JPH0972518A - Stopping preventing method for melting furnace gas duct and melting facility therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the sticking and depositing of melted fly ash in a smaller space near an exhaust gas outlet by avoiding the increase in length of an exhaust gas duct by spraying cooling gas to the exhaust gas of a melting furnace outlet before the fly ash contained in the exhaust gas starts liquefying. SOLUTION: The exhaust gas mixed with melted fly ash is exhausted together with melted slag from the slag hole 2 of a plasma melting furnace 1. Since the gas temperature in the furnace 1 is a high temperature of 1200 deg.C or higher, the slag is completely liquid state, but the structure that can supply city gas E toward the hole 2 is formed to prevent the stopping due to the solidification of the melted slag so that the temperature in the duct near the outlet of the hole 2 can be held at 1000 to 1200 deg.C. In this case, cooling gas is sprayed to the exhaust gas of the outlet of the furnace 1 before the melted fly ash contained in the exhaust gas starts liquefying. That is, the high temperature gas is quickly cooled at once by spraying the cooling gas A supplied by cooling gas supply means 9 via a spray nozzle 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing clogging of a melting furnace exhaust gas duct and melting equipment, and more particularly to a melting furnace exhaust gas duct suitable for equipment for melting and solidifying various industrial wastes such as municipal waste incineration ash at high temperature. The present invention relates to a clogging prevention method and a melting facility.

[0002]

2. Description of the Related Art Most of incineration ash generated by incinerating municipal waste, sewage sludge, and other wastes is landfilled. However, since it is becoming more difficult to secure landfill sites year after year, there is a demand for minimizing the volume of incinerated ash to be landfilled, that is, volume reduction treatment.

Further, when the incinerated ash is landfilled as it is, various harmful substances such as heavy metals contained in the incinerated ash itself may dissolve into rainwater, groundwater, etc. and cause so-called secondary pollution. . For this reason, it is also strongly desired that the incineration ash be treated to be pollution-free before the landfill. Under such circumstances, a method of melting and solidifying at high temperature is being adopted in order to realize volume reduction and detoxification treatment of incinerated ash, and a melting furnace is generally used for carrying out the method.

Exhaust gas near the exit of the melting furnace contains fly ash and low-boiling-point gaseous substances (hereinafter collectively referred to as "melt fly ash"). Therefore, depending on the temperature and flow velocity conditions of the exhaust gas from the furnace outlet, molten fly ash may adhere to and accumulate on the inner wall of the exhaust gas duct, and eventually the exhaust gas duct may be blocked.

Therefore, the development of a technique for preventing the blockage of the exhaust gas duct is urgently required, and there have been proposed examples so far. That is, as shown in FIG. 8, as a structure of the exhaust gas duct, a heat resistant porous body 2 such as a foaming ceramic is arranged inside the exhaust gas duct 1, and a wind chamber 3 is provided between the porous body 2 and the exhaust gas duct 1. At the same time, a gas supply nozzle 4 is attached to the exhaust gas duct 1, a gas 9 such as air is sent from the nozzle 4 into the wind chamber 3, and this gas 9 is jetted from the porous body 2 to the inside of the duct.

[0006] By jetting this gas, not only the low boiling point gaseous substance in the vicinity of the porous body 2 is rapidly cooled and solidified and purged, but also the fly ash in the exhaust gas is purged, and these molten fly ash are exhausted into the exhaust gas. It is designed so that it does not directly adhere to or accumulate on the duct.

[0007]

However, there is a problem in the technology for preventing the exhaust gas duct from being blocked by the above proposal. That is, FIG. 7 shows a state in which the molten fly ash is volatilized and the weight is reduced as the temperature rises.

As is apparent from this figure, the temperature is about 100.
It can be seen that when the temperature falls below 0 ° C, the condensation is rapidly progressing as early as possible, and the temperature range in which the molten fly ash is liquefied is extremely wide. It is considered that the molten fly ash adheres to the inner wall of the exhaust gas duct, which is a flue, when condensed from the state of volatilized gas. Therefore, it can be said that the temperature range in which such an adhesion phenomenon occurs is wide.

On the other hand, the exhaust gas immediately after being discharged from the melting furnace is in a high temperature state of about 1200 ° C. and is cooled while passing through the flue. Therefore, as described above, the exhaust gas flow passage area and the flow passage length in the flue to which the molten fly ash adheres are increased due to the wide temperature range in which the molten fly ash is below the condensation point. Therefore, in the blockage prevention technology of the proposed example,
As long as the efficiency of collecting the molten fly ash is to be increased, the exhaust gas duct will have to be energetic and long.

In the exhaust gas from the melting furnace, 300
Harmful dioxins are often generated in the region around 400 ° C. As a countermeasure, dioxin is removed with a bag filter in the exhaust gas post-treatment process that is generally connected to the flue, but the exhaust gas is treated at a temperature below the temperature at which dioxin is likely to occur before treatment with the bag filter. By providing a cooling step for cooling to 0, the removal efficiency of dioxin can be increased.

Therefore, the object of the invention of claim 1 of the present invention is to avoid increasing the length of the exhaust gas duct,
Adhesion of molten fly ash in a smaller space near the exhaust gas outlet,
In addition to taking measures to prevent accumulation, it is possible to combine the effect of suppressing dioxin generation with this prevention measure, simplifying the structure of the flue part up to the exhaust gas post-treatment process, and connecting the conventional exhaust gas cooling process to a bag filter. An object of the present invention is to provide a method for preventing clogging of a melting furnace exhaust gas duct, which can contribute to a significant reduction in the cost of the melting furnace and, as a result, the overall equipment cost of the incinerator / melting equipment by reducing the scale of the exhaust gas aftertreatment device.

In addition to the object of the invention as set forth in claim 1, the object of the invention as set forth in claim 2 is to provide a part after the cooling part of the exhaust gas to a part where the exhaust gas flow is likely to be stagnant, such as a branch part of the exhaust gas duct. An object of the present invention is to provide a method for preventing clogging of a melting furnace exhaust gas duct, which can prevent adhesion and deposition of molten fly ash and ensure stable and continuous operation of the melting furnace.

An object of the invention of claim 3 is to provide a melting facility capable of effectively realizing the object of the invention of claim 1.

[0014]

In order to achieve the above object, the invention according to claim 1 of the present invention is directed to the exhaust gas at the outlet of the melting furnace, and the molten fly ash contained in the exhaust gas is liquefied. It is characterized by spraying a cooling gas before starting. In the invention according to claim 2, the inner wall of the exhaust gas duct corresponding to a portion of the exhaust gas duct after the cooling portion of the exhaust gas, where the flow direction of the exhaust gas changes, is made of a refractory material having a high thermal conductivity and the exhaust gas flow. It is characterized in that a product processed into a thickness such that the roadside surface temperature is 300 ° C. or lower is attached.

Here, the "exhaust gas at the outlet of the melting furnace" means the high temperature exhaust gas before liquefaction in the space passing through the outlet. Before the molten fly ash begins to liquefy, the cooling gas is blown to the exhaust gas because the molten fly ash is actively condensed, solidified, and further scattered in a smaller space immediately after the exhaust gas outlet, and is discharged from the outlet. This is to prevent the molten fly ash from adhering to and depositing on the inner wall of the exhaust gas duct that follows.

The temperature of the exhaust gas in the space immediately after the slag outlet to the exhaust gas cooling portion is in the high temperature range of 1000 to 1200 ° C., but it is preferable to maintain this temperature. This is to prevent blockage due to slag at the outlet.
As shown in FIG. 7, since the molten fly ash is vaporized in the high temperature range of 1000 to 1200 ° C., the adhesion to the refractory surface does not pose a problem.

As described above, the dioxin generated in the exhaust gas from the melting furnace is removed by the bag filter. However, in order to increase the removal efficiency of the bag filter, the exhaust gas reaches the bag filter. In the previous stage, it is necessary to control the exhaust gas temperature on a large scale with water cooling.

In the present invention, the means for spraying the cooling gas onto the exhaust gas before the molten fly ash is liquefied also has the same role as the conventional water cooling temperature control. That is, in order to exert the effect of suppressing the generation of dioxin in addition to the effect of preventing the adhesion and accumulation of molten fly ash, the exhaust gas cooling unit has about 100
A high temperature gas of 0 ° C is rapidly cooled to about 200 ° C.

If it is only intended to prevent the molten fly ash from adhering to the inner wall of the exhaust gas duct, cooling to about 600 ° C. is sufficient as shown in FIG. 7, but the temperature at which dioxin is easily formed. Area is 300-400 ° C
Because it is in the vicinity, it is effective to cool all at once to about 200 ° C in order to suppress the generation of dioxin.

Further, after the exhaust gas cooling section, it is necessary to take countermeasures in anticipation that the exhaust gas temperature control due to the blowing of the cooling gas may become unstable. That is,
When the exhaust gas temperature control becomes unstable, there may be a temperature atmosphere in which the molten fly ash adheres to the inner wall of the exhaust gas duct. In particular, the molten fly ash is likely to be deposited at a portion where the direction of the duct is changed after the exhaust gas cooling section and the stagnation of the gas flow is likely to occur, for example, a branch portion or a bent portion of the exhaust gas duct.

In view of this point, the inventors of the present invention have conducted various experiments on the content of the refractory construction. As a result, the refractory having a large thermal conductivity is thinly processed so that the surface temperature of the refractory on the exhaust gas passage side becomes as low as possible. By doing so, it could be confirmed that the adhesion of the molten fly ash hardly occurred. Therefore, as the invention according to claim 2, after the exhaust gas cooling portion, the inner wall of the exhaust gas duct is processed to a thickness that is a refractory material having a large thermal conductivity and the surface temperature on the exhaust gas passage side is 300 ° C or less. It was possible to adopt the unique solution of sticking something. As a result, stable continuous operation of the melting furnace can be reliably ensured.

The invention according to claim 3 is a melting facility in which a slag portion for simultaneously smelting molten slag and exhaust gas is provided in a lower portion of a melting furnace for melting a material to be melted, immediately after the slag portion. In addition to connecting exhaust gas ducts downward from the slag portion to, a cooling gas blowing nozzle that penetrates the exhaust gas duct wall surface is provided at a position lower than the height of the slag opening in the slag portion, and further to the cooling gas blowing nozzle. It is characterized in that a cooling gas supply means for supplying the cooling gas is provided.

Here, the phrase "provided at a position lower than the height of the outlet" means that the cooling gas is blown out so that the cooling gas can be blown out while the temperature inside the duct is at a high temperature of about 1000 to 1200 ° C. Means to provide. For example, if the flue gas duct is a cylindrical space having a cross sectional area of about 0.3～0.5M ² is in the vertical distance from the height position of the tapping opening downward (exhaust gas flow direction) 0.5 ~ 1.
It is desirable to provide the cooling gas blowing nozzle within the range of about 0 m.

With the above structure, it is possible to provide a melting facility in which a measure for preventing the adhesion and deposition of molten fly ash is provided in a smaller space near the outlet of the melting gas of the melting furnace. In addition, the preventive measure can exert the effect of suppressing the generation of dioxin. Therefore, the structure of the flue part up to the post-treatment process of the gas is simplified, the scale of the conventional gas post-treatment device is reduced, and an economical melting facility that can ensure stable continuous operation of the melting furnace. Can be

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic explanatory view showing an example in which the blockage prevention method and the melting equipment of the present invention are applied to an exhaust gas duct of a plasma melting furnace. Exhaust gas mixed with molten fly ash is discharged from the outlet 2 of the plasma melting furnace 1 together with the molten slag. The temperature of the gas inside the melting furnace 1 is 120
The slag is completely liquid because it is a high temperature of 0 ° C or more, but the city gas E is directed toward the slag outlet 2 to prevent clogging due to the solidification of the molten slag due to the temperature drop when flowing down the slag outlet 2. As a structure capable of supplying, the temperature inside the duct near the outlet of the outlet 2 can be maintained at a high temperature of about 1000 to 1200 ° C.

In the exhaust gas cooling section, the cooling gas A supplied from the cooling gas supply means 9 through the blowing nozzle 7.
The high temperature gas of approx.
Although it is rapidly cooled to about 00 ° C, the refractory 4 on the inner wall of the duct has a stagnation portion of the exhaust gas flow around the blowout nozzle 7 of the cooling gas A as shown in FIG. 2 (a diagram in which only the exhaust gas duct portion is enlarged). As shown by the diagonal lines, the molten fly ash slightly accumulates and grows in an icicle. However, it is possible to prevent the molten fly ash from being accumulated and grown to a certain extent, and the molten fly ash falls into the slag water granulation tank 6.

The problem here is whether or not it is possible to reliably suppress the deposition and growth of the molten fly ash in the vicinity of the cooling gas A blowing nozzle 7, and to understand the conditions. is there. The conditions when the molten fly ash is deposited and grown to some extent and falls due to its own weight or the blowing of the cooling gas are governed by parameters such as the blowing velocity and blowing angle of the cooling gas A, or the arrangement pitch of the cooling gas blowing nozzles 7. .

The applicable range of these parameters will be clarified with reference to FIGS. 3 and 4. The circles in the figure show the cases where the deposition and growth of the molten fly ash converged to such an extent that they did not affect the stable continuous operation of the melting furnace, and the crosses marked with X indicate that the deposition and growth of the molten fly ash converged. This indicates a case where the continuous operation of the melting furnace is adversely affected due to a large amount of deposits or an almost closed state.

FIG. 3 shows the effects of the cooling gas blowing velocity and the blowing angle on the deposition and growth of molten fly ash by providing three cooling gas blowing nozzles 7 on one side and changing the blowing angle α. It is a figure which shows the result.
As is clear from this figure, the larger the angle α formed by the direction perpendicular to the exhaust gas flow and the blowing direction of the cooling gas, the higher the blowing speed of the cooling gas A must be.

When the blowing angle α = 0 °, it is considered that the blowing velocity is minimum and ideal, but when used in an actual melting furnace facility, the exhaust gas flows backward toward the melting furnace depending on the flow rate of the cooling gas, It is not preferable because it may adversely affect the operation of the melting furnace.

In FIG. 4, the cooling gas blowing angle α is 30 °.
It is a figure which shows the result of having investigated the influence which it has on deposition and growth of a molten fly ash when it is set to this and the arrangement pitch of the blowing nozzle 7 is changed. It can be seen that the smaller the number of outlets, the easier the molten fly ash adheres and grows during that time, and the cooling gas outlet speed must be increased.

Exhaust gas treatment equipment is installed after the exhaust gas cooling unit. In FIG. 1, around the branch portion of the exhaust gas duct,
That is, with respect to the portion around the connection between the flue 8 leading to the exhaust gas treatment facility and the exhaust gas cooling portion, where molten fly ash is likely to adhere because the exhaust gas flow is likely to stagnant (the portion indicated by the dashed line in the figure) Is attached to the inner wall of the duct, which is a refractory material having a high thermal conductivity, and which is processed to have a thickness such that the surface temperature on the exhaust gas flow path side is 300 ° C or less. Making it difficult.

The solidified molten fly ash is collected using an ordinary bag filter or the like. In this way, clogging of the exhaust gas duct due to adhesion and deposition of molten fly ash is prevented, and stable and continuous operation of the melting furnace is possible.

FIG. 5 is a schematic explanatory view showing another embodiment. As the inner wall structure of the exhaust gas cooling section, similar to the inner wall structure around the connecting portion to the flue 8 described above, the thermal conductivity of An example is shown in which a large refractory is thinly applied. In this way, the cooling effect of the refractory surface by water cooling further suppresses the adhesion of molten fly ash around the cooling gas blowing nozzle 7,
It is also possible to further enhance the effect of preventing the accumulation of molten fly ash.

FIG. 6 is a schematic explanatory view showing still another embodiment. The configurations of the exhaust gas ducts shown in FIGS. 1 and 5 are such that the molten slag and the exhaust gas follow the same discharge line. However, with such a configuration, harmful components (hydrogen chloride, etc.) in the exhaust gas and molten fly Ash is slag unloading tank 6
The quality of the solidified slag and the slag unloading tank 6 because it mixes in
There is also a risk of degrading the water quality when using a water granulation tank.

Therefore, as shown in FIG. 6, by separately forming the slag line 9 and the exhaust gas line 10 near the outlet, and applying the exhaust gas duct blockage prevention method of the present invention to the exhaust gas line 10 It is also possible to deal with such a situation. In this case, it is preferable that the joint space between the slag line 9 and the exhaust gas line 10 be made as small as possible in order to maintain the high temperature around the outlet of the slag outlet.

[0037]

As described above, according to the first aspect of the present invention, it is possible to prevent the exhaust gas duct from being lengthened and to prevent the adhesion and deposition of the molten fly ash in a smaller space near the exhaust gas outlet. In addition to this, as a preventive measure that can also have a dioxin generation suppression effect, the structure of the flue part up to the exhaust gas post-treatment process is simplified, and the exhaust gas after connecting from the conventional exhaust gas cooling part to the bag filter By reducing the scale of the processing equipment, it has become possible to significantly reduce the equipment cost of the melting furnace and eventually the incineration / melting equipment as a whole.

Further, in addition to the effect of the invention described in claim 1, the invention described in claim 2 is directed to a part after the exhaust gas cooling part such as a branch part or a bent part of the exhaust gas duct where the exhaust gas flow is likely to be stagnant. It is possible to prevent the adhesion and deposition of the molten fly ash and to ensure stable continuous operation of the melting furnace.

Further, in the invention described in claim 3, in short, the structure of the flue part immediately after the discharge gas of the melting furnace in the melting equipment makes it possible to prevent the adhesion and deposition of molten fly ash and to suppress the generation of dioxins. Since it has been adopted, the structure of the flue part up to the post-treatment process of the gas is simplified, the scale of the conventional gas post-treatment device is reduced, and a stable continuous operation of the melting furnace can be secured. It was possible to make a melting facility.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of the present invention.

FIG. 2 is an enlarged view of only an exhaust gas duct portion.

FIG. 3 is a diagram showing the results of examining the influence of a cooling gas blowing velocity and a blowing angle on the deposition and growth of molten fly ash.

FIG. 4 is a diagram showing a result of examination on influences of a cooling gas blowing flow velocity and a pitch of arranging the blowing ports on deposition and growth of molten fly ash.

FIG. 5 is a schematic explanatory view showing another embodiment of the present invention.

FIG. 6 is a schematic explanatory view showing another embodiment of the present invention.

FIG. 7 is a graph showing how the weight of molten fly ash decreases with temperature.

FIG. 8 is a schematic cross-sectional view of essential parts showing a conventional structure for preventing obstruction of a gas duct for a melting furnace.

[Explanation of symbols]

 1 Plasma melting furnace 2 Slag port 3 City gas supply port 4 Refractory 5 Water-cooled iron skin 6 Slag carry-out tank 7 Cooling gas blowing nozzle 8 Flue A Cooling gas E City gas

Front page continuation (72) Inventor Yoshiaki Shimizu 1-3-18 Wakihamacho, Chuo-ku, Kobe-shi, Hyogo Kobe Steel Works, Ltd. Kobe Head Office

Claims (3)

[Claims] 1. A method for preventing clogging of a melting furnace exhaust gas duct, which comprises blowing a cooling gas onto the exhaust gas at the exit of the melting furnace before the molten fly ash contained in the exhaust gas begins to liquefy. 2. The inner wall of the exhaust gas duct, which corresponds to the portion of the exhaust gas duct after the cooling portion of the exhaust gas where the flow direction of the exhaust gas changes, has a refractory material having a high thermal conductivity and has a surface temperature on the exhaust gas passage side. 2. The method for preventing clogging of a melting furnace exhaust gas duct according to claim 1, wherein a material processed to have a thickness of 300 ° C. or less is attached. 3. In a melting facility in which a slag part for simultaneously smelting molten slag and exhaust gas is provided in a lower part of a melting furnace for melting a material to be melted, the slag part is moved downward from the slag part immediately after the slag part. Along with connecting exhaust gas ducts, a cooling gas blowing nozzle that penetrates the wall surface of the exhaust gas duct is provided at a position lower than the height of the outlet of the outlet, and a cooling gas supply that supplies cooling gas to the cooling gas blowing nozzle. Melting equipment characterized by having means.