Study On The Mineralization Mechanism Of Fine Coal Flotation And The Effect Of Reagents On Attachment Property

The interaction between particles and bubbles in flotation has received great attention and has been extensively studied.The research mainly focuses on two aspects:one is the theoretical description of particle trajectory,the other is the experimental monitoring of the interaction between particles and bubbles.However,most of the current research objects are glass beads and glass fibers with uniform shape and uniform surface properties.Little research has been done on fine coal particles and there is no mechanism study on the motion of particles in far field and near field.The research on attachment behavior between particles and bubbles mainly focuses on the determination of induction time and surface force.There is no systematic study on the influence of surfactants on the attachment properties between particles and bubbles.The raw coal from Gongwusu mining area was taken as the research object and the whole process of the relative motion between coal particles and bubbles is traced by the self-designed experiment device.Specific research contents are as follows:the variation of particle kinematics parameters in near field,the relationship between particles initial settlement position and collision angle,the influence of coal samples properties on collision angle and collision velocity,the variation of coal particles motion state during the sliding process on bubble surface,the relationship between attachment efficiency and coal samples' density and size,the effect of cationic surfactants and anionic surfactants on attachment properties.The conclusions obtained through these studies are as follows:(1)The main distribution interval of the particle equivalent diameter is 0.19-0.24 mm,0.10-0.15 mm and 0.07-0.11 mm.The distribution of particle equivalent diameter conforms to the Gaussian distribution,and the particle contour coefficient increases with the decrease of the coal sample size.(2)Particles are not affected by the bubbles in far field,and the trajectory of particles are always in vertical direction.The particles reach the terminal velocity after a short acceleration,and the time required for acceleration increases with the increase of coal particle density and size.The distribution of the terminal velocity of the nine coal samples conforms to the Gaussian distribution.(3)The distance between the trajectory deviation point and the center of the bubble increases as the initial settlement interval expands outward after the particles enter the near field.When the initial settlement interval is the same,the distance between the trajectory deviation point of the coarse coal sample and the center of the bubble is smaller than the distance between the trajectory deviation point of the fine coal sample and the center of the bubble.When the particle size is the same,the distance between the trajectory deviation point and the bubble center decreases with the increase of the density of coal sample in vertical direction.(4)When the particle velocity reduction reaches 10%,the distance to the bubble center decreases as the initial settlement interval expands outward after the particles enter the near field.When the initial settlement interval is the same,the distance decreases when the velocity reduction reaches 10%,which decreases with the increase of the particle size and density.The deviation angle of the particle velocity at the boundary of the resistance layer increases with the initial settlement interval.When the initial settlement interval is the same,the deviation angle of the particle velocity decreases with the increase of the particle size and density.(5)The distribution of coal particles in different collision angles is more in the middle particles and less in the two sides.The main distribution interval of the collision angle is 20°-50°,which expands outward with the initial settlement interval.The particle ratio shows two change rules:one is that the collision angle interval is continuously expanding outward,the other is that the particle concentration distribution interval is continuously expanding.The mean value of the collision angle of each interval increases as the initial settlement interval expands.(6)The coal particle collision velocity increases with the collision angle.When the collision angle is less than 50°,the collision velocity increases linearly with the collision angle.When the collision angle is greater than 50°,the collision velocity tends to plateau.When the collision angle is the same,the velocity reduction of low density particles is greater than the velocity reduction of high density particles.When the particles are far away from the bubble,the particle velocity,radial velocity and tangential velocity are relatively stable.The particle velocity and the radial velocity decrease rapidly as the distance between particles and bubbles decrease,the radial velocity decreases to almost zero,and the tangential velocity slowly rises.(7)The particle velocity at the bubble "equator" increases with the increase of the particle density,and the particle velocity reduction ratio decreases as the coal sample density increases.When the coal sample density is small,the ratio of particle velocity reduction at the bubble "equator" is not much different.When the coal sample density is large,the particle velocity reduction at the bubble "equator" is small.(8)The collision position of coal particles and bubbles will affect attachment,and the attachment efficiency decreases as the collision angle increases.The static water attachment angle decreases with the increase of the coal particle density and size when the collision angle is the same.When the coal sample density is small,the difference of static attachment angle between coarse and fine coal samples is not much different.When the coal sample density is large,the static water attachment angle of the fine coal sample is larger than the static water attachment angle of the coarse coal sample.(9)The static water attachment angle of coal samples decreases with the increase of SDS concentration,and increases first and then decreases with the increase of CTAB concentration.The difference of the static water attachment angle between the coarse coal sample and the fine coal sample decreases with the increase of the SDS concentration,and the influence of the bubble surface on the attachment is dominant.When the solution environment is CTAB,the increase of the static water attachment angle of the fine coal sample is greater than the increase of the static water attachment angle of the coarse coal sample.(10)SDS cannot adsorb on the surface of coal particles effectively,and adsorption of SDS on the surface of bubbles will reduce the attachment efficiency.CTAB will adsorb on the surface of coal particles under the action of electrostatic force to enhance the hydrophobicity of the surface of coal particles.When the amount of CTAB is too much,double-layer adsorption will be formed on the surface of coal particles to reduce the static water attachment angle of the coal sample.The adsorption of CTAB on the surface of the bubble reduces the hydrophobicity of the bubble surface and reduces the static water attachment angle of the coal sample.