Modeling Studies On Flow Behavior In Bottom Blown Oxygen Copper Smelting Furnace

Bottom blown oxygen copper smelting process(which is also called as SKS process)is a new bath smelting technique with domestic intellectual property right,which has many advantages such as less investment,short technological process,strong adaptability of raw materials and low energy consumption.So in recent years,this technology has been widely applied in China.However,as a young technology,SKS process still has some inevitable shortcomings and deficiencies,for example,no scientific theoretical basis for the design of nozzle's layout and structure,it is difficult for ore material to be quickly involved into the molten poor,the splash of molten pool cause the clogging of charging hole.These shortcomings hinder the enlarging application of SKS process.In general,these problems are closely related to the fluid flow phenomenon in the furnace.In order to fully tap the potential of SKS furnace,the bottom blown furnace were studied in this paper.Taking an industrial SKS furnace as the prototype,water model experiment,numerical simulation and dimensional analysis are used to investigate the flow field characteristics,the characteristic of gas-liquid mass transfer,and the dispersion states of materials charged into the furnace,and so on.Besides,an air curtain device on feed inlet is designed to research its suppression effects on the splash of molten pool.The conclusions are as follows:(1)Physical simulation experiment was conducted in a slice water model.Characteristics of fluid flow in SKS furnace were observed as follows:Gas column is formed in the liquid phase by the jet injection.The column carries liquids moving upward and erupting from the liquid level,forming a bulge on the liquid surface which phenomenon like fountain.The jet column is unstable,with frequent expansion and contraction appearing near the nozzle exit.When expansion occurs,the jet column will hit the wall around the nozzle,and forms a bubbles ring consisting of large number of small bubbles.PIV technology was used to investigate the flow field in the slice water model.There are two large circulations in the pool.The splash of molten pool mainly appears in the fountain zone above the nominal liquid surface level.Keeping a relatively deep pool will be helpful to reduce the splash and fluctuation of liquid,promote the mixing of fluid and the energy efficiency of jet.With the increase of gas flow rate,the circulations are enhanced and thesplash of liquid also becomes more violent.(2)In the full-length water model,by using the absorption of CO2 in a NaOH solution,the characteristic of gas-liquid mass transfer was investigated.The influence of CO2 volume fraction,initial linear velocity of gas and depth of liquid on the volumetric mass transfer coefficient and the utilization rate of CO2 were researched.The results show that with the increase of the volume fractions of CO2,the volumetric mass transfer coefficient shows an increasing tendency and the utilization rate of CO2 decreases.Increasing the gas initial linear velocity will enlarge the volumetric mass transfer coefficient and utilization rate of CO2,meaning that by increasing the flow rate of air to improve the injection linear velocity will helpful to promote the gas-liquid mass transfer and the efficiency of CO2.When the depth of liquid increases,the volumetric mass transfer coefficient and utilization rate of CO2 will increase.So increase the depth of pool will promote mixing effect of SKS furnace,accelerate the reaction rate and improve the efficiency of gas.(3)By using dimensional analysis method on the influence factors of the volumetric mass transfer coefficient AK,an empirical formula about AK and related bottom blown parameters was established:By using dimensional analysis method,an empirical formula about the utilization rate of CO2 and related bottom blown parameters was established:The two formulas are in very good agreement between those calculated values and experimental values.The two formulas are suitable for the bottom blown furnace whose length-diameter ratio is 4.3:1 and the number and layout of nozzles should be same as the first furnace of Fangyuan Corporation.(4)By water model experiment,air curtain devices were made to investigate the influence of curtain's gas flow rate,diameter of orifice and number of orifice on the suppression of liquid splash.The results are as follows:in the same gas flow rate of curtain,when the diameter of orifice increases,the splashing capacity which can reach the feed inlet will increase.If the gas flow rate of curtain increases,the splashing capacity will decrease.With the decrease of orifice number,the splashing capacity decreases.The essence of the change of curtain's gas flow rate,the diameter and number of orifice is to change the gas velocity out of the orifice.The splashing capacity decreases with increasing the gas velocity.(5)Based on physical simulation experiments,the dispersion states of materials charged into the furnace were researched.The influence factors considered are as follows:gas flow rate of bottom blown,diameter and installation angle of nozzle.Experiment results show that the entrainment effect becomes better with the increase of bottom blown gas flow rate.In the same gas flow rate,increasing the diameter of nozzle will gain a better dispersion state of materials.When the 2.5 mm diameter of nozzle was used,the larger installation angle of nozzle will improve the entrainment effect.For 5.92 mm diameter nozzle,there is a contrary tendency.(6)A numerical model of bottom blown furnace was proved to be reasonable by the physical simulation experiment and numerical study was performed for the furnace in industrial conditions.The results show that when using single nozzle,with the increasing distance from the center of nozzle,the velocity of fluid decreases rapidly.The effective stirring radius of single nozzle is less than 1 m.The stirring effect of two nozzles with a distance of 0.65 m was investigated and the results show that the whole molten pool between the two nozzles can form stable circulations.Compared with single nozzle,the overall flow velocity of the pool has a great improvement.