Method for producing low-chlorine fly ash, method for reducing the chlorine content of incinerated fly ash, method for producing cement, and method for utilizing incinerated fly ash as cement resources.

Abstract

To provide a method for producing low-chlorine fly ash, which has a reduced chlorine content, from incinerator fly ash. [Solution] A method for producing low-chlorine fly ash is disclosed. This method comprises a first step of measuring the amount of Al2O3, Cl, and R2O in the incineration fly ash and selecting incineration fly ash in which the amount of Al2O3 is 9% by mass or less, the amount of Cl is 11% by mass or more, and the R2O / Cl molar ratio is 0.35 or more; and a second step of washing the selected incineration fly ash with water to remove soluble matter.

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 as cement resources.

Background Art

[0002] A method is conventionally known in which incineration fly ash is washed, the chlorine in the incineration fly ash is desalted, and the obtained dewatered cake is used as a cement raw material. For example, Patent Documents 1 and 2 disclose a method in which water or water and an acid are added to incineration fly ash and suspended to elute chlorine, and the dewatered cake obtained by dehydrating this with a dehydrator is used as a cement raw material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

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

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

Means for Solving the Problems

[0006] As a result of diligent research by the inventors to solve the above problems, they found that the chlorine removal rate when washing incinerated fly ash differs depending on the amount of components in the fly ash. Based on this finding, the inventors discovered that by focusing on specific components, the amount of chlorine in incinerated fly ash can be sufficiently reduced by washing the 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, which has a reduced chlorine content (Cl content), from incinerator fly ash. The production method comprises a first step of measuring the Al2O3 and Cl content of the incinerator fly ash and selecting incinerator fly ash in which the Al2O3 content is 9% by mass or less, and a second step of washing the selected incinerator fly ash with water or acidic water to remove soluble components. In the second step, when the incinerator fly ash is stirred and washed with acidic water, the pH of the slurry containing the incinerator fly ash and acidic water may be 8 to 12. According to the inventors' studies, it has been found that by selecting incinerator fly ash in which the Al2O3 content is 9% by mass or less and washing it with water or acidic water, the chlorine in the incinerator fly ash can be sufficiently removed. Therefore, according to the production method, it is possible to produce low-chlorine fly ash with a reduced Cl content from incinerator fly ash.

[0008] One embodiment of the first step may be a step of selecting incinerated 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 incinerated fly ash with water. According to the inventors' studies, it has been found that by selecting such incinerated fly ash, chlorine in the incinerated fly ash can be removed more sufficiently 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 cause scaling problems in equipment when dissolved.

[0009] Another aspect of the first step may be a step of further measuring the amount of R2O (alkali oxide) in the incinerated fly ash and selecting incinerated fly ash in which the amount of Al2O3 is 9% by mass or less, the amount of Cl is greater than 11% by mass, and the R2O / Cl molar ratio is greater than 0.35. In this case, the second step may be a step of washing the selected incinerated fly ash with water. According to the inventors' studies, it has been found that by selecting such incinerated fly ash, chlorine in the incinerated fly ash can be removed more sufficiently 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 cause scaling problems in equipment when dissolved.

[0010] In the second step, the number of washes may be two or more. In this case, it is preferable that the last wash is a through wash and the other washes are agitation washes.

[0011] The loss on ignition of incinerated 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 incinerated fly ash. This reduction method comprises a first step of measuring the amount of Al2O3 and Cl in the incinerated fly ash and selecting incinerated fly ash in which the amount of Al2O3 is 9% by mass or less, and a second step of washing the selected incinerated 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. This method comprises a step of using 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 converting incinerated fly ash into cement resources. This cement resource conversion method uses low-chlorine fly ash produced by the above-described manufacturing method as a cement raw material. [Effects of the Invention]

[0015] The present invention provides a method for producing low-chlorine fly ash, which has a reduced chlorine content, from incinerated fly ash. The present invention also provides a method for reducing the chlorine content of incinerated fly ash. Furthermore, the present invention provides a method for producing cement using the low-chlorine fly ash produced by the above method, and a method for utilizing incinerated fly ash as a cement resource. [Modes for carrying out the invention]

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

[0017] [Method for producing low-chlorine fly ash] One embodiment of the method for producing low-chlorine fly ash involves obtaining low-chlorine fly ash with reduced Cl content from incinerated fly ash. The method for producing low-chlorine fly ash according to this embodiment comprises at least a first step and a second step.

[0018] <First step> This process involves measuring the amount of Al2O3 and Cl in the incinerated fly ash and selecting incinerated fly ash in which the Al2O3 content is 9% by mass or less.

[0019] Incineration ash is the ash generated in waste incinerators and is broadly classified 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 mainly collected by the dust collector of the incinerator. Fly ash is mainly composed of ash content, fine metal particles such as aluminum, and chlorides produced by the reaction of volatile chlorine with sodium-based or calcium-based chemicals added as desalination agents.

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

[0021] Select incineration fly ash with an Al₂O₃ content of 9% by mass or less, and in the second step described below, wash it with water or acidic water to remove soluble components, thereby enabling the production of low-chlorine fly ash with a sufficiently reduced Cl content (for example, low-chlorine fly ash with a Cl content of 1% by mass or less). The reason why the effect of sufficiently reducing the Cl content can be achieved by selecting incineration fly ash with an Al₂O₃ content of 9% by mass or less is not necessarily clear, but the inventors of the present invention speculate as follows. Incineration fly ash reacts with water to form insoluble hydrates (such as Friedel's salt, Kuzel's salt, etc.) composed of calcium, aluminum, and chlorine. Therefore, when the Al₂O₃ content of the incineration fly ash is sufficiently low, i.e., 9% by mass or less, the formation of the insoluble hydrate is suppressed, and it is considered that the Cl content can be sufficiently reduced by washing with water or acidic water.

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

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

[0024] One aspect of this process may be a step of selecting incineration fly ash with 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 only water 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, still more preferably 8% by mass or less, and particularly preferably 7% by mass or less, because it is 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 aspect of this process may be a step of further measuring the R₂O content (total amount of alkali oxides in terms of Na) of the incineration fly ash and selecting incineration fly ash with an Al₂O₃ content of 9% by mass or less, a Cl content exceeding 11% by mass, and an R₂O / Cl molar ratio exceeding 0.35. By selecting such incineration fly ash, the Cl content of the incineration fly ash can be sufficiently reduced by washing with only water without using acidic water. The R₂O content of the incineration fly ash can be determined using the following formula (1) by measuring the Na₂O and K₂O contents of the incineration fly ash by fluorescent X-ray 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 R₂O / Cl molar ratio of the selected incineration fly ash exceeds 0.35, preferably 0.37 or more, more preferably 0.39 or more, still more preferably 0.40 or more, and particularly preferably 0.41 or more, because it is easier to obtain low-chlorine fly ash with a sufficiently reduced Cl content. The upper limit of the R₂O / 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] <The second step> This process involves washing the selected incinerator fly ash with water or acidic water to remove soluble components. By washing the incinerator fly ash, chlorine in the fly ash is leached out and removed as soluble components.

[0028] There are no particular restrictions on the method of washing incinerated fly ash, but examples include agitation washing, through washing, and water spray washing. Agitation washing refers to washing by mixing incinerated ash with water or acidic water using a mixer or the like. Through washing refers to washing by passing washing water (water or acidic water) through the dewatered cake inside the dewatering machine without opening the frame of the dewatering machine after dewatering with a filter press or the like.

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

[0030] When washing incinerator fly ash with acidic water, the acid in the acidic water may be one or more 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 the mass of the incinerator fly ash, more preferably 2 to 15 times, and even more preferably 3 to 12 times.

[0031] When incinerator fly ash is washed by stirring with acidic water, the pH of the slurry containing the incinerator 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 the calcium component of the incinerator fly ash.

[0032] In this process, the number of washes may be one or two or more. However, it is preferable to wash the material two or more times, as this allows for a sufficient reduction in the amount of Cl in the incinerated fly ash.

[0033] If the incinerated 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 residual acid from acidic water, it is preferable that the final washing be done with water.

[0034] If the incinerated fly ash is washed two or more times, the above washing methods can be combined as desired. From the viewpoint of more sufficiently reducing the amount of Cl in the incinerated fly ash, it is preferable that the last washing is through washing (more preferably through washing with water), and the other washings are agitation washing.

[0035] If the first step is to select incinerator 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 to wash the selected incinerator fly ash with water. By selecting such incinerator fly ash, the Cl content of the incinerator fly ash can be sufficiently reduced by washing with water alone, without using acidic water.

[0036] If the first step is to select incinerator fly ash in which the Al2O3 content is 9% by mass or less, the Cl content exceeds 11% by mass, and the R2O / Cl molar ratio exceeds 0.35, then the second step may be to wash the selected incinerator fly ash with water. By selecting such incinerator fly ash, the Cl content of the incinerator fly ash can be sufficiently reduced by washing with water alone, without using acidic water.

[0037] When washing incinerated fly ash with water or acidic water, other additives may be added. Examples of other additives include polymer flocculants and dehydration aids. The timing of adding these other additives can be adjusted as needed.

[0038] The manufacturing method of this embodiment may further include a third step of separating insoluble low-chlorine fly ash from soluble components to obtain low-chlorine fly ash. The separation of insoluble low-chlorine fly ash from soluble components can be carried out using known dewatering machines such as vacuum filters, filter presses, belt presses, and centrifugal dewaterers. The residual solids obtained by filtration and dewatering may be subjected to heat drying treatment. The conditions for heat drying treatment can be, for example, 20 to 200°C for 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 incinerated fly ash that is 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 manufacturing method of this embodiment can be used as a cement raw material because its Cl content is sufficiently reduced.

[0041] [Methods for reducing the chlorine content of incinerator fly ash] One embodiment of the method for reducing the chlorine content of incinerator fly ash comprises a first step of measuring the Al2O3 and Cl content of the incinerator fly ash and selecting incinerator fly ash in which the Al2O3 content is 9% by mass or less, and a second step of washing the selected incinerator fly ash with water or acidic water to remove soluble components. The incinerator fly ash and washing method used in the method for reducing the chlorine content of incinerator fly ash are the same as those used in the method for producing low-chlorine fly ash. Therefore, redundant explanations are omitted here.

[0042] [Method of manufacturing cement] One embodiment of the cement manufacturing method includes a step of using low-chlorine fly ash produced by the above manufacturing method as a cement raw material. Examples of the step of using low-chlorine fly ash as a cement raw material include a step of mixing low-chlorine fly ash with a cement raw material such as limestone, and a step of feeding low-chlorine fly ash together with a cement raw material such as limestone into a kiln.

[0043] [Method for utilizing low-chlorine fly ash as a cement resource] One embodiment of the method for converting incinerated fly ash into cement resources involves using low-chlorine fly ash produced by the above manufacturing method as a cement raw material. Since the low-chlorine fly ash produced by the above manufacturing method has a sufficiently reduced Cl content, it can be used as a cement raw material, making cement resource conversion possible. [Examples]

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

[0045] [1. Incinerator fly ash] Dry ash from municipal solid waste incineration was used as the incinerator fly ash. The chemical composition of incinerator fly ashes A to J used in the test is shown in Table 1. The chemical composition shown in Table 1 is the value measured by the following method. (1) Amounts of SiO2, Al2O3, Fe2O3, CaO, MgO, SO3, R2O, and Cl: Measured by X-ray fluorescence analysis (fundamental parameter method). (2) Loss on ignition: Measured in accordance with JIS R 5202:2015 "Methods for chemical analysis of cement".

[0046] [Table 1]

[0047] [2. Experiment on washing incinerator fly ash] <Washing experiment (1)> Incineration fly ash A, B, and G were used as incineration fly ash with an Al2O3 content of 9% by mass or less and a Cl content of 11% by mass or less. Incineration fly ash D was used as incineration fly ash with an Al2O3 content of 9% by mass or less and a Cl content of more than 11% by mass. Incineration fly ash H was used as incineration fly ash with an Al2O3 content of more than 9% by mass. First, for the first washing (agitation washing), 100g of incineration fly ash and 300g or 500g of water were placed in a beaker and stirred for 10 minutes at 300 rpm (revolutions / min) using a three-one motor. Next, a polymer flocculant (Akofloc A-110, manufactured by MT Aquapolymer Co., Ltd.) was added and allowed to stand for 30 minutes, after which the supernatant water was removed. The concentrated slurry remaining in the beaker was separated into solid and filtrate by suction filtration using filter paper (No. 5C). Next, the second washing (through washing) was performed by adding 300, 500 g, or 1000 g of water to the solids separated on the filter paper while continuing suction filtration. The washing was terminated when the discharge of the filtrate stopped, and washing ash was obtained. After drying the washing ash at 40°C for 24 hours, the amount of Cl was measured in accordance with JIS R 5202:2015 "Methods for Chemical Analysis of Cement". The results are shown in Table 2. Since the amount of Cl in unwashed incinerated bottom ash used as a cement raw material is usually 1% by mass, an amount of Cl of 1% by mass or less indicates that the amount of Cl has been sufficiently reduced. Note that in Example 2, when the second washing was performed by agitation washing, the amount of Cl in the washing ash was 0.38% by mass, indicating that the amount of Cl was lower when the second washing was performed by through washing.

[0048] [Table 2]

[0049] <Washing experiment (2)> Incineration fly ash G was used as incineration fly ash with an Al2O3 content of 9% by mass or less and a Cl content of 11% by mass or less; incineration fly ashes C and E were used as incineration fly ash with 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 with an Al2O3 content of more than 9% by mass. Examples 6-8, 11 and Comparative Example 2 were washed in the same manner as in Example 1 or Example 5, except that hydrochloric acid was added during the first wash (acidic water, agitated wash) to adjust the pH of the slurry to 8 or 10 before washing. Examples 9 and 10 were washed in the same manner as in Example 1 or Example 5, with a second wash (water, through wash) performed. The amount of Cl in the obtained washing ash was measured in the same manner as described above. The results are shown in Table 3.

[0050] [Table 3]

[0051] <Washing 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 exceeding 11% by mass, and an R2O / Cl molar ratio exceeding 0.35. The incineration fly ash was washed in the same manner as in Example 1. The Cl content of the obtained washed ash 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 amount of Cl in the washed ash could be reduced to 1% by mass or less by washing with water or acidic water for incinerator fly ash with an Al2O3 content of 9% by mass or less (incinerator fly ash A-G, I, J). Furthermore, it was found that the amount of Cl in the washed ash could be sufficiently reduced by washing with water for incinerator fly ash with an Al2O3 content of 9% by mass or less and a Cl content of 11% by mass or less (incinerator fly ash A, B, G) (Table 3). Moreover, it was found that the amount of Cl in the washed ash could be sufficiently reduced by washing with water even for incinerator fly ash with an Al2O3 content of 9% by mass or less, a Cl content exceeding 11% by mass, and an R2O / Cl molar ratio exceeding 0.35 (incinerator fly ash E, F, I, J) (Table 4). Based on the above, it was confirmed that the method for producing low-chlorine fly ash of the present invention makes it possible to produce low-chlorine fly ash with reduced chlorine content from incinerator fly ash.

Claims

1. A method for producing low-chlorine fly ash, which has a reduced chlorine content from incinerator fly ash, Al in incinerator fly ash ２ O ３ Quantity, amount of Cl, and R ２ Measure the amount of O, Al ２ O ３ The amount is 9% by mass or less, the amount of Cl is greater than 11% by mass, and R ２ The first step is to select incineration fly ash with an O / Cl molar ratio exceeding 0.35, A second step involves washing the selected incinerated fly ash with water to remove soluble matter, Equipped with, A method for producing low-chlorine fly ash.

2. In the second step described above, the number of washes is two or more. A method for producing low-chlorine fly ash according to claim 1.

3. In the second step described above, the last wash is a through wash, and the other washes are agitation washes. A method for producing low-chlorine fly ash according to claim 2.

4. The loss on ignition of the aforementioned incinerated fly ash is 5 to 40% by mass. A 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 incinerated fly ash, Al content of incineration fly ash ２ O ３ content, Cl content, and R ２ O content are measured, and the first step of selecting incineration fly ash with an Al ２ O ３ content of 9% by mass or less, a Cl content exceeding 11% by mass, and an R ２ O / Cl molar ratio exceeding 0.35 A second step involves washing the selected incinerated fly ash with water to remove soluble matter, Equipped with, Methods for reducing the chlorine content of incinerator fly ash.

6. The process includes a step of using low-chlorine fly ash, produced by the manufacturing method described in any one of claims 1 to 4, as a cement raw material. A method for manufacturing cement.

7. Low-chlorine fly ash produced by the manufacturing method described in any one of claims 1 to 4 is used as a cement raw material. A method for recycling incinerated fly ash into cement resources.

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