JPH07167426A - Air preheater outlet exhaust gas temperature controller in boiler - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to control the temperature of exhaust gas from an air preheater within an optimum temperature range with a simple configuration without requiring a steam heating device for combustion air. [Configuration] An air preheater 10 having an exhaust gas passage 20 through which an exhaust gas 23 from a boiler 1 passes, a primary air preheating passage 16, and a secondary air preheating passage 17 having a heat exchange cross section larger than that of the primary air preheating passage 16, and a primary air preheating A forced draft fan 6 for supplying air to the passage 16 and the secondary air preheating passage 17,
A primary air supply passage 8 that connects the primary air preheating passage 16 to the pulverized coal machine 4 and a secondary air supply passage 9 that connects the secondary air preheating passage 17 to the boiler 1 Of the pulverized coal bypass passage 33 for connecting the pulverized coal burner 1 to a location other than the pulverized coal burner, an exhaust gas temperature control damper 35 provided in the pulverized coal bypass passage 33, and a temperature detector provided at the exhaust gas outlet of the air preheater 10. 36 and an exhaust gas temperature controller 40 that controls the opening of the exhaust gas temperature control damper 35 based on the temperature 37 detected by the temperature detector 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is designed so that the exhaust gas temperature of an outlet of an air preheater for preheating combustion primary air and secondary air supplied to a pulverized coal burning boiler with a boiler exhaust gas falls within a predetermined temperature range. , An air preheater outlet exhaust gas temperature control device.

[0002]

2. Description of the Related Art In a coal-fired boiler, primary air and secondary air used for combustion are preheated in an air preheater using exhaust gas from the boiler, and the primary air preheated in the air preheater is a pulverized coal machine. Through the pulverized coal burner and the pulverized coal burner to the boiler, and the secondary air is directly supplied to the boiler.

FIG. 2 shows an example of a conventional coal-fired boiler. A coal-fired boiler 1 used for power generation, industrial use, etc. has a pulverized coal burner 2 attached thereto. 2 is connected to the pulverized coal machine 4 by the pulverized coal supply pipe 3.

Combustion air of the boiler 1 is sucked into the forced draft fan 6 from the air suction pipe 5 and heated by the steam heating device 7. On the discharge side of the steam heating device 7, the primary air supply passage is provided. 8 and the secondary air supply passage 9 are introduced into the air preheater 10 and are separately preheated by the high temperature exhaust gas 23 from the exhaust gas duct 11 connected to the boiler 1, and then the primary air 12 is supplied with the primary air. The secondary air 13 is guided to the pulverized coal machine 4 through the passage 8, and the secondary air 13 is guided to the pulverized coal burner 2 of the boiler 1 and the OAP (over air port) not shown by the secondary air supply passage 9.

As the air preheater 10, for example, FIG.
And, a rotary air preheater such as a Rotemure heat exchanger as shown in FIG. 4 is generally used.

The rotoremure type air preheater 10 is formed on the upper side and the lower side of the disc-shaped heat exchange element 14 so as to have a butterfly shape within a required angle range around the center of the heat exchange element 14. In addition, the partition wall 15 allows air to flow through the inner primary air preheating passage 16 and the outer secondary air preheating passage 17
The upper and lower air hoods 18 and 19 are provided so as to correspond to each other, and the air hoods 18 and 19 are configured to be rotationally driven with respect to the heat exchange element 14.

Further, fixed upper and lower exhaust gas hoods that surround the air hoods 18 and 19 and form an exhaust gas passage 20 for supplying the high temperature exhaust gas 23 to the remaining angle range excluding the required angle range. 21 and 22 are provided. In FIG. 3, the primary air 12 and the secondary air 13 are caused to flow from the lower side of the air preheater 10 to the upper side thereof, and the exhaust gas 23
Is flowing from the upper side to the lower side.

The passage cross section between the primary air preheating passage 16 and the secondary air preheating passage 17, that is, the size of the heat exchange area, of the air preheater 10 is determined according to the required amount of the primary air 12 and the secondary air 13. In general, the secondary air preheating passage 17 has a larger passage cross section than the primary air preheating passage 16 as in about 3: 7.

A pulverized coal machine supply air amount control damper 24 is provided at a place where the primary air supply passage 8 is connected to the pulverized coal machine 4, and is detected by an air amount detector 25 attached to the pulverized coal supply pipe 3. There is provided a controller 28 for issuing a command signal to the controller 27 of the pulverized coal machine supply air amount control damper 24 so that the flow rate on the outlet side of the pulverized coal machine 4 becomes the set flow rate 26.

Exhaust gas 23 generated in the boiler 1 is guided to the exhaust gas passage 20 of the air preheater 10 through the exhaust gas duct 11, and the exhaust gas duct 11 causes a dust collector (not shown),
It is designed to be led to a desulfurizer.

The exhaust gas duct 11 for guiding the exhaust gas 23 generated in the boiler 1 to the exhaust gas passage 20 of the air preheater 10 is provided with an oxygen amount detector 29 for detecting the residual oxygen amount in the exhaust gas 23 emitted from the boiler 1. A controller 32 for issuing a command signal to the controller 31 of the forced draft fan 6 is provided so that the residual oxygen amount in the exhaust gas 23 discharged from the boiler 1 becomes the residual oxygen amount set value 30.

Exhaust gas 23 generated by combustion of the boiler 1
Is preheated to the primary air 12 and the secondary air 13 while passing through the exhaust gas passage 20 of the air preheater 10 to lower the temperature, and then is guided to the dust collector and the desulfurizer by the exhaust gas duct 11. It is discharged to the outside.

At this time, the exhaust gas passage 20 of the air preheater 10
Boiler efficiency (combustion efficiency) is better when the exhaust gas 23 passing through passes the heat as much as possible to the primary air 12 and the secondary air 13 and the temperature of the exhaust gas 23 becomes low and is discharged downstream of the exhaust gas duct 11.
However, if the temperature of the exhaust gas 23 emitted from the air preheater 10 is too low, a product based on sulfurous acid gas or sulfuric acid is generated, which lowers the efficiency of the dust collector or desulfurizer and reduces the exhaust gas. This causes a problem such as corrosion of the duct 11.

Therefore, it is desired that the temperature of the exhaust gas at the outlet of the air preheater 10 be maintained in the range of 130 to 140 ° C.

[0015]

In order to adjust the temperature of the exhaust gas at the outlet of the air preheater 10 to 130 to 140 ° C., conventionally, the air before entering the air preheater 10 is preheated by the steam heating device 7, With this, the temperature of the exhaust gas 23 is controlled.

However, in the above-mentioned conventional apparatus, the control range of the exhaust gas temperature is narrow and it is not possible to meet the operational requirements. Further, it is necessary to provide the steam heating device 7, and a large amount of steam is required for heating the air. There was a drawback that it was consumed.

The present invention eliminates such conventional drawbacks,
It is an object of the present invention to provide an air preheater outlet exhaust gas temperature control device for a boiler that does not require a steam heating device and can control the exhaust gas temperature from the air preheater to an optimum temperature range with a simple device. is there.

[0018]

The present invention is directed to a boiler having a pulverized coal burner, a pulverized coal machine connected to the pulverized coal burner, an exhaust gas passage through which exhaust gas from the boiler passes, and an exhaust gas passing through the exhaust gas passage. Depending on the residual oxygen content in the exhaust gas, an air preheater having a secondary air preheating passage having a larger heat exchange cross section than the primary air preheating passage, which is preheated by the exhaust gas passing through the exhaust gas passage, A forced draft fan that supplies air to the primary air preheating passage and the secondary air preheating passage that are controlled, a primary air supply passage that connects the primary air preheating passage to the pulverized coal machine, and a secondary air preheating passage. An air preheater outlet exhaust gas temperature control device in a boiler, comprising: a secondary air supply passage connected to the boiler, wherein the primary air supply passage is connected to the pulverized coal bar of the boiler. Pulverized coal machine bypass passage connected to a place other than the above, an exhaust gas temperature control damper provided in the pulverized coal machine bypass passage, a temperature detector provided at the exhaust gas outlet of the air preheater, and detection of the temperature detector An exhaust gas temperature controller for controlling an opening of the exhaust gas temperature control damper based on a temperature, and an exhaust gas temperature control device for an air preheater outlet in a boiler.

[0019]

When the exhaust gas temperature at the outlet of the air preheater is high, the opening degree of the exhaust gas temperature control damper becomes small, the amount of primary air passing through the air preheater decreases, and the secondary air preheat passage having a large heat exchange cross section is passed. The amount of secondary air increases. Therefore, the amount of heat exchange from the exhaust gas in the air preheater increases and the exhaust gas temperature at the outlet of the air preheater decreases.

When the exhaust gas temperature at the outlet of the air preheater is low, the opening degree of the exhaust gas temperature control damper becomes large, the amount of primary air passing through the air preheater increases, and the secondary air preheat passage having a large heat exchange cross section is passed. Secondary air volume decreases. Therefore, the amount of heat exchange from the exhaust gas in the air preheater decreases and the exhaust gas temperature at the outlet of the air preheater rises.

[0021]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a system diagram of an embodiment of the present invention applied to the boiler of FIG. 2, in which the air sucked from the air suction pipe 5 to the forced draft fan 6 is equipped with a conventional steam heating device. Of course, the primary air preheating passage 1 is branched into the primary air supply passage 8 and the secondary air supply passage 9 and is divided into the primary air preheat passage 10 and the air preheater 10.
After being preheated by the exhaust gas 23 from the boiler 1 through the secondary air preheating passage 6 and the secondary air preheating passage 17, the primary air 12 passes through the primary air supply passage 8, the pulverized coal machine 4 and the pulverized coal supply pipe 3 to obtain fine powder of the boiler 1. Supply to the charcoal burner 2 and also the secondary air 1
3 is directly supplied to the pulverized coal burner 2 through the secondary air supply passage 9.

At the inlet of the pulverized coal machine 4, a pulverized coal machine supply air amount control damper 24 is provided, and the pulverized coal supply pipe 3
The controller 28 which issues a command signal to the controller 27 of the pulverized coal machine supply air amount control damper 24 so that the flow rate at the outlet of the pulverized coal machine 4 detected by the air amount detector 25 attached to the It is prepared. Further, an oxygen amount detector 29 for detecting the amount of residual oxygen in the exhaust gas 23 is provided at the outlet of the boiler 1 so that the amount of residual oxygen in the exhaust gas 23 emitted from the boiler 1 becomes the residual oxygen amount set value 30. Further, a controller 32 for issuing a command signal is provided to the controller 31 of the forced draft fan 6 so as to control the total amount of air supplied to the boiler 1.

In the above structure, the pulverized coal machine bypass passage 33 is branched into the primary air supply passage 8 between the air preheater 10 and the pulverized coal machine 4 and the pulverized coal bypass passage 3 is provided.
3 is the upper part of the boiler 1, the vicinity of the pulverized coal burner 2, and the boiler 1
An exhaust gas temperature control damper 35 is provided in the pulverized coal bypass passage 33 while being connected to an air inlet 34 provided at a required position such as the bottom of the pulverized coal.

Exhaust gas 23 of the air preheater 10 described above
An exhaust gas temperature controller 40 that outputs a command signal to the controller 39 of the exhaust gas temperature control damper 35 so that the temperature detector 36 is provided at the outlet of the exhaust gas temperature detector 36 and the detected temperature 37 of the temperature detector 36 becomes the set temperature 38. Set up.

The set temperature 38 of the exhaust gas 23 is set in the temperature range of 130 to 140 ° C. from the viewpoint of maintaining the efficiency of the dust collector and the desulfurization device and the corrosion prevention of the exhaust gas duct 11 and the like. The detected temperature 37 detected by is 13
When the temperature is higher than the range of 0 to 140 ° C, the exhaust gas temperature controller 40 controls the opening degree of the exhaust gas temperature control damper 35 to be small, and the detected temperature 37 is lower than the temperature range of 130 ° C to 140 ° C. In this case, the exhaust gas temperature controller 40 controls the exhaust gas temperature control damper 35 so as to increase the opening degree.

Next, the operation of the apparatus shown in FIG. 1 will be described.

The air sucked into the forced draft fan 6 from the air suction pipe 5 by operating the forced draft fan 6 is introduced into the primary air supply passage 8 and the secondary air supply passage 9 on the discharge side of the forced draft fan 6. Divide.

Primary air 1 flowing into the primary air supply passage 8
2 is an exhaust gas 23 passing through the exhaust gas passage 20 of the air preheater 10 when passing through the primary air preheating passage 16 of the air preheater 10.
After being preheated by the heat of 1, the air is divided into the air passing through the primary air supply passage 8 and the air flowing into the pulverized coal machine bypass passage 33 through the exhaust gas temperature control damper 35.

The primary air 12 of the primary air supply passage 8 enters the pulverized coal machine 4 through the pulverized coal machine supply air amount control damper 24, and together with the pulverized coal, the air amount detector 25, the pulverized coal supply pipe 3,
The air that enters the boiler 1 through the pulverized coal burner 2, burns the pulverized coal in the boiler 1 and flows into the pulverized coal machine bypass passage 33 is used as combustion air in the upper portion of the boiler 1, the vicinity of the pulverized coal burner, and the boiler. Air inlet 34 provided at the bottom of 1 etc.
Is supplied to the inside of the boiler 1. At this time, the installation position of the air blowing port 34 can be arbitrarily set, and the air may be supplied to one air blowing port 34, or may be simultaneously supplied to a plurality of air blowing ports 34. .

On the other hand, when the secondary air 13 flowing into the secondary air supply passage 9 passes through the secondary air preheating passage 17 of the air preheater 10, the heat of the exhaust gas 23 passing through the exhaust gas passage 20 of the air preheater 10 After being preheated by the pulverized coal, it is directly supplied from the pulverized coal burner 2 to the boiler 1 through the secondary air supply passage 9 and used for combustion of the pulverized coal.

Exhaust gas 23 generated by the combustion in the boiler 1 is introduced into the exhaust gas passage 20 of the air preheater 10 through the exhaust gas duct 11, and the primary air preheating passage 1 described above is introduced.
6. The air passing through the secondary air preheating passage 17 is preheated to lower the temperature, and then discharged to the outside through the exhaust gas duct 11 through a dust collector and a desulfurizer which are not shown.

The temperature of the exhaust gas 23 discharged from the air preheater 10 to the exhaust gas duct 11 is detected by the temperature detector 36, and the detected temperature 37 is 130 to 140 ° C. which is the set temperature 38 input to the exhaust gas temperature controller 40. If the temperature is higher than the temperature range, the exhaust gas temperature controller 40 controls the opening degree of the exhaust gas temperature control damper 35 to be small, and the detected temperature 37 is lower than the temperature range of 130 to 140 ° C. of the set temperature 38. In this case, the exhaust gas temperature controller 40 controls the exhaust gas temperature control damper 35 so as to increase the opening degree.

Air preheater 10 in the exhaust gas duct 11
When the exhaust gas temperature at the outlet of the exhaust gas is higher than the temperature range of 130 to 140 ° C. and the opening degree of the exhaust gas temperature control damper 35 becomes small, the flow rate of the air flowing through the pulverized coal bypass passage 33 decreases, The amount of primary air 12 passing through the primary air preheat passage 16 of the preheater 10 will be reduced. However, since the total amount of air flowing from the discharge side of the forced draft fan 6 into the primary air supply passage 8 and the secondary air supply passage 9 depends on the residual oxygen amount in the exhaust gas from the boiler 1, there is no change. When the amount of air passing through the primary air preheating passage 16 decreases, the amount of air passing through the secondary air preheating passage 17 increases.

By the way, in the primary air preheating passage 16 and the secondary air preheating passage 17, as shown in FIG. 4, the secondary air preheating passage 17 has a larger passage cross section than the primary air preheating passage 16, When the air flow rate is changed, the larger the passage cross section (heat exchange area), the larger the change in the amount of heat deprived (heat exchange efficiency). Therefore, the reduced amount of air passing through the primary air preheating passage 16 is used as the secondary air. When flowing into the preheating passage 17, the heat exchange rate of the air preheater 10 is rapidly increased, and the exhaust gas 2 at the outlet of the air preheater 10 in the exhaust gas duct 11 is discharged.
The temperature of 3 becomes low.

When the temperature of the exhaust gas 23 at the outlet of the air preheater 10 is lower than the temperature range of 130 to 140 ° C. and the opening degree of the exhaust gas temperature control damper 35 becomes large, the pulverized coal bypass passage 33 is opened. Since the flow rate of the flowing air increases, the amount of primary air passing through the primary air preheating passage 16 increases, and the amount of air passing through the secondary air preheating passage 17 decreases, the heat exchange rate of the air preheater 10 rapidly increases. As a result, the temperature of the exhaust gas 23 at the outlet of the air preheater 10 becomes higher.

In this way, by controlling the opening degree of the exhaust gas temperature control damper 35 by the temperature of the exhaust gas 23 at the outlet of the air preheater 10, the heat exchange rate of the air preheater 10 changes, and the exhaust gas at the outlet of the air preheater 10 changes. The temperature of 23 is kept in a temperature range of 130 to 140 ° C. to improve boiler efficiency (combustion efficiency) and prevent the generation of products and sulfuric acid based on sulfurous acid gas to corrode the exhaust gas duct 11 and a dust collector. It is possible to prevent adverse effects such as a decrease in the efficiency of the desulfurization device.

Further, since a part of the combustion air is supplied directly to the boiler 1 through the pulverized coal machine bypass passage 33 without passing through the pulverized coal burner 2, generation of nitrogen oxides and melting in the boiler 1 are performed. It is also possible to prevent adhesion of ash.

[0039]

INDUSTRIAL APPLICABILITY The present invention controls the exhaust gas temperature emitted from the air preheater to an optimum temperature range with a simple structure without providing a steam heating device for combustion air, thereby improving boiler efficiency and sulfurous acid. It is effective in reducing the generation of gas and sulfuric acid.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention.

FIG. 2 is a system diagram showing an example of an air preheater outlet exhaust gas temperature control device in a conventional boiler.

FIG. 3 is a cutaway front view of the rotary air preheater.

FIG. 4 is a plan view of FIG.

[Explanation of symbols]

 1 Boiler 2 Pulverized coal burner 4 Pulverized coal machine 6 Push-in fan 8 Primary air supply passage 9 Secondary air supply passage 10 Air preheater 16 Primary air preheating passage 17 Secondary air preheating passage 20 Exhaust gas passage 23 Exhaust gas 33 Pulverized coal bypass Passage 35 Exhaust gas temperature control damper 36 Temperature detector 37 Detected temperature 40 Exhaust gas temperature controller

Claims (1)

[Claims] 1. A boiler having a pulverized coal burner, a pulverized coal machine connected to the pulverized coal burner, an exhaust gas passage through which exhaust gas from the boiler passes, and a primary air preheating passage preheated by the exhaust gas passing through the exhaust gas passage. An air preheater having a secondary air preheating passage preheated by the exhaust gas passing through the exhaust gas passage and having a larger heat exchange cross section than the primary air preheating passage, and the primary air preheating passage controlled by the residual oxygen amount in the exhaust gas, and A forced draft fan that supplies air to a secondary air preheating passage, a primary air supply passage that connects the primary air preheating passage to the pulverized coal machine, and a secondary air supply that connects the secondary air preheating passage to the boiler. An air preheater outlet exhaust gas temperature control device in a boiler having a passage,
A pulverized coal machine bypass passage connecting the primary air supply passage to a location other than the pulverized coal burner of the boiler, an exhaust gas temperature control damper provided in the pulverized coal machine bypass passage, and an exhaust gas outlet of the air preheater were provided. An exhaust gas temperature control device for an air preheater outlet in a boiler, comprising: a temperature detector; and an exhaust gas temperature controller that controls an opening of the exhaust gas temperature control damper based on a temperature detected by the temperature detector.