KR20120103174A - Acid leaching system for silicon powder - Google Patents

Abstract

PURPOSE: An acid leaching system for silicon powder is provided to prevent the occurrence of environmental pollution by condensing waste gas and collecting the condensed waste gas in a stirring bath. CONSTITUTION: An acid leaching system for silicon powder includes an acid leaching part(100), a silicon powder collecting part(200), a waste gas condensing part(300), and a waste gas purifying and discharging part(400). Silicon powder, distilled water, and acid at the pre-determined weight ratio are introduced into a stirring bath by a quantitatively introducing unit. The internal temperature of the stirring bath is raised by a heating unit, and the raised temperature of the stirring bath is maintained. The mixture of the silicon powder, the distilled water, and the acid is stirred in the stirring bath. Impurities in the silicon powder are leached in the acid leaching part. The mixture is separated into the silicon powder and waste liquid by a centrifuge(25) in the silicon powder collecting part. The waste gas condensing part receives and condenses the waste gas and returns the condensed waste gas to the acid leaching part.

Description

Acid leaching system for silicon powder {ACID LEACHING SYSTEM FOR SILICON POWDER}

The present invention relates to an acid leaching system, and more particularly, impurities such as solvent metal remaining on the surface from primary silicon crystals (hereinafter referred to as silicon powders) which are melted together with a source metal and then dissolved by cooling. The present invention relates to an acid leaching system for silicon powders, wherein the primary silicon crystals are leached.

Acid leaching is known as a method of obtaining purified silicon from silicon crystals containing impurities. To obtain silicon crystals purified by acid leaching, source silicon (a mixture or compound containing a certain amount of silicon) and a solvent metal (e.g., aluminum, which is a low melting point metal) are heated together to form a melt, and the melt is After forming primary silicon crystals while cooling, molten metal is removed to obtain primary silicon crystals (silicon powder), and acid leaching of the molten metal on the surface of the primary silicon crystals (silicon powder) by hydrochloric acid, nitric acid, hydrofluoric acid, etc. Purify by

In particular, when the silicon powder is purified by acid leaching, acid, distilled water and silicon powder should be treated at a predetermined ratio and maintained at a constant temperature during acid leaching. In addition, the purification of the silicon powder by acid leaching involves the generation of waste liquid and waste gas, which are harmful to the human body. At this time, the waste liquid and the waste gas are harmful to the environment, so the waste liquid must be separated and discharged, and the waste gas must be released after diluting the harmful components. For this reason, in the acid leaching method, it is difficult to mass-purify a silicon powder in a rapid process.

The present invention has been made to solve the above-mentioned problems with the acid leaching method of the conventional silicon powder tablet, and the first problem to be solved by the present invention is to prepare a mixture of silicon powder, acid and distilled water in a continuous process in a single system. By stirring while maintaining a constant temperature, the leaching of impurities is carried out, and the acid leaching system which not only separates the purified silicon crystals from the mixture from which the impurities are leached, but also minimizes and purifies the amount of waste gas generated in the stirring process to reduce environmental hazards. To provide.

The second problem to be solved by the present invention is to provide an acid leaching system that can rapidly purify the silicon powder in a rapid process by quickly measuring and quantitating the amount of silicon powder, acid and distilled water to be added to the stirring tank. .

The third problem to be solved by the present invention is to provide an acid leaching system that can not only quickly raise the temperature inside the stirring tank to the temperature required for acid leaching, but also continuously maintains the proper temperature required for acid leaching during the stirring process. .

The fourth problem to be solved by the present invention is to provide an acid leaching system that can effectively condense the waste gas generated in the stirring process and recover it into the stirring tank.

The first problem of the present invention described above is that after the acid leaching system adds silicon powder, distilled water and acid to a stirring tank by a fixed weight input device by a fixed weight ratio, the internal temperature of the stirring tank is raised to a constant temperature by a heating device. An acid leaching unit for stirring the mixture of silicon powder, distilled water and acid with the stirring device in the stirring tank to leach impurities remaining in the silicon powder; A silicon powder recovery unit which receives the mixture leaching impurities from the acid leaching unit by a pump installed in a pipe and a pipe, and separates the mixture into silicon powder and waste liquid by a centrifugal separator to recover silicon powder; A waste gas condensing unit which receives the waste gas generated in the stirring process from the acid leaching unit and condenses it, and then returns to the acid leaching unit; And a waste gas purification discharge unit which receives waste gas that has not been condensed in the waste gas condensation unit, cleans it with water, and discharges it to the atmosphere.

The second object of the present invention described above is a load cell capable of measuring the mass thereof when the silicon powder, distilled water and acid are added to the stirring tank by providing the metering unit at the bottom of the stirring tank, and the mass measured by the load cell. Distilled water inlet means for injecting distilled water of a predetermined mass into the agitation tank, an acid injecting means for injecting a predetermined mass of acid into the agitation tank based on the mass measured in the load cell, and a mass measured in the load cell. It is achieved by constructing silicon powder injecting means which injects a predetermined mass of silicon powder into the stirring vessel on the basis.

The third object of the present invention described above is an oil jacket in which the heating device surrounds the outside of the stirring vessel and is filled with a heat medium oil therein, an oil provided outside the stirring vessel and circulating the oil jacket inside the stirring vessel; An oil tank accommodating the first electrothermal heater for heating the oil, a pipe for forming a flow path for the oil to circulate between the oil jacket and the oil tank, and an oil installed between the oil jacket and the oil tank. It is achieved by including an indirect heating device composed of a pump to circulate, and a direct heating device for directly heating the mixture by a second heat transfer heater provided in the stirring vessel.

The fourth object of the present invention described above, the waste gas condensation unit, the condensation tube is connected to the upper portion of the stirring tank and the waste gas generated in the stirring tank in the stirring process passes, and the cooling water is enclosed inside the condensation tube A coolant tank, a coolant tank provided separately from the coolant jacket and having a coolant to circulate the coolant jacket and an evaporation coil of a refrigerating cycle to generate coolant, and a coolant circulated between the coolant jacket and the coolant tank. It is achieved by constructing a pipe so as to form a flow path and a pump provided in the pipe to circulate the cooling water between the cooling water jacket and the cooling water tank.

According to the present invention having the above-described configuration, the acid leaching method used as one of the silicon powder refining methods can be effectively applied to mass production of purified silicon in a state in which environmental hazards are minimized. That is, according to the present invention, the processes such as acid leaching, silicon powder recovery, waste gas removal, etc. are performed in a single process in a single system, and the amount of silicon powder, acid and distilled water to be added to the stirring tank is quickly measured and quantified. It can be added, and the temperature of these mixtures added to the stirring tank can be rapidly increased and stirred while maintaining at a constant temperature, so that the silicon powder can be purified in large quantities in a rapid process, and the waste gas generated during the stirring process can be condensed into the stirring tank. Since the recovery, the acid leaching method is used to minimize the environmental hazards.

1 is a block diagram of an acid leaching system for silicon powder according to the present invention.
Figure 2 is a detailed view of the acid leaching part of the acid leaching system for silicon powder according to the present invention.
Figure 3 is a detailed view of the silicon powder recovery portion of the acid leaching system for silicon powder according to the present invention.
Figure 4 is a detailed view of the waste gas condensation unit of the acid leaching system for silicon powder according to the present invention.
Figure 5 is a detailed view of the waste gas purifying exhaust portion of the acid leaching system for silicon powder according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the acid leaching system according to the present invention includes an acid leaching unit 100 for removing and purifying impurities of unrefined silicon (silicone powder) by an acid leaching method and impurities by an acid leaching method. Silicon powder recovery unit 200 for centrifuging the removed silicon powder, waste gas condensation unit 300 for minimizing waste gas emissions by condensing most of the waste gas into the agitation tank, and harmful substances remaining in the waste gas in water The waste gas purification discharge unit 400 that absorbs and purifies waste gas discharged to the atmosphere is configured as a single integrated system. Although not shown in the drawings, the acid leaching system according to the present invention is a well-known programmable logic controller (PLC) for controlling the components (valve, valve, pump, electric heater, motor, compressor, etc. described later) of these parts as described below. And a microprogram employing a controller or microprocessor and a peripheral employing controller, and a control program executed on the controller.

As can be seen with reference to Figures 1 and 2, the acid leaching unit 100 is after the silicon powder, distilled water and acid in a fixed weight ratio by the input device in a fixed weight ratio by a metering unit, and then by a heating device While maintaining the internal temperature of the stirring tank 7 to a constant temperature, a mixture of silicon powder, distilled water and acid is stirred in the stirring tank 7 with a stirring device to leach impurities remaining in the silicon powder.

The dosing device includes a load cell 19 provided at the lower end of the stirring tank 7 to measure the mass thereof when silicon powder, distilled water and acid are added to the stirring tank 7. In addition, the metering unit is a distilled water injecting means for injecting distilled water of a predetermined mass into the stirring vessel 7 based on the mass measured in the load cell 19, and based on the mass measured in the load cell 19 Acid injecting means for injecting a predetermined mass of acid into the stirring vessel 7, and silicon injecting silicon powder of a predetermined mass into the stirring vessel 7 based on the mass measured by the load cell 19. Powder input means.

The distilled water inlet means is a distilled water tank (1) connected to the upper inlet (9b) of the stirring vessel (7) and the pipe (L1), the pump (P1), flow meter (M) and valve provided in the pipe (L1) It may be configured as (V1). The distilled water tank 1 may further include a hopper 3 for distilled water input, a pipe L19 for distilled water drain, and a valve V9. When distilled water is input, the controller receives the mass measured by the load cell 19, and based on this, the valve V1 is opened and the pump P1 is operated to draw distilled water having a predetermined mass into the stirring tank ( To 7).

The acid injecting means includes acid tanks 5a and 5b connected to the upper inlet 9a of the stirring vessel 7 by a pipe L2, a pump P2 provided in the pipe L2, and a flow meter M. And a valve V2. As shown in the figure, the acid tanks 5a and 5b may be two or more. 1 and 2 exemplarily show hydrofluoric acid tank 5a and nitric acid tank 5b. As needed, you may add another type of acid tank, such as a hydrochloric acid tank. At this time, it is possible to further provide the cock (C1, C2) to open and close manually in the branch pipe connected to each tank (5a, 5b) shown in FIG. When using an acid leaching system, the cokes C1 and C2 are opened and locked otherwise. When the acid is added, the controller receives the mass measured by the load cell 19, and based on this, the valve V2 is opened and the pump P2 is operated to generate acid of a predetermined mass into the stirring tank ( To 7).

The silicon powder inlet means may be composed of a silicon powder inlet tube 11 connected to the upper inlet 9c of the stirring vessel 7 and a valve V3 provided in the silicon powder inlet tube 11. A well-known hopper may be further provided on the silicon powder inlet tube 11. When the silicon powder is added, the controller receives the mass measured by the load cell 19, and opens the valve V3 to inject the silicon powder having a predetermined mass into the stirring vessel 7 based on this.

In this way, the acid leaching system according to the present invention, by rapidly measuring the amount of silicon powder, acid, and distilled water to be added to the stirring tank and quantitatively input, it is possible to mass-purify the silicon powder in a fast process.

As shown in FIG. 2, the stirring device is installed outside the stirring tank 7 and the rotating shaft is installed on the motor 15 extending to the inside of the stirring tank 7 and the rotating shaft of the motor 15. It includes a fan 17 for stirring the mixture introduced into the stirring tank 7 by the rotation of the motor (15).

As can be seen with reference to FIGS. 1 and 2, the stirring vessel heating apparatus according to the present invention includes an indirect heating apparatus and a direct heating apparatus. The indirect heating device surrounds the outside of the stirring tank 7 and has an oil jacket 24 enclosed therein for heating the heat medium, and is provided outside the stirring tank 7 and circulates the oil jacket 24 therein. An oil tank 23 accommodating oil and the first heat transfer heater 21 for heating the oil, and a pipe for forming a flow path for allowing oil to circulate between the oil jacket 24 and the oil tank 23 (L16). L17 and a pump P6 installed in the pipe to circulate oil between the oil jacket 24 and the oil tank 23. The direct heating device is composed of a second heat transfer heater 22 provided in the stirring vessel (7). The direct heating apparatus directly heats the mixture introduced into the stirring vessel 7 to quickly raise the temperature of the mixture to an acid leaching proper temperature (eg, 80 ° C.), and the indirect heating apparatus has a large area from outside the stirring vessel 7. The amount of heat in the agitation vessel 7 at the same time is applied throughout so that the temperature of each part of the mixture can be maintained at a uniform level during stirring. The stirring tank 7 and the oil tank 23 are provided with temperature sensors S1 and S2, and the controller receives the values of the temperature sensors and the temperature of the stirring tank 7 and the oil tank 23. The first heat transfer heater 21 and the second heat transfer heater 22 are controlled to maintain a predetermined temperature.

When impurities are leached out by stirring in the acid leaching unit 100, the mixture is transferred to the silicon powder recovery unit 200 through an outlet 13 provided at the bottom of the stirring tank 7. The silicon powder recovery part 200 receives the mixture in which impurities are leached from the acid leaching part 100 by a pump P7 installed in the pipe L5 and the pipe L5, and then mixes the mixture by the centrifuge 25. This is separated into silicon powder and waste liquid to recover the silicon powder. As shown in FIG. 3, the centrifuge 25 includes a rotary cylinder 31 in which the mixture is introduced and centrifuged, an input tube 32 for injecting the mixture transferred to the rotary cylinder 31, and the A motor 27 for driving the rotating cylinder 31, a discharge pipe 33 for separating and discharging waste liquid during the rotation of the rotating cylinder 31, and a housing 29 accommodating the rotating cylinder 31 therein. Can be configured. Outside the housing 29, the first waste container 35 for receiving and temporarily storing the waste liquid separated from the rotary cylinder 31 or overflowed into the housing 29, and the capacity than the first waste container 35 The large second waste container 37 may be further provided. As shown in FIG. 3, the second waste container 37 may also be connected to the bottom outlet 13 of the stirring vessel 7 by a pipe L3, and the second waste container 37 may be connected to a pipe adjacent to the second waste container 37. A pump P8 for transferring waste liquid or agitating vessel washing liquid, etc., from the first waste liquid container 35 or the stirring vessel 7 to the second waste liquid container 37 may be provided.

1 and 4, the waste gas condensation unit 300 is connected to the upper portion of the stirring vessel (7) and the condensation tube (39) through which the waste gas generated in the stirring vessel (7) in the stirring process and A coolant jacket 41 surrounding the outside of the condensation tube 39 and having a coolant sealed therein, and a coolant and a coolant to circulate the coolant jacket 41 inside the coolant jacket 41 are provided outside the coolant jacket 41. A cooling water tank 43 containing the evaporating coil 49 of the refrigerating cycle to be generated, pipes L7 and L8 forming a flow path for cooling water to circulate between the cooling water jacket 41 and the cooling water tank 43; And a pump (P4) installed in the pipe to circulate the cooling water between the cooling water jacket 41 and the cooling water tank 43, and condenses the waste gas generated in the stirring process in the acid leaching unit 100 by inflow. After returning to the acid leaching unit 100, waste gas Thereby significantly reducing emissions. As shown in FIG. 4, the inner surface of the condensation tube 39 may be formed as a curved surface in which optical narrow diameters are repeated, so that the contact area with the cooling water is maximized. The refrigeration cycle includes a compressor (45) for compressing the gas refrigerant at high temperature and high pressure, a condenser (47) which takes heat from the compressed high temperature and high pressure gas refrigerant and changes it into a high pressure liquid refrigerant, and a high pressure of the phase change in the condenser. It is composed of an expansion valve (EX) for expanding the volume in a good state to vaporize the liquid refrigerant and the evaporation coil (49) which is installed inside the cooling water tank (43) to take the heat amount of the cooling water and change the liquid refrigerant into a gas refrigerant. . The coolant tank 43 is equipped with a temperature sensor S3, and the controller operates the compressor 45 according to the input value of the temperature sensor S3 to maintain the coolant temperature in the coolant tank 43 at a predetermined temperature. do.

1 and 5, the waste gas purification discharge unit 400 receives waste gas that has not been condensed in the waste gas condensation unit 300, cleans it with water, and discharges it to the atmosphere. To this end, the waste gas purification discharge unit 400 is provided with a purification tank 51 for receiving waste gas from the condensation tube 39 to purify the supply water, and provided in the lower portion of the purification tank 51 to overflow from the purification tank 51. It includes a reservoir 53 for temporarily storing the overflowed purified water. The upper part of the purification tank 51 receives the waste gas from the condensation tube 39 and at the same time receives the feed water from the external water tank, mixes the mixture 55 to be introduced into the purification tank 51, and does not mix with water. 51) nozzles 57a and 57b for injecting water into the waste gas introduced therein, and an exhaust port 59 for discharging waste gas from which the harmful components have been washed with water from the mixer 55 and the nozzles 57a and 57b to the outside. Prepared. Perforated diaphragms 67 and 69 may be installed in the purification tank 51 to distinguish the lower space of the mixer 55, the lower space of the nozzles 57a and 57b, and the lower space of the exhaust port 59. Holes are formed in the perforated diaphragm to allow liquid and gas to pass through. Between the purifying tank 51 and the reservoir 53 is sealed by a sealing diaphragm 65, the sealing diaphragm 65 through the sealing diaphragm 65 to go through the upper and lower predetermined lengths of the overflow pipe ( 63) may be provided to automatically flow into the reservoir 53 when the purified water in the purification tank 51 rises above a predetermined height. The reservoir 53 may also be provided with a curved overflow tube 61 so that the water level in the reservoir 53 rises above a predetermined level to be drained to the outside through the drain pipe L15. A circulation pipe L12 and a pump P5 may be installed between the bottom of the reservoir 53 and the nozzles 57a and 57b of the clarifier 51 to reuse when the concentration of the purified water in the authentic cylinder 53 is low. It is desirable to have.

In this way, the acid leaching system according to the present invention, while maintaining a constant temperature of the mixture of silicon powder, acid and distilled water in a single system while stirring to leach the impurities, purified silicon crystals from the mixture from which impurities are leached It not only separates the wastes, but also minimizes and purifies the amount of waste gas generated in the stirring process to reduce environmental hazards.

1: distilled water tank 3: hopper
5a, 5b: acid tank 7: stirring tank
9a, 9b, 9c: inlet hole 11: silicon inlet tube
13: outlet 15: motor
17: fan 19: load cell
21: first electric heater 22: second electric heater
23: oil tank 24: oil jacket
25 centrifuge 27 motor
29 housing 31 rotation cylinder
32: input pipe 33: discharge pipe
35: first waste container 37: second waste container
39: condensation tube 41: coolant jacket
43: coolant tank 45: compressor
47: condenser 49: evaporation coil
51: Purification Container 53: Reservoir
55 mixer 57a, 57b nozzle
59: exhaust port 61: curved overflow tube
63: straight overflow pipe 65: sealed diaphragm
67, 69: perforated diaphragm

Claims (4)

The silicon powder, the distilled water and the acid are introduced into the stirring tank 7 at a predetermined weight ratio by the metering device, and then the silicon is mixed with the stirring device while the temperature inside the stirring tank 7 is maintained at a constant temperature by the heating device. An acid leaching unit (100) for stirring a mixture of powder, distilled water and acid in the stirring tank (7) to leach impurities remaining in the silicon powder;
The mixture in which impurities are leached from the acid leaching unit 100 is transferred by the pipe L5 and the pump P7 installed in the pipe L5, and the mixture is separated into silicon powder and waste liquid by a centrifuge 25. A silicon powder recovery unit 200 for recovering silicon powder;
A waste gas condensing unit 300 which receives the waste gas generated in the stirring process from the acid leaching unit 100 and condenses it and then returns to the acid leaching unit 100; And
Acid waste leaching system for a silicon powder, characterized in that it comprises a ;; waste gas condensation unit 300, the waste gas that is not condensed in the waste gas inlet is washed with water to purify and discharged to the atmosphere after discharged to the atmosphere.
The method of claim 1,
The metered dose device,
Based on the load cell 19 and the mass measured by the load cell 19 is provided at the lower end of the stirring tank (7) to measure the mass when silicon powder, distilled water and acid are added to the stirring tank (7) Distilled water injecting means for injecting distilled water of a predetermined mass into the stirring vessel 7 and acid injecting means for injecting a predetermined mass of acid into the agitating vessel based on the mass measured by the load cell 19. And a silicon powder injecting means for injecting a silicon powder having a predetermined mass into the stirring vessel (7) based on the mass measured by the load cell (19).
The method of claim 1,
The heating device,
An oil jacket 24 surrounding the outside of the stirring tank 7 and filled with a heat medium oil therein, and an oil and the oil to be circulated inside the stirring tank 7 and circulating the oil jacket 24 inside the stirring tank 7. An oil tank 23 accommodating the first heat transfer heater 21 to be heated, pipes L16 and L17 for forming a flow path for the oil to circulate between the oil jacket 24 and the oil tank 23, and An indirect heating device installed in the pipe and configured to include a pump P6 for circulating oil between the oil jacket 24 and the oil tank 23, and a second heat transfer heater 22 provided in the stirring vessel 7. Acid leaching system for a silicon powder, characterized in that it comprises a direct heating device for directly heating the mixture.
The method of claim 1,
The waste gas condensation unit,
A condensation tube 39 connected to an upper portion of the stirring vessel 7, through which waste gas generated in the stirring vessel 7 passes, and a coolant jacket enclosed outside the condensation tube 39 and filled with coolant therein. (41), and a coolant tank (43) provided outside the coolant jacket (41) and containing an evaporation coil (49) of a refrigerating cycle for generating coolant for circulating the coolant jacket (41) and for generating coolant therein; And pipes L7 and L8 for forming a flow path between the coolant jacket 41 and the coolant tank 43 so that the coolant can circulate, and the coolant jacket 41 and the coolant tank installed in the pipe. 43) Acid leaching system for silicon powder, characterized in that consisting of a pump (P4) to circulate between.

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