Method of treating waste gypsum board

Abstract

To provide a method of treating a waste gypsum board for recovering, from the waste gypsum board, a gypsum component of a low paper content that can be used as a raw material for cement, having high treatment efficiency in obtaining an intended gypsum component, with the treatment in each of the steps constituting the treatment method being made easy to carry out.SOLUTION: The method of treating a waste gypsum board includes a crushing step of crushing a waste gypsum board to obtain a crushed product, a vibration step of applying vibration to the obtained crushed product to obtain a crushed product subjected to the vibration treatment, and a classification step of classifying the crushed product subjected to the vibration treatment to obtain a crushed product of a smaller particle size having the maximum particle size of 3.0 mm or less. The method may include a coarse particle removal step of classifying the crushed product between the crushing step and the vibration step to obtain a crushed product of a smaller particle size having the maximum particle size in a range of 10 to 50 mm.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for treating waste gypsum board. [Background technology]

[0002] Waste gypsum board is generated as scraps from the interior construction of new buildings and as waste material removed during the renovation or demolition of existing buildings, and is mainly disposed of as non-combustible industrial waste. The amount of waste gypsum board is expected to increase in the future. Under these circumstances, technology has been developed to recycle (reuse) the gypsum contained in waste gypsum board as a raw material for cement, etc.

[0003] For example, Patent Document 1 describes a method for recovering gypsum from waste gypsum boards as a cement raw material, which comprises roughly crushing the gypsum boards and removing paper of 30 mm or more in size, and then using two or more stages of dry sieves with successively smaller sieve openings from top to bottom, with the final sieve having openings of 0.5 mm to 1.8 mm.

[0004] Patent Document 2 describes a method for recycling waste gypsum board, which comprises crushing waste gypsum board, pulverizing and classifying the waste gypsum board (specifically, classifying the waste gypsum board using a dry classifier with a classification point of 100 μm or less), thereby separating the waste gypsum board into gypsum with a high impurity content (coarse powder) and gypsum with a low impurity content (fine powder), producing anhydrous gypsum from the gypsum with a high impurity content (coarse powder), and recovering gypsum dihydrate and / or gypsum hemihydrate from the gypsum with a low impurity content (fine powder). Patent Document 2 also describes how gypsum (fine powder) with low impurity content is washed with water to remove water-soluble impurities and recover gypsum dihydrate, and how the obtained gypsum dihydrate is molded to improve its handleability and shipped as a cement raw material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-228954 A [Patent Document 2] JP 2008-6400 A Summary of the Invention [Problem to be solved by the invention]

[0006] When gypsum components recovered from waste gypsum boards are used as a raw material for cement, if a large percentage of paper derived from the waste gypsum boards remains in the gypsum components, the chemical admixtures will be adsorbed by the paper when preparing concrete containing chemical admixtures such as high-performance water-reducing agents. As a result, the chemical admixtures will not be able to fully exert their performance (e.g., water-reducing effect), and in order to compensate for this, the amount of chemical admixture added must be increased.

[0007] On the other hand, when the technology described in the above-mentioned Patent Document 1 is adopted to solve this problem, the final sieve has a small mesh size of 0.5 to 1.8 mm, so the efficiency of the process to obtain the target gypsum (gypsum as a cement raw material) is low. Furthermore, when the technology described in the above-mentioned Patent Document 2 is adopted, classification is performed using a dry classifier with a classification point of 100 μm or less, and only fine powder (gypsum) with a maximum particle size of 100 μm or less (0.1 mm or less) is targeted and recycled as a cement raw material, so the efficiency of the process until the target gypsum (gypsum dihydrate as a cement raw material) is obtained is low.

[0008] The object of the present invention is to provide a method for treating waste gypsum board for recovering a gypsum component with a small paper content from the waste gypsum board, which can be used as a raw material for cement, etc., and which is highly efficient in the process for obtaining the target gypsum component from the waste gypsum board and which is simple in each process that constitutes the treatment method. [Means for solving the problem]

[0009] As a result of intensive research into solving the above-mentioned problems, the inventors have discovered that when a series of processes is carried out in which waste gypsum board is crushed to obtain crushed material, the crushed material is vibrated, and then the fine-particle crushed material having a maximum particle size of 3.0 mm or less is obtained by classification, the fine-particle crushed material can be suitably used as a raw material for cement, etc., and have completed the present invention.

[0010] The present invention provides the following [1] to [6]. [1] A method for treating waste gypsum board, comprising: a crushing step of crushing waste gypsum board to obtain crushed material; a vibration step of applying vibration to the crushed material to obtain crushed material after vibration treatment; and a classification step of classifying the crushed material after vibration treatment to obtain fine-particle crushed material having a maximum particle size of 3.0 mm or less (gypsum component with a low paper content that can be used as a raw material for cement, etc.). [2] The method for treating waste gypsum board described in [1] above, further comprising a coarse fraction removal step between the crushing step and the vibration step, in which the crushed material is classified to obtain fine-particle crushed material having a maximum particle size within the range of 10 to 50 mm.

[0011] [3] The method for treating waste gypsum boards according to [1] or [2] above, wherein the vibration in the vibration step is performed by a sieve shaker, a vibrating conveyor, an air slider, a vibrating sieve, a wave sieve, or a rotating sieve. [4] A method for treating waste gypsum board described in [1] or [2] above, comprising a recycling process in which the fine crushed material obtained in the classification process is used as a raw material for cement or a cement admixture. [5] A method for treating waste gypsum board described in [1] or [2] above, in which the paper content in the fine crushed material obtained in the classification step is 0.3 mass% or less. [6] The method for treating waste gypsum boards according to the above [1] or [2], wherein the maximum particle size of the fine crushed material obtained in the classification step is 1.9 to 2.6 mm. Effect of the Invention

[0012] According to the processing method of the present invention, since it includes a vibration process, the paper removal rate in the classification process is increased, and the efficiency of the processing from waste gypsum board to obtaining the desired gypsum component (specifically, crushed fine particles having a maximum particle size of 3.0 mm or less) can be improved (in particular, the processing time required to obtain a specified amount of gypsum component can be shortened). In particular, if the fine crushed material is classified in the classification process so that the maximum particle size is 1.9 to 2.7 mm, a larger amount of gypsum component with a smaller paper content (usable as a raw material for cement, etc.) can be obtained compared to the technology described in Patent Document 1 mentioned above. Furthermore, the treatment in each step constituting the processing method of the present invention is simple, for example, it can be carried out using a general-purpose device. The obtained gypsum component has a small paper content and can be suitably used as a raw material for cement, etc. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An example of a method for treating waste gypsum board of the present invention includes: (A) a crushing step of crushing waste gypsum board to obtain crushed material; (B) a coarse fraction removal step of classifying the crushed material obtained in step (A) to obtain fine-particle crushed material having a maximum particle size within the range of 10 to 50 mm; (C) a vibration step of applying vibration to the crushed material obtained in step (B) to obtain a crushed material after vibration treatment; (D) a classification step of classifying the crushed material obtained in step (C) to obtain fine-particle crushed material having a maximum particle size of 3.0 mm or less; and (E) a recycling step of using the fine-particle crushed material obtained in step (D) as a cement raw material or a cement admixture. Incidentally, steps (A), (C) and (D) are essential steps in the present invention. Steps (B) and (E) are optional steps in the present invention. Each step will be described in detail below.

[0014] [Process (A): Crushing process] Step (A) is a step of crushing waste gypsum boards to obtain crushed material. A gypsum board is a building component formed by integrally molding a plate-like body containing gypsum as a main component and a gypsum board base paper that covers both sides of the plate-like body. In this specification, the term "waste gypsum board" refers to scraps or waste gypsum board generated during the construction of new buildings or the renovation or demolition of existing buildings. Examples of means for crushing waste gypsum boards include a jaw crusher, a hammer mill, a pulverizer, a roll crusher, a single-shaft crusher, a double-shaft crusher, and a chain crusher.

[0015] [Step (B): Coarse component removal step] Step (B) is a step of classifying the crushed material obtained in step (A) (crushing step) to obtain fine crushed material having a maximum particle size within the range of 10 to 50 mm. An example of a means for classifying the crushed material is a dry sieve with a mesh size in the range of 10 to 50 mm. In this specification, the term "particle size" refers to the size corresponding to the mesh size of a sieve. For example, the undersize fraction obtained by using a dry sieve with a mesh size of 10 mm has a maximum particle size of 10 mm. In this specification, the term "fine particle side" refers to an aggregate of particles on the smaller particle size side after classification, and the term "coarse particle side" refers to an aggregate of particles on the larger particle size side after classification.

[0016] When a dry sieve is used as the classification means, the sieve mesh size is preferably 10 to 50 mm, more preferably 15 to 45 mm, and particularly preferably 20 to 40 mm. If the mesh size is 10 mm or more, the amount of coarse particles removed is not excessive, and the amount of fine crushed material (usable as a raw material for cement, etc.) obtained in the subsequent step (D) (classification step) is larger. If the mesh size is 50 mm or less, the amount of coarse crushed material obtained in step (D) (classification step) is excessive, and the efficiency of the treatment in step (D) can be prevented from decreasing. Step (B) can be omitted, for example, when the particle size of the crushed material obtained in step (A) (crushing step) is 50 mm or less at most.

[0017] [Process (C): Vibration process] Step (C) is a step of applying vibration to the crushed material obtained in step (B) (coarse fraction removal step) to obtain a crushed material after vibration treatment. In the present invention, the crushed material obtained in step (B) (or step (A) if step (B) is not performed) is subjected to vibration, causing repeated collisions between the crushed materials, with the result that the paper (fibrous material) contained in the crushed material (mainly containing gypsum) jumps out of the gypsum and becomes entangled with each other to form aggregates. These aggregates are included in the crushed material on the coarse particle side in step (D) (classification step), and are separated from the crushed material on the fine particle side (material that can be used as a raw material for cement, etc.). Examples of the means for applying vibration to the crushed material include a sieve shaker, a vibrating conveyor, an air slider, a vibrating sieve, a wave type sieve, a rotary type sieve, and the like. Among these, the vibrating conveyor and the air slider are advantageous when the processing method of the present invention is carried out continuously, since they can simultaneously perform vibration processing and movement of the crushed material.

[0018] A sieve shaker is a device that combines the functions of screening and shaking. In the present invention, the sieve shaker is used to collide the granular material (crushed material) to be treated with each other, so a frame (dish-shaped) without mesh openings can be used instead of a sieve. The vibration frequency of the sieve shaker is preferably 0.5 to 5 Hz (0.5 to 5 times / second), more preferably 1 to 4 Hz. When the vibration frequency is 0.5 Hz or more, the content of paper in the fine crushed material obtained in step (D) (classification step) becomes smaller. When the vibration frequency is 5 Hz or less, the sieve shaker is easily available (a general-purpose one may be used).

[0019] The amplitude of the sieve shaker is preferably 0.1 to 100 mm, more preferably 0.3 to 80 mm, further preferably 0.5 to 50 mm, and particularly preferably 1 to 30 mm. When the amplitude is 0.1 mm or more, the content of paper in the fine crushed material obtained in step (D) (classification step) becomes smaller. When the amplitude is 100 mm or less, the sieve shaker is easily available (a general-purpose one may be used). In the present invention, when a sieve shaker is used, the effects of the present invention can be obtained even if the vibration is slight (amplitude of, for example, 1 to 3 mm). The time for applying vibration by the sieve shaker is preferably 5 seconds to 2 minutes, more preferably 10 seconds to 1 minute. If the time is 5 seconds or more, the paper removal rate can be increased. If the time is 2 minutes or less, the processing efficiency of the processing method of the present invention can be increased.

[0020] A vibrating conveyor is a device that moves the object being moved, granular material (crushed material), in a specific direction while vibrating it. The vibration frequency of the vibrating conveyor is preferably 5 to 30 Hz (5 to 30 times / second), more preferably 10 to 25 Hz. When the vibration frequency is 5 Hz or more, the content of paper in the fine crushed material obtained in step (D) (classification step) becomes smaller. When the vibration frequency is 30 Hz or less, it is easy to obtain a vibrating conveyor (a general-purpose one will do). The amplitude of the vibration conveyor is preferably 3 to 10 mm, more preferably 4 to 8 mm. If the amplitude is 3 mm or more, the content of paper in the fine crushed material obtained in step (D) (classification step) becomes smaller. If the amplitude is 10 mm or less, it is easy to obtain a vibration conveyor (a general-purpose one will suffice).

[0021] The time for applying vibration by the vibrating conveyor is preferably 5 seconds to 2 minutes, more preferably 10 seconds to 1 minute. If the time is 5 seconds or more, the paper removal rate can be increased. If the time is 2 minutes or less, the processing efficiency of the processing method of the present invention can be increased. The length of the vibration conveyor (the length of the path along which the crushed material is moved) is preferably 0.5 to 10 m, more preferably 1 to 5 m. If the length is 0.5 m or more, the content of paper in the fine crushed material obtained in step (D) (classification step) becomes smaller. If the length is 10 m or less, the vibration conveyor does not become excessively large, which is advantageous in terms of cost.

[0022] An air slider is a device that moves granular material (crushed material) by circulating air in the direction of movement, lifting it up and moving it up a slope with a gradient of 7 to 15 degrees. The length of the air slider (the length of the path along which the crushed material moves as the object to be moved) is preferably 0.5 to 10 m, more preferably 1 to 5 m. If the length is 0.5 m or more, the content of paper in the fine crushed material obtained in step (D) (classification step) becomes smaller. If the length is 10 m or less, the air slider does not become excessively large, which is advantageous in terms of cost.

[0023] A vibrating sieve is a device that vibrates a screen horizontally and vertically to cause the granules (crushed material) to be processed to collide with each other on the screen, thereby increasing the efficiency of sorting the granules as a sieve. A vibration sieve is a device that creates a vibration motion on a mesh mat, causing the granular materials (crushed material) to collide with each other on the mat, thereby increasing the efficiency of sorting the granular materials as a sieve. A rotating sieve is a device that causes a mesh frame to rotate in a horizontal plane, causing the granular materials (crushed material) to collide with each other on the mesh frame, thereby increasing the efficiency of the granular sorting process as a sieve. In the present invention, the vibrating sieve, the wave motion sieve, and the rotary sieve are all used to collide the granular material (crushed material) to be processed with each other, so a frame (dish-shaped) without mesh openings can be used instead of a sieve.

[0024] [Process (D): Classification process] Step (D) is a step of classifying the crushed material obtained in step (C) (vibration step) to obtain fine crushed material having a maximum particle size of 3.0 mm or less. An example of the classification means is a dry sieve with an opening size of 3.0 mm or less. When a dry sieve is used as the classification means, the sieve has an opening of 3.0 mm or less, preferably 0.6 to 2.9 mm, more preferably 1.0 to 2.8 mm, even more preferably 1.5 to 2.7 mm, and particularly preferably 1.9 to 2.6 mm. If the opening exceeds 3.0 mm, the content of paper in the fine-particle-side crushed material obtained in step (D) increases, making it difficult to use the crushed material as a raw material for cement, etc. If the opening is 0.6 mm or more, the amount of the fine-particle-side crushed material obtained in step (D) increases, which is preferable from the viewpoint of recycling the crushed material as a raw material for cement, etc. The paper content in the fine crushed material obtained in step (D) is preferably 0.3 mass% or less, more preferably 0.2 mass% or less, even more preferably 0.15 mass% or less, and particularly preferably 0.12 mass% or less. The paper content can be adjusted by adjusting the vibration conditions (e.g., the time for which vibration is applied) in step (C) (vibration step).

[0025] [Process (E): Recycling process] Step (E) is a step in which the fine-particle crushed material obtained in step (D) (classification step) is used as a cement raw material or a cement admixture. The content of paper in the fine crushed material is small due to step (C) (vibration step), so the fine crushed material can be used as a cement raw material (specifically, gypsum crushed together with cement clinker) or as a cement admixture (material added to cement). EXAMPLES

[0026] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Example 1] The waste gypsum board was crushed using a jaw crusher (product name: BB300; manufactured by Verder Scientific). The crushed material obtained was classified using a dry sieve (mesh size: 30 mm; product name: KFC-800; manufactured by Kowa Kogyo Co., Ltd.) to obtain crushed material A (grain size: 30 mm or less), which is the undersieve fraction. Next, the crushed material A (undersieve fraction) was subjected to vibration for 30 seconds using a sieve shaker (vibration frequency: 3 Hz; amplitude: 1 mm; product name: MRK-RETAC; manufactured by Verder Scientific) to obtain crushed material B after vibration treatment. Next, the obtained crushed material B was divided into three (hereinafter referred to as B-1 to B-3), and each of these crushed materials B-1 to B-3 was classified as follows. The crushed material B-1 was classified using a mesh sieve with 2.5 mm openings to obtain crushed material C (particle size: 2.5 mm or less), which was the undersieve fraction. The crushed material B-2 was classified using a mesh sieve with 1.2 mm openings to obtain crushed material D (particle size: 1.2 mm or less), which was the undersieve fraction. The crushed material B-3 was classified using a mesh sieve with 0.6 mm openings to obtain crushed material E (particle size: 0.6 mm or less), which was the undersieve fraction. For each of the three crushed materials C to E obtained by the above operations, the ratio (unit: mass%) to the mass of crushed material B after vibration treatment (100 mass%) and the paper content (unit: mass%) were calculated.

[0027] The paper content in the crushed material was calculated by the following method. First, the crushed material (eg, crushed material C) was pulverized in a mortar to a particle size of about 20 μm, and a sample weighing 2 g was taken from the resulting crushed material. This sample was added to 180 milliliters of dilute hydrochloric acid (a mixture of 1 part concentrated hydrochloric acid by volume and 5 parts water by volume) and stirred, causing the gypsum content in the sample (including gypsum and paper) to dissolve in the dilute hydrochloric acid solution. Next, this dilute hydrochloric acid (containing paper as a solid content) was filtered using a Buchner funnel, and the solid content (paper) on top of the filter paper was collected. After this solid matter (paper) was dried, its mass was measured. The obtained mass was divided by the mass of the crushed material (for example, crushed material C) (multiplied by 100 as a percentage) to obtain the paper content in the crushed material (unit: mass %).

[0028] [Comparative Example 1] An experiment was carried out in the same manner as in Example 1, except that the vibration treatment using the sieve shaker was not carried out. The above results are shown in Table 1.

[0029] [Table 1]

[0030] From Table 1, it can be seen that in Example 1, the paper content in the crushed materials C to E is smaller than in Comparison Example 1, and crushed materials that can be suitably used as raw materials for cement, etc., are obtained with a particle size of 2.5 mm or less. In particular, in Comparative Example 1, the paper content increases in the order of crushed material E, crushed material D, and crushed material C, and it can be seen that the larger the particle size, the higher the paper content, even if the particle size is within the range of 2.5 mm or less. In this regard, in Example 1, at least as long as the particle size is within the range of 2.5 mm or less, the paper content is almost the same (about 0.10 mass%) regardless of the particle size. Therefore, in the present invention, for example, when a sieve with an opening size of 2.5 mm is used as the sieve used in step (D) (classification step), a large amount (for example, 37.7 mass% in Example 1) of the undersize fraction (a gypsum component that can be used as a raw material for cement, etc.) having a very small paper content can be obtained.

Claims

1. A crushing process for crushing waste gypsum boards to obtain crushed material; A vibration step of applying vibration to the crushed material to obtain a crushed material after vibration treatment; and A classification step of classifying the crushed material after the vibration treatment to obtain fine crushed material having a maximum particle size of 3.0 mm or less; A method for treating waste gypsum board comprising the steps of:

2. 2. The method for treating waste gypsum board according to claim 1, further comprising a coarse fraction removal step between the crushing step and the vibration step, in which the crushed material is classified to obtain fine-particle crushed material having a maximum particle size within a range of 10 to 50 mm.

3. 3. The method for treating waste gypsum boards according to claim 1 or 2, wherein the vibration in the vibration step is performed by a sieve shaker, a vibrating conveyor, an air slider, a vibrating sieve, a wave type sieve, or a rotary type sieve.

4. 3. The method for treating waste gypsum boards according to claim 1 or 2, further comprising a recycling step of using the fine crushed material obtained in the classification step as a raw material for cement or a cement admixture.

5. 3. The method for treating waste gypsum board according to claim 1, wherein the content of paper in the fine crushed material obtained in the classification step is 0.3% by mass or less.

6. The method for treating waste gypsum boards according to claim 1 or 2, wherein the maximum particle size of the fine crushed material obtained in the classification step is 1.9 to 2.6 mm.

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