JP4084503B2 - Processing method of incinerated fly ash containing dioxins - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating dioxin-containing incinerated fly ash. In particular, the present invention relates to a technology for detoxifying high chlorine content incineration fly ash containing dioxins generated when municipal waste is incinerated.
[0002]
[Prior art and problems to be solved by the invention]
Incineration ash composed of incineration main ash (incineration ash) and incineration fly ash (dust) when incineration of so-called municipal waste, which is discharged from urban factories, offices, ordinary households, etc. appear. At present, these incineration ash is landfilled at the final disposal site. However, in recent years, it has become clear that incinerated fly ash contains a large amount of dioxins, and there are concerns about soil contamination and water pollution due to dioxins resulting from landfill of incinerated fly ash. In addition, the remaining years of the final disposal site are decreasing, and there is an urgent need for detoxification of incineration ash and development of effective utilization technology.
[0003]
Under such circumstances, development of a technique for effectively using incinerated ash as a raw material for cement and decomposing and detoxifying dioxins contained in the incinerated ash by heat in the cement burning process has been performed.
As one of them, a treatment technique for directly injecting waste incineration ash containing dioxins into a cement kiln that produces cement clinker from cement raw materials and thermally decomposing dioxins in the incineration ash by heat during clinker firing (Japanese Patent Laid-Open No. Hei 11). No. 19623).
[0004]
However, this proposed technique is an inappropriate technique considering the difference in the components contained in the incineration fly ash and incineration main ash. In other words, this proposed technique does not separate the incineration fly ash and the incineration main ash, but treats them in the state of waste incineration ash mixed with them. For this reason, since the incineration main ash which hardly contains dioxins is also processed together with the incineration fly ash containing a large amount of dioxins, it is not possible to efficiently treat dioxins.
[0005]
Furthermore, since the waste incineration fly ash contains a large amount of chlorine compounds, the incineration ash mixed with the incineration fly ash and the incineration main ash is not subjected to pretreatment as in the technique of JP-A-11-19623. When it is directly input to the cement kiln, the input amount is limited. In other words, when a large amount of waste incineration ash, especially incineration fly ash, is put into a cement kiln without pre-treatment by desalination, the chlorine content in the waste incineration fly ash is transferred between the suspension preheater and the rotary kiln in the high temperature part. Since it repeatedly concentrates by volatilization and solidification in a low temperature part, a low melting point compound containing chlorine is generated, which is fused in the suspension preheater, causing troubles such as cyclone blockage. In addition, the chlorine concentration in the cement to be produced increases, and when used in a reinforcing bar structure, it causes corrosion of the reinforcing bar.
[0006]
As described above, in the technique proposed in Japanese Patent Application Laid-Open No. 11-19623, not only the dioxins in the waste incineration fly ash cannot be efficiently treated, but also the cement kiln is inhibited from being stably operated and further produced. There is a risk of deteriorating the quality.
Therefore, the first problem to be solved by the present invention is to detoxify highly toxic dioxins in incineration fly ash.
[0007]
The second problem to be solved by the present invention is to efficiently perform the detoxification treatment of dioxins.
The third problem to be solved by the present invention is to stably and efficiently perform the detoxification treatment of dioxins.
The fourth problem to be solved by the present invention is not only to detoxify dioxins but also to detoxify dioxins at the time of cement production, and to newly dispose of incinerated fly ash containing a large amount of dioxins. Recycling incineration fly ash without the need for wastewater.
[0008]
The fifth problem to be solved by the present invention is not only to detoxify dioxins but also to perform detoxification of dioxins at the time of cement production, and new disposal of incinerated fly ash containing a large amount of dioxins The recycling of incinerated fly ash is not required, and the quality of the cement obtained is not changed.
[0009]
[Means for Solving the Problems]
The first to fifth problems are as follows:
Removal of removing chlorine compounds by adding water to high chlorine content incineration fly ash containing dioxins, dissolving water-soluble chlorine compounds contained in the incineration fly ash, and then filtering the suspension Process,
After the removing step, a slurry-like desalted product in which dioxins hardly soluble in water remain is transferred to a 900 to 1100 ° C. portion of a rising duct under a suspension preheater for cement production by a pump. And a decomposition process for decomposing dioxins, which is solved by a method for treating incinerated fly ash containing dioxins.
Also, a recovery process for separately collecting the main ash and fly ash of incineration ash,
A step of introducing the main ash obtained in the recovery step into a raw material system of a cement manufacturing step;
By adding water to the high chlorine content incineration fly ash containing dioxins obtained in the recovery step, dissolving the water-soluble chlorine compound contained in the incineration fly ash, and then filtering the suspension A removing step of removing the chlorine compound;
After the removing step, a slurry-like desalted product in which dioxins hardly soluble in water remain is transferred to a 900 to 1100 ° C. portion of a rising duct under a suspension preheater for cement production by a pump. And a decomposition process for decomposing dioxins, which is solved by a method for treating incinerated fly ash containing dioxins.
[0010]
As a method for removing the water-soluble chlorine compound contained in the incineration fly ash, for example, the method described in Japanese Patent Application No. 10-156202 already filed by the applicant of the present invention may be adopted. I can do it. Of course, it is not limited to this.
Of the waste incineration ash, the incineration main ash contains almost no dioxins and has a low content of chlorine compounds. On the other hand, incineration fly ash contains a large amount of dioxins, and chlorine compounds also contain 10 to 20% in terms of chlorine concentration. Therefore, in the case of incinerated main ash, there is no need to treat dioxins and no desalting treatment, so it can be used as it is as a cement raw material in any part such as a raw material system or a firing system.
[0011]
On the other hand, in the case of incineration fly ash, when it is put into the cement manufacturing process, it may cause the cyclone clogging as mentioned above, so it is necessary to desalinate as a pretreatment, and dioxins are surely In order to decompose it, it is necessary to put it in a high temperature part of 800 ° C. or higher in the cement manufacturing process. Therefore, incineration main ash and incineration fly ash are not mixed, incineration main ash is used directly as a cement raw material as described above, and incineration fly ash is washed and desalted by the method of Japanese Patent Application No. 10-156202, for example. Injecting a large amount of incineration fly ash without impairing the stable operation of the cement kiln and adversely affecting the quality of the cement by putting it in the part of the rotary kiln and / or suspension preheater at 800 ° C or higher. It can be put into a cement kiln and dioxins can be processed efficiently.
[0012]
That is, as in the present invention, for example, by the method of Japanese Patent Application No. 10-156202, high chlorine-containing incinerated fly ash containing dioxins is washed with water and desalted, and then the rotary kiln for cement production and / or 800 ° C. below the suspension preheater is used. By injecting into the above high temperature part, the incineration fly ash brings in a very small amount of chlorine into the cement kiln, so that the chlorine content does not repeatedly concentrate and volatilize between the suspension preheater and the rotary kiln. The possibility of troubles such as cyclone blockage due to the generation of a low melting point compound containing chlorine is reduced, and stable operation can be achieved. In addition, high-quality cement can be produced without increasing the chlorine content in the produced cement.
[0013]
Further, it has been confirmed that the solubility of dioxins contained in incineration fly ash in water is very small. Even if the incineration fly ash is washed with water and desalted by the method of Japanese Patent Application No. 10-156202, dioxin is obtained. Will not dissolve in water and will remain on the desalted incineration fly ash side. Accordingly, the dioxins are reliably decomposed by putting the incinerated fly ash after the desalting treatment into the rotary kiln and / or suspension preheater for cement production.
[0014]
In particular, dioxins are said to decompose in a few seconds at temperatures of 800 ° C. or higher. Therefore, dioxins are reliably decomposed when placed in the lower part of a rotary kiln or suspension preheater for cement production. This is because the maximum baking temperature of the rotary kiln is about 1450 ° C., and the temperature range of 800 ° C. or more from the lower part of the suspension preheater to the clinker outlet of the rotary kiln is usually 30 minutes or more.
[0015]
In addition, when desalinized fly ash containing dioxins is introduced below the rotary kiln and / or suspension preheater for cement production, even if the dioxins in the fly ash are not instantly decomposed, undecomposed Dioxins are caught by the raw material while passing through the multistage cyclone on the upper part of the suspension preheater, and again pass through the high temperature part, so that they are reliably decomposed. On the other hand, for example, when incinerated fly ash after desalting is put into the raw material system of the cement manufacturing process, dioxins remain inside the dryer, raw material mill, electrostatic precipitator, etc., so periodic inspections and repairs in the equipment Workers may be exposed to dioxins during work. Also from such a side, a method of introducing desalted fly ash containing dioxins into the lower part of a rotary kiln and / or suspension preheater for cement production is useful.
[0016]
Further, when desalting is performed using a horizontal belt filter by the method of Japanese Patent Application No. 10-156202, the obtained desalted incineration fly ash contains about 47% of water. Even if the water content is about 47%, the desalted fly ash is in the form of a fluid slurry and can be transported by a slurry pump or the like, but it is highly viscous and difficult to transport. When high power is required, liquid fuel such as water and heavy oil or urea solution for denitration, and other waste liquids such as waste oil are added to the fly ash after desalting to make a slurry with low viscosity. After that, it is effective to transfer the incinerated fly ash to the charging part with a pump or the like.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The present invention adds water to high chlorine content incineration fly ash containing dioxins, dissolves the water-soluble chlorine compound contained in the incineration fly ash, and then filters the suspension to filter the suspension. After removing the water, put the demineralized treatment product in which dioxins hardly soluble in water remain into the rotary kiln for cement production and / or the suspension preheater at 800 ° C or higher, containing dioxins that decompose the dioxins Incineration fly ash treatment method. For example, incinerated fly ash containing dioxins is washed and desalted by the method of Japanese Patent Application No. 10-156202, and then put into a rotary kiln and / or suspension preheater at a temperature lower than 800 ° C. for cement production. It has a step of decomposing dioxins contained in fly ash. In addition, before charging the rotary kiln and / or suspension preheater, add a liquid consisting of water, fuel such as heavy oil, urea solution for denitration, and / or liquid waste such as waste oil to the desalted material. Then, this mixture is put into a portion of the rotary kiln and / or suspension preheater at a temperature of 800 ° C. or higher. This facilitates transfer and input.
[0018]
Hereinafter, the present invention will be described in more detail.
FIG. 1 shows an example of an apparatus for decomposing and detoxifying dioxins by introducing fly ash after desalting treatment into the lower part of the suspension preheater of the cement kiln in the method for treating incinerated fly ash containing dioxins according to the present invention. .
First, the main ash and fly ash of incineration ash generated at municipal waste incineration facilities are separately collected and transported to a cement manufacturing plant. Of the incinerated ash, the main ash removes foreign matters such as iron scraps, and then enters the raw material system of the cement manufacturing process as it is to be used as part of the cement raw material. On the other hand, the fly ash is washed and desalted by the method of Japanese Patent Application No. 10-156202, for example.
[0019]
Here, the desalting method of Japanese Patent Application No. 10-156202 will be briefly described.
First, fly ash is put into a dissolution tank, and warm water is added here to dissolve a chlorine compound contained in the fly ash in a liquid phase.
Next, the fly ash suspension is filtered using, for example, a horizontal belt type filter. At this time, it is possible to perform desalting more efficiently by spraying the fly ash cake formed on the belt filter with water. The fly ash cake thus desalted is treated by the method of the present invention in the next step. On the other hand, the filtrate is discharged out of the system through a wastewater treatment system that removes heavy metals and the like.
[0020]
The desalted fly ash cake is put into the fly ash slurry agitation tank 1 of FIG. Here, if necessary, water or the like is added to the cake to form a slurry with low viscosity and high fluidity. The desalted fly ash in the form of a slurry is fed by a slurry pump 2 into a rising duct 5 below the calcining furnace 4 via a fly ash slurry introduction pipe 3. The temperature inside the rising duct 5 is approximately 900 to 1100 ° C., and the dioxins are instantaneously decomposed. Even if it is not decomposed and transported with the exhaust gas, it is caught by the raw material descending in the upstream calcining furnace and the multistage cyclone of the suspension preheater 6 and enters the high temperature region again, and finally the rotary kiln is Since it passes, the dioxins contained in the incinerated fly ash are completely decomposed.
[0021]
The apparatus shown in FIG. 1 is an example used for carrying out the present invention, and does not limit the scope of the present invention.
[0022]
【Example】
Municipal waste incineration fly ash containing 14.1% chlorine and 3.0 ng-TEQ / g dioxins was desalted by the desalting method of Japanese Patent Application No. 10-156202. The chlorine content of the fly ash after the desalting treatment was 0.43%, and the desalting efficiency was 97.0%. The water content of the fly ash after desalting was 47%. Further, no dissolution of dioxins in the filtrate was observed.
[0023]
Next, this desalted fly ash was first stirred with the apparatus shown in FIG. 1 in the fly ash slurry agitation tank 1 and sufficiently stirred to adjust the water content to 55%. An ejector is used for the fly ash slurry introduction pipe 3, and the slurry is transferred to the ejector by the slurry pump 2, where compressed air is introduced into the ejector and the lower portion of the suspension preheater 6 is introduced at a rate of 2.5 t / h. It sprayed in the rising duct 5. This cement kiln was able to produce 7000 tons of clinker per day, the temperature of the part where the fly ash slurry was charged was about 1000 ° C., and the firing temperature of the rotary kiln 7 was 1400 to 1500 ° C. Moreover, the residence time of those sections was about 40 minutes.
[0024]
After 24 hours from the start of spraying of the fly ash slurry, the cement kiln-based final exhaust gas was sampled and analyzed for the concentration of dioxins, which was 0.01 ng-TEQ / Nm ³ or less.
Furthermore, although the fly ash slurry was continuously fed for one week, no trouble such as cyclone blockage was observed.
[0025]
From the above results, it was shown that the dioxins contained in the fly ash were completely decomposed by the method of the present invention, and high quality cement could be produced without adversely affecting the stable operation of the cement kiln. .
[0026]
【The invention's effect】
(1) Highly toxic dioxins are efficiently detoxified.
{Circle around (2)} Dioxins are detoxified and fly ash input to the cement kiln is effectively recycled as a substitute for cement raw materials.
(3) Detoxification treatment of dioxins can be performed without adversely affecting the stable operation of the cement kiln.
(4) There is no adverse effect on the quality of the cement obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a cement manufacturing apparatus in which the method for treating incinerated fly ash containing dioxins according to the present invention is implemented.
DESCRIPTION OF SYMBOLS 1 Fly ash slurry stirring tank 2 Slurry pump 3 Fly ash slurry introduction pipe 4 Calcining furnace 5 Rising duct 6 Suspension preheater 7 Rotary kiln

Claims (2)

Removal of removing chlorine compounds by adding water to high chlorine content incineration fly ash containing dioxins, dissolving water-soluble chlorine compounds contained in the incineration fly ash, and then filtering the suspension Process,
After the removing step, a slurry-like desalted product in which dioxins hardly soluble in water remain is transferred to a 900 to 1100 ° C. portion of a rising duct under a suspension preheater for cement production by a pump. A method for treating incinerated fly ash containing dioxins, comprising a decomposition step of decomposing dioxins. A recovery process for separately recovering main ash and fly ash of incineration ash;
A step of introducing the main ash obtained in the recovery step into a raw material system of a cement manufacturing step;
By adding water to the high chlorine content incineration fly ash containing dioxins obtained in the recovery step, dissolving the water-soluble chlorine compound contained in the incineration fly ash, and then filtering the suspension A removing step of removing the chlorine compound;
After the removing step, a slurry-like desalted product in which dioxins hardly soluble in water remain is transferred to a 900 to 1100 ° C. portion of a rising duct under a suspension preheater for cement production by a pump. A method for treating incinerated fly ash containing dioxins, comprising a decomposition step of decomposing dioxins.

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