Method for producing low-chlorine fly ash, method for reducing the amount of chlorine in incineration fly ash, method for producing cement, and method for recycling incineration fly ash into cement resources

Abstract

To provide a method for producing low-chlorine fly ash that makes it possible to produce low-chlorine fly ash with a reduced chlorine level from incineration fly ash.SOLUTION: A method for producing low-chlorine fly ash is disclosed. The production method includes a first step for measuring Al2O3 and Cl levels in incineration fly ash and selecting the incineration fly ash with the Al2O3 level being 9 mass% or less, and a second step for washing the selected incineration fly ash with water or acidic water to remove soluble matter.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing low-chlorine fly ash, a method for reducing the chlorine content of incineration fly ash, a method for producing cement, and a method for recycling incineration fly ash into a cement resource. [Background technology]

[0002] Conventionally, methods have been known in which incineration fly ash is washed, the chlorine in the incineration fly ash is desalted, and the resulting dehydrated cake is used as a cement raw material. For example, Patent Documents 1 and 2 disclose methods in which water or water and acid are added to the incineration fly ash to suspend it, thereby dissolving the chlorine, and the resulting dehydrated cake is used as a cement raw material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-338312 [Patent Document 2] Japanese Patent Application Publication No. 10-202226 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the methods of Patent Documents 1 and 2 have a problem in that, depending on the type of incineration fly ash, chlorine in the incineration fly ash cannot be sufficiently removed.

[0005] Therefore, a main object of the present invention is to provide a method for producing low-chlorine fly ash, which is capable of producing low-chlorine fly ash having a reduced chlorine content from incineration fly ash. [Means for solving the problem]

[0006] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, it was found that the chlorine removal rate when incineration fly ash is washed varies depending on the amount of components in the incineration fly ash. Based on this finding, the present inventors found that by focusing on specific components, the amount of chlorine in incineration fly ash can be sufficiently reduced by washing the incineration fly ash with water or acidic water, and thus completed the present invention.

[0007] One aspect of the present invention relates to a method for producing low-chlorine fly ash from incineration fly ash, which produces low-chlorine fly ash with a reduced chlorine content (Cl content). The method includes a first step of measuring the Al2O3 and Cl content of incineration fly ash and selecting incineration fly ash with an Al2O3 content of 9% by mass or less, and a second step of washing the selected incineration fly ash with water or acidic water to remove soluble components. When the incineration fly ash is stirred and washed with acidic water in the second step, the pH of the slurry containing the incineration fly ash and acidic water may be 8 to 12. The inventors have found that selecting incineration fly ash with an Al2O3 content of 9% by mass or less and washing it with water or acidic water can sufficiently remove chlorine from the incineration fly ash. Therefore, this method makes it possible to produce low-chlorine fly ash with a reduced Cl content from incineration fly ash.

[0008] One embodiment of the first step may be a step of selecting incineration fly ash having an Al2O3 content of 9% by mass or less and a Cl content of 11% by mass or less. In this case, the second step may be a step of washing the selected incineration fly ash with water. The inventors have found that by selecting such incineration fly ash, chlorine in the incineration fly ash can be more thoroughly removed without using acidic water. By not using acidic water, it is possible to suppress the dissolution of calcium components, which are useful as a cement resource and which, if dissolved, cause scaling problems in equipment.

[0009] Another embodiment of the first step may be a step of further measuring the RO content (amount of alkali oxide) of the incineration fly ash and selecting incineration fly ash having an AlO content of 9% by mass or less, a Cl content of more than 11% by mass, and an RO / Cl molar ratio of more than 0.35. In this case, the second step may be a step of washing the selected incineration fly ash with water. The inventors have found that by selecting such incineration fly ash, chlorine in the incineration fly ash can be more thoroughly removed without using acidic water. By not using acidic water, it is possible to suppress the dissolution of calcium components, which are useful as a cement resource and which, if dissolved, can cause scaling problems in equipment.

[0010] In the second step, the number of washings may be two or more. In this case, it is preferable that the last washing is a penetration washing and the remaining washings are agitation washings.

[0011] The ignition loss of the incineration fly ash may be 5 to 40% by mass.

[0012] Another aspect of the present invention relates to a method for reducing the amount of Cl in incineration fly ash, which comprises a first step of measuring the amounts of Al2O3 and Cl in the incineration fly ash and selecting incineration fly ash having an Al2O3 amount of 9 mass% or less, and a second step of washing the selected incineration fly ash with water or acidic water to remove soluble matter.

[0013] Another aspect of the present invention relates to a method for producing cement, comprising the step of using the low-chlorine fly ash produced by the above-described method as a cement raw material.

[0014] Another aspect of the present invention relates to a method for recycling incineration fly ash into a cement resource, in which the low-chlorine fly ash produced by the above-mentioned production method is used as a cement raw material. [Effects of the Invention]

[0015] According to the present invention, there is provided a method for producing low-chlorine fly ash, which can produce low-chlorine fly ash with a reduced chlorine content from incineration fly ash. The present invention also provides a method for reducing the chlorine content of incineration fly ash. Furthermore, the present invention also provides a method for producing cement using the low-chlorine fly ash produced by the above-mentioned method, and a method for recycling incineration fly ash into a cement resource. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0017] [Method of manufacturing low-chlorine fly ash] The method for producing low-chlorine fly ash according to one embodiment is for obtaining low-chlorine fly ash having a reduced Cl content from incineration fly ash. The method for producing low-chlorine fly ash according to this embodiment includes at least a first step and a second step.

[0018] <First step> This step is a step of measuring the amounts of Al2O3 and Cl in incineration fly ash and selecting incineration fly ash having an Al2O3 amount of 9 mass% or less.

[0019] Incineration ash is generated by waste incinerators and can be broadly divided into two types: bottom ash and fly ash. Bottom ash refers to the ash that accumulates at the bottom of the incinerator, while fly ash refers to the ash that is primarily collected by the incinerator's dust collector. Incineration fly ash is primarily composed of ash, fine metal particles such as aluminum, and chlorides produced by the reaction of volatilized chlorine with sodium- or calcium-based dechlorinating agents.

[0020] In this step, incineration fly ash is prepared and the amounts of Al2O3 and Cl in the incineration fly ash are measured. The amounts of Al2O3 and Cl in the incineration fly ash can be measured by X-ray fluorescence analysis (fundamental parameter method).

[0021] By selecting incineration fly ash with an Al2O3 content of 9% by mass or less and washing it with water or acidic water to remove soluble components in the second step described below, it is possible to produce low-chlorine fly ash with a sufficiently reduced Cl content (e.g., low-chlorine fly ash with a Cl content of 1% by mass or less). The reason why selecting incineration fly ash with an Al2O3 content of 9% by mass or less achieves the effect of sufficiently reducing the Cl content is not entirely clear, but the inventors speculate as follows: Incineration fly ash reacts with water to produce sparingly soluble hydrates (e.g., Friedel's salt, Kusel's salt, etc.) consisting of calcium, aluminum, and chlorine. Therefore, when the Al2O3 content of incineration fly ash is sufficiently low, such as 9% by mass or less, the formation of these sparingly soluble hydrates is suppressed, and it is believed that washing with water or acidic water can sufficiently reduce the Cl content.

[0022] In this step, the Al2O3 content of the incineration fly ash selected is 9% by mass or less, preferably 8.5% by mass or less, more preferably 8% by mass or less, even more preferably 7.5% by mass or less, particularly preferably 7% by mass or less, and most preferably 6.5% by mass or less, because this makes it easy to obtain low-chlorine fly ash with a sufficiently reduced Cl content. The lower limit of the Al2O3 content of the incineration fly ash selected is not particularly limited, but may be 1% by mass or more, 2% by mass or more, or 3% by mass or more.

[0023] In this step, the ignition loss of the selected incineration fly ash may be 5 to 40% by mass. The ignition loss of the incineration fly ash can be measured in accordance with JIS R 5202:2015 "Methods for Chemical Analysis of Cement." The ignition loss of the incineration fly ash is preferably 7% by mass or more, more preferably 8% by mass or more, even more preferably 9% by mass or more, particularly preferably 10% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 18% by mass or less, particularly preferably 15% by mass or less.

[0024] One embodiment of this step may be a step of selecting incineration fly ash having an Al2O3 content of 9% by mass or less and a Cl content of 11% by mass or less. By selecting such incineration fly ash, the Cl content of the incineration fly ash can be sufficiently reduced by washing with water alone, without using acidic water. The Cl content of the selected incineration fly ash is 11% by mass or less, preferably 10% by mass or less, more preferably 9% by mass or less, even more preferably 8% by mass or less, and particularly preferably 7% by mass or less, because this makes it easier to obtain low-chlorine fly ash with a sufficiently reduced Cl content. The lower limit of the Cl content of the selected incineration fly ash is not particularly limited, but may be more than 1% by mass, 2% by mass or more, 3% by mass or more, or 4% by mass or more.

[0025] Another embodiment of this step may be a step of further measuring the RO content (total amount of alkali oxides converted to Na) of the incineration fly ash and selecting incineration fly ash having an AlO content of 9% by mass or less, a Cl content of more than 11% by mass, and an RO / Cl molar ratio of more than 0.35. By selecting such incineration fly ash, the Cl content of the incineration fly ash can be sufficiently reduced by washing with water alone, without using acidic water. The RO content of the incineration fly ash can be calculated using the following formula (1) by measuring the NaO and KO contents of the incineration fly ash by X-ray fluorescence analysis (fundamental parameter method). R2O = Na2O + 0.625 × K2O (1)

[0026] The upper limit of the Cl content of the selected incineration fly ash is not particularly limited, but may be 20% by mass or less, 19% by mass or less, or 18% by mass or less. The RO / Cl molar ratio of the selected incineration fly ash is greater than 0.35, preferably 0.37 or more, more preferably 0.39 or more, even more preferably 0.40 or more, and particularly preferably 0.41 or more, since this makes it easier to obtain low-chlorine fly ash with a sufficiently reduced Cl content. The upper limit of the RO / Cl molar ratio of the selected incineration fly ash is not particularly limited, but may be 0.80 or less, 0.60 or less, or 0.50 or less.

[0027] <Second process> This process involves washing the selected incineration fly ash with water or acidic water to remove soluble matter. By washing the incineration fly ash, chlorine in the incineration fly ash is dissolved and removed as soluble matter.

[0028] The method for washing incineration fly ash is not particularly limited, but examples include agitation washing, penetration washing, and sprinkling washing. Agitation washing refers to washing in which incineration ash is mixed with water or acidic water using a mixer or the like. Penetration washing refers to washing in which, after dehydration using a filter press or the like, washing water (water or acidic water) is passed through the dehydrated cake in the dehydrator without opening the dehydrator.

[0029] When incineration fly ash is washed with water, the amount of water added is preferably 1 to 20 times, more preferably 2 to 15 times, and even more preferably 3 to 12 times the mass of the incineration fly ash.

[0030] When incineration fly ash is washed with acidic water, the acid in the acidic water may be one or more acids selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid. The pH of the acidic water may be -3 to 1. The amount of acidic water added is preferably 1 to 20 times, more preferably 2 to 15 times, and even more preferably 3 to 12 times the mass of the incineration fly ash.

[0031] When incineration fly ash is stirred and washed with acidic water, the pH of the slurry containing the incineration fly ash and acidic water may be, for example, 8 to 12, and preferably 8 to 10, from the viewpoint of sufficiently reducing the amount of Cl while suppressing the dissolution of calcium components in the incineration fly ash.

[0032] In this step, the washing may be carried out once or twice or more times. The washing is preferably carried out twice or more times, since this allows the amount of Cl in the incineration fly ash to be sufficiently reduced.

[0033] When the incineration fly ash is washed two or more times, washing with water and washing with acidic water can be combined as desired. From the viewpoint of preventing the acid from remaining in the acidic water, it is preferable that the last washing be with water.

[0034] When the incineration fly ash is washed two or more times, the above washing methods can be combined arbitrarily. From the viewpoint of more sufficiently reducing the Cl content of the incineration fly ash, it is preferable that the last washing be through washing (more preferably through washing with water) and the other washings be agitation washings.

[0035] When the first step is a step of selecting incineration fly ash having an Al2O3 content of 9% by mass or less and a Cl content of 11% by mass or less, the second step may be a step of washing the selected incineration fly ash with water. By selecting such incineration fly ash, the Cl content of the incineration fly ash can be sufficiently reduced by washing with water alone, without using acidic water.

[0036] When the first step is a step of selecting incineration fly ash having an Al2O3 content of 9% by mass or less, a Cl content of more than 11% by mass, and an RO / Cl molar ratio of more than 0.35, the second step may be a step of washing the selected incineration fly ash with water. By selecting such incineration fly ash, the Cl content of the incineration fly ash can be sufficiently reduced by washing with water alone, without using acidic water.

[0037] When incineration fly ash is washed with water or acidic water, other additives may be added. Examples of such additives include polymer flocculants and dehydration aids. The timing of adding such additives can be adjusted as desired.

[0038] The manufacturing method of this embodiment may further include a third step of separating the insoluble low-chlorine fly ash from the soluble components to obtain low-chlorine fly ash. The separation of the insoluble low-chlorine fly ash from the soluble components can be carried out using a known dehydrator such as a vacuum filter, filter press, belt press, or centrifugal dehydrator. The residual solid component obtained by filtration and dehydration may be subjected to a heat-drying treatment. The heat-drying treatment conditions may be, for example, 20 to 200°C and 0.1 to 50 hours.

[0039] In this way, low-chlorine fly ash can be obtained. The low-chlorine fly ash only needs to have a lower Cl content than the incineration fly ash to be washed. The Cl content of the low-chlorine fly ash may be, for example, 1% by mass or less, preferably 0.9% by mass or less, more preferably 0.8% by mass or less, even more preferably 0.7% by mass or less, particularly preferably 0.6% by mass or less, and most preferably 0.5% by mass or less. The lower limit of the Cl content of the low-chlorine fly ash may be, for example, 0.01% by mass or more, 0.05% by mass or more, or 0.1% by mass or more.

[0040] The low-chlorine fly ash produced by the production method of this embodiment has a sufficiently reduced amount of Cl, and can therefore be used as a cement raw material.

[0041] [Method for reducing the amount of chlorine in incineration fly ash] A method for reducing the chlorine content of incineration fly ash in one embodiment includes a first step of measuring the Al2O3 and Cl contents of the incineration fly ash and selecting incineration fly ash having an Al2O3 content of 9% by mass or less, and a second step of washing the selected incineration fly ash with water or acidic water to remove soluble components. The incineration fly ash and washing method used in the method for reducing the chlorine content of incineration fly ash are the same as those used in the method for producing low-chlorine fly ash. Therefore, a redundant description will be omitted here.

[0042] [Cement manufacturing method] A method for producing cement according to one embodiment includes a step of using the low-chlorine fly ash produced by the above-described method as a cement raw material. Examples of the step of using the low-chlorine fly ash as a cement raw material include a step of mixing the low-chlorine fly ash with a cement raw material such as limestone, and a step of feeding the low-chlorine fly ash together with the cement raw material such as limestone into a kiln.

[0043] [Method of recycling low-chlorine fly ash into cement resources] In one embodiment of the method for recycling incineration fly ash into cement, the low-chlorine fly ash produced by the above-described method is used as a cement raw material. Since the Cl content of the low-chlorine fly ash produced by the above-described method is sufficiently reduced, it can be used as a cement raw material and can be recycled into cement. [Example]

[0044] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0045] [1. Incineration fly ash] Dry ash from municipal waste incineration fly ash was used as the incineration fly ash. The chemical compositions of the incineration fly ashes A to J used in the test are shown in Table 1. The chemical compositions shown in Table 1 were measured by the following methods. (1) SiO2, Al2O3, Fe2O3, CaO, MgO, SO3, R2O, and Cl content: Measured by X-ray fluorescence analysis (fundamental parameter method). (2) Ignition loss: Measured in accordance with JIS R 5202:2015 "Methods for chemical analysis of cement."

[0046] [Table 1]

[0047] [2. Incineration fly ash cleaning experiment] <Cleaning Experiment (1)> Incineration fly ash samples A, B, and G were used, each containing 9% or less Al2O3 by mass and 11% or less Cl by mass. Incineration fly ash sample D was used, containing 9% or less Al2O3 by mass and more than 11% Cl by mass. Incineration fly ash sample H was used, containing more than 9% Al2O3 by mass. For the first wash (stirring wash), 100 g of incineration fly ash and 300 g or 500 g of water were placed in a beaker and stirred at 300 rpm (revolutions per minute) using a Three-One motor for 10 minutes. Next, a polymer flocculant (MT Aquapolymer Co., Ltd., Acofloc A-110) was added and allowed to stand for 30 minutes. The supernatant water was then removed. The concentrated slurry remaining in the beaker was subjected to suction filtration using filter paper (No. 5C) to separate the solids and filtrate. Next, the second washing (through washing) was performed by adding 300, 500, or 1000 g of water to the solids separated on the filter paper while continuing suction filtration. The end point of the washing was when the filtrate stopped discharging, yielding washed ash. The washed ash was then dried at 40°C for 24 hours, after which the Cl content was measured in accordance with JIS R 5202:2015 "Methods for Chemical Analysis of Cement." The results are shown in Table 2. Since the Cl content of unwashed incineration bottom ash used as a cement raw material is typically 1% by mass, a Cl content of 1% by mass or less can be considered to have been sufficiently reduced. In Example 2, when the second washing was performed by agitation washing, the Cl content of the washed ash was 0.38% by mass, whereas the Cl content was lower when the second washing was performed by through washing.

[0048] [Table 2]

[0049] <Cleaning Experiment (2)> Incineration fly ash G was used as incineration fly ash having an Al2O3 content of 9% by mass or less and a Cl content of 11% by mass or less; incineration fly ash C and E were used as incineration fly ash having an Al2O3 content of 9% by mass or less and a Cl content of more than 11% by mass; and incineration fly ash H was used as incineration fly ash having an Al2O3 content of more than 9% by mass. In Examples 6 to 8, 11, and Comparative Example 2, the second washing (water, through-washing) was performed in the same manner as in Example 1 or Example 5, except that hydrochloric acid was added to the first washing (acidic water, stirring washing) to adjust the pH of the slurry to 8 or 10. In Examples 9 and 10, the incineration fly ash was washed by adding hydrochloric acid or sulfuric acid to the first washing (acidic water, stirring washing) to adjust the pH of the slurry to 8, followed by a second washing (acidic water, stirring washing) under the same conditions as the first washing, and then a third washing (water, through-washing) under the same conditions as the first washing. The Cl content of the resulting washed ash was measured in the same manner as above, and the results are shown in Table 3.

[0050] [Table 3]

[0051] <Cleaning Experiment (3)> Incineration fly ashes F, I, J, and E were used as incineration fly ashes having an Al2O3 content of 9% by mass or less, a Cl content of more than 11% by mass, and an RO / Cl molar ratio of more than 0.35. The incineration fly ashes were washed in the same manner as in Example 1. The Cl content of the washed ashes was measured in the same manner as above. The results are shown in Table 4.

[0052] [Table 4]

[0053] As shown in Tables 2, 3, and 4, it was found that the Cl content of incineration fly ash containing 9% or less AlO by mass (incineration fly ashes A to G, I, and J) could be reduced to 1% or less by washing with water or acidic water. It was also found that the Cl content of incineration fly ash containing 9% or less AlO by mass and 11% or less Cl by washing with water (incineration fly ashes A, B, and G) could be sufficiently reduced by washing with water (Table 3). It was also found that the Cl content of incineration fly ash containing 9% or less AlO by mass, more than 11% Cl by mass, and an RO / Cl molar ratio exceeding 0.35 (incineration fly ashes E, F, I, and J) could be sufficiently reduced by washing with water (Table 4). From the above, it was confirmed that the method for producing low-chlorine fly ash of the present invention can produce low-chlorine fly ash with a reduced chlorine content from incineration fly ash.

Claims

1. A method for producing low-chlorine fly ash in which the amount of chlorine is reduced from incineration fly ash, Al in incineration fly ash ２ O ３ The amount of Al and Cl were measured. ２ O ３ A first step of selecting incineration fly ash having a C content of 9% by mass or less and a Cl content of 11% by mass or less; a second step of washing the selected incineration fly ash with water to remove soluble components; Equipped with A method for producing low-chlorine fly ash.

2. In the second step, the number of washing steps is two or more. The method for producing low-chlorine fly ash according to claim 1.

3. In the second step, the last cleaning is a penetration cleaning, and the other cleanings are agitation cleanings. The method for producing low-chlorine fly ash according to claim 2.

4. The ignition loss of the incineration fly ash is 5 to 40% by mass. The method for producing low-chlorine fly ash according to any one of claims 1 to 3.

5. A method for reducing the amount of chlorine in incineration fly ash, comprising: Al in incineration fly ash ２ O ３ The amount of Al and Cl were measured. ２ O ３ A first step of selecting incineration fly ash having a C content of 9% by mass or less and a Cl content of 11% by mass or less; a second step of washing the selected incineration fly ash with water to remove soluble components; Equipped with Method for reducing the amount of chlorine in incineration fly ash.

6. The method according to any one of claims 1 to 4, further comprising a step of using the low-chlorine fly ash produced by the method as a cement raw material. Cement manufacturing method.

7. The low-chlorine fly ash produced by the production method according to any one of claims 1 to 4 is used as a cement raw material. A method for recycling incineration fly ash into cement resources.

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