Method for crushing waste gypsum board and silo used for the same

Abstract

To smoothly take out gypsum granules from a silo when storing gypsum granules obtained by crushing a waste gypsum board in a silo.CONSTITUTION: A waste gypsum board is crushed into gypsum granules and stored in a silo. A plurality of screw conveyors is provided at a bottom of the silo, and the gypsum granules in the silo are discharged to the outside of the silo by a screw conveyor.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This invention relates to the crushing of waste gypsum boards and a silo used for the crushing. [Background technology]

[0002] The inventors have proposed a method for recovering gypsum from waste gypsum board (for example, Patent Document 1: WO2012 / 176688). Waste gypsum board consists of a gypsum board and a paper surface, and may contain foreign matter such as metal. In Patent Document 1, the waste gypsum board is first roughly crushed using a cutter. The crushed waste gypsum board is transported on a belt conveyor, and foreign matter such as metal is visually removed on the belt conveyor. Next, the roughly crushed waste gypsum board is crushed into gypsum granules using a four-axis roll crusher, and the waste gypsum board is separated into paper pieces and gypsum granules using a sieve in the subsequent stage. In addition, before and after processing with the four-axis roll crusher, metal foreign matter is further removed using a magnetic separator.

[0003] The resulting gypsum granules are calcined and converted into, for example, gypsum hemihydrate. The converted gypsum hemihydrate or the like is mixed with gypsum slurry, and gypsum particles such as gypsum dihydrate are precipitated in a closed-loop crystallization tank. The precipitated gypsum particles are separated from the slurry by solid-liquid separation, allowing the gypsum particles to be recovered from the waste gypsum board. The recovered gypsum particles can be recycled into gypsum board or used as a cement raw material, etc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2012 / 176688 Summary of the Invention [Problem to be solved by the invention]

[0005] When crushing waste gypsum board, it is preferable to store the gypsum granules obtained by crushing in a silo. However, the gypsum granules recovered from the waste gypsum board tend to coagulate due to moisture, making it difficult to discharge the gypsum granules from the silo by gravity. Furthermore, the gypsum granules in the silo often form bridges (a phenomenon known as "hanging") and tend to harden on the inner walls of the silo. When waste gypsum board gets wet at a building demolition site, for example, hanging and hardening become particularly likely to occur.

[0006] An object of the present invention is to make it possible to smoothly remove gypsum granules obtained by crushing waste gypsum boards from a silo when storing the gypsum granules in the silo. [Means for solving the problem]

[0007] The method for crushing waste gypsum board of this invention includes a crushing step of crushing the waste gypsum board into gypsum granules and a storage step of storing the gypsum granules obtained in the crushing step in a silo. The method for crushing waste gypsum board of this invention is characterized in that in the storage step, the gypsum granules in the silo are discharged to the outside of the silo by a plurality of screw conveyors provided at the bottom of the silo.

[0008] The silo of this invention is a silo for storing gypsum granules made from crushed waste gypsum board. The silo of this invention is characterized by having a plurality of screw conveyors at the bottom so as to discharge the gypsum granules inside the silo to the outside of the silo. Note that in this specification, the description of the method for crushing waste gypsum board also applies to a waste gypsum board crushing system consisting of a silo, etc.

[0009] Gypsum granules in a silo lose fluidity due to coagulation, and may not be able to be discharged from the silo by natural gravity. In this invention, the gypsum granules are forcibly discharged using a screw conveyor at the bottom of the silo. The use of a screw conveyor allows for discharge even when the fluidity of the gypsum has decreased. Furthermore, in order to discharge the gypsum granules from almost the entire bottom of the silo, multiple screw conveyors are installed at the bottom of the silo. This allows for the gypsum granules to be discharged from almost the entire bottom of the silo.

[0010] Preferably, the inner wall of the silo is tilted from the vertical direction toward the inside of the silo. This means that the bridge of gypsum particles can no longer be supported by friction with the inner wall of the silo, and the bridge naturally collapses. Furthermore, even if gypsum adheres to the inner wall of the silo, gravity makes it easy for the gypsum to peel off from the inner wall. The above mechanisms prevent gypsum from hanging inside the silo and also prevent gypsum from adhering to the inner wall.

[0011] Preferably, the gypsum granules discharged by the multiple screw conveyors are collected by another screw conveyor and discharged outside the silo. Since multiple screw conveyors are used, the gypsum granules are discharged through slits or long holes of a certain length. If the discharged gypsum granules were discharged using a hopper or the like, additional space would be required and the gypsum granules may solidify in the hopper. Therefore, preferably, the gypsum granules are collected in one place by another screw conveyor and discharged.

[0012] Preferably, in the storage step, when the inner diameter of the bottom of the silo is D and the storage height of the gypsum granules is H, the gypsum granules are stored in the silo so that the inner diameter D is equal to or greater than the height H. If the height H is greater than the inner diameter D, the gypsum granules are likely to solidify in the silo.

[0013] A preferred embodiment of the crushing step will be described. When removing foreign matter such as metal by visual inspection on the conveyor, the foreign matter may be covered by gypsum particles produced by crushing. This may make the foreign matter invisible and difficult to remove. Therefore, after crushing the waste gypsum board with a crusher, the crushed waste gypsum board is sieved. The fine gypsum particles produced by crushing are then separated below the sieve. When the oversized components that did not pass through the sieve are transported by a belt conveyor, the foreign matter is easily visible, making it easier to remove the foreign matter on the belt conveyor.

[0014] The gypsum particles obtained by roughly crushing waste gypsum board are large in size and can be called crushed pieces or coarse particles. It is preferable to crush these gypsum particles into small pieces using a fine crusher to reduce the size to a size suitable for downstream processing. At this time, it is necessary to supply the crushed waste gypsum board to the fine crusher in predetermined amounts. Therefore, a fixed-volume conveyor is preferably used, which has a belt, multiple plates attached to the belt so as to stand upright, and side panels on both sides of the belt, and transports the gypsum particles diagonally upward. The gypsum particles are supplied from the upstream belt conveyor to the fixed-volume conveyor, and then supplied to the fine crusher while the amount of gypsum particles is regulated by the plates. In the fixed-volume conveyor, the amount of gypsum particles per stage is determined by the plates and the side panels on both sides, so the gypsum particles are supplied to the fine crusher in predetermined amounts. Therefore, the gypsum particles do not overflow from the fine crusher.

[0015] Before supplying the gypsum granules to the silo, foreign matter is removed on a belt conveyor, and metal foreign matter is removed before and after fine crushing using a magnetic separator or the like. However, small metal pieces such as screws and nails may still pass through both the belt conveyor and the magnetic separator. Therefore, preferably, the gypsum granules after being crushed by the fine crusher are supplied to a pipe, and the gypsum granules are transported to the silo by airflow due to the pressure difference between both ends of the pipe. A magnet is then attached to the pipe, and magnetic particles such as metal pieces are separated from the gypsum granules by magnetic force. Magnetic particles flowing through the pipe on the airflow are not covered by the gypsum granules and are therefore easily attracted to the magnet. In this way, small magnetic particles that are easily embedded in the gypsum granules are removed. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram showing an outline of a method for recovering gypsum from waste gypsum board in an embodiment. [Figure 2] A process diagram showing the process from crushing waste gypsum board to storing it in a silo in an example. [Figure 3] Schematic diagram of a fixed-volume conveyor used in the crushing method of the embodiment [Figure 4] Schematic diagram of a conveying pipe with magnetic separation function used in the crushing method of the embodiment [Figure 5] Schematic vertical cross-sectional view of a silo used in the crushing method of the embodiment [Figure 6] Schematic plan view of the bottom of the silo in Figure 5 DETAILED DESCRIPTION OF THE INVENTION

[0017] 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]

[0018] 1 to 6 show examples. FIG. 1 shows the overall method for recovering gypsum from waste gypsum board. In pretreatment step 2, the waste gypsum board is crushed and the resulting gypsum granules are stored in a silo 40. In the subsequent calcination step 4, the gypsum granules are calcined to convert them into granules such as gypsum hemihydrate and anhydrous type III gypsum. In crystallization step 6, the calcined gypsum granules are mixed with a gypsum slurry, etc., and gypsum particles such as gypsum dihydrate are precipitated in a crystallization tank. In the final filtration step 8, the gypsum slurry is sieved to remove paper powder, etc., and then the gypsum slurry is treated in a filter to separate the gypsum powder. Note that this invention relates to pretreatment step 2.

[0019] Pretreatment process 2 is shown in detail in Figure 2. Waste gypsum board 12 is fed into crusher 10 through inlet 11 and transported by built-in conveyor 13. For example, blades 14 are dropped to roughly crush the waste gypsum board 12. 15 is a drive unit that raises the blades and allows them to fall freely. A sieve 16 is provided on the outlet side of crusher 10, and the gypsum particles generated by crushing are separated below the sieve. The mesh size of sieve 16 is preferably approximately 5 to 15 mm. Note that the type of crusher 10 is optional, and when a range is specified using "to" in this specification, both the upper and lower limits are included. For example, 5 to 15 mm means 5 mm or more and 15 mm or less.

[0020] When the gypsum particles are separated by the sieve 16, foreign matter such as metal, mortar, and wood chips in the crushed pieces of waste gypsum board becomes easy to see. Therefore, the components that remain on the sieve 16 are fed to the sorting conveyor 18, and these foreign matter are removed on the conveyor 18 by visual inspection or by image recognition using AI or the like and a robotic hand or the like.

[0021] The gypsum granules that have passed through the sorting conveyor 18 are fed into the constant-volume conveyor 20 shown in FIG. 3. The constant-volume conveyor 20 is a belt conveyor that divides the belt into sections of a predetermined length by plates 21 perpendicular to the belt. Both sides of the belt are surrounded by side plates 22, and the plates 21 and side plates 22 determine the size of each storage space (cell). The constant-volume conveyor 20 is inclined from the horizontal plane at an angle of, for example, about 30 to 50 degrees, so that any gypsum granules that exceed the size of a cell fall into the cell below, thereby limiting the amount of gypsum granules per cell. Therefore, even if the amount of gypsum granules fed from the sorting conveyor 18 shown in FIG. 2 increases, the gypsum granules will not overflow from the fine crusher 30 at the downstream stage.

[0022] In the fixed-volume transfer conveyor 20, magnetic substances such as metals are attracted and separated from the gypsum granules by a suspended magnetic separator 26 or a magnetized drum 27. Note that the removal of magnetic substances by the conveyor 20 is not part of this invention.

[0023] Returning to Figure 2, the gypsum granules are supplied from the fixed-quantity transfer conveyor 20 to a fine crusher 30 such as a roller crusher, where they are crushed to a size suitable for the crystallization process 6. A sieve (not shown) is also provided in the fine crusher 30 to separate paper pieces derived from the waste gypsum board as an over-sieve component. The under-sieve gypsum granules are entrained in an air flow by a magnetic separation pipe 32 and supplied to a silo 40.

[0024] As shown in Figure 4, a magnetic separation unit 34 is attached to a pipe 33 of the magnetic separation pipe 32. By reducing the pressure at the outlet side of the magnetic separation pipe 32, the gypsum particles flow together with air toward the outlet side of the magnetic separation pipe 32. A permanent magnet or an electromagnet 35 is attached to the magnetic separation unit 34, and it attracts the magnetically attached material flowing through the magnetic separation pipe 32. The attracted magnetic material is then removed, for example, periodically by hand through a door 36. The magnetic separation pipe 32 is preferably inclined upward, so that foreign material with a high specific gravity, such as gravel, is separated from the bottom of the pipe 32.

[0025] 5 and 6 show a silo 40 for storing gypsum granules made from crushed waste gypsum board. In the silo 40, reference numeral 41 denotes a side wall, 42 denotes an inlet, and 43 denotes a bottom. The side wall 41 is inclined inward from the vertical direction at an angle of, for example, 1° to 20°, preferably 3° to 10°, so that the bottom 43 is wider than the inlet 42. This inclination angle is represented by θ.

[0026] The inner diameter (diameter) of the bottom 43 is D, and the height of the gypsum granules in the silo 40 is H. Setting the inner diameter D to be equal to or greater than the height H is effective in preventing the gypsum granules from solidifying. In this embodiment, the inner diameter D is, for example, 3 to 4 m, the storage height H of the gypsum granules is, for example, 3 m, and the volume of the stored gypsum granules is, for example, 20 m. 3 The volume of the gypsum granules stored in the silo 40 is, for example, 5 m 3 ~30m 3 The degree is preferable.

[0027] A plurality of screw conveyors 44 (for example, three to five) are provided on the bottom 43 of the silo 40 and driven by a drive unit 45. The screw conveyors 44 transport the gypsum granules to the right side in FIGS.

[0028] Another screw conveyor 46 is provided on the bottom 43 and driven by a drive unit 47 to discharge the gypsum granules from a discharge port 48. As shown by the chain line on the right side of Figure 6, a screw conveyor 49 may be provided in which the conveying direction of the gypsum granules is reversed midway, and the gypsum granules may be discharged from an outlet 50. A hopper may be provided instead of the screw conveyors 46 and 49. However, additional space is required for the hopper, and the gypsum granules are prone to solidification in the hopper.

[0029] The operation of the silo 40 will now be explained. The gypsum granules produced from crushed waste gypsum boards tend to coagulate, making it difficult to remove them from the silo 40. Therefore, the gypsum granules are transported from almost the entire bottom 43 by multiple screw conveyors 44, collected by screw conveyors 46 and 49, and discharged from discharge outlets 48 and 50.

[0030] Since the gypsum granules are discharged from almost the entire surface of the bottom 43 and the side walls 41 are tilted inward, bridges of gypsum granules naturally collapse. Also, gypsum granules adhering to the side walls 41 tend to fall. Furthermore, since the height H of the gypsum granules is smaller than the inner diameter D of the bottom 43, the gaps formed by the screw conveyor 44 tend to affect the gypsum granules at the top. These features prevent the gypsum granules from hanging (forming bridges) inside the silo 40 and the gypsum from adhering to the side walls 41. [Explanation of symbols]

[0031] 2 Pretreatment process 4. Calcination process 6 Crystallization process 8. Filtration process 10 Crusher 11 Inlet 12 Waste gypsum board 13 Conveyor 14 blades 15 Drive unit 16 Sieve 18 Sorting conveyor 20 Fixed-quantity conveyor 21 Plate 22 Side panel 23 Gypsum granules 26 Hanging magnetic separator 27 Magnetized drum 30 Fine crusher 32 Magnetic separation pipe 33 Pipe 34 Magnetic Separation Unit 35 Magnet 36 Doors 40 Silo 41 Side wall 42 Inlet 43 bottom 44, 46, 49 Screw conveyor 45,47 Drive unit 48,50 outlet

Claims

1. A crushing step of crushing the waste gypsum board into gypsum granules; A storage step of storing the gypsum granules obtained in the crushing step in a silo. In a method for crushing waste gypsum board, In the storing step, the gypsum granules in the silo are discharged to the outside of the silo by a plurality of screw conveyors provided at the bottom of the silo, In the crushing step, The waste gypsum board is crushed by a crusher, and the crushed waste gypsum board is sieved. The components that did not pass through the sieve are transported by a belt conveyor, and foreign matter is removed on the belt conveyor. A fixed quantity conveyor is used, which has a belt, a plurality of plates attached to stand up from the belt, and side plates on both sides of the belt, and conveys materials obliquely upward, The gypsum granules that have passed through the belt conveyor are supplied to a fixed-quantity conveying conveyor, and the gypsum granules are supplied to a fine crusher while regulating the amount of the gypsum granules with the plate. A method for crushing waste gypsum boards, characterized in that gypsum granules after being crushed by a fine crusher are supplied to a pipe, and the gypsum granules are transported to the silo by the pressure difference between both ends of the pipe, and a magnet is attached to the pipe and magnetic material is separated from the gypsum granules by magnetic force.

2. 2. The method for crushing waste gypsum boards according to claim 1, characterized in that the inner wall of the silo is inclined from the vertical direction so as to face the inside of the silo, thereby preventing the formation of bridges of gypsum particles inside the silo.

3. 3. The method for crushing waste gypsum boards according to claim 1 or 2, wherein the gypsum granules discharged by the plurality of screw conveyors are collected by another screw conveyor and discharged to the outside of the silo.

4. In the storage step, when the inner diameter of the bottom of the silo is D and the storage height of the gypsum granules is H, the gypsum granules are stored in the silo so that the inner diameter D is equal to or greater than the height H. A method for crushing waste gypsum board according to any one of claims 1 to 3.

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