Numerical Study Of Gas-Solid Heat Transfer On Roasting Shaft Furnace For Vanadium Titano-magnetite In Western Liao-ning Province

Roasting shaft furnace is the key equipment in directly vanadium recovery process for vanadium titano-magnetite in western Liao-ning province.The essence of roasting is vanadium titano-magnetite is heated by the hot combustion products,and then cooled by the cold air.As the key to enhance the effect of roasting is improving the effect of gas-solid heat transfer in moving material bed,get a good grasp of gas flow rules and gas-solid heat transfer rules can fundamentally improve the shaft furnace roasting effect.Therefore,a numerical calculation was carried out to explore the gas flow and gas solid heat transfer rules in shaft furnace on basis of predecessors' workings in this paper and then could provide guidance for actual shaft furnace in the moderate scale experiment.In essence,it should be set of the gas-solid heat transfer problem in moving bed to explore the gas-solid heat transfer process in the shaft furnace.However,the current numerical studies of gas flow and heat transfer in moving bed are not perfect,such as the similar calculation models are confined in the blast furnace or pelletizing shaft furnace,which have large differences with the roasting shaft furnace for the more gas imports and exports.Besides,The heat transfer theory is limited to local thermodynamic equilibrium theory,which result in a poor practicability for only calculate the gas-solid average temperature.Flow theory is confined to classic Ergun formula which lack in pertinence but appear more general.Such characteristics have certainly affect the reliability of numerical results,which lead to the lack engineering application.An experiment platform was built to determine the state of flowing gas in the shaft furnace based on the above backgrounds.And then,a heat transfer model based on the local thermodynamic non-equilibrium theory was built,the double energy equations in non-equilibrium model was deduced which suitable for steady heat transfer process in roasting shaft furnace.Once more,Through the secondary development of FLUENT software,the heat transfer mathematical model in moving bed and the heat release in chemical reaction processes are complied by the user-defined functions.At final,a comparison of test data in the moderate scale experiment with the numerical results was carried out and the influences of operating parameters on the roasting process in shaft furnace were discussed,and then theoretically analyses of some onsite causes were developed and some improvement opinions were given.Some conclusions are draw as follows,(1)The critical Reynolds number of flowed gas in roasting shaft furnace is about 2100,and the modified Ergun equation which applicable to describe the turbulent fluid flow is,?p/L=500(1-?)2/?3?u/d2+2.1(1-?)/?3?u2/d(2)The temperature of vanadium titanium pellets is more higher which near the roasting tuyere,but lower while away from the roasting tuyere in the same horizontal plane.In addition,the temperature of pellets is lower in bottom of soaking zone because of the counter-flow of cooling gas.(3)Pellets temperature increased with the increase of roasting wind volume,but decreased with the increase of cooling air volume in the adjustable range of production.The influence of particle diameter to pellets temperature is with the increase of pellets diameter,pellets temperature is lower which in the heating section,while increased in the cooling section.(4)Low pellets temperature in shaft furnace can be solved by adjusting the roasting and cooling air volume,which no need to adjust the structure parameters.The production of pellets in existing equipment should be appropriately decreased,but not less than 264t/a with synchronizing change the roasting air volume.The import congested problem can be solved by setting the protection brick body which is good for improving the effect of roasting at the same time.The double inlets of roasting gas is better than the single import model,which can be imposed.(5)The suitable parameter combination is roasting air volume of 3500m3/h,and cooling air volume of 1512m3/h,which heat preservation time of 5.0h when annual output of 330t(V2O5)/a.Besides,The suitable parameter combination is roasting gas volume of 2800m3/h,and cooling air volume of 1512m3/h,which heat preservation time of 6.0h when annual output of 264t(V2O5)/a.