Study On Thermal Parameters Of Roasting Shaft Furnace For Direct Vanadium Extraction From Vanadium-Titanium Magneticite

Direct vanadium extraction proposed by our research group with the intellectual property rights,is aimed at high vanadium and titanium low iron vanadium-titanium magnetite concentrate of Liaoning province.It adopt to produce vanadium products directly without process of vanadium extraction from converter steelmaking.Aiming at the defect of existing rotary kiln,such as low material filling rate and bad raw material adapt ability,direct extraction of vanadium roasting shaft furnace is proposed by our research group as a kind of vertical roasting equipment referring to pelletizing shaft furnace in steel domain.It owns the merits of small volume,low initial investment and convenient operation.From the point of the heat,roasting shaft furnace is a typical gas-solid counter current vertical particle bed,which is subordinate to moving bed layer.In vertical furnace,oxidizing roasting reaction of oanadium-titanium magnetite pellet and air is accompanied with chemical reaction heat.According to three kinds of variable relations,the structure and operating parameters of roasting shaft furnace impact gas flow and gas-solid heat transfer process,and then have influences on quality and yield of the furnace.Based on this,aiming at the deficiencies of early stage of the numerical calculation model in our research group,such as chemical reaction heat and pelletizing temperature is not coupled,viscous and inertia resistance coefficient reliability is insufficient,established coupled chemical reaction heat and pelletizing temperature and introduced numerical calculation model of revised viscous and inertia force coefficient.At the same time,a pilot furnace shaft with roasting area of 1m2 was designed and set up.Based on this,a series of gas-solid heat transfer experimentwere carried out and numerical calculation model is verified,groping for the part of the gas-solid heat transfer law.The main research contents,conclusions and innovations are as follows:Firstly,the test bench was built by ourselves.We carried out resistance characteristic experiment about gas Passing through pellets seam.The results showed that when apparent particle velocity is controlled in adjustable range of production 0.1～0.7m/s,viscous and inertia coefficient of pellet are 2.443×105 and 1281.8 respectively.Also the most important factors effecting pellet bed resistance are apparent particle velocity,size and distribution of voidage.Controlling the rate of ore fines is the most favorable measures to reduce the resistance characteristics.Secondly,The 3-D steady gas-solid heat transfer numerical model was established.Main innovations of the model are that describing the down speed of pellets by UDF,based on local thermodynamic equilibrium model.The steady state calculation in the 3-D area was realized,adopting experimental viscous force and inertial force coefficient,the disadvantages of using general formula of Ergun were overcomed.Simultaneously,editing chemical reacting source term again,the temperature of chemical reacting heat source is coupled with pelletizing temperature.This model is an universal model which could be used for subsequent large-scale producting shaft furnace.Thirdly,taking the example of pilot furnace in a enterprise,combining numerical calculation and experimental results,it could be known that the main factors influencing the shaft furnace gas-solid heat transfer are roasting air volume and cooling air volume,namely,upper and lower gas-solid water equivalent ratio.In the adjust range of the production,with the increase of roasting air volume,temperature of the pellets in preheating section calcination section and soaking zone all have been improved significantly,the temperature in cooling zone had no obvious change.With 5%increase of upper gas-solid water equivalent ratio,temperature of the pellets in preheating section rise by an average of 23 K,temperature in roasting soaking zone rise by an average of 15.4K.With the increase of cooling air volume,temperature of the pellets is declining trend in pilot furnace shaft.With 5%increase of lower gas-solid water equivalent ratio,temperature of the pellets drop by an average of 24.1 K.Fouthly,Taking a judgment is based on 4h roasting time and roasting temperature of 900～1150℃.It could be known that maximal utilization factor of pilot furnace shaft in enterprise is 1.3t/m2·h at present.In this moment,roasting air volume of 446m3/h and cooling air volume of 350m3/h is equivalent to upper and lower gas-solid water equivalent ratio of 1.06 and 0.41 respectively.When utilization factor is 1.2t/m2·h,the suitable operating parameters are roasting air volume of 428m3/h and cooling air volume of 350m3/h,which is equivalent to upper and lower gas-solid water equivalent ratio of 1.08 and 0.45.When utilization factor is 1.0t/m2·h,the suitable operating parameters are roasting air volume of 357m3/h and cooling air volume of 350m3/h,which is equivalent to upper and lower gas-solid water equivalent ratio of 1.05and 0.53.