JPH07155731A - Heating dechlorination treatment for collected dust and ash - Google Patents

Abstract

PURPOSE:To prolong the service life of the device and to reduce the running cost by operation the heating treatment device at an appropriate condition. CONSTITUTION:Hexachlorobenzene concentration in collected dust and ash A introduced into a heating pipe 1 and in treated ash B discharged from the heating pipe 1 are detected at specified intervals by an automatic analyzer 5 and the removal ratio of dioxines by the heating device is estimated based on this data and heating conditions of the heating device are adjusted based on the estimated removal ratio. Thus, the service life of the device is prolonged and the running cost is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating and dechlorinating dust collecting ash, and more particularly, to a method for treating exhaust gas discharged from waste incinerators such as municipal waste and industrial waste. Decomposes harmful chlorine compounds such as dioxins (hereinafter referred to as dioxins) contained in the collected dust ash,
The present invention relates to a heating dechlorination treatment method for dust collecting ash to be removed.

[0002]

2. Description of the Related Art Dioxins harmful to the human body and the environment, that is, 4 to 8 chlorinated PCDD _S (polychlorinated dibenzoparadioxin) and 4 to 8 chlorinated PCD.
F _S (polychlorinated dibenzofuran) is known to pollute the environment when it is contained in the exhaust gas and dust ash discharged from the municipal waste incineration treatment facility.

As a measure against this, the national government has decided on December 26, 1990.
Date Ministry of Health and Welfare Bureau Health and Sanitation Bureau Water Environment Department Notification Sanitation Environment No. 260
Comprehensive measures are summarized in the “Dioxins Generation Prevention Guidelines” attached to the issue. According to this guideline, regarding the treatment of danoxins in dust ash, "The ash treatment technology for danoxins such as incineration ash that is finally disposed is (1) heat dechlorination treatment, (2) melt solidification treatment. It is desirable to promote technological development and research, including the behavior of heavy metals, for practical use in the future. ”

As a technique for reducing dioxins in such dust-collected ash, there is, for example, Japanese Patent Laid-Open No. 2-78479 (incinerator ash treatment method and treatment device for a refuse incinerator) proposed by the present inventors. To be According to this treatment method and treatment apparatus, by heating the incinerated ash collected from the refuse incineration treatment facility to 300 ° C. or higher, it is possible to effectively decompose organic chlorine compounds such as dioxins in the ash, and exhaust gas. By providing a heating means in the ash accumulation portion of the dust collector to heat the incinerated ash filled therein, the organic chlorine compounds in the incinerated ash can be almost completely detoxified.

[0005]

However, in the above-mentioned prior art, the decomposition performance of dioxins in the dust collecting ash in the heating device, that is, the change in the concentration of dioxins contained in the dust collecting ash before and after the heat treatment is not monitored. However, the heat treatment device is operated on the safe side, that is, at a higher temperature than necessary for a long average residence time, and there is a problem that the device life is shortened due to high temperature corrosion and the running cost is increased.

By the way, the amount of dioxins in the collected ash is determined by mixing the sampled ash with an organic solvent such as toluene to extract the dioxins, pretreating the extract as necessary, It is carried out using GC / MS (gas chromatography mass spectrometer). For this reason, it took at least one week until the analysis results were obtained, and it was physically impossible to directly monitor the concentration in ash before and after the heat treatment. There is also a problem that such an analysis requires a great deal of cost.

The object of the present invention is to solve the above-mentioned problems of the prior art and to operate the heat treatment apparatus under appropriate conditions capable of decomposing and removing dioxins, thereby prolonging the life of the apparatus and reducing the running cost. Another object of the present invention is to provide a method for heating and dechlorinating dust ash.

[0008]

Means for Solving the Problems The present inventor has noticed that in order to operate the apparatus for thermally dechlorinating dust collecting ash under proper conditions, it is sufficient to monitor the removal rate of dioxins in the heating apparatus. However, as a result of diligent research on the relationship between the concentration of dioxins and the concentration of a specific organic chlorine compound before and after the heat treatment, the removal rate of chlorobenzenes or chlorophenols, which is significantly easier to analyze than dioxins, and the above-mentioned dioxins. It was discovered that there is a strong correlation with the removal rate of dioxin, and at least one of the above chlorobenzenes and chlorophenols was used as an indicator substance, and the change in concentration before and after heating was measured to measure dioxins. Estimate the removal rate, and based on this, control the heating conditions such as the heating temperature of the heating device and the average residence time of ash. It found that prevents extension of the high temperatures and unnecessary residence time of use, have reached the present invention.

Further, the present inventor has noticed that pentachlorobenzene and hexachlorobenzene among the above-mentioned chlorobenzenes have no isomers, and the analysis is easy and accurate, and the dioxins are removed by a heating device. By using it as an indicator substance to monitor the rate,
The inventors have found that the removal rate of dioxins can be estimated quickly and accurately, and have reached the present invention.

That is, the invention claimed in this application is as follows. (1) The dust ash collected in the exhaust gas treatment process of a refuse incineration treatment facility is introduced into a heating device and heated to decompose the dioxins contained in the dust ash by heating and dechlorination. In the method, in the heating device, at least one of chlorobenzenes and chlorophenols contained in the dust collecting ash before the heating treatment at the inlet of the heating device and the dust collecting ash after the heating treatment at the outlet of the heating device is quantified, respectively. A method for thermal dechlorination of dust collection ash, which comprises estimating a removal rate of dioxins and adjusting heating conditions based on the estimated removal rate of dioxins. (2) Heating the dust ash according to (1), characterized in that the removal rate of dioxins in the heating device is estimated by measuring the content of pentachlorobenzene or hexachlorobenzene before and after the heat treatment of the dust ash. Dechlorination treatment method.

[0011]

[Function] The removal rate of dioxins in the heat treatment apparatus can be estimated by quantifying at least one of chlorobenzenes and chlorophenols before and after the heat treatment. Therefore, the estimated removal rate of dioxins can be estimated. By adjusting heating conditions such as heating temperature and ash residence time in the equipment to obtain the desired dioxins removal rate based on the above, unnecessary high temperature and unnecessary extension of residence time are avoided. To be done.

2 and 3 are explanatory views showing the principle of the present invention. FIG. 2 shows the removal rate of hexachlorobenzene and the removal rate of dioxins in the case of heat treating dust collection ash. It is a figure which shows a relationship. FIG. 3 is a diagram showing the relationship between the decomposition rate of hexachlorobenzene and the decomposition rate of dioxins at each heating temperature when the dust ash is also heat-treated.
_The display is divided into _S and PCDF _S. In FIG. 2, the removal rate of hexachlorobenzene and the removal rate of dioxins are almost proportional in the removal rate range of 90 to 99.9%, and the removal rate of dioxins is higher than that of hexachlorobenzene. It tends to be higher than the removal rate. Further, in FIG. 3, the decomposition rate (removal rate) of dioxins is higher than the decomposition rate of hexachlorobenzene, and hexachlorobenzene <PCDF _S <PCDD _S
It can be seen that the decomposition rate increases in the order of. Therefore, from FIGS. 2 and 3, if the removal rate of hexachlorobenzene in the heat treatment apparatus is measured, it is guaranteed that the removal rate of dioxins will be higher than that. Almost the same relationship is observed for chlorobenzene or chlorophenols other than hexachlorobenzene.

As described above, according to the present invention, hexachlorobenzene, which is easy to analyze, is used as an index substance for estimating the removal rate of dioxins, and the removal rate of dioxins is estimated by obtaining the removal rate, Using this as a guide, the operating conditions of the heating device are adjusted to achieve the desired dioxins removal rate. In the present invention, dioxins are a general term for 4-8 chlorinated polychlorinated dibenzoparadioxins (PCDD _S ) and 4-8 chlorinated polychlorinated dibenzofurans (PCDF _S ).

In the present invention, the type of the heat treatment device is not particularly limited as long as it can heat the dust collecting ash, and in addition to the heating pipe system, for example, a horizontal screw, an inclined angle screw, a vertical screw, a multi-tube rotary kiln. Etc. are used. As a heating method, in addition to an electric heater, for example, a heat exchange method with exhaust gas or high-temperature powder, a burner method, a microwave method, or the like is used, but is not particularly limited.

In the present invention, the measurement index substance used to estimate the removal rate of dioxins may be hexachlorobenzene, pentachlorobenzene, other chlorobenzenes, chlorophenols or a combination thereof. As an analyzer for these measurement index substances, for example, a GC / ECD (gas chromatography electron capture detector) is used, but other than this as long as it can quantify chlorbenbenes or chlorophenols in ash However, it is not particularly limited.

In the present invention, the heating temperature of the dust collecting ash is about 50 by substituting the gas phase in the heating pipe with nitrogen or by heating the dust collecting ash by adding, for example, about 5% by weight of slaked lime. Even if the temperature is reduced by -100 ° C, the same dioxins removal rate can be obtained.

[0017]

EXAMPLES Next, the present invention will be described in more detail by way of examples. FIG. 1 is an explanatory diagram of a thermal dechlorination apparatus for dust collecting ash used in an embodiment of the present invention. In this heat treatment apparatus, a heating pipe 1 inclined so that the outlet side is slightly lower than the inlet side, an inlet hood 2 and an outlet hood 3 of the heating pipe 1, and a dust collecting ash A in the heating pipe 1. A constant quantity feeder 6 to be introduced and a heating device 7 for heating the heating pipe 1.
And a drive device 8 for rotationally driving, an automatic analyzer 5 for detecting the amount of hexachlorobenzene in the treated ash B provided at the outlet of the outlet hood 3 for discharging the treated ash B subjected to heat treatment, and a subsequent flow Sealing device 4 and obtained treated ash B
Based on the amount of hexachlorobenzene in the powder and the amount of hexachlorobenzene in the dust ash A detected in advance, the removal rate of hexachlorobenzene is determined, and the removal rate of dioxins is estimated based on the determined removal rate. Mainly comprises a control device 12 for controlling the heating temperature and the rotation speed of the heating device 7 and the driving device 8, respectively. In addition, 9 and 10 are temperature detectors, and 11 is an exhaust fan.

In such a configuration, the constant quantity supply device 6
The dust-collected ash A discharged by means of the inlet hood 2 is slightly inclined toward the outlet side, and is introduced into the heating pipe 1 rotated by the drive device 8 and heated by the heating device 7 in the heating pipe to a predetermined extent. After passing through the residence time of 1, the dioxins such as PCDD _S and PCDF _S contained in the dust collecting ash A are decomposed and transferred into the gas phase during this time. The decomposed gas generated by decomposition is separated from the treated ash B, and then flows out of the outlet hood 3, and the blower 11
After that, the ash gas C is extracted to the outside of the apparatus, and is introduced into the upstream of the dust collecting apparatus of the exhaust gas processing apparatus of the refuse incineration processing facility for separate processing. On the other hand, the dust collecting ash from which the dioxins have been decomposed and removed is separated from the decomposed gas by the outlet hood 3, and then discharged as a treated ash B through the sealing device 4 to the outside of the system. At this time, the hexachlorobenzene concentration in the treated ash B is continuously detected at a predetermined interval by the analyzer 5 arranged in the upstream side of the sealing device 4, and the signal is sent to the controller 12. The control device 12, which has received the hexachlorobenzene concentration signal in the treated ash B, uses the detection value and the hexachlorobenzene concentration of the dust collecting ash A at the inlet of the heating device determined in advance to remove the hexachlorobenzene in the heating device. Then, the removal rate of dioxins is estimated from the removal rate, and if the estimated removal rate of dioxins is lower than the target removal rate, raise the heating temperature or decrease the inclination angle of the heating tube. Alternatively, a signal is sent to the heating device 7, the driving device 8 and the inclination angle changing means (not shown) of the heating tube 1 so as to increase the residence time by reducing the number of rotations and improve the removal rate. On the other hand, if the estimated removal rate is higher than the target removal rate, lower the heating temperature, or increase the heating tube inclination angle or increase the heating tube rotation speed, Shorten the residence time to relax the heating conditions.

According to the present embodiment, the concentration of hexachlorobenzene in the treated ash B at the outlet of the heat treatment device is monitored, and from this and the concentration of hexachlorobenzene at the inlet of the heat device determined in advance, the dioxin content in the heater is determined. By estimating the removal rate and adjusting the heating conditions of the heating device based on this, it is possible to eliminate unnecessary high-temperature heating and prevent unnecessary extension of the residence time. Therefore, not only dioxins in the dust collection ash can be decomposed at a desired removal rate, but also the life of the device can be extended and the running cost can be reduced.

In the present embodiment, the average residence time of the ash to be treated in the heating device is controlled by adjusting the rotation speed and the inclination angle of the heating tube 1. The tilt angle of the heating tube is adjusted by a known method such as increasing the tilt angle with a hydraulic cylinder. In this embodiment, as an analyzer for hexachlorobenzene in the treated ash B, for example, GC /
ECD (Gas Chromatography Electron Capture Detector) is used and its quantification is performed as follows. That is, a fixed amount of the treated ash B, for example, 5 g is taken and mixed with about 10 ml of acetone to extract hexachlorobenzene as a target component. Then, a part of the extract, for example 5 μl, is introduced into the GC / ECD and quantified using, for example, a capillary column. The time required for analysis of one sample is 2 to 30 minutes.

In the present embodiment, the concentration of hexachlorobenzene in the treated ash B after the heat treatment is monitored, and based on this and the concentration of hexachlorobenzene in the collected dust ash A before the heat treatment, the heating device The removal rate of dioxins was estimated. For example, the automatic analysis device 5 was arranged between the constant amount supply device 6 and the heating device 1, and the dust collection ash A
It is also possible to monitor the hexachlorobenzene concentration in the same manner as the concentration in the treated ash B, and estimate the removal rate of dioxins from the concentrations at the inlet and the outlet that are continuously detected at predetermined intervals.

Next, specific examples of the present invention will be described. Using the device in Fig. 1 inclined at 5 ° on the outlet side, the treatment rate is 100 kg / h for the purpose of decomposing and removing 99% of dioxins.
The bag filter ash discharged from the municipal solid waste incineration facility was heat-treated with an average residence time of 10 min.
The hexachlorobenzene concentration in the treated ash B flowing out of the outlet hood 3 was detected every 10 minutes, and the hexachlorobenzene concentration in the treated ash B obtained and the hexachlorobenzene of the dust collecting ash A before the heat treatment obtained in advance were detected. Concentration (28 ng /
The removal rate of hexachlorobenzene in the heating device was calculated from g), and the removal rate of hexachlorobenzene was 9%.
If it is lower than 5%, set the heating pipe tilt angle to 3
And the average residence time was about 20 minutes, the removal ratio of hexachlorobenzene was maintained at 95% or more, and heat dechlorination treatment was performed. At this time, the heating temperature of the heating pipe 1 is about 450.
The temperature was 6 ° C and the rotation speed was 6 rpm.

The test results are shown in Table 1.

[0024]

[Table 1]

From Table 1, it can be seen that the removal rate of dioxins was stably 99% or more. According to the present example, in order to obtain the removal rate of dioxins of 99% or more, the same dioxins removal rate can be achieved at the heating temperature of 400 to 500 ° C, which has been heat treated at about 500 ° C. Therefore, high temperature corrosion of the heating pipe can be prevented and the life of the device can be extended. Further, along with this, the run cost can be significantly reduced.

[0026]

According to the invention of claim 1 of the present application, the removal rate of dioxins in the heating device is determined by quantifying at least one of chlorobenzenes and chlorophenols in the ash at the inlet and outlet of the heating device. By adjusting the heating conditions by this,
Since the removal rate of dioxins in the heating device can be monitored, it is possible to prevent an unnecessary increase in heating temperature or an unnecessary extension of the residence time.
Therefore, high temperature corrosion can be prevented and the life of the apparatus can be extended, and running costs can be significantly reduced.

According to the invention of claim 2 of the present application, by using pentachlorobenzene or hexachlorobenzene, which is free of isomers and is easy to analyze, as an index substance for estimating the removal rate of dioxins, In addition to the effects of the invention, the removal rate of dioxins can be quickly and accurately monitored.

[Brief description of drawings]

FIG. 1 is an explanatory view of a thermal dechlorination apparatus used in an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the principle of the present invention.

FIG. 3 is an explanatory diagram showing the principle of the present invention.

[Explanation of sign]

1 ... Heating tube, 2 ... Inlet hood, 3 ... Outlet hood, 4 ... Sealing device, 5 ... Hexachlorobenzene automatic analyzer,
6 ... Fixed amount supply device, 7 ... Heating device, 8 ... Driving device, 9 ...
Temperature detector, 10 ... Temperature detector, 11 ... Exhaust fan, 12 ...
Control device.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI technical display location F23G 7/00 103 Z 9430-3K (72) Inventor Hiroshi Kudo 1-6 Osaki, Shinagawa-ku, Tokyo No. 1 Sanzo Kankyo Engineering Co., Ltd. (72) Inventor Gentaro Takasuka No. 1 Hachiman Kaigan Dori, Ichihara City, Chiba Prefecture Mitsui Engineering & Ships Co., Ltd. Chiba Works No. 1 Mazumi Itaya No. 1 Hachiman Kaido Dori, Ichihara City, Chiba Prefecture Mitsui Shipbuilding Co., Ltd. Chiba Works

Claims (2)

[Claims] 1. A thermal dechlorination of dust ash which introduces dust ash collected in an exhaust gas treatment step of a refuse incineration treatment facility into a heating device to heat it and decomposes dioxins contained in the dust ash. In the chemical treatment method, at least one of chlorobenzene and chlorophenol contained in the dust-collected ash before the heat treatment at the inlet of the heating device and the dust-collected ash after the heat treatment at the outlet of the heating device is quantified and the heating is performed. A method for heating and dechlorinating dust-collecting ash, which comprises estimating a removal rate of dioxins in an apparatus and adjusting heating conditions based on the estimated removal rate of dioxins. 2. The dust collection ash according to claim 1, wherein the removal rate of dioxins in the heating device is estimated by measuring the pentachlorobenzene or hexachlorobenzene content before and after the heat treatment of the dust collection ash. Method for thermal dechlorination of.