JP2001304502A - Method for preventing corrosion of boiler tube and structure of boiler tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure prevention of corrosion of a most easily corroded portion of a boiler tube, i.e., the portion right above the upper end of refractories. SOLUTION: In a boiler wall 12 wherein a number of boiler tubes 8 are vertically arranged with an interval therebetween, wherein the boiler tubes 8 are connected with each other through a connecting board 9, and wherein the lower inside of the boiler tubes 8 is lined with refractories 10, the boiler tubes 8 are prevented from being corroded by blowing a perge gas from between the boiler tubes 8 at right above the upper end of the refractories 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing corrosion of a boiler tube and a boiler tube structure,
The present invention relates to a boiler tube corrosion prevention method and a boiler tube structure that can reliably prevent corrosion of a boiler tube immediately above an upper end of a refractory that is most likely to be corroded.

[0002]

2. Description of the Related Art For example, in a waste incinerator, waste heat is effectively used by passing high-temperature exhaust gas through a boiler. Hereinafter, the boiler will be briefly described with reference to the drawings.

FIG. 4 is a longitudinal sectional view showing a refuse incinerator provided with a boiler, FIG. 5 is a partial sectional view taken along line AA of FIG.
FIG. 6 is a partial cross-sectional view taken along the line BB of FIG. 4, and FIG.
FIG. 4 is an enlarged partial cross-sectional view taken along a line A.

In FIG. 4 to FIG. 7, reference numeral 1 denotes a refuse incinerator main body, 3 denotes a boiler provided on the exhaust gas discharge side of the refuse incinerator main body 1, and 2 reburns unburned components in the combustion exhaust gas. Combustion chamber in the boiler 3 for use. Boiler 3
Is provided with a boiler wall 4 and has a structure in which high-temperature exhaust gas passes through a space surrounded by the boiler wall 4.

[0005] The boiler wall 4 is lined with a plurality of boiler tubes 5 provided vertically at intervals, a metal connecting plate 6 for connecting the boiler tubes 5 to each other, and a lower inside of the boiler 3. And a castable refractory 7. The portion where the refractory 7 is lined is referred to as a lower radiation heat transfer portion 3A, and the portion above the refractory 7 is referred to as an upper radiation heat transfer portion 3B.

In the boiler 3 configured as described above, when the high-temperature exhaust gas from the secondary combustion chamber 2 passes through the space surrounded by the boiler wall 4, the high-temperature exhaust gas and the boiler water circulating in the boiler tube 5 are removed. Exchange heat. As a result, the boiler water becomes heated steam and is sent to the next process such as a turbine for power generation. Boiler water is condensed and recycled.

[0007]

In the above-described boiler, the boiler tube 5A immediately above the upper end of the refractory 7 was most easily corroded. This is because the exhaust gas temperature is maintained at a high temperature of 700 to 950 ° C. in the lower radiant heat transfer section 3A, and as shown in FIG. This is considered to be caused by reduction corrosion, molten salt corrosion, high-temperature corrosion, or corrosion caused by dust in exhaust gas adhering to the boiler tube 5 immediately above the upper end of the refractory 7.

Conventionally, in order to solve the above problem, FIG.
As shown in the figure, a method has been taken in which the upper end of the refractory 7 is formed obliquely to reduce entrainment of high-temperature exhaust gas.
There was not enough solution.

Therefore, there is a strong demand for a method for preventing corrosion of the boiler tube 5A just above the upper end of the refractory 7 due to entrainment of high-temperature exhaust gas and development of a boiler tube structure. However, such a method and structure have not yet been proposed. There is no present.

Accordingly, an object of the present invention is to provide a boiler tube corrosion prevention method and a boiler tube structure that can reliably prevent corrosion of a boiler tube immediately above an upper end of a refractory which is most likely to be corroded. It is in.

[0011]

According to the first aspect of the present invention,
A number of boiler tubes are provided vertically at intervals, the boiler tubes are connected to each other by a connecting plate, and the lower inside of the boiler tubes is a boiler tube in a boiler wall on which a refractory is lined. In the method for preventing corrosion, a purge gas is blown into the boiler from between the boiler tubes immediately above the upper end of the refractory, thereby preventing corrosion of the boiler tube immediately above the upper end of the refractory.

The invention according to claim 2 is characterized in that the purge gas is blown toward the boiler tube immediately above the upper end of the refractory.

According to a third aspect of the present invention, a large number of boiler tubes are provided vertically at an interval, and the boiler tubes are connected to each other by a connecting plate. The boiler tube structure in the lined boiler wall is characterized in that a purge gas blowing nozzle for blowing a purge gas into the boiler is provided on the connecting plate immediately above the upper end of the refractory.

The invention according to claim 4 is characterized in that the purge gas blowing nozzle is arranged toward the boiler tube immediately above the upper end of the refractory.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for preventing corrosion of a boiler tube according to the present invention will be described with reference to the drawings.

FIG. 1 is a partial sectional view showing a boiler tube structure of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. 3 is a partial sectional view showing another boiler tube structure of the present invention. It is.

In FIGS. 1 to 3, reference numeral 8 denotes a number of boiler tubes which are vertically provided at intervals, and reference numeral 9 denotes a boiler tube.
A metal connecting plate 10 for connecting the boiler tubes 8 to each other is a castable refractory lined inside a lower portion of the boiler tube 8, and 11 is a refractory 10.
Is a purge gas blowing nozzle provided on each connecting plate 9 immediately above the upper end of the nozzle.

A boiler wall 12 is constituted by the boiler tube 8, the connecting plate 9 and the refractory 10. From each nozzle 11, a purge gas such as air is blown into the boiler from a header tube (not shown).

In this manner, when the purge gas is blown into the boiler from each nozzle 11, entrainment of high-temperature exhaust gas generated at the upper end of the refractory 7 is suppressed, and
Local gas property stabilization and temperature suppression can be performed.
Accordingly, there is no reduction corrosion or molten salt corrosion due to entrainment of the high-temperature exhaust gas, or corrosion due to dust in the exhaust gas adhering to the boiler tube 8A immediately above the upper end of the refractory 10.

As shown in FIG. 3, by directing the tip of the nozzle 11 toward the boiler tube 8A just above the upper end of the refractory 10, the surface of the boiler tube 8A can be directly purged, so that the effect of preventing corrosion of the boiler tube 8A is further improved. improves. In order to diffuse the purge gas and make it easier for the purge gas to flow toward the boiler tube 8A, the nozzle 1
1 may be formed by widening the tip opening. The injection pressure of the purge gas is appropriately adjusted in accordance with the flow rate of the exhaust gas rising in the boiler so that the effect of suppressing the entrainment of the high-temperature exhaust gas occurs. As purge gas, besides air,
An inert gas such as nitrogen gas may be used.

[0021]

As described above, according to the present invention, by injecting the purge gas into the boiler from between the boiler tubes immediately above the upper end of the refractory, entrainment of high-temperature exhaust gas generated just above the upper end of the refractory is suppressed. Therefore, there is provided a useful effect that corrosion of the boiler tube immediately above the upper end of the refractory can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing a boiler tube structure of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a partial cross-sectional view showing another boiler tube structure of the present invention.

FIG. 4 is a longitudinal sectional view showing a refuse incinerator provided with a boiler.

FIG. 5 is a partial sectional view taken along line AA of FIG. 4;

FIG. 6 is a partial sectional view taken along line BB of FIG. 4;

FIG. 7 is an enlarged partial sectional view taken along line AA of FIG. 6;

[Explanation of symbols]

 1: Waste incinerator body 2: Secondary combustion chamber 3: Boiler 3A: Lower radiant heat transfer section 3B: Upper contact heat transfer section 4: Boiler wall 5: Boiler tube 5A: Boiler tube immediately above the refractory upper end 6: Connecting plate 7: Refractory 8: Boiler tube 9: Connecting plate 10: Refractory 11: Nozzle 12: Boiler wall

Claims (4)

[Claims] 1. A boiler wall comprising a plurality of boiler tubes vertically provided with a space therebetween, wherein the boiler tubes are connected to each other by a connecting plate, and a lower inner side of the boiler tubes is lined with a refractory material. In the method for preventing corrosion of the boiler tube, the purge gas is blown into the boiler from between the boiler tubes immediately above the upper end of the refractory, thereby preventing corrosion of the boiler tube immediately above the upper end of the refractory. To prevent boiler tube corrosion. 2. The method for preventing corrosion of a boiler tube according to claim 1, wherein the purge gas is blown toward the boiler tube immediately above an upper end of the refractory. 3. A plurality of boiler tubes are provided vertically with an interval therebetween, and the boiler tubes are connected to each other by a connection plate, and a boiler wall lined with a refractory is provided on a lower inner side of the boiler tubes. The boiler tube structure according to any one of claims 1 to 3, wherein a purge gas blowing nozzle for blowing a purge gas into the boiler is provided on the connecting plate immediately above an upper end of the refractory. 4. The boiler tube structure according to claim 3, wherein the purge gas blowing nozzle is disposed toward the boiler tube immediately above an upper end of the refractory.