JP2005313030A - Slurry regeneration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method used for regenerating slurry by efficiently recovering abrasive grain contained in sludge. <P>SOLUTION: In the slurry regeneration method, (1) used slurry 1 where slurry comprising abrasive grains and a water-based dispersion medium for dispersing them is contaminated with silicon grains is subjected to primary centrifugal separation to recover solid matter 3b mainly comprising the abrasive grains, (2) a liquid part 3a obtained by the primary centrifugal separation is subjected to secondary centrifugal separation to be separated into a liquid part 5a mainly comprising the dispersion medium, and residual sludge 5b, (3) the sludge 5b is diluted with a water-based medium, and then solid matter 7b is recovered by tertiary centrifugal separation, and (4) the solid matter 7b is used together with the solid matter 3b mainly comprising the abrasive grains as regenerated abrasive grains. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a slurry regeneration method.

  In general, a multi-wire saw (hereinafter referred to as “MWS”) is used to slice a silicon ingot into a wafer. When slicing a wafer using MWS, a slurry formed by dispersing abrasive grains in a dispersion medium is usually used. The slurry mainly serves as an abrasive and a heat dissipation agent. Silicon chips are usually mixed in the slurry used for wafer slicing. Slurry is usually used repeatedly, but as it is used, the mass ratio of silicon contained in the slurry increases. When the mass ratio of silicon becomes high, various problems occur when the wafer is sliced. For example, in the case where the mass of silicon chips in the slurry becomes 5% or more, due to a decrease in the cutting ability of the abrasive grains, defects such as TTV, warpage, and breakage occur successively on the wafer after slicing, resulting in a decrease in yield. Not only does this cause breakage of the slicing wire, resulting in a 0% yield, but also serious damage to the multi-wire saw body, such as breakage of the wire guide, leading to a reduction in operating rate. is there.

  In addition, when using an aqueous dispersion medium (for example, a mixture of water and polyethylene glycol (PEG)), when a certain amount is accumulated in the tank until wafer slicing is completed, a small amount of slurry is circulated. When the amount of silicon chips in the slice becomes 12% or more in the slice ratio, the slurry is retained between the wafers due to increase in the viscosity of the slurry due to mixing of chips. As a result, the wafer spreads in a skirt shape (peach shape) and the wire cannot be removed, or even if it does, the wire breaks the wafer, leading to a decrease in yield, and solids often stick to the wafer surface. In many cases, it takes time and time for cleaning.

  In order to prevent such a problem, it is necessary to regenerate the slurry by removing silicon chips from the used slurry. Slurry regeneration has been conventionally performed by the following method (see, for example, Patent Document 1). In the method, firstly, the used slurry is firstly centrifuged with a centrifugal separator (primary) 200G to 1200G ultra-low G (generally referred to as “primary separation”). Then, the dispersion medium and chips (for example, silicon chips) are separated into a low specific gravity liquid containing the main components. Generally, a specific gravity liquid mainly composed of abrasive grains is called an abrasive recovery liquid or a primary recovery liquid. Thereafter, a low specific gravity liquid mainly composed of a dispersion medium and chips (for example, silicon chips) is applied to a 2000G to 3500G centrifuge (secondary) (generally referred to as “secondary separation”), and chips (for example, silicon). The solids (commonly called sludge) and the dispersion medium of the chips) and abrasive grains (those not recovered by the primary separation or those refined) and the dispersion medium are separated into the main regenerated dispersion medium, and then the first centrifugation The abrasive particles obtained by the separation are mixed with the specific gravity liquid of the main component and the regenerated dispersion medium whose main component is the dispersion medium obtained by the second centrifugation, and the new abrasive particles and A new slurry is mixed to create a regenerated slurry and used in MWS.

In addition, Patent Document 2 discloses a slurry regeneration method.
JP 2003-340719 A JP 2003-230880 A

  However, in these methods, expensive abrasive grains contained in the sludge are discarded, which increases the manufacturing cost of the wafer.

  This invention is made | formed in view of the situation which concerns, and provides the method of collect | recovering the abrasive grains contained in sludge efficiently, and using it for reproduction | regeneration of slurry.

  The slurry regenerating method of the present invention comprises (1) primary centrifugation of used slurry in which silicon particles are mixed in a slurry comprising abrasive grains and an aqueous dispersion medium in which the abrasive grains are dispersed. The solid content of the component is recovered, and (2) the liquid obtained by the primary centrifugation is subjected to secondary centrifugation, whereby the dispersion medium is separated into the main liquid and the remaining sludge ( 3) After the sludge is diluted with an aqueous medium, the solid content is recovered by tertiary centrifugation, and (4) the solid content is used as a regenerated abrasive grain together with the solid content of the abrasive grains.

  Conventionally, sludge has been discarded for reasons such as high silicon content. The inventor found that the sludge was diluted with an aqueous medium, the solid content was recovered by centrifugation, and the abrasive grains could be recovered with a low silicon content, and the present invention was completed.

  According to the present invention, expensive abrasive grains can be used repeatedly without being discarded. Conventionally, the cost of disposal of sludge has been required, but according to the present invention, the amount of waste can be reduced, so that the cost of disposal can be reduced. Waste reduction is also beneficial from the viewpoint of environmental protection.

1. First Embodiment A slurry regenerating method according to a first embodiment of the present invention includes (1) a used slurry in which silicon particles are mixed in a slurry composed of abrasive grains and an aqueous dispersion medium for dispersing the abrasive grains. By primary centrifugation, the solid content of abrasive grains is recovered, and (2) the liquid content obtained by the primary centrifugation is subjected to secondary centrifugation, whereby the dispersion medium is the liquid content of the main component. And the remaining sludge. (3) The sludge is diluted with an aqueous medium, and then the solid content is recovered by tertiary centrifugation. (4) The solid content is combined with the solid content of the abrasive grains as a main component. It is used as a regenerated abrasive grain.

1-1. A process of recovering a solid content mainly composed of abrasive grains by first centrifuging a used slurry in which silicon grains are mixed in a slurry composed of abrasive grains and an aqueous dispersion medium for dispersing the abrasive grains. For example, it is made of SiC, diamond, CBN, alumina or the like. The water-based dispersion medium is, for example, water-soluble coolant (water-soluble organic solvent) such as ethylene glycol, propylene glycol, or polyethylene glycol, and water (about 5% to 15%, to avoid dangerous substances in the Fire Service Act) Mixed. Furthermore, a dispersing agent (bentonite) for dispersing abrasive grains and Si chips is usually added to the dispersion medium (about several percent). Silicon grains are, for example, silicon chips generated when a silicon wafer is formed by slicing a silicon ingot, or polishing chips generated when lapping a silicon wafer. The used slurry is, for example, a slurry that is used when a silicon wafer is formed by slicing a silicon ingot and silicon particles such as silicon chips are mixed. The primary centrifugation is preferably performed at 100 to 1000G. The primary slurry separates the used slurry into a first solid content and a first liquid content. The first solid content is mainly composed of abrasive grains. Abrasive grains generally have a specific gravity greater than that of silicon grains, and therefore settle faster than silicon grains. For this reason, when low-speed centrifugation is performed, the abrasive grains are selectively settled. Since the first solid content contains many abrasive grains, the first solid content can be used for slurry regeneration. On the other hand, the first liquid component mainly contains a dispersion medium and silicon particles.

1-2. Step of separating the liquid obtained by the primary centrifugation into the liquid mainly composed of the dispersion medium and the remaining sludge by secondary centrifugation The secondary centrifugation is preferably , 2000-5000G. When such high-speed centrifugation is performed, solid components that have not settled in the primary centrifugation also settle. The sludge (second solid content) obtained in this step contains silicon grains and abrasive grains that have not settled by primary centrifugation. Conventionally, sludge has a large mass ratio of silicon grains and cannot be used to regenerate slurry, and has been discarded. The present invention effectively removes silicon particles from this sludge and uses it to regenerate the slurry. The liquid component (second liquid component) whose main component is the dispersion medium contains abrasive grains and silicon grains. For this reason, if the entire amount of the second liquid is used for slurry regeneration, the silicon mass ratio of the regenerated slurry becomes too large, which is not preferable. It is preferable to further comprise a step of distilling at least a part of the second liquid, recovering the liquid obtained by distillation, and using it for slurry regeneration. The liquid fraction obtained by distillation usually consists essentially of a dispersion medium. Therefore, by using this liquid for slurry regeneration, the silicon mass ratio of the slurry to be regenerated can be reduced. Since the dispersion medium usually contains an organic solvent, there is a risk of igniting during distillation in distillation under normal pressure. Therefore, the distillation is preferably performed in a vacuum (about 20 Torr or less). Moreover, it is preferable to perform component analysis about the liquid component obtained by distillation, and to use for the reproduction | regeneration of slurry, after adjusting a component.

1-3. Step of recovering solid content by tertiary centrifugation after diluting sludge with aqueous medium As described above, sludge contains silicon grains and abrasive grains that have not settled by primary centrifugation. When the sludge is diluted with an aqueous medium, the sludge is dispersed in water. The aqueous medium is preferably a substantially neutral or alkaline aqueous medium (solution), and a small amount of silicon particles is dissolved in such an aqueous medium. Further, a larger amount of silicon particles is dissolved in an alkaline aqueous medium. The alkaline aqueous medium is, for example, an aqueous NaOH solution. The pH of the alkaline aqueous medium is preferably 8-14. The “aqueous medium” also includes a liquid mixture containing pure water.

  The tertiary centrifugation is preferably performed at 2000 to 5000G. The diluted solution obtained by diluting the sludge with the aqueous medium is separated into a third liquid component and a third solid content by the tertiary centrifugation. The third liquid component contains silicon dissolved in water and silicon particles dispersed in water. For this reason, the silicon mass ratio contained in the third solid content is usually smaller than the sludge. And since the third solid content contains many abrasive grains and the mass ratio of silicon is small, the third solid content can be recovered and used to regenerate the slurry.

  Moreover, it is preferable to further comprise a step of solid-liquid separation of the third liquid component by sedimentation, centrifugation or distillation, and adding the obtained liquid component to sludge to dilute. The third liquid component is mainly composed of water and silicon contained therein. By reducing the silicon content in the third liquid by sedimentation, centrifugation or distillation, this third liquid can be used again for sludge dilution. Moreover, before using for dilution of 3rd solid content, you may adjust a component so that the liquid component obtained by solid-liquid separation may become alkaline. In addition, if the third liquid is allowed to stand for a while after the third centrifugation, a silicon lump may precipitate in the third liquid, but this silicon lump is removed by sedimentation, centrifugation or distillation. can do. Moreover, it is preferable to further provide the process of neutralizing a 3rd liquid component before this solid-liquid separation. The third liquid component is usually alkaline. Even when a neutral aqueous medium is added to the second solid and diluted, the third liquid becomes alkaline due to dissolution of silicon. As described above, silicon dissolves more in an alkaline aqueous medium than neutral. Therefore, silicon is deposited by neutralizing the third liquid component. Thereafter, silicon can be effectively removed from the third liquid by sedimentation or centrifugation. Centrifugation here is performed at 2000-5000G, for example.

  In addition, about the solid content obtained by 1-3, you may perform the process of 1-3 again. This is because the silicon contained in the solid content can be further removed by repeating the process 1-3.

  Moreover, you may further provide the process of neutralizing the solid content (3rd solid content) collect | recovered by the tertiary centrifugation. If the third solid content is used for slurry regeneration while remaining alkaline, the regenerated slurry becomes alkaline. If the regenerated slurry is alkaline, the solubility of silicon increases and the viscosity of this slurry increases. The neutralization treatment includes a method in which an acid such as hydrochloric acid or nitric acid is added and a neutralization reaction is performed while stirring. The reaction may be accelerated by heating. The regenerated slurry may be neutralized.

  Moreover, you may further provide the process of drying the solid content (3rd solid content) collect | recovered by the tertiary centrifugation. If the third solid content is left for a while (for example, 2 hours), the silicon remaining in the third solid content may react with the water remaining in the third solid content, thereby increasing the viscosity of the regenerated slurry. . For this reason, there is a problem that the obtained third solid content needs to be quickly used for slurry regeneration. By further providing this step and removing residual moisture, the reaction between water and silicon can be prevented, so that the above problem is solved. This step is preferably performed after the neutralization treatment.

  Moreover, you may further provide the process of classifying the solid content collect | recovered by the tertiary centrifugation and adjusting the particle size of the abrasive grain contained in this solid content. Classification is a method of removing particles having a predetermined particle size (for example, 5 μm) or less from a solid content composed of particles having various particle sizes (for example, an average particle size of 20 μm), or a predetermined particle size (for example, 5 μm). Refers to a method of extracting only ~ 20 μm). The abrasive grains are pulverized in a silicon slicing step or the like, and the particle diameter is reduced. Abrasive grains having a predetermined particle diameter or less do not function as an abrasive, and therefore are not wasted even if removed. Further, by performing classification, silicon particles having a predetermined particle size (for example, 5 μm) or less can be removed. For this reason, by performing the classification, it is possible to increase the removal efficiency of the silicon grains without wasting the abrasive grains. This step may be performed either before or after the drying treatment. What is performed before the drying treatment is wet classification, which can be performed by mixing water and fine particles and classifying using a specific gravity difference. What is performed after the drying treatment is dry classification, which can be performed by mixing fine particles with air and blowing away, and dividing the particle size by the difference in weight and specific gravity of the particles.

1-4. Step of using this solid content (third solid content) as regenerated abrasive grains together with the solid content (first solid content) of which the abrasive grains are the main component As described above, the first and third solid contents are There are many abrasive grains and the silicon mass ratio is small. For this reason, the 1st and 3rd solid content can be utilized as regenerated abrasive grains. The second liquid component may be utilized as a regenerating dispersion medium because most of its components are the dispersion medium and the silicon mass ratio is small. For this reason, when the first and third solid components and the second liquid component are used for slurry regeneration, a regenerated slurry having a small silicon mass ratio can be obtained. When the slurry is regenerated, the slurry components are usually adjusted by adding at least one of new abrasive grains, a dispersion medium, and a dispersant.

2. Second Embodiment A slurry regenerating method according to a second embodiment of the present invention is based on solid-liquid separation of used slurry in which silicon particles are mixed in a slurry composed of abrasive grains and an aqueous dispersion medium for dispersing the abrasive grains. After the solid content obtained by the above is diluted with an aqueous medium, the solid content is recovered by centrifugation or filtration and used as recycled abrasive grains.

  The description of the first embodiment is basically applicable to the second embodiment.

  In the first embodiment, the used slurry is separated into a solid content and a liquid content by centrifugation, but in the second embodiment, the solid-liquid separation is not necessarily limited to centrifugation. Solid-liquid separation may be performed by filtration, distillation, or a combination thereof in addition to centrifugation. Further, the solid-liquid separation may be performed in one stage or in two or more stages.

  In the first embodiment, the used slurry is separated into solid and liquid by centrifugation, but in the second embodiment, this solid-liquid separation is performed by centrifugation or filtration. be able to.

  Since MWS for solar cells uses MWS with the focus on production capacity, four silicon ingots (125W × 125D × 400L) are processed at a time in one slice, and wafers (125W × 125D × 0.3L) can be processed about 3200 sheets. The slurry tank used at the time of processing is about 200 L in size, and abrasive grains (specific gravity: 3.21) and an aqueous dispersion medium (specific gravity: 1) are mixed at a mass ratio of 1: 1. . Specifically, SiC grains having an average particle diameter of 14 μm (No. 800) are used as abrasive grains, and propylene glycol, water (about 5% to 15%, dangerous substances in the Fire Service Act are used as a dispersion medium. In order to avoid this, a mixture of bentonite (about 0.5%) is used as a dispersant for dispersing abrasive grains and Si chips. At this time, about 20 kg of solid matter such as silicon chips is mixed into the slurry at one time. When this used slurry is repeatedly regenerated and sliced using a slurry regenerator as described in the prior art, about 12% silicon chips remain in the used slurry, and 6% Silicon chips of a certain concentration will remain. As a method of keeping the mass ratio of the remaining silicon chips low, the fact is that about 50% to 70% of the secondary separation liquid is discarded. That is, in the conventional slurry regenerating apparatus, even if the secondary separation liquid is discarded by about 50% to 70%, the silicon chip removal rate is about 50%. The present invention has been made with a focus on reducing the waste by reusing the solid matter generated in the secondary portion.

  Hereinafter, the method for regenerating the slurry according to the first embodiment will be described with reference to FIG.

  First, the used slurry 1 is guided to a primary centrifuge, and subjected to primary centrifugation at an ultra-low G of 500 G, the first solid content 3b mainly composed of abrasive grains, and a dispersion medium + Chips (for example, silicon chips) are separated into the first liquid component 3a as the main component. The first solid content 3b is recovered and used for slurry regeneration (recovered abrasive grains 4).

  Next, the first liquid fraction 3a is guided to the secondary centrifuge, and the second centrifugal part is subjected to the secondary centrifugal separation with a centrifugal force of G of 3500G. (For example, silicon chips) and abrasive grains are separated into the main component sludge 5b. The sludge 5b is generally called sludge. The second liquid component 5a is recovered, and at least a part thereof is used for slurry regeneration (regeneration dispersion medium 6).

  Next, the sludge 5b is led to a dilution tank and diluted with water 8. This is because sludge 5b has a small amount of organic solvent component (about 20% by weight) and cannot be introduced into the centrifuge, and is also necessary to improve the performance of the centrifuge. Dilute to 300 CP. (Dilution was performed by mass ratio, and sludge: water = 1: 1.) After 1H dilution, tertiary centrifugation was performed at 3500 G, and the diluted solution was a third liquid content 7a and a third solid content 7b. Separated. Next, the 3rd solid content 7b was neutralized and the reproduction | regeneration abrasive grain 9 was obtained.

  This regenerated abrasive grain 9 contains SiC, water, Si, organic solvent, other Fe, Cu, etc., but the weight% is as shown in Table 1. It can be seen that the main component is SiC.

  In addition, the regenerated abrasive grains 9 when diluted with alkaline water (here, NaOH 1% (a mixture of NaOH granules in 1 kg and water 99 kg)) were used for SiC, water, Si, an organic solvent component, and other Fe, Cu, and the like are contained, but the weight% is as shown in Table 2.

  The reason for the increase in the SiC recovery rate and the decrease in the Si recovery rate is thought to be that Si reacted with alkali water and changed to a soluble state in water.

The reaction is
Si + 4NaOH = Si (Na) 4 O 4 - + 2H 2
Si (Na) ₄ O ₄ Is generally called water glass (sodium silicate) and is known to be soluble in water. Also, this reaction requires moisture.

  From the above, the amount of sludge discarded was almost zero except for the liquid content from the third centrifugation. In addition, in Example 5, the liquid fraction obtained from the third centrifugation is recovered and reused.

  Using the recovered abrasive grains 4, the regenerated abrasive grains 9 and the regenerated dispersion medium 6 and using the new dispersion medium to produce a regenerated slurry based on the specific gravity and viscosity, and using it in MWS, There was no particular effect. In general, in slices, the TTV value is said to show sharpness, but a comparison was made between a new dispersion medium and a new slurry made of new abrasive grains. In addition, it compared with the liquid which repeated the said reproduction | regeneration 100 times. Slicing conditions were the same and unidirectional cutting was performed. TTV sliced about 3000 slices per slice in 10 hours. It is an average value of TTV of all wafers obtained by slicing. Here, TTV is an index indicating the unevenness of the thickness within the wafer surface defined by JIS H0611. Here, the thickness of one point at the center of the wafer and the thickness at eight points at the peripheral portion were measured using a dial gauge, and the difference between the maximum value and the minimum value was measured as TTV.

  From Table 3, it was found that the yield and TTV are comparable to those when using a new dispersion medium.

  As shown in FIG. 2, the slurry regeneration method according to Example 2 was the same as the regeneration method of Example 1, except that the dispersion medium was removed by adding a drying step after the neutralization treatment. For drying, a vibration dryer was used, and ceramic balls were put inside to prevent it from being fooled. In the case of Example 1, if it was not used within 1 to 2 hours after purification, the remaining Si reacted with moisture and the viscosity increased somewhat (100 CP → 130 CP: state of regenerated slurry). Although it was implemented to prevent this, the recovery rate did not change, but it became possible to use it after a while in production.

  As shown in FIGS. 3 and 4, the slurry regeneration method according to the third embodiment includes a classification step before or after drying in the regeneration method according to the second embodiment. We confirmed how slicing accuracy and yield improved by classification. The classification was performed using a dry classifier under conditions that remove 5 μm or less. The particle size distribution before and after classification is shown in FIG. As can be seen from FIG. 5, particles having a particle size of 5 μm or less were removed by classification. Since most of the silicon chips have a particle size of 5 μm or less, most of the silicon chips can be removed by removing particles of 5 μm or less.

  In general, in slices, the TTV value is said to show sharpness, but a comparison was made between a new dispersion medium and a new slurry made of new abrasive grains. In addition, it compared with the liquid which repeated the said reproduction | regeneration 100 times. Slicing conditions were the same and unidirectional cutting was performed. TTV sliced about 3000 slices per slice in 10 hours. It is an average value of TTV of all wafers obtained by slicing. From Table 4, it was found that the yield and TTV were comparable to the case where a new dispersion medium was used. Further, it was found that the TTV yield was improved as compared with the Example of Example 1.

  When the component analysis was performed about the reproduction | regeneration abrasive grain 9 obtained by classification, the following results were obtained.

When diluted with water

When diluted with alkaline water

  The amount of waste was 10% by weight when the sludge was discarded as 1.

  As shown in FIG. 6, the slurry regeneration method according to the fourth embodiment reuses the third liquid portion 7 a in the regeneration method of the first embodiment. First, the third liquid 7a is neutralized. By neutralizing, silicon dissolved in the third liquid portion 7a is deposited. In this state, the third liquid portion 7a is distilled, settled or centrifuged (3000G). The liquid 8a obtained by distillation, sedimentation or centrifugation can be used again for diluting the sludge 5b. What remains after distillation, sedimentation or centrifugation is treated as waste, but the waste generated here is 10% to 15% by weight when the sludge is discarded as 1. Overall, a reduction effect of up to 85% by weight to the worst 75% by weight was obtained.

  As shown in FIG. 7, the slurry regeneration method according to Example 4 is the same as the regeneration method of Example 1, except that a part of the second liquid 5a is used after vacuum distillation and component adjustment (distillation dispersion medium 6a). ). In the regeneration method of Example 1, when the entire second liquid 5a is used for slurry regeneration, the silicon mass ratio of the regenerated slurry becomes too large due to silicon contained in the second liquid 5a. There was a problem. In this example, a part of the second liquid portion 5a was used for slurry regeneration as it was, and the rest was used for slurry regeneration after vacuum distillation and component adjustment. Table 7 shows the component ratio of the second liquid 5a before distillation, and Table 8 shows the component ratio after distillation.

  The recovery rate of the dispersion medium was 98%, and no other solid content was detected. In addition, since an aqueous dispersion medium (which frequently uses PEG, PG and water as an additive, etc.) is used as the dispersion medium, the boiling point was relatively low and distillation was easy. Thereafter, the dispersion medium was analyzed to supplement the components that had fallen out, and used as a distillation dispersion medium. This time, a new dispersion medium was added to the liquid after distillation to adjust the viscosity and specific gravity. Moreover, although PH is neutral and may require pH adjustment, it has not been implemented this time. As a result, when the amount of waste in the entire system is 1, a reduction effect of 83% by weight to 73% by weight at worst is obtained.

  In particular, this embodiment is characterized when an aqueous dispersion medium is used as the dispersion medium, and refers to a dispersion medium produced using propylene glycol, polyethylene glycol, water or the like as a main component. Further, the present invention can be applied for the purpose of recovering abrasive grains even when quantitative exchange is performed without having a slurry recycling system.

It is a flowchart which shows the slurry reproduction | regeneration method based on Example 1 of this invention. It is a flowchart which shows the slurry reproduction | regeneration method based on Example 2 of this invention. It is a flowchart which shows the slurry reproduction | regeneration method based on Example 3 of this invention. It is a flowchart which shows the slurry reproduction | regeneration method based on Example 3 of this invention. It is a graph which shows the particle size distribution before and behind classification based on Example 3 of this invention. It is a flowchart which shows the slurry regeneration method which concerns on Example 4 of this invention. It is a flowchart which shows the slurry reproduction | regeneration method based on Example 5 of this invention.

Claims (11)

(1) The used slurry in which silicon particles are mixed in a slurry composed of abrasive grains and an aqueous dispersion medium that disperses the abrasive grains is subjected to primary centrifugal separation, thereby recovering a solid content mainly composed of abrasive grains,
(2) The liquid obtained by the primary centrifugation is subjected to secondary centrifugation, so that the dispersion medium is separated into the main liquid and the remaining sludge;
(3) After the sludge is diluted with an aqueous medium, the solid content is recovered by tertiary centrifugation,
(4) A slurry reclaiming method, wherein the solid content is used as reclaimed abrasive grains together with the solid content of the abrasive grains as a main component.   The slurry regeneration method according to claim 1, wherein the secondary centrifugation is performed with a higher centrifugal force than the primary centrifugation.   The slurry regeneration method according to claim 1, wherein the aqueous medium is a substantially neutral or alkaline aqueous solution.   The slurry regeneration method of Claim 1 further equipped with the process of neutralizing the solid content collect | recovered by the tertiary centrifugation.   The slurry regeneration method according to claim 1, further comprising a step of drying the solid content recovered by the tertiary centrifugation.   The slurry regeneration method according to claim 1, further comprising a step of classifying the solid content recovered by the tertiary centrifugation and adjusting the particle size of the abrasive grains contained in the solid content. The liquid obtained by the third centrifugation is solid-liquid separated by sedimentation, centrifugation or distillation,
The slurry regeneration method according to claim 1, further comprising a step of adding and diluting the obtained liquid to sludge.   The slurry regeneration method according to claim 7, further comprising a step of neutralizing a liquid component obtained by tertiary centrifugation before solid-liquid separation. Distilling at least a portion of the liquid obtained by secondary centrifugation;
The slurry regeneration method according to claim 1, further comprising a step of recovering the liquid component obtained by distillation and using it for slurry regeneration.   (1) Solid or solid separation obtained by solid-liquid separation of used slurry in which silicon particles are mixed in a slurry composed of abrasive grains and an aqueous dispersion medium in which the abrasive grains are dispersed is diluted with an aqueous medium, and then centrifuged or filtered. A slurry reclaiming method characterized in that the solid content is recovered by the above and used as reclaimed abrasive grains.   6. The slurry regeneration method according to claim 5, wherein the aqueous medium is a substantially neutral or alkaline aqueous solution.

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