Rotary scraper and method for discharging foreign matter having high specific gravity in gypsum slurry

Abstract

Provided is a rotary scraper capable of discharging a hard foreign matter having a large specific gravity such as gravel settled in a liquid, reducing liquid leakage, and easily coping with abrasion caused by the hard foreign matter. The rotary scraper comprises at least three plates of an upper plate, a lower plate, and an intermediate plate between the upper plate and the lower plate so as to overlap each other in a plan view. Each of the three plates is provided with an opening which penetrates the plate in the vertical direction. The rotary scraper further comprises a means for rotating the intermediate plate. The openings are arranged so as to switch, through rotation of the intermediate plate, between a state where the opening of the upper plate and the opening of the intermediate plate are in communication with each other but not in communication with the opening of the lower plate, and a state where the opening of the intermediate plate and the opening of the lower plate are in communication with each other but not in communication with the opening of the upper plate.

Description

Rotary scraper and method for removing high specific gravity foreign matter from gypsum slurry

[0001] This invention relates to a rotary scraper suitable for removing heavy, hard solid foreign matter that has settled in a liquid, such as gravel, sand, small metal objects, etc. This invention also relates to the removal of foreign matter from a gypsum slurry using this rotary scraper.

[0002] The applicant has established a technology for commercially recovering gypsum from waste gypsum board. The waste gypsum board is crushed and calcined to convert it into hemihydrate or anhydrous type III gypsum. The resulting gypsum slurry is then retained in a crystallization tank, where gypsum particles such as gypsum dihydrate are precipitated and subjected to solid-liquid separation. Waste gypsum board may contain gravel and sand derived from gypsum plaster, etc. It may also contain small metal objects such as nails and screws. While it is preferable to remove these hard, heavy foreign objects in a pretreatment process, it is difficult to completely remove them.

[0003] The applicant proposed removing heavy foreign matter, such as gravel, sand, and metal, from the gypsum slurry in the crystallization tank by settling it to the bottom of a settling tank due to differences in specific gravity between the gypsum particles and water (Patent Document 1: JP 2020-65975 A). A rotary scraper was used to remove the settled gravel and other foreign matter. A standard rotary scraper divides a cylindrical container with a horizontal axis into multiple compartments using multiple blades fixed to the rotating shaft, and solid matter such as gravel is removed from each compartment by rotating the blades. An example of a rotary scraper is shown in Patent Document 2 (JP 10-113066 A).

[0004] JP 2020-65975 JP 10-113066

[0005] If the gap between the inner surface of the container and the tip of the blade widens, the slurry will leak through the gap. When discharging gravel or other particles, the gravel or other particles get caught in the gap, widening the gap in a short period of time. Therefore, a rotary scraper is needed that can remove hard, heavy solid foreign matter such as gravel, sand, and small metal objects from liquid, with little liquid leakage and easy wear resistance. Such a rotary scraper can be used not only to remove hard foreign matter from gypsum slurry, but also to remove heavy, hard foreign matter that has settled from liquid.

[0006] An object of the present invention is to provide a rotary scraper that can remove hard, heavy foreign matter such as gravel that has settled in a liquid, reduces liquid leakage, and easily handles wear caused by the hard foreign matter.An object of the present invention is also to provide a rotary scraper that can easily remove heavy foreign matter in a gypsum slurry, such as that derived from waste gypsum board.

[0007] The rotary scraper of this invention comprises at least three plates, an upper plate, a lower plate, and an intermediate plate between them, which are overlapped in a plan view, each of the at least three plates having an opening penetrating the plate in the vertical direction, and further comprising a means for rotating the intermediate plate, and each opening is arranged so that, upon rotation of the intermediate plate, it can be switched between a state in which the opening in the upper plate and the opening in the intermediate plate are connected but not connected to the opening in the lower plate, and a state in which the opening in the intermediate plate and the opening in the lower plate are connected but not connected to the opening in the upper plate.

[0008] The rotary scraper of this invention is attached to the bottom of a settling tank or the like so that high-density foreign matter settles to the top. The settled foreign matter enters the openings in the upper plate and, when they overlap with the openings in the middle plate, moves by gravity to the opening in the middle plate. As the middle plate continues to rotate and the openings in the middle plate overlap with the openings in the lower plate, the foreign matter falls through the openings in the middle plate and through the openings in the lower plate. This allows the foreign matter to be discharged in predetermined amounts. Since the three openings in the three plates do not overlap simultaneously, there is no risk of large liquid leakage. The device can be used to discharge any object, including hard, high-density foreign matter, from a liquid. Three plates are sufficient, but two or more middle plates may be used.

[0009] Preferably, a total of at least two resin films are provided between the upper plate and the intermediate plate, and between the intermediate plate and the lower plate, each resin film is fixed to one of the plates, and each film has an opening that penetrates the film vertically and communicates with the opening of the plate to which the film is fixed, the upper plate and the lower plate have a larger diameter than the intermediate plate, an elastic ring is provided between the upper plate and the lower plate so as to surround the intermediate plate in an annular shape, and a fastening member is provided that pressurizes the elastic ring and fastens the upper plate and the lower plate so as to freely adjust the gap between the upper plate and the lower plate.

[0010] By providing a resin film between the plates, damage to the plates due to hard foreign matter can be prevented. Because the resin film is pressurized by the fastening members, foreign matter is less likely to enter between the film and the plates. Even if foreign matter does enter and damage the resin film, the elasticity of the resin film closes the gap between the plates. This more reliably prevents liquid leakage. When the resin film wears, the fastening members can adjust the spacing between the plates, preventing gaps from forming between the plates and the resin film. The resin film is, for example, approximately 1 mm to 30 mm thick, and a typical material is PTFE, which is elastic, wear-resistant, and preferably has a low coefficient of friction.

[0011] In the method for discharging high-specific-gravity foreign matter in a gypsum slurry of the present invention, the rotary scraper of the present invention is attached to the bottom of a gypsum slurry container, the high-specific-gravity foreign matter in the gypsum slurry is allowed to settle to the bottom of the container, the high-specific-gravity foreign matter is introduced from the opening at the bottom of the container to the opening in the upper plate, the high-specific-gravity foreign matter is moved to the opening in the intermediate plate by rotation of the intermediate plate, and then the high-specific-gravity foreign matter is discharged to the outside from the opening in the intermediate plate through the opening in the lower plate.

[0012] This method allows the settled foreign matter to be discharged in predetermined amounts from the openings in the upper plate through the openings in the middle plate. Furthermore, there is little leakage of slurry, and the machine can be operated continuously for a longer period of time than conventional rotary scrapers.

[0013] Cross-sectional view of the rotary scraper of the embodiment. Plan view of the main part of the rotary scraper of the embodiment. Vertical cross-sectional view in the III-III direction of FIG. 2. Vertical cross-sectional view of a rotary scraper of a modified example. Process diagram of a method for recycling waste gypsum board using the rotary scraper of the embodiment.

[0014] The following examples are provided for carrying out the present invention. The scope of the present invention should be determined based on the claims, taking into account the description in the specification and well-known techniques in this field, and in accordance with the understanding of those skilled in the art.

[0015] 1 to 3 show a rotary scraper 2 according to an embodiment, and FIG. 4 shows a rotary scraper 2' according to a modified example. In FIGS. 1 to 3, the rotary scraper 2 (hereinafter referred to as "scraper 2") comprises a lower plate 3, an upper metal plate 4, and a rotating plate 6 therebetween. Plates 3 and 4 are suitably made of metal or plastic. Rotating plate 6 comprises an intermediate plate 10 made of metal or plastic, and thick resin films 7 and 8 above and below plate 10. Plates 3, 4, and 6 are circular in plan view, and resin films 7 and 8 are made of a resin, such as a fluororesin, that has lubricity and high wear resistance.

[0016] Plates 3, 4, and 6 are all circular in plan view, and films 7 and 8 and plate 10 are also circular. Films 7 and 8 have openings 25a and 25b that communicate with opening 20. In this embodiment, films 7 and 8 rotate together with plate 10, but the upper film 8 may be fixed to the upper plate 4, and the lower film 7 may be fixed to the lower plate 3. When film 8 is fixed to plate 4, opening 25b communicates with opening 22. When film 7 is fixed to plate 3, opening 25a communicates with opening 24.

[0017] The rotating plate 6 is rotated by a motor 12 and, for example, a vertical shaft 14, and an annular elastic ring 18 is placed between the upper and lower plates 3 and 4, and the plates 3 and 4 are pressurized by fasteners such as bolts 16 and nuts 17, which allow for adjustable clearance. The elastic ring 18 is made of plastic rubber, elastomer, or fluororesin. The elastic ring 18, bolts 16, and nuts 17 prevent liquids such as gypsum slurry from leaking from the gap between the plates 3 and 4.

[0018] The rotating plate 6 has, for example, a circular opening 20 penetrating through the films 7 and 8 and the plate 10, the lower plate 3 has, for example, a circular opening 24, and the upper plate 4 has, for example, a circular opening 22. In this embodiment, the openings 20, 22, and 24 are circular and have the same diameter, but they do not need to be the same shape or size. For example, instead of opening 20, opening 21 with an arc-shaped edge, as shown by the dashed line in FIG. 2, may be used. The openings 20, 22, and 24 are coaxial in the radial direction around the shaft 14. When the shaft 14 and the rotating plate 6 are rotated as indicated by the arrows in FIG. 2, opening 20 first overlaps with opening 22, and then, after the openings 20 and 22 are blocked, opening 20 overlaps with opening 24. The openings 20, 22, and 24 are not allowed to overlap at the same time. In this embodiment, one opening 20, 22, and 24 are provided in each of the plates 10, 3, and 4, but the same number of openings may be provided in each of the plates.

[0019] Reference numeral 30 denotes a settling tank in which hard foreign matter such as gravel 33 is allowed to settle from the slurry 34, and an opening 32 communicating with the opening 22 is provided at the bottom. The settling tank 30 is not a part of the rotary scraper 2, but the rotary scraper 2 is attached to the bottom of the settling tank 30, and the settled gravel and the like are discharged while preventing leakage of the slurry 34.

[0020] The operation of this embodiment is as follows. Gravel 33 and other particles are allowed to settle to the bottom of the settling tank 30, and the rotary plate 6 is rotated. When the openings 20 and 22 overlap, the gravel 33 and other particles move into the opening 20. Further rotation of the rotary plate 6 separates the openings 20 and 22, and when the openings 20 and 24 overlap, the gravel and other particles in the opening 20 fall through the opening 24 and are discharged from the bottom of the rotary scraper 2. If gravel and other particles get between the plate 3 and the film 7, or between the plate 4 and the film 8, the films 7 and 8 gradually wear, but the plates 3 and 4 suffer little wear. When the films 7 and 8 wear, the bolts 16 are tightened to prevent leakage of slurry.

[0021] In this embodiment, the amount of gravel discharged per rotation of the rotary plate 6 is determined by the size of the openings 20, 22, allowing a constant amount of gravel to be discharged. The elastic ring 18 and the upper film 8 prevent leakage of slurry. Wear caused by gravel or other particles getting into the gaps between the plates 3, 4 and the films 7, 8 is concentrated on the replaceable films 7, 8, and the wear on the films 7, 8 is compensated for by tightening the bolts 16.

[0022] Figure 4 shows a modified example in which a cleaning nozzle 26 and pump 28 are provided inside or below the lower opening 24. Except where otherwise noted, the embodiment is the same as that shown in Figures 1 to 3, and the same reference numerals represent the same parts. When the openings 24, 20 overlap, a gypsum slurry or the like is sprayed from the nozzle 26 by the pump 28 into the openings 24, 20 to clean the openings 20, 24. Even when the openings 24, 20 do not overlap, spraying the slurry can also clean the gap between the film 7 and the plate 3. This prevents gravel and other particles from getting into the gap between the plates 3, 4 and the films 7, 8.

[0023] It is also possible to equip conventional rotary scrapers with a plate-shaped, self-lubricating member at the tip of the blade that fits tightly against the cylindrical container, preventing gravel from getting into the gap between the blade and the container. However, because the blade rotates around a horizontal axis, gravity acts on the gravel being fed into the container, causing it to get into the gap between the blade tip and the container. This results in faster wear on the blade tip compared to the present invention. Furthermore, even if the blade tip wears out and a gap forms between the blade and the container, it is difficult to adjust.

[0024] The rotary scrapers 2, 2' of the embodiment are suitable for removing not only hard foreign matter having a large specific gravity in the gypsum slurry but also hard foreign matter that has settled and separated from the liquid.

[0025] Figure 5 shows an example of a method for removing high-specific-gravity foreign matter from gypsum slurry. This example is part of a method for recovering gypsum from waste gypsum board. The waste gypsum board is crushed in a crusher 40, and large foreign matter is removed while the crushed pieces are transported on a sorting conveyor 42. The crushed pieces are then pulverized in a crusher 44, and paper chips derived from the gypsum board are separated by sieving. Gravel, sand, small metal objects, etc. are separated using a sieve and a magnetic separator. The gypsum powder that has undergone this pretreatment is calcined in a calciner 46 to produce hemihydrate and / or anhydrous type III gypsum.

[0026] The calcined gypsum powder and an aqueous medium such as a gypsum slurry are mixed in a mixing tank 48, and gypsum particles such as gypsum dihydrate are precipitated in a crystallization tank 50. The precipitated gypsum particles are extracted in a solid-liquid separator 52, and the gypsum slurry is returned to the mixing tank 48 by, for example, a pump 53.

[0027] Although gravel and other foreign matter are separated before calcination, complete separation is difficult. Therefore, when gypsum particles dissolve in the slurry in the crystallization tank 50 and the gypsum is separated from the foreign matter, foreign matter such as gravel, screws, and nails, especially gravel, settles in the slurry. These foreign matter can damage the pump, impeller, and piping. Therefore, the gypsum slurry is supplied to the settling tank 30, for example, by pump 54 or by gravity flow, and the slurry and heavy foreign matter are separated by gravity settling. The gravel and other foreign matter that settle to the bottom of the settling tank 30 are discharged by the rotary scraper 2, and the slurry and heavy foreign matter are separated, for example, by a sieve 36. The slurry is then returned to, for example, the mixing tank 48. In the rotary scraper 2 of this embodiment, the resin films 7 and 8 wear slowly, and even if they do wear, the bolts 16 can be tightened. This allows the gypsum regeneration process to be carried out stably for a long period of time.

[0028] 2, 2' Rotary scraper 3, 4 Plate 6 Rotating plate 7, 8 Resin film 10 Plate 12 Motor 14 Shaft 16 Bolt 17 Nut 18 Elastic ring 20, 22, 24 Opening 25a, b Opening 26 Nozzle 28 Pump 30 Settling tank 32 Opening 33 Gravel 34 Slurry 36 Sieve 40 Crusher 42 Sorting conveyor 44 Pulverizer 46 Calciner 48 Mixing tank 50 Crystallization tank 52 Solid-liquid separator 53, 54 Pump

Claims

1. At least three plates, including an upper plate, a lower plate, and an intermediate plate therebetween, are provided so as to overlap each other in a plan view; each of the at least three plates has an opening extending vertically through the plate; further comprising means for rotating the intermediate plate; each opening is arranged so that, by rotation of the intermediate plate, the state can be switched between a state in which the opening of the upper plate and the opening of the intermediate plate communicate with each other but do not communicate with the opening of the lower plate, and a state in which the opening of the intermediate plate communicates with the opening of the lower plate but do not communicate with the opening of the upper plate; Furthermore, at least two resin films in total are provided between the upper plate and the intermediate plate, and between the intermediate plate and the lower plate; Each resin film is fixed to one of the plates, and each film has an opening that passes through the film from top to bottom and communicates with an opening in the plate to which the film is fixed; The upper and lower plates are larger in diameter than the middle plate. An elastic ring is provided between the upper plate and the lower plate so as to surround the intermediate plate in an annular shape, The rotary scraper further includes a fastening member that applies pressure to the elastic ring and fastens the upper plate and the lower plate together so that the gap between the upper plate and the lower plate can be adjusted.

2. (delete)

3. The rotary scraper of claim 1 is attached to the bottom of a gypsum slurry container, allowing high specific gravity foreign matter in the gypsum slurry to settle at the bottom of the container; introducing the high specific gravity foreign matter from the opening in the bottom of the container to the opening in the upper plate; By rotating the intermediate plate, the high specific gravity foreign matter is moved to the opening of the intermediate plate, and then the high specific gravity foreign matter is discharged to the outside from the opening of the intermediate plate through the opening of the lower plate; By applying pressure to each resin film with the fastening member, foreign matter is prevented from entering the gap between each plate and each film, A method for discharging high-specific-gravity foreign matter from gypsum slurry, in which the spacing between the plates is adjusted using fastening members to prevent gaps from occurring between the plates and the resin film.