JP3821309B2 - Method and apparatus for preventing blockage of exhaust duct of fly ash melting furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust duct blockage prevention method and apparatus for a fly ash melting furnace for melting and stabilizing fly ash generated from a waste incinerator.
[0002]
[Prior art]
Incineration ash and dust collection ash (hereinafter referred to as “fly ash”) generated from a waste incinerator is melted in a melting furnace to reduce the volume and make it harmless. As the melting furnace, an arc furnace, a plasma arc furnace, a resistance furnace, an induction furnace, a burner furnace, etc. are used, and the exhaust gas generated when melting the incineration ash and fly ash is exhaust gas established on the furnace wall of the melting furnace It is discharged out of the furnace through the mouth. An exhaust duct is connected to the exhaust port, and the exhaust gas is led to the gas cooling tower by the exhaust duct, and further led to the dust collector to separate and recover the solid content in the exhaust gas. The exhaust gas from which the solid content has been removed is then detoxified with a chemical solution or the like and discharged to the atmosphere.
[0003]
[Problems to be solved by the invention]
By the way, since fly ash contains a large amount of low-melting-point inorganic substances and heavy metals, when low-melting-point inorganic substances and heavy metals are melted in a melting furnace, the low-melting-point inorganic substances and heavy metals are exhaust gas systems, especially the exhaust port and gas cooling. There is a problem in that it adheres and accumulates on the wall surface in the exhaust duct connecting to the tower, and finally the exhaust duct is blocked, making it impossible to operate for a long time.
[0004]
In order to prevent such blockage of the exhaust duct, a large amount of air is blown by providing an air blowing port for exhaust gas cooling on the peripheral surface of the exhaust port. According to this method, the temperature of the exhaust gas is lowered, and the concentration of dust in the exhaust gas becomes lean, which is effective in preventing the exhaust duct from being blocked. However, if a large amount of air is blown unnecessarily, the total amount of exhaust gas increases and the amount of exhaust gas detoxification increases, which makes the exhaust system large and uneconomical.
[0005]
The present invention has been made in view of the above-described situation, and an object of the present invention is to provide a method and an apparatus for optimizing the amount of blown air necessary for effectively and economically preventing the exhaust duct from being blocked. Is to provide.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the exhaust duct blockage prevention method for a fly ash melting furnace according to the present invention, when exhaust gas generated during operation of the fly ash melting furnace is discharged outside the furnace by the exhaust duct, the peripheral surface of the exhaust duct In the exhaust duct blockage prevention method performed by blowing exhaust gas cooling air from an air inlet provided in the exhaust duct, the chloride concentration in the exhaust gas in the exhaust duct is determined by the exhaust gas temperature in the exhaust duct, and the exhaust duct inner surface The amount of the exhaust gas cooling air blown in is adjusted so as to be less than a limit concentration at which chloride adheres.
[0007]
In addition, the exhaust duct blockage prevention device for the fly ash melting furnace of the present invention,
An exhaust duct connected to an exhaust port provided in the fly ash melting furnace;
An air inlet provided on the peripheral surface of the exhaust duct;
An air blowing device provided in connection with the air blowing port;
A chloride concentration measuring device for measuring a chloride concentration in the exhaust gas in the exhaust duct;
An exhaust gas temperature measuring device for measuring the exhaust gas temperature in the exhaust duct;
A cooling air conditioner that regulates the operation of the air blowing device according to the output of the chloride concentration measuring device in the exhaust gas and the output of the exhaust gas temperature measuring device;
It is characterized by providing.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the waste to be melted is a mixture of fly ash and incineration ash that are generated when municipal waste, industrial waste, or the like is incinerated. An arc furnace, a plasma arc furnace, a resistance furnace, an induction furnace, a burner furnace, or the like can be used as a melting furnace (referred to as a fly ash melting furnace) used for melting such waste.
[0009]
The method and apparatus for preventing exhaust duct clogging of a fly ash melting furnace according to the present invention was invented based on the following findings obtained as a result of earnest research on the cause of clogging of the exhaust duct in the fly ash melting furnace. .
In other words, fly ash contains a large amount of chlorides such as NaCl and KCl, but when this is melted in a fly ash melting furnace, the chloride in the fly ash is heated to a high temperature in the melting furnace. Volatilize. Also, when fly ash is mixed with incineration ash and melted, the chloride in the fly ash reacts with component elements contained in the incineration ash, particularly zinc, to form a low melting point chloride such as ZnCl ₂ and volatilize. .
[0010]
Volatilized chloride is sucked by an exhaust gas fan provided in the exhaust gas system, and is carried by the exhaust gas together with other dusts to reach the exhaust duct. The volatilized chloride is cooled here, liquefied and adhered to the inner surface of the exhaust duct, and further cooled and solidified. Other dust or the like also adheres to the liquid chloride, further promoting the growth of the adhering matter and eventually closing the exhaust duct.
[0011]
As described above, the clogging of the exhaust duct occurs due to the chloride contained in the exhaust gas being liquefied and adhering to the inner surface of the exhaust duct. According to the results of the experiment, the conditions under which the chlorides cause adhesion in the exhaust duct depend on the temperature of the exhaust gas in the exhaust duct and the concentration of chloride contained in the exhaust duct. The limit concentration causing adhesion in the duct (hereinafter referred to as “limit chloride concentration”) decreases as the exhaust gas temperature in the exhaust duct increases.
[0012]
Therefore, in the fly ash melting furnace exhaust duct blockage prevention method of the present invention, first, the exhaust gas temperature in the exhaust duct and the concentration of chloride contained in the exhaust gas are measured, and the exhaust gas temperature and the chloride concentration in the exhaust gas are measured. Examine the relationship. When the chloride concentration in the exhaust gas is equal to or higher than the limit chloride concentration, the exhaust gas cooling air is blown from the air blowing port, and the exhaust gas temperature and the chloride concentration in the exhaust gas are measured again to investigate their relationship. Thus, the amount of exhaust gas cooling air blown is adjusted so that the chloride concentration in the exhaust gas is always less than the limit chloride concentration.
[0013]
Since the value of the limit chloride concentration varies depending on the characteristics of the equipment including the melting furnace and exhaust system to be used, it is desirable to grasp the relationship between the exhaust gas temperature and the limit chloride concentration for the equipment to be used in advance.
The method for controlling the adhesion of chloride to the inner surface of the exhaust duct by the limit chloride concentration has been described above. The exhaust gas temperature is the limit temperature at which chloride adheres to the inner surface of the exhaust duct (hereinafter referred to as the “limit exhaust gas temperature”). The amount of exhaust gas cooling air blown may be adjusted so that the exhaust gas temperature is lower than the limit exhaust gas temperature.
[0014]
In the fly ash melting furnace blockage prevention apparatus of the present invention, the exhaust duct is connected to an exhaust port provided in the fly ash melting furnace, and the exhaust gas generated in the fly ash melting furnace is transferred from the fly ash melting furnace to a gas cooling tower or the like. Guide to the process.
An air blowing port is provided on the peripheral surface of the exhaust duct, an air blowing device is connected to the air blowing port, and air is blown into the exhaust duct from the air blowing port by operating the air blowing device.
[0015]
A chloride concentration measuring device and an exhaust gas temperature measuring device are provided in the exhaust duct, and the chloride concentration in the exhaust duct and the exhaust gas temperature in the exhaust duct are measured.
The cooling air conditioner uses the measured chloride concentration in the exhaust duct and the exhaust gas temperature in the exhaust duct so that the chloride concentration in the exhaust gas becomes less than the limit chloride concentration (or the exhaust gas temperature is The operation of the air blowing device is controlled so that the exhaust gas cooling air blowing amount is adjusted so that the temperature becomes lower than the limit exhaust gas temperature.
[0016]
【Example】
Examples of the present invention will be described below.
FIG. 2 is a sectional view schematically showing an embodiment of the present invention in relation to an arc furnace, and FIG. 1 is a partially enlarged longitudinal sectional view of the same embodiment as FIG. As shown in FIG. 2, the arc furnace 11 includes a furnace main body 21 and a furnace lid 31 attached to the furnace main body 21. A molten slag discharge port 23 is opened on the side wall 22 of the furnace body 21. A waste input port 33 and an exhaust port 34 are opened in the ceiling wall 32 of the furnace lid 31. Further, three electrodes 51 are inserted into the furnace through the ceiling wall 32 of the furnace lid 31. A jacket 61 capable of circulating a cooling fluid is provided on the outer surface of the furnace lid 31, and an exhaust port 34 is opened in the ceiling wall 32 of the furnace lid 31 in the vertical direction.
[0017]
An exhaust duct 41 is connected to the exhaust port 34. As shown in FIG. 1, a plurality of air blowing ports 42 penetrating the tube wall of the exhaust duct 41 are provided on a part of the peripheral surface of the exhaust duct 41. An air introduction path 43 is provided so as to surround a large number of air blowing ports 42. Further, a jacket 44 that surrounds the outer periphery of the air introduction path 43 and is capable of circulating cooling water is provided. The cooling air guided by the air introduction path 43 is blown from the air blowing port 42, passes through the exhaust duct 41, and is sucked together with the exhaust gas by an exhaust gas fan (not shown) connected to the downstream side of the exhaust duct 41.
[0018]
The chloride concentration measuring device 71 and the thermometer 73 are installed outside the exhaust duct 41, and the chloride concentration measuring terminal 72 and the temperature detecting terminal 74 are inserted into the exhaust duct 41 through the end plate 45 of the exhaust duct 41. To do.
An automatic valve 82 is interposed in an air introduction pipe 81 connected to an air supply source (not shown) and connected to the air introduction path 43. On the other hand, the chloride concentration measuring device 71 and the thermometer 73 are connected to the cooling air conditioner 91, and the cooling air conditioner 91 is connected to the automatic valve 82. When the chloride concentration measured by the chloride concentration measuring device 71 is equal to or higher than the limit chloride concentration obtained from the exhaust gas temperature measured by the thermometer 73, it is automatically detected by a signal output from the cooling air conditioner 91. The opening degree of the valve 82 is adjusted, and the required cooling air is blown from the air blowing port 42 so that the chloride concentration in the exhaust gas becomes the critical chloride concentration.
[0019]
FIG. 3 shows the result of examining the relationship between the exhaust gas temperature at which clogging occurs in the exhaust duct and the chloride concentration in the exhaust gas when the waste containing various fly ash components is melted in the experimental furnace of the present invention. . As can be seen from FIG. 3, the exhaust duct was not blocked by setting the chloride concentration and temperature lower than the blockage limit line.
In the demonstration furnace of the present invention with a processing capacity of 3 ton / day (the exhaust duct blockage limit condition of the demonstration furnace according to the preliminary test was an exhaust gas temperature of 160 ° C. and a chloride concentration of 20 g / Nm ³ ), an air blowing amount of 250 m When exhaust gas temperature is 210 ° C and chloride concentration is 27.2g / Nm ³ at ³ / hr, the exhaust duct is clogged after 4 days of operation, but exhaust gas temperature is 125 ° C and chloride concentration is 12.6g / Nm ³ . Therefore, by setting the air blowing rate to 650 m ³ / hr, the exhaust duct was not blocked even during the operation for 5 months or more.
[0020]
【The invention's effect】
As described above, according to the method and apparatus for preventing exhaust duct blockage of the fly ash melting furnace of the present invention, the exhaust duct is prevented from being blocked when melting waste containing fly ash and fly ash in the melting furnace. Thus, the exhaust gas can be smoothly discharged continuously.
[0021]
Further, in the method and apparatus for preventing exhaust duct blockage of the fly ash melting furnace of the present invention, an appropriate amount of exhaust gas cooling air is provided so that the chloride concentration in the exhaust gas in the exhaust duct becomes an appropriate value corresponding to the exhaust gas temperature. Since it is only necessary to blow in, the amount of cooling air used can be suppressed to the minimum necessary amount. Therefore, it is possible to reduce the amount of gas processing in subsequent processes such as exhaust gas cooling, dust collection, and washing, which is extremely economical.
[Brief description of the drawings]
FIG. 1 is a partially enlarged longitudinal sectional view showing an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view schematically showing an embodiment of the present invention in relation to an arc furnace.
FIG. 3 is a characteristic diagram showing the relationship between the exhaust gas temperature at which the exhaust duct is clogged and the chloride concentration in the exhaust gas in an example of the present invention.
[Explanation of symbols]
11 Arc furnace 21 Furnace body 22 Side wall 23 Molten slag discharge port 31 Furnace lid 32 Ceiling wall 33 Waste input port 34 Exhaust port 41 Exhaust duct 42 Air inlet port 43 Air introduction path 44 Jacket 45 End plate 51 Electrode 61 Jacket 71 Chloride Concentration measuring device 72 Chloride concentration measuring terminal 73 Thermometer 74 Temperature detecting terminal 81 Air introducing pipe 82 Automatic valve 91 Air conditioning device for cooling

Claims (4)

In the exhaust duct blockage prevention method in which exhaust gas generated during operation of the fly ash melting furnace is discharged outside the furnace by an exhaust duct, and exhaust gas cooling air is blown from an air blowing port provided on the peripheral surface of the exhaust duct.
The exhaust gas temperature in the exhaust duct and the chloride concentration in the exhaust duct are measured, the chloride concentration in the exhaust duct in the exhaust duct is determined by the exhaust gas temperature in the exhaust duct, and chloride is present on the inner surface of the exhaust duct. When the concentration is greater than the limit chloride concentration to be adhered, the amount of the exhaust gas cooling air blown is increased so that the chloride concentration in the exhaust gas in the exhaust duct is less than the limit chloride concentration. A method of preventing exhaust duct blockage in a fly ash melting furnace, characterized by adjusting an amount of cooling air blown. In the exhaust duct blockage prevention method in which exhaust gas generated during operation of the fly ash melting furnace is discharged outside the furnace by an exhaust duct, and exhaust gas cooling air is blown from an air blowing port provided on the peripheral surface of the exhaust duct.
The exhaust gas temperature in the exhaust duct and the concentration of chloride in the exhaust duct are measured, the exhaust gas temperature in the exhaust duct is determined by the chloride concentration in the exhaust duct in the exhaust duct, and chloride adheres to the inner surface of the exhaust duct. When the exhaust gas temperature is equal to or higher than the limit exhaust gas temperature, the blowing amount of the exhaust gas cooling air is increased, and the exhaust gas temperature in the exhaust duct is adjusted to be lower than the limit exhaust gas temperature. How to prevent exhaust duct blockage in the furnace. An exhaust duct connected to an exhaust port provided in the fly ash melting furnace;
  An air inlet provided on the peripheral surface of the exhaust duct;
  An air blowing device provided in connection with the air blowing port;
  A chloride concentration measuring device for measuring a chloride concentration in the exhaust gas in the exhaust duct;
  An exhaust gas temperature measuring device for measuring the exhaust gas temperature in the exhaust duct;
  When the output of the chloride concentration measuring device in the exhaust gas is determined by the exhaust gas temperature in the exhaust duct and is equal to or higher than the limit chloride concentration at which chloride adheres to the inner surface of the exhaust duct, the output in the exhaust gas A cooling air conditioner for increasing the amount of blowing of the exhaust gas cooling air so that the output of the chloride concentration measuring device is less than the limit chloride concentration;
  An exhaust duct blockage prevention device for a fly ash melting furnace, comprising: An exhaust duct connected to an exhaust port provided in the fly ash melting furnace;
  An air inlet provided on the peripheral surface of the exhaust duct;
  An air blowing device provided in connection with the air blowing port;
  A chloride concentration measuring device for measuring a chloride concentration in the exhaust gas in the exhaust duct;
  An exhaust gas temperature measuring device for measuring the exhaust gas temperature in the exhaust duct;
  When the output of the exhaust gas temperature measurement device is determined by the chloride concentration of the exhaust gas in the exhaust duct and is equal to or higher than the limit exhaust gas temperature at which chloride adheres to the inner surface of the exhaust duct, the output of the exhaust gas temperature measurement device A cooling air conditioner that increases the amount of the exhaust gas cooling air blown so that the temperature becomes less than the limit exhaust gas temperature,
  An exhaust duct blockage prevention device for a fly ash melting furnace, comprising:

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