JP2021122768A - Method for recovery of metals from gypsum board waste materials - Google Patents

Abstract

To provide a method for effective recovery of magnetic substances such as iron and stainless steel which are valuables themselves while being obstacles in recycling of gypsum itself on recycling of gypsum board waste materials from the gypsum board waste material.SOLUTION: After gypsum board waste materials are pulverized by using a shear pulverizer, etc., separation is conducted by using an air table type gravity sorter in a setting that gypsum is on a low specific gravity component side and magnetic substances are on a high specific gravity component side, and components on the high specific gravity side are processed with a magnetic separator for sucking and recovering magnetic substances. Gypsum which has been recovered as a component on the low specific gravity side is recycled by a method involving melting and re-precipitation.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for efficiently recovering magnetic substances such as iron and stainless steel nails contained in gypsum board waste material.

A large amount of gypsum board waste is generated due to the demolition and renovation of buildings. For this reason, it is necessary to dispose of gypsum board waste material. In Patent Document 1 proposed by the inventors, gypsum board waste material is crushed, gypsum powders obtained by baking are mixed with gypsum slurry in a mixing tank, and dihydrate gypsum particles are precipitated in a precipitation tank. Next, dihydrate gypsum particles are extracted from the gypsum slurry by a solid-liquid separator, and the filtrate is circulated to the mixing tank.

Gypsum board is a building material, and various other building materials used in construction and refurbishment are often contained as foreign substances in the gypsum board waste material. In addition, even after construction, nails and screws may be driven in to attach shelves, etc., which are also mixed in the gypsum board waste material.

WO2012 / 176688

When recycling gypsum board waste material by the method described above, these foreign substances need to be removed in advance. For example, heavy foreign matter such as iron or stainless steel may settle in the dihydric gypsum precipitation tank and interfere with the stable operation of the device. On the other hand, such iron and stainless steel are treated as valuable objects for recycling by themselves, and it is useful if they can be efficiently recovered.

If the foreign matter has a relatively large shape, it can be separated by hand before or after crushing, but small ones such as nails and screws cannot be sufficiently removed.

Further, as a method of recovering a magnetic substance from a mixture containing various substances, a magnetic separator has been conventionally used. However, according to the study by the present inventors, even if an attempt is made to recover the magnetic substance contained in the waste gypsum powder by a magnetic separator, there is a problem that a substance having a weak magnetic force such as austenitic stainless steel, which is widely used, cannot be sufficiently recovered. was there. Furthermore, in this method, a large amount of gypsum powder may be mixed in the material recovered by the magnetic separator.

Therefore, an object of the present invention is to provide a method for efficiently recovering the magnetic substance such as iron or stainless steel from the waste gypsum board material.

Although austenitic stainless steel is originally non-magnetic, it becomes weakly magnetic when subjected to strong stress due to crushing or the like, and is treated as a magnetic substance in the present invention.

The present inventors have made diligent efforts in view of the above problems, focused on the fact that the difference in specific densities between gypsum and metals such as stainless steel is large, and after subjecting the gypsum board waste material containing foreign substances such as stainless steel to specific densities, a magnetic separator. The present invention was completed by finding that it can be efficiently separated and recovered.

That is, the present invention is a method for recovering a magnetic substance from gypsum board waste material.
The crushing process of crushing gypsum board waste material to obtain crushed material,
A separation process in which the crushed material is placed on an air table type specific gravity sorter and the gypsum is set to the low specific density component side and the magnetic substance is set to the high specific density component side for separation.
A method for recovering a magnetic substance from a gypsum board waste material, which comprises a step of subjecting a high specific density component obtained in the separation step to a magnetic separator and sucking and recovering the magnetic substance.

The whole schematic diagram of the recycling of the gypsum board waste material including the recovery process of the magnetic substance of this invention. Schematic diagram of the air table type specific gravity sorter used in the examples

1 and 2 show an example for carrying out the present invention. FIG. 1 shows a process of treating gypsum board waste material including a process of recovering magnetic foreign matter. Magnetic foreign matter such as stainless steel is mixed in the received gypsum board waste material. In some cases, sand and gravel are also mixed.

The received gypsum board waste material is crushed by a primary crusher 2 composed of a biaxial shear type crusher. Even boards containing metals such as stainless steel and gravel can be easily crushed by using a shear crusher. Moreover, since it is easy to crush the metal itself by using a shear type crusher, it can be crushed to a size that can be easily recovered by a magnetic separator.

The gypsum board waste material is a relatively fine powder consisting of small foreign substances such as stainless nails, screws, sand and gravel, and crushed gypsum, and a large lump of gypsum board waste material crushed into lumps by the primary crushing. Divided into a body (board piece). The agglomerates may be repeatedly crushed into small pieces and the entire amount may be subjected to a specific gravity sorter described later, but in terms of crushing efficiency and separation efficiency of each component, the agglomerates are once sieved so that the granules and the agglomerates are separated. , It is preferable to handle them separately until they are placed in a specific gravity sorter.

A known sieve can be appropriately selected and used as the sieve, but a dry vibrating sieve is preferable from the viewpoint of efficiency. The opening of the sieve 4 is determined so that the lumps do not pass under the sieve and clogging due to gypsum powder does not occur. For example, in a sieve having an opening of 6 mm, clogging due to gypsum powder did not occur, and no lumps were found under the sieve. If the opening is smaller than 2 mm, the possibility of clogging due to gypsum powder increases, and if the opening is larger than 10 mm, the possibility of lumps being mixed under the sieve increases. From these facts, 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.

Since the paper contained in the gypsum board waste material keeps a relatively large shape even when it is subjected to a crusher, when it is sieved in such a way, the paper component is usually a sieving component.

In the present invention, the component (under-sieve component) that has passed through the sieve is supplied to an air table type specific gravity sorter. The structure of the specific gravity sorter 12 is shown in FIG. That is, the above-mentioned subsieving component is placed on a deck (board surface) 28 which is composed of a perforated plate, a screen, etc., is inclined from a horizontal plane, and allows wind to pass through. The blower 30 blows air from the bottom to the top of the deck 28 to rock the gypsum. Further, the exciter 32 vibrates the deck 28. The direction of vibration is indicated by the black arrow in FIG. 2, and the mixture on the deck 28 is vibrated so that an impact diagonally upward is applied.

Conventionally, when an air table type specific gravity sorter is used to separate crushed gypsum board waste material, gypsum is set to be separated on the high specific density component side and paper is separated on the low specific density component side. Paper has been separated, but in the present invention, the sorting machine is set so that the gypsum is on the low specific density component side and the magnetic substance is on the high specific density component side. Since the paper is separated as a component on the sieve by sieving as described above, the amount of paper mixed in the low specific density component side is 1% or less. Further, when the above-mentioned sand or gravel is contained in the waste gypsum board material, it is preferable to set the sand or gravel to be on the high specific density component side.

In the air table type specific gravity sorter set as described above, the gypsum having a small specific gravity fluctuates due to the air flow, is not so affected by the vibration of the deck 28, and moves to the lower side of the deck 28. On the other hand, the weight component (metal such as stainless steel, gravel, etc.) is flipped up from the deck 28 by vibration and moves to the upper side of the deck 28. In addition, the fine powder of gypsum moves upward on the wind and is collected by a dust collector (not shown). In this way, gypsum and heavy components such as metal such as stainless steel and gravel are easily separated.

Such an air table type specific gravity sorter is generally commercially available, 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 made by Matsuoka Engineering Co., Ltd., GSD series, SH type made by Harada Sangyo Co., Ltd., SHB type, etc. Air table type specific gravity sorter can be used.

The component on the side recovered as a weight component is usually a mixture containing the above-mentioned magnetic substance made of various metals such as stainless steel and a small amount of non-magnetic substance such as gypsum, sand, and gravel. Is. In the present invention, this mixture is subjected to a magnetic separator to recover the magnetic substance. In the present invention, since most of the gypsum powder is separated by the above-mentioned air table type specific gravity sorter, even a substance having weak magnetism such as stainless steel can be easily recovered by the magnetic separator. The gypsum board waste material may contain iron metal fittings, which are ferromagnetic substances, and among them, the members that were small from the beginning and the size that became smaller due to the crushing and passed through the sieve. Of course, things are also collected here by a magnetic separator.

A known magnetic separator may be appropriately used as the magnetic separator. For example, a hanging magnetic separator, a drum magnetic separator, a pulley magnetic separator, or the like can be used as a commercially available magnetic separator. In order to separate substances with weak magnetism such as stainless steel, it is possible to separate them more efficiently if the distance between the substance to be separated and the magnet is as small as possible. For this reason, drum type and pulley type magnetic separators are more preferable than hanging magnetic separators. Magnets can be used in both permanent and electromagnetic types.

Most of the magnetic substances recovered in this way are usually stainless steel screws and nails (crushed products) and can be recycled as they are, but if necessary, further separation operations are performed. The operation of separating into each of the constituent components may be performed.

Since the gypsum separated by the air table type specific gravity sorter contains almost no other components, it can be reused as gypsum as it is, but it is preferable to use the method described in Patent Document 1 and the like. , Bake to convert to hemihydrate gypsum and / or type III anhydrous gypsum, dissolve this in water and then precipitate as dihydrate gypsum particles to make gypsum slurry, which is used for solid-liquid separation to dihydrate gypsum. It is more preferable to recover the particles.

Specifically, the gypsum is heated in a calcination machine 14 to, for example, about 130 ° C. to change it into hemihydrate gypsum and / or type III anhydrous gypsum. Hemihydrate gypsum and / or type III anhydrous gypsum and gypsum slurry are mixed in a mixing tank 16 to precipitate dihydrate gypsum particles in a precipitation tank 18. The mixing tank 16 and the precipitation tank 18 may be integrated or separate, and the precipitation tank 18 may be a single tank or a tank in which a plurality of stages are arranged in series. The gypsum slurry is used by circulating what is generated in the precipitation tank, and the gypsum particles contained therein become seed crystals, so that the dihydrate gypsum particles precipitated are large and of good quality.

The plaster slurry is fed from the precipitation tank 18 by the liquid feed pump 20, preferably the paper dust is sieved by the sieve 22, and the slurry under the sieve is treated by a solid-liquid separation device 24 such as a filter press. In the solid-liquid separation device 24, the dihydrate gypsum particles and the filtrate are separated. The type of the solid-liquid separation device 24 is arbitrary. The filtrate is circulated to the mixing tank, and at the same time, fresh water is added in an amount corresponding to the amount of water taken out of the system by accompanying the dihydrate gypsum particles.

On the other hand, the agglomerates separated by the above-mentioned sieving treatment may be treated in the same manner as the under-sieving component in the sieving 4 after being treated by the following procedure.

As described above, the gypsum board waste material may contain metal fittings made of iron, which is a ferromagnetic substance, and those that have not been sufficiently reduced by the crushing are mixed in this lump (sieving component). ing. Therefore, it is preferable that the iron on the sieve is once subjected to a magnetic separator to remove the iron. Further, since it is easy to visually confirm the size that remains on the sieve, manual sorting may be used in combination as appropriate. In the magnetic separation at this stage, since it is a mixture of a magnetic substance and a large amount of gypsum, it is difficult to recover a substance with weak magnetism such as stainless steel, and substantially only iron is recovered.

After iron is removed by the magnetic separator 6, the agglomerates after the primary crushing are secondary crushed by the secondary crusher 8. The secondary crusher 8 is preferably a hammer crusher, a roll crusher, a pin roll crusher, or the like.

The crushed material by the secondary crushing is separated into gypsum under the sieve, various metals and the like, and a piece of paper on the sieve by the sieve 10. Since the piece of paper has a larger size in a plan view than the powder or granular material of gypsum and the metal component, it can be separated by the sieve 10. The type of sieve 10 is arbitrary, and is not limited to a vibrating sieve or the like, and a screen attached to a pin roll crusher may be used. 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.

In other words, in the secondary crushing, it is preferable that almost the entire amount of the gypsum component becomes the subsieving component in the above-mentioned open sieve. In this respect, it is preferable to use a hammer crusher for the secondary crushing of the agglomerates that could not be crushed by the primary crushing by the shear crusher. It is preferable to crush with.

Then, if the sieving component thus obtained is treated with an air table type specific gravity sorter and a magnetic separator in the same manner as the sieving component in the sieve 4 described above, a magnetic substance having weak magnetism such as stainless steel can be efficiently produced. Can be recovered. Although these treatments may be performed separately from the subsieving component in the sieve 4, it is preferable to treat them as the same without distinction in terms of efficiency (they may be mixed after each sieving).

After the waste gypsum board was first crushed by a shear type twin-screw crusher, it was sieved with a mesh opening of 6 mm, and the under-sieving was put into a specific gravity sorter. Further, after passing over the sieve through a hanging magnetic separator, secondary crushing was performed with a hammer crusher and a roll crusher, and then sieving was performed with a mesh opening of 6 mm, and the under-sieving was put into a specific gravity sorter. As the specific gravity sorter, SH-10 manufactured by Harada Corporation was used, and in addition to metals, gravel and the like were set to be separated on the high specific density side, and gypsum was set to be separated on the low specific density side. The two systems under the sieve were combined and charged at 5 t / h for continuous treatment.

The high specific density component obtained by separation by the specific gravity sorter was put into a pulley type magnetic separator to separate the magnetic substance. The pulley type magnetic separator used a magnetic force of 10,000 gauss manufactured by EMS Co., Ltd. As a result of continuous operation for 24 hours, the amount of metal recovered by the pulley type magnetic separator was 30 kg. Most of the recovered metals were weakly magnetic stainless steel. The gypsum content in the material recovered by the magnetic separator was 0.1% or less.

Comparative example

As for the treatment until the material was subjected to the specific gravity sorter, the subsieving portion which had been subjected to the same treatment as in the example was charged into the drum type magnetic separator at 5 t / h without being treated by the specific gravity sorter. As a result of continuous operation for 24 hours, the amount of metal recovered was 2 kg. About half of the recovered metal was stainless steel. The gypsum content in the material recovered by the magnetic separator was 15%.

2 Primary crusher 4 Sieve 6 Magnetic separator 8 Secondary crusher 10 Sieve 11 Magnetic separator 12 Air table type specific gravity sorter 14 Kake machine 16 Mixing tank 18 Precipitation tank 20 Liquid transfer pump 22 Sieve 24 Solid-liquid separation device 28 Deck 30 Blower 32 Exciter

Claims (4)

It is a method of recovering magnetic substances from gypsum board waste material.
The crushing process of crushing gypsum board waste material to obtain crushed material,
A separation process in which the crushed material is placed on an air table type specific gravity sorter and the gypsum is set to the low specific density component side and the magnetic substance is set to the high specific density component side for separation.
A method for recovering a magnetic substance from a gypsum board waste material, which comprises a step of subjecting a high specific density component obtained in the separation step to a magnetic separator and sucking and recovering the magnetic substance. The method for recovering a magnetic substance according to claim 1, wherein the magnetic substance is stainless steel. The method for recovering a magnetic substance according to claim 1 or 2, wherein the gypsum board waste material is crushed by a shear type crusher. The magnetic substance is recovered from the waste gypsum board by the method according to any one of claims 1 to 3, and the gypsum recovered as the low specific gravity component side is heated to make hemihydrate gypsum and / or type III anhydrous gypsum. Next, a method for recycling gypsum board waste material, which is dissolved in water and then precipitated as dihydrate gypsum particles, and the gypsum slurry containing the dihydrate gypsum particles is subjected to solid-liquid separation to recover the dihydrate gypsum particles.

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