JP2001286846A - Method and device for treating chlorine compounds in incinerated ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for treating chlorine compounds in incineration ash, by which unburned substrates such as dioxins or dioxin precursors contained in the incineration ash, incineration fly ash or the like are highly decomposed. SOLUTION: Organic chlorine compounds such as unburned substances being dioxins and dioxin precursors adsorbed on or contained in the incineration ash, incineration fly ash or the like are decomposed in a molten salt (reactor) composed of two or more alkaline metal carbonates selected from sodium carbonate, potassium carbonate and lithium carbonate and one or more alkali nitrates selected from sodium nitrate, potassium nitrate and lithium nitrate, and then the molten salt is removed from the incineration ash or the incineration fly ash by washing (by shower).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for oxidizing organic chlorine compounds such as dioxins adsorbed or contained in incinerated ash or incinerated fly ash and unburned substances as a dioxin precursor. It is.

[0002]

2. Description of the Related Art As a method for treating dioxins adsorbed or contained in incinerated ash and incinerated fly ash, and organic chlorine compounds such as unburned substances as a dioxin precursor, the Haugenmeier method (Germany) and the like are practically used. Has been

[0003]

The above-mentioned methods put into practical use are all kiln systems using indirect heating.
The heat treatment is performed at a temperature in the range of 00 to 500 ° C. Various methods have been devised to almost completely decompose the chlorine compound and to shorten the preheating time from room temperature to the heat treatment temperature. However, at present, there is a limit in shortening the preheating time because each method is an indirect heating method.

[0004] The present invention overcomes the above-mentioned disadvantages of the prior art and solves the problem of incineration ash which is highly decomposed to decompose dioxins adsorbed or contained in incineration ash or incineration fly ash and unburned substances as dioxin precursors. It is an object of the present invention to provide a method and an apparatus for treating a chlorine compound.

[0005]

In order to achieve the above object, a method for treating a chlorine compound according to the present invention comprises the steps of:
Incineration ash or incineration fly ash in a molten salt consisting of two or more alkali metal carbonates selected from potassium carbonate and lithium carbonate and one or more alkali nitrates selected from sodium nitrate, potassium nitrate and lithium nitrate Soak,
It decomposes organic chlorine compounds such as dioxins adsorbed on or contained in the incinerated ash or incinerated fly ash and unburned substances as dioxin precursors.

The temperature for the decomposition treatment is not particularly limited, but it is possible to maintain the temperature in the range of 400 to 600 ° C., to blow in an oxygen-containing gas such as air, and to perform stirring of the molten salt and oxygen supplementation.

In order to achieve the above object, a chlorine compound treating apparatus according to the present invention comprises two or more alkali metal carbonates selected from sodium carbonate, potassium carbonate and lithium carbonate, and sodium nitrate, potassium nitrate and lithium nitrate. A closed reaction vessel for containing a molten salt comprising at least one selected alkali nitrate, and a plurality of through-holes which cannot pass through the incineration ash or incineration fly ash and which can pass the molten salt; A conveyor in which containers are continuously attached, incineration ash or incineration fly ash is accommodated in the containers, the incineration ash is installed so as to pass through the molten salt and then pass through a washing device, and the molten salt treatment is completed. Alternatively, the molten salt adhering to the incineration fly ash is washed and removed.

The time for treating the incineration ash and / or incineration fly ash in the conveyor with the molten salt, that is, the residence time, is usually sufficient within 30 minutes, but is absorbed or contained in the incineration ash or incineration fly ash. The residence time of the incinerated ash and / or incinerated fly ash is adjusted in consideration of the composition and temperature of the molten salt depending on the content of organic chlorine compounds such as dioxins and unburned substances as a dioxin precursor. This adjustment time can be generally in the range of 5 to 120 minutes.

Nitrate has a strong oxidizing power and plays a leading role in the oxidative decomposition of organic chlorine compounds, but involves a danger such as explosion. Mixing sodium carbonate, potassium carbonate and lithium carbonate with the mixed alkali carbonate to avoid danger while adsorbing or contained in incinerated ash and / or incinerated fly ash, unburned as a dioxin precursor Organic compounds can be decomposed to a high degree.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in more detail.

As described above, the melting points of the two or more kinds of alkali metal carbonates are all 600 ° C. or more.
By mixing more than one species, it can be reduced to below. In particular, by mixing three types, the melting point can be lowered to about 400 ° C. In this case, the melting point can be lowered by setting the mixing ratio to a value closer to the equivalent amount, but the present invention is not limited to these.

It is not preferable to set the temperature too high for reasons such as safety and economy. Generally, the decomposition treatment temperature in the range of 400 to 600 ° C. is appropriate as described above.
In addition, the alkali metal nitrate can be mixed up to about 40% by weight based on the total amount of the carbonate mixture and the nitrate mixture.

Since the molten salt has a large heat capacity, the time required for heating the incinerated ash and / or fly ash to about 500 ° C. in the molten salt is extremely short. Therefore, it is possible to prevent the organic chlorine compound from being scattered in the gas phase during the preheating, and to completely oxidatively decompose in the molten salt.

Most of the harmful chlorine gas generated by the oxidative decomposition is trapped in the molten salt as chloride, so that the chlorine gas concentration in the oxidative decomposition gas is extremely low, and a simple cleaning device for the decomposition gas is used. It can be removed by alkali washing.

The incinerated ash and / or fly ash taken out of the molten salt can be recovered in a hopper or the like as safe treated ash after the salt attached to the surface is washed off with washing water such as industrial water. Further, the washing water after washing can be used as the oxidative decomposition gas washing water, and the finally used washing water can be treated by a water treatment facility.

It is preferable that the speed of the conveyor is low, and that the molten salt sufficiently penetrates the incineration ash and / or fly ash. Therefore, the incineration ash carried on the conveyor and / or
Alternatively, the moisture contained in the incineration fly ash evaporates in the process of being preheated to about 100 to 150 ° C., but it is possible to avoid the possibility that the evaporation is concentrated and a steam explosion occurs. In particular, when the oxygen-containing gas such as the air is used in combination with the blowing means, it is preferable from the viewpoint of safety because the gas can be easily released from the molten salt as bubbles by stirring by blowing the gas.

Next, an apparatus for treating chlorine compounds in incinerated ash according to an embodiment of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, a reaction vessel 1 (molten salt bath)
Is provided with an electric heater 2 and a heated air (oxygen-containing gas) at the lower part thereof, and a sizzle 3 at the lower part thereof.
A gas passage 4 for discharging the decomposition gas and the heated air is provided, and at a side wall of the upper space 6 of the molten salt 5, there are provided two entrances 8 at which a conveyor 7 penetrates through the reaction vessel 1 and enters and exits. As an industrial means, the electric heater 2 can be changed to another heating means.

The conveyor 7 is for transporting incinerated ash and / or incinerated fly ash (hereinafter referred to as incinerated ash / incinerated fly ash). It is arranged to run between the cleaning device 10 and the hopper 11 that receives the processing ash. Then, in the reaction vessel 1, in order to travel between the molten salt 5 and the space 6 above the molten salt 5, as shown in FIG.
It is installed so as to be guided to be.

The conveyor 7 can be formed by continuously attaching basket-shaped containers for accommodating untreated incinerated ash and incinerated fly ash in an endless track, for example. The basket-shaped container is made of a fine-meshed stainless steel net that does not allow incineration ash and incineration fly ash to pass through, and is provided with a lid that can be opened and closed and lockable (both are not shown). ). When the conveyor 7 is passed through the reaction vessel 1, toxic substances such as chlorine gas due to an oxidative decomposition reaction may leak from the entrance 8 to the outside. However, as described above, since the amount of toxic gas is small, it is possible to prevent the toxic gas from being scattered from the entrance 8 by keeping the space 6 of the reaction vessel 1 at a negative pressure gas.

The washing device 10 sprays washing water from the shower 12 placed on the conveyor 7 that has exited the reaction vessel 1 onto the conveyor 7 to wash the treated incinerated ash and incinerated fly ash, and drains the washing wastewater. The collected water is collected in a pit 13 and transported to a wastewater treatment device (not shown) by a cleaning water transfer pump 14.

The incinerated ash and incinerated fly ash that have been washed are discharged from the conveyor 7 to the hopper 11 and sent to a predetermined disposal site (both not shown) by a truck or the like. In addition, the decomposition gas and the exhaust gas such as heated ventilation are supplied to the gas passage 4.
Through a scrubber (not shown). As described above, the harmful components in the exhaust gas are mainly chlorine gas, and the generated chlorine gas is captured as chloride in the molten salt column, so the chlorine gas concentration in the exhaust gas is extremely low, and simple alkaline cleaning is performed. Can be removed.

The opening and closing of the lid between when the conveyor 7 receives the incineration ash and the incineration fly ash supplied from the receiving hopper 9 and when the treated incineration ash and the incineration fly ash are supplied to the hopper 11 are performed according to this kind. It can be performed by a commonly used automatic opening and closing device.

The traveling speed of the conveyor 7 is such that water contained when incinerated ash and incinerated fly ash enter the molten salt 5 does not suddenly evaporate, does not cause steam explosion, and oxidative decomposition occurs as quickly as possible. What is necessary is just to determine the progress speed according to actual.
The structure of the conveyor is not limited to the above-described embodiment and may be appropriately modified as long as the structure does not allow incinerated ash and incinerated fly ash to escape from the conveyor into the molten salt.

Hereinafter, the present invention will be described more specifically with reference to a laboratory scale example.

Example 1 In a 1-liter stainless steel container equipped with an air supply nozzle in the lower part, a mixed salt of sodium carbonate, potassium carbonate and lithium carbonate and sodium nitrate in an equal weight ratio of 85% by weight: 15 % By weight and heated by an electric heater from the outer wall of the container to 550 ° C.
And heated air at 400 ° C from the lower nozzle to 3 ml
/ Second. At this time, the capacity of the molten salt is 6
It was 00 ml. Next, 50 gr of incinerated ash [stoker furnace main ash: unburned portion = 4.1%, moisture = 8.2%, dioxin = 2.4 ng-TEQ (toxicity) was placed in a stainless steel net basket provided with a thermocouple. (Conversion index) / g], and the basket was put into a molten salt. 1 minute incineration ash in 3 minutes
Heated to 50 ° C and reached 500 ° C in 10 minutes. After holding for 5 minutes, the basket was taken out of the molten salt, and the treated incinerated ash was washed with water and analyzed for dioxin in the hexane extract. The dioxin concentration of the treated ash was 0.01 ng.
−TEQ / g, which was significantly lower than the environmental standard. The unburned carbon amount was reduced to 10 ppm.

Example 2 In a 1-liter stainless steel container provided with an air supply nozzle at the lower part, a mixed salt of sodium carbonate, potassium carbonate and lithium carbonate and sodium nitrate in an equal weight ratio of 85% by weight: 15 % By weight and heated by an electric heater from the outer wall of the container to 550 ° C.
And heated air at 400 ° C from the lower nozzle to 3 ml
/ Second. The volume of the molten salt at this time is 600 ml
Met. Next, 50 gr of incinerated fly ash (stoker furnace main ash: unburned portion = 1.2%, moisture = 10.1%, dioxin = 3) was placed in a stainless steel net basket provided with a thermocouple.
1 ng-TEQ / g) and the basket was poured into the molten salt. The incineration ash was heated to 170 ° C. in 3 minutes and reached 500 ° C. in 9 minutes. After holding for 5 minutes, the basket was taken out of the molten salt, and the treated fly ash was washed with water and analyzed for dioxin in the hexane extract. The dioxin concentration of the treated ash was 0.12 ng-TEQ / g. The unburned carbon amount was 5 ppm.

[0028]

As described above, in the method for treating chlorine compounds in incinerated ash according to the present invention, incinerated ash and / or fly ash is treated in the molten salt described above. Prevents chlorination and / or incineration fly ash from dispersing into the gas phase during preheating of ash and / or incinerated fly ash, and also prevents water vapor contained in dioxins or dioxin precursors from causing water vapor explosion in a short period of time. While it can be removed from the incinerated ash and / or fly ash as quickly as possible, and the amount of chlorine contained in the decomposed gas due to oxidative decomposition is small, it can be removed by simple operations such as alkali cleaning. It can be removed, and the salts attached to the incineration ash and / or fly ash recovered from the molten salt can be easily washed away with water. That.

Further, as described above, the apparatus for treating chlorine compounds in incinerated ash of the present invention can continuously treat incinerated ash and / or fly ash.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of an apparatus for treating chlorine compounds in incinerated ash according to one embodiment of the present invention.

[Explanation of symbols]

 1 Closed-type reaction vessel 5 Molten salt 7 Conveyor 10 Cleaning device

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C07D 319/24 B09B 3/00 303L F-term (Reference) 2E191 BA12 BC01 BD11 4D004 AA36 AA37 AB07 CA24 CB04 CB32 CB42 CB43 CB46 CC11 CC12 DA01 DA03 DA06 DA10 4H006 AA02 AC13 AC26 BA02 BA32 BA34 BC10 BC19 BE30

Claims (4)

[Claims] 1. A molten salt comprising two or more alkali metal carbonates selected from sodium carbonate, potassium carbonate and lithium carbonate and one or more alkali nitrates selected from sodium nitrate, potassium nitrate and lithium nitrate. Incineration ash or incineration fly ash immersed in the incineration ash or incineration ash adsorbed or contained in the incineration ash or incineration fly ash to decompose organic chlorine compounds such as unburned substances as dioxins and dioxin precursors Method for treating chlorine compounds inside. 2. The temperature for the decomposition treatment is 400 to 600.
The method for treating chlorine compounds in incinerated ash of chlorine-based harmful substances according to claim 1, wherein the temperature is kept in a range of ° C and an oxygen-containing gas is blown. 3. A molten salt comprising at least two alkali metal carbonates selected from sodium carbonate, potassium carbonate and lithium carbonate and at least one alkali nitrate selected from sodium nitrate, potassium nitrate and lithium nitrate. An incineration ash, which is provided with a closed reaction vessel into which the incineration ash or incineration fly ash cannot pass, and a conveyor having a plurality of containers having a plurality of through-holes large enough to allow the molten salt to pass through, is provided in the vessel. Alternatively, the incineration fly ash may be accommodated and passed through the molten salt, and then installed so as to pass through a cleaning device, so that the molten salt that has been subjected to the molten salt treatment or the molten salt attached to the incineration fly ash is washed and removed. For treating chlorine compounds in incinerated ash. 4. The apparatus for treating chlorine compounds in incinerated ash according to claim 3, wherein the time for treating the incinerated ash or incinerated fly ash in the molten salt is 5 to 120 minutes.