Method and System for Treating Incineration Ash of Garbage

Abstract

To separate a foreign matter such as a wire and the like from ashes.CONSTITUTION: Main ashes from a refuse incinerator are processed by a roll screen, and are separated into screen lower components that have fallen to a lower side of the roll screen and screen upper components which have passes an upper side thereof. Next, the screen lower components and the screen upper components are separately processed by magnetic force to sort magnetically attracted substances. The screen lower components and the screen upper components after sorting the magnetically attracted substances are screened into non-magnetically attracted foreign matters and ashes.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] <了 This invention relates to the treatment of the main ash in waste incineration ash.

Background Art

[0002] It is known to separate metal foreign matters and solid foreign matters from the main ash in waste incineration ash and use the remaining ash as cement raw materials or the like. For example, in Patent Document 1 (Patent No. 4979164), the main ash is treated with a sieve having a mesh size of 20 mm and a magnetic separator to separate large foreign matters and metals 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 a mesh size of 5 mm to separate small solid foreign matters as well. Thereafter, the undersize component is washed with water to separate the solid content, and the drainage 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] By the way, the main ash may contain wire-shaped foreign matters. When the wire-shaped foreign matters are applied to a vibrating sieve, which is a typical sieve, the wire-shaped foreign matters may stand up due to vibration and pass through the sieve openings as if dancing. Furthermore, since a large amount of incineration ash adheres to the wire-shaped foreign matters that have passed through the sieve, they may not be adsorbed by the magnetic separator. It is difficult to sufficiently remove the wire-shaped foreign matters with either the vibrating sieve or the magnetic separator, so there is a possibility that the wire-shaped foreign matters may be mixed into cement raw materials or the like.

[0005] An object of this invention is to more reliably separate foreign matters such as wire-shaped ones from the ash.

Means for Solving the Problems

[0006] In this invention's method for processing waste incineration ash, the waste incineration ash is separated into magnetic material, non-magnetic foreign matter, and ash by performing the following steps: a roll screen step, in which the main ash from the waste incinerator is processed by a roll screen to separate it into a lower component that falls below the roll screen and a higher component that passes above the roll screen; a first magnetic separation step, in which the lower and higher components are processed separately by magnetic force to separate the magnetically attached material; and a sieving step, in which the lower and higher components, after the magnetically attached material has been separated, are sieved into non-magnetic foreign matter and ash. Magnetic separation refers to the separation of magnetically attached material from non-magnetic material by magnetic force.

[0007] The waste incineration ash processing system of this invention comprises a roll screen for processing the main ash from the waste incinerator, a magnetic separator that separately processes the components below the screen and above the screen that have fallen below the roll screen using magnetic force to separate the magnetically attached materials, and a sieve that separates the components below the screen and above the screen, after the magnetically attached materials have been separated, into non-magnetic foreign matter and ash, thereby separating the waste incineration ash into magnetically attached materials, non-magnetic foreign matter and ash.

[0008] A roller screen is a device equipped with a rotating roller that allows small objects to fall through the roller and its opening, while larger objects are carried over the opening. Since roller screens do not apply vibration, wire-like foreign objects are less likely to stand up due to vibration and fall vertically through the opening; instead, wire-like foreign objects are transported over the opening. In a roller screen, wire-like foreign objects and other foreign objects are mainly sorted by their longest diameter and become the components on the screen. Foreign objects with a small longest diameter, such as screws, gravel, and ceramic fragments, fall through the roller screen's opening along with the ash and become the components below the screen.

[0009] By treating the components on the screen with magnetic force, wire-like foreign objects are separated by magnetic force. By treating the components below the screen separately with magnetic force from the components on the screen, small metal screws and other objects in the ash are separated from the ash. The components on and below the screen, after removing the magnetically attached materials, are sieved to separate non-magnetic foreign objects.

[0010] In this way, wire-like foreign matter and other materials are removed from the bottom ash, as well as other magnetic and non-magnetic foreign matter. Since foreign matter can be sufficiently removed from the bottom ash, the bottom ash after foreign matter separation becomes suitable for cement raw materials, etc. Wire-like foreign matter and other materials can also be recovered from the bottom ash.

[0011] Preferably, a crushing step in which the components on the screen are crushed by an impact crusher is performed between the roll screen step and the first magnetic separation step. Crushing makes it easier for ash that has entered the inside of large foreign objects such as empty cans to fall out, and some of the ash attached to foreign objects such as wires also peels off and falls off. When the ash is removed, the foreign objects become smaller and lighter. Because the ash is removed and the objects become lighter, both foreign objects such as wires and large foreign objects become easier to separate by magnetic force.

[0012] Preferably, if the amount of foreign matter in the main ash is large, the roll screen step is performed, and if the amount of foreign matter in the main ash is small, the roll screen step is omitted, and a second magnetic separation step is performed in which the main ash is treated by magnetism to separate the magnetically attached materials. Since the roll screen step is omitted for main ash with little foreign matter, the processing of incinerated waste ash is simplified. The amount of foreign matter may be determined each time incinerated ash is received, or it may be determined in advance for each source of incinerated ash. The amount of foreign matter can be determined, for example, by passing the incinerated ash through a sieve with the same mesh size as the sieve used in the sieving step, and for example, if the weight ratio of the sieved components to the incinerated ash is 10% or more, it is considered that there is a lot of foreign matter.

[0013] Preferably, in the magnetic separation step, the components below the screen and the components above the screen are processed by separate magnetic separation devices. That is, small magnetic deposits in the components below the screen and large magnetic deposits in the components above the screen are separated by magnetic separation. The components above the screen have a lower ash content than the components below the screen, so it is easier to separate them by magnetic separation if they are not mixed together. Also, the small magnetic deposits in the components below the screen do not have a large amount of ash attached to them. At least they are not thickly coated with ash. For this reason, they can be easily separated by magnetic force.

[0014] Preferably, the process further includes a wet step in which water is added to at least a portion of the ash sieved in the sieving step, and a washing step in which magnetic and non-magnetic foreign materials are placed in separate water-permeable baskets and washed with water. At least a portion of the wastewater generated in the washing step is used in the wet step, for example, containing ash. By using water-permeable baskets, washing can be easily performed. Furthermore, the wastewater generated in the washing step can be used in the wet step and reused within the treatment system. [Brief explanation of the drawing]

[0015] [Figure 1] A diagram illustrating the outline of the first embodiment. [Figure 2] Plan view of the main part of the roller screen used in the first embodiment. [Figure 3] Vertical cross-sectional view of the roll in the roll screen used in the first embodiment. [Figure 4] Diagram showing an overview of the second embodiment. [Figure 5] Schematic cross-sectional view of the mesh basket and water tank used in the second embodiment. [Figure 6] A diagram illustrating the overview of the third embodiment. [Figure 7] A diagram illustrating the fourth embodiment. [Modes for carrying out the invention]

[0016] Examples for carrying out the present invention are shown below. The scope of this invention should be determined based on the claims, taking into consideration the description in the specification and the well-known art, and in accordance with the understanding of those skilled in the art. [Examples]

[0017] Example 1 Figures 1 to 7 show examples of a method and a system for treating incineration ash of garbage, and Figures 1 to 3 show a first embodiment. As shown in Figure 1, the receiving hopper 1 receives the main ash from the garbage 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.

[0018] The roll screen 2 is shown in Figures 2 and 3. The roll screen 2 includes a plurality of rolls 20, and a set of a small-diameter flange 21 and a large-diameter flange 22 projects radially from the roll shaft 24 of each roll 20. These flanges 21 and 22 may be industrially referred to as disks. And between 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. The ash and small foreign matters in the main ash fall from the opening 25, and the large foreign matters are conveyed without passing through the opening 25.

[0019] As shown in Figure 3, the flanges 21 and 22 are shaped such that the central part of the side of a polygon from a triangle to a pentagon bulges outward. With such flanges 21 and 22, it is difficult for foreign matters 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 referred to as components under the screen, and the components that have not fallen are referred to as components on the screen.

[0020] The adjacent openings 25, 25 are separated by flanges 21, 22, and wire-like foreign matter cannot pass through the gap between flanges 21, 22. For wire-like foreign matter to pass through opening 25, it would need to be raised vertically by vibration, but the roll 20 does not apply vibration to the main ash. Therefore, the wire-like foreign matter does not pass through opening 25 and is discharged as part of the screen component.

[0021] The number of rolls 20 is arbitrary, and the flanges 21 and 22 do not have to be polygonal but can be circular. Also, instead of a combination of large and small diameters, flanges of the same diameter may be arranged facing each other or alternately between adjacent rolls. However, in the roll screen 2 of Figures 2 and 3, it is difficult for wire-like foreign matter to pass between adjacent openings 25, 25, so wire-like foreign matter is less likely to be mixed into the components below the screen.

[0022] The magnetic material is separated by a magnetic separator from the component below the screen and the component above the screen, which have fallen through the opening 25 of the roll screen 2. Since the size of the magnetic material (mainly metal) differs between the component below the screen and the component above the screen, it is preferable to process them using different magnetic separators 4 and 5. The magnetic separators 4 and 5 may be electromagnetic, or they may use a magnetic pulley with a permanent magnet attached to the end of a belt conveyor to change the falling position of the magnetic material and other materials.

[0023] The ash and solid foreign matter that have passed through magnetic separators 4 and 5 are passed through sieve 6 to separate the solid foreign matter from the ash. Sieve 6 is, for example, a vibrating sieve, with a preferred mesh size of 8 mm to 25 mm, but the type of sieve and the range of mesh size are arbitrary. The ash that has passed through sieve 6 is stored in a silo 7 or the like, a portion is shipped as unwashed ash, and the remainder is subjected to wet crushing and washing to desalinate before being shipped. In addition, the magnetically attached materials from magnetic separators 4 and 5 are recovered as magnetically attached foreign matter, and the components on the sieve 6 are recovered as non-magnetic foreign matter. In this way, wire-like foreign matter and the like are prevented from being mixed into the ash that passes through sieve 6 and is shipped.

[0024] Example 2 Figures 4 and 5 show a second embodiment, which is the same as the embodiments in Figures 1 to 3 except for the points specifically noted. In the second embodiment, the screen components of the roll screen 2 are crushed by an impact crusher 3. The impact crusher 3 works by, for example, attaching multiple hammers to a rotating shaft and applying impact to the material to be processed by rotating the shaft. In the impact crusher 3, the material to be processed is sandwiched between a fixed gate and rotating hammers, or between a hammer on one rotating shaft and another rotating shaft, and impact is applied. Such impact crushers have been put into practical use as crushers or shredders. Crushers that use a toggle mechanism to sandwich the material to be processed between movable jaws and a fixed plate and crush it by gradually increasing the pressure were unsuitable for separating ash from foreign matter.

[0025] A large amount of ash adheres to the foreign matter on the screen. If the ash is not removed from the foreign matter, the ash recovery rate will decrease, and the magnetically attached material may not be separated by the subsequent magnetic separator due to the attached ash. Therefore, the impact crusher 3 is used to crush the components on the screen (metallic and nonmetallic foreign matter) and remove the ash attached to the foreign matter. When impact is applied, the ash attached to the foreign matter peels off. Ash may have entered the inside of containers such as empty cans and bottles, but crushing the containers separates the ash from the containers. In addition, some of the ash attached to the foreign matter peels off, making the foreign matter smaller and lighter. In addition, clumps of ash are also crushed, separating the ash from the foreign matter. As a result, magnetically attached foreign matter can be reliably separated by the next magnetic separator 5, and the ash recovery rate is also improved. Note that if the material does not pass through the impact crusher 3, magnetically attached foreign matter may not be separated by the magnetic separator 5.

[0026] The magnetically attached materials from the magnetic separators 4 and 5 are collected in a mesh basket 8 in the water tank 10 and washed with water. Similarly, the foreign materials remaining on the sieve 6 are collected in a mesh basket 9 in the water tank 11 and washed with water. The mesh baskets 8 and 9 and the water tanks 10 and 11 are schematically shown in Figure 4. By pouring water on the mesh baskets 8 and 9, or by vibrating the mesh baskets 8 and 9 in the water tanks 10 and 11 using a device not shown, ash attached to the magnetically attached materials (magnetic materials such as metals) and non-magnetic foreign materials can be removed. Removing the ash makes it easier to reuse the magnetically attached materials and non-magnetic foreign materials. The mesh baskets 8 and 9 only need to be permeable to water and not allow foreign materials to pass through; other types of baskets besides mesh baskets are also acceptable.

[0027] The ash, from which foreign matter has been removed and stored in silo 7, is transported to, for example, a cement factory to be used as part of the raw materials for cement clinker. Cement clinker has an upper limit on chlorine concentration. Therefore, a portion of the ash from which foreign matter has been removed is crushed in a wet crusher 13 and immersed in water in a desalination tank 14 to dissolve the chlorine. Then, the ash and water are separated by a solid-liquid separation device 15 such as a filter press. In this way, the average salinity of the treated ash is reduced to within an acceptable range. The wastewater separated in the solid-liquid separation device 15 is treated in a wastewater treatment device 16, and a portion of the wastewater is discharged after it has been made to meet environmental standards. When fly ash generated at a waste incineration plant is also treated, dioxins in the fly ash are removed by a dioxin removal device 12. The treated fly ash is then processed in a desalination tank 14.

[0028] The washing water used in tanks 10 and 11 to separate foreign matter from ash contains ash. Even if the wastewater from tanks 10 and 11 is used in the wet grinder 13 or desalination tank 14, for example, while it still contains ash, it will not contaminate the material being processed or the surrounding equipment. Therefore, the wastewater from tanks 10 and 11 is reused in the wet step (wet grinding or desalination) within the processing system. If the ash content in the wastewater is high, the wastewater may be treated in the solid-liquid separator 15. Alternatively, the ash may be allowed to settle from the wastewater, the supernatant may be used in the wet step, and the settled material may be treated in the solid-liquid separator 15. Furthermore, the wastewater can be used in the wet step without any treatment to separate the ash from the wastewater.

[0029] Example 3 Figure 6 shows a third embodiment, which is the same as the embodiments in Figures 1 to 3 except for the points specifically noted. In the third embodiment, if the amount of foreign matter in the bottom ash is large, it is processed with a roll screen and the magnetically attached material is separated by magnetic separators 4 and 5. If the amount of foreign matter in the bottom ash is small, the processing with the roll screen is omitted, and the bottom ash is processed by magnetic separator 4 via a receiving hopper. The amount of foreign matter may be determined each time incinerated ash is received, or it may be determined in advance for each source of incinerated ash. The amount of foreign matter can be determined, for example, by passing the incinerated ash through a sieve with the same mesh size as the sieve used in the sieving step, and for example, if the weight ratio of the sieved components to the incinerated ash is 10% or more, it is considered that there is a lot of foreign matter. The sieve 6 used in the sieving step has a mesh size of 8 mm to 25 mm, for example, so a sieve with a mesh size of 8 mm to 25 mm can also be used to determine the amount of foreign matter. In the third embodiment, the main ash, which contains few foreign materials, is not processed by the roll screen 2 and magnetic separator 5, thus simplifying the processing of waste incineration ash.

[0030] Example 4 Figure 7 shows the fourth embodiment, which is the same as the second embodiment in Figures 4 and 5, except for the points specifically noted. In the fourth embodiment as well, the bottom ash, which contains little foreign matter, is not processed by the roll screen 2, crusher 3, and magnetic separator 5, thus simplifying the processing of waste incineration ash compared to the second embodiment. [Explanation of symbols]

[0031] 1. Receiving hopper 2 Roller blinds 3. Impact shredder 4,5 Magnetic separator 6 sieve 7 silos 8,9 Net basket 10, 11 Aquariums 12. Dioxin removal device 13. Wet grinder 14 Desalination tank 15 Solid-liquid separator 16. Wastewater treatment equipment 20 rolls 21,22 Flange 24 Roll axis 25 Opening

Claims

1. a roll screen step in which bottom ash from a waste incinerator is treated with a roll screen to separate it into an under-screen component that falls below the roll screen and an over-screen component that passes through the upper side of the roll screen; a first magnetic separation step in which the under-screen component and the over-screen component are separately treated with magnetic force to separate magnetically attached materials; After separating the magnetic materials, the under-screen components and the over-screen components are separated into non-magnetic foreign matter and ash in a sieving step. A method for treating garbage incineration ash, which separates the garbage incineration ash into magnetic materials, non-magnetic foreign materials, and ash.

2. 2. A method for treating refuse incineration ash according to claim 1, wherein a crushing step of crushing the components on the screen with an impact crusher is carried out between the roll screen step and the first magnetic separation step.

3. If the amount of foreign matter in the bottom ash is large, perform the roll screen step; 3. A method for treating refuse incineration ash according to claim 1 or 2, characterized in that if the amount of foreign matter in the bottom ash is small, the roll screen step is omitted and a second magnetic separation step is carried out in which the bottom ash is treated by magnetic force to separate magnetically attached matter.

4. 4. The method for treating refuse incineration ash according to claim 1, wherein in the first magnetic separation step, the under-screen component and the over-screen component are treated by separate magnetic separation devices.

5. a wet step in which at least a portion of the ash sieved in the sieving step is treated with water; a water washing step of placing the magnetized objects and the foreign objects in separate water-permeable baskets and washing them with water; The method for treating refuse incineration ash according to any one of claims 1 to 4, characterized in that at least a part of the wastewater generated in the water washing step is used in the wet step.

6. Roll screens for processing bottom ash from waste incinerators, a magnetic separator that separates the under-screen components that have fallen to the bottom of the roll screen and the above-screen components using magnetic force to separate the magnetically attached materials; and a sieve for separating the under-screen component and the over-screen component after separating the magnetic material into non-magnetic foreign matter and ash; A garbage incineration ash treatment system configured to separate garbage incineration ash into magnetic materials, non-magnetic foreign materials, and ash.

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