JP7078512B2 - How to collect dihydrate gypsum from waste gypsum board - Google Patents

Description

The present invention relates to the recovery of dihydrate gypsum from waste gypsum board.

Patent Document 1 (WO2012 / 176688) discloses the recovery of dihydrate gypsum from waste gypsum board. The waste gypsum board is crushed by a crusher and separated into a piece of paper and gypsum. If necessary, magnetic separators are placed before and after the crusher to separate metallic foreign substances such as screws and screws and remove the foreign substances. Gypsum from which foreign substances have been removed is calcinated to change it into hemihydrate gypsum and mixed with water to make gypsum slurry. Dihydrate gypsum particles can be recovered by precipitating dihydrate gypsum particles in the gypsum slurry, removing the remaining paper dust with a vibrating sieve, and solid-liquid separating the gypsum slurry that has passed through the sieve.

WO2012 / 176688

The inventors have noticed that the waste gypsum board contains gravel and sand derived from gypsum plaster and the like, in addition to the paper and metallic foreign matter derived from the base paper of the gypsum board. In addition, non-magnetic metals such as copper and aluminum cannot be separated by a magnetic separator. After calcination, we tried to separate the sand, gravel, etc. in the gypsum from the metallic foreign matter (heavy foreign matter) by wind sorting, but the gypsum is stuck to the heavy foreign matter, so the separation between the gypsum and the heavy foreign matter is insufficient. Met.

An object of the present invention is to efficiently separate heavy foreign substances in a gypsum slurry.

In the present invention, gypsum derived from waste gypsum board is baked into semi-water and / or anhydrous type III gypsum granules, and the gypsum granules are mixed with water to form a gypsum slurry, which is then precipitated in the gypsum slurry. In the method of recovering the dihydrate gypsum from the waste gypsum board, which separates the dihydrate gypsum particles into solid and liquid.
It is characterized in that after mixing the gypsum granules with water and before solid-liquid separation of the dihydrate gypsum particles, heavy foreign substances in the gypsum slurry are removed by gravity sedimentation.

Compared to the dry separation of heavy foreign matter by wind sorting, etc., when the heavy foreign matter is settled in the gypsum slurry, the heavy foreign matter and the slurry can be easily separated, and the sieve attached to the separation device is clogged with gypsum. Nor. In the present invention, heavy foreign matter can be efficiently removed from the dihydrate gypsum slurry.

Preferably, the gypsum granules are mixed with water in the mixing tank, and the dihydrate gypsum particles are precipitated in the gypsum slurry in the precipitation tank.
The gypsum slurry was introduced into a foreign matter separator, and separated into a mixture of gypsum slurry and heavy foreign matter and gypsum slurry by gravity sedimentation.
The separated gypsum slurry is refluxed into a mixing tank or a precipitation tank.
The mixture is sieved into a heavy foreign substance and a gypsum slurry, and the sieved gypsum slurry is refluxed into a mixing tank or a precipitation tank.

The heavy foreign matter wears the stirring blades of the mixing tank and the precipitation tank, the impeller of the pump that sends out the gypsum slurry, the piping, and the like, and further makes the rotation of the stirring blade unstable. Therefore, the gypsum slurry is introduced into the foreign matter separating device from the precipitation tank or the mixing tank, and the gypsum slurry from which the foreign matter has been removed is refluxed to suppress the wear of the device and enable stable stirring. The heavy foreign matter may be separated immediately before the solid-liquid separation. If the precipitation of dihydrate gypsum particles progresses in the gypsum slurry, the separation of heavy foreign matter becomes easy. Therefore, the gypsum slurry is preferably extracted from the precipitation tank to separate the heavy foreign matter.

It is difficult to separate only heavy foreign matter by gravity sedimentation, and gypsum slurry accompanies the heavy foreign matter. Therefore, the mixture is sieved into a heavy foreign substance and a gypsum slurry, and the sieved gypsum slurry is refluxed to a mixing tank or a precipitation tank to prevent loss of the gypsum slurry.

Particularly preferably, the mixture is sieved into heavy foreign matter and gypsum slurry by a vibrating sieve, and paper powder is sieved from the gypsum slurry by a vibrating sieve before the solid-liquid separation, and the sieved gypsum slurry is sieved into a solid liquid. To separate.

In the stage before solid-liquid separation, heavy foreign matter has been sieved from the gypsum slurry, and if the paper powder is sieved from the gypsum slurry from which the heavy foreign matter has been removed, the recovered paper powder can be reused as a raw material for papermaking. Also, unlike the mesh, the vibrating sieve is less likely to be clogged with paper dust.

A process diagram showing a method of recovering the dihydrate gypsum of the example. The figure which shows the separation process of the heavy foreign matter in an Example The figure which shows the separation process of the heavy foreign matter in the modification

Examples for carrying out the present invention are shown below. The scope of the present invention should be determined in accordance with the understanding of those skilled in the art, based on the description of the scope of claims, taking into consideration the description of the specification and the well-known techniques in the art.

1 to 3 show examples and modifications. In FIG. 1, 2 is a dihydrate gypsum recovery device, in which waste gypsum board is crushed by a crusher 4, crushed by a crusher 5, and separated into waste gypsum and a piece of paper derived from gypsum board paper by a sieve (not shown). do. Then, for example, the waste gypsum is temporarily stored in a silo 6 and heated to, for example, 130 ° C. or higher and 150 ° C. or lower by a calcination machine 7 to change it into semi-hydrated gypsum and / or anhydrous type III gypsum. The silo 6 does not have to be provided. Heavy foreign matter such as sand, gravel, and metal pieces and paper powder are mixed in the gypsum baked with the calcination machine 7, and the gypsum is stuck to the heavy foreign matter. Therefore, the gypsum and the heavy foreign matter are separated by wind sorting or the like. It's difficult to do. Further, when separated by a sieve, heavy foreign matter below the opening of the sieve cannot be removed, and when the opening is made small, the sieve is easily clogged with gypsum.

The gypsum baked gypsum is put into the mixing tank 10 and mixed with the gypsum slurry, the filtrate of the gypsum slurry and water refluxed from the foreign matter separating device 12 described later to obtain gypsum slurry. The gypsum slurry is supplied to a precipitation tank 11 equipped with a stirrer (not shown) by gravity drop or a slurry pump, and the gypsum slurry is stirred in the precipitation tank 11, the hemihydrate gypsum or the like is dissolved, and the gypsum slurry is precipitated as dihydrate gypsum particles. .. The heavy foreign matter wears the stirring blade of the stirrer, the impeller of the slurry pump 21 described later, the piping, etc., and makes the stirring unstable, so that it is removed by the foreign matter separating device 12. The precipitation tank 11 is not limited to multiple stages, but may be one stage.

The gypsum slurry is pumped from the bottom or bottom of the mixing tank 10 or the precipitation tank 11 to the foreign matter separating device 12 by the slurry pump 13. The heavy foreign matter in the slurry is settled on the bottom of the foreign matter separating device 12, and the gypsum slurry is refluxed from the upper part of the foreign matter separating device 12 to the mixing tank 10 or the precipitation tank 11 via the reflux path 18. Since the gypsum slurry accompanies the heavy foreign matter settled in the foreign matter separating device 12, the gypsum slurry is separated into the heavy foreign matter on the sieve and the gypsum slurry under the sieve by the vibrating sieve 14, and the gypsum slurry is passed through the reflux path 19. It is refluxed to the mixing tank 10 or the precipitation tank 11.

FIG. 2 shows the foreign matter separating device 12 in an enlarged manner. The foreign matter separating device 12 is, for example, a vertically long pipe, and the shape, inner diameter, height, presence / absence of accessories such as a baffle plate of the foreign matter separating device 12 are determined according to the flow velocity of the slurry, the shape and weight of the heavy foreign matter, and the like. The foreign matter separating device 12 has a forced discharge device such as a rotary valve 17 at the bottom or a lower portion, and discharges heavy foreign matter by the rotary valve 17. If the rotary valve 17 is not provided and the heavy foreign matter is naturally discharged from the discharge port at the bottom, a large amount of gypsum slurry also flows out. If the precipitation of dihydrate gypsum particles progresses in the gypsum slurry, it becomes easy to separate heavy foreign substances. Therefore, it is preferable to treat the slurry of the precipitation tank 11 instead of the slurry of the mixing tank 10. Further, since heavy foreign matter stays at the bottom of the precipitation tank 11 or the like, the gypsum slurry is supplied to the slurry pump 13 from the bottom or the bottom of the precipitation tank 11 or the like.

The slurry from which the heavy foreign matter has been removed and the dihydrate gypsum particles are precipitated is supplied to the vibrating sieve 15 via the slurry pump 21 to separate the paper powder and the gypsum slurry. The vibrating sieve 15 may be provided at a low position to supply the slurry by gravity drop. Since the separated paper dust does not contain heavy foreign substances, it can be reused as a papermaking material. The gypsum slurry is supplied to a solid-liquid separation device such as a filter press 16, dihydrate gypsum particles are collected, and the filtrate is supplied to the mixing tank 10 via the reflux path 20. Further, the water lost due to sieving, filtration, etc. is replenished from the reflux path 20 or the like.

The foreign matter separating device is not limited to the one having the structure shown in FIG. For example, as in the foreign matter separating device 22 of FIG. 3, heavy foreign matter may be settled while the gypsum slurry is flowing in the inclined flow path and separated from the settling portion 23. Further, a forced discharge device such as a rotary valve may be provided on the outer periphery of the bottom of the precipitation tank 11 to separate heavy foreign matter. Further, the foreign matter separating devices 12 and 22 may be arranged on the immediately upstream side of the vibrating sieve 15 and the gypsum slurry from which the heavy foreign matter has been removed may be supplied to the vibrating sieve 15.

By providing the foreign matter separating devices 12 and 22, heavy foreign matter in the slurry is removed, wear of the stirring blade, the impeller, the pipe, etc. is suppressed, stable stirring is possible, and the heavy foreign matter is further removed by the vibrating sieve 15. Allows separation of free paper dust and gypsum slurry.

Experimental example Hemihydrate gypsum 5 t / h and a mixture of filtrate and water 10 t / h were put into a mixing tank 10, and dihydrate gypsum particles were precipitated in a precipitation tank 11 having a total volume of 175 m ³ . The gypsum slurry is extracted from the bottom of the precipitation device 11 at 15 m ³ / h, supplied to the foreign matter separating device 12, the gypsum slurry in which heavy foreign matter is concentrated is discharged, and the gypsum slurry from which the heavy foreign matter has been removed is sent to the precipitation tank 11 or the like. It was refluxed. The gypsum slurry discharged from the forced discharge device was sieved by a vibrating sieve 14 having an opening of 1 mm.

Unlike the dry-type sieving, heavy foreign matter is separated from the slurry, so that clogging due to dihydrate gypsum did not occur even with a sieve having an opening of 1 mm. Since a large amount of gypsum slurry passed through the sieve, it was refluxed to the precipitation tank 11. Most of the heavy foreign substances were gravel and sand, which were aggregates of gypsum plaster, the size was about 1 to 3 mm, the amount of gypsum adhered was small, and the weight was 40 kg / h in dry weight.

A gypsum slurry was extracted from the precipitation tank 11 at 12 m ³ / h, paper dust was removed by a vibrating sieve 15, and the slurry from which the paper dust had been removed was solid-liquid separated by a filter press 16. The opening of the vibrating sieve 15 was 0.5 mm, and a lightweight foreign substance having a dry weight of 15 kg / h was separated. The ash content in the lightweight foreign matter was 22 mass%, which was derived from gypsum and sand. If the ash content is at this level, it can be recycled for papermaking.

Since the gypsum slurry was circulated between the precipitation tank 11 and the foreign matter separating device 12, damage to the impeller, piping, and stirring blade of the slurry pump could be suppressed. Further, the stirring did not stop due to the heavy foreign matter accumulated at the bottom of the precipitation tank 11. On the other hand, before the foreign matter separating device 12 was installed, the impeller and the like were significantly damaged, and the operation of the stirring blade was unstable. Further, the ash content in the foreign matter removed by the vibrating sieve 15 was 78 mass%, which had to be treated at the final disposal site.

2 Recovery device 4 Crusher 5 Crusher 6 Silo 7 Kake machine 10 Mixing tank 11 Precipitation tank 12, 22 Foreign matter separator 13.21 Slurry pump 14, 15 Vibration sieve 16 Filter press 17 Rotary valve 18-20 Circulation passage 23 Settlement Department

Claims (3)

Gypsum derived from waste gypsum board is baked into semi-water and / or anhydrous type III gypsum granules, and the gypsum granules are mixed with water to form a gypsum slurry, and then the dihydrate gypsum precipitated in the gypsum slurry. In the method of recovering dihydrate gypsum from waste gypsum board, which separates particles into solid and liquid.
Recovery of gypsum from waste gypsum board, characterized in that after mixing the gypsum granules with water and before solid-liquid separation of the gypsum particles, heavy foreign matter in the gypsum slurry is removed by gravity sedimentation. Method. The gypsum granules are mixed with water in the mixing tank, and the dihydrate gypsum particles are precipitated in the gypsum slurry in the precipitation tank.
The gypsum slurry was introduced into a foreign matter separator, and separated into a mixture of gypsum slurry and heavy foreign matter and gypsum slurry by gravity sedimentation.
The separated gypsum slurry is refluxed into a mixing tank or a precipitation tank.
The method for recovering dihydrate gypsum from the waste gypsum board according to claim 1, wherein the mixture is sieved into heavy foreign matter and gypsum slurry, and the sieved gypsum slurry is returned to a mixing tank or a precipitation tank. Sifting from the mixture into heavy foreign matter and gypsum slurry is performed by a vibrating sieve, and at the same time.
The method for recovering dihydrate gypsum from the waste gypsum board according to claim 2, wherein the paper powder is sieved from the gypsum slurry by a vibrating sieve before the solid-liquid separation, and the sieved gypsum slurry is separated into solid and liquid. ..

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