JP2009172523A - Ash treating method of roasting furnace, and roasting equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ash treating method of a roasting furnace which prevents a remnant of fly ash containing highly-concentrated heavy metals in roasted ash, and can improve a removal efficiency of the heavy metals, and to provide roasting equipment. <P>SOLUTION: The roasting equipment includes the roasting furnace 2 kept at a reducing atmosphere, and volatilizing and separating heavy metals by heating an object to be treated containing heavy metals at temperatures of the melting point or less, and an ash discharger 3 discharging by dropping the roasted ash produced in the roasting furnace 2 from a pipe arrangement 31, and is characterized in that a nozzle 32 introducing a gas for separation into the pipe arrangement is provided on the pipe arrangement 31 of the ash discharger 3, at the same time, the gas for separation introduced from the nozzle 32 forms ascending air in the pipe arrangement, and a flow rate separating the fly ash having a fine particle diameter and containing heavy metals from the roasted ash by the ascending air to return it to the roasting furnace 2 is set. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an ash treatment method and a roasting facility for a roasting furnace in which an object to be treated such as ash and soil containing heavy metals is heat-treated in a reducing atmosphere, and the heavy metals are volatilized and separated to be harmless. .

  Various types of heavy metals are contained in incineration ash and fly ash generated by incineration of general waste and industrial waste. Incinerators that do not have heavy metal treatment facilities may leak heavy metal-containing substances into the atmosphere, soil, and groundwater. In addition, there are environmental standards in soils such as factory sites and landfills. Heavy metals may be present in concentrations higher than those specified in. Many heavy metals are highly toxic and not only adversely affect the environment but also accumulate in the body and cause harm. In recent years, regulations on heavy metals tend to be stricter, such as the establishment of environmental standards for heavy metals contained in incineration ash, fly ash, soil, and the like. In particular, there is a method of recycling the incinerated ash from molten slag as a resource product derived from incinerated ash, but for heavy metals in the molten slag, in addition to the conventional elution control, a new content control has been set. It was done.

As one method for detoxifying substances containing heavy metals, a method is proposed in which the object to be treated is heated in a reducing atmosphere in a roasting furnace maintained below the melting point, and the heavy metals are volatilized and removed. Has been put to practical use.
FIG. 7 shows an apparatus configuration for detoxifying heavy metals using a roasting furnace. As shown in the figure, in this apparatus, an object to be treated containing heavy metals such as ash and soil is put into a roasting kiln 52 from a hopper 51, and at a high temperature of 950 to 1050 ° C. in a reducing atmosphere. Heat treatment to volatilize and separate heavy metals. The roasted ash from which the heavy metals have been separated is fed to the ash cooling device 53, cooled by the ash cooling device 53, and then reused or landfilled. On the other hand, the exhaust gas generated in the roasting kiln 52 is discharged from the roasting kiln 52 in a state containing fly ash enriched with heavy metals, and is processed by an exhaust gas treatment facility 54 provided at a subsequent stage.

Among heavy metals, Pb is particularly a problem. In addition to the above configuration, as a method for improving the removal efficiency of heavy metals containing Pb, chlorine is supplied to a roasting furnace by supplying chlorine to heat treatment. There has been proposed a method in which the material is vaporized and removed.
For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-181323), combustion exhaust gas containing hydrogen chloride discharged from a waste incinerator is introduced into an ash treatment furnace for treating incineration ash and is included in the incineration ash. The method of volatilizing and removing the heavy metals to be removed as chlorides is disclosed.
Further, in Patent Document 2 (Japanese Patent Laid-Open No. 2005-288433), after introducing a chlorine-containing substance or a chlorine-based exhaust gas into a rotary kiln, chlorinating heavy metals in an object to be treated to lower the boiling point, A method for volatilizing and removing heavy metals is disclosed.

JP 2004-181323 A JP 2005-288433 A

As described above, as a method of detoxifying heavy metals, there is a method of removing heavy metals by volatilization by heating the object to be processed in a reducing atmosphere in a roasting furnace. Some of the heavy metals were concentrated to fly ash, sent to the exhaust gas treatment facility together with the exhaust gas, and processed in the exhaust gas treatment facility.
However, the fly ash that should be discharged to the exhaust gas treatment equipment cannot be scattered and mixed into the roasted ash, and there is a possibility that heavy metals may remain in the roasted ash by being discharged with the roasted ash. there were. That is, if the fly ash and the roasted ash are not sufficiently separated, there is a problem that the heavy metal removal efficiency of the roasted ash is lowered.

As described in Patent Document 1 and Patent Document 2 and the like, fly ash is also sufficiently roasted in a method in which heavy metals in a workpiece are chlorinated to lower the boiling point and volatilize heavy metals. If it is not separated from the burned ash, fly ash containing high-concentration heavy metals remains in the roasted ash, and the removal efficiency of heavy metals decreases.
Therefore, in view of the above-mentioned problems of the prior art, the present invention prevents fly ash containing high-concentration heavy metals from remaining in the roasted ash and improves the heavy metal removal efficiency. It aims at providing the ash processing method and roasting equipment of a kiln.

Therefore, in order to solve this problem, the present invention provides:
An object to be treated containing heavy metals is separated by volatilizing and separating the heavy metals by heating at a temperature below the melting point in a roasting furnace maintained in a reducing atmosphere. In the ash treatment method of the roasting furnace that was dropped from the piping and discharged,
A separation gas is introduced into a pipe of the ash discharging device to form an ascending air current, and the ascending air current is used to separate fine ash containing heavy metals from the roasted ash to the roasting furnace. It is characterized by returning.

  According to the present invention, the fly ash having a small particle diameter contained in the roasted ash is separated by the rising air flow formed by the separation gas, whereby the fly ash containing a high concentration of heavy metals is separated. It is possible to prevent the ash from remaining and improve the heavy metal removal performance of the roasted ash.

Further, the ascending air current has a flow rate capable of separating fly ash having a particle size of 10 μm or less from the roasted ash by accompanying the ascending air current.
Fly ash containing heavy metals at a high concentration is fly ash having a fine particle size of 10 μm or less, and when the particle size exceeds 10 μm, the concentration of heavy metals in the ash becomes extremely low. Therefore, the fly ash of 10 μm or less is separated from the roasted ash, and the separated fly ash is returned to the roasting furnace and sent to the exhaust gas to be discharged, whereby almost heavy metals are left in the roasted ash. It is possible to perform the detoxification process without any problem.

Furthermore, the ascending airflow has a flow rate of 0.2 to 0.4 m / s.
In order to blow away fine ash containing high-concentration heavy metals and separate them from roasted ash, a flow rate of 0.2 or higher is sufficient because of the terminal velocity of fly ash, while heavy metals are mostly used. Since it is not necessary to separate the ash which does not contain, 0.4 m / s is made into the upper limit of the flow velocity. Thus, by appropriately setting the flow rate of the separation gas to be introduced, it is possible to minimize the influence on the exhaust gas treatment facility.

A roasting furnace that volatilizes and separates the heavy metals by heating an object to be treated containing the heavy metals at a temperature below the melting point, and a roasted ash generated in the roasting furnace. In roasting equipment equipped with an ash discharge device that drops and discharges
While providing a nozzle for introducing a separation gas into the pipe of the ash discharge device,
The separation gas introduced from the nozzle forms an ascending airflow in the pipe, and the ascending airflow separates fine ash containing heavy metals from the roasted ash to the roasting furnace. The flow rate is set to be returned.

According to the present invention, the fly ash having a small particle diameter contained in the roasted ash is separated by the rising air flow formed by the separation gas, whereby the fly ash containing a high concentration of heavy metals is separated. It is possible to prevent the ash from remaining and improve the heavy metal removal performance of the roasted ash.
The ascending air flow formed by the separation gas introduced from the nozzle has a flow velocity capable of separating fly ash having a particle size of 10 μm or less from the roasted ash by accompanying the ascending air current. To do.
Further, the flow rate of the rising air flow formed by the separation gas introduced from the nozzle is 0.2 to 0.4 m / s.

The nozzle may be arranged so that the ascending air current is a swirling flow.
In this way, by forming a swirling flow in the pipe, the separation gas introduced into the pipe can be easily diffused, the flow rate of the rising air flow becomes uniform, and the roasted ash falling in the pipe It is possible to perform fly ash separation evenly. Furthermore, it is preferable to set the protruding speed of the separation gas from the nozzle to 20 m / s or more, which makes it easy to form an upward swirling flow.

In addition, a diameter of a part of the pipe located above the nozzle is reduced to provide a throttle portion.
According to this, it is possible to ensure the speed of the updraft required with a small flow rate of the separation gas, and the amount of fly ash delivered to the exhaust gas treatment facility due to the excessive supply of the separation gas. An increase and an increase in the exhaust gas treatment amount can be prevented.
Furthermore, in these inventions, it is preferable that the roasting furnace is a rotary kiln.

As described above, according to the present invention, high-concentration heavy metals are contained in the roasted ash by separating the fly ash having a small particle diameter contained in the roasted ash by the rising air flow formed by the separation gas. It is possible to prevent the fly ash containing slag from remaining and improve the heavy metal removal performance of the roasted ash.
Moreover, by making the introduction amount of the separation gas to be introduced appropriate, it is possible to reliably separate the fine particle fly ash from the roasted ash and to minimize the influence on the exhaust gas treatment facility.
In addition, by making the updraft a swirl flow, the separation gas introduced into the pipe is easily diffused, the flow rate of the updraft is made uniform, and evenly fly over the roasted ash falling in the pipe. Ash separation can be performed.
Furthermore, it is possible to ensure the required ascending air velocity with a small flow rate of the separation gas by providing a throttle part in which a part of the pipe is reduced in diameter.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.
1 is a schematic configuration diagram of a roasting facility according to an embodiment of the present invention, FIG. 2 is a side view of the ash discharging apparatus shown in FIG. 1, FIG. 3 is a cross-sectional view taken along the line AA in FIG. FIG. 5 is a graph showing the relationship between the ash particle size and the Pb concentration, and FIG. 6 is a graph showing the relationship between the ash particle size and the terminal flow velocity.
This embodiment is a technique for separating and removing heavy metals such as Pb, Zn, As, Cd, Cr, Se, Hg, Sb, and Cu, and is particularly suitable for removing Pb. Moreover, as a to-be-processed object, the substance containing heavy metals, such as contaminated soil, incineration ash, fly ash, is mentioned, for example.

With reference to FIG. 1, it demonstrates per apparatus structure concerning this embodiment.
The roasting facility according to the present embodiment has a hopper 1 that receives an object to be processed containing heavy metals and supplies it to a roasting kiln (roasting furnace) 2, and an object input port 22 on one end side. The to-be-processed object inlet 22 is connected with the hopper 1, the to-be-processed object is heated at the temperature below melting | fusing point in reducing environment, and the roasting furnace 2 which volatilizes and separates the heavy metals contained in this to-be-processed object The hopper 1 of the roasting furnace 2 is provided with an ash discharging device 3 provided on the other end side, an ash cooling device 4 connected to the ash discharging device 3 for cooling the roasted ash, and the roasting furnace And an exhaust gas treatment facility 5 connected to the two exhaust gas outlets 23.

  As the roasting kiln 2, a rotary rotary kiln is preferably used. The roasting kiln 2 is provided on a cylindrical horizontal furnace body 21 and one end side of the furnace body 21, and a workpiece is put into the furnace body from the hopper 1. A workpiece inlet 22, an ash discharge device 3 provided on the other end side of the furnace body 21 with respect to the hopper 1, a burner 24 provided on the ash discharge device 3 side of the furnace body 21, and a workpiece It has a configuration including an exhaust gas outlet 23 that is provided on the input port 22 side and exhausts exhaust gas generated in the furnace body 21. The furnace body 21 is provided with transfer means (not shown) for transferring the workpiece in the axial direction from the workpiece inlet 22 toward the ash discharging device 3, and the furnace body 21 introduced into the roasting kiln 2. The processed product is roasted by the flame of the burner 24 while being transferred toward the ash discharging device 3. At this time, the roasting kiln 2 has a reducing atmosphere in an oxygen-deficient state or an oxygen-free state so that the object to be treated is not oxidized and burned. Moreover, while the temperature in the roasting kiln 2 is about 500-1200 degreeC, Preferably it is about 950-1050 degreeC, and is maintained at a negative pressure. Moreover, although FIG. 1 showed about the structure which does not supply a chlorine containing substance (a chlorine containing gas is included), you may provide the means to supply a chlorine containing substance.

  On the other hand, the exhaust gas generated by the thermal reaction of the object to be processed by the heat from the burner 24 is conveyed from the ash discharge device 3 toward the object to be processed inlet 22 side, contrary to the transfer direction of the object to be processed. A counter-current flow that opposes the transfer direction of the workpiece is formed and discharged from the exhaust gas outlet 23. In the exhaust gas discharged from the roasting kiln 2, fly ash containing high-concentration heavy metals is present, so that the exhaust gas is processed by the exhaust gas treatment facility 5 on the rear stage side. The exhaust gas treatment facility 5 is set to an optimum configuration for making the exhaust gas harmless by appropriately selecting a treatment device based on the properties and components of the exhaust gas. As an example, an exhaust gas treatment facility includes a recombustion chamber that decomposes dioxins and the like contained in exhaust gas, and a heat exchanger (or a temperature reducing tower) that cools high-temperature exhaust gas discharged from the recombustion chamber by heat exchange. And a bag filter that collects fly ash in the cooled exhaust gas.

  In such a roasting facility, an object to be processed containing heavy metals is introduced into the furnace body 21 of the roasting kiln 2 from the hopper 1 through the object to be treated inlet 22 and from the object to be treated inlet 22. While being transported toward the ash discharge device 3, the metal is heated to a temperature equal to or lower than the melting point of the object to be processed in a reducing atmosphere, whereby heavy metals contained in the object to be processed are volatilized and separated. The volatilized heavy metals are accompanied by the exhaust gas, discharged from the exhaust gas outlet 23, and processed by the exhaust gas treatment facility 5. The heavy metals concentrated in the fly ash among the volatilized heavy metals are also accompanied by the exhaust gas and sent to the exhaust gas treatment facility 5, but a part of the fly ash containing heavy metals is mixed into the roasted ash. And then discharged from the ash discharging device 3.

Therefore, in this embodiment, in addition to the above configuration, the ash discharging device 3 of the roasting furnace 2 reliably separates the fine fly ash containing heavy metals from the roasted ash and into the roasted ash. The structure which suppresses the residue of heavy metals to the minimum is provided.
Since the fly ash particle size is distributed in the range of about 0.6 to 30 μm, and heavy metals such as Pb tend to be concentrated in the fly ash having a particularly fine particle size in this particle size distribution, In the ash discharging device 3, the fly ash is separated from the roasted ash by using a separation gas so that the fly ash is not mixed and discharged from the roasted ash.

In FIG. 2, the side view of the ash discharging apparatus 3 is shown. As shown in the figure, the ash discharge device 3 includes a pipe 31 that connects the roasting kiln 2 and the ash cooling device 4, and further includes one or a plurality of nozzles 32 installed in the pipe 31. . The pipe 31 extends substantially in the vertical direction, and the cross-sectional shape may be circular or rectangular, and the shape is not particularly limited, but the roast generated in the roasting kiln 2 is not limited. It shall have a cross-sectional area where burnt ash can be discharged smoothly.
A separation gas is introduced into the pipe 31 from the nozzle 32. The nozzle 32 may be installed parallel to the horizontal cross section of the pipe 31 or may be installed with an angle downward or upward. When a plurality of the nozzles 32 are installed, they may be installed at regular intervals in the circumferential direction of the pipe 31 or may be installed at different heights.

  As the separation gas, exhaust gas such as combustion exhaust gas or dry exhaust gas, air, or the like is used. As for the combustion exhaust gas, the exhaust gas discharged from the roasting kiln 2 is treated with an exhaust gas as necessary, and then the combustion exhaust gas is introduced into the pipe 31 from the nozzle 32. The dry exhaust gas is introduced from the nozzle 32 into the pipe 31 when a drying device is provided in the front stage of the roasting kiln 2. Moreover, you may use the waste gas discharged | emitted from another processing apparatus. It is preferable to use such an exhaust gas as the separation gas, which makes it possible to reduce the amount of exhaust gas treated in the roasting facility. Moreover, since exhaust gas, such as combustion exhaust gas and dry exhaust gas, has a low oxygen concentration, a reducing atmosphere can be maintained even if it is introduced into the roasting kiln 2. Of course, air may be used, and since the amount of separation gas introduced is smaller than the amount of gas in the furnace body 21, a reducing atmosphere can be maintained.

Further, the flow rate of the separation gas introduced from the nozzle 32 is set to a flow rate that forms an updraft in the pipe 31.
Preferably, the flow velocity (column speed) V ₁ of the ascending air flow in the pipe 31 is set to 0.2 to 0.4 m / s.
Also preferably, the flow velocity V ₁ of the said updraft, the particle size 10μm or less of fly ash is Banoku in the updraft and separable flow rate from the roasting ashes.

FIG. 5 shows the relationship between the ash particle size and the Pb concentration. The graph is an actual measurement value. According to this, when the ash particle diameter exceeds 2 μm, the Pb concentration in the ash becomes extremely low. Therefore, when Pb is contained in the ash at a high concentration, the fly ash has a fine particle diameter of 10 μm or less, and the ash having a particle diameter larger than 10 μm contains almost no Pb.
In this embodiment, based on this result, fly ash having a size of 10 μm or less is separated from the roasted ash, and the separated fly ash is returned to the roasting kiln 2 to be accompanied by the exhaust gas and discharged to the exhaust gas treatment facility 5. Thus, it is possible to improve the heavy metal removal efficiency of the roasted ash with almost no heavy metal remaining in the roasted ash.

FIG. 6 shows the relationship between the ash particle size and the ash terminal speed. According to this, in order to blow away fly ash having a particle size of 10 μm or less and separate it from roasted ash, it is understood that a flow rate of 0.2 or more is sufficient. On the other hand, since it is not necessary to separate the ash that hardly contains heavy metals, it is preferable to set the upper limit to 0.4 m / s. This is also preferable from the viewpoint of preventing the separation gas from being introduced into the roasting kiln 2 more than necessary.
In this embodiment, based on this result, the separation gas is introduced so that the rising air velocity in the pipe 31 is 0.2 to 0.4 m / s. Thus, by making the introduction amount of the separation gas introduced from the nozzle 32 appropriate, the influence on the exhaust gas treatment facility 5 can be minimized.

  In the above-described configuration, the roasted ash generated in the roasting kiln 2 falls from the furnace main body 21 to the ash discharging device 3 in a state that includes fly ash having a fine particle size in which heavy metals are concentrated. In the pipe 31 of the ash discharging device 3, an ascending air flow having a predetermined flow rate is formed by the separation gas blown from the nozzle 32. The fly ash having a small particle diameter is separated from the roasted ash dropped on the ash discharging device 3 by the ascending air current, and the separated fly ash is returned into the furnace main body 21 and is accompanied by exhaust gas from the furnace main body 21. Discharged. The roasted ash from which fly ash containing high-concentration heavy metals is separated is supplied to the ash cooling device 4 and cooled, and then subjected to processing such as reuse or landfill.

  According to the present embodiment, high-concentration heavy metals are contained in the roasted ash by separating the fly ash having a small particle diameter contained in the roasted ash by the rising airflow formed by the separation gas. It is possible to prevent the fly ash from remaining and improve the heavy metal removal performance of the roasted ash.

In addition, as shown in FIG. 3, it is preferable to arrange a plurality of nozzles 32 so that an upward swirling flow is formed in the pipe 31. In this case, the nozzle 32 may be disposed so that the separation gas is ejected toward the tangential direction of the virtual circle set in the pipe 31. In this way, by forming a swirling flow in the pipe 31, the blown separation gas is easily diffused, the flow rate of the rising air flow is made uniform, and the roasted ash falling in the pipe 31 is universal. As a result, it is possible to perform fly ash separation.
Further, it is preferable that the projecting velocity V ₂ of the separation gas from the nozzle 32 and 20 m / s or more, thereby likely to increase the swirling flow is formed.

Moreover, as shown in FIG. 4, it is good also as a structure which provided the aperture | diaphragm | squeeze part 33 which diameter-reduced a part of piping 31 located above the nozzle 32. As shown in FIG. The narrowed portion 33 is provided at a site where ash does not adhere. The part where the ash adheres is a part of the pipe 31 that is a high-temperature part and is highly likely to partially melt and adhere to the wall surface.
The diameter of the narrowed portion 33 is preferably set so that the separation gas introduced from the nozzle 32 is 0.2 to 0.4 m / s.
According to this, it is possible to prevent an increase in the amount of fly ash accompanying the exhaust gas treatment facility and an increase in the exhaust gas treatment amount due to excessive supply of the separation gas.

It is a schematic structure figure of roasting equipment concerning an embodiment of the present invention. It is a side view of the ash discharging apparatus shown in FIG. It is AA sectional drawing of FIG. It is a side view which shows the modification of the ash discharging apparatus shown in FIG. It is a graph which shows the relationship between the particle size of ash, and Pb density | concentration. It is a graph which shows the relationship between the particle size of ash, and a terminal flow velocity. It is a schematic block diagram of the processing apparatus provided with the conventional roasting furnace.

Explanation of symbols

1 Hopper 2 Roasting furnace (roasting kiln)
DESCRIPTION OF SYMBOLS 3 Ash discharge apparatus 4 Ash cooling apparatus 5 Exhaust gas treatment equipment 21 Furnace main body 22 To-be-processed object inlet 23 Exhaust gas outlet 24 Burner 31 Piping 32 Nozzle 33 Restriction part

Claims (9)

An object to be treated containing heavy metals is separated by volatilizing and separating the heavy metals by heating at a temperature below the melting point in a roasting furnace maintained in a reducing atmosphere. In the ash treatment method of the roasting furnace that was dropped from the piping and discharged,
A separation gas is introduced into a pipe of the ash discharging device to form an ascending air current, and the ascending air current is used to separate fine ash containing heavy metals from the roasted ash to the roasting furnace. A method for ash treatment of a roasting furnace, characterized in that it is returned.   2. The ash treatment method for a roasting furnace according to claim 1, wherein the ascending air current has a flow rate capable of separating fly ash having a particle size of 10 μm or less from the roasting ash by accompanying the ascending air current. 3.   The ash treatment method for a roasting furnace according to claim 1, wherein a flow rate of the ascending air current is 0.2 to 0.4 m / s. A roasting furnace that volatilizes and separates heavy metals by heating an object to be treated that contains a heavy metal at a temperature below the melting point, and a roasted ash generated in the roasting furnace. In roasting equipment equipped with an ash discharging device that drops and discharges more,
While providing a nozzle for introducing a separation gas into the pipe of the ash discharge device,
The separation gas introduced from the nozzle forms an ascending airflow in the pipe, and the ascending airflow separates fine ash containing heavy metals from the roasted ash to the roasting furnace. A roasting facility characterized in that the flow rate is set back.   The ascending air flow formed by the separation gas introduced from the nozzle has a flow rate capable of separating fly ash having a particle size of 10 μm or less from the roasted ash by accompanying the ascending air current. Item 5. The roasting equipment according to item 4.   The roasting equipment according to claim 4, wherein a flow rate of the rising air flow formed by the separation gas introduced from the nozzle is 0.2 to 0.4 m / s.   The roasting equipment according to any one of claims 4 to 6, wherein the nozzle is arranged so that the ascending airflow is a swirling flow.   The roasting equipment according to claim 4, wherein a diameter of a part of the pipe located above the nozzle is reduced to provide a throttle portion.   The roasting equipment according to any one of claims 4 to 8, wherein the roasting furnace is a rotary kiln.

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