Method for processing refuse incineration ashes

Abstract

To remove ashes from a magnetic ore and a foreign object to reuse generated waste water.CONSTITUTION: Main ashes from a refuse incineration furnace are processed by means of a magnetic force to select a magnetic ore, and then divided into a non-magnetic foreign object and ashes, and water is added to at least parts of the divided ashes to execute a wet process. The magnetic ore and the foreign object are stored in different water-permeable baskets and water washed. At least part of water-washed waste water is used in the wet process.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] This invention relates to the treatment of the main ash in refuse incineration ash.

Background Art

[0002] It is known to separate metallic foreign substances and solid foreign substances from the main ash in refuse incineration ash and use the remaining ash as a cement raw material or the like. For example, in Patent Document 1 (Patent No. 4979164), the main ash is treated with a sieve having an opening of 20 mm and a magnetic separator to separate large foreign substances and metal from the ash. Next, the ash is pulverized by a pulverizer to an average particle size of 1 mm or less and then treated with a sieve having an opening of 5 mm to separate small solid foreign substances. Thereafter, the undersize component is washed with water to separate the solid content, and the drained liquid is subjected to wastewater treatment.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem of this invention is to separate the main ash into ash, magnetically adherent substances, and foreign substances, remove the ash from the magnetically adherent substances and foreign substances, and further reuse the wastewater generated when removing the ash from the magnetically adherent substances and foreign substances.

Means for Solving the Problems

[0005] In the method for treating refuse incineration ash of this invention, a magnetic separation step of treating the main ash from a refuse incinerator with a magnetic force to select magnetically adherent substances; a sieving step of sieving the main ash after selecting the magnetically adherent substances into non-magnetically adherent foreign substances and ash; a wet step of adding water to at least a part of the ash sieved in the sieving step and treating it; A water washing step of separately accommodating the magnetic adherents and the foreign matters in cages with different water permeabilities and washing them with water, and at least a part of the wastewater generated in the water washing step is used in the wet step, The incineration ash of garbage is separated into magnetic adherents, non-magnetic foreign matters, and ash.

[0006] In this invention, a magnetic separation step, a sieving step, a wet step of adding water to at least a part of the ash sieved in the sieving step and treating it, and a water washing step of separately accommodating the magnetic adherents and the non-magnetic foreign matters in cages with different water permeabilities and washing them with water are performed. Also, at least a part of the wastewater generated in the water washing step is used in the wet step, for example, in a state containing ash. By using the cage with water permeability, it can be easily washed with water. In addition, the wastewater generated in the water washing step can be used in the wet step and reused within the treatment system.

[0007] Preferably, in the wet step, a part of the wastewater generated in the water washing step is used to wet-grind the sieved ash, Another part of the wastewater generated in the water washing step is added to the wet-ground ash, and a desalting treatment is performed in a desalting tank to elute the chlorine content from the ash into the wastewater, The mixture of ash and wastewater generated in the desalting treatment is separated into ash and wastewater by a solid-liquid separation device, The wastewater separated by the solid-liquid separation device is treated by a wastewater treatment device, a part of the treated wastewater is discharged to the outside, and the rest is used in the wet grinding or the desalting treatment.

[0008] Then, the average chlorine concentration of the ash subjected to wet grinding and desalting treatment and the entire ash without these treatments can be reduced, and it can be made within the allowable range of the chlorine concentration in the cement clinker raw material.

[0009] Preferably, after removing dioxins from the fly ash from the garbage incinerator by a dioxin removal device, the desalting treatment is performed in the desalting tank to elute the chlorine content in the fly ash into the wastewater. In this way, the fly ash from the garbage incinerator can also be treated.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0011] Examples for carrying out the present invention are shown below. The scope of this invention should be determined according to the understanding of those skilled in the art, taking into consideration the description in the claims, the description in the specification, and well-known techniques in this field.

Examples

[0012] Example 1 Examples of a method and a system for treating refuse incineration ash are shown in FIGS. 1 to 7, and a first embodiment is shown in FIGS. 1 to 3. As shown in FIG. 1, the receiving hopper 1 receives the main ash from the refuse incineration plant and supplies it to the roll screen 2. The main ash is incineration ash discharged from the bottom of a furnace such as a stoker furnace, and the ash discharged together with the exhaust gas is called fly ash.

[0013] The roll screen 2 is shown in FIGS. 2 and 3. The roll screen 2 includes a plurality of rolls 20. From the roll shafts 24 of each roll 20, a set of a small-diameter flange 21 and a large-diameter flange 22 protrudes in the radial direction. These flanges 21 and 22 may be industrially called disks. And for adjacent rolls 20, 20, the large-diameter flange 22 and the small-diameter flange 21 face each other, and the gap between the facing flanges 21 and 22 is narrow. Also, a plurality of sets of flanges 21 and 22 are provided on each roll 20. There is an opening 25 sandwiched between the left and right flanges 21 and 22 between the roll shafts 24, 24. Ash and small foreign objects in the main ash fall from the opening 25, and large foreign objects are conveyed without passing through the opening 25.

[0014] As shown in FIG. 3, the flanges 21 and 22 are shaped such that the central portion of the side of a polygon from a triangle to a pentagon bulges outward. With flanges 21 and 22 having such a shape, it is difficult for foreign objects to pass through the gap between the flanges 21 and 22. If the size of the opening 25 in the direction parallel to the roll shaft 24 is a, and the size in the perpendicular direction is b, then a:b is preferably about 1:1 to 1:2, for example. The size a is preferably 5 mm or more and 50 mm or less, for example, and the size b is preferably 10 mm or more and 60 mm or less, for example. The rolls 20 rotate in the same direction, and the main ash is conveyed by the rolls 20. The components that have fallen from the opening 25 are defined as the components below the screen, and the components that have not fallen are defined as the components above the screen.

[0015] Adjacent openings 25, 25 are separated by the flanges 21 and 22, and wire-shaped foreign objects cannot pass through the gap between the flanges 21 and 22. For a wire-shaped foreign object to pass through the opening 25, it is necessary to stand up vertically by vibration, but the rolls 20 do not apply vibration to the main ash. For this reason, wire-shaped foreign objects do not pass through the opening 25 and are discharged as components above the screen.

[0016] The number of rolls 20 is arbitrary, and the flanges 21, 22 may be circular instead of polygonal. Also, instead of a combination of a large diameter and a small diameter, flanges of the same diameter may face each other or be arranged alternately between adjacent rolls. However, in the roll screen 2 of FIGS. 2 and 3, since it is difficult for wire-shaped foreign matter to pass between adjacent openings 25, 25, the wire-shaped foreign matter is less likely to mix into the under-screen components.

[0017] The under-screen components that have fallen through the opening 25 in the roll screen 2 and the on-screen components are separated by a magnetic separator to separate magnetic adherents. Since the sizes of the magnetic adherents (mainly metals) are different between the under-screen components and the on-screen components, it is preferable to process them with different magnetic separators 4, 5. The magnetic separators 4, 5 may be electromagnetic or may use a magnetic pulley with a permanent magnet attached to the tip of a belt conveyor to change the falling positions between the magnetic adherents and others.

[0018] The ash and solid foreign matter that have passed through the magnetic separators 4, 5 are passed through a sieve 6 to separate the solid foreign matter from the ash. The sieve 6 is, for example, a vibrating sieve, and the preferred mesh size is 8 mm or more and 25 mm or less, but the type of sieve and the range of mesh size are arbitrary. The ash that has passed through the sieve 6 is stored in a silo 7 or the like, a part of it is shipped as unwashed ash, and the rest is shipped after being subjected to treatments such as wet grinding and water washing for desalting. Also, the magnetic adherents in the magnetic separators 4, 5 are recovered as magnetic adherent foreign matter, and the over-screen components in the sieve 6 are recovered as non-magnetic foreign matter. In this way, it is possible to prevent wire-shaped foreign matter and the like from mixing into the ash shipped through the sieve 6.

[0019] Example 2 Figures 4 and 5 show a second embodiment, which is the same as the embodiments of FIGS. 1 to 3 except for the points specifically noted. In the second embodiment, the components on the screen of the roll screen 2 are crushed by the impact crusher 3. The impact crusher 3, for example, has a plurality of hammers attached to a rotating shaft, and by rotating the rotating shaft, an impact is applied from the hammers to the object to be processed. In the impact crusher 3, the object to be processed is sandwiched between a fixed gate and a rotating hammer, or between the hammers of one rotating shaft and another rotating shaft to apply an impact. Such an impact crusher has been put into practical use as a crusher or a shredder. Note that a crusher that uses a toggle mechanism to sandwich the object to be processed between a movable jaw and a fixed plate and gradually increases the pressure to crush it is not suitable for separating ash and foreign matter.

[0020] A large amount of ash adheres to the foreign matter in the components on the screen. If the ash is not peeled off from the foreign matter, the recovery rate of the ash will decrease, and in some cases, the magnetic adherents cannot be separated by the subsequent magnetic separator due to the adhering ash. Therefore, by applying an impact with the impact crusher 3, the components on the screen (metallic and non-metallic foreign matters) are crushed, and the ash adhering to the foreign matter is peeled off. When an impact is applied, the ash adhering to the foreign matter is peeled off and falls off. In some cases, the ash may enter even inside containers such as empty cans and bottles, but when the container is crushed, the internal ash can be separated from the container. In addition, a part of the ash adhering to the foreign matter is peeled off, and the foreign matter becomes small and light. In addition, lumps of ash are also crushed and can be separated into ash and foreign matter. For these reasons, the magnetic adherent foreign matters can be surely separated by the next magnetic separator 5, and the recovery rate of the ash is also improved. Note that if the material does not pass through the impact crusher 3, the magnetic adherent foreign matters may not be magnetically separated by the magnetic separator 5.

[0021] The magnetically attached substances in the magnetic separators 4 and 5 are collected in the wire cages 8 in the water tank 10 and washed with water. Similarly, the foreign substances remaining on the screen of the sieve 6 are collected in the wire cage 9 in the water tank 11 and washed with water. The wire cages 8 and 9 and the water tanks 10 and 11 are schematically shown in Fig. 4. When water is sprayed on the wire cages 8 and 9, or the wire cages 8 and 9 are vibrated in the water tanks 10 and 11 by a device (not shown), the magnetically attached substances (magnetic substances such as metal) and the ash attached to the non-magnetically attached foreign substances can be dropped. When the ash is dropped, the reuse of the magnetically attached substances and the non-magnetically attached foreign substances becomes easy. The wire cages 8 and 9 only need to be water-permeable and allow water to pass through but not allow foreign substances to pass through, and cages other than wire cages may also be used.

[0022] The ash from which foreign substances and the like stored in the silo 7 have been removed is transported to, for example, a cement factory and used as part of the raw material for cement clinker. There is an upper limit on the chlorine concentration in cement clinker. Therefore, a part of the ash from which foreign substances and the like have been removed is pulverized by a wet pulverizer 13, immersed in water in a desalting tank 14, and the chlorine content is eluted. Next, the ash and moisture are separated by a solid-liquid separation device 15 such as a filter press. In this way, the average salt concentration of the treated ash is reduced within the allowable range. Also, the wastewater separated by the solid-liquid separation device 15 is treated by a wastewater treatment device 16, and after making a part of the wastewater conform to environmental standards, it is discharged. When treating fly ash generated at a waste incineration plant, the dioxin in the fly ash is removed by a dioxin removal device 12. Then, the treated fly ash is treated in the desalting tank 14.

[0023] The washing water used in the water tanks 10 and 11 to separate foreign substances contains ash. Even if the wastewater from the water tanks 10 and 11 is used, for example, in a wet pulverizer 13 or a desalting tank 14 in a state containing ash, it will not contaminate the treatment target or the surrounding devices. Therefore, the wastewater from the water tanks 10 and 11 is reused in the wet steps (wet pulverization or desalting) in the treatment system. When the ash content in the wastewater is high, the wastewater may be treated by the solid-liquid separation device 15. Also, the ash may be sedimented from the wastewater, the supernatant may be used in the above-mentioned wet steps, and the sediment may be treated by the solid-liquid separation device 15. Furthermore, the wastewater can be used in the wet steps without performing the treatment of separating the ash from the wastewater.

[0024] Example 3 Figure 6 shows the third embodiment, which is the same as the embodiments of FIGS. 1 to 3 except for the points to be particularly noted. In the third embodiment, when the amount of foreign matter in the main ash is large, it is processed by a roll screen, and the magnetically attached matter is separated by the magnetic separators 4 and 5. When the amount of foreign matter in the main ash is small, the treatment by the roll screen is omitted, and the main ash is processed by the magnetic separator 4 via the receiving hopper. The amount of foreign matter may be determined for each reception of the incineration ash, or may be determined in advance for each source of the incineration ash. The amount of foreign matter is determined, for example, by passing the incineration ash through a sieve having the same mesh size as the sieve used in the screening step. For example, if the weight ratio of the oversize component to the incineration ash is 10% or more, it is considered that there is a large amount of foreign matter. Since the sieve 6 used in the screening step has a mesh size of, for example, 8 mm or more and 25 mm or less, a sieve having a mesh size of 8 mm or more and 25 mm or less is also used for determining the amount of foreign matter. In the third embodiment, since the treatment by the roll screen 2 and the magnetic separator 5 is omitted for the main ash with less foreign matter, the treatment of the garbage incineration ash is simplified.

[0025] Example 4 Figure 7 shows the fourth embodiment, which is the same as the second embodiment of FIGS. 4 and 5 except for the points to be particularly noted. Also in the fourth embodiment, since the treatment by the roll screen 2, the crusher 3, and the magnetic separator 5 is omitted for the main ash with less foreign matter, the treatment of the garbage incineration ash is simplified compared to the second embodiment.

Explanation of Reference Numerals

[0026] 1 Receiving hopper 2 Roll screen 3 Impact crusher 4,5 Magnetic separators 6 Sieve 7 Silo 8,9 Cylinder 10,11 Water tank 12 Dioxin removal device 13 Wet grinder 14 Desalting tank 15 Solid-liquid separation device 16 Wastewater treatment device 20 Roll 21,22 Flange 24 Roll shaft 25 openings

Claims

1. A magnetic separation step of treating the main ash from a garbage incinerator by magnetism and separating the magnetically attached substances; A screening step of screening the main ash after separating the magnetically attached substances into non-magnetically attached foreign substances and ash; A wet step of adding water to at least a part of the ash screened in the screening step and treating it; A water washing step of accommodating the magnetically attached substances and the foreign substances in separate water-permeable cages and washing them with water, and performing the following steps: Using at least a part of the wastewater generated in the water washing step in the wet step; A method for treating garbage incineration ash, which separates the garbage incineration ash into magnetically attached substances, non-magnetically attached foreign substances, and ash.

2. In the wet step: Using a part of the wastewater generated in the water washing step to wet-grind the screened ash; Adding another part of the wastewater generated in the water washing step to the wet-ground ash, and performing a desalting treatment of eluting chlorine components from the ash into the wastewater in a desalting tank; Separating the mixture of ash and wastewater generated in the desalting treatment into ash and wastewater by a solid-liquid separation device; Treating the wastewater separated by the solid-liquid separation device with a wastewater treatment device, discharging a part of the treated wastewater to the outside, and using the remaining part in the wet grinding or the desalting treatment; The method for treating garbage incineration ash according to Claim 1.

3. After removing dioxins from the fly ash from a garbage incinerator by a dioxin removal device, Eluting the chlorine components in the fly ash into the wastewater by performing a desalting treatment in the desalting tank; The method for treating garbage incineration ash according to Claim 2.

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