Method for recovering slips of paper and gypsum grains from waste gypsum board

Abstract

To separate gypsum grains from slips of paper while suppressing generation of slips of paper caused by crushing in recovery of slips of paper and gypsum grains from a waste gypsum board.CONSTITUTION: After crushing of a waste gypsum board, the crushed articles are separated into a sieve upper slip of paper and a sieve lower component through a first sieve. The sieve lower component of the first sieve is crushed by a crushing machine. The sieve lower component crushed by the crushing machine is sieved through a second sieve, and separated into a sieve upper component containing a mixture of a slip of paper and gypsum grains and a sieve lower component containing gypsum grains. The sieve upper component of the second sieve is put on the conveyance surface of a belt conveyor which moves obliquely upward, the slip of paper is conveyed upward together with the conveyance surface of the belt conveyor to be recovered from an upper part of the belt conveyor, and the gypsum grains are rolled downward on the conveyance surface to be recovered from a lower part of the belt conveyor.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for separating and recovering paper chips and gypsum particles from waste gypsum board. [Background technology]

[0002] The inventors have commercialized the recovery of gypsum powder and paper from waste gypsum board. First, the waste gypsum board is crushed to produce paper chips and gypsum granules. Next, the paper chips are recovered as an oversized component using a sieve such as a vibrating sieve, and the gypsum granules are recovered as an undersized component. The gypsum granules are further crushed and sieved into paper chips and gypsum granules. The gypsum granules are converted into hemihydrate and / or anhydrous type III gypsum by calcination, which is then dissolved in a gypsum slurry in a mixing tank, and gypsum powder such as gypsum dihydrate is precipitated in a crystallization tank. The precipitated gypsum powder is filtered, and the filtrate is returned to the mixing tank, for example. Through the above process, paper chips and gypsum powder can be recovered from waste gypsum board. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2023-00603 Summary of the Invention [Problem to be solved by the invention]

[0004] When the material is sieved after crushing, large gypsum particles remain in the sieved components. If the gypsum particles are mixed with the paper pieces, the value of the paper pieces decreases. Therefore, if the crushing is intensified, paper powder is generated, which mixes with the gypsum particles and reduces the purity of the gypsum particles. It is difficult to sufficiently separate the paper pieces from the gypsum particles while suppressing the generation of paper powder using only crushing and sieving.

[0005] An object of the present invention is to separate the gypsum particles from the paper chips while suppressing the generation of paper dust due to pulverization when recovering the paper chips and gypsum particles from waste gypsum board. [Means for solving the problem]

[0006] The method for recovering paper chips and gypsum particles from waste gypsum boards of the present invention includes the steps of crushing the waste gypsum boards and then separating the crushed gypsum boards into paper chips that pass through a first sieve and an under-sieve component; A step of crushing the undersize component of the first sieve using a crusher; A step of sieving the under-sieve component pulverized by the pulverizer using a second sieve to separate it into an over-sieve component consisting of a mixture of paper pieces and gypsum granules and an under-sieve component consisting of gypsum granules; The remaining components on the second sieve are fed onto the conveying surface of a belt conveyor whose conveying surface moves diagonally upward, the paper pieces are conveyed upward together with the conveying surface of the belt conveyor and collected from the top of the belt conveyor, and the gypsum granules are rolled diagonally downward on the conveying surface and collected from the bottom of the belt conveyor.

[0007] In this invention, flat paper pieces that have high friction with the belt are transported diagonally upward along the conveying direction on the conveying surface of the belt conveyor and can be collected from the top of the belt conveyor. Gypsum granules, which are bulkier than paper pieces, roll on the conveying surface of the belt conveyor, and because they are soft, the corners are cut off by rolling, forming a shape that is closer to a sphere, making them easier to roll. As a result, the gypsum granules can be collected, for example, from the bottom of the belt conveyor. In this invention, the paper pieces and gypsum granules can be separated by the belt conveyor. This separation does not involve crushing the paper pieces, so the amount of paper powder mixed into the gypsum granules does not increase.

[0008] Preferably, the gypsum granules collected from the bottom of the belt conveyor are re-ground in a grinder together with the under-sieve component of the first sieve. The re-ground gypsum granules are then sieved through a second sieve. Since the gypsum granules collected from the bottom of the belt conveyor tend to have large particle sizes, re-grounding them makes it possible to make the particle sizes uniform with the gypsum granules that initially passed through the second sieve.

[0009] Particularly preferably, the sieve is a vibrating sieve with openings of 6 mm to 12 mm. If the openings are less than 6 mm, clogging is likely to occur when processing waste gypsum board wet with rainwater, etc. If the openings are more than 12 mm, a large amount of paper fragments will be mixed in with the undersize component. [Brief explanation of the drawings]

[0010] [Figure 1] Process diagram from crushing waste gypsum board to recovering gypsum powder in an example [Figure 2] FIG. 10 is a diagram showing separation of paper pieces and gypsum granules by a belt conveyor in an embodiment. [Figure 3] Photographs showing paper pieces (FIG. 3(A)) and gypsum granules (FIG. 3(B)) separated in the example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Examples for carrying out the present invention are shown below. 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. The scope of the present invention is not limited by the examples. [Example]

[0012] Examples are shown in Figures 1 to 3. In this specification, the opening (mesh size) of a sieve is the diameter of the opening if the opening is circular, the length of one side if the opening is square, and the root of the product of the lengths of the short side and the long side if the opening is rectangular.

[0013] Figure 1 shows an example of recovering paper chips and gypsum dihydrate powder from waste gypsum board. At a minimum, it is sufficient to crush and pulverize the waste gypsum board and separate the paper chips from the gypsum granules; subsequent calcination and crystallization are not required. In Figure 1, the waste gypsum board is crushed using a crusher 2 to produce paper chips and gypsum granules. The crusher can be of any type. The paper chips and gypsum granules obtained by crushing are fed into a first sieve 4, such as a vibrating sieve, and separated into the oversized paper chips and the undersized component (mainly gypsum granules, including the paper chips).

[0014] The undersize fraction obtained from sieve 4 is fed into crusher 5, and the crushed gypsum granules are sieved using second sieve 8, which may be a vibrating sieve or the like. The type of crusher 5 is arbitrary. The undersize fraction of sieve 8 is mostly gypsum and is fed into calciner 10. The oversize fraction of sieve 8 includes paper chips and gypsum granules and is fed into belt conveyor 6. The paper chips are collected from the top of belt conveyor 6, and gypsum granules with slightly larger particle sizes are collected from the bottom and fed back into crusher 5. Processing using belt conveyor 6 allows the paper chips and gypsum granules to be separated, and almost no paper dust is generated.

[0015] The openings of the second sieve 8 are preferably 6 mm or more and 12 mm or less. If the openings are less than 6 mm, clogging is likely to occur when processing waste gypsum board wet with rainwater, etc. If the openings are more than 12 mm, a large amount of paper fragments will be mixed in with the under-sieve component. The openings of the first sieve 4 are made larger than the openings of the second sieve 8.

[0016] In order to separate metal pieces such as nails, gravel, sand and other non-magnetic foreign matter mixed in with the waste gypsum board, it is preferable to carry out a process for separating metallic foreign matter, non-magnetic foreign matter, etc. at an appropriate location, for example, between the crusher 2 and the calciner 10.

[0017] In the calciner 10, the gypsum granules are calcined to produce hemihydrate and / or anhydrous type III gypsum, which is then mixed with water such as a gypsum slurry in a mixing tank 12, and for example, gypsum dihydrate particles are precipitated in a crystallization tank 14. A filter 16 recovers gypsum dihydrate powder and the like from the gypsum slurry in the crystallization tank 14, and the filtrate is returned to, for example, the mixing tank 12. Note that in the crystallization tank 14, other gypsum such as hemihydrate may be precipitated instead of gypsum dihydrate.

[0018] The separation of paper chips and gypsum granules by a belt conveyor 6 will be explained with reference to Figure 2. The belt conveyor 6 drives an endless belt 20 with a pair of pulleys 22, 22, for example, one of which is a drive pulley and the other a driven pulley. The endless belt 20 is, for example, a flat belt made of natural rubber with teeth on its backside that mesh with the teeth of the pulley 22. The endless belt 20 may be a low-friction steel belt, a stepped belt with horizontal protrusions to increase friction with the conveyed material, or a flat belt with upward protrusions on both sides, and the shape and material of the endless belt 20 are optional.

[0019] The conveying surface 21 of the endless belt 20 conveys clumps of gypsum particles 24 and paper chips 26. The conveying direction of the endless belt 20 (hereinafter referred to as "belt 20") is diagonally upward. In the case of a flat belt made of natural rubber, the inclination angle for separating the paper chips from the gypsum particles is preferably 7° or more and 30° or less. The inclination angle is made smaller for belts with low friction such as steel belts, and larger for stepped belts with high friction. The inclination angle was empirically determined so that the paper chips rise with the belt 20 and the gypsum particles roll down on the belt 20.

[0020] The oversized component is charged onto the belt 20, for example, from a chute 28, and the charge position is preferably between the center position in the longitudinal direction of the belt 20 and a position in the lower half position in the longitudinal direction of the belt 20 so that the gypsum granules do not move to the upper end of the belt conveyor 6. A skirt or the like may be provided at the lower end of the chute 28 to prevent paper pieces from scattering.

[0021] When the sieved components are fed onto the conveying surface 21, the flat paper pieces 26, which have high friction with the belt 20, are conveyed diagonally upward along the conveying direction and are collected, for example, from the upper end of the conveyor 6. The gypsum granules 24, which are bulkier than the paper pieces 26, roll on the conveying surface 21, and because they are soft, their corners are cut off and they become nearly spherical, making them easier to roll. As a result, the gypsum granules 24 can be collected, for example, from the lower end of the conveyor 6. Most of the gypsum powder generated by the corners of the gypsum granules 24 being cut off is also collected from the lower end of the conveyor 6. The paper pieces 26 and gypsum granules 24 can be collected by free fall from the end of the belt 20 or by vacuum suction, etc.

[0022] The gypsum granules collected from the conveyor 6 have a large particle size, and are therefore pulverized in a pulverizer 5 together with the undersize component of the first sieve 4 .

[0023] Figure 3(A) shows paper scraps collected from the top of the conveyor 6, and Figure 3(B) shows gypsum granules collected from the bottom of the conveyor 6. The gypsum granules have rounded corners and are easy to roll. This makes it easy to separate and collect the paper scraps and gypsum granules. [Explanation of symbols]

[0024] 2 Crusher 4,8 sieve 5. Crusher 6. Belt conveyor 10 Calciner 12 Mixing tank 14 Crystallization tank 16 Filter 20 endless belt 21 Conveying surface 22 Pulley 24 Gypsum granules 26 piece of paper 28 shots

Claims

1. After crushing the waste gypsum board, separating it into paper pieces on the sieve and an under-sieve component using a first sieve; A step of crushing the undersize component of the first sieve using a crusher; A step of sieving the under-sieve component pulverized by the pulverizer using a second sieve to separate it into an over-sieve component consisting of a mixture of paper pieces and gypsum granules and an under-sieve component consisting of gypsum granules; The method for recovering paper chips and gypsum granules from waste gypsum boards includes the steps of: feeding the remaining components of the second sieve onto the conveying surface of a belt conveyor whose conveying surface moves obliquely upward; conveying the paper chips upward together with the conveying surface of the belt conveyor and recovering them from the upper part of the belt conveyor; and rolling the gypsum granules obliquely downward on the conveying surface and recovering them from the lower part of the belt conveyor.

2. The method for recovering paper chips and gypsum granules from waste gypsum boards according to claim 1, characterized in that in the crushing step, the gypsum granules recovered from the bottom of the belt conveyor are re-crushed by the crusher together with the undersize components of the first sieve.

3. 3. The method for recovering paper chips and gypsum particles from waste gypsum boards according to claim 2, wherein the second sieve is a vibrating sieve having openings of 6 mm or more and 12 mm or less.

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