Water washing method of main ash, method for producing cement raw material, and main ash washing apparatus

Abstract

To provide a water washing method of main ash capable of further reducing a drainage amount while sufficiently removing chlorine, a method for producing a cement raw material including the water washing method of main ash in a process, and a main ash washing device used for the water washing method of main ash.SOLUTION: A water washing method of main ash according to the present invention is a method for washing main ash with water using a washing tank, and includes the following steps (1) to (3). Step (1) of immersing the main ash in water in a washing tank to wash the main ash with water to obtain a water-washed cake. Step (2) of taking out the water-washed cake obtained in the step (1) from water, and then sprinkling water on the water-washed cake at an upper part in a washing tank. Step (3) of discharging the water in the washing tank according to the amount of the water flowing into the washing tank while the water sprayed in the step (2) flows into the washing tank.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for washing bottom ash with water, a method for producing a cement raw material, and a bottom ash washing device. [Background technology]

[0002] Incineration ash generated in incineration facilities such as waste incinerators includes bottom ash recovered from the bottom of the incinerator and fly ash contained in the incineration exhaust gas. In recent years, such incineration ash has been effectively utilized as a cement raw material. However, since incineration ash containing bottom ash contains chlorine, if it is used as a cement raw material as is, the resulting cement will contain a large amount of chlorine, which will have a negative impact on the quality of the cement. In particular, bottom ash is generally used as a cement raw material after being washed with water to remove chlorine.

[0003] Conventionally, a method for washing incineration ash such as bottom ash with water involves providing a two-stage washing tank (for example, Patent Documents 1 and 2). Specifically, the bottom ash is washed with water in a first-stage washing tank to remove chlorine, and then the bottom ash is further washed with water in a second-stage washing tank to replace and remove the washing water containing chlorine remaining in the bottom ash. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-200794 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-82487 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-described water washing method, a large amount of water is used, particularly in the second-stage washing tank, and therefore a large amount of wastewater treatment is required. Although the second-stage washing water can be reused, it is desired to further reduce the amount of wastewater from the viewpoints of load on the treatment facility and environmental conservation.

[0006] Therefore, an object of the present invention is to provide a method for washing bottom ash that can sufficiently remove chlorine while further reducing the amount of wastewater, a method for producing a cement raw material using the method for washing bottom ash, and a bottom ash washing device used in the method for washing bottom ash. [Means for solving the problem]

[0007] The method for washing bottom ash according to the present invention is a method for washing bottom ash with water using a washing tank, and includes the following steps (1) to (3). Step (1): The bottom ash is immersed in water in a washing tank and washed to obtain a washed cake. Step (2): A step of removing the washed cake obtained in step (1) from the water and then spraying water onto the washed cake in the upper part of the washing tank. Step (3): A step of draining the water from the cleaning tank according to the amount of water that has flowed into the cleaning tank after the water spraying in step (2).

[0008] According to this configuration of the bottom ash washing method, in step (2), after removing the washed cake obtained in step (1) from the water, water is sprayed on the washed cake at an upper part of the washing tank, thereby efficiently removing chlorine from the washed cake with a smaller amount of water than in the conventional method of immersing the washed cake in water even in the second step. Furthermore, in step (3), the water sprayed in step (2) flows into the washing tank, and the water in the washing tank is discharged in accordance with the amount of water that has flowed into the washing tank, thereby reducing the amount of wastewater compared to conventional methods. Therefore, the bottom ash washing method according to the present invention can further reduce the amount of wastewater while sufficiently removing chlorine.

[0009] In the method for washing bottom ash with water according to the present invention, the amount of water sprayed in the step (2) may be 20% by mass or more and 150% by mass or less with respect to the bottom ash.

[0010] In the method for washing bottom ash with water, by setting the amount of water sprayed within the above range, chlorine can be efficiently removed from the washed cake with a small amount of water, and the amount of wastewater can be further reduced.

[0011] In the method for washing bottom ash with water according to the present invention, the water in the washing tank may contain sulfuric acid.

[0012] According to the above-described method for washing bottom ash with water, chlorine can be sufficiently removed with a smaller amount of water.

[0013] In the method for washing bottom ashes with water according to the present invention, in the step (3), water may be discharged from the washing tank in an amount substantially equal to the amount of water that has flowed into the washing tank after the water spraying.

[0014] According to the above-described method for washing bottom ash with water, the amount of water discharged from the washing tank can be easily controlled.

[0015] The method for producing a cement raw material according to the present invention includes a step of dehydrating the washed cake obtained by the water-washing method for bottom ash described above, The solid content obtained in the above step is used as a cement raw material.

[0016] According to the above-described method for producing a cement raw material, chlorine in the bottom ash can be sufficiently removed with a smaller amount of water, and the solid content thus obtained can be effectively used as a cement raw material.

[0017] The bottom ash washing device according to the present invention is a bottom ash washing device used in the above-mentioned bottom ash washing method, The method comprises a washing tank for washing bottom ash and a conveying means for conveying the bottom ash in the washing tank, The cleaning tank comprises: an inlet provided at an upper portion of the washing tank for introducing bottom ash; a water storage section for storing water for washing the bottom ash introduced through the introduction port; a discharge port provided in an upper portion of the washing tank for discharging the washed cake; a sprinkling unit that is provided in an upper portion of the washing tank and upstream of the discharge port in the conveying direction, the sprinkling unit being configured to sprinkle water on the washed cake that has been subjected to the water-washing treatment and to allow the sprinkled water to flow into the water storage unit; and a drainage section for draining the water from the water storage section.

[0018] According to this configuration, the bottom ash washing device can thoroughly remove chlorine from the bottom ash by washing the bottom ash with water in the water storage section and then further washing the bottom ash with water in the water spray section. Furthermore, by configuring the water spray section so that the water after spraying flows into the water storage section, the amount of wastewater can be further reduced. As a result, the bottom ash washing device of the present invention can thoroughly remove chlorine from the bottom ash while further reducing the amount of wastewater.

[0019] The bottom ash washing apparatus according to the present invention may further include a chlorine concentration monitoring unit that monitors the concentration of chlorine contained in the water stored in the water storage unit.

[0020] With this configuration, the bottom ash washing device can easily manage the concentration of chlorine contained in the water stored in the water storage section so that it does not increase too much. [Effects of the Invention]

[0021] According to the present invention, there are provided a method for washing bottom ash that can reduce the amount of wastewater while sufficiently removing chlorine, a method for producing a cement raw material using the method for washing bottom ash, and a bottom ash washing apparatus used in the method for washing bottom ash. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram illustrating a bottom ash washing device 1 according to this embodiment. [Figure 2]FIG. 2 is a graph obtained by plotting values ​​in Test 1 of the Example, with the amount of water used for irrigation on the horizontal axis and the chlorine removal rate on the vertical axis. [Figure 3] FIG. 3 is a graph obtained by plotting values ​​in Test 2 of the example, with the amount of sprinkling water containing sulfuric acid on the horizontal axis and the chlorine removal rate on the vertical axis. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0024] (How to wash bottom ash) The method for washing bottom ash according to this embodiment is a method for washing bottom ash using a washing tank, and includes the following steps (1) to (3). Step (1): The bottom ash is immersed in water in a washing tank and washed to obtain a washed cake. Step (2): A step of removing the washed cake obtained in step (1) from the water and then spraying water onto the washed cake in the upper part of the washing tank. Step (3): A step of draining the water from the cleaning tank according to the amount of water that has flowed into the cleaning tank after the water spraying in step (2).

[0025] As used herein, "bottom ash" refers to granular ash generated from incineration facilities such as waste incinerators that is not contained in the exhaust gas emitted from the incineration facilities. The particle size of the bottom ash is not particularly limited and may be, for example, 0.1 μm to 100 mm or 1 μm to 50 mm. The particle size is determined by separating particles that do not pass through a 1 mm sieve from those that do, using the method specified in JIS Z 8815, General Rules for Sieving Test Methods. The particle size of the non-passing particles is measured using the method specified in JIS Z 8815, General Rules for Sieving Test Methods, and the particle size of the passing particles is measured using the method specified in JIS Z 8825, Particle Size Analysis - Laser Diffraction and Scattering Methods. The chlorine content of the bottom ash is not particularly limited and varies greatly depending on the facility and the material being treated, but may be, for example, 0.1% to 5% by mass or 0.5% to 2% by mass. The chlorine content of bottom ash can be measured in accordance with JIS R 5202 Chemical Analysis Method for Cement (18 Chlorine 18.1 Potentiometric Titration Method).

[0026] The method for washing bottom ash according to this embodiment may be a method for washing only the bottom ash, or a method for washing ashes other than the bottom ash, such as fly ash, biomass combustion ash, and paper sludge ash, together with the bottom ash. When ashes other than the bottom ash are washed together with the bottom ash, the content of the bottom ash may be, for example, 10% by mass or more and 90% by mass or less with respect to the total amount of ash.

[0027] <Process (1)> In step (1), the bottom ash is immersed in water in a washing tank and washed to obtain a washed cake.

[0028] The method for soaking the bottom ash is not particularly limited, and examples thereof include a method in which the bottom ash is directly poured into the water in the washing tank and left to soak for a predetermined time, a method in which the bottom ash is soaked in the water in the washing tank while being moved by a conveying means (described later), etc. Among these, the method of soaking the bottom ash is preferably a method in which the bottom ash is soaked in the water in the washing tank while being moved by a conveying means, from the viewpoint of further shortening the working time while sufficiently removing chlorine.

[0029] The amount of water in the washing tank is not particularly limited as long as it is an amount that allows the bottom ash to be immersed, and may be, for example, 2 to 20 times or 4 to 20 times the mass of the bottom ash.

[0030] The time for soaking the bottom ash in water is preferably 30 minutes or more, more preferably 1 hour or more, from the viewpoint of sufficiently removing chlorine, and is preferably 2 hours or less, more preferably 1 hour or less, from the viewpoint of further shortening the working time while sufficiently removing chlorine.

[0031] The water used in step (1) preferably contains sulfuric acid from the viewpoint of sufficiently removing chlorine with a smaller amount of water. Note that the sulfuric acid may be, for example, industrially produced sulfuric acid or sulfuric acid generated when calcium carbonate is produced by a conversion reaction of gypsum.

[0032] When the water contains sulfuric acid, the amount of sulfuric acid added to the water is preferably 0.5% by mass or more and 20% by mass or less, more preferably 0.8% by mass or more and 15% by mass or less, calculated as concentrated sulfuric acid, relative to 100 g of bottom ash. The concentration of sulfuric acid is preferably 0.06% by mass or more and 90% by mass or less, more preferably 35% by mass or more and 80% by mass or less. The concentration of sulfuric acid is determined in accordance with JIS K 0102 Industrial Wastewater Testing Method (41. Sulfate ion (SO4 2- )) can be measured based on.

[0033] <Process (2)> In step (2), the washed cake obtained in step (1) is taken out of the water, and then water is sprayed onto the washed cake in an upper part of the washing tank. The upper part of the washing tank is not particularly limited as long as it is a position where water after spraying flows into the washing tank in step (3) described below, that is, it may be a position vertically above a plane including the surface of the water stored in a water storage section described below.

[0034] The method for removing the washed cake from the water is not particularly limited, and examples thereof include a method of removing the washed cake using a bucket or the like, and a method of removing the washed cake while moving it using a conveying means described below.

[0035] From the viewpoint of efficiently removing chlorine from the washed cake with a small amount of water, the amount of water used in the sprinkling is preferably 20% by mass or more and 150% by mass or less, and more preferably 40% by mass or more and 150% by mass or less, based on the bottom ash.

[0036] The time for spraying water onto the washed cake is preferably 1 minute or longer, more preferably 3 minutes or longer, from the viewpoint of sufficiently removing chlorine, and is preferably 10 minutes or shorter, more preferably 5 minutes or shorter, from the viewpoint of further shortening the working time while sufficiently removing chlorine.

[0037] When water containing sulfuric acid is used in step (1), the water used in step (2) is preferably sulfuric acid-free, which makes it possible to remove not only chlorine but also sulfuric acid from the washed cake obtained in step (1).

[0038] <Process (3)> In step (3), the water after sprinkling in step (2) flows into the cleaning tank, and the water in the cleaning tank is discharged in accordance with the amount of water that has flowed into the cleaning tank. Specifically, the water after sprinkling in step (2) flows into a water storage section in the cleaning tank, and the water in the water storage section in the cleaning tank is discharged in accordance with the amount of water that has flowed into the water storage section in the cleaning tank.

[0039] From the viewpoint of easily controlling the amount of water discharged from the cleaning tank, the amount of water discharged from the cleaning tank is preferably within a range of ±10% of the amount of water that flows into the cleaning tank after watering, and more preferably is approximately the same amount as the amount of water that flows into the cleaning tank after watering. Note that "approximately the same amount" means an amount that is within a range of ±5% of the amount of water that flows into the cleaning tank after watering.

[0040] The bottom ash washing method according to this embodiment includes the above steps (1) to (3). First, in step (2), the washed cake obtained in step (1) is removed from the water, and then water is sprayed onto the washed cake at an upper portion of a washing tank. This allows chlorine to be removed from the washed cake more efficiently with a smaller amount of water than in conventional methods of immersing a washed cake in water. Next, in step (3), the water sprayed in step (2) flows into the washing tank, and the water in the washing tank is discharged in accordance with the amount of water that has flowed into the washing tank. This keeps the chlorine concentration in the water in the washing tank substantially constant, thereby reducing the amount of wastewater while maintaining the chlorine removal rate from the washed cake. This allows for a further reduction in the amount of wastewater while sufficiently removing chlorine.

[0041] (Cement raw material manufacturing method) The method for producing a cement raw material according to this embodiment includes a step of dehydrating the washed cake obtained by the water-washing method for the bottom ash after the water spraying.

[0042] The method for dewatering the washed cake after water spraying is not particularly limited, and for example, a known dewatering machine such as a vibrating sieve, a filter press, a belt press, or a centrifuge can be used.

[0043] The solid content (dehydrated cake) obtained by the step of dehydrating the washed cake after water spraying is used as a cement raw material. The moisture content of the dehydrated cake is not particularly limited, and may be, for example, 10% to 50% or 10% to 30%.

[0044] The moisture content can be calculated from the following formula (1). Moisture content (%) = 100 × (mass of water in dehydrated cake) / (mass of dehydrated cake) (1)

[0045] The method for producing a cement raw material according to this embodiment includes a step of dehydrating the washed cake obtained by the above-described method for washing bottom ash after water spraying. By using the solid fraction obtained in this step as a cement raw material, chlorine in the bottom ash can be sufficiently removed with a smaller amount of water, and the solid fraction obtained in this way can be effectively used as a cement raw material.

[0046] (Bottom ash cleaning device) Hereinafter, a bottom ash washing device 1 according to an embodiment of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference numerals, and the description thereof will not be repeated.

[0047] Fig. 1 is a schematic diagram illustrating a bottom ash washing apparatus 1 according to this embodiment. As shown in Fig. 1, the bottom ash washing apparatus 1 according to this embodiment includes a washing tank 2 for washing bottom ash S, and a conveying means 3 for conveying the bottom ash S within the washing tank 2. The bottom ash washing apparatus 1 according to this embodiment preferably further includes a chlorine concentration monitoring unit (not shown).

[0048] [Cleaning tank] The washing tank 2 includes an inlet 21 for introducing bottom ash, a water storage section 22 for storing water W for washing the bottom ash S introduced from the inlet 21, a discharge outlet 23 for discharging the washed cake S', a water sprinkling section 24 configured to sprinkle water on the washed cake S' and allow the sprinkled water to flow into the water storage section 22, and a drainage section 25 for draining the water W from the water storage section 22.

[0049] The inlet 21 is provided at an upper part in the cleaning tank 2. More specifically, the inlet 21 is provided at a position vertically above a plane including the water surface of the water W stored in the water storage section 22.

[0050] The inlet 21 may further include a hopper.

[0051] The water storage section 22 is provided in the lower part of the cleaning tank 2, and is provided downstream of the input port 21 in the conveying direction A.

[0052] The discharge outlet 23 is provided in the upper part of the cleaning tank 2 and is provided downstream of the water storage section 22 in the conveying direction A.

[0053] The water spray unit 24 is provided in the upper part of the cleaning tank 2 and on the upstream side of the discharge port 23 in the conveying direction A.

[0054] The sprinkler unit 24 is a spray device. Note that the sprinkler unit 24 is not limited to a spray device, and may be, for example, a shower, a sprinkler, or the like.

[0055] 1, the drainage section 25 is provided at the bottom inside the cleaning tank 2. Specifically, the drainage section 25 is provided at the side of the water storage section 22. Note that the drainage section 25 may be provided at another position, for example, at the bottom of the water storage section 22.

[0056] The drainage section 25 may be provided with a drainage adjustment section such as a valve so that the amount of drainage can be adjusted.

[0057] [Transportation means] The conveying means 3 is arranged so as to be able to convey the bottom ash S within the washing tank 2. Specifically, the conveying means 3 are arranged in succession so that the bottom ash S can travel from the inlet 21 through the water storage section 22 and the water spray section 24 to the outlet 23. The conveying means 3 is a belt conveyor equipped with a belt. The belt has a plurality of protrusions 31 protruding outward. This allows the bottom ash S to move even below the belt conveyor. Note that the conveying means 3 is not limited to a belt conveyor, and may be, for example, a screw conveyor, a classifier, or the like.

[0058] The bottom ash S charged through the charging port 21 falls onto the upper side of the conveying means 3. The conveying means 3 drops the charged bottom ash S onto the lower side of the conveying means 3 and moves it to the water storage section 22 through the lower side of the conveying means 3. The conveying means 3 then transfers the bottom ash S within the water storage section 22 through the lower side of the conveying means 3 to obtain a washed cake S'. Thereafter, the conveying means 3 removes the washed cake S' from the water and transfers it through the lower side of the conveying means 3 to below the water spray section 24 and to the discharge port 23. Note that the conveying means 3 may transfer the charged bottom ash S while moving it above the conveying means 3 between the charging port 21 and the discharge port 23.

[0059] The conveying means 3 is inclined so as to gradually decline toward the downstream side in the conveying direction on the upstream side of the water storage section 22. In addition, the conveying means 3 is inclined so as to gradually decline toward the downstream side in the conveying direction on the downstream side of the water storage section 22. This allows the bottom ash washed in the water storage section 22 to be extracted from the water as a washed cake.

[0060] [Chlorine concentration monitoring unit] In one embodiment, the bottom ash washing device 1 according to the present embodiment preferably further includes a chlorine concentration monitoring unit that monitors the concentration of chlorine contained in the water stored in the water storage unit 22. The chlorine concentration monitoring unit may be disposed on the upstream side of the water storage unit 22 in the conveying direction A, on the downstream side of the water storage unit 22 in the conveying direction A, or around the center of the water storage unit 22.

[0061] The chlorine concentration monitoring unit is configured to be able to monitor the concentration of chlorine contained in the water stored in the water storage unit 22, specifically the concentration of chloride ions and / or free residual chlorine. Specifically, the chlorine concentration monitoring unit has an ion meter, an absorptiometer, etc.

[0062] The bottom ash washing device 1 according to this embodiment is used in the bottom ash washing method according to this embodiment.

[0063] Specifically, the bottom ash washing device 1 according to this embodiment performs a step (1) of washing the bottom ash S in the water storage section 22 while moving the bottom ash S with the transport means 3 to obtain a washed cake S'.

[0064] In the bottom ash washing apparatus 1 according to this embodiment, the washed cake S' is taken out of the water by the conveying means 3, and then water is sprayed onto the washed cake S' in the water spraying section 24, thereby carrying out the step (2).

[0065] The bottom ash washing device 1 according to this embodiment performs step (3) by allowing the water sprayed in the spray section 24 to flow into the water storage section 22 and discharging the water in the drain section 25 according to the amount of water that has flowed in.

[0066] The bottom ash washing device 1 according to this embodiment may be provided with a washed cake dewatering section (not shown) downstream of the discharge outlet 23 in the conveying direction A. This allows the washed cake discharged from the discharge outlet 23 to be dewatered, thereby obtaining a dewatered cake that can be used as a cement raw material.

[0067] The washed cake dewatering section is the same as the dewatering machine used in the method for producing a cement raw material according to the above embodiment.

[0068] The bottom ash washing apparatus 1 according to this embodiment is equipped with the washing tank 2 and the conveying means 3, and can thoroughly remove chlorine from the bottom ash S by washing the bottom ash S with water in the water storage section 22 and then further washing the bottom ash S with water in the water spray section 24. Furthermore, the water spray section 24 is configured so that the water after spraying flows into the water storage section 22, thereby further reducing the amount of wastewater. As a result, the bottom ash washing apparatus 1 according to the present invention can thoroughly remove chlorine from the bottom ash while further reducing the amount of wastewater.

[0069] The bottom ash washing method, cement raw material manufacturing method, and bottom ash washing apparatus according to the present invention are not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention.

[0070] The present invention includes the following aspects. [1] A method for washing bottom ash with water using a washing tank, comprising the following steps (1) to (3): Step (1): The bottom ash is immersed in water in a washing tank and washed to obtain a washed cake. Step (2): A step of removing the washed cake obtained in step (1) from the water and then spraying water onto the washed cake in the upper part of the washing tank. Step (3): A step of draining the water from the cleaning tank according to the amount of water that has flowed into the cleaning tank after the water spraying in step (2). [2] The method for washing bottom ash according to [1], wherein the amount of water sprayed in step (2) is 20% by mass or more and 150% by mass or less relative to the bottom ash. [3] The method for washing bottom ash with water according to [1] or [2], wherein the water in the washing tank contains sulfuric acid. [4] A method for washing bottom ash with water according to any one of [1] to [3], wherein in step (3), approximately the same amount of water as that flowing into the washing tank after the water spraying is discharged from the washing tank. [5] A method for washing bottom ash by water washing according to any one of [1] to [4], comprising a step of dehydrating the washed cake obtained after water spraying, The solid content obtained in the above step is used as a cement raw material. [6] A bottom ash washing device used in the bottom ash washing method according to any one of [1] to [4], The method comprises a washing tank for washing bottom ash and a conveying means for conveying the bottom ash in the washing tank, The cleaning tank comprises: an inlet provided at an upper portion of the washing tank for introducing bottom ash; a water storage section for storing water for washing the bottom ash introduced through the introduction port; a discharge port provided in an upper portion of the washing tank for discharging the washed cake; a sprinkling unit that is provided in an upper portion of the washing tank and upstream of the discharge port in the conveying direction, the sprinkling unit being configured to sprinkle water on the washed cake that has been subjected to the water-washing treatment and to allow the sprinkled water to flow into the water storage unit; A bottom ash washing device comprising: a drainage section for draining water from the water storage section. [7] The bottom ash washing device described in [6] further comprises a chlorine concentration monitoring unit that monitors the concentration of chlorine contained in the water stored in the water storage unit. [Example]

[0071] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0072] (Materials used) Bottom ash: Collected from a general waste incineration plant. The chlorine content of the bottom ash was 0.75% by mass-wet. The chlorine content of the bottom ash was measured in accordance with JIS R 5202 Chemical Analysis Method for Cement (18 Chlorine 18.1 Potentiometric Titration Method). Impregnation water: Chlorine was added to pure water by adding sodium chloride to achieve the specified concentration shown in Table 1. The chlorine content in the impregnation water was measured based on JIS R 5202 Methods for Chemical Analysis of Cement (18 Chlorine 18.1 Potentiometric titration method). Water for irrigation: Pure water was used as is.

[0073] [Test 1] (Examples 1-1 to 1-6) A washed cake was obtained by impregnating 20 g of bottom ash wet in 40 g of impregnation water containing 4000 ppm Cl for 30 minutes. Using a wash bottle, the obtained washed cake was sprayed with water at the ratio of water to bottom ash shown in Table 1 for 5 minutes. The washed cake after spraying was dewatered, and the chlorine content of the resulting dehydrated cake was measured using the same method as above. The chlorine removal rate was calculated from the chlorine content in the dehydrated cake and the chlorine content in the bottom ash using the following formula (I). The results are shown in Table 1. Note that when the chlorine removal rate is a negative value, this means that the chlorine content in the dehydrated cake exceeds the chlorine content in the bottom ash. Chlorine removal rate (%) = (chlorine content in dehydrated cake) / (chlorine content in bottom ash) × 100 (I)

[0074] (Examples 1-7 to 1-12) Except for using impregnation water containing 8000 ppm-Cl of chlorine, the chlorine removal rate was determined in the same manner as in Examples 1 to 6. The results are shown in Table 1.

[0075] (Examples 1-13 to 1-18) The results are shown in Table 1.

[0076] (Examples 1-19 to 1-24) The chlorine removal rate was determined in the same manner as in Examples 1-1 to 1-6, except that the impregnation water containing 40,000 ppm of chlorine was used. The results are shown in Table 1.

[0077] (Comparative Example 1-1) The chlorine removal rate was determined by washing with water in the same manner as in Example 1-5, except that chlorine-free water was used as the impregnation water. The results are shown in Table 1.

[0078] (Comparative Example 1-2) The chlorine removal rate was determined by washing with water in the same manner as in Example 1-6, except that chlorine-free water was used as the impregnation water. The results are shown in Table 1.

[0079] (Comparative Examples 1-3) The chlorine removal rate was determined in the same manner as in Example 1-1, except that no water was sprayed. The results are shown in Table 1.

[0080] (Comparative Examples 1-4) The chlorine removal rate was determined in the same manner as in Example 1-7, except that no water was sprayed. The results are shown in Table 1.

[0081] (Comparative Examples 1-5) The chlorine removal rate was determined in the same manner as in Example 1-13, except that no water was sprayed. The results are shown in Table 1.

[0082] (Comparative Examples 1-6) The chlorine removal rate was determined in the same manner as in Example 1-19, except that no water was sprayed. The results are shown in Table 1.

[0083] [Table 1]

[0084] [Test 2] (Examples 2-1 to 2-24, Comparative Examples 2-1 to 2-6) Sulfuric acid 0.85% (SO4 2- Washing with water was carried out in the same manner as in Examples 1-1 to 1-24 and Comparative Examples 1-1 to 1-6, except that impregnation water containing sulfuric acid (equivalent to sulfuric acid) was used, and the chlorine removal rate was determined. The impregnation water containing sulfuric acid was obtained by mixing 0.345 g of concentrated sulfuric acid with the impregnation water. The results are shown in Table 2.

[0085] [Table 2]

[0086] As can be seen from Tables 1 and 2 and FIGS. 2 and 3, the method for washing bottom ash that satisfies all of the configurations of the present invention is capable of sufficiently removing chlorine while further reducing the amount of wastewater.

[0087] Furthermore, as can be seen from Table 2 and Figure 3, the water washing method for bottom ash that satisfies all of the configurations of the present invention can sufficiently remove chlorine with a smaller amount of water by including sulfuric acid in the water in the washing tank.

[0088] Furthermore, the dehydrated cake (solid content) obtained by the bottom ash washing method according to the present invention can be used as a cement raw material because chlorine can be sufficiently removed even with a smaller amount of water. [Explanation of symbols]

[0089] 1 Bottom ash cleaning device 2 Cleaning tank 21 Inlet 22 Water storage section 23 Outlet 24 Sprinkler section 25 Drainage section 3. Means of transportation 31 Protrusion S bottom ash S' Washed cake W Water storage section 22 A Conveying direction

Claims

1. A method for washing bottom ash with water using a washing tank, comprising the following steps (1) to (3). Step (1): A step of immersing the bottom ash in water in a washing tank to wash it and obtain a washed cake. Step (2): A step of removing the washed cake obtained in the step (1) from the water and then spraying water onto the washed cake in the upper part of the washing tank. Step (3): A step of discharging the water from the cleaning tank according to the amount of water that has flowed into the cleaning tank as the water from the spraying step (2) flows into the cleaning tank.

2. 2. The method for washing bottom ash according to claim 1, wherein the amount of water sprayed in step (2) is 20% by mass or more and 150% by mass or less relative to the bottom ash.

3. The method for washing bottom ash with water according to claim 1 , wherein the water in the washing tank contains sulfuric acid.

4. 2. The method for washing bottom ash with water according to claim 1, wherein in the step (3), the amount of water discharged from the washing tank is approximately the same as the amount of water that flowed into the washing tank after the watering.

5. The method for washing bottom ash according to any one of claims 1 to 4, further comprising a step of dehydrating the washed cake obtained after water spraying, The solid content obtained in the above step is used as a cement raw material.

6. A bottom ash washing device used in the bottom ash washing method according to any one of claims 1 to 4, The method comprises a washing tank for washing bottom ash and a conveying means for conveying the bottom ash in the washing tank, The cleaning tank comprises: an inlet provided at an upper portion of the washing tank for introducing bottom ash; a water storage section for storing water for washing the bottom ash introduced through the introduction port; a discharge port provided in an upper portion of the washing tank for discharging the washed cake; a sprinkling unit that is provided in an upper portion of the washing tank and upstream of the discharge port in the conveying direction, the sprinkling unit being configured to sprinkle water on the washed cake that has been subjected to the water-washing treatment and to allow the sprinkled water to flow into the water storage unit; A bottom ash washing device comprising: a drainage section for draining water from the water storage section.

7. The bottom ash washing device according to claim 6, further comprising a chlorine concentration monitoring unit that monitors the concentration of chlorine contained in the water stored in the water storage unit.

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