JP2001221421A - Method for treating ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating ash in which metal scavenger is added to the ash to fix poisonous metal, such as heavy metal or the like, and with which metal can be surely and firmly fixed without an addition of a large amount of metal scavenger in a condition where metal salt, such as calcium salt, sodium, potassium salt or the like is contained in the ash, and thus treating costs of the ash can be remarkably reduced. SOLUTION: The method is characterized by comprising washing the ash containing metal with water, filtering the washed ash, adding the metal scavenger to metal residuum resulted from the filteration, and fixing the metal in the residuum by the metal scavenger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to incineration ash remaining as incineration residue in incinerators, fly ash separated and removed from smoke exhaust, or incineration when waste is incinerated in a garbage incineration plant or the like. Effectively fix metal contained in ash such as molten fly ash separated from waste gas generated when heat and melting incinerated ash or fly ash to reduce the volume of ash or fly ash The present invention relates to a method of treating ash that can be performed.

[0002]

2. Description of the Related Art In recent years, with the diversification of types of refuse, incineration ash and fly ash generated in refuse incineration plants and the like, and melting and fly ash generated in a processing step of reducing the volume by heating and melting these incineration ash and fly ash. Various metals are contained in ash such as ash, and heavy metals harmful to the human body such as mercury, cadmium, lead, and chromium may be contained in many cases. When such harmful heavy metals flow out of the ash into groundwater, rivers, seawater, lakes and marshes, serious environmental pollution problems may occur.

[0003] For this reason, incineration ash generated in garbage incineration plants and the like,
Conventionally, when processing fly ash, molten fly ash, etc., a method of solidifying it with cement and then reclaiming it or dumping it in the ocean has been adopted.However, there is a possibility that metal may flow out through the cement wall. A method of fixing metals in ash with a metal scavenger before they are dumped into the sea or into the ocean has been adopted. Examples of such a metal collecting agent include, as previously proposed by the present applicant, dithioic acid groups and dithioic acid bases at nitrogen atoms of polyalkylene polyamines such as ethylenediamine and triethylenetetramine and polyamines such as polyethyleneimine. Are known (for example, Japanese Patent Publication No. 5-7079, Japanese Patent Publication No. 5-7080).

[0004]

In recent years, with the increase of plastic waste, a large amount of chlorine gas may be generated when garbage is incinerated at a garbage incineration plant. A method of collecting chlorine gas generated by spraying is generally used. For this reason, fly ash contains a large amount of calcium salt. In addition, since various kinds of acidic substances and alkali substances are contained in recent waste, in addition to the above-mentioned calcium salts, metal salts such as sodium salts and potassium salts also exist in incinerated ash and fly ash. May be included.

According to studies by the present inventors, in the case of incinerated ash or fly ash containing metal salts such as calcium salts, sodium salts, and potassium salts, a treatment for immobilizing metals by adding a metal collecting agent is performed. Even when the ash was applied, it was found that if the treated ash was exposed to rain or the like, the metal fixed by the metal trapping agent might be eluted from the ash. The higher the concentration of the metal salt such as a calcium salt, a sodium salt, and a potassium salt, the more the metal collecting agent is not added (for example, the metal collecting agent required to collect the metal contained in the ash). It was found that elution of the metal could not be prevented. Furthermore, when incinerated ash and fly ash containing sodium salts and potassium salts are heated and melted, the molten fly ash separated from the waste gas generated during this treatment contains sodium in the original incinerated ash and fly ash. Sodium and potassium salts are contained at a higher concentration than the concentration of salts and potassium salts, and in order to surely fix the metal in such molten fly ash with a metal collecting agent,
It was also found that it was necessary to add a large amount of a metal collecting agent. Originally, in the case of a method in which metals contained in solid waste such as ash are fixed by a metal collecting agent, the metal collecting agent to be added is a method of collecting and removing metals in waste water by using a metal collecting agent. Since a much larger amount is required than the amount of the metal trapping agent used in the above, a larger amount of the metal trapping agent is contained by containing a metal salt such as a calcium salt, a sodium salt, and a potassium salt in the ash. The need to add agents
There was a major problem that the processing cost of ash became extremely high.

The present inventors have conducted intensive studies to solve such a problem. As a result, the ash was washed with water and filtered before adding the metal collecting agent, and then the metal collecting agent was added to the filtration residue. By adopting the method, it has been found that the metal contained in the ash can be reliably immobilized even by adding a small amount of the metal collecting agent, and the present invention has been completed.

[0007]

In other words, the method for treating ash according to the present invention comprises washing and filtering ash containing metal, adding a metal collecting agent to the filtration residue, and converting the metal in the residue to metal. It is characterized by being immobilized by a collecting agent. The present invention also provides a method for washing a metal-containing ash with water, filtering the ash, adding a metal collecting agent to the filtrate, collecting and removing the metal eluted in the filtrate by the metal collecting agent, and collecting the metal in the filtration residue. It is characterized in that a collecting agent is added, and the metal in the residue is fixed by the metal collecting agent. The method of the present invention is particularly effective for treating molten fly ash.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Ash used in the method of the present invention is incinerated ash remaining as incineration residue in an incinerator when waste is incinerated in a garbage incineration plant, etc. In order to reduce the volume of separated fly ash, incinerated ash and fly ash, molten fly ash separated from waste gas generated when heat-melting incinerated ash and fly ash, or a mixture thereof is mentioned. Can be The method of the present invention is particularly suitable as a method for treating molten fly ash in which the concentration of sodium salt or potassium salt contained in incinerated ash or fly ash is higher than the concentration in the original incinerated ash or fly ash. is there.

In the method of the present invention, first, ash such as incinerated ash, fly ash, molten fly ash and the like generated in a garbage incineration plant is washed with water.
The rinsing process is a process raw material ash (hereinafter referred to as raw ash) 10.
This is performed using at least 50 parts by weight of cold water, hot water and steam per 0 parts by weight. The washing is performed for a time sufficient to dissolve the metal salt contained in the raw ash, usually for several minutes to several hours. As a cleaning method, a batch-type cleaning method or a continuous-type cleaning method such as a water passing method is employed.

Next, the ash washed with water is filtered, and a metal collecting agent is added to the filtration residue (the ash after washing may be hereinafter referred to as filtration residue) to collect the metal in the filtration residue. Immobilize with agent.

As the above-mentioned metal collecting agent, a compound having a group having a complex forming ability with respect to a metal, for example, a group having an atom having a coordinating ability with respect to a metal such as an oxygen atom, a nitrogen atom and a sulfur atom is used. For example, compounds having a functional group such as a phosphoric acid group, a carboxylic acid group, a carbamic acid group, a dithiocarbamic acid group, and the like can be given. As the metal collecting agent, those having water solubility and water dispersibility are preferable, and a compound having a dithiocarbamic acid group is particularly preferable because of its excellent ability to collect heavy metals such as mercury.

Examples of the compound having a dithiocarbamic acid group include compounds obtained by reacting amines such as monoamine and polyamine with carbon disulfide. Examples of the monoamine include monomethylamine, dimethylamine, monoethylamine, diethylamine, monopropylamine, dipropylamine, monobutylamine, dibutylamine, isopropylamine, diisopropylamine, piperidine, piperazine, morpholine, methylphenylamine, and ethylphenylamine. Is mentioned. As the polyamine, for example, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenediamine, dibutylenetriamine, triethylenetetramine,
Tripropylenetetramine, tribubutylenetetramine,
Aliphatic polyamines such as tetraethylenepentamine, tetrapropylenepentamine, tetrabutylenepentamine, pentaethylenehexamine, iminobispropylamine, monomethylaminopropylamine, and methyliminobispropylamine; 1,3-bis (aminomethyl) cyclohexane Cycloamines such as 1-aminoethylpiperazine and piperazine; polymers of cyclic imines such as polyethyleneimine, polypropyleneimine, poly-3-methylpropylimine and poly-2-ethylpropylimine; polyvinylamine And polymers of unsaturated amines such as polyallylamine. In addition, unsaturated amines such as vinylamine and allylamine, and unsaturated amines that can be copolymerized with unsaturated amines such as dimethylacrylamide, styrene, methyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, styrene sulfonic acid, and salts thereof. Copolymers with other monomers having a saturated bond are also included.

The above amines include a hydroxyalkyl group,
Those having an acyl group, an alkyl group or the like as the N-substituent may be used. The N-hydroxyalkyl substituent can be introduced by reacting the amines with an epoxy alkane; the N-acyl substituent is introduced by reacting the amines with a fatty acid; N
An alkyl substituent is introduced by reacting the amines with an alkyl halide; The N-hydroxyalkyl substituent preferably has 2 to 28 carbon atoms in the alkyl group, and the N-acyl substituent preferably has 2 to 26 carbon atoms.
It is preferred that The N-alkyl substituent preferably has 2 to 22 carbon atoms.

Further, a polycondensed polyamine obtained by polycondensation of the above amines and epihalohydrin and a polycondensed polyethyleneimine can also be used. Epihalohydrin includes epichlorohydrin, epibromohydrin, epiiodohydrin and the like. The amines may be other than those described above as long as they have an active hydrogen atom bonded to a nitrogen atom and can react with carbon disulfide to form a dithiocarbamic acid group.

A hydroxyalkyl group to the above amines,
The reaction for introducing an N-substituent such as an acyl group or an alkyl group or the polycondensation reaction between an amine and epihalohydrin may be performed before or after the reaction between the amine and carbon disulfide. When the reaction is performed before the reaction with carbon, an N-substituent is introduced into the amines, or after the polycondensation of the amines with epihalohydrin, the dithiocarbamic acid group reacts with carbon disulfide to form a dithiocarbamic acid group. It is necessary that as many active hydrogen atoms as can be formed remain in the amines.

The reaction between amines and carbon disulfide can be carried out by, for example, dissolving the amines in a solvent such as water or alcohol, and adding carbon disulfide to the reaction to react. The dithiocarbamic acid type functional group may be an acid type or a salt type, and after completion of the reaction, a hydroxide or carbonate of an alkali metal (eg, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, etc.) )
Alkaline earth metal hydroxides and carbonates (for example, calcium hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, etc.) or alkali such as ammonia, or the reaction of amines with carbon disulfide, By performing the reaction in the presence of these alkalis, a metal collector having a salt type dithiocarbamic acid type functional group can be obtained.

The metal scavenger having a dithiocarbamic acid group is not limited to the above, and may be, for example, a compound having another functional group in addition to a dithiocarbamic acid type functional group. Among the metal collectors having a dithiocarbamic acid group, dimethyldithiocarbamic acid and salts thereof, diethyldithiocarbamic acid and salts thereof, ethylenediamine-polydithiocarbamic acid and salts thereof, diethylenetriamine-polydithiocarbamic acid and salts thereof, and triethylenetetramine-poly Dithiocarbamic acid and its salts,
Tetraethylenepentamine-polydithiocarbamic acid and salts thereof, and polyethyleneimine-polydithiocarbamic acid and salts thereof are preferred.

In the method of the present invention, the above-mentioned metal collecting agent is
Two or more different compounds can be used in combination.

After the addition of a metal collecting agent to the filtration residue, the metal in the filtration residue is collected and fixed by kneading as necessary. When performing this treatment, water may be further added as necessary.

The filtration residue on which the metal is immobilized by the metal-collecting agent as described above is solidified with cement, if necessary, and finally disposed of by landfilling or ocean dumping. On the other hand, the metal contained in the ash may be eluted in the water (filtrate) used for washing the ash containing the metal. For this reason, it is preferable to add a metal collecting agent to the filtrate so that the metal eluted in the filtrate is collected and removed by the metal collecting agent. As the metal collecting agent for collecting the metal in the filtrate, the same compounds as described above can be used. The metal in the filtrate is collected by the metal collecting agent and precipitated and removed as flocs. The filtrate from which flocs have been removed can be safely discharged to rivers and the like.

[0021]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. The complex forming compounds used in the following Examples and Comparative Examples are as follows.

Metal collector a: sodium dimethyldithiocarbamate.

Metal collector b: N, N'-dimethylethylenediamine-sodium dithiocarbamate.

Metal collector c: tetraethylenepentamine-sodium tetradithiocarbamate

Metal scavenger d: polyethyleneimine-sodium polydithiocarbamate (0.7 mol of carbon disulfide adduct per ethyleneimine unit)

Metal collecting agent e: diethylenetriamine-
Sodium tridithiocarbamate

Examples 1 to 5 A mixture of 10 tons of incinerated ash and fly ash generated in a garbage incineration plant was heated and melted at 1200 ° C. in a heating and melting furnace, and the waste gas generated at that time was passed through a bag filter. The molten fly ash was recovered. This molten fly ash contained the amounts of lead, cadmium, mercury, calcium, sodium, and potassium shown in Table 1. 20 kg of water was added to 10 kg of the molten fly ash, and the mixture was stirred at 25 ° C. for 2 hours for washing, and then filtered with a GA-100 filter paper using a press filter. Table 1 shows the amounts of metals contained in the filtrate and the filtration residue. A metal collecting agent shown in Table 2 was added to the filtration residue, kneaded and allowed to stand for 6 hours, and then a metal elution test from the filtration residue was performed. The metal dissolution test was performed in accordance with the Environment Agency Notification No. 13. Table 3 shows the results.

On the other hand, to the filtrate from which the molten fly ash was washed, the same metal collecting agent as that added to the filtration residue was added in the amount shown in Table 2, and the mixture was stirred for 1 hour and allowed to stand for 1 hour. The formed floc was removed by precipitation. Table 2 also shows the results of measuring the residual metal concentration in the filtrate after removing the floc from the precipitate.
Table 3 also shows the total amount of the metal scavenger added to the filtrate and the metal scavenger added to the filtration residue.

[0029]

[Table 1]

[0030]

[Table 2] * 1: For Comparative Examples 1 to 5, the amount of metal scavenger added to the raw ash.

[0031]

[Table 3]

Comparative Examples 1 to 5 The same molten fly ash as used in Examples 1 to 5 was used without washing, and 10 kg of the molten fly ash was mixed with a metal collector in an amount shown in Table 2 and kneaded. After standing for 6 hours, a test for dissolution of metal from the filtration residue was performed in the same manner as in Examples 1 to 5. Table 3 shows the results. The amount of the metal scavenger added in the comparative example in Table 2 is the minimum necessary for immobilizing the metal so that the amount of metal eluted from the raw ash according to the Environment Agency Notification No. 13 test is below the reference value. Quantity.

[0033]

As described above, according to the method of the present invention, even when a metal salt such as a calcium salt, a sodium salt or a potassium salt is contained in the ash, the metal contained in the ash is not eluted. Therefore, it is not necessary to particularly add a large amount of the metal collecting agent in order to prevent the immobilized metal from being eluted by the metal collecting agent.
According to the method of the present invention, it is possible to reduce the amount of a metal collecting agent used for immobilizing a metal in an ash containing a metal salt such as a calcium salt, a sodium salt, and a potassium salt. Cost can be significantly reduced.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Hosoda 1 at Nishiide, Noyoro-cho, Iwakura-shi, Aichi Prefecture Inside Nagoya Plant of Miyoshi Oil & Fats Co., Ltd. (72) Inventor Masatake Kawashima 4-66 Horikiri, Katsushika-ku, Tokyo No. 1 Miyoshi Oil & Fat Co., Ltd. (72) Inventor Masafumi Moriya 4-66-1, Horikiri, Katsushika-ku, Tokyo F-term in Miyoshi Oil & Fat Co., Ltd. 3K061 NA01 NA02 NA07 NA15 NA18 4D004 AA36 AA37 AB03 CA15 CA40 CA50 CC06

Claims (3)

[Claims] An ash containing metal, wherein the ash containing metal is washed with water and filtered, and then a metal collecting agent is added to the filtration residue, and the metal in the residue is fixed by the metal collecting agent. Processing method. 2. A metal-containing ash is washed with water and filtered, and then a metal collecting agent is added to the filtrate to collect and remove the metal eluted in the filtrate with the metal collecting agent. A method for treating ash, comprising adding a collector and fixing the metal in the residue with a metal collector. 3. The method for treating ash according to claim 1, wherein the ash is fly ash.