JP2014083491A - Processing method for combustion ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating the paper sludge combustion ash containing harmful substances effectively and conveniently.SOLUTION: Combustion ash is treated to attain a product by adding 0.01 to 2 pts.wt. of sulfite salt to 100 pts.wt. of combustion ash containing paper sludge combustion ash having a particle size adjusted within 10 to 300 μm. This product is suppressed in the elution of noxious components so that the product can be effective in applications of an absorber, a soil improvement material, a roadbed material, a forest work and a road improvement material, and the like.

Description

  The present invention relates to a method for treating combustion ash including paper sludge combustion ash. In particular, by applying the treatment method of the present invention, inorganic harmful components such as fluorine and hexavalent chromium can be prevented from eluting from the combustion ash, and at the same time, the combustion ash can be prevented from scattering. In addition, according to the present invention, a treated product in which the water absorption of the combustion ash that is the object to be treated is maintained can be obtained, so that the treated product can be used as a soil improving material, a water absorbing material, or the like having high water absorption.

  In recent years, reduction of industrial waste has been strongly demanded from the viewpoint of environmental conservation. The reduction of industrial waste is a request to all companies and local governments that are engaged in power generation and waste incineration, and the paper and pulp industry is no exception.

  Under such circumstances, handling of combustion ash is a big social problem. Currently, a part of the combustion ash is effectively used as a recycled material such as a cement raw material, an iron-making antioxidant and an admixture, but the rest is often landfilled as industrial waste. Combustion ash is one of the reasons for not reusing the soil environment in accordance with the provisions of Article 5, Paragraph 4, Item 4 of the Ordinance for Enforcement of the Soil Contamination Countermeasures Law (Ministry of Environment Ordinance No. 29, 2004). In many cases, the elution amount of harmful components listed in the standards (Ministry of the Environment Notification No. 18 and Amended Ministry of the Environment Notification No. 48) exceeds the standard value. Of the above harmful components, organic harmful components are decomposed during incineration, so combustion ash is not a problem in most cases, but the amount of elution of inorganic harmful components such as fluorine, boron, hexavalent chromium and lead is Often the standard is exceeded. If the leaching amount of harmful components exceeds the soil environment standard value, the combustion ash cannot be applied to the soil, which is a big barrier to reuse.

  Further, in most cases, the combustion ash is a fine solid powder and requires attention as dust when handled. When discharging or transporting, it is common to add moisture to the combustion ash to prevent dust scattering, but if the combustion ash with added moisture is left in the air, the added moisture Reacts with the calcium content in the combustion ash to form calcium hydroxide, and this calcium hydroxide reacts with carbon dioxide in the atmosphere to form calcium carbonate. The elution amount of hexavalent chromium increases. In addition, since the water absorption of combustion ash is reduced due to the addition of a large amount of water, there is also a problem that the performance of the reused product is reduced when it is reused as a water absorbent product utilizing the excellent water absorption of combustion ash. .

  In order to satisfy the soil environmental standards stipulated in the Soil Contamination Countermeasures Law, a number of technologies have been studied and patent applications have been made to reduce the leaching amount of harmful components by adding some insolubilizing agent to contaminated materials. Yes. Patent Document 1 discloses a method for treating contaminated soil by contacting hexavalent chromium-contaminated soil with polyphenol and phosphoric acid or phosphate. Patent Document 2 discloses a method for purifying contamination caused by a chemical substance, characterized by adding a reducing agent after adding a persulfate as an oxidizing agent to a contaminant containing an organic chlorine compound and containing heavy metals. Has been. Patent Document 3 discloses a method for suppressing the elution amount of fluorine and boron by adding calcium oxide, blast furnace cement, and aluminum sulfate in the presence of water to combustion ash containing fluorine and boron and mixing the mixture. Is disclosed.

Japanese Patent Application Laid-Open No. 10-85716 JP 2004-337777 A (Patent No. 4095490) JP 2006-181535 A

  The main subject of this invention is providing the method of processing the paper sludge combustion ash containing a harmful substance effectively and simply. In particular, by reducing the elution amount of inorganic harmful components such as fluorine and hexavalent chromium contained in paper sludge combustion ash, and at the same time, processing so as not to impair the water absorption of the object to be treated, the treated material has high water absorption. Another object of the present invention is to obtain a treated product with added value that can be used as a water-absorbing material having a property.

  The present invention is a method for treating combustion ash, which includes adding sulfite after adjusting the particle size of combustion ash containing paper sludge combustion ash to a range of 10 to 300 μm.

  The present invention provides a method for efficiently and simply treating paper sludge combustion ash, which is a waste containing hazardous substances. In particular, according to the present invention, elution of inorganic harmful components such as fluorine and hexavalent chromium contained in the paper sludge combustion ash can be suppressed. Moreover, according to this invention, the processed material with added value which can be utilized also as a water absorbing material etc. can be manufactured by using combustion ash as a raw material. In the present invention, it is possible to complete the treatment of the paper sludge combustion ash by a relatively simple process in which only a chemical is added without requiring a special device or equipment.

  In the present invention, the paper sludge is also called paper sludge and means waste generated from a pulp manufacturing process, a paper manufacturing process, a used paper processing process, and the like. Paper sludge contains organic substances such as pulp, ink, and papermaking chemicals in addition to inorganic substances such as silica, calcium carbonate, cinnabar, talc and kaolin used in papermaking as pigments and fillers.

  In the present invention, paper sludge combustion ash refers to combustion ash generated when paper sludge is burned by a combustion device.

  In the present invention, the type of the combustion apparatus is not particularly limited, and a known apparatus can be used. For example, a known incinerator such as a fluidized bed boiler or a stoker combustion furnace can be used.

  Moreover, in order to use for auxiliary combustion, fuels such as heavy oil and coal may be mixed with paper sludge. Furthermore, RDF (garbage solid fuel), RPF (industrial waste plastic / waste paper solid fuel), and other general combustible materials may be co-fired in a boiler together with paper sludge.

  The temperature at which the above combustion treatment is performed can be arbitrarily determined by those skilled in the art, preferably in the range of 500 to 1500 ° C, more preferably in the range of 600 to 1200 ° C, and most preferably in the range of 700 to 1000 ° C. Moreover, the time of the said combustion process can also be selected suitably, The average residence time of the raw material in a combustion apparatus has preferable within 1 hour, More preferably within 3-30 minutes, More preferably within 10 minutes.

  In the present invention, in addition to paper sludge combustion ash, coal ash and biomass combustion ash may be further mixed and used. 0-100 mass parts is preferable with respect to 100 mass parts of paper sludge combustion ash, and, as for the mixing ratio of coal ash and biomass combustion ash, 0-50 mass parts is more preferable.

  In the present invention, the combustion ash obtained in this way can be subjected to some kind of treatment before the chemical addition described below. For example, insofar as the object of the present invention is not impaired, pretreatment such as crushing, crushing, crushing, classification, reburning, redrying, magnetic sorting, etc. is performed using any suitable apparatus well known to those skilled in the art. Can also be done. Alternatively, the combustion ash that has been subjected to the combustion treatment can be directly used in the present invention without performing any pretreatment, and it is preferable not to perform the pretreatment from the viewpoint of energy consumption and cost.

  In the present invention, the particle size of the combustion ash is 10 to 300 μm, preferably 150 to 250 μm, and more preferably 150 to 250 μm. As the particle size of the combustion ash increases, the specific surface area decreases, and as a result, the amount of fluorine and boron eluted decreases. However, if the particle size of the combustion ash exceeds 300 μm, the strength decreases, which is not preferable for applications such as roadbed materials and forest road improvement materials.

  In the present invention, the apparatus for adjusting the particle size of the combustion ash includes a vibrating sieve, an ultrasonic sieve, a jet screen, an air separator, a trommel screen, a cyclone type wind classifier, and the like. Specific examples include a wind classifier (micron separator, manufactured by Hosokawa Micron Corporation), and a semi-free vortex centrifugal classifier (eddy classifier, manufactured by Nisshin Engineering Co., Ltd.).

  In the present invention, sulfite is preferably added. The elution amount of hexavalent chromium can be suppressed by adding sulfite. Examples of the sulfite include sodium sulfite and potassium sulfite. It is necessary to add 0.01 to 5 parts by mass of sulfite to 100 parts by mass of combustion ash, and it is more preferable to add 0.1 to 1 part by mass. When the addition amount is less than 0.01 parts by mass, the suppression of the elution amount of hexavalent chromium is insufficient, and even if the addition amount exceeds 5 parts by mass, the effect is not improved. By adding sulfite, it is considered that hexavalent chromium is reduced to harmless trivalent chromium and the elution amount of hexavalent chromium is reduced.

  In the present invention, the above raw materials are kneaded to produce a processed product. The kneading time is also affected by the mixing device (such as the rotation speed and size of the stirrer), and thus is suitably adjusted, but is preferably 1 to 30 minutes, and more preferably 5 to 10 minutes. The mixing apparatus for kneading is not particularly limited, and the raw material can be kneaded by an apparatus equipped with a kneading roll and a kneading blade, but a rolling kneader is most suitable for efficient kneading. Examples of suitable kneaders include ELBA mixers (manufactured by Kurihara), intensive mixers (manufactured by Eirich), and Pelegaia (manufactured by Kitagawa Iron Works).

  In the present invention, raw materials such as paper sludge combustion ash and sulfite may be supplied separately to the kneader, or may be supplied in a premixed state.

  In the present invention, it is not always necessary to add water to the combustion ash. When water is added to prevent scattering, the amount is preferably 30 parts by weight or less with respect to 100 parts by weight of combustion ash. If the amount exceeds 30 parts by weight, the combustion ash itself contains a large amount of water, and the water absorption of the incinerated ash is lost, making it difficult to use the obtained processed product as a water absorbent. There is. Further, combustion ash to which a large amount of moisture is added tends to increase the elution amount of hexavalent chromium.

  The treated product obtained by the present invention has good water absorption and is useful per se. The treated product of the present invention can be particularly suitably used for applications such as an absorbent material, a soil improvement material, a roadbed material, and a forest work road improvement material, taking advantage of its water absorption and water retention. According to the present invention, a useful material can be produced using combustion ash, which is waste, as a raw material, which is preferable from the viewpoint of waste reduction and global environmental conservation.

  Examples of the present invention will be specifically described below in comparison with comparative examples, but the present invention is not limited to these examples.

In the description, “%” and “part” indicate “% by mass” and “part by mass” unless otherwise specified. Moreover, about the material addition rate, when there is no designation | designated, the addition rate of an active ingredient is shown.
(A) Fluorine (F), boron (B), hexavalent chromium (Cr (VI), total chromium (total Cr), lead (Pb) elution method: performed in accordance with 2003 Ministry of the Environment Notification No. 18 That is, after the sample was crushed into granular products, 50 g of a non-metallic sieve having a mesh opening of 2 mm was passed into a 1000 ml polyethylene container with a lid, and purified water (pH 5.8 to 6.3) was obtained. The sample solution was shaken continuously for 6 hours at room temperature and atmospheric pressure using an elution shaker (shaking width: 4 to 5 cm, frequency: 200 times). The sample solution after shaking was allowed to stand for 30 minutes, and then centrifuged at about 3000 rpm for 20 minutes, and the supernatant was filtered through a membrane filter having a pore size of 0.45 μm. Measure accurately the amount required for quantification, It was used as a test liquid. Incidentally, elution reference the following fluorine 0.8 mg / L, or less boron 1 mg / L, hexavalent chromium 0.05 mg / L or less, or less lead 0.01 mg / L.
(B) Method for measuring fluorine elution amount: The above test solution was analyzed by ion chromatography, and the amount of eluted fluorine was quantified (34.2 of JIS K 0102).
(C) Measuring method for elution amount of boron, hexavalent chromium, total chromium and lead: Analyze the above test solution by diphenylcarbazide absorptiometry and quantify the amount of eluted boron, hexavalent chromium, total chromium and lead (JIS K 0102 65.2.1).
(D) pH of eluate: according to “pH test method for soil suspension” (Geotechnical Society standard, JGS 0211-2000) It was measured.

[Example 1]
Burning waste (mainly referred to as “paper sludge”) consisting mainly of deinked floss and run-off fibers in a paper mill in a fluidized bed furnace for paper sludge at a combustion temperature of 850 ° C. and an average residence time of less than 10 seconds I let you. This combustion is intended to reduce the volume of waste and recover steam and thermal energy.
The obtained combustion residue (combustion ash) collects a large particle size portion by a cyclone treatment, and then collects a small particle size portion in a bag filter. The combustion ash finally transferred into the storage silo was taken out and subjected to the following treatment.
0.25 part of sodium sulfite was added to 100 parts of combustion ash having an average particle diameter of 206.4 μm treated with cyclone, and the mixture was stirred and mixed for 3 minutes using a mixer. The ash after the treatment was subjected to a dissolution test in accordance with 2003 Ministry of the Environment Notification No.18. The pH of the eluate is 12.0, the elution amount of fluorine is 0.55 mg / L, the elution amount of hexavalent chromium is 0.018 mg / L, and the elution amounts of other elements are the environmental standard values of the Soil Contamination Countermeasures Law. It was the following.

[Example 2]
The treatment was performed in the same manner as in Example 1 except that 0.5 part of sodium sulfite was added to 100 parts of combustion ash. The ash after the treatment was subjected to a dissolution test in accordance with 2003 Ministry of the Environment Notification No.18. The pH of the eluate is 12.0, the elution amount of fluorine is 0.54 mg / L, the elution amount of hexavalent chromium is 0.03 mg / L, and the elution amount of other elements is also the environmental standard value of the soil pollution countermeasures law. It was the following.

[Comparative Example 1]
The treatment was performed in the same manner as in Example 1 except that 0.1 part of sodium sulfite was added to 100 parts of combustion ash. The ash after the treatment was subjected to a dissolution test in accordance with 2003 Ministry of the Environment Notification No.18. The pH of the eluate was 11.9, the elution amount of fluorine was 0.50 mg / L, and the elution amount of hexavalent chromium was 0.053 mg / L. The amount of elution of other elements was below the environmental standard value of the Soil Contamination Countermeasures Law.

[Comparative Example 2]
The treatment was performed in the same manner as in Example 1 except that sodium sulfite was not added. The ash after the treatment was subjected to a dissolution test in accordance with 2003 Ministry of the Environment Notification No.18. The pH of the eluate was 12.0, the elution amount of fluorine was 0.27 mg / L, and the elution amount of hexavalent chromium was 0.079 mg / L. The amount of elution of other elements was below the environmental standard value of the Soil Contamination Countermeasures Law.

[Comparative Example 3]
The ash of combustion ash with an average particle size of 6.2 μm collected by the bag filter was subjected to an elution test in accordance with Notification No. 18 of the Ministry of the Environment in 2003. The pH of the eluate was 11.1, the elution amount of fluorine was 2.24 mg / L, the elution amount of boron was 1.12 mg / L, and the elution amount of hexavalent chromium was 0.060 mg / L. The amount of elution of other elements was below the environmental standard value of the Soil Contamination Countermeasures Law.

  As is clear from a comparison of Examples 1 and 2 and Comparative Examples 1 to 3, the treated product obtained from the incinerated ash according to the present invention was difficult to elute harmful substances. In other words, an appropriate amount of sulfite is added to and mixed with incinerated ash containing fluorine and hexavalent chromium after cyclone treatment, so that fluorine from the incinerated ash by an elution test based on Notification No. 18 of the Ministry of the Environment in 2003 can be obtained. The elution amount can be less than 0.8 mg / L, and the elution amount of hexavalent chromium can be less than 0.05 mg / L. As a result, the amount of elution of all environmental impact elements from the incineration ash can be reduced below the environmental standard value of the Soil Contamination Countermeasures Law, and incineration ash containing fluorine and hexavalent chromium can be safely used in the soil field. It was.

Claims (4)

  A method for treating combustion ash, comprising adjusting the particle size of combustion ash containing paper sludge combustion ash to a range of 10 to 300 μm and then adding sulfite.   The processing method of the combustion ash of Claim 1 which adds a sulfite in the range of 0.01-5 mass parts with respect to 100 mass parts of combustion ash containing paper sludge combustion ash.   The processing method of the combustion ash in any one of Claims 1-2 in which the said combustion ash contains 0-50 weight part of coal ash with respect to 100 mass parts of paper sludge combustion ash.   The processing method of the combustion ash in any one of Claims 1-3 including adjusting the particle size of the combustion ash containing paper sludge combustion ash to the range of 10-300 micrometers by performing a cyclone process.