Method for mixing gypsum particles derived from waste gypsum board and gypsum slurry, and mixing device

Abstract

To suppress generation of gypsum scale in a device for mixing gypsum granular material and gypsum slurry derived from a waste gypsum board.CONSTITUTION: A mixing method for gypsum granular material and gypsum slurry derived from waste gypsum boards comprises: feeding hemihydrate and / or anhydrous type III gypsum granular material derived from waste gypsum boards into a flow passage of an aqueous gypsum slurry containing gypsum dihydrate; mixing the gypsum granular material; and supplying the gypsum slurry to a precipitation tank. The method supplies the gypsum slurry from an inlet of a flow passage, feeds, from above into the gypsum slurry, the hemihydrate and / or anhydrous type III gypsum granular material derived from waste gypsum boards, and after feeding the gypsum granular material, with an upper liquid surface of the gypsum slurry being always exposed to air, causes the gypsum slurry to flow to an outlet of the flow passage. The method causes the gypsum slurry to freely fall from the outlet of the flow passage to feed it into a pipe, and causes the gypsum slurry to collide against a surface on a far side as viewed from the outlet of the pipe, to fall down, or to fall down through a center part of the pipe.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This invention relates to the mixing of gypsum particles derived from waste gypsum board and gypsum slurry.

Background Art

[0002] The inventors have been considering the recovery of gypsum dihydrate from waste gypsum board. In Patent Document 1 (Patent No. 6336385), using the cylindrical mixing device 40 shown in FIG. 5, after crushing the waste gypsum board and heating it to obtain gypsum particles in the form of hemihydrate and / or anhydrous type III, the gypsum particles are introduced into the gypsum slurry 44 from the inlet 41. Further, a slurry containing gypsum dihydrate is supplied from the slurry inlet 42 on the side surface of the cylinder in the tangential direction of the cylinder, and the slurry is discharged from the slurry outlet 43 to the crystallization tank. By swirling the slurry 44 in the mixing container 40, entrainment of air into the slurry 44 is prevented. As a result, cavitation can be prevented when the slurry is pumped out from the mixing container 40 to the crystallization tank by a fluid pump. In order to prevent the occurrence of a stagnant area in the central part of the mixing container 40, a pipe 45 is provided in the central part, and an exhaust port 47 is provided to prevent the pressure inside the container from rising.

[0003] However, in the mixing device 40 of FIG. 5, it has been found that a scale 46 of gypsum is likely to occur from the bottom to the side of the container. The scale 46 adheres to the inner wall of the mixing device 40 and is extremely hard. It is inefficient to periodically interrupt operation to remove the scale.

[0004] The related prior art is shown. The inventors proposed in Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2020-105045) to suppress the generation of crystal nuclei by shortening the residence time of the slurry in the mixing device and increase the particle size of the recovered gypsum dihydrate. It was also described that the mixer is, for example, cylindrical, but it may also be in the form of a trough or the like.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] An object of the present invention is to suppress the generation of a gypsum scale in an apparatus for mixing gypsum particles derived from waste gypsum board and a gypsum slurry. [Means for Solving the Problems]

[0007] The present invention is a method of introducing hemihydrate and / or anhydrous type III gypsum particles derived from waste gypsum board into a flow path of an aqueous gypsum slurry containing dihydrate gypsum, mixing the gypsum particles and the gypsum slurry, and supplying them to a precipitation tank for dihydrate gypsum, supplying the gypsum slurry from an inlet of the flow path, introducing the gypsum particles into the gypsum slurry from above, and after introducing the gypsum particles, flowing the gypsum slurry to an outlet of the flow path while constantly exposing the liquid surface at the upper part of the gypsum slurry to air, causing the gypsum slurry to freely fall from the outlet of the flow path into a pipe, and causing the gypsum slurry to collide and fall on the surface on the far side of the pipe as viewed from the outlet, or to fall through the central part of the pipe, and preventing it from falling along the surface on the near side of the pipe as viewed from the outlet.

[0008] The mixing apparatus of the present invention is an apparatus for mixing hemihydrate and / or anhydrous type III gypsum particles derived from waste gypsum board with an aqueous gypsum slurry containing dihydrate gypsum and supplying them to a precipitation tank for dihydrate gypsum, comprising a flow path for the gypsum slurry and a pipe, wherein the flow path is configured to supply the gypsum slurry from an inlet of the flow path, introduce the gypsum particles into the gypsum slurry from above, and after introducing the gypsum particles, flow the gypsum slurry to an outlet of the flow path while constantly exposing the liquid surface at the upper part of the gypsum slurry to air. The pipe is configured to allow the gypsum slurry to fall freely from the outlet of the flow path and enter the pipe, and to cause the gypsum slurry to collide with and fall on the surface of the pipe on the far side as viewed from the outlet, or to fall through the central portion of the pipe, and not to fall along the surface of the pipe on the near side as viewed from the outlet.

[0009] Gypsum scale is very hard and difficult to remove in the form of an annular scale. In contrast, when the scale adheres only to a part rather than the entire circumference of the flow path or the pipe, the scale can be easily peeled off. If the upper part of the slurry is constantly exposed to air in the flow path, annular scale will not adhere to the flow path. Also, when the slurry is made to collide with the far side surface of the pipe or the slurry falls through the central portion of the pipe, scale will not be generated annularly around the entire 360 degrees inside the pipe. Therefore, in this invention, the gypsum scale adhering to the mixing device can be easily removed.

[0010] Preferably, the flow path is linear. In the embodiment, the flow path has a U-shaped cross-section, but it may also be pipe-shaped. It is important that the upper liquid level of the slurry is constantly exposed to air. Also, between the pipe and the crystallization tank, at a surface perpendicular to the flow, no location is provided where the slurry flows over the entire 360 degrees of the circumference of the flow path or the pipe. In a flow path with an open upper surface, the upper part of the slurry is constantly exposed to air, and inside the pipe, the slurry flows along only a part of the inner wall or through the central portion of the pipe.

[0011] The cross-section of the flow path is preferably a curved surface such as a U-shape rather than a quadrilateral with a corner at the bottom corner. If there is a corner in the cross-section of the flow path at a height lower than the liquid level of the slurry, the slurry is likely to stagnate and scale is likely to occur. Further, it is preferable that the cross-sectional shape of the flow path is constant at a height below the liquid level of the slurry from the input location of the gypsum particles to the outlet, more preferably from the inlet to the outlet of the flow path. If the cross-sectional shape changes, the slurry is likely to stagnate and scale is likely to occur. Similarly, a circular pipe is preferable to a square pipe for the pipe, and it is preferable that the thickness of the pipe is constant. In a square pipe, scale is likely to occur at the corners of the pipe, and scale is likely to occur even if the thickness changes.

[0012] Note that passing the gypsum particles through the mixing device instead of directly introducing them into the crystallization tank means limiting the location where scale is generated to the mixing device. In the present invention, when the slurry mixed with the gypsum particles reaches the crystallization tank, the supersaturation decreases, so scale does not occur.

[0013] Preferably, the inner surfaces of the flow path and the pipe are covered with a fluororesin film or plate to slow the growth of gypsum scale. The fluororesin film or plate can be used for a long time even in the gypsum slurry. Also, since the fluororesin film or plate is less likely to have gypsum scale adhere to it, the growth of scale can be slowed down.

[0014] Preferably, while supplying the gypsum slurry from the supply pipe to the flow path, the cross-sectional area of the flow path at the inlet of the flow path is made larger than the cross-sectional area of the supply pipe, so that the upper part of the gypsum slurry in the flow path is exposed to air. The cross-sectional area of the flow path here refers to the maximum cross-sectional area through which the slurry can flow, not the cross-sectional area of the slurry. For example, if the flow path is a pipe, it refers to the cross-sectional area inside the pipe. Even if the supply pipe is completely occupied by the slurry, the upper part of the slurry can be exposed to air in a flow path with a large cross-sectional area.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0016] Examples for carrying out the present invention are shown below. The scope of this invention should be determined in accordance with the understanding of those skilled in the art, taking into account the description in the claims, the description in the specification, and well-known techniques in this field. The scope of this invention is not limited by the examples.

Examples

[0017] Examples are shown in Figures 1 to 4. Figure 1 shows a recovery system 2 of gypsum dihydrate from waste gypsum board. The waste gypsum board composed of cardboard and gypsum dihydrate is crushed by a crusher 4, and the cardboard pieces and gypsum dihydrate are separated by a sieve 4. The gypsum dihydrate is heated by a heating device 5 to form hemihydrate and / or anhydrous type III gypsum granules.

[0018] The mixing device 6 of the embodiment is composed of a flow path 7 and a pipe 8. Gypsum granules are introduced into the aqueous slurry of gypsum dihydrate in the flow path 7, and the gypsum slurry is supplied from the pipe 8 to a crystallization tank 10. Gypsum dihydrate crystals are grown in the crystallization tank 10, and the gypsum powder is separated from the gypsum slurry by a solid-liquid separation device 12 such as a filter press via a fluid pump 11. Then, the gypsum slurry is circulated to the flow path 7.

[0019] Figures 2 to 4 show the structures of the flow path 7 and the pipe 8. The flow path 7 may include a location where the flow of the aqueous slurry 23 containing dihydrate gypsum bends, but is preferably linear. In Figure 2, the flow path 7 is shown horizontally, but in actuality, it slopes downward from the inlet 25 to the outlet 30 to prevent foreign matters such as gravel from accumulating. The vertical cross-section perpendicular to the flow direction of the flow path 7 is, for example, U-shaped. As shown in Figure 3, the flow path 7 consists of a flow path body 20 with a U-shaped cross-section (e.g., made of stainless steel) and a lining 21 made of fluororesin. The lining 21 may be in the form of a film or a plate. The upper part of the flow path 7 is covered with, for example, a tread plate 22. It should be noted that the flow path 7 may be in the form of a pipe, and the slurry may flow through the lower 1 / 2 to 1 / 4 of the cross-section, with air always present above the slurry.

[0020] The lining 21 made of fluororesin can slow down the growth of gypsum scale. Also, the lining 21 made of fluororesin has high durability in the gypsum slurry and can be used for, example, more than one year. In contrast, the lining made of soft vinyl chloride resin, etc., has a lifespan of about half a year in the gypsum slurry. It should be noted that the lining 21 may not be provided.

[0021] The slurry 23 is supplied from the pipe 24, and the joint between the pipe 24 and the flow path 7 is the inlet 25 of the flow path 7. Also, hemihydrate and / or anhydrous type III gypsum granules are introduced into the flow path 7 from a feeding device 26 such as a screw conveyor. 27 is the motor of the feeding device 26, and 28 is the inlet. The velocity distributions of the slurry in the pipe 24 and the flow path 7 are schematically shown in Figure 2. The inlet 28 is provided upstream of the center of the flow direction of the flow path 7 to promote the mixing of the gypsum granules and the slurry. The gypsum slurry 23 flows at the bottom of the flow path 7, and the liquid level 32 of the slurry 23 is always exposed to the air 34, so that scale does not form annularly in the flow path 7. It should be noted that the diameter of the pipe 24 is, for example, 100 mm to 200 mm, the diameter of the flow path 7 is about twice the diameter of the pipe 24, and the average flow velocity of the slurry 23 in the flow path 7 is, for example, 2 to 4 m / s.

[0022] From the outlet 30 of the flow path 7, the slurry 23 freely falls into the pipe 8 and collides with the side surface on the side opposite to the flow path 7 of the pipe 8 and falls due to the high flow velocity. It is also preferable to cover the inner surface of the pipe 8 with an inner lining 31 made of a fluororesin film or a pipe. Although droplets of the slurry adhere to each part inside the pipe 8, as shown by the dashed-dotted line in Fig. 4, the slurry 23 does not flow expanding 360 degrees around the inner circumference of the pipe 8. And just by the adhesion of the droplets, the scale does not grow annularly without gaps. Note that the diameter of the pipe 8 may be increased and the center part of the pipe 8 may be arranged such that the slurry 23 falls. The diameter of the pipe 8 is, for example, about the same as the diameter of the flow path 7, and the orientation of the pipe 8 is not limited to vertical.

[0023] The gypsum slurry flows from the pipe 8 into the crystallization tank 10. Note that between the pipe 8 and the crystallization tank 10, there may be a flow path where the upper part of the liquid surface is always exposed to air, or a pipe different from the pipe 8, etc.

[0024] In the embodiment, there are the following effects. 1) It is possible to prevent the gypsum scale from adhering annularly in the mixing device 6. The gypsum scale is strong, but if it is not annular, it can be easily peeled off. 2) The inner linings 21, 31 made of fluororesin slow down the growth of the gypsum scale. The inner linings 21, 31 made of fluororesin have higher durability in the gypsum slurry compared to, for example, soft vinyl chloride resin. 3) Connect a large-diameter flow path 7 to the pipe 24 and ensure that the liquid surface of the slurry is always exposed to air in the flow path 7.

Explanation of reference numerals

[0025] 2 Recovery system of gypsum dihydrate 3 Crusher 4 Sieve 5 Heating device 6 Mixing device 7 Flow path 8 Pipe 10 Crystallization tank 11 Fluid pump 12 Solid-liquid separation device 20 Flow path body 21, 31 Inner expansion 22 Pedal 23 Gypsum slurry 24 Pipe 25 Entrance 26 Feeding device 27 Motor 28 Inlet 30 Exit 32 Liquid level 34 Air

Claims

1. A method of introducing hemihydrate and / or anhydrous type III gypsum particles derived from waste gypsum board into a flow path of an aqueous gypsum slurry containing dihydrate gypsum, mixing the gypsum particles and the gypsum slurry, and supplying them to a precipitation tank of dihydrate gypsum, comprising: supplying the gypsum slurry from the inlet of the flow path, introducing the gypsum particles into the gypsum slurry from above, and after introducing the gypsum particles, flowing the gypsum slurry to the outlet of the flow path while constantly exposing the liquid surface at the upper part of the gypsum slurry to air; causing the gypsum slurry to freely fall from the outlet of the flow path and be introduced into a pipe, and causing the gypsum slurry to collide and fall on the surface far from the outlet of the pipe as seen from the outlet, or to fall through the central part of the pipe, and preventing it from falling along the surface near the outlet of the pipe as seen from the outlet. A method for mixing gypsum particles derived from waste gypsum board and a gypsum slurry.

2. The method for mixing gypsum particles derived from waste gypsum board and a gypsum slurry according to Claim 1, wherein the inner surfaces of the flow path and the pipe are covered with a fluororesin film or plate to slow down the growth of gypsum scale on the inner surfaces.

3. The method for mixing gypsum particles derived from waste gypsum board and a gypsum slurry according to Claim 1 or 2, wherein the gypsum slurry is supplied to the flow path from a supply pipe, and the cross-sectional area of the flow path at the inlet is made larger than the cross-sectional area of the supply pipe, so as to expose the upper part of the gypsum slurry in the flow path to air.

4. A mixing device for mixing hemihydrate and / or anhydrous type III gypsum particles derived from waste gypsum board with an aqueous gypsum slurry containing dihydrate gypsum and supplying them to a precipitation tank of dihydrate gypsum, comprising: a flow path for the gypsum slurry and a pipe; the flow path is configured to supply the gypsum slurry from the inlet of the flow path, introduce the gypsum particles into the gypsum slurry from above, and after introducing the gypsum particles, flow the gypsum slurry to the outlet of the flow path while constantly exposing the liquid surface at the upper part of the gypsum slurry to air; the pipe is configured to cause the gypsum slurry to freely fall from the outlet of the flow path and be introduced into the pipe, and cause the gypsum slurry to collide and fall on the surface far from the outlet of the pipe as seen from the outlet, or to fall through the central part of the pipe, and prevent it from falling along the surface near the outlet of the pipe as seen from the outlet. A mixing device.

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