JP7303729B2 - Waste gypsum board processing method - Google Patents

Description

The present invention relates to a method for treating waste gypsum board.

A large amount of waste gypsum board is generated due to the demolition and renovation of buildings. Therefore, there is a need to treat the waste gypsum board. In Patent Document 1 (WO2012/176688) proposed by the inventors, waste gypsum boards are crushed, gypsum powder obtained by calcination is mixed with gypsum slurry in a mixing tank, and gypsum dihydrate is produced in a precipitation tank. Precipitate the particles. Next, gypsum dihydrate particles are extracted from the gypsum slurry by a solid-liquid separator, and the filtrate is circulated to the mixing tank.

Waste gypsum board may have gypsum plaster attached to it. Gypsum plaster contains gypsum, sand, gravel, etc., and is used to improve the design of Japanese-style room walls. Also, since the gypsum plaster is strongly bonded to the gypsum board, it is difficult to separate the gypsum plaster from the gypsum board.

WO2012/176688

When recovering gypsum from waste gypsum boards, it is necessary to separate foreign matters such as sand and gravel from the gypsum. Even when the collected gypsum is used as a soil conditioner or the like as it is, contamination with sand or gravel is not preferable. When the gypsum dihydrate particles are precipitated from the slurry as in Patent Document 1, sand and gravel wear the impeller of the pump that feeds the gypsum slurry, the stirring blades of the precipitation tank, the pipes and valves of the processing equipment, and the like. It is difficult to sieve dry so that sand and gravel remain and allow gypsum to pass through because the gypsum powder clogs the openings of the sieve. Classifying sand and gravel from gypsum by airflow requires relatively large equipment such as cyclones.

An object of the present invention is to remove heavy foreign matters such as sand and gravel contained in waste gypsum board.

The present invention comprises a first crushing step for crushing waste gypsum boards into crushed materials;
performing a separation step of separating the crushed material into gypsum and foreign matter having a higher specific gravity than gypsum;
In the separation step, an air table type specific gravity sorter is used to separate foreign matters as high specific gravity components and gypsum as low specific gravity components.

In this invention, gypsum and heavy foreign matter are separated not by the difference in size but by the difference in specific gravity, utilizing the fact that gypsum derived from waste gypsum boards has a small specific gravity. Then, before sorting by specific gravity, the waste gypsum board is crushed in the first crushing step. In sorting by specific gravity, an air table type specific gravity sorter is used, and sorting is performed using air currents and deck vibrations. Therefore, it can be sorted with a smaller device than a cyclone or the like.

Preferably, after the first crushing step, a sieving step of sieving the crushed matter with a sieve;
a second crushing step of further crushing components that did not pass through the sieve in the sieving step;
performing a paper separation step of sieving the crushed material obtained in the second crushing step to separate the paper;
In the crushed material obtained in the first crushing step, the components that have passed through the sieve in the sieving step and the components from which the paper has been separated in the paper separation step are treated in the separation step.

In the first crushing step, the waste gypsum board is crushed into granules and block board pieces. Since the granules and board pieces have different sizes, they can be separated by a sieve. The board pieces are then further crushed by a second crushing step, and the waste gypsum board becomes a mixture of paper and gypsum granules and heavy contaminants. At this stage, the paper is in the form of flakes and is larger than the gypsum and heavy foreign matter, so the paper can be recovered by sieving. Then, the mixture of gypsum and heavy foreign matter is sorted by an air table type specific gravity separator together with the sieved crushed material of the first crushing step, whereby gypsum and heavy foreign matter can be separated.

Also preferably, at least part of the waste gypsum board is waste gypsum board with gypsum plaster. Since the invention is suitable for separating sand and gravel in gypsum plaster from gypsum, waste gypsum board with gypsum plaster can also be treated.

Preferably, the first crushing step is performed by a shear crusher. Waste gypsum boards can be easily crushed by using a shear crusher.

Preferably, a calcining step of calcining the gypsum obtained in the separation step to gypsum hemihydrate and/or anhydrous gypsum type III;
a precipitation step of dissolving the gypsum hemihydrate and/or type III anhydrous gypsum obtained in the calcination step in water to form a slurry in which gypsum dihydrate particles are precipitated;
and a solid-liquid separation step of separating gypsum dihydrate particles from the slurry obtained in the precipitation step, and recovering the gypsum dihydrate particles from the waste gypsum board.

Since sand and gravel are separated before calcination, they do not wear the impellers, stirring blades, pipes, valves, etc. of the slurry feed pump.

A diagram showing a method for treating waste gypsum in an embodiment Schematic diagram of the air table type specific gravity sorter used in the example

Examples for carrying out the present invention are shown below. The scope of the present invention should be determined according to the understanding of those skilled in the art based on the description of the claims, taking into consideration the description of the specification and well-known techniques in this field. The scope of the invention is not limited by the examples.

1 and 2 show an embodiment. FIG. 1 shows the treatment process of waste gypsum board. Among the received waste gypsum boards, there are mixed ones with gypsum plaster. Waste gypsum board contains gypsum and paper at a mass ratio of 10:1, etc., and gypsum and paper are worth recovering, and the amount of mixed sand and gravel is indefinite. The received waste gypsum board is crushed by a primary crusher 2 consisting of a twin-shaft shear type crusher. Even boards containing sand or gravel can be easily crushed using a shear crusher. Through the primary crushing, the waste gypsum board is separated into powdery particles composed of crushed gypsum and heavy foreign matters such as sand and gravel, and lumps (board pieces) obtained by crushing the waste gypsum board into lumps.

The crushed material in the primary crushing is sieved by a sieve 4 such as a vibrating sieve into powdery particles and lumps. Since the purpose of sieving is not to separate gypsum and heavy foreign matters, but to separate powders and aggregates, dry sieving can be easily performed. Any type of sieve may be used. The mesh size of the sieve 4 is determined so that the agglomerates do not pass under the sieve and clogging with gypsum powder does not occur. For example, with a sieve with an opening of 6 mm, clogging with gypsum powder did not occur, and lumps were not observed under the sieve. If the mesh size is smaller than 2 mm, the possibility of clogging with gypsum powder increases, and if the mesh size is larger than 10 mm, the possibility of lumps being mixed in under the sieve increases. For these reasons, the opening is, for example, 2 mm or more and 10 mm or less, preferably 4 mm or more and 10 mm or less, and most preferably 4 mm or more and 8 mm or less.

A component (under-sieve component) that has passed through the sieve 4 is supplied to an air table type gravity sorter 12 . Here, however, the treatment of the lumps remaining on the sieve 4 will be explained first. Since it is preferable to remove iron such as metal fittings contained in the mass, iron is removed by the magnetic separator 6 . Next, the primary crushed aggregates are secondarily crushed by the secondary crusher 8 . A hammer crusher, a roll crusher, a pin roll crusher, or the like is preferable for the secondary crusher 8, and the aggregates are crushed into granules by the secondary crushing to form a mixture of gypsum, paper, and heavy foreign matters. A sieve 10 separates the crushed material from the secondary crushing into gypsum and heavy contaminants under the sieve and paper pieces on the sieve. Since the paper pieces are larger in plan view than the gypsum particles and heavy foreign matter, they can be separated by the sieve 10 . The sieve 10 may be of any type, and is not limited to a vibrating sieve, and may be a screen attached to a pin roll crusher. Like the sieve 4, the mesh size of the sieve 10 is preferably 2 mm or more and 10 mm or less, more preferably 4 mm or more and 10 mm or less, and most preferably 4 mm or more and 8 mm or less.

A mixture of gypsum and heavy contaminants that has passed through the sieve 10 is supplied to a gravity sorter 12 together with the sieved components of the sieve 4 . The structure of the gravity sorter 12 is shown in FIG. The above mixture is placed on a deck 28 consisting of a perforated plate, screen or the like, inclined from the horizontal and through which air flows. A blower 30 blows air from the bottom to the top of the deck 28 to rock the gypsum. Also, the deck 28 is vibrated by the vibrator 32 . The direction of vibration is indicated by the black arrow in FIG. 2, and the mixture on the deck 28 is vibrated so as to give an oblique upward impact. The gypsum having a low specific gravity is swayed by the air flow and moves to the lower side of the deck 28 without being greatly affected by the vibration of the deck 28 . On the other hand, heavy foreign objects are bounced up from the deck 28 by vibration and move to the upper side of the deck 28 . Gypsum fine powder is carried upward by the wind and collected by a dust collector (not shown). In this way, gypsum and heavy foreign matters such as sand and gravel are easily separated.

Such an air table type gravity sorter is generally available on the market, and an appropriate one can be used. For example, T-10 type and BX-110 type manufactured by J-Tech Co., Ltd., NCTAT013 manufactured by MM Nagata Coal Tech Co., Ltd., VS1500H type manufactured by Fuji Kogyo Co., Ltd., MH-510 series and MH manufactured by Harashima Electric Industry Co., Ltd. -310 series, GS series and GSD series manufactured by Matsuoka Engineering Co., Ltd., SH type and SHB type manufactured by Harada Sangyo Co., Ltd. can be used.

The gypsum sorted by the specific gravity sorter 12 is heated to, for example, about 130° C. by the calciner 14 to change into gypsum hemihydrate and/or anhydrous gypsum III. Gypsum hemihydrate and/or type III anhydrous gypsum and gypsum slurry are mixed in a mixing tank 16 , and gypsum dihydrate particles are precipitated in a precipitation tank 18 . The mixing tank 16 and the precipitation tank 18 may be integrated or separated, and the precipitation tank 18 may be a single tank or a series of multiple stages.

A gypsum slurry is sent from a precipitation tank 18 by a liquid sending pump 20, paper dust is preferably sieved by a sieve 22, and the slurry under the sieving is treated by a solid-liquid separator 24 such as a filter press. The solid-liquid separator 24 separates the gypsum granules and the filtrate, and the type of the solid-liquid separator 24 is arbitrary. Water is added to the filtrate and part of the slurry in the precipitation tank 18 and circulated to the mixing tank.

In this embodiment, the primary crusher 2 crushes the waste gypsum board, and the sieve 4 separates it into granules containing gypsum and heavy contaminants and lumps. Since the granules and lumps are separated instead of separating the gypsum from the heavy foreign matter, separation can be achieved without clogging the sieve. The lumps on the sieve 4 are secondarily crushed, and the sieve 10 separates the paper in the state of paper pieces. The under-sieved components of the sieve 4 and the under-sieved components of the sieve 10 are sorted by an air table type gravity sorter 12 . Since gypsum powder particles derived from waste gypsum board have a small specific gravity and differ from sand and gravel in specific gravity, they can be separated by airflow and vibration of the deck 28 .

When the gypsum from which sand and gravel have been removed is treated in the mixing tank 16 and the precipitation tank 18, gypsum dihydrate particles are precipitated. Since the sand and gravel are removed, the impeller, pipes, valves, stirring blades, etc. of the liquid feed pump 20 are not worn by these foreign substances. Then, the gypsum dihydrate particles and the filtrate are separated by the solid-liquid separator 24 , and the filtrate is circulated to the mixing tank 16 .

2 Primary Crusher 4 Sieve 6 Magnetic Separator 8 Secondary Crusher 10 Sieve 12 Air Table Gravity Separator 14 Calciner 16 Mixing Tank 18 Precipitation Tank 20 Liquid Feeding Pump 22 Sieve 24 Solid-Liquid Separating Device 28 Deck 30 Blower 32 Vibrator

Claims (4)

a first crushing step of crushing the waste gypsum board into crushed materials;
After the first crushing step, a sieving step of sieving the crushed material into granules and lumps with a sieve;
A magnetic separation step of magnetically separating the lumps obtained in the sieving step to remove iron;
a second crushing step of further crushing the iron-removed mass;
A paper separation step of further sieving the crushed material obtained in the second crushing step and sieving it into a mixture of gypsum and foreign substances having a higher specific gravity than gypsum and paper;
The granules obtained in the sieving step and the mixture obtained in the paper separation step are separated by an air table type specific gravity sorter to separate foreign matter with a higher specific gravity than gypsum as a high specific gravity component and gypsum as a low specific gravity component. A method for treating waste gypsum board, comprising: 2. The method for treating waste gypsum board according to claim 1 , wherein at least part of the waste gypsum board is waste gypsum board with gypsum plaster. 3. The method for treating waste gypsum board according to claim 1, wherein said first crushing step is performed by a shear crusher. a calcining step of calcining the gypsum obtained in the gravity separation step to form gypsum hemihydrate and/or anhydrous gypsum type III;
a precipitation step of dissolving the gypsum hemihydrate and/or type III anhydrous gypsum obtained in the calcination step in water to form a slurry in which gypsum dihydrate particles are precipitated;
4. The method for treating waste gypsum boards according to any one of claims 1 to 3 , further comprising a solid-liquid separation step of separating gypsum dihydrate particles from the slurry obtained in the precipitation step.

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