Research On The Influence Of Jet Crushing On The Physical Properties Of Powders And The Mechanism Of Crushing

With the development of industrial production and the improvement of materialrequirements,the air jet crushing technology has received more and more attention from people,and has become an extremely important process in the production process.Air jet crushing has the advantages of small particle size after crushing,which can reach the micron level,narrow particle size distribution,high purity,good dispersion,etc.,and is suitable for the crushing of low melting point materials.However,in the process of production and application,it often relies on empirical regulation and control,and there is still a problem of lack of relevant experimental results and theoretical guidance for the control of process parameters in the crushing process,resulting in lower production efficiency and increased production costs.At present,there are few studies on the pulverization mechanism of different materials in the fluidized bed jet crushing process,and the physical properties and product performance of the powder obtained after jet crushing are inseparable from its crushing mechanism.Therefore,research in this area should be strengthened.This dissertation explores the types,powder fluidity,and bulk density of Molerus powder by airflow crushing by crushing starch,straw,wolfberry,yeast and other materials with a jet fluidized bed jet mill.The effect of compressibility;the effect of crushing parameters such as gas pressure,material feed rate,classifier speed,etc.on the particle size distribution of different types of powder in the process of airflow crushing;the powder after airflow crushing under different working conditions The powder properties such as solubility,swelling degree,water holding capacity,fat binding capacity were measured,and the influence of different airflow crushing parameters on the powder properties was explored.Finally,this dissertation also combines the experimental research with the particle number calculation model.By calculating the experimental results under different operating conditions,the selection function and crushing function of different particle levels are obtained,and the The crushing mechanism and crushing rules were analyzed.The results of the study show that after jet milling,the types of Molerus powders of different powder materials change differently.Among them,yeast powder changed from Molerus ? powder to Molerus ? powder,and straw powder showed a tendency to change from Molerus ? powder to Molerus ? powder.The effect of jet crushing on the fluidity,bulk density and compressibility of different powders also showed corresponding specificity.The particle size obtained by air flow crushing decreases with the increase of the system inlet pressure.However,when the inlet pressure reaches a certain value,the particle size change curve gradually becomes gentle,and the influence of the gas pressure on the particle size after crushing becomes very small.At this time,further increase of the inlet pressure does not significantly improve the crushing effect.At the same time,with the increase of the speed of the classifier,the particle size of the particles obtained by the air flow crushing becomes smaller,and the particle size distribution becomes narrower.In addition,the physical properties of different powder materials after crushing,such as solubility,swelling degree,water holding capacity,fat binding capacity,etc.,were all improved compared with those before crushing,indicating that airflow crushing can effectively improve various properties of the powder.During airflow crushing,as the particle size of the powder increases,the absolute value of the Kapur function increases and the particle crushing rate increases.This is because large particles have many defects and cracks,and the energy required for crushing is small,so the crushing rate is fast.With the increase of intake pressure,the selection function of coarser particles first increases and then decreases,while the selection function of finer particles does not change much.As the feed volume increases,the selection function of the particles shows the law of increasing first and then decreasing.Through the analysis of the crushing function,it is concluded that the main crushing methods of the powder particles in the fluidized bed jet mill are shearing and collision.Specifically,for coarser particles,the main crushing method is shearing.The finer particles have less internal defects and cracks,and are more difficult to be crushed than the larger particles.Crushing requires more energy.Therefore,the finer particles are mainly crushed by collision.