JPH10180222A - Treatment of waste incineration fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry process treating method of waste incineration fly ash by which heavy metals contained in incineration fly ash discharged from a waste incineration furnace are converted into compounds hardly eluted to subject them to stabilizing treatment and also decomposing dioxin contained in the incineration fly ash to make it harmless. SOLUTION: In this treating method of waste incineration fly ash, waste incineration fly ash is fed from an incineration fly ash feeding port 5 and is stayed in a fly ash heating reactor 1 in which waste incineration fly ash is heated and reacted, and while the fly ash heating reactor in which waste incineration fly ash is thus stayed is heated to a temperature of 350 deg. to 400 deg.C, a gaseous sulfurizing agent is blown into the fly ash heating reactor from a sulfurizing agent inlet 6, causing heavy metals such as lead and zinc contained in fly ash to be converted into hardly soluble sulfides, thereby stabilizing the heavy metals and also decomposing dioxin contained in fly ash to make it harmless.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for stabilizing heavy metals by converting heavy metals contained in incineration fly ash discharged from a refuse incinerator into compounds that are hardly eluted, The present invention relates to a method for detoxifying incineration fly ash, which decomposes dioxin contained therein.

[0002]

2. Description of the Related Art Generally, municipal waste and industrial waste are incinerated. Most of the incineration residues generated during this incineration are disposed of in landfills. However, this incineration residue contains a lot of harmful heavy metals such as lead and zinc, and the heavy metals elute after landfill disposal, which is a problem.

[0003] Among the incineration residues, in particular, incineration fly ash collected by a bag filter or an electric dust collector contains heavy metals at a higher concentration than the main ash, so that it becomes a specially controlled general waste. It is designated and its detoxification is required.

At present, as a method of detoxifying incinerated fly ash,
Methods of melting and solidifying fly ash to solidify, cement solidification of solidifying fly ash with cement, and acid extraction of extracting acid in the fly ash have been adopted. Further, the following technology has been proposed as a detoxification method for incinerated fly ash. (1) JP-A-63-111990, "Method for stabilizing heavy metals in refuse incineration fly ash" (hereinafter, referred to as prior art 1) (2) JP-A-7-100455, "Hazardous heavy metals contained in fly ash Detoxification Method ”(hereinafter referred to as Prior Art 2) In the above-mentioned Prior Art 1 and 2, incineration fly ash is brought into contact with a liquid sulphidizing agent using a dedicated reaction tank and sedimentation tank to react. Processing.

Further, in recent years, PCDDs (polychlorinated dibenzodioxin) and PCDFs (polychlorinated dibenzofuran) among organic chlorine compounds contained in fly ash have been known as extremely toxic substances (hereinafter, referred to as "highly toxic substances"). PCDD
s, PCDFs are collectively referred to as dioxins). As a method of reducing dioxin in the fly ash, the following fly ash heat treatment method has been proposed. (3) Japanese Patent Application Laid-Open No. 7-112172 "Dust ash treatment method"
(Hereinafter referred to as prior art 3)

[0006]

The prior art has the following problems. That is, in the prior arts 1 and 2, water is mixed in addition to the fly ash and the liquid sulphide to make the fly ash muddy or lumpy, and the fly ash is reacted with the sulphide. Therefore, there is a problem that the fly ash and the sulphating agent do not sufficiently contact each other, and the reaction efficiency is poor.

In prior art 3, there is a problem that a special device is required separately from the heavy metal processing device for the treatment of dioxin. Therefore, the object of the present invention is
Waste incineration fly ash treatment that overcomes the problems of the prior art described above, effectively detoxifies the incineration fly ash, and decomposes the dioxin in the fly ash without installing a new treatment device. There is a way to provide.

[0008]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems. As a result, it is thrown into the fly ash heating reactor that heats and reacts the incinerated fly ash,
By retaining and heating the fly ash to a predetermined temperature and blowing a gaseous sulphide, the reaction efficiency between heavy metals such as lead and zinc contained in the fly ash and the sulphide is increased,
In addition, the inventors have found that dioxin contained in fly ash can be decomposed and fly ash can be efficiently rendered harmless.

The waste incineration fly ash treatment method of the present invention is based on the above findings, and is provided in a fly ash heating reactor in which the waste incineration fly ash is heated and reacted. Injecting and retaining, while heating the fly ash heating reactor in which the refuse incineration fly ash is retained to a predetermined temperature, by blowing a gaseous sulphide into the fly ash heating reactor, It converts heavy metals such as lead and zinc contained in fly ash into hardly soluble sulfides, thereby stabilizing the heavy metals, and decomposing dioxins contained in fly ash to render them harmless. It is assumed that.

Further, in the method for treating incineration fly ash of the present invention, the fly ash heating reactor is heated to a temperature within the range of 350 to 400 ° C., and the fly ash in the fly ash heating reactor is heated. The dioxin in the fly ash is decomposed by setting the residence time of the fly ash to 15 minutes or more.

Further, in the method for treating incineration fly ash according to the present invention, the fly ash heating reactor has a stirring blade having a heater and a sulphidizing agent injection port for injecting the sulphiding agent into a central axis thereof. The fly ash heating reactor is heated to a temperature in the range of 350 to 400 ° C. by the heater, and the sulphating agent is blown and the fly ash is stirred by the stirring blades. It is characterized in that it promotes the reaction of ash with a sulfurizing agent.

[0012]

DETAILED DESCRIPTION OF THE INVENTION Next, a method for treating incineration fly ash of the present invention will be described in detail with reference to the drawings.

The refuse incineration system includes a furnace body, a fly ash heating reactor, a dust collector, and the like. FIG. 1 shows a fly ash heating reactor used in one embodiment of the treatment method of the present invention. In FIG. 1, 1 is a fly ash heating reactor, 2 is a heater, 3 is a sulphating agent injection port, 4 is a stirring blade, 5 is an incineration fly ash inlet, 6 is a sulphidating agent inlet, 7 is an exhaust gas outlet, and 8 is treated ash. Each exit is shown.

In the treatment method of the present invention, incinerated fly ash generated when waste is incinerated is introduced into the fly ash heating reactor 1 from the fly ash inlet 5, and the fly ash heating reactor is heated by the heater 2. Heat to a predetermined temperature. The fly ash supplied to the fly ash heating reactor stays therein for a predetermined time. The sulphide blown into the fly ash heating reactor from the sulphidant inlet 6 is blown from the sulphide blow-in port toward the heated fly ash retained in the fly ash heating reactor as shown by the arrow. At the same time, the fly ash and the sulphating agent are stirred by the stirring blades 4 to promote the reaction between the heavy metals and the sulphidating agent in the fly ash and move toward the other end of the fly ash heating reactor. . The treated ash after the reaction is discharged from the treated ash outlet, and the remaining exhaust gas is discharged from the exhaust gas outlet 7. It should be noted that the sulfide agent inlet may be located at a position other than that shown in FIG.

As described above, by blowing a gaseous sulphide into the fly ash, heavy metals such as lead and zinc contained in the fly ash can be converted into hardly soluble sulfides and stabilized. . By using a gaseous sulphidizing agent, the sulphating agent and the fly ash can be efficiently contacted in a state where the ash is dry because no water is used. By employing the dry processing in this way, the processing apparatus can be made compact.

In the method of the present invention, the fly ash heating reactor is heated to a temperature in the range of 350 to 400 ° C., and the time during which the incinerated fly ash stays in the fly ash heating reactor is 15 minutes or more. By this, the reaction between the heavy metals contained in the incineration fly ash and the sulphidizing agent proceeds sufficiently, and the heavy metals can be converted into the hardly soluble sulfide,
Dioxin in fly ash can be decomposed. When the heating temperature is lower than 350 ° C., the amount of dioxin increases.
On the other hand, when the heating temperature exceeds 400 ° C., the amount of generated SOx exceeds 10 ppm. If the time during which the fly ash stays in the fly ash heating reactor is less than 15 minutes, the dioxin decomposition rate decreases. Therefore, the heating temperature of the fly ash heating reactor (the temperature at which the heavy metals contained in the incinerated fly ash react with the sulfide agent)
Should be limited to 350 to 400 ° C., and the time during which fly ash stays in the fly ash heating reactor should be 15 minutes or more.

[0017]

EXAMPLES The method for treating incineration fly ash of the present invention will be described with reference to examples. The fly ash heating reactor shown in FIG. 1 was used, and hydrogen sulfide was used as a sulfide agent. While changing the heating temperature of the fly ash heating reactor and the time during which the fly ash stays in the fly ash heating reactor, the fly ash reacts with hydrogen sulfide, and is moved by the stirring blades in the fly ash heating reactor and treated. Discharged as ash. The injection amount of hydrogen sulfide
The total molar ratio of Pb, Zn and Cd was 1 or more. The reaction rate between fly ash and hydrogen sulfide is shown in FIG.

In FIG. 2, the vertical axis indicates the reaction rate (%), and the horizontal axis indicates the reaction temperature (° C.). As is clear from FIG. 2, when the reaction temperature is 400 ° C. or less, if the residence time is 5 minutes or more, the reaction rate becomes approximately 100%, and the reaction between fly ash and hydrogen sulfide proceeds sufficiently. Heavy metals contained in fly ash can be converted into hardly soluble sulfides.

The heavy metal oxides in the fly ash are converted into sulfides by the following reaction. _{PbO + H 2 S = PbS +} H 2 O ZnO + H 2 S = ZnS + H 2 O CdO + H 2 S = CdS + H 2 O Then, the fly ash collected by the dust collector in which (defined in Environment Agency Notification No. 13) A dissolution test was performed. Table 1 shows the results. As is clear from Table 1, the amount of elution of heavy metals such as lead and zinc contained in the incineration fly ash collected by the dust collector is less than the measurable value, and according to the method for treating garbage incineration fly ash of the present invention. We were able to fully meet the environmental standards.

[0020]

[Table 1]

Further, the state of SOx generation when the reaction temperature (heating temperature of the fly ash heating reactor) was changed as described above was examined. The result is shown in FIG. In FIG.
The vertical axis indicates SOx (ppm), and the horizontal axis indicates reaction temperature (° C.). As is clear from FIG. 3, when the reaction temperature is 400 ° C. or less, the amount of SOx generated can be suppressed to 10 ppm or less.

Further, the decomposition rate of dioxin when the reaction temperature and the residence time were changed as described above was examined. FIG. 4 shows the results. In FIG. 4, the vertical axis indicates the decomposition rate of dioxin (%), and the horizontal axis indicates the reaction time (min). ● indicates a reaction temperature of 350 to 400 ° C., □ indicates a reaction temperature of 400 to 450 ° C., and ▲ indicates a reaction temperature of 450 to 500 ° C. As is clear from FIG. 4, in order to decompose dioxin, the reaction temperature is 350 ° C. or more and the residence time is 15 minutes.
Must be at least minutes. When the reaction time was less than 350 ° C., it was confirmed that the amount of dioxin generated increased.

[0023]

According to the present invention, heavy metals contained in incineration fly ash discharged from a refuse incinerator are converted into compounds that are difficult to elute, stabilizing the heavy metals and contained in the fly ash. Provided is a dry treatment method for incineration fly ash, which can decompose dioxin and render it harmless,
An industrially useful effect is provided.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a fly ash heating reactor in one embodiment of the method of the present invention.

FIG. 2 is a graph showing the relationship between reaction temperature, conversion and residence time in the process of the present invention.

FIG. 3 shows the reaction temperature and S in the method of the present invention.
It is a graph which shows the relationship between Ox production amount.

FIG. 4 is a graph showing the relationship between reaction temperature, reaction time and dioxin decomposition rate in the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fly ash heating reaction device 2 Heater 3 Sulfurizing agent injection port 4 Stirrer blade 5 Incineration fly ash inlet 6 Sulfurizing agent inlet 7 Exhaust gas outlet 8 Treatment ash outlet

Continued on the front page (72) Inventor Masahiro Sudo 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (3)

[Claims] Claims 1. An incinerated fly ash is charged and retained in a fly ash heating reactor in which the incinerated fly ash is heated and reacted.
By blowing a gaseous sulphide into the fly ash heating reactor while heating the fly ash heating reactor in which the refuse incineration fly ash stays at a predetermined temperature, the fly ash is included in the fly ash. Converting waste metals such as lead and zinc into hardly soluble sulfides, thereby stabilizing the heavy metals, and decomposing dioxins contained in fly ash to make them harmless. Ash treatment method. 2. The fly ash heating reactor according to claim 1,
Heating to a temperature in the range of ° C., and decomposing the dioxin in the fly ash by setting the residence time of the fly ash in the fly ash heating reactor to 15 minutes or more. A method for treating incinerated fly ash according to claim 1. 3. The fly ash heating reaction device has a heater and a stirring blade having a sulphidant injection port for blowing the sulphidant into a central axis of the heater, and the fly ash heating device is operated by the heater. It is heated to a temperature in the range of 350 to 400 ° C., and the blowing of the sulphide and the agitation of the fly ash are performed by the agitating blades, thereby promoting the reaction of the fly ash with the sulphide. The method for treating incinerated fly ash according to claim 1.