JP2009095754A - Treatment method of boiler ash - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boiler ash treatment agent capable of surely and easily treating harmful substances in boiler ashes for solving the problem that a conventional method cannot simultaneously treat harmful substances in boiler ashes to the environmental standard value or less, therefore complicated procedures are necessary to surely treat the harmful substances, in particular, the harmful substances such as fluorine and the like in the boiler ashes including paper sludge ashes particularly high in the fluorine content are difficult to treat surely, although various methods were proposed heretofore in order to reduces the elution volume of these harmful substances to the environmental standard value or less because harmful substances such as boron, fluorine, selenium, arsenic and the like are included in the boiler ashes. <P>SOLUTION: The treatment method of boiler ash adds an alkaline earth metal phosphoric acid salt and a sulfate to the boiler ashes made of paper sludge as a fuel, and immobilizes fluorine and boron in the boiler ashes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for treating boiler ash.

  Boiler ash discharged from boilers fueled with paper sludge and coal, etc., separated and recovered as solids in waste liquid generated from pulp manufacturing processes, paper manufacturing processes, waste paper processing processes, etc. in paper mills is cement, concrete, Aggregates such as mortar, soil improvement materials, asphalt filler, tiles and tiles, admixtures of marine structures such as tetrapots, golf courses, ground drainage improving materials, water retention block materials, sewage / drainage treatment materials, etc. It is a resource that can be effectively used. However, the boiler ash produced by burning fuels such as coal, paper sludge, and wood chips contains a large amount of various substances such as boron, fluorine, selenium, and arsenic. In recent years, environmental standards have been strengthened in order to regulate. Under these circumstances, arsenic, selenium, fluorine and boron, especially fluorine and boron, are important for treatment. When reusing boiler ash, harmful substances such as boron are not eluted to cause environmental pollution. Need to be processed. In addition, when boiler ash is discarded, it is necessary to treat it so that harmful substances do not elute. As a method for treating harmful substances contained in waste such as boiler ash, lime and gypsum are added to coal ash and kneaded to fix boron in coal ash (Patent Document 1, Patent Document 2). ), A method of insolubilizing fluorine and boron by adding an insolubilizing agent containing calcium aluminate and calcium silicate to coal ash (Patent Document 3), fluorine, arsenic, selenium generated when producing zeolite from coal ash, Add alkaline earth metal salt to alkaline waste liquid containing harmful substances such as boron to precipitate and remove harmful substances (Patent Document 4), add phosphate compound and calcium compound to fluorine-containing solid waste A kneading method (Patent Document 5) and the like have been proposed.

JP-A-11-116292 JP 2004-97944 A JP 2006-224025 A JP 2005-95785 A JP 2002-331272 A

  Boiler ash contains boron, fluorine, etc. as harmful substances that are likely to elute and cause pollution problems. However, even if the methods described in Patent Documents 1 and 2 can fix boron, they can fix fluorine. Noh was inadequate. Moreover, although the method of patent document 3 can fix | immobilize a fluorine and a boron, the high temperature of 850-1450 degreeC is required for preparation of an insolubilizing agent, and there exists a problem of becoming high cost. The method described in Patent Document 4 can remove and purify harmful substances such as fluorine and arsenic at the same time. A wastewater treatment method that occurs during reuse, and when it is applied to prevent the release of harmful substances from solid coal ash, even though the harmful substances in the wastewater can be below the wastewater standard Therefore, it was difficult to make the amount of harmful substances eluted from coal ash below the environmental standard. Furthermore, even if a large amount of chemicals was used and the amount of harmful substances eluted could be below the environmental standard value, the ability to immobilize harmful substances was insufficient, and there was a problem that harmful substances were eluted over time. Fluorine contained in boiler ash is in the form of hydrogen fluoride by combustion of fluorine contained in fuels such as paper sludge and coal. Hydrogen fluoride is in comparison with fluorine contained in soil. It is easy to elute, and since the paper sludge ash contains a large amount of fluorine, it is difficult to reliably treat the fluorine in the boiler ash containing the paper sludge ash even by the method described in Reference 5. .

On the other hand, as a conventional wastewater treatment method, a calcium fluoride coprecipitation method or a hydroxide coprecipitation method is known for fluorine. In fact, a fluorine two-stage precipitation treatment method combining these two methods, etc. The advanced processing method is a common method. In this method, a calcium salt such as slaked lime (calcium hydroxide) or calcium chloride is added as the first stage to produce and remove poorly soluble calcium fluoride, and an aluminum salt is added as the second stage. Thus, aluminum hydroxide is produced, and fluorine ions are adsorbed and co-precipitated on the floc. The advanced treatment method can reduce the fluorine in the wastewater below the wastewater standard value, but it is difficult to make it below the environmental standard value. As another advanced treatment, there is a method in which phosphoric acid is added to the wastewater and the pH is adjusted to 12 with slaked lime to treat the fluorine to 5 mg / L or less, but a large amount of phosphoric acid needs to be supplied, and excessively It is necessary to treat the added excess phosphoric acid separately after the fluorine treatment, and there is a problem that it is wasteful and impractical.
Boron can be effectively treated by the combined use of slaked lime and aluminum salt as described above, but when fluorine is present in the wastewater, it becomes fluoroboron, and boron that has become fluoroboron is removed by ordinary coagulation precipitation. Although it has been reported that a method of adding a calcium salt to the regenerated waste liquid removed by the ion exchange treatment and concentrating it to perform thermal decomposition, there are problems such as high processing costs. Moreover, none of the above methods alone can treat boron and fluorine at the same time, and complicated treatments such as a combination of various methods are necessary. Furthermore, even if it is applied to prevent the elution of harmful substances such as fluorine and boron from solid boiler ash, the harmful substances contained in solid waste such as boiler ash are gradually eluted over a long period of time. There was a fear. The present invention has been made in view of the above problems, and can reliably fix harmful substances such as boron and fluorine in boiler ash containing paper sludge in the fuel, safely and effectively use boiler ash, landfill, etc. It aims at providing the processing method of boiler ash which makes it possible to dispose of safely.

That is, the present invention
(1) Treatment of boiler ash characterized by adding alkaline earth metal phosphate and sulfate to boiler ash containing paper sludge in the fuel to fix fluorine and boron in the boiler ash Method,
(2) The boiler ash treatment method according to (1), wherein the sulfate is one or more selected from ferrous sulfate, ferric sulfate, magnesium sulfate, and aluminum sulfate,
(3) The above (1) or (2), wherein 0.1 to 30 parts by weight of alkaline earth metal phosphate and 0.1 to 30 parts by weight of sulfate are added to 100 parts by weight of boiler ash. Boiler ash treatment method,
Is the gist.

  The method for treating boiler ash of the present invention can simultaneously and reliably fix harmful substances such as fluorine and boron in boiler ash containing a large amount of fluorine containing paper sludge in the fuel. From the boiler ash of these harmful substances, The boiler ash treated by the method of the present invention can be safely treated so that the amount of elution of the water is equal to or less than the environmental standard value. It can be safely and effectively used as a ground drainage improver, water retention block material, sewage / drainage treatment material, and can be safely disposed of even when discarded without being reused.

  In the present invention, the alkaline earth metal phosphate includes calcium monohydrogen phosphate, calcium dihydrogen phosphate, calcium phosphate, magnesium monohydrogen phosphate, magnesium dihydrogen phosphate, magnesium phosphate, barium monohydrogen phosphate, Barium dihydrogen phosphate, barium phosphate, beryllium phosphate phosphate, beryllium phosphate phosphate, beryllium phosphate, strontium phosphate phosphate, strontium phosphate phosphate, strontium phosphate, radium phosphate phosphate, phosphate Examples thereof include radium dihydrogen and radium phosphate, and calcium monohydrogen phosphate, calcium dihydrogen phosphate, and calcium phosphate are preferable. These alkaline earth metal phosphates can be used alone or in combination of two or more. Also, as sulfates, ferrous sulfate, ferric sulfate, lithium sulfate, sodium sulfate, potassium sulfate, rubidium sulfate, cesium sulfate, francium sulfate, beryllium sulfate, magnesium sulfate, calcium sulfate, barium sulfate, strontium sulfate, sulfuric acid Radium, aluminum sulfate, ammonium sulfate, ammonium hydrogen sulfate, ammonium iron sulfate (II), ammonium iron sulfate (III), ammonium magnesium sulfate, aluminum ammonium sulfate, indium sulfate, potassium aluminum sulfate, sodium aluminum sulfate, potassium hydrogen sulfate, sodium hydrogen sulfate, titanium sulfate Zirconium sulfate, manganese sulfate, silver sulfate, thallium sulfate and the like are mentioned, and ferrous sulfate, ferric sulfate, magnesium sulfate and aluminum sulfate are preferable. One or more of the above sulfates can also be selected and used.

  The amount of alkaline earth metal phosphate and sulfate added to the boiler ash is 0.1 to 30 parts by weight of alkaline earth metal phosphate and 0.1 to 30 parts by weight per 100 parts by weight of boiler ash. Part is preferable, but 0.1 to 10 parts by weight of alkaline earth metal phosphate and 0.1 to 10 parts by weight of sulfate are particularly preferable. If the addition amount of alkaline earth metal phosphate is less than 0.1 parts by weight per 100 parts by weight of boiler ash, there is a possibility that the fixation of fluorine will be insufficient, and an amount exceeding 30 parts by weight is added. However, it is not economical because there is no significant change in effect. On the other hand, if the amount of sulfate added is less than 0.1 parts by weight per 100 parts by weight of boiler ash, both fluorine and boron may be insufficiently immobilized, and if it exceeds 30 parts by weight, the pH will be too low. As a result, boron may be eluted. The alkaline earth metal phosphate and sulfate may be added separately to the boiler ash, or both may be mixed and added to the boiler ash. The amount of alkaline earth metal phosphate and sulfate added should be fixed according to the properties of the boiler ash, such as the difference in the content of each harmful substance in the boiler ash, to ensure that the harmful substances are fixed. Can be economically effective. For example, when the fluorine content in boiler ash is high, the proportion of alkaline earth metal phosphate is increased, and when the pH of the eluate is high or the boron content is low, the amount of sulfate added It is preferable to adjust the amount of addition, such as increasing the amount. Further, when fixing harmful substances in boiler ash, the optimum treatment pH differs depending on the kind of the harmful substance, the treatment appropriate pH of fluorine is 8 or more, and the treatment appropriate pH of boron is 11 or more. For this reason, in order to fix a harmful substance effectively, it is preferable to adjust and process the pH of boiler ash to 11 or more. In order to adjust the pH at the time of treating boiler ash to 11 or more, it is usually necessary to add alkaline earth metal hydroxide, but it is optimal depending on the content and elution amount of each toxic substance. It is preferable to adjust the pH (confirmed by the Environmental Agency Notification No. 46 test method). In addition, it can be said that there is a general correlation between the content of harmful substances in boiler ash and the elution amount. In some cases, it is important to check both the content and the elution amount.

  Boiler ash using coal or paper sludge that does not contain heavy metals as fuel contains almost no heavy metals, even if it contains harmful substances such as selenium, arsenic, boron, and fluorine. However, since boiler ash that uses heavy metals such as biomass and building waste as fuel contains heavy metals, it is necessary in the case of boiler ash that contains fuel other than coal together with paper sludge. Accordingly, it is preferable to further use a metal fixing agent in combination because it is possible to prevent elution of heavy metals from the boiler ash. Any metal fixing agent may be used as long as it can form an insoluble compound with the heavy metal in the boiler ash. The amount of the metal fixing agent added is usually 0.1 to 10 parts by weight per 100 parts by weight of the boiler ash, although it depends on the amount of heavy metals contained in the boiler ash.

  Examples of the metal fixing agent include compounds having functional groups such as dithiocarbamic acid group, phosphoric acid group, carboxylic acid group, carbamic acid group, dithioic acid group, aminophosphoric acid group, thiol group, and xanthate group. The metal immobilizing agent used in the present invention may have the same functional group or may have two or more different functional groups. In addition, two or more kinds of metal fixing agents having different functional groups can be mixed and used, but the metal fixing agent preferably has water solubility and water dispersibility. Examples of the compound having a dithiocarbamic acid group include compounds obtained by reacting carbon disulfide with amines such as monoamines and polyamines.

  In the compound having a dithiocarbamic acid group as a functional group, the dithiocarbamic acid group may be an acid type (terminal is a hydrogen atom), a salt type, or a compound containing both. Examples of the salt-type dithiocarbamic acid group include barium salt, sodium salt, potassium salt, calcium salt, magnesium salt, amine salt and the like, but sodium salt and potassium salt are usually preferable. A compound having a dithiocarbamic acid group as a functional group includes a compound having both an acid type and a salt type dithiocarbamic acid group, a compound having only an acid type dithiocarbamic acid group, and a salt type dithiocarbamic acid group only. One or a mixture of two or more compounds can be used.

  Examples of the compound having a phosphate group as a functional group include compounds having a phosphate group obtained by reacting the same amines as described above with aldehydes and phosphorous acid. In the compound having a phosphoric acid group as a functional group, the phosphoric acid group may be an acid type (terminal is a hydrogen atom), a salt type, or a compound containing both. Examples of the salt-type phosphate group include barium salt, sodium salt, potassium salt, calcium salt, magnesium salt, and amine salt, and sodium salt and potassium salt are usually preferable. As a compound having a phosphate group as a functional group, a compound having both an acid type and a salt type phosphate group in one molecule, a compound having only an acid type phosphate group, and a salt type phosphate group only. One kind or a mixture of two or more kinds of the compounds having them can be used.

  Examples of the compound having a carboxylic acid group as a functional group include compounds having a carboxylic acid group obtained by reacting the same amines as described above with a monohalogenated carboxylic acid or an ester thereof. In the compound having a carboxylic acid group as a functional group, the carboxylic acid group may be an acid type (terminal hydrogen atom), a salt type, or a compound containing both. Examples of the salt-type carboxylic acid group include barium salts, sodium salts, potassium salts, calcium salts, magnesium salts, and amine salts, but sodium salts and potassium salts are usually preferable. As a compound having a carboxylic acid group as a functional group, a compound having both an acid type and a salt type carboxylic acid group in one molecule, a compound having only an acid type carboxylic acid group, and a salt type carboxylic acid group only. One kind or a mixture of two or more kinds of the compounds having them can be used.

  A commercially available metal collector may be used as the metal collector, and examples of commercially available metal collectors include Ashclean C-500, Ashclean C-508, and Ashclean C-505 (stocks). Ebara Manufacturing Co., Ltd.), Ash Knight S-803 (Kurita Industry Co., Ltd.), TX-10, TS-500, TS-600, TS-800, (Tosoh Corporation), Alcite L-105 (Fuji Sash Corporation) ), Koei Chelate 200 (Lasa Soei Co., Ltd.), Ash Ace L-5000 (Hitachi Shipbuilding Co., Ltd.), UML-7200, UML-8100, UML-8100A (Unitika Ltd.), ALM-648HG, Heidion-VG ( Nippon Soda Co., Ltd.), Epoflock series (Epofuloc L-1 and Epofloc L-2) manufactured by Miyoshi Oil & Fat Co., Ltd. ), Epo Luba series (NEW Eporuba 800, NEW Eporuba 800A, NEW Eporuba 810, etc.), include the Epoasshu M-1 and the like.

  As boiler ash to be treated in the method of the present invention, for example, boiler ash fueled with paper sludge, which is fiber residue generated in the paper manufacturing process, and paper sludge together with coal, wood chips, livestock waste, food waste, construction Generated wood, lumber mill residue, black liquor (pulp mill waste liquid), sewage sludge, human waste sludge, rice straw, wheat straw, rice husk, forest land residues (thinned wood, damaged trees, etc.), sugar systems such as sugar cane and corn Although boiler ash using biomass, such as oil crops, such as crops and rapeseed, as a fuel is mentioned, it is especially suitable for processing of boiler ash containing 100 mg / kg or more of fluorine and boron.

Hereinafter, the present invention will be described in more detail with reference to examples.
Examples 1-6, Comparative Examples 1-6
20% by weight of water is added to 100 g of boiler ash having a pH of 11.6 (according to the Environmental Agency Notification No. 46 test method) containing 130 mg / kg of boron and 880 mg / kg of fluorine as harmful substances. And kneaded for 5 minutes. About the boiler ash after a process, and the unprocessed boiler ash, the elution density | concentration of a hazardous | toxic substance was measured according to the Environmental Agency Notification No.46 test. Table 2 shows the results of the toxic substance elution test from the boiler ash immediately after the treatment with the chemical mixed with the boiler ash. Table 3 shows the results of the dissolution test after 7 days of treatment.

(Table 1)

(Table 2)

(Table 3)

Claims (3)

A method for treating boiler ash, comprising adding alkaline earth metal phosphate and sulfate to boiler ash containing paper sludge in fuel to fix fluorine and boron in the boiler ash. The method for treating boiler ash according to claim 1, wherein the sulfate is one or more selected from ferrous sulfate, ferric sulfate, magnesium sulfate, and aluminum sulfate. The treatment of boiler ash according to claim 1 or 2, wherein 0.1 to 30 parts by weight of alkaline earth metal phosphate and 0.1 to 30 parts by weight of sulfate are added to 100 parts by weight of boiler ash. Method.