JP7774809B2 - Method for recycling waste gypsum board, method for manufacturing raw materials for processed resin products using waste gypsum board, method for manufacturing raw materials for cement using waste gypsum board, and type II anhydrous gypsum obtained from waste gypsum board - Google Patents

Description

The present invention relates to a method for recycling waste gypsum board, a method for producing a raw material for a resin processed product using waste gypsum board, a method for producing a raw material for cement using waste gypsum board, and type II anhydrous gypsum obtained from waste gypsum board.

Gypsum board is an extremely useful building material and is widely used in a variety of buildings. However, the amount of waste gypsum board generated, for example when demolishing a building, is enormous and is expected to continue to increase in the future.

Waste gypsum board is recyclable; specifically, the gypsum and paper extracted from waste gypsum board can be recycled as renewable resources. Currently, for example, most of the gypsum extracted from waste gypsum board is used to remanufacture gypsum board or as a solidification material for sludge, etc. However, the amount of recycled waste gypsum board is very small compared to the total amount of waste gypsum board generated. In reality, most waste gypsum board is landfilled. In other words, it cannot be said that progress is being made toward improving and spreading the recycling environment for waste gypsum board.

Currently, waste gypsum board is landfilled at controlled industrial waste disposal sites. However, there are limitations to the land available for industrial waste disposal sites, and in order to reduce environmental impact and health hazards, it is desirable to avoid using such sites as much as possible.

For these reasons, it is desirable to create an environment in which as much waste gypsum board as possible can be recycled. For these reasons, various technologies for processing waste gypsum board have been proposed, such as those disclosed in Patent Documents 1 to 4.

Japanese Patent Application Laid-Open No. 2023-36207 Japanese Patent Application Laid-Open No. 2023-36205 Japanese Patent Application Laid-Open No. 2022-24689 Patent No. 6088277

The inventors of the present invention believe that the reasons why the improvement and widespread adoption of the recycling environment for waste gypsum boards has not progressed as desired are as follows: (1) to (4).
(1) The main uses of gypsum extracted from waste gypsum board (remanufacturing gypsum board and as a hardening agent) are currently very limited. In other words, the market is limited, and not many companies are willing to enter the market.
(2) The gypsum extracted from waste gypsum boards is generally required to be in the form of gypsum dihydrate and needle-like crystals. In other words, these characteristics and properties restrict the uses for reuse and make it difficult to expand the market (uses).
(3) The gypsum extracted from currently used gypsum boards still contains a certain amount of foreign matter, such as sand and plastic, which can have undesirable effects on the environment, limiting its uses.
(4) Recycling waste gypsum board requires a lot of cost and effort, which acts as a barrier to entry.

The inventors conducted extensive research in light of the above circumstances and discovered that by devising the properties of the gypsum extracted from waste gypsum board and the manufacturing process, its uses could be expanded.

Specifically, the inventors have discovered that by converting the gypsum extracted from waste gypsum board into fine anhydrous gypsum, particularly Type II anhydrous gypsum, and properly removing impurities, and by simplifying the process to achieve this, they can reduce takt time and manufacturing costs, thereby significantly expanding the uses of the gypsum extracted from waste gypsum board.

High-purity, fine type II anhydrous gypsum can be used, for example, as a raw material for environmentally friendly resin processed products with excellent processing precision. Because such gypsum-containing raw materials for resin processed products contain few or no impurities, they are expected to be used in the consumer sector. Furthermore, high-purity, fine type II anhydrous gypsum can be used, for example, as a cement raw material for concrete, which produces a good finish, and opportunities for its use are expected to increase. If high-purity, fine type II anhydrous gypsum can be produced from waste gypsum board in this way, the market for this gypsum will expand, leading to an improvement and widespread adoption of the recycling environment. Furthermore, if gypsum with expanded reuse applications can be easily obtained through process innovation, barriers to entry will be removed, leading to an improvement and widespread adoption of the recycling environment.

In light of the above, the present invention aims to provide a method for recycling waste gypsum board that efficiently produces high-purity, fine gypsum from waste gypsum board and can expand the range of uses for the gypsum obtained from waste gypsum board; a method for producing raw materials for resin processed products using waste gypsum board; and a method for producing raw materials for cement using waste gypsum board.

The present invention relates to the following [1] to [4].

[1] A first crushing and separation process in which a waste gypsum board including a gypsum core material and paper attached to the gypsum core material is crushed and an intermediate gypsum powder obtained by crushing the gypsum core material is separated from the paper;
A heating step of heating the intermediate gypsum powder to convert it into type II anhydrous gypsum and burning off residues containing paper and/or plastic contained in the intermediate gypsum powder;
The method for recycling waste gypsum board includes a second crushing and separation step of crushing the intermediate gypsum powder after the heating step into fine gypsum powder using an airflow crusher, and separating a residue containing sand contained in the intermediate gypsum powder from the fine gypsum powder using a classification section of the airflow crusher.

[2] A first crushing and separation process in which a waste gypsum board including a gypsum core material and paper attached to the gypsum core material is crushed and an intermediate gypsum powder obtained by crushing the gypsum core material is separated from the paper;
A heating step of heating the intermediate gypsum powder to convert it into type II anhydrous gypsum and burning off residues containing paper and/or plastic contained in the intermediate gypsum powder;
A second crushing and separating step in which the intermediate gypsum powder after the heating step is crushed into fine gypsum powder by an airflow crusher, and a residue containing sand contained in the intermediate gypsum powder is separated from the fine gypsum powder by a classification unit of the airflow crusher.
A method for producing a resin processed raw material using waste gypsum board, comprising: a raw material production step of producing a resin processed raw material by mixing the fine gypsum powder with a resin composition.

[3] A first crushing and separation process in which a waste gypsum board including a gypsum core material and paper attached to the gypsum core material is crushed and an intermediate gypsum powder obtained by crushing the gypsum core material is separated from the paper;
A heating step of heating the intermediate gypsum powder to convert it into type II anhydrous gypsum and burning off residues containing paper and/or plastic contained in the intermediate gypsum powder;
A second crushing and separating step in which the intermediate gypsum powder after the heating step is crushed into fine gypsum powder by an airflow crusher, and a residue containing sand contained in the intermediate gypsum powder is separated from the fine gypsum powder by a classification unit of the airflow crusher.
A method for manufacturing a cement raw material using waste gypsum board, comprising: a raw material manufacturing step of manufacturing a cement raw material by mixing the fine gypsum powder with lime.

[4] Type II anhydrous gypsum obtained from waste gypsum board, in which 80% or more of the components in the particle size distribution have particle sizes of 50 μm or less, are non-needle crystals and non-plate crystals, and the Type II anhydrous gypsum component accounts for 90% by mass or more of the total. The mass% of the components is determined by wavelength dispersive X-ray fluorescence analysis, and the Type II anhydrous gypsum component is determined as the sum of the Ca component and the S component.

This invention makes it possible to efficiently produce high-purity, fine gypsum from waste gypsum board, thereby expanding the range of uses for the gypsum obtained from waste gypsum board.

1 shows a schematic configuration of a recycling system according to one embodiment. 2 is a flowchart showing the procedure of a method for recycling waste gypsum boards using the recycling system shown in FIG. 1. FIG. 2 is a diagram showing an SEM image of an example of fine gypsum powder produced by the recycling system shown in FIG. FIG. 2 is a graph showing the particle size distribution of an example of fine gypsum powder generated by the recycling system shown in FIG.

The following describes one embodiment of the present invention.

Figure 1 shows the schematic configuration of a recycling system S used in carrying out the method for recycling waste gypsum board. The recycling system S includes a first crushing and separating device 1, a heating device 10, and a second crushing and separating device 20.

The first crushing and separating device 1 includes a hopper 2 that receives waste gypsum board, a crushing unit 3 that crushes the waste gypsum board received by the hopper 2, and a separation unit 4 that separates the crushed pieces crushed by the crushing unit 3. The waste gypsum board includes a gypsum core material and paper attached to the gypsum core material. The crushed pieces crushed by the crushing unit 3 include intermediate gypsum powder obtained by crushing the gypsum core material and paper pieces obtained by crushing or breaking the paper. The separation unit 4 separates the intermediate gypsum powder from the paper, for example, by vibrating a sieve.

The particle size of the intermediate gypsum powder crushed in the first crushing and separation device 1 is not particularly limited, and it may be crushed in a relatively coarse state (with a large variation in particle size). The particle size of the intermediate gypsum powder may be, for example, 15 mm or less, or approximately 5 mm or less. However, since fine crushing of the intermediate gypsum powder in the first crushing and separation device 1 enables smooth and accurate processing by the second crushing and separation device 20 in the subsequent stage, it is desirable for the particle size of the intermediate gypsum powder to be approximately 5 mm or less.

A general gypsum board crushing device may be used as the first crushing and separating device 1. For example, a gypsum board processing system manufactured by Towa Kogyo Co., Ltd. or a gypsum board separator manufactured by Hosoda Kikaku Co., Ltd. may be used as the first crushing and separating device 1. However, the specific configuration of the first crushing and separating device 1 is not particularly limited.

The heating device 10 heats the intermediate gypsum powder pulverized in the first pulverizing and separating device 1. The heating device 10 heats the intermediate gypsum powder to convert it into Type II anhydrous gypsum, and also heats it to burn off any residues, including paper and/or plastic, contained in the intermediate gypsum powder.

The intermediate gypsum powder pulverized in the first pulverizing and separating device 1 is what is known as gypsum dihydrate (CaSO4·2H2O). High-temperature heating is required to ensure that the gypsum dihydrate is converted into type II anhydrous gypsum and that the paper and plastic contained in the intermediate gypsum powder are burned away. Therefore, it is preferable that the heating device 10 be capable of heating the intermediate gypsum powder to 700°C or higher, and preferably 800°C or higher. However, there are no particular limitations on the heating temperature, as long as the gypsum dihydrate can be reliably converted into type II anhydrous gypsum.

A kiln (rotary kiln) may be used as the heating device 10. However, the specific configuration of the heating device 10 is not particularly limited, and other furnaces or kilns may also be used.

The second crushing and separating device 20 receives the intermediate gypsum powder heated by the heating device 10 and crushes it. The second crushing and separating device 20 is composed of an airflow crusher with a classification function.

In detail, the second crushing and separating device 20 includes an inlet 21 that receives intermediate gypsum powder, a fine crushing section 22 that crushes the intermediate gypsum powder received from the inlet 21 into fine gypsum powder, a classification section 23 that separates components with larger particle diameters from the fine gypsum powder crushed by the fine crushing section 22, a collection section 24 that collects the larger particle diameter components separated by the classification section 23, and an outlet 25 for removing the fine gypsum powder.

The fine crushing section 22 includes a rotor with blades, and the rotating rotor creates a swirling flow that breaks down the intermediate gypsum powder and causes particles of the intermediate gypsum powder to collide with each other, thereby crushing the intermediate gypsum powder into a fine powder state. The classification section 23 separates the fine gypsum powder crushed in the fine crushing section 22 from the residue, including sand, contained in the intermediate gypsum powder. In this embodiment, the classification section 23 has a structure that allows the fine gypsum powder crushed in the fine crushing section 22 to pass downstream and forms a clearance that restricts the downstream passage of components with particle sizes larger than the fine gypsum powder. In this structure, components that are restricted from passing by the classification section 23 are either crushed again by the fine crushing section 22 or drop out of the fine crushing section 22 and accumulate below the rotor of the fine crushing section 22. In particular, components that cannot be crushed into fine gypsum powder gradually accumulate below the rotor. However, the classifying section 23 may also be configured to use, for example, air drag and centrifugal force to move residue radially outward and discharge fine gypsum powder in the axial direction of the rotor.

The present invention envisions obtaining fine gypsum powder from intermediate gypsum powder, in which 80% or more of the components in the particle size distribution have particle sizes of 50 μm or less, preferably 25 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. To achieve this fine pulverization, the second pulverizing/separating device 20 adjusts the rotation speed, classification clearance, raw material input amount (intermediate gypsum powder input amount), air volume, and other parameters. When the above particle size distribution is achieved, the particle sizes of many of the components in the fine gypsum powder will be 20 μm or less. Sand particle sizes are generally approximately 20 μm to 2 mm. When pulverization and classification are performed with the above particle size distribution in mind, the classifier 23 can accurately separate the sand-containing residue from the fine gypsum powder. This prevents residue from being mixed into the fine gypsum powder.

To obtain fine gypsum powder with the above particle size distribution, the classification clearance in the classification section 23 of the second crushing and separating device 20 in this embodiment is set to between 1.5 μm and 3.0 mm, preferably between 1.5 mm and 2.5 mm, more preferably between 1.75 mm and 2.25 mm, specifically 2 mm in this example. This clearance is set to accurately separate residues, including sand. Specifically, the above particle size distribution is considered excessive in light of the applications of fine gypsum powder described below (resin processing, cement, etc.). However, fine gypsum powder with larger particle sizes can also be used with sufficient practicality, and the classification clearance may be greater than the above range. However, to efficiently achieve both particle size reduction and removal of residues, including sand, it is desirable to set the classification clearance to between 1.5 μm and 3.0 mm, preferably between 1.5 mm and 2.5 mm, more preferably between 1.75 mm and 2.25 mm, specifically 2 mm in this example. However, there are no particular limitations on the classification clearance value.

Furthermore, the fine gypsum powder pulverized by the fine pulverization section 22 of the second pulverization/separation device 20, which is an airflow pulverizer, loses its needle-like or plate-like crystal form and tends to become fine granules.

In this embodiment, the residue separated by the classification unit 23 is not circulated as in a typical airflow mill, but is instead collected by the collection unit 24. This prevents the residue from being mixed into the fine gypsum powder that is ultimately removed from the outlet 25. However, the residue collected by the collection unit 24 also contains gypsum components, which may be re-introduced into the inlet 21 for effective use. In this case, it is desirable to remove sand from the residue before re-introducing it into the inlet 21. Furthermore, when removing the fine gypsum powder from the outlet 25, applying vibration to the outlet 25 makes it easier to remove the fine gypsum powder. Although not shown, a vibration generator is provided at the outlet 25, and vibration is applied at a predetermined frequency.

A variety of airflow crushers can be used as the second crushing and separating device 20, but a collection section 24 is additionally provided. For example, the Serenmirror MKCL8-20 (registered trademark) manufactured by Masuko Sangyo Co., Ltd. may be used as the second crushing and separating device 20.

Figure 2 is a flowchart showing the steps of the method for recycling waste gypsum board using the recycling system S. The steps of the method for recycling waste gypsum board according to this embodiment are described in detail below.

First, in step S1, a first crushing and separation process is performed in which waste gypsum board containing a gypsum core material and paper attached to the gypsum core material is crushed and the gypsum core material is crushed to separate intermediate gypsum powder from paper fragments. In this example, the first crushing and separation process crushes the intermediate gypsum powder so that 80% or more of the intermediate gypsum powder components are 5 mm or less in particle size distribution. In this example, the first crushing and separation process is performed using a gypsum board separator manufactured by Hosoda Kikaku Co., Ltd. as the first crushing and separation device 1.

In step S2, the intermediate gypsum powder obtained in the first crushing and separation process is heated by the heating device 10 to convert it into type II anhydrous gypsum, and a heating process is performed to burn off residues, including paper and/or plastic, contained in the intermediate gypsum powder. In this example, the intermediate gypsum powder is heated at 800°C or higher for 3 hours or more. In this example, a kiln (rotary kiln) is used as the heating device 10 to perform the heating process.

In step S3, the intermediate gypsum powder after the heating process is crushed and the residue is separated in a second crushing and separation process. Specifically, in the second crushing and separation process, the intermediate gypsum powder is crushed into fine gypsum powder using the second crushing and separation device 20, which is an airflow crusher, and the residue, including sand contained in the intermediate gypsum powder, is separated in the classification section 23, and then collected and separated from the fine gypsum powder.

In the second crushing and separation process, foreign matter (residue) is removed at the same time as the intermediate gypsum powder is crushed, allowing the desired high-purity fine gypsum powder to be extracted efficiently and easily, significantly reducing takt time compared to using a sieve, for example.

Figure 3(A) shows an SEM image of an example of fine gypsum powder produced by the recycling system S (produced in step S3 above). Figure 3 shows that the fine gypsum powder is non-acicular and non-plate-like, forming fine granules. Furthermore, as is clear from comparison with the scale in Figure 3, the particle diameters of many of the components of the fine gypsum powder are 10 μm or less. On the other hand, Figure 3(B) is an SEM image of an example of gypsum powder after being crushed by the first crushing and separation device 1 but before heating. In the state shown in Figure 3(B), many linear crystals remain in the gypsum powder, and the particle diameters are large, with many of them forming clumps.

Table 1 below shows the measurement results of the particle size distribution of the fine gypsum powder produced by the recycling system S. Table 1 below shows the measurement results when grinding was performed using two different operating patterns, first and second. The difference between the first and second operating patterns is the amount of intermediate gypsum powder added: 2.00 kg in the former and 3.46 kg in the latter.

On the other hand, Table 2 below shows the particle size distribution of gypsum powder when the first pulverization and separation process and the second pulverization and separation process were performed without the heating process, as a comparative example.

As shown in Table 2, the gypsum powder of the comparative example contains only about half of the components with particle sizes of 20 μm or less, and also contains components with significantly larger particle sizes. In the comparative example, heating was performed after the second crushing and separation process to convert the gypsum powder into type II anhydrous gypsum, but the resulting type II anhydrous gypsum is expected to have large particle sizes and contain some that retain the morphology of needle-like or plate-like crystals. Therefore, the characteristics of the type II anhydrous gypsum obtained based on the comparative example are expected to be significantly different from the characteristics of the fine gypsum powder obtained according to this embodiment. In the comparative example, the heating process was not performed before the second crushing and separation process, so plastic adhered to the rotor of the fine crushing section 22, and it is believed that this phenomenon prevented the expected fine crushing.

Figure 4(A) shows a graph representing the particle size distribution shown in Table 1, and Figure 4(B) shows a graph representing the particle size distribution shown in Table 2. The line indicated by the symbol A in Figure 4(A) shows the particle size distribution of fine gypsum powder pulverized using the first operating pattern, and the line indicated by the symbol B shows the particle size distribution of fine gypsum powder pulverized using the second operating pattern. The line indicated by the symbol C in Figure 4(B) shows the particle size distribution of gypsum powder in the comparative example. As is clear from Figures 4(A) and (B), the pulverization process according to this embodiment can stably produce fine gypsum powder of 10 μm or less.

Returning to Figure 2, the fine gypsum powder produced in step S3 may be mixed with a resin composition, for example, in step S10. Then, in step S11, a resin processed material containing the fine gypsum powder and the resin composition may be produced. The resin processed material produced here may be a simple mixture of the fine gypsum powder and the resin composition, or it may be produced as pellets in which the fine gypsum powder is mixed with the resin composition and hardened.

The resin composition used in the raw material for the resin processed product is not particularly limited, but a thermoplastic resin is preferable. For example, the resin composition may be one of polyolefin resins such as polypropylene, high-density polyethylene, and low-density polyethylene, vinyl resins such as polyvinyl chloride, and polyester resins such as polyethylene terephthalate, or a mixture of two or more of these. The resin composition may also be a thermosetting resin, a photocurable resin, or the like.

The resin processed material described above may be used as a molding material for a resin processed product in step S12. For example, the resin processed material can be melted and then hardened to form a resin processed product.

Furthermore, the fine gypsum powder produced in step S3 may be mixed with lime, for example, in step S20. Then, in step S21, a cement raw material containing the fine gypsum powder and lime may be produced. The cement raw material may then be used as a raw material for concrete in step S22.

Furthermore, the fine gypsum powder produced in step S3 may be used in fields other than resin processed products and cement raw materials (for example, the medical field or the food field) (see Figure 1). Because the fine gypsum powder obtained in this embodiment is highly pure, it has the potential to be used in the medical and food fields as well.

In the waste gypsum board recycling method according to the present embodiment described above, the intermediate gypsum powder is converted into type II anhydrous gypsum in the heating process (step S2), and the residue, including paper and/or plastic, contained in the intermediate gypsum powder is burned. During this process, impurities are removed. Furthermore, in the subsequent second crushing and separation process (step S3), foreign matter (residue) is removed simultaneously with the crushing of the intermediate gypsum powder. This allows the desired high-purity fine gypsum powder to be extracted efficiently and easily, significantly reducing takt time compared to, for example, using a sieve. Therefore, high-purity, fine gypsum powder can be easily obtained. Furthermore, in the second crushing and separation process (step S3), the intermediate gypsum powder from which the plastic was burned in the heating process is crushed. This prevents plastic from adhering to the rotor of the fine crushing unit 22, etc., and therefore allows the crushing process to be carried out efficiently and in the desired state, further extending the life of the equipment and reducing maintenance burden.

Therefore, the waste gypsum board recycling method according to this embodiment makes it possible to efficiently produce high-purity, fine gypsum from waste gypsum board, thereby expanding the range of uses for the gypsum obtained from waste gypsum board.

The fine gypsum powder obtained from the waste gypsum board recycling method according to this embodiment can be used, for example, as a raw material for resin processed products. In this case, because the fine gypsum powder is type II anhydrous gypsum, it does not change into gypsum hemihydrate, making it effective for long-term storage of the raw material for resin processed products. Furthermore, because it is fine (and because it is not a needle-shaped or plate-shaped crystal), it does not affect the shape of the finished product, for example, when molding the resin processed product by heating. This allows for the production of high-quality resin processed products, expanding their uses.

Fine gypsum powder obtained by the waste gypsum board recycling method according to this embodiment can be used, for example, as a cement raw material. In this case, because the fine gypsum powder is type II anhydrous gypsum, it does not change into gypsum hemihydrate, making it effective for long-term storage of cement raw materials. Furthermore, because it is fine (and because it is not needle-shaped or plate-shaped crystals), when concrete is produced, it is possible to avoid the inclusion of air bubbles or voids in the concrete, thereby providing concrete with a good finish.

The fine gypsum powder obtained by the waste gypsum board recycling method according to this embodiment loses its needle-like or plate-like crystal form. In other words, the fine gypsum powder is neither needle-like nor plate-like, and becomes a fine granular material. This makes it easier to mix with the resin composition and lime, improving the quality of the final product, which is a notable point.

1...First crushing and separating device, 2...Hopper, 3...Crushing section, 4...Separating section, 10...Heater, 20...Second crushing and separating device, 21...Inlet, 22...Fine crushing section, 23...Classifying section, 24...Collection section

Claims (2)

A first crushing and separating process of crushing waste gypsum board including a gypsum core material and paper attached to the gypsum core material, and separating the gypsum core material into intermediate gypsum powder and the paper;
A heating step of heating the intermediate gypsum powder at 800°C or higher to convert it into type II anhydrous gypsum and burning off residues containing paper and/or plastic contained in the intermediate gypsum powder;
A second crushing and separation process in which the intermediate gypsum powder after the heating process is crushed into fine gypsum powder by an airflow crusher, and a residue containing sand contained in the intermediate gypsum powder is separated from the fine gypsum powder by a classification unit of the airflow crusher.
A raw material preparation step of preparing a resin processed raw material by mixing the fine gypsum powder with a resin composition,
The fine gypsum powder after the second crushing and separation step has a particle size distribution in which 80% or more of the components have a particle size of 10 μm or less, and is non-needle crystals and non-plate crystals. The method for recycling waste gypsum board described in claim 1, wherein the resin processed raw material is produced as pellets by incorporating the fine gypsum powder into the resin composition and hardening it.