JP2001082735A - Air preheater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam system of a steam air preheater outlet air duct for enabling the temperature difference of the element at the low-temperature end of a regenerative air preheater to be reduced. SOLUTION: Though air for combustion to be supplied to a boiler furnace 1 consists of the mixed air between the heat air having passed a regenerative air preheater 5 and the cold air having bypassed the regenerative air preheater 5 and passing through a duct 11, an air agitation means is installed in the air duct 4 at the outlet of a steam type air preheater so as to reduce the temperature difference within the air duct 4 at the outlet of the steam air preheater, whereby the temperature difference of the air for combustion can be reduced. This way, the suppression of the corrosion of an apparatus such as the low- temperature element, etc., of the regenerative air preheater becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air preheating apparatus for a combustion furnace such as a boiler, and more particularly to an air duct at an outlet of a steam air preheater of an air duct having a steam air preheater and a regenerative air preheater. TECHNICAL FIELD The present invention relates to an outlet duct structure of a steam-type air preheater for reducing a temperature difference between outlet air temperatures in a room.

[0002]

2. Description of the Related Art As shown in FIG. 4, fuel combustion air used in a boiler furnace 1 is supplied from an air duct 2 to a steam type air preheater 3.
And heat-exchanged, the air is supplied from the air duct 4 to the boiler furnace 1 through the regenerative air preheater 5. The boiler flue gas is supplied to the superheater 6 and the evaporator 7 in the boiler convection section.
After the heat exchange by the economizer 8, the denitrification treatment is performed by the denitration device 9, then the heat flows into the regenerative air preheater 5, heat exchanges with the boiler combustion air, and finally discharged from the chimney 10 to the atmosphere. Is done.

In order to make the combustion air supplied to the boiler furnace 1 suitable for combustion, cold air that branches off from an air duct 4 and passes through a bypass duct 11 that bypasses a regenerative air preheater 5; The hot air that has passed through the regenerative air preheater 5 is used after mixing. At this time, in order to adjust the temperature of the combustion air, the flow rate of the cold air is adjusted by opening and closing the flow rate adjustment damper 12 provided in the regenerative air preheater bypass duct 11 so that the combustion air temperature is set. Controlling.

FIG. 3 is an enlarged view of the air duct 2 and the air duct 4 provided before and after the steam type air preheater 3 with the steam type air preheater 3 interposed therebetween. Due to its structure, the steam-type air preheater 3 supplies steam from the upper end and discharges drain from the lower end.
In the air duct 4 after passing through the steam-type air preheater 3, as shown in FIG. 2, the upper end of the duct is in a high-temperature region, and the lower end is an air region having a temperature difference between the upper and lower ends of the low-temperature region (the horizontal axis in FIG. (Length in the width direction of the air duct 4).

[0005] The air flowing from the air duct 4 to the bypass duct 11 bypasses the regenerative air preheater 5 while maintaining the above-mentioned temperature difference, and is used as combustion air.
Since the combustion air introduced into the boiler furnace 1 remains at a temperature distribution having the above-mentioned temperature difference, the combustion air temperature at the place where the thermometer is installed and the combustion air temperature set are set. This is the cause of the deviation.

The steam-type air preheater 3 is provided for raising the air temperature at the inlet of the regenerative air preheater 5 to increase the low-temperature end metal temperature. The low-temperature end metal temperature of the regenerative air preheater 5 is set by the steam-type air preheater outlet air temperature and the regenerative air preheater outlet gas temperature. Preheater 3
When the air comes in contact with air in a low temperature range, the temperature rises only to a temperature lower than the expected element temperature, becomes lower than the acid dew point of sulfuric acid contained in the exhaust gas, and the regenerative air preheater 5 by condensation of sulfuric acid. It has been a problem that it may cause corrosion of devices constituting the device.

[0007]

In the above prior art, due to the structure of the steam-type air preheater 3, the inevitable nonuniformity of the outlet air temperature occurs. The difference in air temperature causes corrosion of the low-temperature element of the regenerative air preheater 5.

[0008] It is an object of the present invention to provide an air preheating apparatus for enabling a temperature difference between the low-temperature end element temperatures of a regenerative air preheater to be reduced.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to provide a steam type air preheater and a regenerative type air preheater which are arranged in order from the upstream in an air duct serving as a flow path for fuel combustion air in a combustion furnace. The air duct at the outlet of the steam type air preheater is provided to be branched to the air duct at the outlet of the steam type air preheater, and the bypass duct supplies the combustion air to the combustion furnace by bypassing the regeneration air preheater. The problem is solved by an air preheating device provided with the provided air stirring means.

[0010]

The non-uniform air temperature distribution at the outlet of the steam-type air preheater is reduced by providing air stirring means for mixing fluid in the air duct at the outlet of the steam-type air preheater. The temperature difference of the low-temperature end element temperature is also reduced, so that corrosion of the low-temperature element and the like of the regenerative air preheater can be suppressed.

[0011]

Embodiments of the present invention will be described with reference to the drawings. Combustion air supplied to the boiler furnace 1 is used by mixing cold air that has bypassed the regenerative air preheater 5 and hot air that has passed through the regenerative air preheater 5 in order to make the air suitable for combustion. are doing. At this time, the regeneration air preheater bypass duct 11 is used to adjust the combustion air temperature.
The flow rate of the cold air is adjusted by opening and closing the flow rate adjusting damper 12 provided in the apparatus, and control is performed so that the temperature of the combustion air is set.

The steam type air preheater 3 is for exchanging heat for boiler combustion air with steam supplied from the upper end as shown in FIG. The boiler combustion air that has exchanged heat with steam in the steam type air preheater 3 has a temperature difference of about 50 ° C. to 90 ° C. at the upper end and the lower end as shown in FIG. 2 and is supplied to the regenerative air preheater 5. .

When the regenerative air preheater is bypassed while having this temperature difference and merged as combustion air, the cold air has a temperature difference of about 50 ° C. to 90 ° C. at the upper end and the lower end. Although the subsequent combustion air temperature was not uniform, as shown in FIG. 1, the air duct 4 at the outlet of the steam-type air preheater was provided with air stirring means 13 composed of a punching plate, a propeller, an air foil, and the like. By installing and reducing the temperature difference in the air duct 4 at the outlet of the steam-type air preheater, the temperature difference in the combustion air temperature of the boiler furnace 1 can be reduced.

Further, the regenerative air preheater 5 sets a low temperature end element temperature to prevent corrosion of the low temperature element. However, if there is a temperature difference between the inlet air of the regenerative air preheater 5 and the regenerative air preheater 5, When the low-temperature element of the air preheater 5 comes into contact with air in the low-temperature region from the steam-type air preheater 3, the temperature rises only to a temperature lower than the expected element temperature, and is lower than the acid dew point of sulfuric acid contained in the gas. Thus, corrosion was a factor.

However, by providing the air agitating means 13 in the steam type air preheater outlet duct 4, the temperature difference between the inlet air temperature of the regenerative air preheater can be reduced and the corrosion of the low temperature element of the regenerative air preheater 5 can be suppressed. Becomes

[0016]

According to the present invention, by providing air stirring means at the outlet duct of the steam type air preheater, the temperature difference of the combustion air temperature can be reduced, and the temperature of the inlet air temperature of the regenerative air preheater can be reduced. By reducing the difference, low-temperature element corrosion of the regenerative air preheater can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic view of an air duct portion at an outlet of a steam-type air preheater of an air preheating apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an air temperature distribution of an outlet duct of a steam-type air preheater of an air preheating apparatus according to the related art.

FIG. 3 is a schematic view of a steam air preheater outlet duct of a prior art air preheating device.

FIG. 4 is a schematic diagram of a boiler plant.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 boiler furnace 2 air duct 3 steam type air preheater 4 air duct 5 regenerative air preheater 6 superheater 7 evaporator 8 economizer 9 denitrification device 10 chimney 11 regenerative air preheater bypass duct 12 flow control damper 13 air Stirring means

Claims (1)

[Claims] 1. A steam-type air preheater, a regenerative-type air preheater, and an air duct at an outlet of a steam-type air preheater, which are sequentially arranged from an upstream in an air duct serving as a flow path of fuel combustion air in a combustion furnace. A bypass duct which is provided in a branched manner and bypasses the regeneration air preheater and supplies combustion air to the combustion furnace;
An air preheating device comprising air stirring means provided in an air duct at an outlet of the steam type air preheater.