JP2002206737A - Device and method for generating hot air - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heat largely-fluctuating exhaust gas to a fixed given temperature so as to generate hot air in which less amount of CO is mixed. SOLUTION: Feed rate of fuel is controlled by a fuel control valve 3 before fed to a burner 1 in a primary combustion chamber. Thus fed fuel is mixed with combustion air which is supplied from a combustion air blower 2, with the feed rate being controlled by a differential pressure control damper 5 or the like, to the burner 1 through a combustion air damper 7 and a combustion air duct 6 for primary combustion for generating primary combustion gas. The primary combustion gas is mixed with secondary combustion air that has been preheated in a secondary combustion air supply chamber which is provided at the periphery of a primary combustion chamber and supplied through a blowing nozzle 13 which is provided around the exit of the primary combustion chamber for secondary combustion for generating hot air. Then detection is made as to the differential pressure between the combustion air before being separated into the primary combustion air and the secondary combustion air, and the hot air at the hot air exit. The feed rate of the combustion air is controlled so that the differential pressure is made constant, followed by separate combustion of the combustion air by primary and secondary to generate hot air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot air generator used for detoxification of exhaust gas and a control method thereof.

[0002]

2. Description of the Related Art In recent years, it has become necessary to reduce harmful substances in exhaust gas due to environmental pollution problems and the like, and various measures have been studied. Among them, the catalytic combustion type has been spotlighted. As the catalytic combustion method referred to here, for example, heated exhaust gas is placed inside a tower (catalyst tower) having a plurality of layers in which a metal catalyst is supported on a honeycomb-shaped ceramic material (catalyst carrier). There is a method in which the exhaust gas is brought into contact with a catalyst, and harmful substances in the exhaust gas are decomposed by a catalytic reaction. In this method, hot air generated by a hot air generator is used to heat the exhaust gas.

[0003]

In order to decompose harmful substances in exhaust gas by catalytic reaction, it is necessary to heat the exhaust gas to a predetermined temperature. In addition, it is necessary to avoid mixing of a reducing gas such as CO into the hot air used for heating the exhaust gas. This is because a reducing gas such as CO has a significant adverse effect on the efficiency of catalytic decomposition of harmful substances in exhaust gas. It is said that the CO concentration in the hot air at the outlet of the hot air generator needs to be 30 ppm (oxygen concentration 12% conversion value) or less. However, the flow rate of the exhaust gas generally has large fluctuations, and therefore, the ventilation resistance of the catalyst tower also has large fluctuations. As such, exhaust gas with large fluctuations
It is necessary to heat to a fixed predetermined temperature and generate hot air with a small amount of CO mixed therein.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hot air generator capable of generating hot air satisfying the above-mentioned conditions and a control method therefor. It is. The hot air generator of the present invention is a device having a fuel supply unit, a fuel supply amount control unit, a combustion air supply unit, a combustion air supply amount control unit, a combustion chamber, and a hot air outlet. The combustion chamber has a primary combustion chamber and a secondary combustion chamber connected to the primary combustion chamber. The means for supplying combustion air includes a combustion air duct so that the combustion air can be divided into primary combustion air and secondary combustion air and supplied to the primary combustion chamber and the secondary combustion chamber, respectively. Is branched. In addition, the present apparatus further includes: combustion air before being divided into primary combustion air and secondary combustion air;
It has a differential pressure detecting means for detecting a differential pressure with hot air at the hot air outlet. The above-described hot-air generator of the present invention is arranged so that the primary combustion air detected by the differential pressure detecting means
The supply amount of combustion air is controlled so that the pressure difference between the combustion air before being divided into the next combustion air and the hot air at the hot air outlet is constant, and the combustion air is divided into primary and secondary air. And burn it to generate hot air.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a hot air generator 1 according to the present invention.
An example is schematically shown, and the contents will be described with reference to the drawings. FIG.
In the figure, a dotted frame 26 indicates a fuel supply means composed of a pressure gauge (PG) 27, followed by an automatic opening / closing valve (S) 28, and a fuel regulating valve 3. The amount of fuel supplied to the combustion chamber from the fuel supply means is controlled by a fuel supply control means such as a control motor. In FIG. 1, a dotted frame 29 indicates a combustion air supply means including a combustion blower and a differential pressure adjusting damper 5, and the combustion air is supplied from the combustion blower 2 to the differential pressure adjusting damper 5, The air is sent out to the combustion chamber via the air damper 7. The delivery amount of the combustion air can be controlled by the rotation speed of the motor of the combustion blower 2, or can be adjusted by the differential pressure adjusting damper 5.

Reference numeral 1 denotes a burner, and the fuel is the burner 1
And the primary combustion air is mixed into the primary combustion chamber 1
It is burned at 1 and becomes primary combustion gas. The combustion air sent from the combustion blower 2 is supplied to a combustion air adjusting damper 7.
After passing through, a part of it is
The secondary combustion air duct 9 branched from the combustion air duct 6 is guided to the secondary combustion air supply chamber 12, passes through the secondary combustion air blowing nozzle 13, etc., and becomes secondary combustion air. , And is led to the secondary combustion chamber 15. The secondary combustion air supply chamber 12 is provided on the outer periphery of the primary combustion chamber 11 so that the secondary combustion air is preheated by the heat of the primary combustion chamber. Further, the secondary combustion air blowing nozzle 13 is provided on the outer periphery of the outlet of the primary combustion chamber 11 so that the secondary combustion air is supplied from the outer periphery of the combustion flame in the primary combustion chamber 11. A plurality are provided at an angle to the direction.

Therefore, the secondary combustion air is supplied to the primary combustion chamber 1.
After being sufficiently preheated in the secondary combustion air supply chamber 12 provided on the outer periphery of the primary combustion chamber 1, the secondary combustion air is supplied through the secondary combustion air blowing nozzles 13 provided on the outer periphery of the outlet of the primary combustion chamber 11. And supplied from outside the primary combustion flame. Therefore, in the hot air generator of the present invention, the primary combustion gas is not rapidly cooled by the secondary combustion air, and the self-circulation of the combustion gas is caused by the plurality of air blowing nozzles 13. The fuel remaining in the secondary combustion and the secondary combustion air exhibit two functions of being uniformly mixed and stirred. By these actions, the hot-air generator of the present invention has a high flame holding property and a large burner turndown ratio, so that it is easy to increase or decrease the amount of hot-air generated.

In the combustion apparatus, if the amount of combustion air is insufficient, CO is generated due to incomplete combustion due to lack of oxygen, and if the amount of combustion air is excessive, the combustion temperature is reduced. CO is generated due to incomplete combustion. For complete combustion, the combustion temperature must be maintained at a high temperature of 1200 ° C. or higher, and therefore, the excess air ratio in the secondary combustion chamber must be 30% or less. The hot-air generator of the present invention can be controlled so as to constantly satisfy the above-described condition of complete combustion. That is, even if the flow rate of the exhaust gas to be heated fluctuates, the amount of combustion air is controlled to an appropriate amount to complete combustion, and the hot air is controlled to suppress generation of CO due to excess or deficiency of the combustion air. Can be supplied to the hot air outlet. Actually, using the hot air generator of the present invention, hot air at a temperature of 500 ° C.
It was generated at a capacity of m ³ / H, and the CO in the hot air was investigated. CO was 5 ppm (converted value of oxygen concentration 12%).
It was below. As described above, the hot-air generator of the present invention has an effect that hot air can be obtained by completely burning in the secondary combustion chamber and suppressing generation of CO due to excess or deficiency of combustion air.

Means for maintaining an appropriate amount of combustion air irrespective of fluctuations in the flow rate of the exhaust gas include the pressure of the hot air at the hot air outlet and the pressure of the combustion air before being divided into primary combustion air and secondary combustion air. Means of making the differential pressure from the pressure constant can be recommended. Specifically, for example, the combustion air sent from the combustion blower 2 and a part of the combustion air in the stage 24 before being divided into the primary combustion air and the secondary combustion air And a part of the hot air from the hot air outlet 25, respectively, is guided to the differential pressure detecting unit 21 (for example, a diaphragm pressure detector) by using a pipe, and is sent from the combustion blower 2 so that the detection fluctuation is constant. This is a means of controlling the amount of combustion air sent out.

By the way, in order to decompose harmful substances in exhaust gas by catalytic reaction, it is necessary to heat the exhaust gas to a predetermined temperature or higher. However, the heat resistance of the catalyst is limited and the temperature is not too high. Also need to be controlled. Therefore, the temperature of the exhaust gas at the entrance 23 to the catalyst tower 18 is measured, and the amount of fuel supply, the amount of primary combustion air, and the amount of secondary combustion air are controlled according to this temperature.

In FIG. 1, reference numeral 17 denotes a temperature control air blower. The temperature control air blown out from the temperature control air blower 17 is provided on the outer circumference of an outlet of the secondary combustion chamber 15 by a temperature control air blower. It is supplied into the combustion gas from the air blowing port 16. The temperature of the hot air at the hot air outlet 22 is measured,
According to the temperature, the supply amount of the temperature adjusting air is controlled by the temperature adjusting air adjusting damper 30. The temperature control air serves to cool hot air when the temperature is too high. As a result, the hot air generator of the present invention sends hot air having a temperature not exceeding the heat resistant temperature of the catalyst to the catalyst tower 18. Can be.

[0012]

The supply amount of combustion air is controlled so that the pressure difference between the combustion air and the hot air at the hot air outlet is kept constant, and the combustion air is divided into primary and secondary combustion. By generating hot air, the exhaust gas can be heated to a predetermined temperature and hot air with a very small amount of CO can be generated, and by using this, harmful substances in the exhaust gas can be catalyzed. Could be effectively decomposed.

[Brief description of the drawings]

FIG. 1 shows an example of a hot air generator according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Burner 2 Combustion blower 3 Fuel adjustment valve 4 Control motor 5 Differential pressure adjustment damper 6 Combustion air duct 7 Combustion air adjustment damper 8 Secondary combustion air adjustment damper 9 Secondary combustion air duct 10 Burner tile 11 Primary Combustion chamber 12 Secondary combustion air supply chamber 13 Secondary combustion air injection nozzle 14 Combustion cylinder 15 Secondary combustion chamber 16 Temperature control air inlet 17 Temperature control air blower 18 Catalyst tower 19 Catalyst carrier 20 Exhaust gas 21 Differential pressure detecting section (for example, diaphragm pressure detector) 22 Hot air temperature measuring point (near hot air outlet) 23 Exhaust gas temperature measuring point (near catalyst tower inlet) 24 Combustion air extraction point for pressure measurement (for combustion) (Near the air damper) 25 Hot air outlet for pressure measurement (Near hot air outlet) 26 Fuel supply means 27 Pressure gauge 28 Automatic open / close valve 29 Combustion air supply means 30 Air regulation damper for temperature regulation

Claims (4)

[Claims] 1. A hot air generator comprising a fuel supply unit, a fuel supply amount control unit, a combustion air supply unit, a combustion air supply amount control unit, a combustion chamber, and a hot air outlet. The combustion chamber is composed of a primary combustion chamber and a secondary combustion chamber connected to the primary combustion chamber. The combustion air duct is branched so that it can be supplied to the combustion chamber and the secondary combustion chamber, and the supply amount of the combustion air before being divided into the primary combustion air and the secondary combustion air. Control means, and differential pressure detecting means for detecting a differential pressure between the hot air at the hot air outlet and the combustion air before being divided into primary combustion air and secondary combustion air. Hot air generator. 2. The primary combustion chamber is provided with an outlet connected to the secondary combustion chamber, and a plurality of secondary combustion air blowing nozzles are provided on an outer periphery of the outlet. The hot air generator according to claim 1. 3. A pressure difference between combustion air before being divided into primary combustion air and secondary combustion air, and hot air at a hot air outlet, using the hot air generator according to claim 1. Is detected by the differential pressure detecting means, and the supply of combustion air is controlled and burned to generate a hot air so as to make the pressure constant. 4. A hot air, wherein the hot air is generated by using the hot air generating device according to claim 1 to burn the combustion air separately into primary combustion air and secondary combustion air. How it occurs.