JP2005313147A - Method for processing incineration ash - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make an effective use of incineration ash for various applications such as a soil amendment, a grassland amendment, a landfill and a bank which have no fear of causing soil contamination and water contamination by suppressing the elution of fluorine in the incineration ash. <P>SOLUTION: A method for processing fluorine-containing incineration ash includes the step of adding water to a calcium compound and an aluminum sulfate, further adding alumina cement as needed and mixing the mixture thus obtained with the incineration ash containing the fluorine obtained by processing a discharge gas when burning coal, RPF (recycle plastic fuel) and papermaking sludge by using an electric dust collector or a bag filter so that the fluorine contained in the incineration ash is insolubilized to an elution amount of the fluorine less than 0.8 mg/L when the fluorine is eluted by an elution testing process based on the Notification No. 18 of the Environment Agency in 2003. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a treatment agent and a treatment method for fluorine-containing combustion ash. Specifically, the present invention conforms to the elution standard value of fluorine, which is a regulated substance in the Soil Contamination Countermeasures Law enacted in February 2003 by the Ministry of the Environment. It is related with the processing method of the combustion ash which makes the elution amount of 0.8 mg / L or less. Furthermore, the present invention relates to a method for treating combustion ash for treating combustion ash containing boron together with fluorine to adjust both the elution amounts of fluorine and boron to a reference value.

  Fluorine has been effective in preventing tooth decay, but its overdose is not limited to patchy teeth, deforms bones and joints, causes osteosclerosis, and causes a disease called fluorosis that affects the nervous system. It has been known that There is currently no cure for this fluorosis, and prevention is the only countermeasure to avoid it, so we believe that these insolubilization technologies will play an important role in areas with fluorine-containing soil. It is done.

  Fluorine is also contained in combustion ash from household waste incineration ash, coal combustion ash (coal ash) from thermal power plants, sewage sludge incineration ash, various industrial wastes, etc. Since the coal originally contains several to several hundred mg / kg of fluorine, the content of fluorine or a fluorine compound is high. In addition, since most of the combustion ash is used as a soil conditioner or backfill material, there is a concern that it will be eluted by rain and cause groundwater contamination. In addition, since there is also a shortage of landfills where the combustion ash is reclaimed, it is desired that the fluorine in the combustion ash be made non-eluting for effective use.

  As methods for detoxifying harmful substances in combustion ash, melt solidification methods, cement solidification, treatment with chemicals, extraction treatment with acids or other solvents have been proposed.

  In the melt-solidification method, waste is heated to a high temperature of 1400 to 1600 ° C. to decompose the organic matter, and is contained and fixed in slag that generates fluorine and heavy metals. This method is said to have the highest safety, but there are problems with fly ash treatment that contains newly generated higher concentrations of harmful substances, and the highest processing cost is also a problem. ing.

  The processing method (for example, patent document 1) which solidifies combustion ash with blast furnace cement or normal cement may not be durable even if it solidifies once depending on the property of ash, for example, it used as cement. In some cases, the concrete is weathered and the ash component is eluted, which may cause contamination.

  In addition, there is a method of solidifying and insolubilizing by adding a treatment agent composed of an inorganic agent or an organic agent when solidifying with ordinary cement (for example, Patent Document 2), but the cost is high because several steps are required for the treatment. It is also necessary to consider the post-treatment of the drug used in the treatment stage.

  In a treatment method (for example, Patent Document 3) in which a phosphoric acid compound and a calcium compound are added to a fluorine-containing waste and kneaded (for example, Patent Document 3), the price of the phosphoric acid compound is extremely high, 10 to 15 times that of hydrochloric acid or sulfuric acid. Moreover, since it is necessary to make the addition rate of a phosphoric acid compound 5% or more in order to make it 0.8 mg / L or less of a soil environment standard value, processing cost is too much and it is not practical.

  Also, after mixing the combustion ash with water, dehydrating it to remove water-soluble chlorine, and further pyrolyzing it in water vapor at 400 ° C. or higher, the fluorine is gasified as hydrofluoric acid and removed (for example, In the case of Patent Document 4), since it is necessary to heat at a high temperature of 400 ° C. or higher, the cost is high, and it cannot be said that it is practical as a treatment method for using ash for an inexpensive application such as a soil improvement material.

Furthermore, the method (patent document 5) which adds calcium aluminate (addition rate 20-80 mass%) and gypsum (10-80 mass%) and suppresses the fluorine elution in steelmaking slag is used by an iron-making process. The fluorine content derived from meteorite is very high, so the addition rate of the treatment agent to make it below the environmental standard value is very high, and not only the chemical cost for the treatment of combustion ash but also the transportation cost is added up. This is not a good idea. Steel slag is a by-product discharged by burning iron ore, limestone, coke, etc. in order to produce pig iron. Therefore, the main component is CaO, and it contains a large amount of MgO, FeO, Fe ₂ O _{3 and the} like. On the other hand, coal ash, the main component, such as incinerator ash or RPF ash in the SiO _2, CaO can also be applied this technique to the combustion ash that is not accustomed contains only about 5% to 10%, it does not make enough crystals of ettringite The effect of suppressing fluorine elution is not exhibited.
Japanese Patent Laid-Open No. 2003-119057 JP-A-6-15248 JP 2002-331272 A Japanese Patent Laid-Open No. 9-165243 JP 2001-259570 A

The present invention is conventionally known as a method for suppressing elution of fluorine from ash discharged from coal boilers or RPF boilers using RPF as a fuel, and is complicated such as cement solidification and melting as described above and high addition of processing agents. The purpose of this project is to provide a simple and inexpensive method to replace the time-consuming method, and by improving the elution of fluorine in the incinerated ash, soil improvement that does not cause soil contamination and water contamination It aims at making combustion ash available effectively for various uses such as wood, grassland improvement material, backfilling material and embankment.
The present invention also relates to a method for treating combustion ash for treating combustion ash containing not only fluorine but also boron so as to adapt both elution amounts of fluorine and boron to a reference value.

  The present invention capable of achieving the above object is basically obtained when exhaust gas combusted with coal, RPF (Refused Paper & Plastics Fuel), paper sludge or the like is treated with an electric dust collector or a bag filter. The combustion ash was mixed with calcium compounds, aluminum sulfates and water, and the fluorine contained in the combustion ash was eluted by the dissolution test method based on the 2003 Environment Agency Notification No. 18 This is a method for treating fluorine-containing combustion ash comprising the elution amount in the case of 0.8 mg / L or less, and includes the following inventions.

(1) Fluorine-containing combustion ash obtained by treating exhaust gas from burning coal, RPF, paper sludge, etc. with an electrostatic precipitator or bag filter, and adding water to calcium compounds and aluminum sulfates As a result, the fluorine contained in the combustion ash is insolubilized so that the amount of fluorine eluted when it is eluted by the dissolution test method based on Notification No. 18 of the 2003 Environmental Agency is 0.8 mg / L or less. The processing method of the fluorine containing combustion ash which consists of this.

(2) Fluorine-containing combustion ash obtained by treating exhaust gas from burning coal, RPF, papermaking sludge, etc. with an electric dust collector or bag filter, and adding water to calcium compounds, aluminum sulfates and alumina cement As a result, the fluorine elution amount when the fluorine contained in the combustion ash is eluted by the elution test method based on the Environmental Agency Notification No. 18 of 2003 is 0.8 mg / L or less. A method for treating fluorine-containing combustion ash comprising insolubilizing in water.

(3) The calcium compound used for the treatment of combustion ash is any one of quick lime, limestone, dolomite, scallop, paper sludge, and calcined lime derived from waste paper mash, or a combination of any ratio thereof (1) Item (2) or the method for treating fluorine-containing combustion ash according to item (2).

(4) The aluminum sulfate used in the treatment of combustion ash is selected from anhydrous aluminum sulfate and aluminum sulfate 14-18 hydrate, any one of items (1) to (3) Of fluorine-containing combustion ash.

(5) The calcium compound used for the treatment of the combustion ash is added in a proportion of 5 parts by mass or more with respect to 100 parts by mass of the combustion ash, according to any one of items (1) to (4) Of fluorine-containing combustion ash.

(6) The method for treating fluorine-containing combustion ash according to (5), wherein the combustion ash is combustion ash containing boron together with fluorine.

  In the present invention, fluorine-containing combustion ash generated from a coal boiler, an RPF boiler, an incinerator or the like is mixed with calcium compound and aluminum sulfate and stirred or mixed, or the calcium compound and aluminum sulfate are further mixed with alumina cement. Since the elution of fluorine contained in combustion ash can be suppressed by adding water to the mixture with added water, adverse effects on the environment such as soil improvement materials, grassland improvement materials, backfill materials, banking, etc. It is possible to use it soon.

Hereinafter, the present invention will be specifically described.
Normally, when fluorine contained in combustion ash or the like forms calcium sulfoaluminate hydrate called ettringite crystal in the combustion ash, fluorine is taken into this crystal and fixation is achieved. When the present inventors coexist with a calcium compound and aluminum sulfate as a treating agent for immobilizing fluorine contained in combustion ash and the like, and when mixed with incinerated ash in the presence of water, ettringite crystals are rapidly formed, which is surprising. It has been found that, within a few hours after the treatment, this crystal structure has the effect of incorporating fluorine and insolubilizing it. Even more surprisingly, even in the case of incinerated ash with a high fluorine content and elution suppression that is not complete in the above treatment, in addition to the calcium compound and aluminum sulfate, the addition of alumina cement further increases the strength. It has been found that a crystal structure can be formed and there is an effect of insolubilizing fluorine almost completely.

  The calcium compound used in the present invention needs to incorporate fluorine and fluorine compound in the combustion ash into the crystal structure, and the calcium compound for that purpose is calcined from quick lime, limestone, dolomite, scallops, paper sludge and waste paper straw Examples include lime. These calcium compounds can be used in combination of one or more kinds in combination of any ratio thereof.

  Examples of the aluminum sulfates used in the present invention include anhydrous aluminum sulfate, aluminum sulfate 14-18 hydrate, aluminum potassium sulfate 12 hydrate, aluminum aluminum sulfate 12 hydrate, ammonium aluminum sulfate 12 hydrate, and the like. Any of them may be used in combination of two or more, but preferably anhydrous aluminum sulfate and aluminum sulfate 14-18 hydrate are desirable. Anhydrous aluminum sulfate and aluminum sulfate 14-18 hydrate are preferred because they are used as papermaking materials, are easily available, and are easy to handle. It is said that the sulfate radical is generally used as a component necessary for composing fluorine ettringite. However, in terms of insolubilization of combustion ash, sulfuric acid, calcium sulfate, magnesium sulfate, aluminum sulfate, iron sulfate, etc. However, it does not exhibit a sufficient inhibitory effect, and by using aluminum sulfates among sulfuric acid compounds, a rapid and stable elution inhibitory effect is manifested. This is considered as another mechanism for insolubilizing fluorine in the present invention, because water is interposed and calcium ions, aluminum ions and fluorine ions react to form a hardly soluble compound. For this reason, it is considered that aluminum sulfate is completely ionized by the presence of water and plays an important role in suppressing fluorine elution very quickly.

The mass ratio of combustion ash / calcium compound when treating with combustion ash and calcium compound, aluminum sulfate and water is preferably in the range of 200/1 to 100/10, more preferably 100/1 to 100/10. . If the mass ratio is less than 200/1, fluorine cannot be fixed sufficiently. On the other hand, if it exceeds 100/10, the absolute amount after treatment increases, and there is a limitation in use, and the cost is also low. Since it increases, it is not practical.
The mass ratio of combustion ash / aluminum sulfate is preferably in the range of 200/1 to 100/10, more preferably 100/1 to 100/10.
5-30 mass% is preferable with respect to combustion ash, and, as for the quantity of the water to add, More preferably, 10-30 mass% is good. The water to be added may be added as an aqueous solution in which other water-soluble components are dissolved.

  In particular, when the content of fluorine in the combustion ash exceeds 200 mg / kg, it is preferable to further add alumina cement to the calcium compound, aluminum sulfates and water. Alumina cement is a kind of special cement used as a binder for refractory materials, and is produced from an alumina material and a calcareous material. 0.5-20 mass parts is preferable with respect to 100 mass parts of combustion ash, and, as for the addition amount of an alumina cement, 1-10 mass parts is more preferable.

  After adding calcium compounds, aluminum sulfates, and water to the combustion ash, it is preferable to stir well. By stirring, the additives are more evenly dispersed in the combustion ash, and a minimum amount of fluorine is required. Immobilization can be performed. According to the treatment method of the present invention, since odor and heat are not generated during the treatment, the treatment method is extremely safe.

  The treatment method of the present invention is carried out so that the treated combustion ash has an elution amount of fluorine of 0.8 mg / L or less, which is eluted by the dissolution test method based on the Environmental Agency Notification No. 18 of 2003. When such treatment is performed, elution of heavy metals other than fluorine can be suppressed. For example, in the case of combustion ash that also contains boron, it is possible to keep the elution amount below a reference value by increasing the amount of calcium compound added. In addition, the form of the incinerated ash after the stirring and mixing treatment is also easy to handle because it is in a wet state, and is convenient for use in various applications such as soil improving materials, grassland improving materials, backfilling materials, banking and the like.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is, of course, not limited to these examples, and may be implemented without departing from the spirit of the present invention. Aspects can be changed.

  In addition, the combustion ash used as a sample for the fluorine elution suppression treatment in the following examples and comparative examples is EP ash A captured by an electric dust collector of a stalker furnace using coal as fuel, and the same coal as fuel. The bag ash B captured by the bag filter of the bubbling fluidized bed furnace. The chemical composition, fluorine content, and elution amount are as shown in Table 1 below, and bag ash B has a higher fluorine content and elution amount.

1) Fluorine elution method In each of the following Examples and Comparative Examples, the fluorine elution test was conducted according to Notification No. 18 of the 2003 Environment Agency. That is, fly ash collected by an electric dust collector (EP) in the flue of a stalker furnace or pulverized coal furnace, or fly ash collected by a bag filter installed in the flue of a fluidized bed combustion furnace After air-drying, medium pebbles, wood chips, etc. are removed and the aggregate is pulverized, it is passed through a non-metallic sieve having an opening of 2 mm and mixed well. 50 g of this sample is put into a 1000 ml polyethylene container with a lid, and 500 ml of pure water (pH 5.8 to 6.3) is added. The prepared sample solution was shaken continuously at room temperature and atmospheric pressure for 6 hours using an industrial waste elution shaker (manufactured by Taitec Co., Ltd.) (shaking width: 4 to 5 cm, frequency: 200 times / min). This solution was allowed to stand for 30 minutes, and then centrifuged at about 3000 rpm for 20 minutes. The supernatant was filtered through a membrane filter having a pore size of 0.45 μm, the filtrate was taken, the amount required for quantification was accurately measured, and this was used as a test solution.

2) Measuring method of fluorine The test solution was analyzed with an ion chromatograph (DX-120 / DIONEX), and the eluted fluorine was quantified.

3) Measuring method of boron The test solution was analyzed with IPC-OES (inductively coupled plasma optical emission spectrometer, Rigaku / Spectoro, CIROS-120 type), and the amount of boron eluted was quantified.

Example 1
Weigh 500 g of coal ash EP ash A in a vinyl bag, add 15 g of kiln calcined lime, and add 46 g of aluminum sulfate 14-18 hydrate as aluminum sulfate to 5 parts by mass with respect to the ash, and then stir well Then, 104 ml of pure water was sprayed and stirred uniformly with a spray. The obtained treated ash was cured for 3 hours and analyzed by the above elution method and measurement method to determine the elution amount of fluorine. The results are shown in Table 2.

Example 2
Weigh 500g of coal boiler EP ash A in a vinyl bag, add 15g of kiln calcined lime and 25g of anhydrous aluminum sulfate as aluminum sulfate, stir well, then spray 125ml of pure water with spray to make it uniform , Stirred. The obtained treated ash was cured for 3 hours and analyzed by the above elution method and measurement method to determine the elution amount of fluorine. The results are shown in Table 2.

Example 3
500 g of coal ash EP ash A was weighed into a vinyl bag, 15 g of kiln calcined lime, and aluminum sulfate 14-18 hydrate as aluminum sulfate were added to 46 g so as to be 5 parts by mass, and 15 g of alumina cement was added. After sufficient stirring, 104 ml of pure water was sprayed and stirred uniformly with a spray. The obtained treated ash was cured for 3 hours and analyzed by the above elution method and measurement method to determine the elution amount of fluorine. The results are shown in Table 2.

Example 4
500 g of coal boiler bug ash B was weighed in a vinyl bag, and 46 g of alumina cement 15 g was added to 15 g of kiln calcined lime, aluminum sulfate 14-18 hydrate as aluminum sulfate and 5 parts by mass with respect to the ash. Thereafter, the mixture was sufficiently stirred, and then 104 ml of pure water was sprayed and stirred uniformly with a spray. The obtained treated ash was cured for 3 hours and analyzed by the above elution method and measurement method to determine the elution amount of fluorine. The results are shown in Table 2.

Example 5
500 g of coal boiler EP ash A was weighed into a vinyl bag, 25 g of kiln calcined lime was added, 46 g of aluminum sulfate 14-18 hydrate as aluminum sulfate was added to 5 parts by mass, and 15 g of alumina cement was added. Thereafter, the mixture was sufficiently stirred, and then 104 ml of pure water was sprayed and stirred uniformly with a spray. The obtained treated ash was cured for 3 hours and analyzed by the above elution method and measurement method to determine the elution amount of fluorine. The results are shown in Table 2.

Comparative Example 1
After spraying and stirring 125 ml of pure water uniformly onto EP ash A of a coal boiler, the mixture was cured for 3 hours. This untreated ash was analyzed by the above elution method and measurement method, and the elution amount of fluorine was determined. The results are shown in Table 2.

Comparative Example 2
500 g of EP ash A from a coal boiler was weighed into a vinyl bag, 15 g of kiln calcined lime was added, and the mixture was sufficiently stirred, and then 125 ml of pure water was sprayed and stirred uniformly. The obtained treated ash was cured for 3 hours and analyzed by the above elution method and measurement method to determine the elution amount of fluorine. The results are shown in Table 2.

Comparative Example 3
500 g of EP ash A from a coal boiler was weighed into a vinyl bag, 15 g of kiln calcined lime was added, and 125 ml of 4 N sulfuric acid was added to the ash as sulfuric acid, and the mixture was uniformly sprayed and stirred. The obtained treated ash was cured for 3 hours and analyzed by the above elution method and measurement method to determine the elution amount of fluorine. The results are shown in Table 2.

Comparative Example 4
Weigh 500g of coal ash EP ash A in a vinyl bag, add 46g of aluminum sulfate 14-18 hydrate as aluminum sulfate to 5 parts by mass, then stir well, then 104ml of pure water Was sprayed and stirred so as to be uniform with a spray. The obtained treated ash was cured for 3 hours and analyzed by the above elution method and measurement method to determine the elution amount of fluorine. The results are shown in Table 2.

Comparative Example 5
After spraying and stirring 125 ml of pure water uniformly on the bug ash B of a coal boiler, curing it for 3 hours, analyzing this untreated ash by the above elution method and measurement method, and determining the elution amount of fluorine. Asked. The results are shown in Table 2.

  As is clear from Table 2, in Examples 1 and 2, the curing is slightly carried out by using either kiln calcined lime and anhydrous aluminum sulfate or 14-18 hydrate and adding water for treatment. In 3 hours, the elution amount of fluorine from the coal boiler EP ash A could be reduced to the standard value of the Soil Contamination Countermeasures Law. Moreover, in Example 3, the amount of fluorine elution could be completely suppressed by further adding alumina cement.

  On the other hand, when only water is added to the coal EP ash A as in Comparative Example 1 without adding calcium compounds or aluminum sulfates, the reference value cannot be cleared even if the amount of fluorine eluted can be slightly reduced. In Comparative Examples 2 and 4, the coal EP ash A is treated by adding kiln calcined lime and water or aluminum sulfate hydrate and water, but the reference value cannot be cleared. Furthermore, in the comparative example 3, although it processes with kiln baking ash and sulfuric acid water, the elution suppression of a fluorine is inadequate.

Further, as shown in the result of Comparative Example 5, coal bug ash B having a high fluorine content and an untreated or water-humidified ash elution amount 1.7 to 1.8 times that of coal EP ash A is also used. As shown in the results of Example 4, by adding kiln calcined lime, aluminum sulfate 14-18 hydrate, water and further alumina cement, elution of fluorine can be suppressed almost completely. It was.
Further, as shown in the results of Example 5, when the combustion ash also contains boron in addition to fluorine, the elution of boron is also suppressed below the reference value by increasing the amount of calcium compound added. I was able to.

  As described above, the treatment method of the present invention can be obtained by adding calcium compound, aluminum sulfate and water to the combustion ash and, if necessary, further adding an alumina cement, and performing a stirring treatment to remove fluorine in the incineration ash. This is a simple method that can suppress the elution amount of boron and the elution amount of boron, and can reduce the elution amount to less than the reference value in both cases, and enables reuse of the fluorine-containing incinerated ash.

  In the method of the present invention, ash discharged from a coal boiler or an RPF boiler using RPF as fuel can be processed in the vicinity of a flue or an outlet, and the obtained processed ash is not solidified. Moreover, the use destination is not limited, and combustion ash that can be effectively used as it is as a soil improvement material, grassland improvement material, backfilling material, embankment and the like can be provided.

Claims (6)

  By adding water to calcium compounds and aluminum sulfates and mixing the fluorine-containing combustion ash obtained by treating the exhaust gas when burning coal, RPF, paper sludge, etc. with an electric dust collector or bag filter, etc. And insolubilizing the fluorine contained in the combustion ash so that the fluorine elution amount is 0.8 mg / L or less when it is eluted by the dissolution test method based on the Environmental Agency Notification No. 18 of 2003. Treatment method for fluorine-containing combustion ash.   Fluorine-containing combustion ash obtained by treating exhaust gas from burning coal, RPF, paper sludge, etc. with an electrostatic precipitator or bag filter, and adding water to calcium compounds, aluminum sulfates, and alumina cement As a result, the fluorine contained in the combustion ash is insolubilized so that the amount of fluorine eluted when it is eluted by the dissolution test method based on Notification No. 18 of the 2003 Environmental Agency is 0.8 mg / L or less. The processing method of the fluorine containing combustion ash which consists of this.   The calcium compound used for the treatment of the burned ash is any one of quick lime, limestone, dolomite, scallop, paper sludge, and calcined lime derived from waste paper straw, or a combination of any ratio thereof. 3. A method for treating fluorine-containing combustion ash according to 2.   4. The fluorine-containing combustion ash according to claim 1, wherein the aluminum sulfate used for the treatment of the combustion ash is selected from anhydrous aluminum sulfate and aluminum sulfate 14-18 hydrate. 5. Processing method.   The fluorine-containing combustion ash according to any one of claims 1 to 4, wherein the calcium compound used for the treatment of the combustion ash is added at a ratio of 5 parts by mass or more with respect to 100 parts by mass of the combustion ash. Processing method. The method for treating fluorine-containing combustion ash according to claim 5, wherein the combustion ash is combustion ash containing boron together with fluorine.