JP2000016844A - Pyrolysis of dioxin and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for pyrolyzing dioxin worried on the employment of incinerated ash in the production of an ecological cement, and to provide a device for pyrolyzing the dioxin. SOLUTION: This method for pyrolyzing dioxin comprises collecting kiln dust containing the non-pyrolyzed dioxin, treating the collected kiln dust 14 with an acid to precipitate the dioxin together with the lead product, heating the precipitates at a higher temperature than the boiling point of the dioxin, guiding the evaporated dioxin-containing gas 20 into a rotary kiln 3 for calcining a cement, and subsequently pyrolyzing the guided dioxin with heat on the calcination of the cement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for thermally decomposing dioxin to make it harmless, and more particularly to a method and apparatus for efficiently decomposing dioxin contained in incinerated ash in a cement kiln. .

[0002]

2. Description of the Related Art In recent years, municipal solid waste, general waste and industrial waste have increased remarkably, and effective use and recycling of such waste have been attempted in various fields. As one of the methods,
The use of incinerated ash and industrial waste in incineration plants as so-called ecocement, which uses the incinerated ash as a raw material for cement production, has also been intensively studied. However, these incineration ash usually contain a considerable amount of dioxin, and there is an urgent need for how to remove or decompose dioxin in the incineration ash.

It is known that dioxin decomposes when heated to a high temperature, for example, as disclosed in Japanese Patent Application Laid-Open No. 10-10907.
No. 6 discloses a method of thermally decomposing dioxin in nitrogen gas, and Japanese Patent Application Laid-Open No. 10-109080 discloses a method of decomposing dioxin by charging incinerated ash into a middle stage of a coke cooling furnace. Is disclosed. The present applicant has also filed an application concerning the production of ecocement using incinerated ash and the removal of dioxin in the process (Japanese Patent Application No. 10-05814).

[0004]

However, in these methods, the kiln dust discharged from the rotary kiln is collected by a bag filter, and the dioxin adsorbed on the residue is heated in another heating furnace. It requires new equipment and heat sources, requires a large amount of processing, and increases processing costs. The present invention has been made to further solve these problems.The present invention concentrates dioxin into lead products, guides dioxin volatilized therefrom to a rotary kiln, and decomposes the lead products so that the lead products can be reused as metal resources. It is.

[0005]

That is, the present invention provides a method for heating a material containing dioxin to a temperature not lower than the boiling point of dioxin, introducing a gas containing volatile dioxin into a rotary kiln for sintering cement, It is intended to provide a method for thermally decomposing dioxin by heat.

Still further, the present invention provides a method for manufacturing cement by using incinerated ash of municipal solid waste or industrial waste as a part of raw materials to collect undecomposed dioxin-containing kiln dust and collect the collected kiln dust. The kiln dust is heated to a temperature equal to or higher than the boiling point of dioxin, and gas containing volatile dioxin is introduced into a rotary kiln for cement firing,
A method for thermally decomposing dioxin by heat during cement firing is also provided.

In this case, the collected kiln dust is separated into a lead product mainly composed of lead and other components by acid treatment, and dioxin accompanying the lead product is heated to a temperature higher than the boiling point of dioxin. Thus, a method for thermally decomposing dioxin is also provided.

Further, the present invention provides a mixing apparatus for mixing incinerated ash from municipal solid waste or industrial waste as a cement raw material, a cement firing apparatus for firing the mixed raw material, and a kiln dust from exhaust gas discharged from the firing apparatus. A collecting device for collecting, a kiln dust collected is subjected to an acid treatment, and a separating device for separating lead products accompanying dioxin from other products, a heating device for heating the lead products to volatilize dioxin, and A dioxin decomposer provided with an introduction device for introducing dioxin into a cement firing device is also provided.

Thus, in the present invention,
Dioxin adhering to the reduced volume of lead products is volatilized and led to a high-temperature cement kiln, where it is completely decomposed.This makes the entire processing unit compact and eliminates the need for new special heat sources. In addition, dioxin can be completely rendered harmless.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the production of so-called eco-cement using conventional municipal waste incineration ash as a recycling resource, the incineration ash that has been subjected to pretreatment such as drying, iron removal, and pulverization is used as a target clinker mineral. Depending on the limestone, calcium chloride or sodium carbonate is prepared and charged to the rotary kiln. The raw material that has entered the kiln is heated to 1300 to 1350 ° C. or higher in a firing zone, becomes clinker, is cooled and then ground together with gypsum, and a setting regulator is added thereto to produce cement. The exhaust gas from the kiln contains chlorine, alkalis, heavy metals and a small amount of cement raw materials volatilized in the rotary kiln. Of these, the cement raw material is included in the coarse particles, so it is removed by a cyclone and charged into the kiln again.

Fine powder not collected by the cyclone (hereinafter referred to as kiln dust) contains heavy metal, chlorine, alkali, undecomposed dioxin derived from incinerated ash, etc., and is collected by a bag filter. The recovered kiln dust is heated by a heating device to a temperature equal to or higher than the decomposition temperature of dioxin to decompose the dioxin, and the remaining heavy metals and the like are further sent to a metal refining device and reduced as lead products or copper products to Yamamoto.

On the other hand, in the present invention, when the kiln dust collected and collected by the bag filter is subjected to heavy metal scouring by an acid treatment method, dioxin is completely transferred to the lead product and concentrated. It has been found that this phenomenon is utilized to perform compact and efficient decomposition of dioxin. Further, the idea of the present invention is not limited to the decomposition of dioxin in kiln dust, but also the decomposition of dioxin in other materials containing dioxin, for example, general incineration ash, industrial waste, and the like. It goes without saying that the present invention can be applied without departing from the above.

The method for acid-treating incinerated ash or kiln dust is not particularly limited as long as it is a usual method for scouring a mixture containing a lead component and a copper component. Generally, an acid-soluble component mainly composed of copper is leached by acid leaching of dust, and a lead component accompanied by dioxin is collected as a residual solid insoluble component by a filter press or the like. The copper component contained in the filtrate is reduced to Yamamoto as a solid copper product through neutralization with sodium hydroxide, sedimentation and separation with sodium hydrosulfide, and the like.

Since the dioxin contained in the kiln dust is all captured in the lead component obtained from the filter press in a concentrated form, the lead product is heated by a heating device at a temperature equal to or higher than the volatilization temperature of dioxin (preferably 600 ° C.).
℃ or more) to evaporate all dioxins. Dioxin has a different melting point and boiling point depending on the number of substituted chlorines.
It is below ° C. Therefore, if gas containing volatile dioxin is blown together with the primary air of the rotary kiln and heated to 1500 ° C. or higher in the rotary kiln, dioxin is completely decomposed.

As described above, in the present invention, even if new incinerated ash is used as a raw material for cement and dioxin comes out of the kiln along with dust from the rotary kiln, the dioxin is collected together with the lead component in the subsequent stage, and is again returned to the rotary kiln. And is decomposed at high temperature,
Dioxin does not accumulate or be released outside the system. The lead product discharged from the heating device is returned to Yamamoto as containing no dioxin.

Hereinafter, a method of incorporating the present invention into an eco-cement manufacturing process using incinerated ash from municipal waste will be described with reference to FIG. In FIG. 1, first,
The incinerated ash that has been subjected to pretreatment such as drying, iron removal, and pulverization,
It is put into the mixing device 1 together with limestone and mixed with air. The prepared raw material is transported to the storage tank 2. Here, the raw materials are measured and charged into the rotary kiln 3 via a screw conveyor (not shown). Depending on the target clinker mineral, calcium chloride or sodium carbonate is added to the raw material from a feeder (not shown) as a raw material conditioner. The raw material that has entered the rotary kiln is heated to 1300 to 1350 ° C. or higher in a firing zone, becomes a clinker, and is cooled by the clinker cooler 4. The cooled clinker 5 is pulverized together with the gypsum, and a setting modifier is added thereto to produce a cement.

From the kiln burner 6, primary air and heavy oil are blown. The air blown from the cooler fan 7
The air that has undergone heat exchange with the clinker, the hot air, the primary air blown from the kiln burner, and heavy oil are mixed and burned. The flue gas exchanges heat with the raw material, drops to about 800 ° C. in the kiln inlet hood, and is further instantaneously cooled to about 400 ° C. by the air blown from the cooling fan 8, and cooled to 280 ° C. or less by water spraying in the cooling tower 9. Cooled. The exhaust gas contains chlorine, alkali, heavy metals and a small amount of cement raw materials that have volatilized in the rotary kiln. Among them, the cement raw material is contained in the coarse particles, so that it is removed by the cyclone 10 and charged into the kiln again.

Since the kiln dust not collected by the cyclone contains heavy metals, chlorine, alkali, dioxin, etc., these are collected by the bag filter 11. The exhaust gas that has passed through the bag filter is released into the atmosphere from the chimney 13 after removing NOx by the exhaust gas treatment device 12.

Kiln dust 1 collected by bag filter
4 enters the next acid treatment device. The dust is first leached in the first leaching tank 15 under sulfuric acid at pH 4 and settles down.
The solution is subjected to solid-liquid separation, and is separated into a solution in which a copper component is dissolved and a solid portion containing lead and Ca. The solid portion is again leached at pH 1 in the second leaching tank 16 again, sedimentation and separation are repeated to separate the copper component as much as possible, and a lead product as a solid residue is obtained by the filter press 17. The copper content contained in the filtrate 18 is reduced to yamamoto as a solid copper product through neutralization with sodium hydroxide, sedimentation with sodium hydrosulfide, separation and the like (not shown).

In the lead product obtained from the separator, the dioxin contained in the kiln dust is all captured in a concentrated form.
9. Heat the dioxin to a temperature equal to or higher than the volatilization temperature of the dioxin (preferably equal to or higher than 600 ° C.) in an externally heated kiln to volatilize all the dioxin. As a heat source for volatilizing the dioxin, heat generated by heat exchange in a cooling unit of the rotary kiln can be used. The gas 20 containing the volatilized dioxin is blown together with the primary air of the burner of the rotary kiln, and is heated to 1500 ° C. or higher in the rotary kiln, and the dioxin is completely decomposed. Dioxin-free lead product 21 discharged from heating device
Is cooled and then returned to Yamamoto.

[0021]

EXAMPLE An example in which cement is actually manufactured using incinerated ash by the manufacturing apparatus shown in FIG. 1, the kiln dust collected by the bag filter is acid-treated, and dioxin accompanying lead products is decomposed by a rotary kiln. Is shown below.
However, this is merely an example, and the present invention is not limited by this example.

43.3% by weight of municipal solid waste incineration ash and 54.5 lime powder each containing the components shown in Table 1 below.
The raw material was fired at 1250-1450 ° C. in a rotary kiln using as raw materials 1.3 wt% of aluminum ash and 0.9 wt% of clay.

[0023]

[Table 1]

The amount of kiln dust recovered by the bag filter 11 is 5 parts by weight with respect to 100 parts by weight of the clinker.
As shown in Table 2, the dioxin content therein was 100 ng per 1000 g of dust. The kiln dust then enters the acid treatment unit. The dust is first leached in the first leaching tank 15 under sulfuric acid at pH 4 and settles down.
Solid-liquid separation was performed, and the liquid was separated into a liquid in which a copper component was dissolved and a solid portion containing lead and Ca components. The solid portion was leached again at pH 1 in the second leaching tank 16 again, sedimentation and separation were repeated to separate the copper as much as possible, and a lead product as a solid residue was obtained by the filter press 17. The copper content contained in the filtrate was reduced to Yamamoto as a solid copper product through neutralization with sodium hydroxide, sedimentation with sodium hydrogen sulfide, separation and the like. Dioxin was no longer detected in this.

The concentrations of dioxin in the lead product and the copper product obtained from the acid treatment apparatus are as shown in Table 2 below, and it can be seen that dioxin has completely migrated to the lead product side. That is, when the mass balance of lead products, copper products, and dioxins was measured before and after the acid treatment of the kiln dust, the results shown in the following Table 2 were obtained.

[0026]

[Table 2]

Since the dioxin contained in the kiln dust is all captured in the lead product obtained from the separator in a concentrated form, the lead product is heated in an externally heated kiln at a temperature equal to or higher than the volatilization temperature of dioxin (600 ° C.). Above) to evaporate all the dioxins. The lead product discharged from the heating device did not contain any dioxin, and after cooling, was reduced to Yamamoto. The gas containing the volatilized dioxin was blown as primary air in the rotary kiln and heated to 1500 ° C. or higher in the rotary kiln, and the dioxin was completely decomposed.

[0028]

As described above, according to the present invention, cement can be produced using municipal waste incineration ash as a raw material, and dioxin, which is a concern due to use of incineration ash, can be completely decomposed. The lead component and copper component contained in these incinerated ash can be reused as useful metal resources.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a dioxin decomposing apparatus in a cement production process according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mixing device 2 storage dunk 3 rotary kiln 4 clinker cooler 5 clinker 6 kiln burner 7 cooler fan 8 cooling fan 9 cooling tower 10 cyclone 11 bag filter 12 exhaust gas treatment device 13 chimney 14 kiln dust 15 first leaching tank 16 second leaching tank 17 filter 18 Filtrate of copper component 19 Heating device 20 Dioxin gas 21 Lead product

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichiro Sato 2-4-2 Daisaku, Sakura City, Chiba Prefecture Inside the Central Research Laboratory, Noda Chichibu Co., Ltd. (72) Tetsuo Oogiri 2-4 Daisaku, Sakura City, Chiba Prefecture No.2 Chichibu Oda Noda Co., Ltd. F-term (reference) 4G012 KA05

Claims (5)

[Claims] 1. A method of heating a material containing dioxin to a temperature equal to or higher than the boiling point of dioxin, introducing a gas containing volatile dioxin into a rotary kiln for sintering cement, and thermally decomposing dioxin by heat during sintering of cement. 2. The method according to claim 1, wherein the dioxin-containing material is reduced in volume and the dioxin is concentrated. 3. When producing incineration using incinerated ash from municipal solid waste or industrial waste as a part of raw materials, a kiln dust containing undecomposed dioxin is collected, and the collected kiln dust is collected by dioxin. A method in which a gas containing dioxin that has been volatilized by heating to a temperature equal to or higher than the boiling point is introduced into a rotary kiln for sintering cement, and the dioxin is thermally decomposed by heat during sintering of the cement. 4. The collected kiln dust is separated into a lead product containing lead as a main component and other components by acid treatment, and dioxin accompanying the lead product is heated to a temperature equal to or higher than the boiling point of dioxin. The method according to claim 3, characterized in that: 5. A mixing device for mixing incinerated ash from municipal solid waste or industrial waste as a cement raw material, a cement firing device for firing the mixed raw material, and a collecting device for collecting kiln dust from exhaust gas discharged from the firing device. An acid treatment of the collected kiln dust to separate lead products accompanying dioxin and other products, a heating device for heating the lead products and volatilizing dioxin,
A dioxin decomposing device, comprising: an introduction device for introducing the volatile dioxin into a cement firing device.