JP2004271041A - Melting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To operate a melting furnace in a state in which temperatures of a revolving melting chamber and a weld pool chamber are kept constant as much as possible. <P>SOLUTION: This melting furnace comprises a thermometer 17a for detecting a temperature of the circular melting chamber 3 and a thermometer 17b for detecting a temperature of the weld pool chamber 4, and the detected temperatures by these thermometers 17a, 17b are respectively compared with predetermined set temperatures, so that the horizontal spiral flow H is strengthened, and a retention time of a combustible component in the circular melting chamber 3 is elongated, when a degree of lowering of the detected temperature from the set temperature in the circular melting chamber 3 is higher than that in the weld pool chamber 4, and a downward spiral flow V is strengthened, and a retention time of the combustible component in the circular melting chamber 3 is shortened, when the degree of lowering of the detected temperature from the set temperature in the weld pool chamber 4 is higher than that in the revolving melting chamber 4. Whereby the melting furnace can be operated in a state that the temperatures of the circular melting chamber 3 and the weld pool chamber 4 can be kept constant as much as possible by increasing a combustion degree of the combustible component in the chamber of higher temperature lowering degree. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melting furnace for melting incombustible components discharged from a pyrolysis furnace by using combustion heat of a pyrolysis gas.
[0002]
[Prior art]
The melting furnace, which introduces the incombustible components and pyrolysis gas discharged from the pyrolysis furnace and melts the noncombustible components using the combustion heat of the pyrolysis gas, has a swirl melting chamber for melting the noncombustible component, The upper part of the swirling melting chamber is provided with nozzles for combustion air and pyrolysis gas forming a downward swirling flow, and the swirling melt below this top There is one in which a nozzle for combustion air that forms a horizontal swirling flow is provided in an upper part of a chamber (for example, see Patent Documents 1 and 2).
[0003]
The non-combustible components discharged from the pyrolysis furnace are introduced as fly ash mixed into the pyrolysis gas or as pulverized powder from the top or upper part of the swirling melting chamber. Further, unburned components such as char are also mixed into the pyrolysis gas, and the unburned components are also mixed into unburned components to be pulverized.
[0004]
The amount of pyrolysis gas generated in the pyrolysis furnace constantly varies depending on the type of waste or the like to be treated, and the proportion of components such as combustible gas, unburned components, and non-burned components contained in the pyrolysis gas also varies. In addition, when a pulverized non-combustible component is also introduced, the ratio of the unburned component contained therein also varies. In the method described in Patent Document 2, a part of the pyrolysis gas is extracted and introduced into the introduction path of the pyrolysis gas to the melting furnace and burned with air, and the theoretical air amount of the pyrolysis gas is detected from the flame temperature. A pyrolysis gas sensor is provided, and the supply amount of combustion air is controlled based on the detection output so that the pyrolysis gas having a variable component ratio is completely burned in the melting furnace.
[0005]
[Patent Document 1]
JP-A-9-243027 (pages 2-4, FIG. 1)
[Patent Document 2]
JP-A-11-304129 (page 4-6, FIG. 1-3)
[0006]
[Problems to be solved by the invention]
The method of completely burning the pyrolysis gas by controlling the supply amount of the combustion air as described above can effectively utilize the combustion heat for melting the non-combustible component. Since the proportion of combustible components such as unburned components constantly varies depending on the type of waste or the like to be treated in the pyrolysis furnace, the amount of heat generated when these combustible components are completely burned also varies greatly. For this reason, there is a problem that it is difficult to operate the swirling melting chamber and the molten pool chamber of the melting furnace at a constant temperature. That is, if the temperature in the furnace is too high, the life of the melting furnace is shortened, and if the temperature in the furnace is too low, the melting of incombustible components becomes insufficient.
[0007]
According to the technology described in Patent Literature 2, when the combustion gas temperature is equal to or lower than the melting temperature of the non-combustible component, the calorific value is higher than the combustion gas based on the outputs of the pyrolysis gas sensor and the furnace temperature sensor. Although supplementary fuel is supplied and the refueling is shut off when the furnace temperature is higher than the allowable temperature, this method is not a basic solution when the furnace temperature is too high.
[0008]
Therefore, an object of the present invention is to make it possible to operate a melting furnace while keeping the temperature of a swirling melting chamber or a melting pool chamber as constant as possible.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a swirl melting chamber that introduces a non-combustible component and a pyrolysis gas discharged from a pyrolysis furnace and melts the non-combustible component with the combustion heat of the pyrolysis gas. The upper part of the swirling melting chamber is provided with a combustion air nozzle and a pyrolysis gas introduction nozzle that form a downward swirling flow. In a melting furnace provided with a combustion air nozzle that forms a horizontal swirling flow in the horizontal direction, a thermometer that detects the temperature of the swirling melting chamber, and a temperature of the melting pool chamber, A thermometer to be detected is provided, and the temperature detected by each of these thermometers in each of the chambers is compared with a preset set temperature for each of the thermometers. Is larger than the molten pool chamber The strong horizontal swirling flow, when towards the molten pool chamber is greater than the swirling-type slagging chamber adopts the configuration to strengthen the downward swirling flow.
[0010]
The present inventors have observed fluctuations in the furnace temperature of the melting furnace, and as a result, the tendency of each temperature fluctuation of the swirl melting chamber and the molten pool chamber does not necessarily match, and even when the temperature of the swirl melting chamber is rising. Regardless, it has been found that the temperature of the molten pool chamber often drops, or conversely, the temperature of the molten pool chamber rises significantly even though the temperature of the swirling melt chamber does not change much. This phenomenon is because the pyrolysis gas is introduced from the top of the swirling melting chamber as a downward swirling flow, so when its flammable components are small, these are burned out only in the swirling melting chamber, and when there are many flammable components, It is considered that the amount of combustion in the swirl melting chamber hardly changed, and the amount of combustion in the molten pool chamber increased. Further, it is considered that the degree of combustion of the combustible components in each of these chambers also changes depending on the ratio and size of the solid unburned portion in the pyrolysis gas.
[0011]
Therefore, utilizing the fact that the tendency of the temperature fluctuation between the swirling melting chamber and the molten pool chamber is different, the detected temperature of each of these chambers is compared with a preset set temperature, and the detected temperature is calculated from the set temperature. When the amount of reduction is larger in the swirl melting chamber than in the molten pool chamber, the horizontal swirling flow is strengthened to increase the residence time of the combustible components in the swirling melting chamber, and the molten pool chamber is more than the swirling melting chamber. When the temperature is also large, the descending swirl flow is strengthened and the residence time of the combustible component in the swirl melting chamber is shortened, so that the degree of combustion of the combustible component in the chamber with the larger temperature decrease is increased. The temperature of the molten pool chamber was kept as constant as possible.
[0012]
By providing the pyrolysis gas introduction nozzle also in the upper part of the swirling melting chamber that forms the horizontal swirling flow, the degree of freedom of adjusting the residence time of the combustible component in the swirling melting chamber can be increased.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment. This melting furnace introduces the pyrolysis gas 2 discharged from the pyrolysis furnace 1 and melts the non-combustible components such as fly ash contained in the pyrolysis gas 2, and the molten non-combustible component is A combustion-air nozzle 6 and a pyrolysis gas that form a downward swirling flow V around a burner 5 that is provided with a molten pool chamber 4 that flows down and accumulates upward and downward, and that is attached downward at the top of the swirling melting chamber 3. An introduction nozzle 7 is provided, and a plurality of combustion air nozzles 8 for forming a horizontal swirl flow H are provided above the swirl melting chamber 3 below the top. The combustion air is supplied from the respective blowers 9a, 9b to the respective nozzles 6, 8.
[0014]
The molten pool chamber 4 is provided with a weir 11 for storing a slag 10 in which incombustible components are melted, and an auxiliary burner 12 is provided on a ceiling thereof. The molten slag 10 overflowing from the weir 11 flows down from the gutter 13 to the lower cooling pit (not shown) along the downflow path 14, and the high-temperature exhaust gas 15 generated in the furnace is provided on the wall of the downflow path 14. It is discharged from the discharge port 16 to a discharge duct.
[0015]
Each of the swirling melting chamber 3 and the melting pool chamber 4 is provided with three thermometers 17a and 17b for detecting the furnace temperature in the upper, middle, and lower portions, respectively. Also, near the inlet of the discharge port 16, the exhaust gas concentration meter 18 for detecting the concentration of incomplete combustion components such as CO and NO _X in the high-temperature exhaust gas 15 is provided. The detection outputs of the thermometers 17a and 17b and the exhaust gas concentration meter 18 are input to a controller 19, and the controller 19 supplies the combustion air from the blowers 9a and 9b to the nozzles 6 and 8 based on the detection results. The quantities Q ₁ and Q ₂ are controlled.
[0016]
FIG. 2 is a flowchart showing a part of an algorithm of control by the controller 19. The controller 19, the incomplete combustion component in the high-temperature exhaust gas 15, for example, and the upper limit value A _U concentration A of CO, the furnace temperature theta ₁ of the swirling melter 3 and molten pool chamber _4, theta ₂ target setting The values θ _1S and θ _2S are stored in advance. In this embodiment, each of the target set values θ _1S and θ _2S is set to 1300 ° C.
[0017]
The controller 19, first, the concentration A of the incomplete combustion component detected by the exhaust gas concentration meter 18 is compared with the upper limit value A _U, when the concentration A exceeds the upper limit value A _U, to the nozzles 6, 8 The supply amounts Q ₁ and Q ₂ of the combustion air are uniformly increased.
[0018]
Next, the controller 19 averages the outputs of the thermometers 17a and 17b, respectively, and sets these average values as the furnace temperatures θ ₁ and θ ₂ of the swirl melting chamber 3 and the molten pool chamber 4, respectively. The amount of decrease Δθ ₁ (= θ _1S −θ ₁ ) and Δθ ₂ (= θ _2S −θ ₂ ) from the set values θ _1S and θ _2S are calculated. Further, these reduction amounts Δθ ₁ , Δθ ₂ are compared in magnitude, and when Δθ ₁ > Δθ ₂ , the ratio Q ₁ / Q ₂ of the supply amounts Q ₁ , Q ₂ of the combustion air is reduced, and Δθ ₁ When <Δθ ₂ , the ratio Q ₁ / Q ₂ is increased. That is, when the temperature decrease amount Δθ ₁ of the swirl melting chamber 3 is large, the ratio of the supply amount Q ₂ of the combustion air supplied to the nozzle 8 is increased to strengthen the horizontal swirl flow H, and the temperature of the molten pool chamber 4 is increased. when reduction amount [Delta] [theta] ₂ is large, increase the ratio of the supply amount to Q ₁ combustion air supplied to the nozzle 6, which strongly downward swirling flow V.
[0019]
In the above-described embodiment, the ratios of the supply amounts Q ₁ and Q ₂ are constantly controlled so that the in-furnace temperatures θ ₁ and θ ₂ of the swirl melting chamber 3 and the molten pool chamber 4 become equal. It is also possible to control the ratio between the supply amounts Q ₁ and Q ₂ only when the values of θ ₁ and θ ₂ are out of the predetermined range. For example, the upper and lower limit temperatures θ _U and θ _L of the swirling melting chamber 3 and the molten pool chamber 4 are set to 1450 ° C. and 1250 ° C., which are the same temperature, respectively. Then, when one of the furnace temperatures θ ₁ and θ ₂ deviates from the upper and lower limit temperatures θ _U and θ _L , the ratio of the supply amounts Q ₁ and Q ₂ is controlled so that the deviated furnace temperature Is set equal to the other furnace temperature within the range of the upper and lower limit temperatures θ _U and θ _L.
[0020]
FIG. 3 shows a second embodiment. The basic configuration of this melting furnace is the same as that of the first embodiment, and a branch is provided in the introduction path of the pyrolysis gas 2 from the pyrolysis furnace 1 to the pyrolysis gas introduction nozzle 7 and is branched. Is connected to a pyrolysis gas introduction nozzle 20 that forms a horizontal swirl flow H provided in the upper part of the swirl melting chamber 3, and dampers 21a and 21b are provided in each branched introduction path. different.
[0021]
The opening degree of each of the dampers 21a and 21b is controlled by a controller 19. In the case of this embodiment, the control of the ratio Q ₁ / Q ₂ of the supply amount of the combustion air in the first embodiment. in addition to, when the temperature decrease amount [Delta] [theta] ₁ of the swirling-type slagging chamber 3 is large, and strong horizontal swirling flow H by increasing the opening degree of the damper 21b, when a large temperature decrease amount [Delta] [theta] ₂ of the molten pool chamber 4 The opening degree of the damper 21a is increased to increase the downward swirling flow V.
[0022]
In each of the above-described embodiments, only the incombustible component contained in the pyrolysis gas is melted. However, the melting furnace according to the present invention can also be employed in a type in which pulverized incombustible component is also introduced.
[0023]
【The invention's effect】
As described above, the melting furnace of the present invention is provided with the thermometer for detecting the temperature of the swirling melting chamber and the thermometer for detecting the temperature of the molten pool chamber, and detects the detected temperature of each chamber by each of these thermometers. When the amount of decrease in the detected temperature from the set temperature is larger than that in the molten pool chamber, the horizontal swirl flow is strengthened and the combustible component is swirled. As the residence time in the melting chamber is lengthened, and when the molten pool chamber is larger than the swirling melting chamber, the descending swirling flow is strengthened to shorten the residence time of the combustible component in the swirling melting chamber. By increasing the degree of combustion of combustible components in the room with the largest temperature drop, maintaining the temperature of the swirl melting chamber and the molten pool chamber as constant as possible, extending the durable life of the furnace and efficiently melting non-combustible components be able to.
[0024]
By providing the pyrolysis gas introduction nozzle also in the upper part of the swirling melting chamber that forms the horizontal swirling flow, the degree of freedom of adjusting the residence time of the combustible component in the swirling melting chamber can be increased.
[Brief description of the drawings]
1 is a longitudinal sectional view showing a melting furnace of a first embodiment; FIG. 2 is a flowchart showing an algorithm of a controller of FIG. 1; FIG. 3 is a longitudinal sectional view showing a melting furnace of a second embodiment; Description】
DESCRIPTION OF SYMBOLS 1 Pyrolysis furnace 2 Pyrolysis gas 3 Rotating melting chamber 4 Melting pool chamber 5 Burner 6 Air nozzle 7 Pyrolysis gas introduction nozzle 8 Air nozzles 9a, 9b Blower 10 Melting slag 11 Weir 12 Auxiliary burner 13 Gutter 14 Downflow path 15 Hot exhaust gas 16 Outlet 17a, 17b Thermometer 18 Exhaust gas concentration meter 19 Controller 20 Pyrolysis gas introduction nozzle 21a, 21b Damper

Claims (2)

A swirl melting chamber that introduces non-combustible components and pyrolysis gas discharged from the pyrolysis furnace and melts the non-combustible components using the combustion heat of the pyrolysis gas, and a molten pool chamber where the molten non-combustible components flow down and accumulate The combustion air nozzle and the pyrolysis gas introduction nozzle that form a downward swirling flow are provided at the top of the swirling melting chamber, and a horizontal orientation is provided above the swirling melting chamber below the top. In a melting furnace provided with a combustion air nozzle for forming a horizontal swirling flow, a thermometer for detecting a temperature of the swirling melting chamber and a thermometer for detecting a temperature of the melting pool chamber are provided. The detected temperature of each chamber is compared with a preset set temperature for each, and the amount of decrease in the detected temperature from the set temperature is greater when the swirl melting chamber is larger than the molten pool chamber. The swirling flow is strengthened and the molten pool chamber Melting furnace when it is greater than the swirling-type slagging chamber, characterized in that so as to increase the said descending swirl flow. The melting furnace according to claim 1, wherein the pyrolysis gas introduction nozzle is provided also in an upper part of the swirling melting chamber that forms the horizontal swirling flow.

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