Study On The Settlement Characteristics And Model Of Coal Slurry Containing Kaolinite

For a long time,coal slurry clarification has been the key of the production management in most coal preparation plant.Coal slurry difficult to settle has brought great difficulties and challenges to the normal production of coal preparation plant.In this paper,kaolinite was selected as the research object,because of its serious effect to coal slime sedimentation.Kaolinite with high purity and low ash coal were firstly prepared to be samples.Later the characteristics of surface feature,electrical properties and functional groups of these samples were determined through particle size analyzer,scanning electron microscopy,zeta potential analyzer,Fourier Transform Infrared Spectrometer etc.These microscopic properties can be used to explain the subsequent experimental phenomena.The macroscopic properties of coal slurry samples were determined by measuring the conductivity and pH value of different samples.The conductivity is approximately proportional to the dose,which can be used for the feedback of intelligent control system.The coal particles will lead to the increase of the pH value of the slime water,and the kaolinite particles in contrast,which can be used for the feedforcing.After the determination of changes in macroscopic and microscopic properties of coal slurry before and after adding CaCl₂,the variation model is established by the figures of Zeta potential,pH and the conductivity.Through the natural sedimentation test,it is believed that the high purity coal and the coal slurry with kaolinite in the deionized water were very difficult to settle.However,with the increase of water hardness,the settlement effect became better gradually but the remains of kaolinite have a serious impact on the effect of coal slurry,so the turbidity is pretty high.According to the flocculation and sedimentation test,coagulant CaCl₂ has a significant effect.The comprehensive influence on the sedimentation effect of the concentration of slurry,the kaolinite content,and the dosage of coagulant were studied by a three factors and four levels orthogonal experiments.According to the experimental results,the settlement models of the settling velocity and the supernatant turbidity were obtained,which can be used to predict settlement effect in the actual production.The model with macroscopic detectable index and integrated sedimentation index can be used to approximately predict the settlement effect of slime water under different indexes.The EDLVO theory analysis shows that adding CaCl₂ affects the electrostatic interaction energy around the particles.With the dosage increase,the total potential energy between particles decreases,which is conducive to the settlement of particles.The setting difficulty order in coal slurry containing kaolinite is: coal-coal,coalkaolinite,kaolinite-kaolinite.In addition to reducing the electrical properties of the particles,the adding of Ca²⁺ not only attenuates the repulsion between the particles,but also thins the hydration layers on the surface which facilitates the agglomeration of particles into tighter large particles.