JP2000343058A - Treatment of harmful matter and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and continuously decompose pyrolytically and detoxify harmful matter without being influenced by the operation of an electric furnace and also by using the high temp. molten slag which had been conventionally discarded at the operation of the electric furnace as a high temp. ignition source containing oxygen and as a combustion/decomposition reaction accelerator containing the fine metal, caustic lime acting as cocatalyst. SOLUTION: In the method, the high temp. molten slag S being the waste of the electric furnace is taken out from the electric furnace 10 in operation and charged into a decomposition furnace 20, and contaminated soil is charged into the decomposition furnace 20 holding the high temp. molten slag S to subject to pyrolysis. Previously to the charge of the contaminated soil into the decomposition furnace 20, waste plastic is incorporated in the contaminated soil as the combustible waste required to keep the temp. for melting the contaminated soil. The harmful matter such as harmful gas leaked from the electric furnace 10 and the decomposition furnace 20 is decomposed at a high temp. decomposition chamber 30 to convent to harmless gas. High temp. gas is supplied to the decomposition furnace 20 and the high temp. decomposition chamber 30 to control the temp. so that the decomposition furnace 20 and the high temp. decomposition chamber 30 may be kept at a high temp. capable of detoxifying the harmful matter such as harmful gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to dioxin-contaminated soil and ash, or waste solvents, waste pesticides or
The present invention relates to a method and an apparatus for treating harmful substances which decompose harmful substances such as contaminated soil contaminated with waste solvents and waste pesticides or medical wastes by thermal decomposition.

[0002]

2. Description of the Related Art Rotary kilns, I.R.
SV (vitrification) equipment, scrap (iron scraps such as steel scraps)
An electric furnace for melting is used. For example, in the case of the electric furnace, harmful substances are directly injected (blown) into high-temperature molten steel in which scrap is melted, or are injected together with scrap. High temperature pyrolysis is being performed.

[0003]

However, the conventional high-temperature pyrolysis treatment as described above requires a lot of heat energy to create a high-temperature field, running costs are high, and the use of heat-resistant materials and equipment However, because of the large size, there is a problem that the equipment cost is high. In addition, in the high-temperature pyrolysis treatment using the electric furnace, it is necessary to take into consideration the effect on products because, for example, harmful substances are put into molten steel in which scrap is melted in a normal operation operation, and the effect on products must be taken into account. (Input amount) and the object to be treated are limited.

[0004] Further, in the melting of scrap by the above-mentioned electric furnace, since a predetermined amount of scrap cannot be put into the electric furnace at a time because the volume of the scrap is large, the amount of scrap to be melted (charged) must be reduced. For each cycle, for example, initial loading (loading of a predetermined amount at the initial stage of the start of scrap melting), additional loading 1
(Additional scrap charging 1) and additional loading 2 (additional scrap charging 2) are performed separately.

[0005] In an electric furnace using such a scrap melting method, scrap reloading is performed when the initial scrap has reached a substantially stable melting temperature. Since the supply of electricity to the furnace has to be temporarily stopped and the supply port of the electric furnace upper lid must be opened, the heating source is eliminated and external air flows in. In addition, since the additional heat from the upper portion of the new scrap removes the retained heat of the dissolving layer of the lower initial scrap, the temperature of the mixture decreases. Due to these factors, the temperature inside the electric furnace (melting temperature, exhaust gas temperature) temporarily decreases. Therefore, the temperature inside the electric furnace fluctuates during the operation of the electric furnace.

Accordingly, when a harmful substance is introduced into molten steel in an electric furnace for decomposition treatment, melting in the electric furnace is almost complete in order to prevent harmful undecomposed substances (eg, dioxin) from being discharged to the outside. When the melting state is reached and the furnace temperature is high (for example, 85
(Temperature of 0 ° C. or more). For this reason, the processing time and processing timing of the harmful substances are limited, and the input processing management is complicated, and it is difficult to process a large amount of waste.

When the harmful substance is put into an electric furnace together with the scrap for decomposition treatment, when the furnace temperature is lower than or equal to a predetermined temperature, the harmful substance of the undecomposed substance is harmful. There is a risk that harmful substances such as gas will be discharged out of the furnace together with the gas. For example, when the temperature in the furnace falls to 850 ° C. or less, there is a risk that dioxin is not decomposed and is discharged outside the furnace.

[0008] Furthermore, in the method of throwing harmful substances into the scrap melting electric furnace and treating them, basically, the treatment target is, for example, a syringe needle or old iron collected in an iron container as medical waste. Harmful substances mainly composed of iron (Fe), such as waste contained therein, are mainly used, and harmful substances containing substances that change the main component of molten steel are not preferable as target objects. Further, when treating other harmful substances, for example, contaminated soil, etc., only the amount of slag as waste increases, and from these points, the type of the object to be treated is also limited. In the operation of the electric furnace, the high-temperature molten slag is taken out of the electric furnace by tilting the electric furnace a predetermined time before one cycle of melting of the scrap ends, and is discarded, and its high retained heat is also discarded.

The present invention has been made in view of the above-mentioned problems of the conventional method for treating harmful substances, and the electric furnace performs the ordinary steelmaking operation and uses the electric furnace for treating harmful substances. In addition, equipment costs related to harmful substance processing can be reduced, and the processing target and processing amount can be freely determined without being affected by the operation of the electric furnace. Newly required energy is consumed by effectively using the high-temperature molten slag that has been used as a high heat source (ignition source) and / or by using flammable waste to maintain the temperature required to dissolve harmful substances. It is an object of the present invention to provide a method and an apparatus for treating harmful substances, which can reduce the amount of the harmful substances, reduce the operating cost, and stably and continuously decompose harmful substances to make them harmless.

[0010]

In order to achieve the above object, the method and apparatus for treating harmful substances according to the present invention employ the following constitution.

(1) As a method of treating harmful substances, a step of taking out high-temperature molten slag as waste from an electric furnace in operation and putting it into a cracking furnace; And thermally decomposing the material. (2) In the method for treating harmful substances according to the above (1), the flammability required for maintaining the harmful substances at a temperature necessary for dissolving the harmful substances prior to the step of charging the harmful substances into the decomposition furnace. The configuration is further provided with a step of mixing waste. (3) In the method for treating harmful substances according to the above (1) or (2), exhaust gases from the electric furnace and the decomposition furnace are introduced into a high-temperature decomposition chamber, and harmful substances such as harmful gases leaked from the electric furnace or the decomposition furnace. Was further decomposed in a high-temperature decomposition chamber to render it harmless. (4) In the method for treating harmful substances according to the above (3), a high-temperature gas is supplied to the decomposition furnace and the high-temperature decomposition chamber, respectively, so that the decomposition furnace and the high-temperature decomposition chamber can be rendered harmless such as harmful gases. The configuration further includes a step of controlling the temperature so as to maintain the predetermined high temperature.

(5) As an apparatus for treating harmful substances, an electric furnace and a high-temperature molten slag generated in the electric furnace are charged, and a harmful substance is charged into the charged high-temperature molten slag. And a decomposition furnace that is thermally decomposed. (6) In the apparatus for treating harmful substances according to the above (5), the electric furnace and the cracking furnace are connected to the electric furnace exhaust gas pipe and the cracking furnace exhaust gas pipe, respectively. The system is further provided with a high-temperature decomposition chamber for detoxifying substances. (7) In the apparatus for treating harmful substances according to the above (6), a high-temperature gas supply source is connected to and provided for the decomposition furnace and the high-temperature decomposition chamber, respectively. A configuration is further provided with a temperature control device that maintains a predetermined high temperature that can be made harmless.

[0013]

According to the constitutions of (1) and (5), for example, scrap generated from an electric furnace such as an electric arc furnace during melting operation using scrap or the like as a melting material is generated as the melting material such as scrap is melted. Is a high-temperature molten slag having a temperature of, for example, 1500 ° C. [slag (ac, noro) floating above the molten layer at the time of melting and also called a molten salt slag]
Immediately before one cycle of melting is completed, it is taken out and put into a cracking furnace.

The method of charging slag from the electric furnace to the cracking furnace is, for example, by moving the cracking furnace to a position close to the electric furnace and positioning it in the vicinity of the electric furnace, for example, by installing the cracking furnace on a truck traveling on rails. The furnace is tilted and the slag floating above the melting layer of the electric furnace is taken out through an outlet (also used as a peep hole and an oxygen injection hole) provided on the furnace wall of the upper part of the electric furnace, and is transferred to the decomposition furnace. A replacement method is adopted.

Oxygen is blown into the cracking furnace to burn the harmful substance itself as an object to be treated and to burn combustible waste previously mixed with the harmful substance, and to prevent the temperature of the molten slag from lowering. Is done. The molten slag introduced into the cracking furnace is at a high temperature equivalent to that taken out of the electric furnace, for example, 150 ° C.
It is kept constant at 0 ° C. and kept in a cracking furnace.

[0016] In such a state, the high-temperature molten slag held in the cracking furnace is contaminated with dioxin or the like contaminated soil or ash, or waste solvent, waste pesticide, or these waste solvents.
Contaminated soil contaminated with waste pesticides, medical waste, etc.
Harmful substances (hazardous wastes) are introduced, and the harmful substances are instantaneously thermally decomposed by the high temperature, and harmful substances such as dioxin are rendered harmless.

[0017] In the decomposition treatment by introducing harmful substances into the decomposition furnace, the reactivity of the molten high-temperature slag is effectively used. That is, in an electric furnace for melting scrap, in order to produce high-quality iron, quicklime (CaO) is supplied into the scrap, phosphorus is removed (P), desulfurization (S) is performed, and oxygen gas is supplied. Is oxidized and removed as slag. Therefore, a large amount of high-temperature molten slag is generated and a large amount of oxygen is present in the high-temperature molten slag.
In addition, there is naturally a fine metal in a predetermined amount or more, for example, 20% by weight or more. Therefore, the high-temperature molten slag can be used as a high-temperature ignition source containing oxygen and as a combustion / decomposition reaction accelerator containing fine metal and quick lime that act as a promoter.

When a flammable harmful substance such as a waste solvent or contaminated soil contaminated with the waste solvent is put into the high-temperature molten slag as an object to be treated, a high-temperature ignition source of the high-temperature molten slag is introduced. As a result, harmful substances such as the combustible waste solvent are easily ignited, burned by oxygen separately supplied to a decomposition furnace, and thermally decomposed. In the combustion and thermal decomposition of this harmful substance, the metal ions and quick lime of the high-temperature molten slag serve as co-catalysts to efficiently promote the oxidation (combustion) reaction of combustible substances and the decomposition reaction of harmful substances. Is done.

The type of harmful substance to be treated in this decomposition treatment is not limited. By effectively using the above-mentioned characteristics of the high-temperature molten slag that was previously discarded in the electric furnace, the slag inside the cracking furnace is maintained at a substantially constant high temperature, so that the change in the furnace temperature due to the operating conditions of the electric furnace is affected. The harmful substances are subjected to thermal decomposition treatment alone.

In the configuration of the above (2), prior to charging the harmful substance into the cracking furnace, a flammable waste such as waste plastic is mixed with the harmful substance in advance as a calorie adjusting material. If the object to be treated is a non-flammable harmful substance, for example, if it is contaminated soil, etc., the temperature of the mixture of the existing high-temperature molten slag and newly added harmful substance in the cracking furnace sharply decreases And the slag is maintained at the temperature required to dissolve harmful substances. That is, the high-temperature molten slag effectively acts as a high-temperature ignition source for combustible waste such as the waste plastic, and the combustible waste is ignited and burns by oxygen supplied separately to the decomposition furnace, thereby melting the slag. The slag is kept at a high temperature required for dissolving the contaminated soil and decomposing the harmful substances contained therein, for example, a predetermined high temperature of 1500 degrees. Also in this combustion and decomposition, the metal ions and quick lime of the high-temperature molten slag serve as co-catalysts, and the reactions such as the oxidation (combustion) reaction of combustibles and the decomposition reaction of harmful substances are efficiently promoted.

In the above configuration (3) or (6), the exhaust gas discharged from the electric furnace and the decomposition furnace is introduced into the high-temperature decomposition chamber, and the harmful gas such as harmful gas leaked from the electric furnace or the decomposition furnace in the high-temperature decomposition chamber. Since detoxifying harmful substances, fluctuations in the electric furnace exhaust gas temperature due to fluctuations in the internal temperature of the electric furnace cause unresolved harmful substances such as dioxins contained or entrained in scraps to be generated in the electric furnace, Even if unresolved substances of harmful substances such as dioxin are generated from the decomposer, the unresolved substances (dioxin, fine solids) may be hindered by the decomposition furnace due to temperature decrease due to some factor. Can be detoxified in the high-temperature decomposition chamber. In this case, the high-temperature exhaust gas of the decomposition furnace is used to maintain the temperature of the high-temperature decomposition chamber at a predetermined high temperature.

In the constitution (4) or (7), a high-temperature gas is supplied from a high-temperature gas supply source such as an auxiliary furnace to the decomposition furnace and the high-temperature decomposition chamber, respectively. Since the temperature is controlled to a predetermined high temperature that can make harmful substances such as harmful gases harmless, for example, in the decomposition of contaminated soil as an object to be treated in a decomposition furnace, the water content of the contaminated soil increases rapidly, or The supply of oxygen gas to the furnace is stopped for some reason, the burning of combustible harmful substances such as combustible waste and waste solvent for calorie adjustment is stopped, and the temperature in the cracking furnace decreases, Even if undecomposed harmful substances such as dioxin in contaminated soil are generated in the decomposition furnace, they are surely decomposed and made harmless.

Further, even when the temperature of the exhaust gas from the electric furnace is lowered and undecomposed harmful substances such as dioxin contained or entrained in the scrap are generated in the electric furnace, it is surely decomposed in the high-temperature decomposition chamber to be harmless. Can be changed. Therefore, the high-temperature decomposition chamber can serve as a guard reactor for the electric furnace and the decomposition furnace.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic flow sheet showing an embodiment of an apparatus for treating harmful substances applied to the present invention, FIG.
3 is a graph showing an example of an operation (operation) cycle of an electric furnace and an operation state of a decomposition furnace and a high-temperature decomposition chamber shown in association with each other, and (a) is a graph showing a relationship between an electric furnace operation cycle and an outlet temperature. (B) is a graph showing the relationship between the operation cycle of the cracking furnace and the temperature of the molten slag in the cracking furnace, and (c) is the temperature of the indoor gas in the high-temperature cracking chamber and the temperature for generating the high-temperature gas supplied to the high-temperature cracking chamber. It is a graph which shows the relationship between the cycle of reheating and the amount of reheating.

As shown in FIG. 1, the harmful substance processing apparatus 1 comprises:
Electric furnace 10, cracking furnace 20, high-temperature cracking chamber 30, quenching chamber 4
0, a cyclone 50 and a bag filter 70 which are dust collectors for collecting dust in the electric furnace 10 and the decomposition furnace 20, an exhaust gas duct for communicating between the devices, and a direct drawing blower 60. A cracking furnace exhaust gas pipe 21 is connected between the cracking furnace 20 and the high-temperature cracking chamber 30.
An electric furnace exhaust gas pipe 11 is connected in the middle of the process, and the electric furnace 10 and the decomposition furnace 20 are configured to be able to introduce respective exhaust gas into the high-temperature decomposition chamber 30. The exhaust gas outlet of the high-temperature decomposition chamber 30 is connected to the quenching chamber 40 by the high-temperature decomposition chamber exhaust gas pipe 12.

The high-temperature decomposition chamber 30 is connected to a decomposition chamber combustion furnace 30A as a high-temperature gas supply source via a high-temperature gas pipe, while the decomposition furnace 20 is connected to the decomposition furnace combustion furnace 30B as a high-temperature gas supply source. Are connected via another hot gas pipe. The high-temperature decomposition chamber 30 is provided with a thermometer 30a such as a thermocouple for detecting the indoor temperature.
A temperature indication controller TIC is provided between A and A.
These auxiliary furnace 30A, thermometer 30a and temperature indicating controller TIC constitute a high-temperature decomposition chamber temperature control device.

The gas temperature in the high-temperature decomposition chamber 30 is maintained at a constant high temperature (for example, 850 ° C.) at which the harmful gas such as dioxin can be decomposed into a harmless gas by the high-temperature decomposition chamber temperature control device. That is, the gas temperature in the high-temperature decomposition chamber 30 is measured by the thermometer 3.
0a, and based on the detected value, the combustion amount of fuel (heavy oil or the like) in the auxiliary combustion furnace 30A is controlled so that the temperature of the high-temperature decomposition chamber 30 is maintained at the constant high temperature. On the other hand, the decomposition furnace 20
Is provided with a thermometer 20a such as a thermocouple for detecting the temperature inside the furnace, and another temperature indicating controller TIC is provided between the thermometer 20a and the auxiliary combustion furnace 30B. These combustion furnaces 30
B, the thermometer 20a and the temperature indicating controller TIC constitute a decomposition furnace temperature control device.

The gas temperature in the cracking furnace 20 is controlled by the cracking furnace temperature control device to a high temperature at which harmful gas such as dioxin can be decomposed into a harmless gas and a constant high temperature (for example, 1500) capable of maintaining the molten state of the molten slag. ° C). That is, the gas temperature in the cracking furnace 20 is detected by the thermometer 20a,
Based on the detected value, the combustion amount of fuel (heavy oil or the like) in the auxiliary combustion furnace 30B is controlled such that the temperature of the decomposition furnace is maintained at the constant high temperature.

A cyclone 50 for dust collection is connected downstream of the quenching chamber 40 via an exhaust gas pipe 41, and the cyclone 50 is connected to a bag for final dust collection by a suction duct 51 provided with a direct blower 60. The exhaust gas outlet of the bag filter 70 is connected to a clean gas discharging stack 80. Reference numeral 60a is a blower for collecting house dust.

The electric furnace 10 is rotatably supported on both sides of the upper part of the furnace body so that the furnace body can be tilted. A slag outlet 10c is provided in the upper part of the furnace wall of the electric furnace 10. The slag outlet 10c also serves as a peephole and an oxygen blowing hole. The high-temperature molten slag is tilted from the electric furnace 10 by a tilting device composed of a hydraulic cylinder, thereby forming a slag outlet 10c.
Is taken out by draining from The electric furnace 10 employs an electric furnace for melting arc-type scrap (iron scraps such as steel scraps).
b is attached.

The cracking furnace 20 is installed on a carriage 22 that can run on rails 23 laid to extend to the electric furnace 10, and is located near the electric furnace 10 when receiving high-temperature molten slag. Be moved.

Next, the operation of the harmful substance treating apparatus 1 configured as described above will be described. The amount of scrap to be melted is charged into the electric furnace 10 in plural times and melted. That is, as shown in FIG. 2A, in the first cycle, the scrap is charged into the electric furnace 10 separately from the initial loading, the additional loading 1 and the additional loading 2.

The temperature of the exhaust gas at the outlet of the electric furnace rises with the progress of the melting of the scrap.
It will be 0 ° C. However, during the melting of the scrap from the initial loading through the additional loading 1 and the additional loading 2, the temperature of the exhaust gas at the outlet of the electric furnace 10 is low and the additional loading 1 and the additional loading 2
In this case, the power supply to the electrode 10b is cut off, the upper lid 10a is opened, and new scrap is charged, so that the furnace temperature and the exhaust gas temperature are rapidly lowered. When a predetermined time has passed through the additional equipment 2 and the temperature in the furnace has reached a substantially predetermined temperature, oxygen is blown (referred to as blowing), and impurity elements in the molten steel are oxidized and removed.

At the time of the first cycle melting of the electric furnace 10,
In the high-temperature decomposition chamber 30, the exhaust gas from the electric furnace is discharged into the exhaust gas pipes 11 and 2.
Introduced via 1. The high-temperature decomposition chamber 30 is always kept at a constant temperature at which the harmful substances such as dioxin discharged from the electric furnace can be rendered harmless by the high-temperature decomposition chamber temperature control device. That is, when the temperature of the exhaust gas of the electric furnace is low at the time of melting based on the initial loading, the additional loading 1, and the additional loading 2, and when the temperature of the exhaust gas decreases, the amount of heat due to the low temperature of the exhaust gas of the electric furnace 10 is compensated. The combustion furnace 30A for the high-temperature decomposition chamber is operated, and FIG.
Auxiliary fuel is refired with the reheating amount of the curve as shown in (c), high-temperature gas is generated from the auxiliary combustion furnace 30A and introduced into the high-temperature decomposition chamber 30, and as shown in FIG. 2 (c). The interior of the high-temperature decomposition chamber 30 is maintained at a predetermined high temperature, for example, a high temperature of 850 ° C. or more, which is the decomposition temperature of dioxin. The exhaust gas that has exited the high-temperature decomposition chamber 30 is guided to a quenching chamber 40, cooled to a predetermined temperature, dust is removed by a cyclone 50 and a bag filter 70, and is discharged from the stack 80 to the atmosphere as a clean gas.

As described above, by maintaining the high-temperature decomposition chamber 30 at a predetermined high temperature even during the melting of the electric furnace 10 in the first cycle, the temperature at the time of melting by the initial charging, the additional loading 1, and the additional loading 2 in the electric furnace. When the temperature is low, even if harmful substances such as dioxin entrained in the scrap are generated as undecomposed substances, the harmful substances can be instantaneously decomposed in the high-temperature decomposition chamber and made harmless. In addition,
The current Ministry of Health and Welfare incineration standards stipulate that a detention time of 2 seconds is maintained at 850 ° C. in order to decompose harmful substances such as dioxins, and the internal volume of the high-temperature decomposition chamber 30 is based on that. Designed.

After the ejaculation, a predetermined time has passed and 1
At the time when the dissolution of the predetermined amount of scrap in the cycle is almost completed, the high-temperature molten slag S of about 1500 ° C. is withdrawn. In the extraction of the molten slag S, the decomposition furnace 20 is disconnected from the exhaust gas pipe 21, travels on the rail 23 via the carriage 22, is moved to the vicinity of the electric furnace 10, and the electric furnace 10 is tilted. The molten slag S flows out of the furnace wall outlet 10 c and is transferred to the cracking furnace 20. Since the molten slag S has a small specific gravity inside the electric furnace, the molten slag S gathers and floats on the upper layer of the molten material (molten steel) M of iron, and easily flows out from the outlet 10c by tilting the electric furnace. When the molten slag S is withdrawn, the temperature of the molten steel is not lowered because the current is continuously supplied to the electrode 10b.

When the withdrawal of the molten slag is completed, the electric furnace is restarted. After a lapse of a predetermined time, the electrode 10b
The power supply to the furnace is stopped, the lid of the molten steel outlet at the bottom of the furnace is opened, the steel is tapped and transferred to the ladle, and the molten steel is formed into a billet through a subsequent reduction step and a continuous casting process.

After the high-temperature molten slag is introduced into the cracking furnace 20, the movable carriage 22 is moved and returned to a predetermined position, and the exhaust gas pipe 21 is connected. And FIG.
As shown in (b), after a lapse of t2 hours from the removal of the slag, the cracking furnace 20 is operated in the first cycle.
In the cycle, after the elapse of t1 time after the completion of tapping of the electric furnace, the operation for burning and decomposing harmful substances is performed while maintaining the predetermined slag temperature of 1500 ° C. until the slag is withdrawn in the second cycle of the next electric furnace melting step. Will be In the electric furnace, the second cycle and subsequent cycles are also subjected to initial loading, additional loading 1, additional loading 2, blowing, slag extraction, and tapping in the same time cycle as the first cycle. One cycle of the electric furnace runs, for example, in about 60 minutes.

Next, the first cycle operation of the cracking furnace 20 will be described. In the present embodiment, a case where the harmful substance to be treated is contaminated soil contaminated with dioxin or the like will be described. Contaminated soil contaminated with dioxin etc.
Prior to being put into the refuse, waste plastic is mixed as a combustible waste for calorie adjustment, for example, by plowing. The high-temperature molten slag is supplied to the cracking furnace 20, and the molten high-temperature slag is used as a high-temperature ignition source containing oxygen, and burned and decomposed including fine metal and quicklime (CaO) acting as a promoter. Used as a reaction accelerator.

That is, the high-temperature molten slag is, for example, Fe
Since it contains oxygen as an oxide such as O, SiO ₂ , MnO, and Al ₂ O ₃ and has a high temperature, it is most suitable as a high-temperature ignition source for combustibles. In addition, metal ions (Fe ²⁺ , M
n ²⁺ ) and quicklime (CaO) serve as co-catalysts to promote reactions such as oxidation (combustion) of combustibles and decomposition of harmful substances such as dioxins.

Contaminated soil mixed with waste plastic is supplied to the cracking furnace 20 having such high-temperature molten slag, and at the same time, oxygen (O ₂ ) for waste plastic combustion (hereinafter referred to as supply oxygen) is supplied. You. Then, the waste plastic, which is a combustible, is ignited instantly with the help of the high-temperature ignition source of the high-temperature molten slag, and is burned by the supplied oxygen. This prevents a rapid drop in the temperature of the molten slag due to the introduction of the contaminated soil, prevents the molten slag from being solidified, and maintains the temperature required for dissolving the contaminated soil at, for example, 1500 ° C. Dioxins and the like are rendered harmless by thermal decomposition. The burning action of the combustible waste plastic and the thermal decomposition action of dioxin and the like are effectively promoted by the co-catalyst action of metal ions and quick lime, which are characteristics of the high-temperature molten slag.

During the decomposition of contaminated soil, the temperature of the gas in the decomposing furnace 20 is controlled by the temperature control device so that harmful substances such as dioxin can be decomposed as harmless gas, The slag is maintained at a constant temperature of 1500 ° C. at which the slag can maintain a molten state. That is, when the water content of the contaminated soil rapidly increases during the decomposition action of the contaminated soil, or when the supply of the supplied oxygen is cut off due to a trouble in the piping system or the like, the temperature in the decomposition furnace 20 is reduced due to some cause. When the temperature falls below the set temperature (1500 ° C.), the temperature indicating controller TIC of the temperature control device operates, the auxiliary combustion furnace 30B is operated so as to return to the set temperature of the cracking furnace of 1500 ° C. It is blown in. Therefore, the generation of undecomposed harmful substances such as dioxin in the contaminated soil due to the decrease in the temperature of the decomposition furnace 20 is reliably prevented, the solidification of the molten slag is prevented, and the decomposing action of the contaminated soil is stably and surely performed. Done.

The high-temperature exhaust gas at a temperature of 1500 ° C. of the cracking furnace 20 generated by the burning of combustible materials such as the waste plastics is introduced into a high-temperature cracking chamber 30 through an exhaust gas pipe 21.
This is effectively used to maintain the temperature of the high-temperature decomposition chamber 30 at 850 ° C. or higher, which is a temperature at which harmful substances such as dioxin can be decomposed. At the same time, the exhaust gas from the electric furnace 10 is also introduced into the high-temperature decomposition chamber 30 through the exhaust gas pipes 11 and 21,
Harmful gases such as dioxin discharged from the electric furnace 10 are also decomposed.

In this embodiment, the electric furnace exhaust gas pipe 11 is used.
Is connected in the middle of the decomposition furnace exhaust gas pipe 21 so that when the temperature of the exhaust gas from the electric furnace 10 is low or low, harmful gases such as dioxin
Even when the gas is discharged from 0, the harmful gas is decomposed by the decomposition furnace high temperature exhaust gas maintained at a predetermined high temperature of 1500 ° C. in the decomposition furnace exhaust gas pipe 21 after the connection point as described above. To be harmless gas.

The temperature of the high-temperature decomposition chamber 30 is maintained at a minimum temperature of 850.degree. That is,
By the operation of the auxiliary furnace 30A of the temperature control device, FIG.
As shown in the curve of the amount of reheating, the amount of fuel (the amount of reheating) of the auxiliary combustion furnace 30A is burned to generate a high-temperature gas. At about the same time as the first cycle during the second cycle of molten steel work in the electric furnace 10, when the melting temperature of the electric furnace or the exhaust gas temperature during the supercharging 1 and the supercharging 2 is low, or when the temperature decreases. It is performed in a combined cycle.

In this embodiment, since the amount of exhaust gas from the electric furnace 10 is much larger than the amount of exhaust gas from the decomposition furnace 20, even if the exhaust gas from the decomposition furnace 20 is maintained at 1500 ° C. as described above, When the exhaust gas temperature of the electric furnace 10 is low or decreases, the temperature of the high-temperature decomposition chamber 30 decreases. Therefore, the room temperature of the high-temperature decomposition chamber 30 is
a, and in response thereto, the auxiliary combustion furnace 30A of the temperature control device of the high-temperature decomposition chamber 30 is operated in the reheating cycle and the reheating cycle as described above to generate a high-temperature gas and supply the heat to the high-temperature decomposition chamber 30. And the temperature of the high-temperature decomposition chamber 30 is set to 85
Maintain a constant temperature of 0 ° C. or higher.

As described above, when the temperature of the exhaust gas from the electric furnace 10 is low or low, even if undecomposed substances (undecomposed gas) of harmful substances such as dioxin accompanying or contained in the scrap are generated, the temperature is high. The temperature of the decomposition chamber 30 is controlled so that the decomposition temperature is kept at a minimum of 850 ° C., so that the undecomposed material is surely decomposed and made into a harmless gas. As described above, even during the decomposition treatment of the contaminated soil by the decomposition furnace 20, harmful substances such as dioxin generated from the electric furnace 10 are surely rendered harmless. Therefore, the high-temperature decomposition chamber 30 functions as a guard reactor for the decomposition furnace 20 and the electric furnace 10.

The exhaust gas discharged from the high-temperature decomposition chamber 30 is
After being introduced into the quenching chamber 40 through the exhaust gas pipe 12 and cooled to a predetermined temperature, the cyclone 50 and the bag filter 70 as dust collecting dust collectors are exhausted through the exhaust gas pipes 41 and 51.
And the dust generated from the electric furnace and the cracking furnace are removed. The exhaust gas from which the dust has been removed is released from the stack (chimney) 80 to the atmosphere as a clean gas.

When the decomposition operation of the contaminated soil by the decomposition furnace 20 is completed, the decomposition furnace 20 is tilted by the tilting device, or
The lid of the bottom slag outlet is opened and the molten slag is removed from the cracking furnace.

Thus, the present invention can be easily implemented by using an existing (existing) electric furnace for scrap melting and the like and its accompanying equipment. That is, for example, the existing electric furnace equipment for melting scrap will be described with reference to FIG. 1. The electric furnace 10, the quenching chamber 40, the cyclone 50 for collecting dust generated in the electric furnace, the bag filter 70, the direct drawing blower 6
0, a building dust blower 60a, and an exhaust gas pipe connecting those devices. When the present invention is implemented, the existing electric furnace equipment is provided with the decomposition furnace 20 and / or the high-temperature decomposition chamber (guard). Reactor) 30, combustion furnace 30A, 30
It is only necessary to additionally install B and a conduit such as the exhaust gas pipe 21 that connects them.

In the above embodiment, the substance to be decomposed is contaminated soil contaminated with harmful substances such as dioxin, and before being put into the decomposition furnace 20, the contaminated soil is converted into combustible waste for calorie adjustment. Although the case of mixing waste plastic is shown, the object to be decomposed is a flammable harmful substance that burns itself, for example, if it is a waste solvent, the combustible waste for calorie adjustment is In some cases, it is not necessary to mix the material into the processing object in advance.

When the object to be decomposed is contaminated soil contaminated with waste solvent or the like, the waste solvent itself contained in the contaminated soil easily burns, so that the content of waste solvent is large. If the melting temperature of the slag can be maintained, there is no need to mix combustible waste for calorie adjustment before charging the slag into the cracking furnace. However, when the content of the slag is such that the melting temperature of the slag cannot be maintained by the combustion, the combustible waste for calorie adjustment needs to be mixed with the contaminated soil in advance.

In the above embodiment, the cracking furnace 20 is provided so as to be able to run on the rail 23 via the carriage 22 and the electric furnace 10 is provided.
And the high-temperature molten slag was moved from the electric furnace 10 to the installation position. However, the decomposition furnace was set at a fixed position, and the electric furnace was tilted with a separate ladle positioned near the electric furnace. The slag may be transferred to the ladle via the outlet of the electric furnace main body, and the ladle may be moved to the position of the cracking furnace and transferred to the cracking furnace.

In the above embodiment, the case where the electric furnace 10 is an electric furnace of a type in which one melting operation cycle of the scrap is divided into the initial loading, the additional loading 1, and the additional loading 2 separately is described. The invention is of course applicable even if the electric furnace is of the type that melts with only one charge of scrap.

In the above embodiment, an example in which contaminated soil containing dioxin as a harmful substance is thermally decomposed has been described. However, in the present invention, as a treated harmful substance, contaminated ash contaminated with dioxin or waste ash is used. Of course, harmful substances such as solvents, waste pesticides, contaminated soil contaminated with these waste solvents and waste pesticides, and hazardous wastes such as medical wastes can also be applied.

[0056]

EXAMPLE An electric furnace 10 for melting scrap was used as an electric furnace 10, and scrap was melted in a melting cycle as shown in FIG. 2 to obtain 80 tons of molten steel and a temperature generated by the melting. Transferred the high-temperature molten slag having a weight of 5 tons at 1500 ° C. to the cracking furnace 20, and charged 2 tons (40% of the weight of the molten slag) of the dioxin-contaminated soil into the cracking furnace 20 having the high-temperature molten slag. Pyrolyzed. Before pouring into contaminated soil, a predetermined amount (approximately 120 kg) of waste plastic is plowed as a combustible waste for calorie adjustment before mixing into the decomposition furnace 20, and the molten slag is necessary for dissolving the contaminated soil. The amount of calorie replenishment necessary to maintain a proper temperature was ensured to prevent the temperature of the mixture from lowering.

As a result, it was confirmed that the contaminated soil was almost completely decomposed and made harmless. During the decomposition operation by the decomposition furnace 20, the electric furnace 10 is set to a predetermined melting temperature of 1100.
Electric furnace exhaust gas (about 60,000 Nm ³
/ Hr) into the high-temperature decomposition chamber 30 and the decomposition furnace 20
(1500 ° C., about 800 Nm ³ / hr) is introduced into the high-temperature decomposition chamber 30, and when the temperature of the exhaust gas from the electric furnace 10 is low or low, the temperature control device for the high-temperature decomposition chamber activates the auxiliary combustion furnace 30A. Set the temperature of the high-temperature decomposition chamber 30 to 8
It was kept at a high temperature of 50 ° C. or higher. In the cracking furnace 20, the temperature control device for the cracking furnace was operated so as to maintain the furnace temperature at 1500 ° C. As a result, when the exhaust gas at the outlet of the bag filter 70 was measured, it was confirmed that the dioxin content was within the allowable range of 0.1 ng-TEQ / Nm ³ .

[0058]

As is apparent from the above description, the present invention has the following advantages because it has the structure described in the claims.

According to the first and fifth aspects of the present invention, the object to be treated and the amount to be treated are not affected by the operation of the electric furnace as in the conventional case where harmful substances are put into an electric furnace for treatment. High-temperature molten slag that can be used to decompose harmful substances and has been discarded in the operation of electric furnaces
It is used as a high-temperature ignition source containing oxygen and as a combustion / decomposition reaction accelerator containing fine metal and quick lime that act as a promoter to promote the decomposition of harmful substances, and stabilize harmful substances. It can be made harmless by continuous thermal decomposition. For the treatment of harmful substances, an electric furnace for scrap melting and an electric furnace including the auxiliary equipment are used, and the electric furnace is operated for normal steelmaking operation for melting scrap. This makes it possible to remarkably reduce the amount of capital investment and operation costs as a harmful substance treatment device.

According to the second aspect of the present invention, a flammable waste such as waste plastic is previously mixed with the harmful substance as a calorie adjusting material before the harmful substance is introduced into the decomposition furnace. Prevents a sharp drop in the temperature of the mixture of existing high-temperature molten slag and newly added harmful substances, keeps the slag at the high temperature required for dissolving harmful substances, and stably decomposes harmful substances. Can be made.

According to the third and sixth aspects, the exhaust gas discharged from the electric furnace and the decomposition furnace is introduced into the high-temperature decomposition chamber, and harmful gas such as harmful gas leaked from the electric furnace or the decomposition furnace in the high-temperature decomposition chamber. Detoxification of harmful substances, the fluctuation of the internal temperature of the electric furnace lowers the temperature of the exhaust gas from the electric furnace, causing undecomposed harmful substances such as dioxins contained or entrained in scrap in the electric furnace, Decomposition action is hindered by the temperature drop due to some factor in the furnace,
Even if an undecomposed product of a harmful substance such as dioxin is generated from the decomposition furnace, the undecomposed product can be detoxified in a high-temperature decomposition chamber.

According to the fourth and seventh aspects of the present invention, a high-temperature gas is supplied to the cracking furnace and the high-temperature cracking chamber from a high-temperature gas supply source such as a combustion furnace, and the temperature inside the cracking furnace and the high-temperature cracking chamber are harmful. Since the temperature is controlled to a predetermined high temperature that can render harmful substances such as gas harmless, for example, in the decomposition of contaminated soil as an object to be treated in the decomposition furnace, the water content of the contaminated soil rapidly increases, or the decomposition furnace The supply of oxygen gas to the furnace is stopped for some reason, the burning of combustible harmful substances such as combustible waste and waste solvents for calorie adjustment is stopped, and the temperature inside the cracking furnace decreases, resulting in pollution. Even if undecomposed harmful substances such as dioxin in the soil are generated in the decomposition furnace, they can be stably and reliably decomposed and made harmless.

Furthermore, even when the temperature of the exhaust gas from the electric furnace is lowered and undecomposed harmful substances such as dioxins contained or entrained in the scrap are generated in the electric furnace, it is surely decomposed in the high-temperature decomposition chamber to be harmless. Can be changed. Therefore, the high-temperature decomposition chamber can serve as a guard reactor for the electric furnace and the decomposition furnace.

[Brief description of the drawings]

FIG. 1 is a schematic flow sheet showing one embodiment of an apparatus for treating harmful substances applied to the present invention.

FIG. 2 is a graph showing an example of an operation (operation) cycle of an electric furnace and an operation state of a decomposition furnace and a high-temperature decomposition chamber shown in association therewith, and (a) shows a relationship between an electric furnace operation cycle and an outlet temperature. (B) is a graph showing the relationship between the operation cycle of the cracking furnace and the temperature of the molten slag in the cracking furnace, and (c) is the temperature of the indoor gas in the high-temperature cracking chamber and the high-temperature gas supplied to the high-temperature cracking chamber. It is a graph which shows the relationship between the cycle of additional reheating and the amount of additional heating.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 harmful substance treatment device 10 arc type electric furnace 10 a top lid 10 b electrode rod 10 c slag outlet S high temperature molten slag M molten steel 11 electric furnace exhaust gas pipe 20 decomposition furnace 20 a, 30 a thermometer 21 decomposition furnace exhaust gas pipe 22 decomposition furnace truck 23 rail 30 High-temperature decomposition chamber (guard reactor) 30A Burning furnace (for reheating of high-temperature decomposition chamber) 30B Fire-reducing furnace (for reheating of decomposition furnace) 40 Quenching chamber 50 Cyclone 60 Direct blower 60a Building dust collector blower 70 Bag filter 80 Stack (chimney)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoshi Orizaki F-term in 1978 Ube Steel Co., Ltd. at 1978, Kogushi-ji, Obe-shi, Ube-shi, Yamaguchi F-term (reference) 4D004 AA36 AA41 AA48 AB07 CA24 CB04 CB31 CB36 CC01 CC11 CC12 CC17 DA02 DA06

Claims (7)

[Claims] 1. A step of taking out high-temperature molten slag as waste from an operating electric furnace and putting it into a decomposition furnace, and introducing a harmful substance into the decomposition furnace holding the high-temperature molten slag to thermally decompose it. And a method for treating harmful substances. 2. The method according to claim 1, further comprising a step of mixing the harmful substance with a combustible waste necessary for maintaining the harmful substance at a temperature required for dissolving the harmful substance prior to the step of charging the harmful substance into the decomposition furnace. The method for treating harmful substances according to claim 1, wherein: 3. The method further comprises a step of introducing exhaust gas from the electric furnace and the decomposition furnace into a high-temperature decomposition chamber and decomposing harmful substances such as harmful gases leaked from the electric furnace or the decomposition furnace in the high-temperature decomposition chamber to render them harmless. The method for treating harmful substances according to claim 1 or 2, wherein: 4. A step of supplying a high-temperature gas to the cracking furnace and the high-temperature cracking chamber, respectively, and controlling the temperature of the cracking furnace and the high-temperature cracking chamber so as to maintain a predetermined high temperature capable of detoxifying harmful substances such as harmful gases. The method for treating harmful substances according to claim 3, further comprising: 5. An electric furnace, and a decomposition furnace into which high-temperature molten slag generated in the electric furnace is charged and a harmful substance is charged into the high-temperature molten slag and thermally decomposed. A harmful substance processing device characterized by the following. 6. A high-temperature decomposition chamber connected to the electric furnace and the decomposition furnace by an electric furnace exhaust gas pipe and a decomposition furnace exhaust gas pipe, respectively, for detoxifying harmful substances such as harmful gas leaked from the electric furnace or the decomposition furnace. The harmful substance processing device according to claim 5, further comprising: 7. A temperature for providing a high-temperature gas supply source to each of the cracking furnace and the high-temperature cracking chamber, and maintaining the cracking furnace and the high-temperature cracking chamber at a predetermined high temperature capable of detoxifying harmful substances such as harmful gases. The apparatus for treating harmful substances according to claim 6, further comprising a control device.