Research On Jet Impact Crushing In Ferroalloy Granulation Process Furnace

With the development of modern science and technology,various industries have higher and higher requirements for the variety and performance of steel.In the steelmaking process,there are certain requirements for the particle size of the ferroalloy added.A smaller particle size can reduce the melting time of adding to the molten steel and improve the uniformity of the distribution of alloying elements in the molten steel,but too small a particle size will be difficult to penetrate over the slag layer.The traditional ferroalloy granulation process is through the method of pouring first and then crushing,which will cause greater environmental pollution during the production process,and the uniformity of the particle size obtained is poor.The foreign GRANSHOT granulation process has a high degree of automation,low pollution and uniform particle size.This paper studies the granulation process in this process.First,use the coupled level set-volume of fluid method(CLSVOF method)to simulate the process,determine the overall granulation process,and study the mechanism of crushing.Subsequently,the overall granulation process is divided into the liquid film spreading process in the granulator an d the liquid film breaking process outside the granulator.Taking Sn-58Bi as the research object,the influence of the process parameters on the particle size,crushing time,crushing position,etc.influences.The conclusion of the paper is as follows:It is more difficult for the jet to hit a flat wall to produce splashes.As the jet velocity increases,the spreading speed increases.In the process of the jet impacting the liquid film,when the jet velocity is low(4.35m/s),only crown splashes appear;when the jet velocity is high(10m/s),obvious splashing occurs.In order to explain the breaking mechanism,a comparative study was conducted with the process of droplets impacting on a flat wall and the process of droplets impacting on a liquid film,and obtained:The occurrence of splashing requires uneven impact conditions,resulting in a partial velocity of separation from the wall,and then a free liquid film.And then turbulence with the air to break into droplets.The existence of the liquid film causes the discontinuity of movement and promotes the generation of splashes.The non-uniformity of droplet impact results in a different way from jet impact fragmentation.When the droplets impact the liquid film,the free liquid film is generated first,then the finger jet is generated,and finally broken into liquid droplets.The jet impact liquid film breaking is to first produce a free liquid film,then produce a ribbon-shaped liquid filament,and then break into liquid droplets.The crushing process is determined by simulating the jet impacting the plane of the limited area as the jet impacting the granulator.A liquid film is formed on the surface of the granulator.After the liquid film separates from the wall surface,it interacts with the air and breaks into droplets.Numerical simulation of the flow process in the jet impact granulator is carried out,and it is obtained:With the increase of the impact velocity,the pressure on the surface of the granulator increases,which is a quadratic function relationship with the impact velocity,and the velocity at the edge of the granulator increases.The thickness of the liquid film at the edge of the granulator changes little.Changing the jet diameter and the diameter of the granulator can change the thickness of the liquid film at the edge of the granulator.When the diameter of the jet is 80mm-140mm,when the diameter of the granulator is 200mm-300mm,the jet velocity is about 1.5m/s.The calculation formula of the thickness and flow velocity at the edge of the granulator:v1=1.2v0 h=0.2d02/d1According to the wave theory,the breaking process of the free liquid film under air disturbance is analyzed,combined with the calculation formula of the thickness and flow velocity at the edge of the granulator,a mathematical model is established,and the diameter,broken position,and broken time of the broken droplets are written in python language.The prediction program is calculated:When the diameter of the granulator is about 200mm,the thickness of the liquid film at the edge of the granulator is about 7mm(the jet diameter is about 80mm),and the obtained particle size is about 10mm,which meets the production requirements.When the jet flow rate increases,the diameter of the droplets obtained by crushing decreases but is not obvious,the crushing time is shortened,and the movement trajectory changes.When the thickness of the liquid film at the edge increases,the diameter of the droplets obtained by crushing increases,which has little effect on the crushing time.Since the centrifugal granulation process and the crushing method of the direct impact granulator in this article are both membrane crushing process,this program is used to predict the centrifugal granulation process,and the results show that when the speed is high(6000rpm),it can be applied to powder Metallurgical production of coarse powder(150～500μm).The thickness and flow rate of the liquid film on the edge of the granulator are determined by the flow rate,the rotation speed and the diameter of the granulator.When the flow rate increases,the thickness of the liquid film at the edge of the granulator increases,the breaking time increases,the width of the liquid film increases,and the droplet diameter increases.As the speed of the granulator increases,the thickness of the liquid film at the edge of the granulator decreases,the breaking time decreases,the width of the liquid film decreases,and the droplet diameter decreases.This study compiles the prediction program for the diameter and breaking position of the droplets obtained by breaking.Provide guidance and theoretical basis for subsequent further experimental research and industrialization.