Ferrosilicon Alloy Granulation Process Based On Water Curtain Cooling

With the saturation of output in iron and steel industry,market competition intensifies.It is required that the iron and steel industry must put the improvement of product quality and accuracy in the first place.As one of the basic burden in iron and steel industry,ferroalloy is indispensable in iron and steel production process,which is often used as deoxidizer and alloy additive in steelmaking process.The production,variety and quality of ferroalloy directly affect the production and development of the iron and steel industry.So,ferroalloy is added to the converter must be required to meet some requirements:moderate particle size,uniform distribution of elements,high purity and so on.The ferroalloy particles are usually inhomogeneous composition,serious segregation and high pulverization rate by traditional ferroalloy granulation process.Therefore,a centrifugal granulation process based on water curtain cooling is proposed for the production of ferroalloy particles,which takes into account the quality control of ferroalloys on the basis of improving production efficiency.In this paper,take FeSi75 alloy as object,study the cooling and solidification process of high temperature ferrosilicon alloy particles.Centrifugal granulation experiments are carried out to study the effects of water curtain cooling on distribution,morphology and oxidation of ferrosilicon alloy particles.The conclusions are as follows:? The solidification process of high temperature ferrosilicon alloy droplets are numerically simulated by COMSOL Multiphysics to analyze the effects of particle size,temperature,air velocity,ambient temperature and cooling medium on the solid-liquid phase evolution of ferrosilicon particles.The results show that the solid phase first forms at the bottom and tail of particles because the boundary layer at the bottom and tail of particles is very thin and the rate of heat transfer is fast.The droplet diameter of ferrosilicon alloy has a great influence on the cooling process.With the increase of the droplet diameter,the moving speed of the phase interface becomes slower and the solidification time increases.The solidification time of the droplet is 7.59 s when the diameter is 10 mm and 14.95 s when the droplet diameter is 20 mm.With the increase of the initial temperature of the droplet,the initial solidification time of the solid phase delays,solidification time prolongs.The solidification time is 10.93 s at the initial temperature of 1623K and 11.89s at the initial temperature of 1773K.The influence of wind speed and ambient temperature on the cooling process of droplets is small.The influence of water cooling on the cooling process of droplets is great.Water cooling has a great influence on the cooling and solidification process of droplets.The solidification time of droplets in water cooling is only 0.78 s,the temperature drop rate is about 1200 K/s.The solidification time of droplets in air takes 10.93 s,and the temperature drop rate of droplets after solidification is about 132 K/s.? The solidification process of high temperature ferrosilicon alloy particles in water curtain environment are numerically simulated by COMSOL Multiphysics.The results show that with the increase of water content in the water curtain environment,the solidification time of droplets decreases and the moving speed of phase interface increases.The solidification time of ferrosilicon alloy particles cooled in different water curtain conditions were calculated and fitted to construct solidification time curve(60%solid phase fraction of the droplets):y0.6=2.44839-1.01462 In(vw-0.00582)Solidification time curve(100%solid phase fraction of the droplets):y1=3.76535-1.37678 ln(cw-0.00596)Under the condition of water curtain cooling,when the volume fraction of water is 8%,the time required for solid fraction to reach 60%is 0.73s.? Centrifugal granulation experiment of water curtain cooling was carried out to study the effect of water curtain on particle size distribution of ferrosilicon alloy after granulation.The result shows that water curtain cooling can reduce the splitting phenomenon of the high temperature ferrosilicon droplets in flight.The larger the flow rate of water curtain,the larger the proportion of large-sized ferrosilicon alloy particles collected.Under the experimental conditions,the optimum technological condition for producing ferrosilicon alloy particles is 12 L/min water curtain flow,12 mm nozzle diameter and 200 rpm rotating speed.Statistical results show that the proportion of particle size greater than 8 mm is more than 70%and particle size below than 4mm less than 10%.?The phase and element distribution of granulated ferrosilicon alloy particles were studied.It is found that the phase of ferrosilicon alloy particles is Phase Fe and FeSi2.The outer surface of ferrosilicon alloy is oxide layer.The oxide layer thickness increases with the increase of particle diameter.The oxide layer thickness of ferrosilicon alloy particles with 6 mm diameter is about 5 um,the oxygen content is 0.12%.The oxide layer thickness of ferrosilicon alloy particles with 8 mm diameter is about 10 um,the oxygen content is 0.18%.The main components of the oxide layer are Al2O3,SiO2,CaO and so on.? The effect of water curtain cooling on the physical properties of ferrosilicon particles was investigated.The results show that with the increase of water curtain flow rate,the cooling strength increases,the grain size of ferrosilicon alloy decreases,and the phase composition becomes more uniform.It shows that the centrifugal granulation process with water curtain cooling can eliminate the segregation of raw material effectively.In summary,this paper theoretically studies the evolution of solid-liquid phase during the cooling process of ferrosilicon alloy droplets under different conditions by simulation.And the effect of water curtain cooling on the particles in the centrifugal granulation process of ferrosilicon alloy is experimentally explored.The results have a good guiding significance for the development and design of centrifugal granulation process of ferrosilicon alloy based on water curtain cooling.