of Metallurgical Dust Carbon-containing Pellets At High Temperature Reduction

With the rapid development of the iron and steel industry,the amount of metallurgical dust has increased rapidly.If these dusts are not handled properly,it will not only cause a huge waste of resources,but also cause serious environmental pollution.At present,the rotary hearth furnace technology is the most widely used for processing metallurgical dust.Its metallized pellet products are mainly used in blast furnace production.It is particularly important to increase the strength of metallized pellets;at the same time,the production of metallized pellets is a high energy-consuming process.How to improve the heat transfer conditions of carbon-containing pellets to save the heat energy consumption during the production of metal ized pellets has become an important research topic.This paper focuses on the heat transfer and compressive strength of metallized pellets.In order to obtain metallized pellets with higher strength and good heat transfer conditions,first of all,the thermodynamics of iron oxide reduction and zinc oxide reduction in the reduction process of metallurgical dust carbon-containing pellets are introduced from theory;the reduction characteristics of carbon-containing pellets in an oxidizing atmosphere were analyzed using a two-way gas-solid reaction kinetic model.Then the effects of alkalinity on the compressive strength and melting point of the pellets,as well as the effect of the calcination temperature and baking time of the pellets on the compressive strength of the metalized pellets were systematically studied through experiments;next,the volume shrinkage and weight loss of the pellets during the calcination process were studied,including the effects of calcination temperature and baking time on the volume shrinkage and weight loss of the pellets,and the effect of alkalinity on the volume shrinkage of pellets.For the heat transfer characteristics of the pellets during the reduction process,this paper first uses the metallurgical dust of a steel plant as the experimental raw material,compacts the metallurgical powder through the cylindrical mold,and uses the temperature collection system to conduct experimental research on the heat transfer of the pellet,The effects of different furnace temperatures and different powder alkalinity on the heat transfer of pellets are discussed.Finally,through the establishment of a three-dimensional cylindrical pellet heat transfer mathematical model,the heat transfer process of the pellet in the reduction process was simulated and the model was verified by heat transfer experiments.Through research,the following main conclusions are drawn:(1)The compressive strength of metallized pellets increases first and then decreases with the increase of calcination temperature and calcination time.When the calcination temperature is 1270 ? and the calcination time is 22 min,the metallized pellets have a higher strength.When the basicity of the pellet is less than 1.2,the compressive strength of the metalized pellet decreases with the increase of the basicity;when the basicity of the pellet is greater than 1.2,the compressive strength of the metalized pellet gradually increases.(2)In the heat transfer experiment with different furnace temperatures,the higher the furnace temperature,the heat transfer rate of the pellet will gradually increase.On the center cross section of the 1/2 height of the cylindrical pellet,the surface point,1/2radius point The shorter the time required for the temperature close to the center point to be close to the furnace,the temperature difference between t he points on the cross section of the pellet will gradually increase.When the furnace temperature is 1200? and the heat transfer is carried out to 22 minutes,the temperature of the pellet surface point,1/2 radius point and center point are 1180.2?,1161.2? and 1117.9?.(3)In the calcination experiment with different basicities,with the increase of the basicity of the pellet,the heat transfer rate of the pellet will gradually decrease.The longer the time required for the temperature of the point and center point to be close to the furnace,the temperature difference between the surface and the interior of the pellet will gradually increase.When the heat transfer is carried out to 22 minutes,the temperature of the surface point on the center of the 1/2 high place of the pellets with different alkalinities is not much different,both are around 1180 ?,and the temperature of the 1/2 radius point and the center point of the pellets varies As the alkalinity increases,it decreases.