Method and system for storing waste gypsum granules

Abstract

The present invention takes out a required amount of waste gypsum granules from a container by a belt conveyor without solidifying the same. In the present invention, waste gypsum granules derived from a waste plaster board are stored. The waste gypsum granules derived from a waste plaster board are charged into a container the bottom of which is the conveying surface of a belt conveyor. By continuously operating the belt conveyor, the waste gypsum granules are taken out of the container, a part of the same is carried out to the outside, and the remaining part is raised by another conveyor to be re-charged into the container in a continuous manner.

Description

Method and system for storing waste gypsum granules

[0001] The present invention relates to a method and system for storing waste gypsum granules derived from waste gypsum boards.

[0002] The inventors have put into practical use the recovery of gypsum from waste gypsum board. For example, waste gypsum board is crushed, and the crushed waste gypsum board is sieved to separate paper chips from gypsum granules consisting of gypsum dihydrate. The separated gypsum granules are crushed to obtain gypsum granules with an adjusted particle size. The gypsum granules are then calcined in a calciner to obtain hemihydrate and / or anhydrous type III gypsum granules. The calcined gypsum granules are mixed with, for example, a gypsum slurry in a mixing tank, and, for example, gypsum dihydrate granules are precipitated from the mixed gypsum slurry in a crystallization tank. The gypsum slurry is then filtered to extract the gypsum dihydrate granules, and the filtrate is returned to, for example, the mixing tank.

[0003] To calcinate the gypsum granules, it is preferable to feed the waste gypsum granules into a calciner in fixed amounts, for example. On the other hand, the number of waste gypsum boards to be crushed in the crusher is likely to vary depending on factors such as the number of trucks that carry the waste gypsum boards. For this reason, it is necessary to store the waste gypsum granules at some step between crushing and the calciner and take out the required amount at a time.

[0004] When waste gypsum granules are stored, they tend to solidify. This makes it difficult to discharge the waste gypsum granules from the container. Therefore, the inventors proposed installing a screw conveyor at the bottom of the container and forcibly discharging the waste gypsum granules using the screw conveyor (Patent Document 1: JP 2023-36204 A).

[0005] Patent Publication No. 2023-36204

[0006] Regarding the discharge of waste gypsum using a screw conveyor, the inventor later noticed that the screw conveyor was worn out by the solidified gypsum granules. Furthermore, the bulk density of the discharged waste gypsum granules varied depending on the moisture content and the degree of solidification of the waste gypsum granules. This made it difficult to remove the required amount of waste gypsum granules from the container.

[0007] The object of this invention is to remove the waste gypsum granules one by one from the container by a belt conveyor without solidifying them.

[0008] This invention is a method for storing waste gypsum granules derived from waste gypsum boards, characterized by comprising the steps of: pouring the waste gypsum granules derived from waste gypsum boards into a container whose bottom is the conveying surface of a belt conveyor; removing the waste gypsum granules from the container by continuously operating the belt conveyor; and transporting a portion of the removed waste gypsum to the outside, and lifting the remainder by another conveyor and continuously re-feeding it into the container.

[0009] This invention is a storage system for waste gypsum granules derived from waste gypsum board, comprising a container whose bottom is the conveying surface of a belt conveyor, and equipment that transports a portion of the waste gypsum granules discharged from the belt conveyor to the outside and lifts the remainder by the conveyor and re-feeds it into the container, characterized in that the system is configured to operate the belt conveyor continuously and to continuously re-feed the remainder into the container by another conveyor.

[0010] Preferably, the conveying surface of the belt conveyor is provided over the entire bottom surface of the container.

[0011] In this invention, waste gypsum granules are removed by a belt conveyor at the bottom of a container. A portion of the removed waste gypsum granules is transported to the outside, and the remainder is recharged into the container. The recharge into the container is carried out continuously, keeping the waste gypsum granules constantly flowing within the container. As a result, the waste gypsum granules in the container circulate and do not solidify. If the waste gypsum granules do not solidify, their bulk density remains almost constant. For example, if they are removed in fixed volumes, the required amount of waste gypsum granules can be continuously removed. Furthermore, if the waste gypsum granules do not solidify and maintain their fluidity, they can be removed by a belt conveyor, with minimal belt wear.

[0012] Unlike a screw conveyor, a belt conveyor can be easily installed over the entire bottom surface of the container, which can more reliably prevent the waste gypsum granules from solidifying.

[0013] A process diagram from crushing waste gypsum boards to recovering gypsum dihydrate in the embodiment. A vertical cross-sectional view showing the storage method and storage system in the embodiment. A horizontal cross-sectional view of the main part showing the storage method and storage system in the embodiment.

[0014] 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.

[0015] An embodiment is shown in Figures 1 to 3. Figure 1 shows the entire embodiment, from crushing waste gypsum board to recovering gypsum dihydrate powder. In Figure 1, waste gypsum board is crushed into paper chips and gypsum granules using a crusher 2, and the paper chips and gypsum granules are separated using a sieve 4 such as a vibrating sieve. The gypsum granules are crushed to the required particle size using a crusher 6, and if necessary, are sieved again to further separate the paper chips. Metals such as nails are separated using a magnetic separator, and if necessary, heavy foreign matter such as gravel and concrete is separated. The crushed waste gypsum powder (composed of gypsum dihydrate) is placed in a container and discharged using a belt conveyor 10. Note that in this specification, granules refer to a powder and an aggregate of particles larger in particle size than the powder. If gypsum granules are stored between the sieve 4 and the crusher 6, the gypsum granules with a particle size larger than the powder are stored in the container.

[0016] The structures of the container 8 and the belt conveyor 10 are shown in Figures 2 and 3. The container 8 has wall surfaces 20 on all four sides, and a conveying surface 24 of the belt conveyor 10 is provided on the bottom of the container 8. In this embodiment, the conveying surface 24 of the belt conveyor 10 is provided on the entire bottom of the container 8. Reference numerals 13, 13 denote pulleys of the belt conveyor 10, one of which is a drive pulley and the other a driven pulley, and 14 is a motor for driving the belt conveyor 10. A level meter 15 is provided on the wall surface 20 of the container 8 to monitor the height of the waste gypsum powder 22 in the container 8. A slit 16 is provided at the outlet of the belt conveyor 10 from the container 8, and the slit 16 is raised and lowered by a lifting mechanism 17.

[0017] A portion of the waste gypsum powder 22 discharged from the container 8 by the belt conveyor 10 is fed into the calciner 30 using the vertical circulating conveyor 11 and the conveyor 12, and the remainder is circulated back to the container 8. For this purpose, the waste gypsum powder discharged by the belt conveyor 10 is fed into the vertical circulating conveyor 11 from a chute 19 on the inlet side, and fed into a conveyor 12 such as a screw conveyor from a chute 18 on the outlet side. The conveyor 12 transports the waste gypsum powder from right to left in FIG. 2 , and a portion of the fed waste gypsum powder is taken out in fixed amounts from an opening or the like (not shown) provided in the casing of the conveyor 12. The taken-out waste gypsum powder is supplied to the calciner 30 as shown in FIG. 1 . The remainder of the waste gypsum powder fed into the conveyor 12 is taken out, for example, from an outlet (the left end in FIG. 2 ) of the conveyor 12 and re-feeds into the container 8. The waste gypsum powder may be recharged into the container 8 continuously in the strict sense, or may be repetitively and intermittently charged without cessation. For example, the waste gypsum powder may be recharged into the container 8 at least once per minute.

[0018] In the embodiment, the waste gypsum powder is distributed by the conveyor 12 into a portion to be recharged into the container 8 and a portion to be charged into the calciner 30. However, for example, a mechanism for taking out the waste gypsum powder in predetermined amounts may be provided between the outlet of the belt conveyor 10 and the chute 19, and the taken-out waste gypsum powder may be charged into the calciner 30, with the remainder being lifted by the vertical circulating conveyor 11. Moreover, instead of the vertical circulating conveyor 11, the waste gypsum powder may be lifted by a normal belt conveyor, screw conveyor, or the like.

[0019] The controller 38 receives a signal from the level meter 15 and the like as an input to control the conveyors 10, 11, 12 and the slit 16. In this control, 1) the waste gypsum powder is supplied to the calciner 30, for example, at a fixed amount at a time, in response to a request from the calciner 30, and 2) the waste gypsum powder is circulated in the container 8 and transported by the conveyor 10, thereby agitating the waste gypsum powder and preventing it from solidifying.

[0020] In order to prevent solidification, it is preferable to increase the amount of circulated waste gypsum powder 22 and the amount of transported by the belt conveyor 10 as the amount of waste gypsum powder 22 in the container 8 increases. Therefore, the transport speed of the belt conveyor 10 and the height of the slit 16 are controlled by the controller 38 based on the signal from the level meter 15.

[0021] In this manner, the waste gypsum powder 22 in the container 8 is constantly stirred, and solidification of the waste gypsum powder can be prevented. Preventing solidification keeps the bulk density of the waste gypsum powder almost constant and maintains its fluidity, so that by controlling the discharge amount by adjusting the speed of the slit 16 and the belt conveyor 10, the waste gypsum powder can be taken out of the container 8 in constant amounts. This also prevents wear on the belt conveyor 10. When the amount of waste gypsum powder in the container 8 becomes excessive, the reception of the waste gypsum powder from the crusher 6 is stopped, and the removal and circulation of the waste gypsum powder by the conveyors 10, 11, and 12 continues.

[0022] Solidification in the container 8 progresses more easily as the moisture content of the waste gypsum powder increases. The waste gypsum powder is made of gypsum dihydrate, and solidification is a phenomenon specific to gypsum dihydrate obtained by crushing waste gypsum boards, and cannot be observed in flue gas desulfurization gypsum or recycled gypsum obtained by recrystallizing waste gypsum, even though they are both gypsum dihydrate.

[0023] A fixed amount of waste gypsum powder is taken out from the container 8 and fed into a calciner 30 to be converted into gypsum hemihydrate and / or anhydrous type III gypsum, which is then mixed with a gypsum slurry or the like in a mixing tank 32, and then, for example, gypsum dihydrate powder is precipitated in a crystallization tank 34, and the gypsum dihydrate powder or the like is filtered out by a filter 36. The filtrate is returned to the mixing tank 32, for example.

[0024] In the examples, the process up to recovery of gypsum dihydrate powder by crystallization is shown, but the steps from calcination to crystallization do not have to be performed.

[0025] 2 Crusher 4 Sieve 6 Pulverizer 8 Container 10 Belt conveyor 11 Vertical circulation conveyor 12 Conveyor 13 Pulley 14 Motor 15 Level meter 16 Slit 17 Lifting mechanism 18, 19 Chute 20 Wall surface 22 Waste gypsum powder 24 Conveying surface 30 Calciner 32 Mixing tank 34 Crystallization tank 36 Filter 38 Controller

Claims

1. A method for storing waste gypsum granules derived from waste gypsum boards, comprising the steps of: pouring waste gypsum granules derived from waste gypsum boards into a container whose bottom is the conveying surface of a belt conveyor; removing the waste gypsum granules from the container by continuously operating the belt conveyor; and transporting a portion of the removed waste gypsum to the outside, and lifting the remainder by another conveyor and continuously re-feeding it into the container.

2. The method for storing waste gypsum granules according to claim 1, characterized in that the conveying surface of the belt conveyor is provided over the entire bottom surface of the container.

3. A storage system for waste gypsum granules derived from waste gypsum boards, comprising: a container whose bottom is the conveying surface of a belt conveyor; and equipment for transporting a portion of the waste gypsum granules discharged from the belt conveyor to the outside and lifting the remainder by the conveyor and re-feeding it into the container, characterized in that the storage system for waste gypsum granules is configured to operate the belt conveyor continuously and to continuously re-feed the remainder into the container by another conveyor.

Images