Incineration bottom ash treatment method

Abstract

To provide an efficient method for treating incineration main ash.SOLUTION: A method for treating incineration main ash includes: a first process of adding water to incineration main ash having 10 mm or smaller of particle size; a second process of dehydrating the incineration main ash to which water has been added through centrifugal separation; a third process of separating the dehydrated incineration main ash into heavy products and light products through sorting through specific gravity and recovering the light products as cement raw materials; and a fourth process of separating the heavy products sorted in the third process into non-magnetic products and magnetic products through sorting through magnetic force, recovering the non-magnetic products as nonferrous refining raw materials and recovering the magnetic products as electric furnace and blast furnace raw materials.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for treating incineration bottom ash. [Background technology]

[0002] Bottom ash is discharged from the hearth of an incinerator for municipal waste, etc., and is disposed of as general waste by landfilling in a controlled disposal site. However, in recent years, the remaining capacity of the final landfill site has been decreasing, and various effective uses of the bottom ash have been considered.

[0003] For example, a method for treating incineration bottom ash has been proposed in which incineration bottom ash with a maximum particle size of 5 mm or less is separated into conductors and non-conductors by eddy current sorting, the conductors are then separated into high and low specific gravity materials by specific gravity difference sorting, precious metals are recovered as the high specific gravity material, and aluminum is recovered as the low specific gravity material (Patent Document 1).It has also been proposed to add water to the incineration bottom ash to make a slurry, separate the garbage incineration ash slurry into a slurry containing coarse particles and a slurry containing fine particles, subject the slurry containing coarse particles to wet specific gravity sorting to recover precious metals, and demineralize the slurry containing fine particles before recycling it as a cement raw material (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-58059 A [Patent Document 2] JP 2020-110739 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, since the incineration bottom ash contains a lot of moisture and is in a wet state, there are the following problems in processing the incineration bottom ash. That is, if the incineration bottom ash is subjected to physical separation while it is in a wet state, moisture will seep out from the surface of the incineration bottom ash, and the incineration bottom ash will be integrated and formed into aggregates, which will cause adhesion to the device, blockage, etc., making normal operation difficult. As a countermeasure against this, for example, it is possible to apply thermal energy from a dryer or hydration heat energy by adding an admixture to the incineration bottom ash to remove moisture, but the method using thermal energy consumes a huge amount of energy and is costly, and the method using an admixture requires a long time to remove moisture, which greatly reduces the processing capacity of the incineration bottom ash per unit time, and if the amount of the admixture is increased to shorten the processing time, it becomes costly. Furthermore, a method of dehydrating the incineration bottom ash as it is with a centrifuge to reduce the moisture content is also considered, but since the incineration bottom ash contains coarse particles such as metal and slag, the centrifuge is worn out and the filter cloth is damaged severely, making the dehydration process difficult. An object of the present invention is to provide an efficient method for treating incineration bottom ash. [Means for solving the problem]

[0006] In the technical field, as explained above, centrifuges are commonly used for the purpose of dehydrating incineration bottom ash. However, the present inventors have discovered that by intentionally adding water to the incineration bottom ash before feeding it into a centrifuge, not only does it become easier to feed it into the centrifuge, but also centrifugation promotes separation of coarse particles from fine particles, making it possible to efficiently separate and recover valuable materials from the incineration bottom ash.

[0007] That is, the present invention provides the following [1] to [6]. [1] A first step of adding water to incineration bottom ash having a particle size of 10 mm or less; A second step of dehydrating the incineration bottom ash after adding water by centrifugation; A third step of separating the dehydrated incineration bottom ash into heavy products and light products by gravity separation and recovering the light products as a cement raw material; The fourth process is to separate the heavy products from the third process into non-magnetic and magnetic products by magnetic separation, recovering the non-magnetic products as non-ferrous smelting raw materials and recovering the magnetic products as electric furnace and blast furnace raw materials. Equipped with How to dispose of incineration bottom ash. [2] The method for treating incineration bottom ash according to [1] above, wherein in the first step, water is added in an amount equal to or more than one mass of the incineration bottom ash. [3] A method for treating incineration bottom ash according to [1] or [2] above, in which in the second step, the incineration bottom ash after adding water is screened and the remaining part is dehydrated by centrifugation. [4] The method for treating incineration bottom ash according to [3] above, wherein the sieve separation is carried out using a sieve with mesh sizes of 1 mm or less. [5] A method for treating incineration bottom ash according to any one of [1] to [4] above, in which the slurry obtained by separating the incineration bottom ash after adding water by centrifugation is separated into heavy products and light products by wet specific gravity separation, and the heavy products are recovered as non-ferrous smelting raw materials and the light products are recovered as cement raw materials. [6] A method for treating incineration bottom ash according to any one of [1] to [5] above, in which the incineration bottom ash after adding water is screened, and the undersize fraction is separated into heavy products and light products by wet specific gravity separation, and the heavy products are recovered as non-ferrous smelting raw materials and the light products are recovered as cement raw materials. [7] The method for treating incineration bottom ash according to any one of [1] to [6] above, further comprising a preparation step of separating incineration bottom ash having a particle size of 10 mm or less from the incineration bottom ash prior to the first step. Effect of the Invention

[0008] According to the present invention, valuable materials can be efficiently separated and recovered from incineration bottom ash. [Brief description of the drawings]

[0009] [Figure 1] 1 is a flowchart showing an example of a method for treating incineration bottom ash according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The method for treating incineration bottom ash of the present invention comprises steps 1, 2, 3 and 4. Each step will be described in detail below, and an example of the method for treating incineration bottom ash of the present invention is shown in Figure 1.

[0011] [First step] The first step is to add water to the bottom ash with a particle size of 10 mm or less. Incineration bottom ash is wet ash containing a lot of moisture, and may contain moisture as high as 18% to 35%. Therefore, when treating incineration bottom ash, it is common to remove moisture from the incineration bottom ash to improve its handleability, but the present inventors have unexpectedly found that adding moisture to the incineration bottom ash makes it easier to separate valuable materials contained in the incineration bottom ash. That is, incineration bottom ash in a wet state may be aggregated and coarsened due to vibrations of the device when performing physical separation. Coarsened incineration bottom ash is prone to blockage in the device, which leads to a decrease in processing efficiency, but incineration bottom ash to which water has been added does not become coarse, so it is easy to supply to the processing device, and it has been found that separation of coarse particles and fine particles can be promoted by centrifugation. Here, in this specification, "incineration bottom ash" refers to the incineration residue (bottom ash) that accumulates at the bottom of the incinerator when urban waste or industrial waste is incinerated in the incinerator. Therefore, the "incinerator bottom ash" according to the present invention does not include incineration fly ash, which is soot in the exhaust gas during incineration. Examples of industrial waste include shredder dust from discarded automobiles, discarded home appliances, vending machines, and office equipment, as well as waste plastics such as construction waste plastics, agricultural waste plastics, fishing waste plastics, and marine waste plastics.

[0012] First, the particle size of the incineration bottom ash is adjusted to prepare the incineration bottom ash to be used in the first step. The particle size can be adjusted by using, for example, a crusher or a classifier, or these may be combined. Examples of crushers include jaw crushers, impact crushers, hammer crushers, roll crushers, and rotary crushers. In order to adjust the particle size of the incineration bottom ash, the crusher is equipped with a screen with a desired sieve mesh, or if no screen is installed, the fixed teeth, rotating teeth, inner wall, etc. may be adjusted to the desired clearance. Examples of classifiers include vibration sieves such as ripple flow type and low head type, rotary sieves such as trommels, and wet classifiers such as spiral classifiers, and the desired sieve mesh may be used.

[0013] The particle size of the incineration bottom ash after particle size adjustment is 10 mm or less, but from the viewpoint of preventing wear and damage inside the device, it is preferably 8 mm or less, more preferably 7 mm or less, and even more preferably 6 mm or less. Note that, although there is no particular lower limit for the particle size of the incineration bottom ash, from the viewpoint of preventing clogging of the sieve mesh, it is preferably 0.3 mm or more, more preferably 0.5 mm or more, and even more preferably 1 mm or more.

[0014] Next, water is added to the particle size-adjusted incineration bottom ash. Any common method can be used as the water addition method, and is not particularly limited. For example, in addition to the method of adding water when the incineration bottom ash is fed into the centrifuge, the incineration bottom ash can be stored in an agitation tank and water can be added or sprayed to the incineration bottom ash and agitated, or water can be added or sprayed to the incineration bottom ash at the entrance of a conveyor, on the conveyor, or at a transfer point during transport. In particular, agitating the incineration bottom ash and water in the agitation tank can break up ash lumps and peel off fine particles attached to coarse particles, making it easier to separate the coarse particles from the fine particles in the centrifuge. The agitator can be a device that can be continuously charged and discharged, such as a device with a structure that rotates a horizontal cylindrical drum (a container with a bar for scraping on the inside, a container with a structure in which a rod or ball is inserted or a shaft with a protrusion or blade is inserted to promote separation of fine particles from the mud or coarse particles, etc.), or a single-shaft or double-shaft batch mixer used for mixing concrete can be used. Considering the effect of beating and the possibility of continuous treatment, it is more effective to use a horizontal cylindrical drum. Water may be added to the bottom ash either intermittently or continuously.

[0015] Examples of water include tap water as specified in JIS A 5303 Appendix C, and water other than tap water (e.g., river water, lake water, well water, groundwater, industrial water). In addition, the water may be any of cooling water, room temperature water, and hot water, and is not particularly limited.

[0016] The amount of water added is preferably 1 mass or more, more preferably 2 mass or more, and even more preferably 3 mass or more, relative to the incineration bottom ash. If the amount of water added to the incineration bottom ash is too small, the fluidity of the incineration bottom ash decreases, and the handling property is likely to decrease due to blockage or the like in the next process. On the other hand, if the amount of water added is too large, not only the work efficiency decreases but also the cost increases, so the amount of water added is preferably 20 mass or less, more preferably 15 mass or less, and even more preferably 10 mass or less, relative to the incineration bottom ash.

[0017] In this process, the incineration bottom ash after adding water may be screened and the remaining part may be subjected to the next process. This further promotes the separation of coarse particles and fine particles by centrifugal separation, making it easier to screen and recover valuable materials from the incineration bottom ash. For the sieve separation, for example, the vibrating sieve, rotary sieve, and wet classifier described above can be used, but are not limited thereto. The mesh size of the sieve used for sieving is preferably 0.5 to 1 mm, more preferably 0.3 to 0.5 mm, and even more preferably 0.3 mm, from the viewpoints of further promoting the separation of coarse particles from fine particles and preventing clogging. In addition, from the viewpoint of handling, it is preferable to add water again to the sieved portion of the incineration bottom ash after adding water to improve the fluidity. The amount of water to be added can be appropriately selected as long as the fluidity is equivalent to that when water was added to the incineration bottom ash.

[0018] [Second step] The second process is a process in which the incineration bottom ash from the first process is dehydrated by centrifugation. Water and ash can be separated by centrifugation, but since the fine ash containing a lot of moisture (high in Ca, S, and Cl) moves to the water side, the ash, which is mainly coarse and contains more Si, Al, Fe, Cu, and Zn than the fine particles, can be recovered as a dehydrated product with a good moisture content. In addition, since the moisture content of the dehydrated product is low at less than 18% and there are fewer fine particles, it can be sent to the next process without using thermal energy, etc., making it easy to recover valuable materials.

[0019] The centrifuge may be a centrifugal settler or a centrifugal dehydrator, but a centrifugal dehydrator, which can separate ash and water by passing water through the mesh of a screen, can transfer more fine ash to the water side, thereby reducing the moisture content of the ash more. In addition, if this process is performed multiple times, the moisture reduction effect increases.

[0020] There are various types of centrifugal dehydrators, such as a cylindrical basket type and a conical basket type, but the type is not particularly limited. Examples of filter media for the centrifugal dehydrator include filter cloth and screen. In particular, the use of a screen with a pore size of 0.05 mm or more allows for efficient dehydration. Examples of materials for the filter cloth include polypropylene and polyethylene, and examples of materials for the screen include stainless steel and Hastelloy. The centrifugal force in the centrifugal filtration is usually 100 to 2000 G, but from the viewpoint of dehydration efficiency, 200 to 1000 G is preferable, and 200 to 800 G is more preferable.

[0021] There are various types of centrifugal settlers, such as a straight barrel type, a decanter type, and a disk type, but the type is not particularly limited. The centrifugal force in the centrifugal sedimentation is usually 500 to 4000 G, but from the viewpoint of dehydration efficiency, it is preferably 1000 to 3000 G, and more preferably 1500 to 2500 G.

[0022] This step may be carried out two or more times. In this case, the recovered dehydrated product is subjected to the same water addition as in the first step, and then this step is carried out again. This not only removes fine particles that could not be removed in one dehydration step, but also further reduces the water content. The slurry in this step may contain a large amount of fine particles. Therefore, the present invention may include a step of recovering solid matter from the slurry. The dehydration treatment may be performed using, for example, a centrifuge, and preferably a centrifugal settler. The dehydration treatment may be performed multiple times.

[0023] After this step, the dehydrated material is collected from the centrifuge, and the collected dehydrated material can be subjected to a surface modification step in which air is blown onto the material to further reduce the water content. After this step, instead of or in addition to the surface modification step, the collected dehydrated material can be screened and separated into two or more particle groups, and each particle group can be subjected to the next step.

[0024] [Third step] The third process is to separate the dehydrated incineration bottom ash into heavy and light products by gravity separation, and to recover the light products as a cement raw material. The specific gravity separator may be a known specific gravity separator, and may be either a dry type or a wet type. A dry type table type specific gravity separator is preferred, and an air table type is more preferred. In gravity separation, for example, when an air table is used, the dehydrated incineration bottom ash supplied to the top surface of the vibrating table is raised from the top surface of the vibrating table by the air flow passing through the vibrating table, and the heavy products with a high specific gravity move to the lower layer and the light products with a low specific gravity move to the upper layer due to the vibration applied in the inclination direction of the vibrating table, and the heavy products in the lower layer move diagonally upward due to frictional force and vibration force from the top surface of the vibrating table, while the light products in the upper layer are swept diagonally downward without being subjected to frictional force and vibration force from the top surface of the vibrating table, and the heavy products and light products are discharged separately from the vibrating table. Then, the heavy products are subjected to the next process, and the light products are recovered as cement raw materials. As shown in the examples below, the light products are rich in calcium and can be reused as cement raw materials.

[0025] In addition, in this process, when the incineration bottom ash after adding water is screened and the dehydrated matter obtained by dehydrating the sieve by centrifugation is subjected to gravity separation, the dehydrated matter has a sufficiently reduced moisture content, so that the heavy product can be easily recovered by processing with a gravity separator. This heavy product is a particle group in which precious metals are particularly concentrated, and valuable metals such as Au, Ag, Cu, and Fe can be concentrated and recovered, and cement-repellent components such as Cr and Pb can also be recovered in the heavy product. As described above, the dehydrated matter has a sufficiently reduced moisture content, so that it can be subjected to gravity separation as it is, but it is better to dry the wet particle surfaces before performing gravity separation, as this has the effect of suppressing adhesion of particles to each other and settling on the deck of the gravity separator, so that a blower may be used on the conveyor or processing may be performed with a wind separator.

[0026] [Fourth step] This is the process where the heavy products from the third process are separated into non-magnetic and magnetic materials by magnetic separation, and the non-magnetic materials are recovered as non-ferrous smelting materials, and the magnetic materials are recovered as electric furnace and blast furnace materials. This makes it possible to reuse valuable metals. For the magnetic separation, a known magnetic separator can be used, and for example, any of a drum type, a pulley type, and a hanging type may be used, without any particular limitation. In magnetic separation, for example, heavy products are fed onto a drum with a permanent magnet inside, and the magnetic materials contained in the heavy products are attracted to the drum surface, carried by the rotation of the drum, and discharged from the magnetic material discharge port. On the other hand, non-magnetic materials contained in the heavy products are separated from the drum surface by the rotation of the drum and fall, and discharged from the non-magnetic material discharge port. The non-magnetic materials are then recovered as non-ferrous smelting materials, and the magnetic materials are recovered as electric furnace and blast furnace materials. As shown in the examples below, the non-magnetic materials are rich in valuable metals such as Au, Ag, Cu, and Fe, and can be reused as non-ferrous smelting materials. The magnetic materials are also rich in stainless steel, iron, and the like, and can be reused as electric furnace and blast furnace materials.

[0027] From the viewpoint of promoting separation of non-magnetic materials and magnetic materials, the surface magnetic flux density of the magnetic separator is preferably from 700 to 10,000 gausses, more preferably from 1,000 to 7,500 gausses, and even more preferably from 1,500 to 5,000 gausses.

[0028] By treating the bottom ash in this manner, valuable materials can be efficiently separated and recovered from the bottom ash.

[0029] Although the present invention has been described in detail based on the embodiments, the present invention is not limited to the above embodiments. Various modifications of the present invention are possible within the scope of the present invention. For example, the undersize separated by sieving the incineration bottom ash after dehydration in the first step and the slurry separated by centrifugation in the second step contain a large amount of fine particles derived from the incineration bottom ash, and these may be recovered. More specifically, one or more selected from the undersize separated by sieving the incineration bottom ash after dehydration in the first step and the slurry separated by centrifugation in the second step can be separated into heavy products and light products by wet specific gravity separation, and the heavy products can be recovered as non-ferrous refining raw materials and the light products can be recovered as cement raw materials. EXAMPLES

[0030] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples.

[0031] 1.Analysis of Au, Ag, Fe, and Cr The analysis was conducted in accordance with the analytical methods for ores, JIS M 8100 to 8200.

[0032] 2. Analysis of S, CaO, SiO2, Al, Cu, Pb, and Cl The analysis was performed using a fundamental parameter method with an X-ray fluorescence analyzer (Rigaku, ZSX Primus II).

[0033] Example 1 (preparation process) The incineration bottom ash separated by the existing equipment of the factory was sieved with a sieve with a mesh size of 25 mm. Next, the incineration bottom ash below the sieve was sieved with a cylindrical vibrating sieve (Kowa Kogyosho, KF-1000-3D, screen 10 mm), and 50.0 kg of the ash below the sieve was collected. The moisture content below the sieve was 25.0 mass%. (First step) To 50 kg of the undersize material, 150 L (three times the amount) of water was added and thoroughly stirred to obtain a uniform slurry. (Second step) The slurry was fed to a centrifugal dehydrator (Kotobuki Giken Kogyo Co., Ltd., N452K, screen 0.3 mm, centrifugal acceleration 300 G) for dehydration, and 41.5 kg of dehydrated material was recovered. The moisture content of the dehydrated material was 16.5 mass%. (Third step) 41.5 kg of the dehydrated material was fed to a dry density separator (SHB-4 manufactured by Harada Sangyo Co., Ltd.) for density separation processing, and 2.0 kg of heavy products and 39.5 kg of light products were recovered. (Fourth step) The heavy product recovered in the third step was supplied to a drum-type magnetic separator (Nihon Magnetics, RENS-φ318×350L, 3000 Gauss) for magnetic separation, recovering 0.95 kg of non-magnetic material and 1.05 kg of magnetic material.

[0034] Example 2 (First step) The dehydrated product obtained by carrying out the preparation step, the first step, and the second step under the same conditions as in Example 1 was again hydrated under the same conditions as in Example 1 and thoroughly stirred to obtain a uniform slurry. (Second step) The slurry was dehydrated using a centrifugal dehydrator under the same conditions as in Example 1, and the dehydrated product was recovered. The water content of the dehydrated product was 13.3 mass%. (Third step) The dehydrated material was subjected to density separation processing using a dry density separator under the same conditions as in Example 1, and heavy products and light products were recovered. (Fourth step) The heavy product was subjected to magnetic separation processing using a drum-type magnetic separator under the same conditions as in Example 1, and non-magnetic materials and magnetic materials were collected.

[0035] Example 3 (preparation process) The undersieve fraction was collected by sieving through a sieve with 25 mm mesh size in the same manner as in Example 1. The moisture content of the undersieve fraction was 25.0 mass%. (First step) The undersize fraction was subjected to the same procedure as in Example 1 to obtain a uniform slurry. (Second step) The slurry was fed to a centrifugal settler (CMS, LCSS-M300-22, centrifugal acceleration 2000G) for dehydration, and the dehydrated product was collected. The water content of the dehydrated product was 17.8 mass%. (Third step) The dehydrated material was subjected to density separation processing using a dry density separator under the same conditions as in Example 1, and heavy products and light products were recovered. (Fourth step) The heavy product was subjected to magnetic separation processing using a drum-type magnetic separator under the same conditions as in Example 1, and non-magnetic materials and magnetic materials were collected.

[0036] Example 4 (First step) The dehydrated product obtained by carrying out the preparation step, the first step, and the second step under the same conditions as in Example 3 was rehydrated under the same conditions as in Example 3 and thoroughly stirred to obtain a uniform slurry. (Second step) The slurry was dehydrated using a centrifugal settler under the same conditions as in Example 3, and the dehydrated product was collected. The water content of the dehydrated product was 16.9 mass%. (Third step) The dehydrated material was subjected to density separation processing using a dry density separator under the same conditions as in Example 1, and heavy products and light products were recovered. (Fourth step) The heavy product was subjected to magnetic separation processing using a drum-type magnetic separator under the same conditions as in Example 1, and non-magnetic materials and magnetic materials were collected.

[0037] Example 5 (preparation process) The undersieve fraction sieved through the 25 mm mesh sieve was collected by the same procedure as in Example 1, except that the undersieve fraction sieved through the 25 mm mesh sieve was sieved through a cylindrical vibrating sieve equipped with a 6 mm screen. The moisture content of the undersieve fraction was 30.0 mass%. (First step) The undersize fraction was subjected to the same procedure as in Example 1 to obtain a uniform slurry. (Second step) The slurry was fed to a centrifugal dehydrator equipped with a 0.4 mm screen, dewatered at a centrifugal acceleration of 400 G, and the dehydrated product was collected. The water content of the dehydrated product was 17.3 mass%. (Third step) The dehydrated material was subjected to density separation processing using a dry density separator under the same conditions as in Example 1, and heavy products and light products were recovered. (Fourth step) The heavy product was subjected to magnetic separation processing using a drum-type magnetic separator under the same conditions as in Example 1, and non-magnetic materials and magnetic materials were collected.

[0038] Example 6 (preparation process) The sieved fraction was collected by the same procedure as in Example 5. The water content of the sieved fraction was 30.0 mass%. (First step) A homogeneous slurry was obtained by the same procedure as in Example 1, except that 50 L (1 volume) of water was added to the undersieve particles. (Second step) The slurry was fed to a centrifugal dehydrator equipped with a 0.4 mm screen, dewatered at a centrifugal acceleration of 700 G, and the dehydrated product was collected. The water content of the dehydrated product was 17.6 mass%. (Third step) The dehydrated material was subjected to density separation processing using a dry density separator under the same conditions as in Example 1, and heavy products and light products were recovered. (Fourth step) The heavy product was subjected to magnetic separation processing using a drum-type magnetic separator under the same conditions as in Example 1, and non-magnetic materials and magnetic materials were collected.

[0039] Example 7 (preparation process) The slurry obtained by carrying out the same operation as in Example 1 on the incineration bottom ash that fell under the sieve with a mesh size of 25 mm was sieved through a sieve with a mesh size of 0.3 mm, and the part that remained on the sieve was collected. The moisture content of the part that remained on the sieve was 35.0 mass%. (First step) The same procedure as in Example 6 was carried out on the sieve to obtain a uniform slurry. (Second step) The slurry was fed to a centrifugal dehydrator equipped with a 0.3 mm screen, dewatered at a centrifugal acceleration of 400 G, and the dehydrated product was collected. The water content of the dehydrated product was 12.1 mass%. (Third step) The dehydrated material was subjected to density separation processing using a dry density separator under the same conditions as in Example 1, and heavy products and light products were recovered. (Fourth step) The heavy product was subjected to magnetic separation processing using a drum-type magnetic separator under the same conditions as in Example 1, and non-magnetic materials and magnetic materials were collected.

[0040] Comparative Example 1 (preparation process) The undersieve fraction sieved through the 25 mm sieve was collected by the same procedure as in Example 1, except that the undersieve fraction sieved through the 25 mm sieve was sieved through a cylindrical vibrating sieve equipped with a 15 mm screen. The moisture content of the undersieve fraction was 24.5 mass%. (First step) The undersize fraction was subjected to the same procedure as in Example 1 to obtain a uniform slurry. (Second step) An attempt was made to dehydrate the slurry using a centrifugal dehydrator under the same conditions as in Example 1, but it was not possible to discharge the dehydrated product, and further attempts were abandoned.

[0041] Comparative Example 2 (preparation process) The undersieve fraction was collected by sieving through a sieve with 25 mm mesh size in the same manner as in Comparative Example 1. The moisture content of the undersieve fraction was 24.5 mass%. (First step) The undersize fraction was subjected to the same procedure as in Example 1 to obtain a uniform slurry. (Second step) An attempt was made to dehydrate the slurry using a centrifugal settler under the same conditions as in Example 3, but it was not possible to discharge the dehydrated product, and further attempts were abandoned.

[0042] Comparative Example 3 (preparation process) The undersieve fraction was collected by sieving through a sieve with 25 mm mesh size in the same manner as in Example 1. The moisture content of the undersieve fraction was 25.0 mass%. (First step) The same operation as in Example 1 was carried out except that 25 L (0.5 times the amount) of water was added to the undersieve particles to obtain a slurry. (Second step) It was not possible to feed the slurry to the centrifugal dehydrator, so further efforts were abandoned.

[0043] The treatment conditions in each of the Examples and Comparative Examples are shown in Table 1. In addition, in each of the Examples and Comparative Examples, the analysis results of the light product (cement raw material) obtained in the third step, and the non-magnetic material (non-ferrous smelting raw material) and the magnetic material (electric furnace and blast furnace raw material) obtained in the fourth step are shown in Tables 2 and 3.

[0044] [Table 1]

[0045] [Table 2]

[0046] [Table 3]

[0047] In Comparative Examples 1 and 2, there was a risk of damage to the centrifuge due to abnormal noise caused by the ingestion of coarse particles, and the slurry could not be discharged from the centrifugal dehydrator or centrifugal settler, making continuous processing difficult. In addition, in Comparative Example 3, the slurry had no fluidity, and therefore the slurry could not be supplied to the centrifugal dehydrator, making continuous processing difficult. In contrast, in Examples 1 to 7, the slurry had fluidity, so it was possible to feed the slurry to the centrifuge and discharge it. In addition, by subjecting the dewatered slurry to gravity separation, it was possible to easily recover cement raw materials as light products, and by subjecting the heavy products to magnetic separation, it was possible to recover non-ferrous refining raw materials as non-magnetic materials and electric furnace and blast furnace raw materials as magnetic materials.

Claims

1. A first step of adding water to incineration bottom ash having a particle size of 10 mm or less in an amount equal to or more than 1 times the mass of the incineration bottom ash; A second step of dehydrating the incineration bottom ash after adding water by centrifugation; A third step of separating the dehydrated incineration bottom ash into heavy products and light products by gravity separation and recovering the light products as a cement raw material; A fourth step of separating the heavy products separated in the third step into non-magnetic and magnetic products by magnetic separation, recovering the non-magnetic products as non-ferrous refining raw materials and recovering the magnetic products as electric furnace and blast furnace raw materials. Equipped with Methods for disposing of incineration bottom ash.

2. 2. The method for treating incineration bottom ash according to claim 1, wherein in the second step, the incineration bottom ash after addition of water is screened and the remaining part is dehydrated by centrifugation.

3. 3. The method for treating incineration bottom ash according to claim 2, wherein the sieve separation is carried out using a sieve having mesh sizes of 1 mm or less.

4. The method for treating incineration bottom ash according to any one of claims 1 to 3, wherein the slurry obtained by separating the incineration bottom ash after adding water by centrifugation is separated into heavy products and light products by wet specific gravity separation, and the heavy products are recovered as non-ferrous smelting raw materials and the light products are recovered as cement raw materials.

5. The method for treating incineration bottom ash according to any one of claims 1 to 4, wherein the incineration bottom ash after adding water is sieved, and the under-sieve fraction is separated into heavy products and light products by wet specific gravity separation, and the heavy products are recovered as non-ferrous smelting raw materials and the light products are recovered as cement raw materials.

6. The method for treating incineration bottom ash according to any one of claims 1 to 5, further comprising a preparation step of separating incineration bottom ash having a particle size of 10 mm or less from the incineration bottom ash prior to the first step.

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