JP3834347B2 - Method for preventing clogging of melting furnace exhaust gas duct and melting equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a melting furnace exhaust gas duct blockage prevention method and melting equipment, and more particularly to a melting furnace exhaust gas duct blockage prevention method and melting equipment suitable for equipment for melting and solidifying various industrial wastes such as municipal waste incineration ash at high temperatures. Is.
[0002]
[Prior art]
Incineration ash generated from incineration of municipal waste, sewage sludge, and other waste is mostly landfilled. However, since securing landfill sites has become difficult year by year, there is a demand for reducing the volume of incinerated ash to be reclaimed as much as possible, that is, volume reduction processing.
[0003]
In addition, when the incineration ash is landfilled as it is, harmful substances such as various heavy metals contained in the incineration ash itself may be dissolved in rainwater or groundwater, which may cause so-called secondary pollution. For this reason, it is strongly desired that the incinerated ash be made pollution-free before the landfill. Under such circumstances, a method of melting and solidifying at a high temperature is being adopted in order to realize the volume reduction and detoxification treatment of incinerated ash, and a melting furnace is generally used for implementing the method.
[0004]
By the way, the exhaust gas in the vicinity of the outlet of the melting furnace contains fly ash and low-boiling gaseous substances (hereinafter collectively referred to as “molten fly ash”). For this reason, depending on the temperature and flow rate conditions of the exhaust gas at 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.
[0005]
Therefore, development of a technique for preventing the clogging of the exhaust gas duct has been urgently performed, and there have been proposal examples so far. That is, as shown in FIG. 8, as a configuration of the exhaust gas duct, a heat-resistant porous body 2 such as a fired ceramic is disposed inside the exhaust gas duct 1, and an air 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 the gas 9 is jetted from the porous body 2 to the inside of the duct.
[0006]
This gas injection not only quickly cools, solidifies and purges the low boiling point gaseous substance in the vicinity of the porous body 2, but also purges the scattered ash in the exhaust gas, and directly sends these molten fly ash to the exhaust gas duct. It is designed not to adhere and accumulate.
[0007]
[Problems to be solved by the invention]
However, there is a problem with the above-mentioned proposal for preventing the exhaust gas duct from being blocked. That is, FIG. 7 shows how the molten fly ash evaporates and the weight decreases as the temperature rises.
[0008]
As can be seen from this figure, condensation rapidly proceeds as soon as the temperature falls below about 1000 ° C., and it can be seen that the temperature range where the molten fly ash liquefies is very wide. The molten fly ash is considered to adhere to the inner wall of the flue gas duct, which is a flue when condensed from the vaporized gas state, and therefore, it can be said that the temperature range in which such an adhesion phenomenon occurs is wide.
[0009]
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 passage area and the passage length in the flue to which the molten fly ash adheres are increased by the wide range of the temperature range where the molten fly ash is below the condensation point. For this reason, in the proposed blocking prevention technology, the exhaust gas duct has to be very long as long as it is intended to increase the collection efficiency of molten fly ash.
[0010]
Further, in the exhaust gas from the melting furnace, harmful dioxins are often generated in the region near 300 to 400 ° C. As a countermeasure, dioxins are generally removed with a bag filter in the exhaust gas aftertreatment process that is connected to the flue, but before the treatment with the bag filter, the exhaust gas is below the temperature at which dioxins are likely to be generated. By providing a cooling step for cooling to a minimum, the dioxin removal efficiency can be increased.
[0011]
Therefore, the object of the first invention of the present invention is to avoid the enlargement of the exhaust gas duct and to take measures to prevent the adhesion and accumulation of molten fly ash in a smaller space near the exhaust gas outlet. In addition to simplifying the structure of the flue section up to the exhaust gas aftertreatment process, and reducing the scale of the exhaust gas aftertreatment device leading to the bag filter from the conventional exhaust gas cooling process. Therefore, the present invention is to provide a method for preventing the melting furnace exhaust gas duct from being blocked, which can contribute to a significant reduction in the equipment cost of the melting furnace, and thus the entire incineration / melting equipment.
[0012]
In addition to the object of the first invention, the object of the second invention is the adhesion and deposition of molten fly ash on the part where the exhaust gas flow is likely to stagnate after the exhaust gas cooling part, such as the branch part of the exhaust gas duct. Therefore, it is possible to prevent the clogging of the melting furnace exhaust gas duct so as to ensure the stable continuous operation of the melting furnace.
[0013]
In addition, an object of the third invention is to provide a melting facility capable of effectively realizing the object of the first invention.
[0014]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the first invention of the present invention is characterized in that a cooling gas is sprayed on the exhaust gas at the outlet of the melting furnace before the molten fly ash contained in the exhaust gas starts to liquefy. It is what. Further, the second invention is an exhaust gas duct after the exhaust gas cooling part, which is a refractory having a high thermal conductivity on the inner wall of the exhaust gas duct corresponding to the part where the flow direction of the exhaust gas changes, It is characterized by sticking a material processed to a thickness such that the surface temperature is 300 ° C. or less.
[0015]
Here, the “exhaust gas at the melting furnace outlet” means high-temperature exhaust gas before liquefaction in the space passing through the outlet. Before the molten fly ash began to liquefy, the cooling gas was blown into the exhaust gas because the molten fly ash was positively condensed, solidified and further scattered in a smaller space immediately after the exhaust gas outlet. This is to prevent molten fly ash from adhering to the inner wall of the exhaust gas duct that follows and depositing to the maximum extent.
[0016]
Moreover, although the temperature of the exhaust gas in the space immediately after the tap outlet to the exhaust gas cooling unit is in a high temperature state of 1000 to 1200 ° C., it is preferable to maintain this temperature. This is to prevent blockage due to slag at the tap. As shown in FIG. 7, since the molten fly ash is vaporized in a high temperature region of 1000 to 1200 ° C., adhesion to the refractory surface does not become a problem.
[0017]
As mentioned above, all removal of dioxins generated in the flue gas from the melting furnace is done with a bag filter, but in order to improve the removal efficiency with the bag filter, the stage before the exhaust gas reaches the bag filter. Therefore, it is necessary to control the exhaust gas temperature on a large scale.
[0018]
In the present invention, the means for spraying the cooling gas to the exhaust gas applied before the molten fly ash is liquefied also has the same role as the conventional water cooling temperature control. That is, in order to exhibit the dioxin generation suppressing effect in addition to the effect of preventing the adhesion and accumulation of molten fly ash, the exhaust gas cooling section rapidly cools a high-temperature gas of about 1000 ° C. to about 200 ° C.
[0019]
If only the prevention of adhesion of molten fly ash to the inner wall of the exhaust gas duct is intended, cooling to about 600 ° C. is sufficient as can be seen from FIG. 7, but the temperature range where dioxins are likely to be formed is 300. Because it is in the vicinity of ˜400 ° C., cooling to about 200 ° C. at a stroke is effective in suppressing the generation of dioxins.
[0020]
Further, after the exhaust gas cooling section, measures should be taken in anticipation that the exhaust gas temperature control by the blowing of the cooling gas may become unstable. That is, if the exhaust gas temperature control becomes unstable, a temperature atmosphere in which the molten fly ash adheres to the inner wall of the exhaust gas duct may occur. In particular, the molten fly ash is likely to accumulate at a portion where the direction of the duct changes after the exhaust gas cooling section and the gas flow is likely to stagnate, for example, at a branching portion or a bent portion of the exhaust gas duct.
[0021]
In view of this point, the present inventors conducted various experiments on the construction contents of the refractory, and as a result, processed the refractory having a high thermal conductivity into a thin film so that the surface temperature of the refractory on the side of the exhaust gas flow path becomes as low as possible. As a result, it was confirmed that adhesion of molten fly ash hardly occurred. Therefore, as a second invention, after the exhaust gas cooling section, the inner wall of the exhaust gas duct is a refractory having a high thermal conductivity and processed to a thickness such that the surface temperature on the exhaust gas flow path side is 300 ° C. or lower. It is possible to adopt a peculiar solution to sticking. Thereby, the stable continuous operation | movement of a melting furnace can be ensured reliably.
[0022]
Further, the third invention is a melting facility provided with a tapping part for simultaneously tapping molten slag and exhaust gas at the lower part of the melting furnace for melting the material to be melted, from the tapping part immediately after the tapping part. An exhaust gas duct that extends downward is continuously provided, and 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 at the outlet, and further, the cooling gas is supplied to the cooling gas outlet nozzle. A cooling gas supply means is provided.
[0023]
Here, “providing at a position lower than the height of the outlet” means providing a cooling gas blowing nozzle so that the cooling gas can be blown out while the temperature in the duct is in a high temperature state of about 1000 to 1200 ° C. Means. 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 It is desirable to provide a cooling gas blowing nozzle within a range of about ~ 1.0 m.
[0024]
With the above configuration, it is possible to more small space adhesion of molten fly ash into the deposition prevention is applied molten facilities near the exhaust gas outlet of the melting furnace. Moreover, the preventive measure can also exhibit the dioxin generation | occurrence | production suppression effect. Therefore, exhaust gas post-treatment to simplify the structure of the smoke path unit to process, also aims to scale reduction of the conventional exhaust gas aftertreatment device, the melting furnace stable continuous operation economic melt equipment can keep the It can be.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic explanatory view showing an example in which the blocking prevention method and the melting equipment of the present invention are applied to an exhaust gas duct of a plasma melting furnace. From the outlet 2 of the plasma melting furnace 1, exhaust gas mixed with molten slag and molten fly ash is discharged. Since the furnace gas temperature of the melting furnace 1 is a high temperature of 1200 ° C. or higher, the slag is completely liquid, but in order to prevent clogging due to solidification of the molten slag due to the temperature drop when flowing down the tap outlet 2 As a structure that can supply the city gas E toward the port 2, the temperature in the duct near the exit of the tap port 2 can be maintained at a high temperature of about 1000 to 1200 ° C.
[0026]
In the exhaust gas cooling section, a high temperature gas of about 1000 ° C. is rapidly cooled to about 200 ° C. by blowing the cooling gas A supplied from the cooling gas supply means 9 through the blowing nozzle 7. 4, as shown in FIG. 2 (enlarged view of only the exhaust gas duct), in the stagnated portion of the exhaust gas flow around the blowout nozzle 7 of the cooling gas A, the molten fly ash is slightly icicle-shaped as shown by the oblique lines. Deposit and grow. However, the accumulation and growth of molten fly ash exceeding a certain level can be prevented, and the molten fly ash falls into the slag granulating tank 6.
[0027]
The problem here is whether or not the accumulation and growth of molten fly ash around the blowing nozzle 7 of the cooling gas A can be reliably suppressed, and it is necessary to grasp the conditions. The conditions under which molten fly ash accumulates and grows to some extent and falls due to its own weight or cooling gas blowing 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. .
[0028]
The application range of these parameters is clarified with reference to FIGS. The ○ mark in the figure indicates the case where the accumulation and growth of molten fly ash has converged to such an extent that it does not affect the stable continuous operation of the melting furnace, and the × mark indicates that the accumulation and growth of molten fly ash has converged. This shows the case where the continuous operation of the melting furnace is adversely affected because the amount of deposition is large or almost closed.
[0029]
FIG. 3 shows the results of examining the influence of the cooling gas blowing flow rate 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. FIG. As is clear from this figure, it can be seen that the larger the angle α formed between the direction perpendicular to the exhaust gas flow and the cooling gas blowing direction, the larger the cooling gas A blowing speed must be.
[0030]
The blowout angle α = 0 ° is considered to be ideal because the blowout speed is minimum, but when used in actual melting furnace equipment, depending on the flow rate of the cooling gas, the exhaust gas may flow backward toward the melting furnace. Since it may adversely affect driving, it is not preferable.
[0031]
FIG. 4 is a diagram showing the results of examining the influence on the accumulation and growth of molten fly ash when the cooling gas blowing angle α is set to 30 ° and the arrangement pitch of the blowing nozzles 7 is changed. It can be seen that the smaller the number of outlets, the more easily the molten fly ash adheres and grows in the meantime, and the cooling gas outlet speed must be increased.
[0032]
An exhaust gas treatment facility is installed after the exhaust gas cooling section. In FIG. 1, the location where the molten fly ash is likely to adhere because the exhaust gas flow tends to stagnate around the branch portion of the exhaust gas duct, that is, around the connection portion between the flue 8 leading to the exhaust gas treatment facility and the exhaust gas cooling unit ( For the part indicated by the alternate long and short dash line in the figure, a refractory having a high thermal conductivity and processed to a thickness such that the surface temperature on the exhaust gas flow path side is 300 ° C. or less is attached to the duct inner wall. Therefore, the accumulation and growth of molten fly ash are less likely to occur.
[0033]
The solidified molten fly ash is collected using a normal bag filter or the like. In this way, blockage of the exhaust gas duct due to adhesion and accumulation of molten fly ash is prevented, and stable continuous operation of the melting furnace is enabled.
[0034]
FIG. 5 is a schematic explanatory view showing another embodiment, and as an inner wall structure of the exhaust gas cooling section, a refractory having a high thermal conductivity, like the inner wall structure around the connection portion with the flue 8 described above. Shows an example of thinly constructed. Thus, by the cooling effect of the refractory surface by water cooling, it is possible to further suppress the adhesion of the molten fly ash to the periphery of the cooling gas blowing nozzle 7 and further enhance the effect of preventing the accumulation of molten fly ash.
[0035]
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. In such a configuration, harmful components (hydrogen chloride, etc.) in the exhaust gas and Since ash is mixed into the slag carry-out tank 6, there is a possibility that the quality of the solidified slag and the water quality when the slag carry-out tank 6 is used as a granulation tank are deteriorated.
[0036]
Therefore, as shown in FIG. 6, such a situation can be obtained by separately configuring the tap line 9 and the exhaust gas line 10 in the vicinity of the tap port 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. In the case of this form, it is preferable to keep the joining space portion between the tap line 9 and the exhaust gas line 10 as small as possible in order to maintain the high temperature around the tap port outlet.
[0037]
【The invention's effect】
As described above, according to the first invention of the present invention, the length of the exhaust gas duct is avoided, and adhesion and accumulation of molten fly ash can be prevented in a smaller space near the exhaust gas outlet, and this prevention is also achieved. In order to have a dioxin generation inhibitory effect together with the measures, the structure of the flue section up to the exhaust gas aftertreatment process is simplified, and the scale of the exhaust gas aftertreatment device leading to the bag filter from the conventional exhaust gas cooling section is reduced. As a result, the melting furnace and thus the incineration / melting equipment as a whole can be significantly reduced in equipment costs.
[0038]
Further, in addition to the effects of the first invention, the second invention is the addition of molten fly ash to a portion where the exhaust gas flow is likely to stagnate, such as a branch portion or a bent portion of the exhaust gas duct, after the exhaust gas cooling portion. It was possible to prevent deposition and ensure stable continuous operation of the melting furnace.
[0039]
Furthermore, a third invention, in short the exhaust gas outlet of the smoke path unit after configuration of the melting furnace in the melting equipment, deposition of molten fly ash, since it is assumed that enables prevention and suppressing generation of dioxin deposition, simplifying the structure of the smoke path unit to exhaust gas aftertreatment step, also aims to scale reduction of the conventional exhaust gas after-treatment device, and economical melting equipment capable of ensuring a stable continuous operation of the melting furnace I was able to.
[Brief description of the 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 the cooling gas blowing speed and the blowing angle on the deposition and growth of molten fly ash.
FIG. 4 is a diagram showing the results of examining the influence of the cooling gas blowing speed and the pitch of the blowing holes on the 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 a state of weight reduction with temperature change for molten fly ash.
FIG. 8 is a schematic cross-sectional view of a relevant part showing a conventional structure for preventing clogging of a melting furnace exhaust gas duct.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plasma melting furnace 2 Outlet 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

Claims (2)

Before the molten fly ash contained in the exhaust gas starts to liquefy, the cooling gas is blown against the exhaust gas at the exit of the melting furnace,
On the inner wall of the exhaust gas duct, which corresponds to the exhaust gas duct after the exhaust gas cooling part and corresponding to the part where the flow direction of the exhaust gas changes, is a refractory having a high thermal conductivity and the surface temperature on the exhaust gas channel side is 300 ° C. or lower. What is claimed is: 1. A method for preventing clogging of a melting furnace exhaust gas duct, characterized by sticking a material processed to such a thickness.   In a melting facility provided with a tapping part for simultaneously discharging molten slag and exhaust gas at the lower part of the melting furnace for melting the material to be melted, an exhaust gas duct directed downward from the tapping part is connected immediately after the tapping part In addition, a cooling gas blowing nozzle penetrating the wall surface of the exhaust gas duct is provided at a position lower than the height of the outlet in the outlet portion, and further a cooling gas supply means for supplying cooling gas to the cooling gas outlet nozzle is provided. Melting equipment characterized by.

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