Coarse Particle Settling Properties Study Based On Particle Analysis

This paper is based on the difference of physical and chemical property between particle and settlement medium,according to the principles and technologies of sedimentation operation requirements.In order to study particle sedimentation properties and reveal the corresponding relation between particle settling velocity and particle properties and settlement medium properties,the methods such as particle force analysis,particle settling velocity calculation,particle free settling test,particle hindered settling test,X-ray diffractometer as well as the Qemscan minerals analysis are used.The main research results as follows:At first,by making force analysis on single particle we can know that when free settling the particle by forces:gravity,buoyancy,viscous resistance,pressure gradient force,false quality force,Basset force,Saffman force and Magnus force,and when hindered settling the particle force analysis will be more complex.For each force analysis and comparing with the viscous resistance we can get that:only at the beginning of the accelerated motion,Basset force is important;in mainstream fluid area Saffman force has no effect on particle sedimentation process;when the particle size is biggish and rotating vigorous Magnus force has influence on particle sedimentation process.The second,exploring single particle free settlement situation,results show t hat the methods for determination of particle size and particle shape irregularit y has a great influence on particle setting velocity.Respectively considering part icle irregularity and particle size conversion relation we can get that bauxite pa rticle free settling theory and empirical formula:u=0.71d2×10-6m·s-1(applicable tograin size 0um to 111um);u=0.71d2×10-6m·s-1(applicable to grain size 111 um to309um);u=7.23 d ×10-3m·s-1(applicable to grain size 111 um to 309um).The third,particle group settlement and flocculation settlementation experiment is carried out to explore the relationship between particle interference settling velocity and particle properties and work out the particle interference settling velocity formula:u=a·C0·Sk+b(k is related to grain size coefficient),particle flocculation settling velocity formula:u=a·C0·Sk+b(x for concentration or granularity,b is related to particle size).To explore the effect of medium p H value with different grain sizes on the subsidence.Finally,by comparing the mineral particles with floccules particles sedimentation test find that particle structure morphology has an effect on particle sedimentation velocity and compression speed.Due to structure differences,with the same volume of mineral particle settling vclocity is greater than floccules particles;compared with mineral grains,floccules will adsorb a large number of moisture after particle sedimentation,and cause compression settling velocity is slow,accord with Roberts relation rule.