| Comparing with common physical or chemical separating method, electrostatic separation is an effective physical separating method with incomparable characteristics. It is lower energy consuming, no pollution emission and especially proper for micro-fine particles processing. These advantages make it attractive in modern society in which the energy conservation and environmental protection are increasingly focused. With such advantages, electrostatic separation is getting more and more attention, and it will definitely leave profound influence on the separating field in the coming years.This thesis is concerning the research of micro-fine particles electrostatic separation. Based on the research of former micro-fine particles suspension electrostatic separation, the theory of micro-fine particles suspension separation is improved through further researches on separating theory. Avoiding several main factors of disturbing the results of suspension electrostatic separators, as a brand-new approach to micro-fine particles separating, Jet Electrostatic Separation is invented by the author. Based on the principle of Jet Electrostatic Separation, related basic experiments are designed. The outcomes of those experiments are satisfactory and they also make the industrial application possible.The thesis covers eight parts as follows:1. Research on basic theory.A series research on basic theory of micro-fine particles suspension electrostatic separation has been finished systematically, including the analysis on some basic principles. This research also explored the technology of electrostatic separation as well as its' application in micro-fine particles separation, and summarized the operation principle of suspension electrostatic separation. Experiments are done on the factors that effect micro-fine particles suspension electrostatic separation. Finally, some limitations, which are in the suspension electrostatic separator in existence, are concluded.2. For the first time, the research figured out some of the design defects of suspension electrostatic separator like the confliction of liquid status, and improved the design of suspension electrostatic separator.The experiments proved that there are some advantages in the original suspension electrostatic separator such as higher reliability and efficient outcomes of separating. The author of this thesis, through theoretical analysis and experimental research of suspension electrostatic separator, made corresponding improvement and achieved a better result, but failed to solve a large amount of original design deficiency. Therefore a new project of jet suspension electrostatic separator has been proposed.3. For the first time, the research on the characteristics of powder mass moving in high voltage electrostatic field has been done.The movement of powder mass in high voltage electrostatic field is a key factor affecting the results of separating. But this issue has not yet been studied in-depth research according to the information available at present. This paper describes the close observation and research on powder mass moving in high voltage electrostatic field. The author put forward the mechanism of powder mass moving in high voltage electrostatic field and made satisfactory explanation to these phenomena such as convection, circulation, jumpiness, ring arch and so on. This research provided a basic knowledge to take advantage of powder mass moving in high voltage electrostatic field and to avoid the disadvantage effectively during the separating process.4. For the first time, the theory of jet suspension electrostatic separation is proposedThe basic mechanism of Jet Electrostatic Separation is that the charging process and discharging process are separated into two independent stages so that they can be dealt with respectively. Suspended by the airflow, micro-fine particles are mixed with air to be the air-solid two phase flow. The air-solid two phase flow passes through a high voltage crown electrostatic field, by which the particles get fully charged. And then, under the force of both the airflow and the high voltage electrostatic field, the accelerated charged particles are ejected from a convergent nozzle and discharged immediately by impacting on a discharging board with glazed surface. Through adjusting the discharging process by controlling the airflow speed, the voltage of electrostatic field, and the obliquity of the discharge board, the conducting particles can discharge completely while non-conducting particles basically are not discharged. After this, all of those particles drop into separating electrostatic field and finish the separation process under the force of high voltage electrostatic field.5. For the first time, the author quantitatively calculated the contact time of discharge collision between rutile powder and discharge board.Under the effect of both flow field and electric field, the actual discharge time of conductive particles and nonconductive particles in rutile powder is modified, 0.07038μs for rutile particles while 0.06182μs for silicon particles. Therefore, in rutile powder, despite the differences between conductive particles and nonconductive particles such as mass, dielectric constant, quantity of charge and velocity of collision, the actual discharge contact time for each kind of particles are quite similar, and generally the discharge time of nonconductive particles is shorter than that of conductive particles. It is favorable to jet suspension electrostatic separation.6. For the first time, the mathematical model of jet suspension electrostatic separation is establishedThe particulate movement model in flow field can be established by the next equation.The formula indicates that jet suspension electrostatic separation is able to separate two kinds of particles by the different amount of remains electric charge after the collision.7. For the first time, each track of conductive particles or nonconductive particles in separating cabinet has been observed and verified by experiments.From the mathematical model of jet suspension electrostatic separation, many parameters of conductive particles and nonconductive particles in rutile powder can be quantitatively calculated, such as contact time of discharge collision, remanent quantity of charge, direction and velocity of entering separating cabinet, acceleration of gravity, electric field acceleration, as well as deceleration of air resistance. For the first time, the movement position and the trochoid of rutile powder are quantitatively calculated and visually showed by a chart. This is a powerful tool for the theoretical research and engineering application of micro-fine particles electrostatic separation in the future.8. Experimental verification on the theory of jet suspension electrostatic separation has been done.Through a lot of analysis, the experimental device was designed. From then, many experiments have been made based on different combinations of experimental parameters. In a separating experiment, the content of TiO2 was increased to 90.56% and the reclaim rate reached 80.12%. The result of the experiment indicated that the calculation from the mathematical model, which proves that the outcome of the experiment is reliable. In turn it shows that the design of the experiment device is successful.Based on a great number of theoretical analysis and experimental verification above, it can be proved that, jet suspension electrostatic separation is feasible and effective to take away nonconductive particles, such as quartz, from rutile powder with favorable conductivity.All in all, jet suspension electrostatic separation can increase the separating precision dramatically and improve the separating efficiency markedly. It is necessary to bring the experimental study into industrial production.
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