KR101188313B1 - Recycling Method for Waste Sludge Formed by Solar Cell Wafer Manufacturing and Recycling System Thereof - Google Patents

Abstract

The present invention relates to a waste sludge recycling method and a recycling system generated during the manufacture of a wafer for a solar cell. The present invention relates to a waste sludge recycling method and a recycling system capable of minimizing waste generation by effectively separating metal impurities and fine particles in a coolant, which is cutting oil, to increase recycling efficiency.
According to the present invention, the amount of waste slurry generated by minimizing the investment and maintenance costs incurred during the recovery of coolant, and separating the metal impurities and fine particles in the coolant more effectively, thereby increasing the coolant recycling cost and efficiency. And the processing cost can be reduced to lower the manufacturing cost of the wafer for solar cells.

Description

Recycling Method for Waste Sludge Formed by Solar Cell Wafer Manufacturing and Recycling System Thereof}

The present invention relates to a waste sludge recycling method and a recycling system generated during the manufacture of a wafer for a solar cell, and more particularly, to an agglomeration reaction step in the middle of a stepwise centrifugation step in a waste sludge recycling process during a solar cell wafer process. The present invention relates to a waste sludge recycling method and a recycling system that can minimize waste generation by effectively separating fine particles in coolant, which is cutting oil, thereby increasing regeneration efficiency.

The slurry refers to waste materials such as abrasives and cutting oils generated during silicon wafer cutting in the semiconductor manufacturing process.

Ingot manufacturing of sludge regenerated semiconductor and solar cell wafers is mostly made by wire sawing, and it improves cutting efficiency by supplying slurry mixed with cutting oil and cutting agent to the cutting part. To control the heat. In this process, it is generated as saw dust of silicon corresponding to 20 to 30wt% of the silicon ingot. These coolants, cutting agents and cutting powders are removed from the wafer through the cleaning process, and the waste sludge generated is a cutting agent, cutting powders and other foreign substances (metallic components such as coolant additives and iron powders). It is dispersed in cutting oil.

The waste sludge produced at this time cannot be simply incinerated, and because it is classified as special industrial waste, a simple landfill causes severe soil contamination. This method of treatment requires the import of expensive cutting agents and cutting oil, The additional cost of special industrial waste is required, which increases the manufacturing cost of the wafer and causes serious environmental pollution.

In addition, semiconductor manufacturers have been collecting and discharging the discharged slurry through a waste collector. Relying on 100% imports from Japan, the material pays enormous amounts annually and enters the country, but has been discarded after being used once, causing environmental pollution.

Therefore, there is a need for a method for recovering cutting oil, cutting agent, cutting powder and the like contained in the waste slurry, and the related art development has been continued.

However, the prior art in such a waste slurry recycling method is not very high recovery rate, and is not suitable as a recycling method of waste slurry for wafer manufacture with a relatively high viscosity.

And when the dilution using cutting oil or solvent to reduce the viscosity of the waste slurry, there is a problem that the amount of cutting oil to be recovered is increased, or a separate distillation apparatus for recovering the used solvent is required.

The method of lowering the viscosity by heating has no problem as described above, but also has a problem that separation of the cutting powder using only centrifugation is not easy.

European Patent No. 0767035 Instead of centrifugation and decanter used in waste slurry separation, it is possible to separate the used slurry into cutting oil and cutting material containing small particles by using microsieve and ultrasonic wave. A microsieve process model is disclosed. However, if the micro sieve is blocked, the replacement cost and maintenance cost can be continuously maintained. If the micro sieve is blocked, the manufacturing cost is more than twice that of the existing one, and if the throughput is increased in terms of efficiency, the cross-sectional area must be increased. There is a problem.

US Patent No. 7,223,344 In the case of selectively removing the fine powder Si and Fe from solids, acid solution (1 ~ 10wt% HCl) is used to remove iron, and basic solution (2 ~ 30wt%, NaOH) is used to remove Si fine powder. A method is disclosed. However, in the case of the chemical treatment method, the heat of reaction and post-reaction gas are generated, and the cleaning and neutralization step are required, and in the case of the method, the process volume of the step requiring the chemical cleaning method can be reduced to a minimum due to the increase of the process step. There is a problem that needs to be reduced.

Korea registered patent No. 626,252 Separating the waste wire saw slurry into a solid component and a liquid component; Introducing and washing a water-soluble component and a solvent for removing organic matters in the separated wire sawing slurry; Settling the cleaned slurry for wire sawing to separate the layers and recovering the abrasive; Filtering the recovered abrasive; Drying the filtered abrasive; Disclosed is a method of reclaiming a wire sawing abrasive comprising the steps of classifying the dried abrasive and removing the iron component from the classified abrasive. However, the process time is long because the process must be left for 2 ~ 3 hours after stirring during the washing step, and the increase of the processing liquid due to the repeatability of the work increases the process cost, and the use of organic solvents. There is a problem.

Korean Patent No. 652,822 After cutting the cutting oil and the cutting material by 1-dimensional core separation, the large particles of the cutting oil are separated once more by the secondary centrifugation, and the secondary centrifuged secondary oil is filtered / purified by the regeneration filter to reduce the regeneration oil. Disclosed is a method for regenerating waste slurries, which produces recycle slurries using a small amount of the third centrifuged abrasive. However, when the regeneration filter is used for the filtration / refining of the secondary oil, the removal of fine particles reduces the process efficiency, and the cartridge filter requires a lot of cost to replace and maintain the cartridge filter, and to remove the iron in the slurry. The use of filters gradually has the problem that iron will require significant equipment and cost to block, remove and operate magnetic filters.

In Korean Patent No. 385,177, before introducing waste sludge into a decanter, it is diluted and mixed with a coolant at a ratio and separated by a decanter to separate the sawdust and shredding cutting materials. In order to adjust the viscosity of the liquid phase by heating by heating the temperature heating device at the time of mixing supply, the filtrate from the primary decanter is recovered by the coolant by the secondary decanter Disclosed is a method for regenerating waste cutting fluid for cutting wire saws, wherein the recovered coolant is always pressurized to allow the extrusion and supply of extrusion during cleaning and mixing with the waste sludge. But, Dilution increases throughput, leading to higher processing costs, and dilution favors SiC particles with a relatively high specific gravity, recovery of small particle size is disadvantageous, and small or suspended particles may be lost during recovery. If the dilution is performed to obtain clean and large SiC particles, there is a problem that the throughput and the SiC recovery rate may be reduced.

Japanese Patent Laid-Open No. 2009-61559 Disclosed is a method for treating waste liquid from a step of applying a high-pressure DC electric field to change surface charges of Si particles, passing water through a first and second filters, and cutting water with a diamond cutter while spraying pure water. However, although the movement of charged particles can occur freely in water, they do not move well due to the viscosity at the base of the glycol system we intend to use. Therefore, if this method is to be used, it should be diluted with water. In this case, the efficiency decreases due to the increase in throughput, and there is a disadvantage in that a lot of equipment costs are required to apply high-pressure DC.

Accordingly, the present inventors have made diligent efforts to solve the above problems. As a result, when the slurry waste liquid generated during solar cell wafer manufacturing is first centrifuged, a flocculant is added, the second centrifugal separation is performed, and the distillation process is performed. The present invention was completed by confirming that metal impurities and fine particles in the coolant are more effectively separated to improve the coolant regeneration efficiency.

An object of the present invention is to effectively separate the metal impurities and fine particles in the coolant (Coolant) generated during the manufacturing of the solar cell wafer to increase the coolant recycling efficiency, thereby minimizing waste generation, wafers for solar cells It is to provide a waste sludge recycling method and a recycling system generated during manufacturing.

In order to achieve the above object, the present invention (a) the first centrifugation step of separating the sludge waste liquid into the cutting agent and the waste cutting oil; (b) an agglomeration reaction step for forming flocs such as metal impurities and fine powder in the cutting oil through agglomeration and reaction by injecting a flocculant into the waste cutting oil from the first centrifugation step; (c) a second centrifugal separation step of separating the waste slurry from the flocculation step into waste sludge and coolant; (d) a distillation step for removing water in coolant from the second centrifugation step; And (e) reusing recycled coolant after the distillation step, and a waste sludge regeneration method and a regeneration system generated in a solar cell wafer manufacturing process.

The present invention also (a) a mixing tank for mixing the abrasive particles and the coolant (Coolant); (b) a primary centrifuge separating the sludge waste liquor into a cutting agent and waste cutting oil; (c) an agglomeration reaction tank for forming flocs such as metal impurities and fine powder in the cutting oil through agglomeration and reaction by injecting a flocculant into waste coolant from the first centrifuge; (d) a secondary centrifuge for separating the waste slurry from the flocculation tank into waste sludge and coolant; (e) a distillation tank for removing water in coolant from the secondary centrifuge; And (f) provides a waste sludge recycling system generated in the solar cell wafer manufacturing process comprising a storage tank for storing the regenerated coolant (Coolant) from the distillation tank.

According to the present invention, compared to the conventional sludge regeneration method, the addition of the coagulation reaction step of removing the metal impurities and fine powder floc in the waste cutting oil eliminates the step of removing the metal impurities in the existing waste cutting oil, thereby eliminating the cutting oil. By reducing the unit cost and increasing the regeneration efficiency, the service life of the recycled sludge can be extended, and a stable cutting oil and cutting agent mixed slurry can be supplied. In addition, it is possible to improve the initial wafer quality in the solar cell wafer manufacturing process, thereby reducing the amount of recycled sludge used in the solar cell wafer manufacturing process, and as a result, reducing the amount of waste slurry, which is a special industrial waste, In addition, the processing cost is also reduced, thereby lowering the manufacturing cost of the solar cell wafer.

1 is a process flowchart showing a slurry regeneration process according to an embodiment of the present invention.
Figure 2 shows the Jar Test test method for determining the optimal dose of flocculant in the present invention.

The present invention in one aspect, (a) the first centrifugation step of separating the sludge waste liquid into the cutting agent and the waste cutting oil; (b) an agglomeration reaction step of coagulating and reacting the coagulant with the waste cutting oil from the first centrifugation step to form a floctable floc such as metal impurities and fine powder in the waste cutting oil; (c) a second centrifugal separation step of separating the waste slurry from the flocculation step into waste sludge and coolant; (d) a distillation step for removing water in coolant from the second centrifugation step; And (e) reusing recycled coolant (Coolant) after the distillation step, relates to a waste sludge recycling method generated in the wafer manufacturing process for solar cells.

In the present invention, the step (a) after the wire sawing (heat sawing), after the heat treatment of the sludge waste liquid at 50 ~ 70 ℃ in a heat supply tank for viscosity reduction, centrifugation at 700 ~ 1500rpm and 5 ~ 10min reaction conditions It is characterized by separating. At this time, if the reaction rate is less than 700rpm or more than 1500rpm and the reaction time is less than 5min or more than 10min occurs a problem of the desired recovery particle recovery.

In the present invention, the flocculant used in the step (b) is preferably a cation-based flocculant, which is a second centrifugal separation to be performed later by flocculating metal impurities and fine powder in the waste cutting oil. It has the effect of effectively removing impurities in the step.

Examples of cationic flocculants that can be used in the present invention include polyacrylamide flocculants.

In addition, the step (b) is to perform a slow stirring in 30rpm (240sec) to finally reduce the speed by starting a rapid stirring at 300rpm (20sec) in the reaction conditions of 300 ~ 30rpm and 20 ~ 240sec. This causes flocculation to form flocs that can precipitate metal impurities, fines, etc. in the waste cutting oil. At this time, if the slow stirring is not performed gradually starting with rapid stirring or if the rapid stirring and the slow stirring are performed at the same speed and time, the floc is not formed or the formed floc is broken.

More specifically, the flocculant is mixed with water in a flocculant input tank (tank), a homogenized flocculent feedstock is prepared using an agitator, and the flocculent feedstock injection concentration is the total solids in the waste cutting oil. Inject 10 ~ 300ppm compared to the waste cutting oil into the waste cutting oil maintained at the optimum temperature of 50 ~ 70 ℃, depending on the content, the optimum coagulation input is determined through the Jar Test to be described in more detail in the following examples.

In the present invention, the step (c) is performed using a hydrocyclone (hydro-cyclone), characterized in that the centrifugation under the reaction conditions of 3000 ~ 4000rpm and 5 ~ 10min, which is in the coolant (Coolant) There is an effect of maximizing the removal of the total solids content. At this time, if the reaction rate is less than 3000rpm, there is a problem of precipitation of floc formed in step (b), and if it exceeds 4000rpm, there is no synergistic effect of floc removal compared to the reaction rate of 3000 ~ 4000rpm, and the reaction time is 5min. If it is less than the floc (Floc) can not be removed sufficiently, if it exceeds 10min compared to the 5 ~ 10min reaction time there is no synergistic effect of floc (Floc) removal.

In the present invention, step (d) uses reduced-pressure distillation, which removes about 6% or less of water in the coolant separated after step (c), thereby improving the quality of the regenerated coolant.

In the present invention, the regenerated coolant (Coolant) of the step (e) may be reusable to 0.05% or less of the total solid content of the water is finally removed after the step (d).

In another aspect, the present invention (a) a mixing tank for mixing the abrasive particles and the coolant (Coolant); (b) a primary centrifuge separating the sludge waste liquor into a cutting agent and waste cutting oil; (c) an agglomeration reaction tank for forming sedimentable flocs such as metal impurities and fine powder through agglomeration and reaction by inputting a coagulant into the waste cutting oil from the first centrifuge; (d) a secondary centrifuge for separating the waste slurry from the flocculation tank into waste sludge and coolant; (e) a distillation tank for removing water in coolant from the secondary centrifuge; And (f) relates to a waste sludge recycling system generated in the solar cell wafer manufacturing process comprising a storage tank for storing the regenerated coolant (Coolant) from the distillation tank.

In the present invention, the waste sludge regeneration system may further include a heat supply tank for viscosity reduction before the first centrifugal separation, and the regenerated coolant is regenerated in a mixing tank.

Hereinafter, the waste slurry recycling system generated in the solar cell wafer manufacturing process according to the present invention will be described in more detail with reference to the accompanying drawings.

Referring to the waste sludge recycling system according to the present invention according to the process flow chart shown in Figure 1, the mixing tank (3), ingot cutting process (5), wire sawing to mix the abrasive particles (1) and coolant (2) (Wire Sawing) (5) The slurry waste liquid tank (7) from the process, the heat supply tank (9) for viscosity reduction, the regenerated particle tank (Tank) entering the mixing tank (3) by primary centrifugation (11) ( 10) and the waste liquid tank 12 in which the waste cutting oil is collected, the flocculant is introduced into the waste liquid through a flocculant input tank (14), and then the coagulation reaction tank (13) for the reaction and the second centrifugal separator (15) It consists of a coolant (17), a coolant (17), a distillation tank (18) for removing water and a final coolant reservoir (20) in which the regenerated coolant (Coolant) is collected, and finally a coolant (Coolant) ) Is characterized in that it comprises a recycle (Recycle) in the mixing tank (3).

According to the present invention, it exhibits a high regeneration effect compared to the coolant regeneration efficiency of the conventional apparatus, and has an excellent regeneration efficiency of 0.05% or less of the total solid content in the coolant after the second centrifugal separation through an agglomeration reaction process. Finally, the coolant after the second centrifugation removes about 6% or less of moisture contained in the flocculation through a reduced pressure distillation process, thereby providing a waste sludge regeneration method for improving the quality of the recycled coolant.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these examples are for illustrative purposes only and that the scope of the present invention is not construed as being limited by these examples.

Jar Test for Calculation of Optimum Aggregation Conditions

First, the present embodiment was carried out under the same conditions. Prior to the present experiment, the total solids content of the waste cutting oil was analyzed before the coagulant injection, and an optimal concentration of coagulant feedstock (FeedStock (Water base)) was prepared, as described below. The test was performed according to the method shown in FIG.

In order to determine the homogeneity of the sample, a certain amount of the sample was taken by stirring, and in order to determine the optimum amount of flocculant, the amount of coagulant to the total solids in the waste cutting oil (10 to 300 ppm) was simultaneously added. In addition, in order to form flocs, slow stirring was performed within 30rpm (240sec) by gradually reducing the speed by gradually stirring at 300rpm (20sec) at agitation speed of 300 to 30rpm and agitation time of 20 to 240sec. Centrifugation was performed for 5 to 10 minutes at 3000 to 4000 rpm for separation. The total solids measurement method is to weigh a small amount of the mixed sample or the upper layer centrifuged after the experiment into a weighed container, weigh it, and heat it until the coolant is removed from the coolant boiling point. It was.

As a result, as shown in [Table 1], when the flocculant (FeedStock (Water base)) was added to 120ppm in the slurry waste liquid after centrifugation, the most optimal value was shown.

Injection amount of Cation-based flocculant compared to total solid waste oil order of experiment One 2 3 4 5 Cation system
Flocculant
No addition 30 ppm
(4.5 g) 60 ppm
(9g) 120 ppm
(18 g) 180 ppm
(27 g) Supernatant TS (%) 3.81% 1.58% 0.07% 0.02% 0.04%

1: abrasive grain 2: coolant
3: mixing tank 4: silicon ingot
5: Wiresawing 6: Wafer Cleaning
7: slurry waste liquid 8: wafer product
9: heat supply tank 10: regenerated particle tank (Tank)
11: first centrifugation 12: waste cutting oil
13: flocculation tank 14: flocculant input tank (Tank)
15: Secondary Centrifugation 16: Waste Sludge
17: Coolant 18: Distillation tank
19: Water removal 20: Recycled coolant

Claims (13)

Waste sludge regeneration in a solar cell wafer manufacturing process comprising the following steps:
(a) a first centrifugation step of separating the sludge waste liquid into a cutting agent and waste cutting oil;
(b) an agglomeration reaction step of agglomeration and reaction by adding a flocculant to the waste cutting oil from the first centrifugation step;
(c) a second centrifugal separation step of separating the waste slurry from the flocculation step into waste sludge and coolant;
(d) a distillation step for removing water in coolant from the second centrifugation step; And
(e) reusing recycled coolant after the distillation step;
The method of claim 1, wherein the sludge waste liquid of step (a) is subjected to a heat treatment at 50 ~ 70 ℃ and then centrifuged.
The method of claim 1, wherein the step (a) is waste sludge regeneration method, characterized in that carried out under the reaction conditions of 700 ~ 1500rpm and 5 ~ 10min.
The method of claim 1, wherein the coagulant of step (b) uses a cation-based coagulant. According to claim 1, wherein the step (b) is a rapid agitation at 300rpm (20sec) starting at 300rpm (20sec) under the reaction conditions of 300 ~ 30rpm and 20 ~ 240sec, the final agglomeration in slow slow stirring within 30rpm (240sec) Waste sludge regeneration method, characterized in that is carried out.
The method of claim 1 or 5, wherein the step (b) is characterized in that the flocculating floc by flocculating the metal impurities and fine powder in the waste cutting oil through rapid stirring and slow stirring. Waste Sludge Recycling Method
The method of claim 1, wherein the step (c) is a waste sludge regeneration method, characterized in that for applying a hydro-cyclone (Hydro-cyclone).
According to claim 1, wherein the step (c) is carried out in the reaction conditions of 3000 ~ 4000rpm and 5 ~ 10min characterized in that the floc (Floc) generated after the completion of the flocculation reaction step in step (b) is characterized in that Waste sludge regeneration method.

The method of claim 1, wherein the distillation in step (d) is distillation under reduced pressure.
The method of claim 1, wherein the regenerated coolant (Coolant) of step (e) is reusable to a total solid content of 0.05% or less.
Waste sludge regeneration system from solar cell wafer manufacturing process, including:
(a) a mixing tank for mixing abrasive particles and coolant;
(b) a primary centrifuge separating the sludge waste liquor into a cutting agent and waste cutting oil;
(c) an agglomeration reaction tank configured to agglomerate and react by adding a flocculant to the waste cutting oil from the first centrifuge;
(d) a secondary centrifuge for separating the waste slurry from the flocculation tank into waste sludge and coolant;
(e) a distillation tank for removing water in coolant from the secondary centrifuge; And
(f) A storage tank for storing regenerated coolant (Coolant) from the distillation tank.
The waste sludge regeneration system according to claim 11, further comprising a heat supply tank for reducing the viscosity before the first centrifugation.
12. The waste sludge regeneration system as set forth in claim 11, wherein the regenerated coolant is regenerated in a mixing tank.

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