JP6085500B2 - Wire source slurry coolant recovery system - Google Patents

Description

  The present invention relates to a wire source slurry in which coolant can be recovered efficiently and at a high recovery rate from slurry waste liquid taken out from a fixed abrasive wire saw used when cutting a silicon ingot workpiece in the manufacturing process of solar cells and the like. The present invention relates to a coolant recovery device.

  Conventionally, a wire saw is used as an apparatus for manufacturing a wafer by cutting a workpiece made of a silicon ingot. In this wire saw, a thin wire row to which tension is applied is run, and a workpiece is pressed against the wire row while spraying a slurry containing abrasive grains for cutting on a coolant for removing cutting heat. Thus, there is a free abrasive wire saw that cuts a workpiece into a plurality of wafers simultaneously (see, for example, Patent Document 1). As the coolant, a mixture of water and glycol or a mixture made only of glycol not containing water is used.

  On the other hand, in recent years, by using a fixed abrasive wire array in which diamond abrasive grains or the like are preliminarily adhered to the surface of a thin wire, the workpiece is pressed against a plurality of wafers by pressing the workpiece against the wire array while spraying the coolant. There is a fixed abrasive wire saw that is cut simultaneously (see, for example, Patent Document 2).

  In the loose abrasive wire saw and the fixed abrasive wire saw, when a silicon ingot is cut to form a large number of wafers, it is generally carried out by one batch operation from the start to the end of the cutting operation. is there. In addition, the slurry waste liquid from the wire saw is being studied for slurry management in which coolant and abrasive grains are separated and recovered for effective use of resources, volume reduction of waste, and the like.

  In the loose abrasive wire saw, a slurry in which abrasive particles are mixed with coolant is supplied to the wire to cut the silicon ingot. Therefore, from the loose abrasive wire saw, coolant, abrasive grains (SiC) and chips (Si) Slurry waste liquid mixed with is discharged. Therefore, in order to separate and recover such slurry waste liquid, the slurry waste liquid is separated into a coolant and a solid content, and the solid content is separated in two stages of abrasive grains = recovery and chips = discard. Here, when continuous separation is to be performed, it is necessary to continuously extract slurry waste liquid and match coolant recovery, abrasive grain recovery, and chip disposal from the extracted slurry waste liquid. In general, the batch type is the mainstream for separating and recovering slurry waste liquid from the loose abrasive wire saw because the amount of the recovered material does not match the amount of the recovered material.

  Generally, a centrifuge or filter is used to collect coolant from the slurry waste liquid. As the cutting operation progresses, the amount of chips in the slurry waste liquid increases, so good cutting work continues. In order to achieve this, it is necessary to separate so that the amount of chips in the regenerated slurry is as small as possible, or to reduce the amount (concentration) of chips in the slurry by increasing the amount of new slurry added. become.

  For this reason, the patent applicant's application that discharges a part of the slurry as waste slurry so that the slurry concentration (chip concentration) is maintained at the specified concentration, thereby reducing the supply amount of new slurry There is a slurry management device for fixed abrasive wire saws (see Patent Document 3).

Japanese Patent Laid-Open No. 11-309664 JP 2010-029998 A JP 2012-125891 A

  According to Patent Document 3, the amount of new slurry used can be reduced, but since the solid content is separated only by the centrifuge, the fine chips in the separated liquid are separated as the cutting operation continues. Accumulation of particles increases the amount of waste slurry discarded, resulting in an increase in the amount of new slurry supplied.

  In order to recover the total amount of coolant in the slurry waste liquid, more liquid coolant can be obtained by removing solids almost completely by further filtering or distilling the separated liquid containing fine particles separated by the centrifuge. It is conceivable to collect.

  However, the method using filtration generally requires an expensive cross-flow filtration device, and further, there is a problem that the separated solid matter is discharged as concentrated liquid sludge without being dried. That is, the coolant contained in the concentrated liquid sludge has been discarded. In addition, since the concentration progresses in the process of filtration and the viscosity of the treatment liquid changes, there is also a problem that the filtration rate is not stable.

  In addition, in the method using distillation, the mainstream is changing from the conventional glycol-based coolant to the water-based coolant having a high water content, and this water-based coolant has a larger latent heat of water than glycol. A large amount of energy is required to evaporate water when separating the solid content, which increases the cost and is difficult to implement in practice.

  The present invention has been made in view of the above-described conventional problems, and provides a coolant recovery device for a wire source slurry that recovers coolant from slurry waste liquid from a fixed abrasive wire saw efficiently and at a high recovery rate. There is.

  In order to achieve the above object, the wire source slurry coolant recovery apparatus of the present invention introduces a slurry waste liquid storage tank for storing slurry waste liquid from a fixed abrasive wire saw, and a part of the slurry waste liquid in the slurry waste liquid storage tank. A primary centrifugal separator for taking out the primary regeneration coolant obtained by separating the sludge, a light liquid tank for taking in the remainder of the slurry waste liquid from the slurry waste liquid storage tank as a light liquid, and a light liquid in the light liquid tank A filter for separating and taking out the secondary regeneration coolant, and a cyclone for introducing the concentrated liquid from which the secondary regeneration coolant has been separated by the filter, separating the light liquid and returning the separated light liquid to the light liquid tank A separator, a heavy liquid tank for storing the heavy liquid separated from the light liquid by the cyclone separator, and the light liquid obtained by introducing the heavy liquid in the heavy liquid tank and separating the sludge into the light liquid tank. A secondary centrifuge to return And wherein the door.

  In the above-described wire source slurry coolant recovery device, the primary regeneration coolant from the primary centrifugal separator, the secondary regeneration coolant from the filter, and new coolant are mixed and adjusted, and the adjusted coolant is fixed. It is preferable to have a coolant supply tank that supplies the abrasive wire saw.

  According to the wire source slurry coolant recovery apparatus of the present invention, a part of the slurry waste liquid from the slurry waste liquid storage tank, the light liquid from the secondary centrifugal separator, and the light liquid from the cyclone separator are supplied to the light liquid tank. Therefore, the light liquid in the light liquid tank has a low solid content concentration and a high fluidity. Therefore, this light liquid is supplied to a filter suitable for separating a slurry having a low solid content concentration and a high fluidity to separate the secondary regeneration coolant, so that the separation capacity of the filter is enhanced and the secondary regeneration is performed. The amount of coolant taken out can be increased. Filters are generally low in solids concentration and are suitable for stable slurry separation. When the solids concentration increases or fluctuates, clogging is likely to occur, and membrane replacement and cleaning are frequently performed. However, according to the present invention, the ability of the filter is effectively enhanced, and the frequency of membrane replacement and cleaning can be reduced.

  In addition, since the concentrated liquid that is not separated by the filter is introduced into the cyclone separator and the heavy liquid separated from the light liquid is supplied to the heavy liquid tank, the heavy liquid in the heavy liquid tank has a high solid content concentration and fluidity. Is low. Therefore, since this heavy liquid is supplied to a secondary centrifuge suitable for separating a slurry having a high solid content concentration and low fluidity to separate light liquid, the separation capacity of the secondary centrifuge is increased. The solid content can be efficiently removed, and as a result, the solid content concentration of the light liquid can be lowered and the capacity of the filter can be increased.

  Therefore, according to the present invention, it is possible to obtain an excellent effect that almost all of the coolant in the slurry waste liquid can be recovered and reused.

It is the schematic which shows one Example of the coolant collection | recovery apparatus of the wire source slurry in this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an embodiment of a coolant recovery apparatus for a wire source slurry according to the present invention. In the figure, reference numeral 1 denotes a fixed abrasive wire saw. In the fixed abrasive wire saw 1, a coolant 2 is supplied and a fixed abrasive wire (not shown) is shown. The sludge waste liquid 3 discharged from the fixed abrasive wire saw 1 is received by the liquid receiving container 4.

  In the figure, reference numeral 5 denotes a slurry waste liquid storage tank for storing the slurry waste liquid 3 from the liquid receiving container 4. When a plurality of fixed abrasive wire saws 1 are provided, the slurry waste liquid 3 from the plurality of fixed abrasive wire saws 1 is supplied to the slurry waste liquid storage tank 5.

  In the figure, reference numeral 6 denotes a primary centrifuge provided with a primary centrifuge 7, and the primary centrifuge 7 introduces a part 3a of the slurry waste liquid 3 in the slurry waste liquid storage tank 5 to produce sludge. 8 and the primary regeneration coolant 9 are separated, the sludge 8 is supplied to the sludge tank 10, and the primary regeneration coolant 9 is supplied to the primary regeneration coolant tank 11. Then, the primary regeneration coolant 9 in the primary regeneration coolant tank 11 is supplied to the coolant supply tank 12 and stored.

  In the figure, reference numeral 14 denotes a light liquid tank that receives and stores the remaining portion 3 b of the slurry waste liquid 3 from the slurry waste liquid storage tank 5 as the light liquid 13.

  In the figure, reference numeral 15 denotes a filter for introducing the light liquid 13 stored in the light liquid tank 14 and separating the secondary regeneration coolant 16. The secondary regeneration coolant 16 separated by the filter 15 is a premix tank. 17 is supplied.

  In the figure, reference numeral 19 denotes a cyclone separator which introduces the concentrated liquid 18 from which the secondary regeneration coolant 16 has been separated by the filter 15 and separates it into a light liquid 20 and a heavy liquid 21, which are separated by the cyclone separator 19. The light liquid 20 is returned to the light liquid tank 14 and the heavy liquid 21 is supplied to and stored in the heavy liquid tank 22. The light liquid tank 14, the filter 15, the cyclone separator 19, and the heavy liquid tank 22 form a coolant recovery unit 32.

  In the figure, reference numeral 23 denotes a secondary centrifuge provided with a secondary centrifuge 24. The secondary centrifuge 24 introduces the heavy liquid 21 in the heavy liquid tank 22 to introduce sludge 25 and light liquid 26. The sludge 25 is supplied to the sludge tank 27, and the light liquid 26 is supplied to the light liquid tank 28 and stored. The light liquid 26 in the light liquid tank 28 is returned to the light liquid tank 14. Since the sludges 8 and 25 of the sludge tank 10 and the sludge tank 27 are mostly chips generated by cutting the silicon ingot, the sludges 8 and 25 can be supplied to a silicon recovery device (not shown) to recover silicon. it can.

  A new coolant 29 is supplied to the premixing tank 17 to which the secondary regeneration coolant 16 is supplied, and the secondary regeneration coolant 16 and the new coolant 29 are mixed in the premixing tank 17. The mixed coolant 30 mixed in the premix tank 17 is supplied to the coolant supply tank 12 and mixed with the primary regeneration coolant 9 from the primary centrifugal separator 6 to generate the coolant 2. Then, the coolant 2 in the coolant supply tank 12 is supplied to the fixed abrasive wire saw 1. When a plurality of fixed abrasive wire saws 1 are provided, the coolant 2 is supplied to the plurality of fixed abrasive wire saws 1. In the figure, 31 is a detector for detecting the properties of the coolant 2, and the primary regenerative coolant 9 and the secondary regenerative coolant are set so that the properties of the coolant detected by the detector 31 have the desired predetermined properties. 16 and the mixing of the new coolant 29 is adjusted. In the figure, P is a pump.

  Next, the operation of the above embodiment will be described.

  The slurry waste liquid 3 discharged from the fixed abrasive wire saw 1 to the liquid receiving container 4 is stored in a slurry waste liquid storage tank 5. A portion 3a of the slurry waste liquid 3 in the slurry waste liquid storage tank 5 is supplied to the primary centrifugal separator 7 and separated into the sludge 8 and the primary regeneration coolant 9, and the sludge 8 is supplied to the sludge tank 10. The primary regeneration coolant 9 is supplied to the primary regeneration coolant tank 11. The primary regeneration coolant 9 in the primary regeneration coolant tank 11 is supplied to the coolant supply tank 12 and stored.

  The remaining portion 3 b of the slurry waste liquid 3 from the slurry waste liquid storage tank 5 is supplied as a light liquid 13 to the light liquid tank 14. The light liquid 13 in the light liquid tank 14 is supplied to the filter 15 to separate the secondary regeneration coolant 16, and the separated secondary regeneration coolant 16 is supplied to the premix tank 17.

  The concentrated liquid 18 from which the secondary regeneration coolant 16 has been separated by the filter 15 is supplied to a cyclone separator 19 to be separated into a light liquid 20 and a heavy liquid 21, and the light liquid 20 is returned to the light liquid tank 14. It is. The heavy liquid 21 from which the light liquid 20 has been separated by the cyclone separator 19 is stored in the heavy liquid tank 22.

  The heavy liquid 21 in the heavy liquid tank 22 is supplied to the secondary centrifuge 24 of the secondary centrifugal separator 23 and separated into the sludge 25 and the light liquid 26. The sludge 25 is supplied to the sludge tank 27, and the light The liquid 26 is supplied to the light liquid tank 28. Then, the light liquid 26 in the light liquid tank 28 is returned to the light liquid tank 14.

  A new coolant 29 is supplied to the premix tank 17, and a mixed coolant 30 in which the secondary regeneration coolant 16 and the new coolant 29 are mixed in the premix tank 17 is supplied to the coolant supply tank 12, and Mixing and adjustment with the primary regeneration coolant 9 from the primary centrifugal separator 6 results in the coolant 2. Then, the primary regeneration coolant 9, the secondary regeneration coolant 16, and the new coolant 29 stored in the coolant supply tank 12 are adjusted so that the property of the coolant detected by the detector 31 becomes a predetermined desired property. The mixing ratio is adjusted, and the adjusted coolant 2 is supplied to the fixed abrasive wire saw 1.

  The detector 31 manages the properties of the coolant by using a viscometer and a hydrometer, and manages the water content by providing a moisture meter or a refractometer in order to monitor the increase or decrease of the moisture content, which is a problem of the water-based coolant. be able to.

  As described above, the remaining portion 3 b of the slurry waste liquid 3 from the slurry waste liquid storage tank 5, the light liquid 26 from the secondary centrifugal separator 23, and the light liquid 20 from the cyclone separator 19 are supplied to the light liquid tank 14. Thus, the light liquid 13 in the light liquid tank 14 has a low solid content concentration and a high fluidity. Therefore, since this light liquid 13 is supplied to a filter 15 suitable for separating a slurry having a low solid content concentration and a high fluidity to separate the secondary regeneration coolant 16, the separation ability of the filter 15 is increased. The removal amount of the secondary regeneration coolant 16 can be increased.

  Further, the concentrated liquid 18 that is not separated by the filter 15 is introduced into the cyclone separator 19 and the heavy liquid 21 separated from the light liquid 20 is supplied to the heavy liquid tank 22, whereby the heavy liquid 21 in the heavy liquid tank 22 is obtained. Solid content concentration is large and fluidity is low. Accordingly, since the heavy liquid 21 is supplied to the secondary centrifuge 24 suitable for separating the slurry having a high solid content concentration and low fluidity to separate the light liquid 26, the separation of the secondary centrifuge 24 is performed. The capacity can be increased and the amount of the light liquid 26 taken out can be increased.

  Therefore, according to the present invention, most of the coolant in the slurry waste liquid 3 can be recovered and reused. That is, the secondary centrifuge 24 can remove almost the entire amount of the sludge 25. The concentrated liquid obtained by conventional filtration has a maximum liquid content of about 70 to 75%, whereas the liquid content of the sludge 25 from the secondary centrifuge 24 is 50% or less. Since the liquid component of this difference is recovered as a coolant, the coolant can be recovered at a high recovery rate. As described above, the coolant can be recovered from the slurry waste liquid at a high recovery rate, whereby the supply amount of the new coolant 29 can be reduced as much as possible.

  As described above, the removal of the secondary regenerative coolant 16 by the filter 15 and the separation of the sludge 25 by the secondary centrifuge 24 are performed in parallel under conditions suitable for each, whereby 2 by the filter 15 is obtained. When the removal amount of the secondary regeneration coolant 16 increases, the removal amount of the sludge 25 of the centrifuge increases, and when the removal amount of the secondary regeneration coolant 16 and the removal amount of the sludge 25 are balanced, the filter 15 And the amount of solid matter in the slurry circulating between the secondary centrifuge 24 is constant. This eliminates the need for a tank as a buffer for lowering the filtration rate required in the conventional batch method, and enables continuous treatment of the slurry waste liquid 3.

  Furthermore, it is known that in a slurry waste liquid using an aqueous coolant, silicon chips and water react and aggregate. In this principle, fine particles having a large surface area per volume aggregate preferentially. Since the chips whose apparent particle diameter has become larger are preferentially removed by the secondary centrifuge 24, the light liquid 13 with reduced fine particles is supplied to the filter 15 and effectively separated. . Therefore, it is effective to provide the water-based coolant in combination with the filter 15 and the secondary centrifuge 24 as described above.

  It should be noted that the present invention is not limited to the above-described embodiments, and it is needless to say that various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Fixed abrasive wire saw 3 Slurry waste liquid 3a Part 3b Remaining part 5 Slurry waste liquid storage tank 6 Primary centrifuge 7 Primary centrifuge 8 Sludge 9 Primary regeneration coolant 12 Coolant supply tank 13 Light liquid 14 Light liquid tank 15 Filtration 16 Secondary regeneration coolant 18 Concentrated liquid 19 Cyclone separator 20 Light liquid 21 Heavy liquid 22 Heavy liquid tank 23 Secondary centrifuge 24 Secondary centrifuge 25 Sludge 26 Light liquid 29 New coolant

Claims (2)

  Slurry waste liquid storage tank for storing the slurry waste liquid from the fixed abrasive wire saw, and a primary centrifugal separator for taking out the primary regeneration coolant obtained by introducing a part of the slurry waste liquid in the slurry waste liquid storage tank and separating the sludge A light liquid tank that takes in the remainder of the slurry waste liquid from the slurry waste liquid storage tank as a light liquid, a filter that introduces the light liquid in the light liquid tank and separates and removes the secondary regeneration coolant, and a filter A cyclone separator that introduces the concentrated liquid from which the secondary regeneration coolant has been separated to separate the light liquid and returns the separated light liquid to the light liquid tank, and a heavy liquid from which the light liquid has been separated by the cyclone separator are stored. A wire source slurry coolant comprising: a heavy liquid tank; and a secondary centrifuge for returning the light liquid obtained by introducing the heavy liquid in the heavy liquid tank and separating sludge into the light liquid tank. Recovery device.   A coolant supply tank that mixes and adjusts a primary regeneration coolant from the primary centrifugal separator, a secondary regeneration coolant from the filter, and a new coolant, and supplies the adjusted coolant to the fixed abrasive wire saw. The wire source slurry coolant recovery device according to claim 1.

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