CN105384173B

CN105384173B - Method and apparatus for recovering silicon powder

Info

Publication number: CN105384173B
Application number: CN201510542262.5A
Authority: CN
Inventors: 藤田敦史; 吉田干; 内田正喜
Original assignee: Disco Corp
Current assignee: Disco Corp
Priority date: 2014-09-01
Filing date: 2015-08-28
Publication date: 2022-05-03
Anticipated expiration: 2035-08-28
Also published as: TWI669273B; CN105384173A; JP2016049506A; JP6448955B2; TW201609564A

Abstract

Provided are a method and an apparatus for recovering silicon powder, which can effectively recover silicon powder from which moisture has been removed. A waste liquid (L) containing silicon powder (P) discharged from a processing device (100) for processing by bringing a grindstone (103d) into contact with a silicon wafer (S) is brought into contact with the silicon adsorption plate (32) and the silicon via a restriction plate (33d), and the silicon powder is attached to the positively charged silicon adsorption plate by energizing the waste liquid (L). Next, the silicon adsorption plate is lifted up from the waste liquid, and a silicon Solution (SF) containing the silicon powder adhered to the silicon adsorption plate and the waste liquid is scraped off from the silicon adsorption plate and recovered. Then, the moisture of the silicon solution scraped off from the silicon adsorption plate is dried by a drying unit (6).

Description

Method and apparatus for recovering silicon powder

Technical Field

The present invention relates to a method and an apparatus for recovering silicon powder, and more particularly to a method and an apparatus for recovering silicon powder, which can recover silicon powder from waste liquid discharged from scraping solid silicon.

Background

Conventionally, in secondary batteries such as lithium ion batteries, a carbon-based material has been used as a material for a negative electrode. On the other hand, attention is paid to the case where silicon is used as a material of a negative electrode in order to enable rapid charging or rapid discharging of a lithium ion battery or to cope with an increase in capacity. When silicon is used, the storage capacity is expected to be several times higher than that of a carbon-based material, and for this reason, it is important to make silicon into a fine powder.

As a technique for recovering such fine powder silicon (silicon powder), a method of separating silicon powder from a waste liquid containing silicon powder discharged from a processing apparatus has been proposed (for example, see patent document 1). In this method, a positively charged silicon adsorption plate is disposed in a liquid tank in which waste liquid containing silicon powder is stored, and the negatively charged silicon powder is adsorbed. The silicon powder adsorbed by the silicon adsorption plate is scraped off by a scraper, and the silicon powder is recovered.

Patent document 1: japanese patent laid-open publication No. 2013-119050

Disclosure of Invention

However, in the method described in patent document 1, it is difficult to completely remove moisture caused by the waste liquid containing silicon powder. On the other hand, it is necessary to remove moisture caused by such waste liquid from the silicon powder reused for the use of the material of the negative electrode and the like.

The present invention has been made in view of the above problems, and an object thereof is to provide a method and an apparatus for recovering silicon powder, which can efficiently recover moisture-removed silicon powder.

The method for recovering silicon powder according to the present invention is a method for recovering silicon powder by grinding solid silicon using a processing liquid and abrasive grains, recovering a waste liquid containing silicon powder discharged, removing moisture from the waste liquid, and recovering silicon powder, the method comprising the steps of: an adhesion step of bringing the anode section and the cathode section into contact with the waste liquid, and energizing the anode section and the cathode section to adhere the silicon powder to the positively charged anode section; a recovery step of lifting the anode portion from the waste liquid and scraping the silicon solution containing the silicon powder and the waste liquid adhering to the anode portion from the anode portion; and a drying step of drying the moisture of the silicon solution scraped off from the anode portion in the recovery step by a drying means.

According to this configuration, since the moisture of the silicon solution scraped off from the anode portion is dried by the drying means, the moisture contained in the silicon solution can be evaporated. This makes it possible to remove water from the silicon solution containing the silicon powder and the waste liquid, and to efficiently recover the silicon powder from which water has been removed.

Further, a silicon powder recovery apparatus according to the present invention recovers silicon powder from a waste liquid containing silicon powder discharged from a processing apparatus that processes a silicon wafer by bringing a grindstone into contact with the silicon wafer, the silicon powder recovery apparatus including: an anode section and a cathode section which are brought into contact with a waste liquid discharged from the processing apparatus; a scraping unit that scrapes the silicon solution attached to the anode portion from the anode portion, the silicon solution including the silicon powder and the waste liquid; a drying unit that dries the silicon solution scraped by the scraping unit; and a collection box that collects the silicon powder dried by the drying unit.

According to this configuration, since the moisture of the silicon solution scraped off from the anode portion is dried by the drying means, the moisture contained in the silicon solution can be evaporated. Thus, moisture can be removed from the silicon solution containing the silicon powder and the waste liquid, and the silicon powder from which the moisture has been removed can be efficiently collected in the collection box.

According to the present invention, the silicon powder from which moisture has been removed can be efficiently recovered.

Drawings

Fig. 1 is a schematic perspective view of a silicon powder recovery apparatus according to the present embodiment.

Fig. 2 is a sectional view taken along line a-a of fig. 1.

Fig. 3 is a schematic cross-sectional view of the silicon powder recovery apparatus according to the present embodiment.

Fig. 4A and 4B are schematic views of the scraping unit included in the silicon powder recovery apparatus according to the present embodiment.

Fig. 5 is a schematic view of a drying unit provided in the silicon powder recovery apparatus according to the present embodiment.

Description of the reference symbols

1: a silicon powder recovery device (recovery device); 3: a separation processing unit; 31: a liquid bath; 32: a silicon adsorption plate; 33: a silicon passing restriction section; 33 d: a silicon pass confinement plate; 4: a recovery unit; 41: a recovery unit; 44: a scraping unit; 44 a: opening and closing the air cylinder; 44 b: scraping a plate; 6: a drying unit; 62. 63: a conveying roller; 64: a conveyor belt; 66: a heater section; 7: a collection box; 8: a control unit; 100: a machining device (grinding device); 103 d: grinding stone; l: waste liquor; p: silicon powder; s: a silicon wafer; SF: a silicon solution; w: and (5) purifying water.

Detailed Description

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The silicon powder recovery apparatus of the present invention recovers silicon powder from a waste liquid containing silicon powder discharged from a processing apparatus that processes a silicon wafer by bringing a grindstone into contact with the silicon wafer. Hereinafter, a grinding apparatus for grinding a silicon wafer will be described as an example of a processing apparatus for supplying a waste liquid containing silicon powder to the silicon powder recovery apparatus of the present invention. However, the processing apparatus for supplying the waste liquid containing the silicon powder is not limited thereto, and may be appropriately changed.

Fig. 1 is a schematic perspective view of a silicon powder recovery apparatus according to the present embodiment. Fig. 2 is a sectional view taken along line a-a of fig. 1. Fig. 3 is a schematic cross-sectional view of the silicon powder recovery apparatus according to the present embodiment. Fig. 1 shows a state where a collection box 7, which will be described later, is drawn out from the silicon powder collection apparatus for convenience of explanation. Fig. 3 shows a part of a processing apparatus for supplying waste liquid containing silicon powder to the silicon powder recovery apparatus of the present embodiment, and also shows a main part of the silicon powder recovery apparatus.

As shown in fig. 1, a silicon powder recovery apparatus (hereinafter, simply referred to as "recovery apparatus") 1 of the present embodiment includes a waste liquid storage box 2, a separation processing unit 3, a recovery unit 4, a purified water storage box 5, a drying unit 6, a collection box 7, and a control unit 8. The recovery apparatus 1 of the present embodiment having such a configuration recovers the silicon powder P from the waste liquid L containing the silicon powder P discharged from the processing apparatus (grinding apparatus) 100 that processes the silicon wafer S by bringing the grinding stone 103d into contact therewith (see fig. 3).

The waste liquid storage tank 2 is a container for storing the waste liquid L. The waste liquid storage tank 2 is disposed on the bottom of the housing 10 of the recovery device 1 and on the side of a liquid tank 31 of a separation processing unit 3 described later. As described above, the waste liquid L containing the silicon powder P is supplied from the grinding apparatus 100 for grinding the silicon wafer S into the waste liquid storage box 2.

Here, a configuration example of the grinding apparatus 100 for supplying the waste liquid L to the waste liquid storage tank 2 will be described with reference to fig. 3. As shown in fig. 3, the grinding apparatus 100 includes a chuck table 102 provided on an upper portion of a base 101, and a grinding unit 103 configured to grind a silicon wafer S held by the chuck table 102.

The chuck table 102 has a substantially disk shape, and is provided to be rotatable about a disk center as an axis by a chuck rotation unit not shown. A holding surface 102a for holding the silicon wafer S by suction is provided on the upper surface of the chuck table 102. The holding surface 102a is made of, for example, a porous ceramic material, and the porous ceramic material is connected to a suction source (not shown). The chuck table 102 is supported by a table support 104. The table support 104 is disposed in an opening 101a formed in the upper surface of the base 101.

In the grinding unit 103, a wheel base 103b is provided at the lower end of a cylindrical spindle 103a, and a grinding wheel 103c is attached to the lower surface of the wheel base 103 b. The main shaft 103a is fixed to an output shaft of a drive motor, not shown. Therefore, the grinding wheel 103c is rotated via the spindle 103a by the driving of the driving motor.

The grinding wheel 103c is configured such that a plurality of grinding stones 103d are arranged in a ring shape on the lower surface of the wheel base. The grinding wheel 103d is made of, for example, a ceramic bonded grinding wheel, and rotates at a high speed around the Z axis in accordance with the driving of the main shaft 103 a. The lower surface of the grinding wheel 103d serves as a grinding surface and is rotated while being in contact with the silicon wafer S, and the silicon wafer S is ground by the contact to generate fine-particle silicon powder P.

The grinding unit 103 has a nozzle, not shown, and supplies the processing liquid from the nozzle to the silicon wafer S held by the chuck table 102 when the silicon wafer S is ground by the grinding wheel 103 d. During the grinding process, the silicon powder P is mixed into the supplied processing liquid. The processing liquid containing the silicon powder P becomes a waste liquid L.

The waste liquid L flows into and is stored in a water tank 105 disposed inside the base 101. The tank 105 has a drain opening 105a at the bottom for discharging the stored waste liquid L. The water tank 105 is illustrated in 2 positions on the left and right in fig. 3, but is also formed on both sides in the vertical direction of the paper plane in fig. 3, and is formed in a rectangular frame shape in a plan view, and has an integrated storage space.

The discharge port 105a communicates with the supply port 21 of the waste liquid storage tank 2 via a transfer pipe 105 b. Thereby, the waste liquid L in the water tank 105 flows into the waste liquid storage tank 2 and is stored therein.

The waste liquid storage box 2 includes a waste liquid pump 22 that sends out the waste liquid L inside to a liquid tank 31 of a separation processing unit 3 described later. The liquid tank 31 is provided with an inlet 31a, and the inlet 31a is connected to a discharge port of the waste liquid pump 22 via a transfer pipe 23. The waste liquid pump 22 conveys the waste liquid containing the silicon powder P into the liquid tank 31 via the conveying pipe 23.

The separation processing unit 3 separates the waste liquid L supplied from the waste liquid pump 22 into the silicon powder P and the purified water W not containing the silicon powder P. As shown in fig. 1 and 2, the separation processing unit 3 includes a liquid tank 31, a plurality of silicon adsorption plates 32, and a plurality of silicon passage restricting portions 33.

The liquid tank 31 is a rectangular parallelepiped container with an open upper part, and stores the waste liquid L supplied from the waste liquid pump 22. The liquid tank 31 is provided on the bottom of the housing 10 so that the waste liquid storage box 2 is positioned on the side. The transport pipe 23 is connected to the liquid tank 31 (see fig. 3). A drain pipe, not shown, is provided above the liquid tank 31 to prevent the waste liquid L from overflowing. The drain pipe is connected to the waste liquid storage box 2, and guides the waste liquid L overflowing from the liquid tank 31 to the waste liquid storage box 2 again.

The silicon adsorption plate 32 constitutes an anode portion, is made of a material having high electrochemical properties, and is formed in a flat plate shape having a rectangular planar shape. For example, the silicon adsorption plate 32 may be made of a material such as copper (Cu), silver (Ag), platinum (Pt), or gold (Au). In this embodiment, stainless steel (SUS316, SUS304, or the like) is used.

A plurality of silicon adsorption plates 32 are disposed at equal intervals in the liquid tank 31. The silicon adsorption plates 32 are arranged with a surface perpendicular to the longitudinal direction of the liquid bath 31, in other words, parallel to the width direction of the liquid bath 31, with a gap therebetween. The silicon suction plate 32 is provided with two engaged pieces 32a projecting upward from the center portion in the width direction with a gap therebetween. The engaged piece 32a is formed in a rectangular plate shape, and an engaged hole 32b penetrating along the surface of the silicon adsorption plate 32 is provided at the center of the engaged piece 32 a. The protruding pin 423e of the suction plate moving portion 42 described later of the recovery unit 4 enters the engaged hole 32b and engages therewith.

The silicon passage restricting portions 33 are provided between the silicon adsorption plates 32 adjacent to each other. The silicon passage restricting portions 33 face the silicon adsorption plate 32, and a plurality of silicon passage restricting portions are alternately arranged so as to be separated from the silicon adsorption plate 32. The silicon is arranged in the liquid tank 31 at equal intervals by the regulating section 33, and is arranged in parallel with the silicon adsorption plate 32.

As shown in fig. 2, the silicon passage restricting section 33 includes a frame 33a and a discharge section 33 b. The frame 33a includes: a rectangular frame 33 c; and a pair of silicon pass-through regulating plates 33d arranged in parallel with each other at a spacing so as to close the opening surfaces on both sides of the frame 33 c. That is, the frame 33a is composed of a frame 33c and a pair of silicon-passing regulation plates 33 d.

The silicon passage regulating plate 33d constitutes a cathode portion, is made of a material having high electrochemical properties, and is formed in a flat plate shape having a rectangular planar shape, as in the silicon adsorbing plate 32. For example, the silicon pass-through restriction plate 33d is made of a material such as copper (Cu), silver (Ag), platinum (Pt), or gold (Au). In this embodiment, stainless steel (SUS316, SUS304, or the like) is used.

In the present embodiment, a dc voltage is applied between the silicon adsorption plate 32 and the silicon passage limiting plate 33d (see fig. 2). That is, the positive (+) side of the direct current power supply DC is electrically connected to the silicon adsorption plate 32, and the silicon adsorption plate 32 is positively charged in the waste liquid L. The silicon adsorption plate 32 is positively charged in the waste liquid L, and is used to adsorb the silicon powder P negatively charged in the waste liquid L. On the other hand, the minus (-) side of the direct current power supply DC is electrically connected to the silicon passage limiting plate 33d, and the silicon passage limiting plate 33d is negatively charged in the waste liquid L.

The silicon is formed in a mesh shape by the restriction plate 33 d. The openings of the meshes of the silicon passing restriction plate 33d are formed sufficiently larger than the silicon powder P. The silicon passage-regulating plate 33d does not have a function of catching the silicon powder P by a mesh, and the mesh size thereof may be set to the following degree: the silicon powder P is negatively charged to generate a repulsive force. By negatively charging the silicon by the restriction plate 33d, only the pure water (water) W as the liquid of the waste liquid L is allowed to pass, and the passage of the silicon powder P is restricted by generating a repulsive force with the negatively charged silicon powder P. The frame 33a is formed of a frame 33c and a pair of silicon passage restricting plates 33d, and forms a region in which the purified water W having passed through the silicon passage restricting plates 33d is present on the inside, and a repulsive force is generated between the silicon passage restricting plates 33d and the silicon powder P, thereby partitioning the region in which the purified water W is present from the waste liquid L in the liquid tank 31.

The discharge portion 33b is provided in each housing 33a, and discharges the purified water W disposed in the housing 33a to the purified water storage tank 5. The discharge portion 33b includes a delivery pipe 33e disposed in the housing 33a and an opening/closing valve 33f connected to the delivery pipe 33 e. The delivery pipe 33e is connected to both the housing 33a and the purified water storage tank 5. The delivery pipe 33e is provided upright from the center of the upper portion of the frame 33c, is bent horizontally upward of the purified water storage tank 5, is bent downward of the purified water storage tank 5, and is connected to a supply port 51 of the purified water storage tank 5, which will be described later. The delivery pipe 33e delivers the purified water W passed through the silicon passage restricting plate 33d from the inside of each housing 33a to the purified water storage tank 5. The opening/closing valve 33f is provided in the flow path of the delivery pipe 33e, and forms the flow path in the delivery pipe 33e so as to be openable and closable.

The recovery unit 4 recovers the silicon powder P separated by the separation processing unit 3. As shown in fig. 1, the recovery unit 4 includes: a recovery unit 41 that recovers silicon powder P (more specifically, a silicon solution SF containing silicon powder P (see fig. 4)) from the silicon adsorption plate 32; and an adsorption plate moving unit 42 for moving the silicon adsorption plate 32 from the liquid tank 31 of the separation unit 3 to the recovery unit 41.

As shown in fig. 1, the recovery unit 41 is disposed outside one end of the liquid tank 31 of the separation processing unit 3. The recovery unit 41 includes: a box-shaped collection container 43 having a lower opening, and a scraping unit 44 (not shown in fig. 1, see fig. 4) provided in the collection container 43.

The adsorption plate moving unit 42 is provided above the liquid tank 31 of the separation processing unit 3. As shown in fig. 1, the suction plate moving section 42 includes: a horizontal moving unit 42a, a vertical plate 42b, an elevating unit 42c, an elevating plate 42d, and a suction plate supporting unit 42 e.

The horizontal movement unit 42a is a unit that moves the silicon adsorption plate 32 above the liquid bath 31 along the longitudinal direction of the liquid bath 31. The horizontal movement unit 42a has: a horizontal ball screw 421a, a horizontal movement motor not shown, and a pair of horizontal movement guide rails 422 a. The horizontal ball screw 421a is provided parallel to the longitudinal direction of the liquid tank 31, and is supported on the upper portion of the housing 10 so as to be rotatable about the axis. The horizontal ball screw 421a is formed longer than the liquid tank 31, and is provided in a range from above the other end portion of the liquid tank 31 on the side away from the recovery portion 41 to above the recovery portion 41. A nut 421b attached to the vertical plate 42b is screwed to the horizontal ball screw 421 a.

The horizontal movement motor is provided in the apparatus main body or the like, and rotationally drives the horizontal ball screw 421a around the axis. A pair of horizontal translation guide rails 422a are disposed in parallel with the horizontal ball screw 421a on the upper portion of the housing 10, and a slide block 422b fixed to the vertical plate 42b is slidably attached. The pair of horizontal-movement guide rails 422a are formed longer than the liquid tank 31 and are provided in a range from above the other end portion of the liquid tank 31 to above the collection unit 41. The horizontal movement unit 42a rotationally drives the horizontal ball screw 421a by a horizontal movement motor, and the silicon adsorption plate 32 engaged with the vertical plate 42b (adsorption plate support unit 42e) is guided by the pair of horizontal movement guide rails 422a and moved along the longitudinal direction of the liquid tank 31.

Both surfaces of the vertical plate 42b are provided in parallel to both the vertical direction and the width direction of the liquid tank 31. The vertical plate 42b is fixed with a nut 421b and a slide block 422b, and is configured to be movable along a guide rail 422a for horizontal movement.

The lifting unit 42c is a unit for lifting the silicon adsorption plate 32 from the liquid bath 31 or inserting the silicon adsorption plate 32 into the liquid bath 31 to lift the silicon adsorption plate 32. The lifting unit 42c includes a vertical ball screw 421c, a lifting motor not shown, and a pair of lifting guide rails 422 c. The vertical ball screw 421c is provided parallel to the vertical direction and is supported on the surface of the vertical plate 42b so as to be rotatable about the axis. The vertical ball screw 421c is formed to be longer than the height of the silicon suction plate 32 and is provided in the range of the entire length of the vertical plate 42 b. A nut, not shown, attached to the elevating plate 42d is screwed to the vertical ball screw 421 c.

The lifting motor is provided on the vertical plate 42b or the like and rotationally drives the vertical ball screw 421c around the axial center. The pair of guide rails 422c for lifting and lowering are disposed on the surface of the vertical plate 42b in parallel with the vertical ball screw 421c, and slidably support the lifting and lowering plate 42 d. The pair of elevating guide rails 422c are formed to have a length substantially equal to the height of the silicon suction plate 32, and are provided over the entire length of the vertical plate 42 b. The lifting unit 42c drives the vertical ball screw 421c to rotate by a lifting motor, and thereby guides and moves up and down the silicon adsorption plate 32 engaged with the lifting plate 42d (adsorption plate support unit 42e) by the pair of guide rails 422 c.

The lifting plate 42d is formed in a band plate shape parallel to the width direction of the liquid tank 31, and is disposed on the surface of the free end side of the vertical plate 42 b. A nut and a slide block, not shown, are fixed to the lifting plate 42d, and are provided to be movable along the lifting guide rail 422 c.

The suction plate supporting unit 42e has a pair of chuck cylinders 421 e. The pair of chuck cylinders 421e are disposed at intervals in the width direction of the liquid tank 31. The chuck cylinder 421e has: a cylinder body 422e attached to the lifting plate 42d, and a projecting pin 423e provided to be extendable and retractable from the cylinder body 422 e. The chuck cylinder 421e is attached to the lower surface of the elevation plate 42d in a state where the projected and retracted pins 423e projected from the cylinder body 422e are close to each other. The protruding pin 423e is formed in a cylindrical shape parallel to the width direction of the liquid tank 31. The projecting pin 423e extends and contracts from the cylinder main body 422e in the range of the position shown by the broken line and the position shown by the solid line in fig. 1. When the projecting pin 423e projects from the cylinder main body 422e in a state where the lifting plate 42d is lowered by the lifting unit 42c, the projecting pin 423e enters the engaged hole 32b of the silicon suction plate 32 and engages therewith.

The recovery container 43 has a slit 43a on the upper surface through which the silicon adsorption plate 32 can pass. A side surface (a side surface on the lower right side in fig. 1) of the collection container 43 is provided with a nitrogen gas (N) for blowing the nitrogen gas into the collection container 43₂) And the blowing port 43b is used. Nitrogen gas was blown into the space in the recovery vessel 43 to deoxidize the space. By bringing the recovery container 43 into the deoxidation state, the formation of an oxide film on the surface of the silicon powder P in the silicon solution SF described later can be suppressed.

The scraping unit 44 is disposed near the slit 43a in the collection container 43. Fig. 4 is a schematic view of the scraping unit 44 included in the recovery apparatus 1 according to the present embodiment. Fig. 4 shows the silicon adsorption plate 32 of the separation processing unit 3 and the lifting unit 42c for lifting and lowering the silicon adsorption plate 32. Fig. 4A shows the scraping unit 44 in a state before the silicon powder P adsorbed by the silicon adsorption plate 32 (more specifically, the silicon solution SF containing the silicon powder P and the waste liquid) is scraped, and fig. 4B shows the scraping unit 44 in a state after the silicon solution SF adsorbed by the silicon adsorption plate 32 is scraped.

As shown in fig. 4, the scraping unit 44 is disposed in the support plate portion 43c, and the support plate portion 43c is disposed in the collection container 43. The support plate portion 43c extends from the inner side surface of the collection container 43 in parallel with the upper surface of the collection container 43. A slit 43d is formed in the support plate portion 43c at a position corresponding to the slit 43 a. The scraping unit 44 includes: a pair of opening/closing cylinders 44a disposed on the support plate portion 43 c; and a pair of scraping plates 44b extending from the opening/closing cylinder 44a toward the inside of the collection container 43.

The pair of opening/closing cylinders 44a are provided on the support plate sections 43c facing each other with the slit 43d interposed therebetween. The scraping plate 44b extends from the side surface of the opening/closing cylinder 44a on the slit 43 side toward the opening/closing cylinder 44a on the target side. The scraping plate 44b is formed in a band plate shape extending parallel to the width direction of the liquid tank 31. The length of the scraping plate 44b is formed to be slightly longer than the width of the silicon adsorption plate 32. The opening/closing cylinder 44a is connected to a drive motor, not shown. The scraping plate 44b is configured to be able to retreat on the slit 43d in accordance with the driving state of the opening/closing cylinder 44 a.

Since the scraping unit 44 has such a structure, the surface of the silicon adsorption plate 32 stored in the recovery container 43 can be sandwiched by the scraping plate 44 b. The lifting unit 42c of the recovery unit 4 lifts the silicon adsorption plate 32 while sandwiching the surface of the silicon adsorption plate 32, and the scraping unit 44 scrapes the silicon powder P (more specifically, the silicon solution SF containing the silicon powder P and the waste liquid) adsorbed by the silicon adsorption plate 32 (see fig. 4B).

The purified water storage tank 5 is a container for storing the purified water W not containing the silicon powder P separated from the waste liquid L by the separation processing unit 3. As shown in fig. 1, the purified water storage tank 5 is stacked on the waste liquid storage tank 2 and is disposed on the side of the liquid tank 31 of the separation treatment unit 3. The purified water W disposed in the housing 33a of the silicon passage regulating unit 33 is delivered to the supply port 51 via the delivery pipe 33e and stored in the purified water storage tank 5.

The drying unit 6 is disposed below the recovery container 43 of the recovery unit 4. The drying unit 6 performs a function of evaporating and removing moisture from the silicon solution SF recovered by the recovery unit 41 of the recovery unit 4. The drying unit 6 has: a drying box 61, a pair of conveying

rollers

62 and 63, a conveying belt 64, a drive motor 65, and a heater portion 66 (see fig. 3 and 5). Hereinafter, the structure of the drying unit 6 will be described with reference to fig. 3 and 5. Fig. 5 is a schematic diagram of the drying unit 6 included in the recovery device 1 according to the present embodiment. In addition, in fig. 5, the drying cassette 61 is omitted for convenience of explanation, and the silicon solution SF and the collection cassette 7 are illustrated.

The drying box 61 has a substantially rectangular parallelepiped shape, and a part of the upper surface and the lower surface thereof is opened. That is, in the drying box 61, an opening 61a is formed at a position corresponding to the scraping unit 44 on the upper surface, and an opening 61b is formed at a position corresponding to the collecting box 7 on the lower surface (see fig. 3). The space inside the drying box 61 also accommodates components of the drying unit 6 other than the drying box 61.

The pair of conveying

rollers

62 and 63 are disposed in the drying box 61 in a state of having a slight difference in height and separated in the Y axis direction as shown in fig. 3. More specifically, the conveying roller 62 is disposed near an end on the liquid tank 31 side, and the conveying roller 63 is disposed near an end on the opposite side in the drying cartridge 61 at a position lower than the conveying roller 62. These conveying

rollers

62, 63 are arranged to extend in a direction (X-axis direction shown in fig. 3) parallel to the width direction of the liquid tank 31. These conveying

rollers

62, 63 have a length slightly longer than the width of the silicon adsorption plate 32.

The conveyor belt 64 is an endless belt wound around the

conveyor rollers

62 and 63. The conveyor belt 64 has a width slightly longer than the width of the silicon suction plate 32, similarly to the

conveyor rollers

62 and 63. The conveyor belt 64 is made of a resin belt such as teflon (registered trademark), for example. By using the conveyor belt 64 made of resin in this way, the silicon powder P can be easily peeled off from the surface of the conveyor belt 64. In consideration of durability, thermal conductivity, and peelability of the silicon powder P, the following conveyor belt 64 is preferably used as an embodiment: the core material is made of a metal such as copper, and a teflon sheet is used for the surface on which the silicon solution SF is placed. Alternatively, the conveyor belt 64 may be formed by coating a metal belt with teflon.

The drive motor 65 is connected to the transport roller 62 and supplies a driving force. The conveying roller 62 receives a driving force from a driving motor 65 and rotates in the arrow a direction shown in fig. 5. Similarly, the conveying roller 63 receives a driving force from the conveying roller 62 via the conveying belt 64 and rotates in the arrow B direction shown in fig. 5. The conveyor belt 64 rotates in the direction of arrow C shown in fig. 5 in accordance with the rotation of the

conveyor rollers

62 and 63.

The heater portion 66 is disposed between the conveying

rollers

62 and 63 and near the back surface (lower surface) of the conveying belt 64 disposed on the upper side. The heater portion 66 performs a function of heating the silicon solution SF transported on the transport belt 64. The heater portion 66 is, for example, a resistance heating system that generates heat by resistance, but is not limited thereto. On the premise that the silicon solution SF on the conveyor belt 64 is heated, any heating method can be adopted. The position of the heater portion 66 with respect to the conveyor belt 64 may be changed as appropriate.

The collecting box 7 is disposed below the drying device 6. The collecting box 7 has a box shape with an upper opening. The collection box 7 is disposed with its upper opening facing the conveying roller 63 of the drying unit 6, and stores the silicon powder P conveyed by the conveying belt 64. As shown in fig. 1, the collection box 7 can be pulled out from the frame 10 of the recovery device 1, and the stored silicon powder P can be easily taken out. Further, the collection container 43, the drying box 61, and the collection box 7 are made to be in a nitrogen atmosphere by the nitrogen gas blown from the blowing port 43b, whereby the natural oxide film can be prevented from adhering to the surface of the silicon powder P.

The control unit 8 controls the components of the recovery apparatus 1. The control unit 8 includes a processor for executing various processes and a storage medium such as ROM and RAM. For example, the control unit 8 controls the driving of the suction plate moving unit 42, the scraping unit 44, and the drying unit 6 of the collection unit 4.

Next, a method for recovering the silicon powder P using the recovery apparatus 1 of the present embodiment will be described. First, as shown in fig. 3, the following states are achieved: after the silicon wafer S is held by suction by the holding surface 102a of the chuck table 102, the table support 104 is driven to position the chuck table 102 at a grinding position where the silicon wafer S faces the grinding wheel 28. From this state, the grinding unit 103 is lowered while rotating the grinding wheel 102 d. Then, the silicon wafer S is supplied with the processing liquid from a nozzle not shown, and the grinding is performed by bringing the grinding wheel 103d into contact with the silicon wafer S. The silicon wafer S is ground by the grinding process to form fine powdery silicon powder P, and the silicon powder P is mixed into the processing liquid to generate a waste liquid L. The generated waste liquid L flows into the water tank 105 through the opening 101a, and then is stored in the liquid tank 31 through the waste liquid storage box 2.

In the state where the waste liquid L is stored in the liquid tank 31 as described above, in the method for recovering silicon powder according to the present embodiment, first, an adhesion step is performed to adhere the silicon powder P to the silicon adsorption plate 32 from the waste liquid L stored in the liquid tank 31. In this adhesion step, the waste liquid L is brought into contact with the silicon adsorption plate 32 and the silicon passage limiting plate 33d, and the positive (+) of the DC power supply DC is applied to the silicon adsorption plate 32, while the negative (-) of the DC power supply DC is applied to the silicon passage limiting plate 33 d. When the electricity is applied in this manner, the silicon powder P mixed in the waste liquid L and charged negatively (-) is repelled from the negatively (-) charged silicon by the electrophoresis through the restriction plate 33d, and is adsorbed by the positively (+) charged silicon adsorption plate 32 (see fig. 2).

Next, a recovery step is performed to recover the silicon solution SF containing the silicon powder P and the waste liquid L adhering to the silicon adsorption plate 32 by the recovery unit 4. In this recovery step, the silicon adsorption plate 32 is lifted from the waste liquid L by the adsorption plate moving section 42 of the recovery unit 4 and moved to above the recovery container 43 of the recovery section 41. Then, the silicon adsorption plate 32 is inserted into the collection container 43 through the slit 43a on the upper surface (see fig. 4A). Then, the opening/closing cylinder 44a of the scraping unit 44 drives the scraping plate 44b to sandwich the cylinder suction plate 32. From this state, the cylinder suction plate 32 is lifted by the suction plate moving section 42 (lifting unit 42c) (see fig. 4B). Thereby, the silicon solution SF is scraped off and recovered from the silicon adsorption plate 32.

Next, a drying step is performed to dry the moisture of the silicon solution SF scraped off from the silicon adsorption plate 32 by the drying unit 6. In this drying step, the silicon solution SF scraped by the scraping unit 44 is moved by the drying unit 6 (more specifically, the conveyor belt 64) disposed below. The silicon solution SF is conveyed by rotating the conveyor belt 64 by the drive motor 65, and the water content of the silicon solution SF is evaporated by heating by the heater portion 66. Thereby, moisture in the silicon solution SF composed of the silicon powder P and the waste liquid L is removed.

In this way, moisture is removed from the silicon solution SF by the heater portion 66, whereby only the silicon powder P remains on the conveyor belt 64. When the silicon powder P on the conveyor belt 64 is conveyed beyond the conveying roller 63, it falls into the collection box 7. This allows the silicon powder P from which moisture has been removed to be extracted in the collection box 7.

As described above, according to the present embodiment, the moisture of the silicon solution SF scraped off from the silicon adsorption plate 32 by the scraping unit 44 can be evaporated by the drying unit 6, and the silicon powder P from which the moisture has been removed can be efficiently recovered.

In particular, according to the present embodiment, the moisture of the silicon solution SF including the silicon powder P and the waste liquid L is dried by heating with the heater portion 66 provided in the drying unit 6, and therefore the moisture included in the silicon solution SF can be effectively removed. Thus, the moisture can be removed more effectively than in the case where the recovered silicon powder P is dried by blowing nitrogen gas or the like, and the silicon powder P from which the moisture has been removed can be recovered more effectively.

In the present embodiment, the silicon powder P in a state of being dehydrated and dried is collected in the collection box 7. Therefore, oxidation of the silicon powder P, which is the case where water is contained in the silicon powder P, is prevented, and generation of hydrogen can be prevented. As a result, the silicon powder P can be safely handled.

In the present embodiment, moisture is removed from the silicon solution SF by heating the heater portion 66 while the silicon solution SF is conveyed on the conveyor belt 64. Therefore, the silicon powder P dried by removing moisture remains as lumps on the conveyor belt 64. Thus, when the sheet is conveyed on the conveying belt 64 beyond the conveying roller 63, the sheet is likely to fall onto the collecting box 7. As a result, the collecting operation of the collecting cassette 7 can be made efficient.

Further, according to the present embodiment, since electrophoresis is used for extraction of silicon powder P, silicon powder P having a uniform particle diameter can be easily extracted. Further, since the silicon powder P is formed by grinding with the grinding stone 103d, the particle diameter of the silicon powder P can be easily reduced by reducing the abrasive grains. Thus, the silicon powder P of the present embodiment is used for the negative electrode of the lithium ion battery, and can contribute to rapid charge and rapid discharge of the lithium ion battery and a large capacity of electric storage.

The present invention is not limited to the above-described embodiments, and various modifications can be made. In the above-described embodiments, the size, shape, and the like shown in the drawings are not limited thereto, and may be appropriately modified within a range in which the effects of the present invention are exhibited. In addition, the present invention can be modified as appropriate without departing from the scope of the present invention.

For example, in the above embodiment, the drying unit 6 including the drying cartridge 61, the conveying

rollers

62 and 63, the conveying belt 64, the driving motor 65, and the heater portion 66 as the constituent elements is described. However, the structure of the drying unit 6 is not limited thereto, and may be appropriately modified. On the premise of having the heater section 66, the drying unit 6 having any structural member can be applied.

In the above embodiment, the heater portion 66 is provided to dry the moisture of the silicon solution SF on the conveyor belt 64. However, the structure of the drying unit 6 is not limited thereto, and may be appropriately modified. For example, the drying unit 6 may be configured to vibrate the conveyor belt 64 to dry the silicon solution SF placed on the conveyor belt 64 by contacting the gas in the drying box 61. In this case, drying can be performed without the heater section 66, but the surface of the silicon solution SF is easily dried and the inside is hardly dried. From the viewpoint of drying the silicon powder P, the drying unit 6 having the heater portion 66 as in the above embodiment is preferable.

Industrial applicability

As described above, the present invention can efficiently collect the silicon powder from which moisture has been removed, and is useful for a silicon powder collection method and a silicon powder collection apparatus for collecting waste liquid containing silicon powder formed by grinding a silicon wafer and collecting the silicon powder from the waste liquid.

Claims

1. A silicon powder recovery device for recovering silicon powder from a waste liquid containing silicon powder discharged from a processing device for processing a silicon wafer by bringing a grindstone into contact with the silicon wafer and stored in a liquid tank,

the silicon powder recovery device comprises:

an anode section and a cathode section which are brought into contact with the waste liquid discharged from the processing apparatus;

a recovery unit including a recovery container having a lower opening, a first slit provided in an upper surface of the recovery container and through which the anode plate can pass, a blowing port provided in a side surface of the recovery container and through which nitrogen gas is blown into the recovery container, a support plate portion provided in the recovery container and extending from an inner side surface of the recovery container in parallel with the upper surface of the recovery container, and a second slit provided in the support plate portion and through which the anode plate passes, the second slit being formed in a position corresponding to the first slit;

a scraping unit provided in the vicinity of the first slit in the collection container and including a pair of scraping plates that can advance and retreat in the second slit so as to scrape a silicon solution containing the silicon powder and the waste liquid adhering to the anode portion from the anode portion by sandwiching the anode portion between the pair of scraping plates; and

a drying unit disposed below the collection container, the drying unit including a conveyor belt that conveys the silicon solution scraped by the scraping unit to a collection box, and a heater unit that heats the silicon solution to dry the silicon solution while the conveyor belt is conveying the silicon solution, and the dried silicon powder remains as lumps on the conveyor belt,

collecting the silicon powder dried by the drying unit,

the recovery container, the drying unit, and the collection box were placed in a nitrogen atmosphere by blowing nitrogen gas through the blowing port.

2. A method for recovering silicon powder by using the apparatus for recovering silicon powder according to claim 1, which comprises recovering a waste liquid containing silicon powder discharged from a processing apparatus for grinding solid silicon using a processing liquid and abrasive grains, removing water from the waste liquid, and recovering the silicon powder, wherein the method comprises the steps of:

an adhesion step of bringing an anode section and a cathode section into contact with the waste liquid, and energizing the anode section and the cathode section to adhere the silicon powder to the positively charged anode section;

a recovery step of lifting the anode portion from the waste liquid, sandwiching the anode portion between a pair of scraping plates, and scraping and recovering a silicon solution adhering to the anode portion from the anode portion, the silicon solution including the silicon powder and the waste liquid; and

a drying step of heating the silicon solution by the heater unit of the drying unit while the silicon solution scraped from the anode unit in the recovery step is being conveyed by the conveyor belt of the drying unit, and drying the silicon powder obtained by drying the silicon solution as lumps on the conveyor belt; and

a collecting step of collecting the silicon powder dried by the drying unit,

the recovering step, the drying step and the collecting step are made to be in a nitrogen atmosphere by blowing nitrogen gas.