Grinding device or cutting device with a sludge drying device for recovering sludge

Abstract

A combination of a grinding device (4) or a cutting device with a sludge drying device (1) for recovering sludge (P) having a high water content from a waste fluid (L) and for subsequently drying the recovered sludge (P), wherein the waste fluid (L) contains powder of a workpiece (W) ground or cut by abrasive elements (404B) of the grinding device (4) or by a cutting blade of the cutting device in a state in which grinding water or cutting water is supplied to the workpiece (W), the sludge drying device comprising: a waste fluid bath (2) for receiving the waste fluid (L); an extraction device (3) for extracting the sludge (P) from the waste fluid (L) received in the waste fluid bath (2); a conveyor belt (51) for conveying the sludge (P) extracted by the extraction device (3) to a recovery box (59); and a drying device (6) for drying the sludge (P) conveyed by the conveyor belt (51), wherein the drying device (6) comprises: a drying box (60) configured to cover at least one upper surface of the conveyor belt (51) and extend in an extension direction of the conveyor belt (51), an air inlet (604) formed at a first end of the drying box (60) as seen in a transfer direction (+Y direction), an air outlet (605) formed at a second end of the drying box (60) as seen in the transfer direction, a fan (606) arranged outside the drying box (60) for extracting air from the drying box (60) via the air outlet (605) and thereby sucking outside air into the drying box via the air inlet (604), a dividing device (607) for dividing the exhaust air G emitted by the fan (606) into two parts, and a return inlet (608) formed between the air inlet (604) and the air outlet (605) of the drying box (60), via which a part G1 of the two parts of the exhaust air G divided by the dividing device (607) can be returned to the drying box (60), wherein the outside air can be introduced via the air inlet (604) into the drying box (60) in the same amount as the amount of the other part G2 of the exhaust air G divided by the dividing device (607) and is led to an ejection device, whereby the sludge (P) conveyed on the upper surface of the conveyor belt (51) is dried, wherein the Y direction is the Y direction in a three-dimensional coordinate system.

Description

BACKGROUND OF THE INVENTIONTechnical field

[0001] The present invention relates to a combination of a grinding device or a cutting device with a sludge drying device. Description of the state of the art

[0002] When grinding a workpiece using abrasive elements while adding grinding water, grinding dust is generated from the workpiece in the state of being mixed with the grinding water, thus producing a waste fluid. The grinding dust (sludge), which has a high water content, is recovered by separating the sludge in the waste fluid or by immersing a positive plate and a negative plate in the waste fluid and then applying electric charges to the positive plate and the negative plate to thereby deposit the sludge on the positive plate. Furthermore, the remaining water is reused by removing the sludge from the waste fluid (see, for example, JP 2013-119050 A). JP 2016-049506 A concerns the recovery of silicon powder.

[0003] A sludge recovery device is used to dry the recovered sludge for use.

[0004] DE 10 2008 056 739 A1 relates to a method and a device for drying.

[0005] DE 42 35 422 A1 relates to a process for drying pasty material, in particular sewage sludge, and a device for carrying out the process. PRESENTATION OF THE INVENTION

[0006] However, in the sludge recovery device disclosed in JP 2016-049506 A, a heater is used to dry the sludge. Accordingly, when maintenance of the sludge recovery device is necessary, an operator must wait until a component heated by the heater has cooled down. Furthermore, electrical power is required to operate the heater.

[0007] It is therefore an object of the present invention to provide a sludge drying apparatus which can dry a sludge without using a heater after recovering the sludge from the waste fluid.

[0008] The object is achieved by a combination of a grinding device or a cutting device with a sludge drying device according to claim 1.

[0009] During operation of the device, a portion of the exhaust air divided by the dividing device (the air is heated by the fan) is returned to the drying box via the return inlet. Outside air is introduced into the drying box via the air inlet in an amount equal to the amount of the other portion of the exhaust air divided by the dividing device and directed to an exhaust device. Accordingly, the sludge conveyed by the conveyor belt in the drying box can be efficiently dried by the flow of the mixed air returned via the return inlet and the outside air introduced into the drying box via the air inlet. Furthermore, during sludge drying, an increased concentration of hydrogen in the drying box is suppressed, thereby preventing a hydrogen explosion.Furthermore, since no heating is used during sludge drying, the power consumption of the sludge drying device is reduced, and the sludge is dried without being melted by the heat of a heater. In addition, there is no need for an operator to wait while replacing the conveyor belt or cleaning the interior of the drying box.

[0010] The above and other objects, features and advantages of the present invention and the mode for carrying them out will become clearer and the invention itself best understood by studying the following description and claims with reference to the figures which show a preferred embodiment of the invention. SHORT DESCRIPTION OF THE CHARACTERS Fig. 1 is a sectional view illustrating the structure of a grinding apparatus and a sludge drying apparatus according to a preferred embodiment of the present invention; Fig. Fig. 2 is an enlarged sectional view showing an arrangement of the positive plates and negative plates in a waste fluid bath used in the sludge drying apparatus shown in Fig. 1 is shown, arranged, represents; Fig. 3 is an enlarged sectional view illustrating a state in which sludge is deposited on the positive plate, and the sludge is then dropped from the positive plate into a drying box; Fig. Fig. 4 is an enlarged sectional view showing a state in which the sludge has just been dropped into the drying box; and Fig. 5 is an enlarged sectional view illustrating a state in which the sludge conveyed by a conveyor belt is conveyed by a conveyor belt in drying the sludge. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0011] With reference to Fig. 1 shows a sludge drying apparatus 1 according to a preferred embodiment of the present invention. A grinding device 4 having abrasive elements 404b is arranged near the sludge drying apparatus 1. In the grinding device 4, a workpiece W is ground by abrasive elements 404b in the state where grinding water is supplied to the workpiece W. Accordingly, a waste fluid L containing the powder of the workpiece W ground by the abrasive elements 404b is discharged from the grinding device 4. The sludge drying apparatus 1 is an apparatus for recovering a sludge P having a high water content from the waste fluid L and then drying the sludge.While the sludge drying device 1 is separate from the grinding device 4 in this preferred embodiment, the sludge drying device 1 may be integrated with the grinding device 4. As a modification, the sludge drying device 1 may be connected to a cutting device having a rotatable cutting blade for cutting the workpiece W while supplying cutting water to the workpiece W by recovering a sludge containing a high amount of water from a waste fluid discharged from the cutting device.

[0012] The grinding device 4, which is in Fig. 1, essentially comprises a holding table 41 for holding the workpiece W as a solid material and a grinding unit 40 having a rotatable grinding wheel 404 containing the abrasive elements 404b that grind the workpiece W. While the workpiece W in this preferred embodiment is a silicon wafer, the workpiece W may be a silicon ingot as a solid cylindrical workpiece.

[0013] The grinding device 4 has a base 49 having an upper opening 49a. The holding table 41 is arranged on the base 49. The holding table 41 has a holding surface 41a formed of a porous member or the like. The holding surface 41a is connected to a vacuum source (not shown). The holding table 41 is rotatable about its axis extending in the Z direction. The holding table 41 is supported by a table support 42 arranged in the upper opening 49a of the base 49. The table support 42 is rotatable in the X direction (in the direction perpendicular to the sheet plane of Fig. 1) movable by an X-movement mechanism (not shown) comprising a motor and a ball screw mechanism.

[0014] A box-like water housing 48 for receiving the waste fluid L from the grinding unit 40 is arranged below the holding table 41. One part of the water housing 48 is shown on both sides of the holding table 41, that is, along the opposite side surfaces of the table support 42 in the Y direction. Although not shown, the other part of the water housing 48 is arranged along the opposite side surfaces of the table support 42 in the X direction. That is, the water housing 48 has a gutter portion 484 for receiving the waste fluid L. The gutter portion 484 has a rectangular shape in a plan view in such a way that a rectangular central opening 481 is formed. The gutter portion 484 is formed of a bottom plate 480, an inner wall 482, and an outer wall 483. Accordingly, the central opening 481 is surrounded by the inner wall 482.The inner wall 482 and the outer wall 483 are connected at their lower ends to the bottom plate 480, thereby forming a rectangular annular space for receiving the waste fluid L. The bottom plate 480 is formed with an outlet port 485 for discharging the waste fluid L. A drain line 485a is connected at one end to the outlet port 485. The other end of the drain line 485a is connected to a tank 12 for receiving the waste fluid L. Accordingly, the waste fluid L containing the powder (for example, silicon powder) of the workpiece W ground by the abrasive elements 404b flows down from the holding table 41 and is received by the gutter portion 484 of the water housing 48. Thereafter, the waste fluid L is transferred from the outlet port 485 to the tank 12 through the drain line 485a.

[0015] The grinding unit 40, which is Fig. 1, a spindle 400 having an axis extending in the Z direction perpendicular to the support surface 41a of the support table 41, a motor 402 for rotating the spindle 400, a fixture 403 fixed to the lower end of the spindle 400, and the grinding wheel 404 removably connected to the fixture 403. The grinding wheel 404 is formed of an annular wheel base 404a and a plurality of abrasive elements 404b fixed to the lower surface of the wheel base 404a so as to be arranged in a ring shape at given intervals. Each abrasive element 404b has an external shape like a substantially rectangular prism. Each abrasive element in Fig. 4b is formed by bonding abrasive diamond grains or the like with a suitable connector. The grinding unit 40 is vertically movable in the Z-axis direction.

[0016] A water passage (not shown) for supplying grinding water is formed in the spindle 400 so as to extend in the axial direction (Z direction) of the spindle 400. The water passage is connected to a grinding water source (not shown). The water passage opens at the lower surface of the wheel base 404a, so that grinding water is discharged to the abrasive elements 404b. As a modification, a grinding water nozzle may be provided at a position adjacent to the grinding wheel 404 of the grinding unit 40 in the state where the grinding unit 40 is lowered to a grinding position for grinding the workpiece W. In this case, the grinding water is supplied from the grinding water nozzle to the position where the abrasive elements 404b come into contact with the workpiece W.

[0017] The sludge drying device 1 comprises a waste fluid bath 2 for receiving the waste fluid L, an extraction device 3 for extracting a sludge P having a high water content from the waste fluid L received in the waste fluid bath 2, a conveyor belt 51 for conveying the sludge P extracted by the extraction device 3 to a recovery box 59, and a drying device 6 for drying the sludge P conveyed by the conveyor belt 51.

[0018] The tank 12 for receiving the waste fluid L is located lower than the drain opening 485 of the water housing 48. The tank 12 has an inlet opening 120. One end of the drain line 485a is connected to the drain opening 485, and the other end of the drain line 485a is connected to the inlet opening 120 of the tank 12. The tank 12 also has a distribution pump 121 for lifting the waste fluid L containing the sludge P and transferring it to the waste fluid bath 2. That is, the distribution pump 121 serves to transfer the waste fluid L containing the sludge P from the tank 12 to the waste fluid bath 2 through a distribution line 121a. The waste fluid bath 2 has an inlet opening 20 connected to the distribution line 121a.

[0019] The waste fluid bath 2 has an outer shape like a rectangular prism and is formed of an insulating material such as a synthetic resin. The waste fluid bath 2 is formed of a bottom plate 21 having a rectangular shape in a plan view and four side walls rising from the outer edge of the bottom plate 21 in the +Z direction, thereby defining a space for accommodating the waste fluid L containing the sludge P. These four side walls are a pair of side walls 22a that are mutually inclined in the X direction (one of the side walls 22a is at the rear side of the sheet plane of Fig. 1), and a pair of side walls 22b arranged opposite each other in the Y direction. Furthermore, an overflow pipe (not shown) for preventing overflow of the waste fluid L is arranged at an upper portion of the waste fluid bath 2. This overflow pipe is connected to the tank 12 so that the waste fluid L can be returned to the tank 12 through the overflow pipe before overflowing from the waste fluid bath 2.

[0020] The extraction device 3, which extracts the sludge P having a high water content from the waste fluid L received in the waste fluid bath 2, comprises a plurality of negative plates 30 arranged in the waste fluid bath 2 and adapted to be negatively charged, a plurality of positive plates 31 arranged opposite the negative plates 30 and adapted to be positively charged to attract the sludge P having a high water content, each positive plate 31 being removable from the waste fluid bath 2, a handling means 32 having a holding section 320 for holding each positive plate 31, the holding section 320 being vertically movable to take each positive plate 31 out of the waste fluid bath 2 or to introduce each positive plate 31 into the waste fluid bath 2, and a stripping means 36 for removing the sludge P from each positive plate 31.which is removed from the waste fluid bath 2 by the handling means 32,

[0021] Each positive plate 31 is formed of an electrochemically noble metal such as copper, silver, platinum, or gold. In this preferred embodiment, each positive plate 31 is formed of stainless steel. Each positive plate 31 is a rectangular, flat plate element.

[0022] A plurality of support grooves (not shown) are formed in the inner surfaces of the two side walls 22a of the waste fluid bath 2, with the two side walls 22a facing each other in the X direction. The plurality of support grooves formed on each side wall 22a are spaced at given intervals in the Y direction. The plurality of positive plates 31 are loosely inserted into these plurality of support grooves and are thereby arranged at given intervals in the Y direction in the waste fluid bath 2. That is, the plurality of positive plates 31 are arranged at given intervals in the Y direction in the state where both side surfaces of each positive plate 31 are perpendicular to the Y direction, that is, parallel to the X direction. Two projections 310 are formed on the upper end surface of each positive plate 31 at a central portion so as to be spaced from each other in the X direction (one of the two projections 310 is shown).Each projection 310 is a rectangular plate portion and has a central through-hole 310a extending in the X direction. The through-hole 310a of each projection 310 is adapted to engage with a pin 320a disposed in the holding portion 320 of the handling means 32.

[0023] Each negative plate 30 is sandwiched between adjacent positive plates 31. That is, each negative plate 30 is parallel to the adjacent positive plates 31 in the Y direction, so that they are spaced apart by a given distance. Thus, the plurality of negative plates 30 and the plurality of positive plates 31 are alternately arranged at given intervals in the Y direction.

[0024] For example, as in Fig. As shown in Figure 1, each negative plate 30 is supported by a frame 33a having a rectangular shape in a side view (in the Y direction). The frame 33a has a given width in the Y direction. The frame 33a is equipped with a pipe 33b for transferring clean water to a clean water receiving tank (not shown). The clean water is obtained by removing the sludge P from the waste fluid L and can enter an internal space of the frame 33a. As shown in Fig. As shown in Figure 1, the frame 33a has a pair of rectangular openings on both sides, and a pair of negative plates 30 are attached to the frame 33a so as to close the pair of rectangular openings. Accordingly, the pair of negative plates 30 are spaced parallel on each frame 33a. Each frame 33a, which supports the pair of negative plates 30, is inserted between positive plates 31.

[0025] Similar to the positive plates 31, each negative plate 30 is formed of an electrochemically noble metal such as copper, silver, platinum, or gold. In this preferred embodiment, each negative plate 30 is formed of stainless steel. Each negative plate 30 is a mesh plate adapted to be negatively charged and thereby exert a repulsive force on the sludge P. Accordingly, the sludge P does not get caught in the mesh of each negative plate 30. That is, when each negative plate 30 is negatively charged, only the pure water in the waste fluid L can flow through the negative plate 30. The sludge P is negatively charged, so a repulsive force occurs between the sludge P and each negative plate 30, and the flow of the sludge P through each negative plate 30 is restricted.Accordingly, the pure water that has flowed through each negative plate 30 is accommodated in the internal space formed by each frame 33a and the two negative plates 30 supported on each frame 33a. Since a repulsive force occurs between each negative plate 30 and the sludge P, the internal space of each frame 33a is kept clear of the waste fluid L containing the sludge P.

[0026] Furthermore, a distance of a predetermined size is defined between the lower end of each frame 33a and the bottom plate 21 of the waste fluid bath 2, and a distance of a predetermined size is defined between the lower end of each positive plate 31 and the bottom plate 21 of the waste fluid bath 2. Accordingly, the waste fluid L supplied to the waste fluid bath 2 can flow through these spaces and rise in the space between the negative plate 30 and the positive plate 31, which are adjacent to each other.

[0027] In this preferred embodiment, a DC voltage is applied between the positive plate 31 and the negative plate 30, which are adjacent to each other (see Fig. 2). That is, the positive electrode of a DC voltage source is electrically connected to each positive plate 31, thereby positively charging each positive plate 31 in the waste fluid L. Accordingly, each positive plate 31 will attract the sludge P, which is negatively charged in the waste fluid L. On the other hand, the negative electrode of the DC voltage source is electrically connected to each negative plate 30, thereby negatively charging each negative plate 30 in the waste fluid L.

[0028] With reference to Fig. 1, the handling means 32, which removes each positive plate 31 from the waste fluid bath 2 and places each positive plate 31 into the waste fluid bath 2, is movable horizontally in the Y direction above the waste fluid bath 2 by means of a Y-moving mechanism 34. The Y-moving mechanism 34 includes a base 341 extending in the Y direction, a vertical plate 342 extending in the Z direction, the vertical plate 342 being supported on the base 341 so that it can be moved along the base 341 in the Y direction, and a ball screw mechanism (not shown) for moving the vertical plate 342.

[0029] A movable member 323 is fixed to a side surface of the vertical plate 342, and the handling means 32 is adapted to be moved in the Z direction by the movable member 323. The handling means 32 includes a pair of holding portions 320 for holding each positive plate 31. For example, each holding portion 320 is configured by a clamping cylinder disposed on the side surface of the movable member 323. The pair of holding portions 320 are arranged opposite each other in the X direction at a given distance. Each holding portion 320 includes a cylinder body 320b fixed to the movable member 323 and a pin 320a adapted to retractably protrude from the cylinder body 320b in the X direction. The two pins 320a of the pair of holding portions 320 are adapted to protrude from the respective cylinder bodies 320b toward each other in the X direction.When the movable member 323 is lowered to position the two holding portions 320 at the upper end of each positive plate 31, the two pins 320a are actuated to protrude from the respective cylinder bodies 320b and respectively engage with the two through holes 310a of the respective projections 310 of each positive plate 31. Accordingly, each positive plate is held by the two holding portions 320 of the handling means 32.

[0030] The stripping means 36, which strips the sludge P from each positive plate 31 taken out of the waste fluid bath 2 by the handling means 32, is simply in Fig. 1 and detailed in Fig. 3. As shown in Fig. As shown in Figure 3, the stripping means 36 is arranged above an air inlet 604 of a drying box 60 arranged in the drying device 6. The air inlet 604 is arranged at a first end of the drying box 60, viewed in the transfer direction (+Y direction). The stripping means 36 comprises a pair of cylinders 360 (motor-driven cylinders or air cylinders), a pair of support plates 361 for supporting the pair of cylinders 360, and a pair of stripping plates 362 adapted to be moved in the Y direction by the pair of cylinders 360.

[0031] Each cylinder 360 includes a cylinder tube 360a that accommodates a piston (not shown) and a piston rod 360b partially inserted into the cylinder tube 360a and having one end fixed to the piston. Each stripper plate 362 is fixed to the other end of the piston rod 360b of the corresponding cylinder 360. The pair of stripper plates 362 oppose each other in the Y direction in such a manner that each positive plate 31 can be inserted between the ends of the pair of stripper plates 362. Each stripper plate 362 extends in the X direction and has a length greater than the width of each positive plate 31 (the length in the X direction).

[0032] With this configuration, the opposite side surfaces of each positive plate 31 can be clamped by the pair of stripping plates 362 of the stripping means 36. In this state, with the opposite side surfaces of each positive plate 31 clamped by the pair of stripping plates 362, the pair of holding portions 320 of the handling means 32 that hold each positive plate 31 are lifted. As a result, the sludge P having a high water content can be stripped from the opposite side surfaces of each positive plate 31 by the pair of stripping plates 362.

[0033] The drying device 6, which removes water from the sludge P, is arranged adjacent to the waste fluid bath 2. The sludge P, which has a high water content when extracted from the waste fluid L by the extraction device 3, is dried on the conveyor belt 51 and transferred to the recovery box 59. The conveyor belt 51 is arranged in the drying box 60 of the drying device 6 so that it extends in the Y direction.

[0034] The drying device 6, which dries the sludge P conveyed by the conveyor belt 51, comprises a drying box 60 configured to cover at least the upper surface of the conveyor belt 51 and extend in the direction of extension of the conveyor belt 51, an air inlet 604 formed at a first end of the drying box 60 as viewed in the transfer direction, and an air outlet 605 formed at the second end of the drying box 60 as viewed in the transfer direction, a fan 606 arranged outside the drying box 60 to exhaust the air in the drying box 60 via the air outlet 605 and thereby suck the outside air into the drying box 60 via the air inlet 604, a dividing device 607 for dividing the exhaust air G discharged from the fan 606 into two parts G1, G2 and a Return inlet 608,which is formed between the air inlet 604 and the air outlet 605 of the drying box 60, via which the part G1 of the exhaust air G, which is divided by the dividing device 607, is returned to the drying box 60.

[0035] The drying box 60 has an external shape like a rectangular prism. That is, the drying box 60 is formed of a rectangular bottom plate 601, four side walls rising from the outer edge of the bottom plate 601 in the +Z direction, and an upper plate 603 connected to the upper ends of the four side walls and facing the upper surface of the conveyor belt 51 in the (+Z direction) perpendicular to the conveying direction. These four side walls are a pair of side walls 602a extending in the X direction (one of the side walls 602a is at the rear side of the sheet plane of Fig. 3), and a pair of side walls 602b opposite each other in the Y direction. The inner space of the drying box 60 has an air passage 600 for guiding the air in the conveying direction in which the sludge P is conveyed by the conveyor belt 51.

[0036] The air inlet 604 is formed at a first end of the upper plate 603, as viewed in the transfer direction. The air inlet 604 also serves as an inlet for introducing the sludge P scraped off and dropped from each positive plate 31. Consequently, the sludge P, which has a high water content, is dropped into the drying box 60 through the air inlet 604. The air inlet 604 is formed with a cover 604d having a plurality of through holes 604c to allow air to pass through. The cover 604d is connected to the upper plate 603 via a hinge, whereby the air inlet 604 can be opened and closed. A guide plate 604b is arranged below the air inlet 604. The guide plate 604b is inclined so that the sludge P dropped through the air inlet 604 is guided to the upper surface of the conveyor belt 51.

[0037] The conveyor belt 51 is an endless belt and is rotationally driven by a motor 540. The motor 540 is fixed to one of the side walls 602a. A drive roller 541 is attached to the shaft of the motor 540, and the conveyor belt 51 is wound around the drive roller 541. The front end of the shaft of the motor 540 is supported on the other side wall 602a. A roller 542 is rotatably attached to the side walls 602a at a position spaced a given distance from the motor 540 in the Y direction. The conveyor belt 51 is also wound around the roller 542. Accordingly, when the motor 540 is actuated to actuate the drive roller 541, the conveyor belt 51 is moved to move the roller 542.

[0038] The drying device 6 includes a scraper 55 for spreading the sludge P placed on the conveyor belt 51 along with the movement of the conveyor belt 51, thereby flattening the sludge P into a plate-like material having a given thickness. The scraper 55 extends in the X direction, and both ends of the scraper 55 are fixed to the side walls 602a.

[0039] The air outlet 605 for discharging air and other gases from the drying box 60 is arranged at the second end of the upper plate 603, viewed in the transfer direction. The air outlet 605 is connected to an inlet opening of the fan 606 through an exhaust duct 605b. A duct 606b is connected at one end to an outlet 606a of the fan 606. The dividing device 607 is connected to the other end of the duct 606b. The dividing device 607 serves to divide the air (exhaust air G) expelled by the fan 606 into two parts. For example, the dividing device 607 is implemented by a three-way valve capable of directing the exhaust air G to be divided into an exhaust duct 607a and a return duct 607b.As a modification, the dividing device 607 may be formed of a dividing pipe and a control valve capable of controlling the amount of exhaust air G flowing into the discharge line 607a and the return line 607b. As another modification, the amount of exhaust air G may be adjusted according to the diameters of the discharge line 607a and the return line 607b.

[0040] Consequently, one end of the exhaust duct 607a and one end of the return duct 607b are connected to the dividing device 607. The other end of the exhaust duct 607a is connected to an exhaust device having a suction means. The return duct 607b serves to return a portion G1 of the exhaust air G, which is divided by the dividing device 607, to the drying box 60. The other end of the return duct 607b is connected to the return inlet 608. The return inlet 608 is arranged in the top plate 603 at a position between the air inlet 604 and the air outlet 605.

[0041] A sludge outlet 609 is formed in the bottom plate 601 at a second end thereof as seen in the transfer direction. The sludge P, which has a high water content, is dried on the conveyor belt 51 to form a dry sludge P1 (see Fig. 1). The dry sludge P1 falls from the conveyor belt 51 through the sludge outlet 609 into the recovery box 59. A shutter 609d is pivotally attached to the lower end of the sludge outlet 609 by a spring joint.

[0042] The recovery box 59 is located below the sludge outlet 609 of the drying box 60. The recovery box 59 has an outer shape like a rectangular prism and is open at its upper end directly below the sludge outlet 609 of the drying box 60. A sensor (not shown), such as an optical transmission sensor, is arranged at an upper portion of the recovery box 59. The sensor serves to detect the amount of dry sludge P1 accommodated in the recovery box 59. That is, when the dry sludge P1 falls from the conveyor belt 51 into the recovery box 59 and is accommodated up to a predetermined height in the recovery box 59, this condition is detected by the sensor to issue an alarm indicating that the recovery box 59 needs to be replaced.

[0043] A plurality of projections 603a for generating turbulence are formed on the lower surface of the upper plate 603. In this preferred embodiment, each projection 603a has an outer semicircular shape as shown in Fig. 1 and Fig. 3. As a modification, each protrusion 603a may have a cylindrical or prismatic outer shape. While the plurality of protrusions 603a are arranged at equal intervals in both the X direction and the Y direction in this preferred embodiment, the plurality of protrusions 603a may be arranged randomly. In the case where each protrusion 603a has a cylindrical or prismatic outer shape, a plurality of protrusions 603a may be arranged at equal intervals in the Y direction in the state where the axis of each protrusion 603a extends in the X direction.

[0044] Due to the presence of the protrusions 603a, the air flowing in the air passage 600 in the drying box 60 collides with the protrusions 603a formed on the lower surface of the upper plate 603 of the drying box 60, thereby generating turbulence. That is, an uneven flow of air is formed above the conveyor belt 51 by the plurality of protrusions 603a, and the air flows in the transfer direction in this state. As a result of the turbulence, the air is blown against the sludge P having a high water content and conveyed on the upper surface of the conveyor belt 51, thereby facilitating the evaporation of water from the sludge P. However, the formation of the plurality of protrusions 603a on the lower surface of the upper plate 603 is not essential.

[0045] The operation of the sludge drying apparatus 1 will now be described for the case where the workpiece W is ground by abrasive elements 404b in the state where grinding water is supplied to the workpiece W and where sludge P having a high water content is recovered from the waste fluid L containing powder of the workpiece W ground by the abrasive elements 404b.

[0046] The workpiece W is first held on the holding surface 41a of the holding table 41 under suction. Then, the table support 42 is moved to set the holding table 41 holding the workpiece W to the grinding position where the workpiece W is opposed to the abrasive elements 404b.

[0047] The motor 402 is next actuated to rotate the spindle 400 about its vertical axis extending in the Z direction, thereby rotating the grinding wheel 404. Thereafter, the grinding unit 40 is lowered until the abrasive elements 404b come into contact with the upper surface of the workpiece W held on the holding table 41. At this time, the holding table 41 is also rotated at a predetermined speed, thereby rotating the workpiece W held on the holding surface 41a. Accordingly, the upper surface of the workpiece W is completely ground by the abrasive elements 404b. During this grinding operation, grinding water is supplied to the position where the abrasive elements 404b come into contact with the upper surface of the workpiece W, thereby cooling and cleaning the contact position.

[0048] In this manner, the workpiece W is ground to cause the formation of fine powder (silicon powder) from the workpiece W. This fine powder is mixed with the grinding water to produce the waste fluid L. The waste fluid L thus produced flows through the upper opening 49a into the water housing 48. Thereafter, the waste fluid L is transferred to the tank 12 through the drain line 485a and then led to the waste fluid bath 2 through the distribution line 121a. The waste fluid L is now stored in the waste fluid bath 2. The powder of the workpiece W absorbs the grinding water, so that it becomes slurry P having a high water content.

[0049] In the state where the waste fluid L is stored in the waste fluid bath 2, the positive plates 31 and the negative plates 30 are immersed in the waste fluid L, as shown in Fig. 2. Next, the positive electrode of the DC power source is connected to the positive plates 31, and the negative electrode of the DC power source is connected to the negative plates 30, thereby positively charging the positive plates 31 and negatively charging the negative plates 30. As a result, an electric field is formed between the positive plate 31 and the negative plate 30, which are adjacent to each other. Accordingly, due to electrophoresis, the sludge P mixed in the waste fluid L and negatively charged experiences a repulsive force from the negative plates 30, which are negatively charged, and an attractive force from the positive plates 31, which are positively charged.

[0050] After a given amount of sludge P is deposited on the positive plates 31, the Y-movement mechanism 34 is actuated to move the holding portions 320 of the handling means 32 to the position immediately above one of the positive plates 31. Thereafter, the holding portions 320 are lowered to hold this positive plate 31 and then raised to remove this positive plate 31 from the waste fluid L accommodated in the waste fluid bath 2. Thereafter, the Y-movement mechanism 34 is actuated to move the holding portions 320 holding the positive plate 31 to the position immediately above the air inlet 604 of the drying box 60.

[0051] Thereafter, the pair of cylinders 360 of the stripping means 36 are actuated to move the pair of stripping plates 362 horizontally relative to each other, thereby clamping the positive plate 31 between the pair of stripping plates 362, as shown in Fig. 3. Thereafter, the movable member 323 (see Fig. 1) is actuated to raise the holding portions 320, thereby raising the positive plate 31. As a result, the sludge P having a high water content is scraped off the positive plate 31 by the pair of scraper plates 362. Accordingly, as shown in Fig. As shown in Figure 4, the sludge P in the form of a lump is dropped from the positive plate 31 through the air inlet 604 of the drying box 60 onto the guide plate 604b disposed in the drying box 60. The lump of sludge P is moved to the upper surface of the conveyor belt 51 due to the inclination of the guide plate 604b. At this time, the cover 604d is opened.

[0052] After placing the lump of sludge P on the upper surface of the conveyor belt 51, the cover 604d is closed as shown in Fig. 5. Thereafter, the motor 540 is actuated to rotate the drive roller 541, thereby rotating the conveyor belt 51 and the roller 542. As a result, the sludge P is conveyed in the transfer direction by the conveyor belt 51. At this time, the lump of sludge P passes through the gap between the scraper 55 and the conveyor belt 51, so that the lump of sludge is spread on the conveyor belt 51 to become a plate-shaped material with a given thickness (for example, 1 to 2 mm).

[0053] During the transfer of the sludge P having a high water content through the conveyor belt 51, the blower 606 disposed outside the drying box 60 is operated to exhaust the air (gas) from the drying box 60 through the air outlet 605. Accordingly, the outside air is introduced into the drying box 60 through the through-holes 604c of the cover 604d and the air inlet 604. The outside air thus introduced into the drying box 60 flows in the air passage 600 in the transfer direction. As a result, the water contained in the sludge P on the conveyor belt 51 is evaporated, so that the sludge P is dried.

[0054] The flow rate of the exhaust air G expelled by the fan 606, as shown by an arrow A, is, for example, at 10 m 3 / min. The exhaust air G, which is discharged from the outlet 606a of the blower 606 via the line 606b, is converted into an exhaust air G1 (flow rate of 5 m 3 / min) and an exhaust air G2 (flow rate 5 m 3 / min) by the dividing device 607, with the exhaust air G1 being returned to the drying box 60 and the exhaust air G2 being led to the ejection device. The exhaust air G absorbs heat generated by a motor (not shown) in the fan 606, so that the temperature of the exhaust air G differs by 5 to 6 degrees from the temperature of the sucked-in air. Accordingly, the temperature of the exhaust gas G1 is 5 to 6 degrees higher than the temperature of the outside air introduced into the drying box 60 via the air inlet 604. The exhaust air G1 is returned to the drying box 60 through the return line 607b and the return inlet 608. The ratio between the flow rate of the exhaust air G1 and the flow rate of the exhaust air G2 is not limited to 1:1.

[0055] In this way, the exhaust air G1, as a part of the exhaust air G divided by the dividing device 607, is returned to the drying box 60 via the return inlet 608, and the air is further sucked through the air outlet 605 of the drying box 60 by the fan 606. In order to keep the air pressure in the drying box 60 constant, outside air is supplied via the air inlet 604 into the drying box 60, as shown by arrows B and C, in the same amount (for example, flow rate of 5 m 3 / min) as the flow rate of the exhaust air G2 as the other part of the exhaust air G divided by the dividing device 607. The exhaust air G1 returned via the return inlet 608 and the outside air introduced via the air inlet 604 are mixed with each other in the drying box 60, and the resulting mixed gas flows in the air passage 600 in the transfer direction. Consequently, the water contained in the sludge P on the conveyor belt 51 evaporates due to the flow of this mixed gas, so that the sludge P is efficiently dried.

[0056] As described above, in the sludge drying device 1 according to this preferred embodiment, the exhaust air G1, which is divided as a part of the exhaust air G by the dividing device 607 (the exhaust air G is heated in the fan 606), is returned to the drying box 60 via the return inlet 608. At this time, the outside air is introduced into the drying box 60 via the air inlet 604 in the same amount as the amount of exhaust air G2 as the other part of the exhaust air G divided by the dividing device 607. Accordingly, the sludge P conveyed by the conveyor belt 51 in the drying box 60 can be efficiently dried by the flow of the mixture of the exhaust air G1 and the outside air introduced into the drying box 60. Furthermore, during the drying of the sludge P, hydrogen is generated in the drying box 60 due to the contact of the air and the sludge P.However, unlike the case of heating with a heater, the generated hydrogen does not accumulate in the drying box 60. That is, an increase in the concentration of hydrogen in the drying box 60 is suppressed, thereby preventing a hydrogen explosion. Furthermore, since no heater is used when drying the sludge P, the power consumption of the sludge drying device 1 can be reduced, and the sludge P can be dried without being melted by the heat of a heater. That is, adhesion of the sludge P to the conveyor belt 51 is prevented, and it is not necessary for an operator to wait when replacing the conveyor belt 51 or cleaning the interior of the drying box 60. Furthermore, the amount of exhaust air G2 supplied to the ejection device can also be reduced, thereby reducing a load on the ejection device.

[0057] By removing the water from the sludge P having a high water content as described above, only dry sludge P1 remains on the conveyor belt 51. When the dry sludge P1 on the conveyor belt 51 arrives behind the roller 542, the dry sludge P1 falls into the recovery box 59. At this time, the shutter 609d is opened by the weight of the dry sludge P1, so that the dry sludge P1 is recovered in the recovery box 59.

Claims

[1] A combination of a grinding device (4) or a cutting device with a sludge drying device (1) for recovering sludge (P) having a high water content from a waste fluid (L) and for subsequently drying the recovered sludge (P), wherein the waste fluid (L) contains powder of a workpiece (W) ground or cut by abrasive elements (404B) of the grinding device (4) or by a cutting blade of the cutting device in a state in which grinding water or cutting water is supplied to the workpiece (W), the sludge drying device comprising: a waste fluid bath (2) for receiving the waste fluid (L); an extraction device (3) for extracting the sludge (P) from the waste fluid (L) received in the waste fluid bath (2); a conveyor belt (51) for conveying the sludge (P) extracted by the extraction device (3) to a recovery box (59); and a drying device (6) for drying the sludge (P) conveyed by the conveyor belt (51), wherein the drying device (6) comprises: a drying box (60) configured to cover at least one upper surface of the conveyor belt (51) and extend in an extension direction of the conveyor belt (51), an air inlet (604) formed at a first end of the drying box (60) as seen in a transfer direction (+Y direction), an air outlet (605) formed at a second end of the drying box (60) as seen in the transfer direction, a fan (606) arranged outside the drying box (60) for extracting air from the drying box (60) via the air outlet (605) and thereby sucking outside air into the drying box via the air inlet (604), a dividing device (607) for dividing the exhaust air G emitted by the fan (606) into two parts, and a return inlet (608) formed between the air inlet (604) and the air outlet (605) of the drying box (60), via which a part G1 of the two parts of the exhaust air G divided by the dividing device (607) can be returned to the drying box (60), wherein the outside air can be introduced via the air inlet (604) into the drying box (60) in the same amount as the amount of the other part G2 of the exhaust air G divided by the dividing device (607) and is led to an ejection device, whereby the sludge (P) conveyed on the upper surface of the conveyor belt (51) is dried, wherein the Y direction is the Y direction in a three-dimensional coordinate system.

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