JPH024191A - Temperature control of smelting furnace - Google Patents

Abstract

PURPOSE:To detect a furnace temperature correctly without being affected by downflow slag and control the temperature with excellent accuracy by controlling the supplying amount of fuel for a combustion burner based on the exhaust gas temperature of a smelting furnace for smelting thrown-in metal to be smelted in a high-temperature combustion chamber. CONSTITUTION:A temperature sensor 13, such as a thermocouple or the like, is provided at the part of an exhaust gas outlet port 6 for a smelting furnace A to detect the temperature of exhaust gas discharged out of a combustion chamber 1 by the temperature sensor 13. The temperature of the exhaust gas is given as the total amount of the sensitive heat of the exhaust gas generated by the combustion of fuel, the accumulated heat of refractories in the furnace and the like and is related directly to a furnace temperature. The detecting value of the sensor is compared with the value of a preset optimum furnace temperature in a furnace temperature control device 14 and a control signal is outputted to a flow rate regulating valve 12 based on the result of the comparison. According to this method, the opening degree of the flow rate control valve 12 as well as the supplying amount of fuel to a burner 2 are regulated whereby the furnace temperature may be controlled toward the optimum temperature.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a temperature control method for a melting furnace that melts waste such as sewage sludge and municipal garbage, its treated ash, coal ash, etc. at high temperature F. .

[Conventional technology]

A conventional melting furnace temperature ill I11 method will be explained with reference to FIG.

In the figure, A is a swirl 11-flow melting furnace, and the inside of a combustion chamber 1 leading to this melting furnace is heated by a burner 2 and maintained at a high temperature higher than the melt flow temperature of the material to be melted.

The material to be melted, such as coal ash, which comes out of the quantitative feeder 3 and is pumped by compressed air is mixed with the combustion air sent from the blower 4 and then introduced into the furnace, where it is swirled at a high temperature F in the combustion chamber 1. while turning into molten slag.

This molten slag flows down along the furnace wall and is collected in the slugbot 5 (or take-out conveyor) below the combustion chamber. Further, the combustion gas (exhaust gas) in the combustion chamber 1 is separated from the particles of the material to be melted, heads toward the exhaust gas outlet 6, and is discharged through the flue 7.

Furnace interior and furnace wall temperature of melting furnace A (hereinafter referred to as furnace temperature)
is above the melt flow temperature of the material to be melted and below the temperature regulated to protect refractories (for example, 1250°C to 1350°C in the case of fluidized incineration ash of lime-based dehydrated cake, hereinafter referred to as appropriate furnace temperature) need to be kept.

Since this furnace temperature changes depending on the supply amount of the material to be melted, etc., it is necessary to detect this furnace temperature and adjust the supply of burner fuel based on this to control the furnace temperature toward the appropriate furnace temperature. .

[Problem to be solved by the invention]

Conventionally, as this temperature control method, a temperature sensor 9 such as a thermal lightning pair is embedded in the furnace wall, the temperature sensor 9 indirectly detects the furnace wall temperature, and this detected value is used as the actual value by the furnace wall temperature calculator 10. It is corrected to a value equivalent to the furnace wall temperature and sent to the furnace temperature control device 11, where it is compared with a preset appropriate temperature value, and based on the comparison result, the flow rate control valve for adjusting the fuel supply groove for the burner 2 is The configuration is such that the fuel supply 1 is controlled by controlling the opening degree of the valve 12.

However, the conventional method of detecting the furnace wall temperature as described above has the following problems.

That is, during the melting operation, molten slag flows down along the furnace wall, forming a slab layer on the furnace wall. Since this slag layer has a lower thermal conductivity than the furnace wall, the furnace wall temperature calculation 310
The corrected temperature will be lower than the actual wall temperature (for example, if the slag layer is formed to a thickness of 10 mm, the corrected value will be about 80° C. lower than the actual value). In addition, if the refractory of the furnace wall is worn out due to a chemical reaction with slag, the corrected humidity will become higher than the actual temperature (for example, if the thickness of 10M is worn out, the corrected value will be about 30% higher than the actual temperature). ℃＾).

As described above, according to the conventional method of detecting humidity on the furnace wall where slag flows up, the detection error due to the influence of the flowing slab is large, resulting in poor control accuracy.

Further, when the temperature sensor 9 is exposed inside the furnace due to wear and tear on the furnace wall, there is a problem that the sensor 9 is damaged due to contact with particles of the material to be melted, resulting in a shortened lifespan.

Therefore, the present invention aims to reduce the influence of the furnace temperature by the falling slag (
The present invention provides a temperature control method for a melting furnace that can accurately detect and control the temperature with high precision without causing any damage, and can prevent damage to the temperature sensor and improve the life of the sensor.

[Means to solve the problem]

In the present invention, a temperature sensor is provided in the exhaust gas passage of a melting furnace in which a charged material to be melted is melted in a high-temperature combustion chamber, the temperature of the exhaust gas of the melting furnace is detected by this temperature sensor, and the combustion The supply of fuel to the burner is controlled.

[Effect]

In this way, since the exhaust gas temperature is detected which is unrelated to the flowing slag and is directly connected to the furnace temperature, the furnace temperature can be accurately detected without being influenced by the flowing slag. Therefore, the furnace temperature can be controlled with high precision.

Furthermore, since the temperature of the exhaust gas from which the particles have been separated is detected in the exhaust gas passage, there is no risk that the sensor will be damaged by contact with the particles.

〔Example) An embodiment of the present invention will be explained with reference to FIG.

In this example, the same parts as shown in Fig. 2, such as the basic structure of the melting furnace, the structure of supplying materials to be melted and fuel to the melting furnace, etc., are indicated with the same reference numerals as in Fig. 2, and the overlap The explanation will be omitted.

In this embodiment device, a temperature sensor 13 such as a thermocouple is used.
is provided at the exhaust gas outlet 6 to the melting furnace, and the temperature of the exhaust gas discharged from the combustion chamber 1 is detected by this combustion chamber sensor 13.

The temperature of this exhaust gas is determined by the temperature of the exhaust gas due to fuel combustion,
Since the temperature is directly connected to the furnace temperature (approximately equal to the furnace temperature), the detected value of the temperature sensor 13 is directly used as the furnace temperature, and is used as the furnace temperature. It is sent to the furnace temperature control device 14 without being subjected to any correction operation by the enhanki.

In this furnace temperature control device 14, a preset appropriate furnace temperature value is compared with this sensor detection value, and based on the comparison result, a control signal (opening increase or decrease) is sent to the flow rate control valve 12. signal).

As a result, the opening degree of the flow control valve 10 is adjusted, the fuel supply gutter to the burner 2 is adjusted, and the furnace temperature is controlled toward an appropriate temperature.

In this way, since the furnace temperature is detected using the exhaust gas temperature, which is unrelated to the flowing slag and is directly connected to the furnace temperature, the furnace temperature can be accurately detected without being affected by the flowing slag. Therefore, based on this accurate detected temperature, the fuel
l adjustment, that is, furnace temperature control, is performed with high precision. In addition, exhaust gas temperature has a correlation with fuel combustion, and changes during fuel supply are directly reflected in this exhaust gas temperature.
Control responsiveness is good, and control accuracy is further improved.

On the other hand, most of the particles of the material to be melted are separated from the combustion gas before the exhaust gas outlet 6 and descend, and the dust concentration is much lower at the exhaust gas outlet 6 than in the combustion chamber 1.
There is no risk that the temperature hinge 13 installed in this part will be damaged by contact with particles, and the life of the senna will be improved.

Incidentally, the air-fuel ratio of the burner 2 is set to a constant value (for example, 1.2) in order to improve thermal efficiency and fuel efficiency.
Particularly during negative pressure operation, the air-fuel ratio may fluctuate due to air entering the furnace.

Therefore, in this embodiment, an oxygen concentration sensor 15 for detecting the oxygen concentration in the exhaust gas is provided in the flue 7 through which the exhaust gas passes.
is provided, and the amount of combustion air is adjusted based on the detected value of this sensor 15.

3T, the oxygen concentration detected by the oxygen concentration sensor 15 is sent to the air-fuel ratio calculator 16. In this operator 16, the oxygen concentration set by the Mjllj concentration setting device 17 (for example, oxygen concentration 3.8% at an air-fuel ratio of 1.2) is set by the Mjllj concentration setting device 17.
) and the detected oxygen concentration to determine the target air-fuel ratio to make the detected oxygen concentration the set oxygen concentration. The amount of combustion air (0) required to achieve the target air-fuel ratio determined here, that is, the #3 set oxygen concentration, is sent to the air-fuel ratio control device!i18.

The air-fuel ratio control device 18 simultaneously receives the fuel flow rate command signal sent from the furnace temperature control m+ device 14 to the fuel flow rate control valve 12 for the above-mentioned furnace temperature control, and from the relationship with this fuel flow, The amount of combustion air required to achieve the target air-fuel ratio is determined, and an opening command (lfl
l command) is output as a signal.

In this way, the air-fuel ratio can be maintained at the most advantageous value in terms of thermal efficiency and fuel efficiency. According to experiments conducted by the present inventor, the fuel consumption rate (the amount of fuel required to raise the furnace temperature by 10° C.) was able to be reduced by 5 to 10% by the air-fuel ratio control described above.

By the way, the temperature sensor 13 that detects the exhaust gas temperature is not limited to the exhaust gas outlet 6 described above, but may be installed in the flue 7.

〔Effect of the invention〕

As described above, according to the present invention, a temperature sensor is provided in the exhaust gas passage of the melting furnace, and this temperature sensor detects the temperature of the exhaust gas, which is directly connected to the furnace temperature. The temperature can be detected at it Tll without being affected by the falling slag.Therefore, compared to the conventional method of detecting the furnace wall temperature, the furnace temperature can be controlled with higher accuracy.

Further, since the temperature sensor is installed in the exhaust gas passage where particles are separated and the powder U concentration is low, damage to the temperature sensor due to contact with particles can be prevented, and the sensor life can be improved.

FIG. 1 is a schematic configuration diagram of a melting furnace and a control system for explaining the present invention in detail, and FIG. 2 is a diagram corresponding to FIG. 1 for explaining a conventional method.

A... Melting furnace, 1... Combustion chamber, 2... Burner,
6... Exhaust gas outlet (exhaust gas passage), 12... Fuel flow rate control valve, 13... Temperature sensor, 14... Furnace temperature 1
, 1ull device.

Watch applicant Kobe Steel, Ltd. Representative Patent attorney Etsushi Kotani Patent attorney
1) Masamukai Patent Attorney Takao Ito

[Brief explanation of the drawing]

No. figure No. figure

Claims (1)

[Claims] 1. A temperature sensor is installed in the exhaust gas passage of the melting furnace that melts the material to be melted in the high-temperature combustion chamber, and this temperature sensor detects the exhaust gas temperature of the melting furnace.Based on this detected value, the combustion burner 1. A temperature control method for a melting furnace, the method comprising controlling the amount of fuel supplied to a melting furnace.