Main Factors Affecting The Clarification Of Coal Slurry And Their Mechanism

Coal slurry treatment is a crucial link in the coal preparation plant.The process is complicated and has many influencing factors,which brings difficulties to the production automation control program.Therefore,this paper investigates the seven factors affecting the sediment concentration and clarification of coal slurry,clay minerals,clay mineral content,ion species,ion dosage,flocculant type and flocculant dosage,and evaluates their effects through orthogonal test.The main factors were selected,and then the influence of main factors on the clarification of coal slurry were analyzed,to provide a basis for the automatic control of coal slurry process.At the same time,real-time online particle observation system is used to observe the dynamic process of coal slurry flocculation to give the mechanism of influence of main factors on coal slurry.The coal particle size and specific surface area characteristics were determined by laser particle size analyzer and specific surface area analyzer,respectively.The particle size and specific surface area characteristics of the sample were thus determined.A jar test was conducted to determine the dosage of the agent.Based on this,a seven-factor and three-level orthogonal test was designed.The visual analysis and variance analysis were carried out to determine the primary and secondary order of the influencing factors.The significant degree of these factors could be order as coagulant dosage,flocculants type,kaolinite content and the flocculant dosage.Then,single factor experiments were conducted to explore the effects of these factors the clarification of coal slurry.The experimental results show that with the increase of the amount of cationic coagulant,the potential value of the coal slurry system gradually increases.When the dosage is 100mg/L,the potential value is closest to the zero point.The surface potential of the slime particles turns positive when increasing the dosage furtherly.Due to the electrostatic force,the size and compactness of the formed flocs rose at first and then descended.Correspondingly,the supernatant turbidity of the coal slurry first decreases and then increases,and the sedimentation velocity first increases and then decreases.Among the different types of flocculants,the supernatant with the anionic flocculant PHP had the lowest turbidity and the fastest sedimentation rate.And the potential in the coal slurry system was closest to the zero point.Within experimental range,as the amount of PHP increased,the size and tightness of the formed flocs gradually increased,and the turbidity of the supernatant and the potential of the coal slurry system decreased,and the sedimentation speed became faster.The results show that the ionic characteristics of the flocculant had a significant effect on the charge neutralization and contributed maximally the most to the turbidity of the supernatant after flocculation and sedimentation.The molecular weight of the flocculant has a significant effect on the size and sedimentation velocity of the flocs,indicating a large molecular weight could improve settlement efficiency by facilitating the growth of the flocs and accelerating the sedimentation.The increase of kaolinite content gradually increased the turbidity of the supernatant and reduced the sedimentation velocity,the potential of the coal slurry and the size and tightness of the formed flocs.Within the investigation range,the lowest potential value and the fastest sedimentation rate was observed when the kaolinite content is 30%.The Particle Vision Measurement(PVM)test results of the flocculation process show that the needed flocculation time is positively correlated with the maximum floc size may grow up to,and the agent and fluid environment together determine the size of the floc that can grow.