JP7713292B2 - How to crush waste gypsum - Google Patents

Description

This invention relates to a method for crushing waste gypsum.

The inventor is considering recovering gypsum from waste gypsum board. Patent Document 1 (JP 2020-65975) shows an example of a method for recovering gypsum. First, the waste gypsum board is crushed, then pulverized to an appropriate particle size, and gypsum particles and paper pieces are separated. The obtained gypsum particles are calcined and then mixed with water to form a gypsum slurry. Dihydrate gypsum is precipitated from this gypsum slurry, and the dihydrate gypsum particles are separated using a solid-liquid separator. The waste gypsum board contains metal foreign objects such as metal fittings and hard foreign objects such as mortar and concrete. Therefore, the metal foreign objects and hard foreign objects in the gypsum slurry are separated based on the difference in specific gravity. Note that the valuable items obtained from the waste gypsum board are dihydrate gypsum and paper pieces. In this specification, the metal foreign objects and hard foreign objects are collectively referred to as heavy foreign objects.

Patent Publication No. 2020-65975

It would be preferable to be able to separate the paper pieces from the gypsum during the process of crushing the waste gypsum. The inventors have confirmed that an impact mill, in which a rotating shaft equipped with a hammer rotates inside a casing, is suitable for this purpose. That is, the waste gypsum board is fed into one end of the casing, where it is crushed by the rotating hammer, and the crushed gypsum chunks are discharged through the mesh of the casing. The paper pieces are difficult to crush, so they do not pass through the mesh, but are sent by the hammer to the other end of the casing where they are discharged.

In addition to gypsum and board paper, waste gypsum board contains heavy foreign objects such as metal pieces such as metal fittings, mortar, and concrete. In order to separate the paper pieces from the gypsum, it is preferable to make the mesh openings small, but such mesh is thin and has limited mechanical strength, making it easily damaged by heavy foreign objects. Furthermore, since the mesh openings are made by punching or other methods, the opening diameter of the mesh is greater than or equal to the thickness of the mesh, and making the openings smaller also reduces the thickness of the mesh.

The objective of this invention is to effectively separate the paper pieces and gypsum when crushing waste gypsum, and to prevent damage to the mesh of the mill used in crushing.

In this invention, waste gypsum is crushed using two mills, a first stage and a second stage. Each mill is equipped with a casing having an inlet at one end and an outlet at the other end, with a mesh between the inlet and the outlet, and rotates a rotary shaft equipped with a hammer inside the casing. In the first stage mill, the mesh opening is 12 mm or more and 30 mm or less, and in the second stage mill, the mesh opening is 3 mm or more and 12 mm or less, and the mesh opening of the second stage mill is smaller than the mesh opening of the first stage mill.
Waste gypsum is fed into the inlet of the first stage mill,
The waste gypsum that passed through the mesh of the first stage mill is fed into the inlet of the second stage mill,
Paper scraps and foreign matter are collected from the outlets of the first and second mills.
The waste gypsum granules are obtained from the mesh of the second mill. The size of these openings is a value empirically determined by the inventor in order to separate the gypsum from the paper pieces while reducing damage to the mesh. The thickness of the mesh is approximately the same as the opening diameter of the mesh.

Preferably, the mesh openings of the first mill are between 14 mm and 20 mm, and the mesh openings of the second mill are between 5 mm and 10 mm. These opening sizes are empirically determined to be optimal ranges for separating the gypsum and the paper pieces while minimizing damage to the mesh.

In this invention, the waste gypsum is crushed with a hammer and separated into paper pieces and gypsum granules. As it moves from the inlet to the outlet, the waste gypsum is repeatedly struck by the hammer, causing the gypsum to fall off from the paper pieces. The first stage mill has a large mesh opening of 12 mm to 30 mm, so the crushed gypsum lumps are quickly discharged from the mesh. In addition, the mesh can be made thick, so damage to the mesh caused by heavy foreign objects can be suppressed. The paper pieces and heavy foreign objects are discharged from the outlet of the first stage mill, and the amount of gypsum adhering to the paper pieces is small. Heavy foreign objects are also mixed into the second stage mill, but since they are small foreign objects that passed through the mesh of the first stage mill, they rarely damage the mesh. The gypsum lumps are further crushed into gypsum granules in the second stage mill, and are separated into the paper pieces, heavy foreign objects, and gypsum granules.

In this invention, waste gypsum is separated into paper chips and gypsum using a two-stage mill equipped with a rotating impact hammer. Here, by setting the mesh openings in the first stage mill to between 12 mm and 30 mm, and in the second stage mill to between 3 mm and 12 mm, the paper chips and gypsum can be sufficiently separated and damage to the mesh can be suppressed.

A process diagram of the recovery of gypsum particles from waste gypsum boards in an example Vertical cross-sectional view of the mill used in the examples Plan view of the mesh in the embodiment Cross-sectional view of the mesh in the embodiment FIG. 13 shows modified examples of mesh openings. FIG. 13 shows a second modified example of mesh openings.

The following are examples of 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. The scope of the present invention is not limited by the examples.

Figures 1 to 6 show a method for crushing waste gypsum board in an embodiment. Figure 1 shows the process from waste gypsum board to recovery of gypsum dihydrate, where the waste gypsum board is fed into the first-stage mill 2 and crushed. If necessary, the waste gypsum board is roughly crushed using a chain crusher or the like before the first-stage mill 2 to a size that can be fed into mill 2. The waste gypsum board is roughly crushed in the first-stage mill 2 and separated into a mixture of paper pieces and heavy foreign matter and gypsum lumps. The gypsum lumps that pass through the mesh of the first-stage mill 2 are fed into the second-stage mill 3, where the gypsum lumps are further crushed to separate the paper pieces from the heavy foreign matter. The paper pieces and heavy foreign matter obtained from mills 2 and 3 are further separated by a specific gravity separator 4 such as a cyclone or vibrating sieve to separate them into gypsum, paper pieces, and heavy foreign matter.

The gypsum granules discharged from the mesh of the second-stage mill 3 are crushed by a crushing device 5 if necessary, or paper pieces and heavy foreign matter are further separated from the gypsum by a specific gravity separator, magnetic separator, etc. The gypsum is temporarily stored in a silo 6 and calcined in a calciner 7 to produce hemihydrate and/or anhydrous type III gypsum. It is then mixed with an aqueous medium in a crystallizer 8 to produce a gypsum slurry, from which gypsum dihydrate particles are precipitated. The gypsum slurry is separated into solid and liquid by a solid-liquid separator 9 such as a filter press, and separated into gypsum dihydrate particles and filtrate, and the filtrate is returned to the crystallizer 8, for example. This invention is directed to crushing waste gypsum using two-stage mills 2 and 3 in series, and other aspects can be modified as appropriate.

Figure 2 shows the structure of the first stage mill 2, and the second stage mill 3 is similar except for the mesh opening size. A number of rows of hammers 12 are attached to the rotating shaft 10, and the striking surface of the hammers 12 is inclined from the axial direction of the rotating shaft 10 to send the waste gypsum from right to left in Figure 2. The rotating shaft 10 is rotated by a motor 14, and 15, 15 are bearings that support the rotating shaft 10. The rotating shaft 10 and the hammers 12 are housed in a casing 16 made of steel, for example, and one end of the casing 16 has an inlet 18 through which waste gypsum board (not shown) is fed. If the waste gypsum board has difficulty passing through the inlet 18, the waste gypsum board is crushed in advance by a chain crusher (not shown) or the like. The other end of the casing 16 has an outlet 19, through which the hammers 12 discharge paper pieces and heavy foreign matter that have not been crushed to a size that can pass through the openings of the mesh 22.

A mesh 22 with many openings is provided, for example, below the casing 16, and the gypsum blocks that are crushed by the hammer 12 to a size that can pass through the openings are discharged from an outlet 21 at the bottom of the cover 20. The mesh 22 may be provided not only below the casing 16 but also around the entire circumference.

Figures 3 and 4 show the openings 25 of the mesh 22. 24 is a metal plate such as steel, and the openings 25 are formed, for example, in a circular shape by punching or the like. The thickness t of the metal plate 24 is approximately the same as the opening diameter D (diameter) of the openings 25. The opening ratio of the mesh 22 (the total area of the openings 25 when viewed from above the mesh 22 divided by the area of the mesh 22 including the openings 25) is, for example, 20% to 50%, and preferably 30% to 40%. The higher the opening ratio, the higher the crushing efficiency, but the lower the strength of the mesh 22.

In the first stage mill 2, the opening diameter D is set to 12 mm or more and 30 mm or less, preferably 14 mm or more and 20 mm or less. If the thickness t of the mesh 22 is set to 12 mm or more, preferably 14 mm or more, it is almost not damaged by hard foreign objects such as metal foreign objects, mortar, concrete, etc. in the waste gypsum board. In addition, since the thickness of the waste gypsum board is often 12.5 mm or 9 mm according to the gypsum board standard, if the opening diameter D is set to 12 mm or more, preferably 14 mm or more, the crushed gypsum lumps can easily pass through the opening 25. The rotary impact hammer 12 crushes the waste gypsum and separates it into paper pieces and gypsum lumps. While the waste gypsum is moving in the casing 16, the gypsum attached to the paper pieces is repeatedly struck and falls off from the paper pieces, and is discharged from the mesh 22, so the amount of gypsum attached to the paper pieces and discharged is small. Empirically, if the opening diameter D is set to 12 mm or more, more than 90% of the gypsum components can be taken out from the opening 25. If the opening diameter D is 30 mm or less, preferably 20 mm or less, the amount of paper scraps and heavy foreign objects entering the second stage mill 3 can be reduced, and large heavy foreign objects can be prevented from entering the second stage mill 3 and damaging the mesh. If the mesh opening of mill 2 is less than 12 mm, not only will the mesh be damaged, but the amount of gypsum discharged from the discharge port 19 along with the paper scraps will increase.

Because the paper pieces are stiff, they are difficult to crush into small pieces, and most of them are discharged from outlet 19. Many of the heavy foreign objects, such as metal fittings, mortar, and concrete, are also discharged from outlet 19. However, some of the paper pieces and heavy foreign objects are fed into the second-stage mill 3 together with the gypsum blocks from outlet 21.

Since large-sized heavy foreign objects are not fed into the second-stage mill 3, the mesh may be thinner than that of the first-stage mill 2. In the second-stage mill 3, the gypsum is repeatedly struck by the hammer 12 while moving from the feed port 18 to the discharge port 19, and the paper pieces and gypsum are further separated from the gypsum block, and the heavy foreign objects are also separated from the gypsum. The gypsum block is then crushed into gypsum granules. In the inventor's experience, if the opening diameter D of the mesh 22 of the second-stage mill 3 is set to 3 mm or more and 12 mm or less, preferably 5 mm or more and 10 mm or less, the paper pieces and heavy foreign objects can be sufficiently separated from the gypsum and damage to the mesh can be prevented. Note that the opening of the mesh of the second-stage mill 3 is made smaller than that of the first-stage mill 2.

The gypsum granules obtained from the second-stage mill 3 may be further pulverized by a pulverizer 5, and after pulverization, other components may be further separated from the gypsum using a magnetic separator, gravity separator, etc.

The size of the openings in the mesh 22 will be explained. For a circular opening 25, the diameter D of the opening is taken as the size of the opening. For openings other than circular, the diameter of the inscribed circle of the opening is taken as the size of the opening. For example, for opening 30 in FIG. 5 and opening 40 in FIG. 6, the diameter D of the inscribed circle shown by the dashed line is taken as the size of the opening.

The following effects can be obtained in the embodiment.
While moving from the inlet 18 to the outlet 19 of the mills 2 and 3, the waste gypsum is repeatedly struck by the rotating hammer 12. The gypsum falls off the paper pieces due to the striking, and the gypsum and the paper pieces can be effectively separated.
By making the mesh opening of the first-stage mill 2 12 mm or more and 30 mm or less, and preferably 14 mm or more and 20 mm or less, the crushed gypsum blocks can be quickly discharged through the mesh, and the mesh can be made thick to prevent damage to the mesh.
By making the mesh openings of the second stage mill 3 3 to 12 mm, preferably 5 to 10 mm, smaller than the mesh openings of the first stage mill, paper pieces and heavy foreign matter can be sufficiently separated from the gypsum. Since large heavy foreign matter has already been separated by the first stage mill 2, the mesh of the second stage mill 3 is unlikely to be damaged even if the mesh openings are made smaller.

2,3 mil
4. Gravity sorting device
5. Crushing equipment
6. Silo
7 Calciner
8. Crystallizer
9 Solid-liquid separator
10 Rotation axis
12 Hammer
14 Motor
15 Bearings
16 Casing
18 Inlet
19 Outlet
20 Cover
21 Exit
22 Mesh
24 Metal plate
25 Aperture
30,40 aperture

Claims (2)

A method for crushing waste gypsum using two mills, a first stage and a second stage, comprising:
Each of the mills has an inlet at one end and an outlet at the other end, and a casing with a mesh between the inlet and the outlet. The mill crushes the waste gypsum by rotating a rotating shaft equipped with a hammer inside the casing.
In either mill, the mesh is a metal plate having a plurality of apertures,
In the first stage mill, the mesh opening is set to 12 mm or more and 30 mm or less,
In the second stage mill, the mesh opening is set to 3 mm or more and 12 mm or less, and the mesh opening of the second stage mill is smaller than the mesh opening of the first stage mill;
Waste gypsum is fed into the inlet of the first stage mill,
The waste gypsum that passed through the mesh of the first stage mill is fed into the inlet of the second stage mill,
Paper scraps and foreign matter are collected from the outlets of the first and second mills.
A method for crushing waste gypsum, comprising obtaining waste gypsum granules through the mesh of the second stage mill. In the first stage mill, the mesh opening is set to 14 mm or more and 20 mm or less,
2. The method for crushing waste gypsum according to claim 1, wherein the opening of the mesh in the second stage mill is set to be 5 mm or more and 10 mm or less.