JP4866206B2 - Method and apparatus for purifying silica particles and purified silica particles - Google Patents

Description

  The present invention relates to a purification method and a purification device for silica particles, which are raw material powder of silica glass, and purified silica particles.

  Silica particles are used as a raw material for plastic packaging fillers such as IC and LSI, or as a raw material powder for a quartz glass crucible for pulling up a silicon single crystal of a semiconductor material. If impurities are contained in these silica particles, the semiconductor product is adversely affected, so that purified silica particles with few impurities are required.

  As a method for purifying silica particles, for example, a method of dehydrating silica particles in a fluidized state by introducing a gas containing chlorine or a chlorine compound at a temperature of 1000 to 1500 ° C. is known. (Patent Document 1). In addition, quartz powder is continuously supplied to the rotary kiln and a mixed gas of hydrogen chloride and chlorine is introduced into the kiln to bring it into contact with the quartz powder. The alkali metal contained in the quartz powder is converted into chloride and volatilized. A removal method is known (Patent Document 2). Furthermore, a method for removing metal impurities by fluidizing silica particles with a chlorinated treatment gas is known (Patent Document 3).

  On the other hand, there is known an electrolytic purification method in which a quartz glass is purified by applying a DC high voltage to solid quartz glass to move an alkali metal or the like inside the glass to the cathode side (Patent Document 4). In addition, an example in which electrolytic purification is applied to a quartz glass crucible (Patent Document 5) is also known, and a high voltage is applied to the quartz powder to charge the adsorbed impurity particles and electrostatically sort the quartz powder. A purification method is also known (Patent Document 6).

  In the above-described conventional method for removing impurities by making silica particles fluidized with a refined gas, many use a chlorine-based gas as the refined gas, and an example using a gas added with hydrogen is also known. However, there is an advantage that hydrogen gas can be purified in a short time, but there is a risk that explosive reaction may occur, so that the gas concentration is strictly controlled and its handling is difficult. Further, in order to increase the reaction rate, the processing temperature is required to be about 1300 ° C. or higher.

On the other hand, the method using chlorine gas or hydrogen chloride gas as a purification gas also has a high effect of removing impurities, but it takes a long time for purification, and the purification temperature is 1250 ° C. for purification in a practical time. Unless the temperature is higher than that, high purification efficiency cannot be obtained, and there is a problem in productivity. The conventional electrolytic purification method also takes time.
Japanese Patent Laid-Open No. 06-40713 Japanese Patent Application Laid-Open No. 08-290911 Special Table 2002-544102 Japanese Patent Publication No. 07-14822 JP 2004-307222 A JP 2003-1119018 A

  The present invention solves the above-mentioned problems in the conventional purification method for silica particles, a treatment method and a purification apparatus excellent in purification effect capable of removing impurities with high ionicity in silica particles in a short time, and Purified silica particles are provided.

The present invention relates to a method and apparatus for purifying silica particles and purified silica particles having the following constitution.
(1) In a purification method in which silica particles are brought into a fluidized state and purified gas is brought into contact with the silica particles in a fluidized state at a high temperature to remove impurity components of the silica particles, the silica particles in a fluidized state are positioned in a magnetic field region. A method for purifying silica particles, wherein a voltage is applied to the silica particles by an electric field generated by the movement of the silica particles and the silica particles are brought into contact with the purified gas.
(2) The purification method according to the above (1), wherein the silica particles in a fluidized state are positioned in a magnetic field region of 10 gauss or more and contacted with a purification gas at a temperature of 1000 ° C. or more.
(3) The method for purifying silica particles according to the above (1) or (2), wherein the purification gas contains one or both of a halogen gas and a hydrogen halide gas.
(4) The method for purifying silica particles according to any one of (1) to (3) above, wherein the purification temperature is 1000 ° C. or higher and 1300 ° C. or lower.
(5) Fluidizing tank for fluidizing silica particles, reaction vessel for receiving fluidized silica particles, means for introducing purified gas into the fluidizing vessel or reaction vessel, the inside of the fluidizing vessel or the reaction vessel at 1000 ° C. to 1300 ° C. An apparatus for purifying silica particles, comprising means for heating, means for forming a magnetic field of 10 gauss or more in a fluidized tank or a reaction vessel.
(6) The fluid tank also serves as a reaction vessel, and the lower part of the vertical cylindrical fluid tank is partitioned by a floor plate having a large number of ventilation holes, silica particles are filled on the upper side of the floor plate, A purified gas introduction port is provided, and a gas exhaust port is provided in the upper part of the fluid tank. On the other hand, a heater is provided on the outer periphery of the fluid tank, and a magnetic field is provided outside the heater. Forming means is provided, the silica particles in the tank are made into a fluid state by the purified gas introduced from the lower part of the fluidized tank, and the fluidized tank is heated to 1000 ° C. to 1300 ° C. by the heater, and the magnetic field forming means (5) The silica particle purifier according to the above (5), which forms a magnetic field of 10 gauss or more.
(7) Purified silica particles, wherein impurity components are removed by the purification method according to any one of (1) to (4) above.

  In the purification method of the present invention, the silica particles in a fluidized state are positioned in a magnetic field region of 10 gauss or more at a temperature of 1000 ° C. or higher, so that a voltage is applied to the silica particles by an electric field generated by the movement of the silica particles. Since the ionic impurity component contained in the silica particles is attracted by the electric field and diffuses to the particle surface and easily reacts with the purified gas, a high purification effect can be obtained in a short time. This impurity component reacts with the purified gas and is removed from the system as a gaseous compound gas.

  Since the treatment method of the present invention can obtain a high purification effect at a temperature of 1000 ° C. to 1300 ° C. lower than the average treatment temperature of the conventional gas purification method, there is an advantage that the energy cost is low. In addition, if halogen gas is used as the purified gas, there is no risk of explosion and safe operation is possible.

Hereinafter, the present invention will be specifically described together with examples.
The purification method of the present invention is a purification method in which silica particles are made into a fluid state, and purified gas is brought into contact with the silica particles in a fluid state at a high temperature to remove impurity components of the silica particles. The method for purifying silica particles is characterized in that the silica particles are brought into contact with the purified gas in a state where a voltage is applied to the silica particles by an electric field generated by movement of the silica particles.

  The purification method of the present invention is preferably a purification method in which silica particles in a fluidized state are brought into contact, and the purified gas is brought into contact with the silica particles in a fluidized state at a high temperature to remove impurity components of the silica particles. This is a method for purifying silica particles that is placed in a magnetic field region of 10 gauss or more and is brought into contact with a purified gas at a temperature of 1000 ° C. or more.

  In the purification method of the present invention, the silica particles in a fluidized state are positioned in the magnetic field region. The flowing silica particles located in the magnetic field region generate an electric field according to Fleming's law when the particles move, and a voltage is applied to the silica particles, and the ionic impurity components inside the silica particles are attracted by the electric field. And diffuse to the particle surface. For this reason, it becomes easy to react with purified gas, and a high purification effect can be acquired in a short time.

  The silica particles in the magnetic field region are kept in a fluid state so that the silica particles can freely move in the magnetic field region. Note that the fluidized state is not limited to the one that causes convection, and it is sufficient that the silica particles can move freely. Therefore, in the present invention, the fluidized state includes the suspended state.

  The strength of the magnetic field is suitably 10 gauss or more. If the strength of the magnetic field is lower than this, the effect of promoting the diffusion of impurity components is low, and the purification effect is not sufficiently improved. Preferably, the strength of the magnetic field is 10 gauss or more and 150 gauss or less. A good purification effect can be obtained in this range.

  The reaction temperature at which the fluidized silica particles come into contact with the purified gas is preferably 1000 ° C. to 1300 ° C. When the reaction temperature is lower than 1000 ° C., the impurity component contained in the silica particles does not exhibit ionic behavior, and it is difficult to increase the diffusion rate to the particle surface. If the reaction temperature is higher than 1300 ° C., the cost increases due to the higher temperature. The purification method of the present invention can obtain an excellent purification effect at a temperature of around 1200 ° C.

  In order to diffuse and move the impurity component contained in the silica particles to the particle surface, it is necessary to place the silica particles in a fluidized state and place them in a magnetic field. In order to fluidize the silica particles and place them in the magnetic field, for example, the silica particles are filled in a fluid tank equipped with a magnetic field forming means, and the silica particles are fluidized by blowing air or an inert gas into the tank. What is necessary is just to form a magnetic field in a tank. Alternatively, a cyclone container provided with magnetic field forming means may be used, and silica particles may be blown into the container together with air or inert gas to form a magnetic field. A purified gas may be used to fluidize the silica particles.

  As the purified gas, a gas that reacts with an impurity component on the particle surface and gasifies is used. Specifically, for example, a halogen gas such as chlorine gas or a hydrogen halide gas such as hydrogen chloride gas can be used. By introducing purified gas into fluidized silica particles in a magnetic field or fluidizing silica particles with purified gas in a magnetic field, diffusion of impurity components contained in the silica particles is promoted and moved to the particle surface, Impurity components come into contact with the purified gas on the particle surface and react to become chloride gas and the like, and are removed.

  According to the purification method of the present invention, purified silica particles with significantly less impurity components can be obtained with a short purification. Among the impurity components, the alkaline impurity component has a strong degree of ionic behavior at a high temperature and has the highest purification effect. In particular, it has an excellent effect on removal of Li having high ionicity.

  To carry out the purification method of the present invention, for example, a fluidized tank for fluidizing silica particles, a reaction vessel for receiving fluidized silica particles, a means for introducing purified gas into a fluidized tank or a reaction vessel, a fluidized tank or A purification apparatus having means for heating the inside of the reaction vessel to 1000 ° C. to 1300 ° C., means for forming a magnetic field of 10 gauss or more in the fluidized tank or in the reaction vessel may be used.

  The apparatus for carrying out the present invention may be one in which the fluid tank also serves as a reaction vessel. For example, a vertical cylindrical fluid tank is used, the lower part of which is partitioned by a floor plate having a number of ventilation holes, silica particles are filled on the upper side of the floor plate, and an inlet for purified gas is provided on the lower side of the floor plate. A gas exhaust port is provided at the top of the tank. On the other hand, a heater is provided on the outer periphery of the fluid tank, and a magnetic field forming means is provided outside the heater. The silica particles in the tank are made into a fluid state by the purified gas introduced from the lower part of the fluid tank, and further the inside of the fluid tank is heated to 1000 ° C. to 1300 ° C. by the heater, and the magnetic field forming means 10 A magnetic field of Gauss or higher is formed, and the purified gas reacts with the impurity component of the silica particles to vaporize the impurity component. The gas produced by the reaction is withdrawn from the fluidized tank together with the unreacted purified gas.

  Prior to the introduction of the purified gas, the silica particles are introduced into the fluidized tank in advance through the purified gas inlet to fluidize the silica particles, and then the purified gas is introduced into the tank instead of the air, or the air At the same time, purified gas may be introduced into the tank.

For example, the treatment condition may be that the purified gas and the silica particles are brought into contact with each other at a purified gas concentration of 1% to 15% at a temperature of 1000 ° C. to 1300 ° C. for 60 minutes to 90 minutes.
A cyclonic container is used in place of the fluidized tank, the temperature in the container is set to 1000 ° C. to 1300 ° C., a magnetic field of 10 gauss or more is formed in the region including the inside of the container, and silica powder is mixed with air in the container. The silica particles are introduced into a fluidized state, and purified gas is blown into the silica particles to react with the impurity components of the silica particles. The gas produced by the reaction is withdrawn from the reaction vessel together with the unreacted purified gas.

  An example of an apparatus for carrying out the purification method of the present invention is shown in FIG. As shown in the figure, the refining device 10 has a vertical cylindrical flow tank 11 and a heater 12 surrounding the flow tank 11, and a pair of magnets 13 so as to surround the flow tank and the heater outside the heater 12. Is provided. The fluid tank 11 is formed of a quartz tube, and has a purified gas inlet at the bottom and an exhaust outlet at the top. Further, a floor plate 14 is provided inside the fluid tank 11, and the floor plate 14 is provided with a number of vent holes.

  The purified gas introduced from the bottom of the fluidized tank 11 flows toward the upper part of the fluidized tank 11 through the vent holes of the floor plate 14, makes the silica particles 15 deposited on the upper side of the floor plate 14 into a fluidized state, and the exhaust port at the upper part of the fluidized tank 11. Is discharged to the outside. On the other hand, the inside of the fluidized tank is heated to about 1200 ° C. by the heater 12, and a magnetic field of 10 gauss or more is formed in the tank by the magnet 13.

  The silica particles maintained in a fluidized state by the purified gas generate an electric field by moving the silica particles in a magnetic field of 10 gauss or more, and a voltage is applied to the silica particles, and ionic impurity components inside the silica particles, for example, Lithium ions and the like are attracted to the particle surface by this electric field, and react with contact with the purified gas at a high temperature of around 1200 ° C. to form chloride and gasify, and are removed from the silica particles.

20 kg of silica particles having an average particle size of 220 μm are put into a quartz reaction vessel having an inner diameter of φ250 mm, a fluidized bed is formed using air as a carrier gas, a magnetic field is formed in a fluidized region, and purified gas is introduced at a high temperature to introduce silica. The particles were purified (Example). In addition, it processed by introducing refined gas, without forming a magnetic field in a flow area | region (comparative example). These treatment effects are shown in comparison with Table 1. In the examples of the present invention, the alkali metal content is 0.15 ppm or less and partially 0.05 ppm or less within the treatment time of 1 hour. In particular, Li has been greatly removed. On the other hand, the alkali metal contents of the comparative examples are each 0.3 ppm or more, and in particular, Li is hardly removed.

The conceptual diagram which shows the refinement | purification apparatus of this invention

Explanation of symbols

10-purifier, 11-fluid tank, 12-heater, 13-magnet, 14-floor plate, 15-silica particles.

Claims (10)

In a purification method in which silica particles are put into a fluidized state and purified gas is brought into contact with the silica particles in a fluidized state at a high temperature to remove impurity components of the silica particles, the fluidized silica particles are positioned in a magnetic field region of 10 gauss or more. silica particles comprising the steps of contacting a purified gas containing salt hydrogen gas, by an electric field caused by the movement of the silica particles and a step of a state where a voltage is applied to the silica particles, comprising contacting a purified gas Te Purification method.   The purification method according to claim 1, wherein the silica particles in a fluidized state are brought into contact with a purified gas at a temperature of 1000 ° C. or higher. The purified gas is purification method of the silica particles according to claim 1 or 2 including both chlorine gas and salts of hydrogen gas.   The method for purifying silica particles according to claim 1, wherein the purification temperature is 1000 ° C. or higher and 1300 ° C. or lower.   The method for purifying silica particles according to claim 1, wherein the magnetic field region is a magnetic field generated by a magnet. Including the from 1% to 15% concentration is the sum of chlorine gas and the salt of hydrogen gas in the purified gas, and the purified gas is the chlorine gas 1% or more, the salts of the hydrogen gas to 0.2% The purification method of the silica particle in any one of Claims 1-5. Fluidization vessel to fluidize the silica particles, or the reaction vessel for receiving a fluidized silica particles, means for introducing a purified gas containing salt hydrogen gas to the fluidizing tank through the reactor, the flow tank or the reaction vessel 1000 ° C. ~ An apparatus for purifying silica particles, comprising means for heating to 1300 ° C., means for forming a magnetic field of 10 gauss or more in a fluidized tank or reaction vessel.   The fluid tank also serves as a reaction vessel. The lower part of the vertical cylindrical fluid tank is partitioned by a floor plate having a large number of vent holes, and silica particles are filled on the upper side of the floor plate, and purified gas is placed on the lower side of the floor plate. An inlet is provided, a gas exhaust port is provided at the top of the fluid tank, and a heater is provided on the outer periphery of the fluid tank, and a magnetic field forming means is provided outside the heater. The silica particles in the tank are made into a fluidized state by the purified gas introduced from the lower part of the fluidized tank, and further the interior of the fluidized tank is heated to 1000 ° C. to 1300 ° C. by the heater, and 10 gauss by the magnetic field forming means. The apparatus for purifying silica particles according to claim 5, which forms the above magnetic field.   The apparatus for purifying silica particles according to claim 8, wherein the magnetic field forming means is a magnet. Including the from 1% to 15% concentration is the sum of chlorine gas and the salt of hydrogen gas in the purified gas, and the purified gas is the chlorine gas 1% or more, the salts of the hydrogen gas to 0.2% The apparatus for purifying silica particles according to claim 8 or 9.

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