JPS6045764B2 - Method for preventing corrosion of boiler superheater tube/reheater tube short bend part - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing localized high-temperature corrosion occurring in superheater tubes and reheater tubes of a boiler.

Conventionally, in crude oil, heavy oil, and coal-fired boilers, the superheater tubes and reheater tubes are oxidized at an accelerated rate due to the adhesion of low-melting compounds consisting of elements such as V) Na and S contained in the fuel. It is known that a phenomenon called high-temperature corrosion due to molten salt occurs.

In order to prevent such high-temperature corrosion, methods such as injecting additives into the fuel and changing the fuel have been attempted, but they have not been successful due to combustion products and oil prices.

In addition, from the viewpoint of the material of the equipment, there is a method of spraying corrosion-resistant metal on the superheater tube and reheater tube to prevent corrosion, but the sprayed layer may peel off due to bending. To41! LIL-L゛J, wo-ζ:j21, ゝ,
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However, from the viewpoint of high-temperature strength, bending workability, weldability, etc., austenitic stainless steel pipes are generally used. On the other hand, in order to effectively transfer heat, the superheater/reheater heat exchanger tube coil 1 shown in Fig. 1 is used, but the short bend part of this coil has a small bending radius, so it may be short-circuited with the heat exchanger tube. The bend creates a space surrounded by a shape in which combustion ash tends to accumulate.

The details are shown in Fig. 2, but in a boiler that employs such a coil, the heat exchanger tube 3 made of austenitic stainless steel tube and the short bend part 2 are
It has been observed that combustion ash 4 accumulates in the space of the short bend section 2 due to corrosion, causing a breakout as shown in the figure.

This is because combustion ash 4, which is a combustion product, tends to accumulate in the short bend portion 2, and as a result, local corrosion occurs.

j An object of the present invention is to provide a method that eliminates the above-mentioned drawbacks of the prior art and prevents local high-temperature corrosion of heat exchanger tube coils of superheaters and reheaters.

In short, the present invention provides for
Corrosion in a shape that prevents the accumulation of combustion ash: A protective material made of a durable fireproof material is installed to distribute the combustion ash and allow it to fall, thereby preventing the occurrence of localized high-temperature corrosion. The present invention will be explained based on embodiments and with reference to the drawings.

FIG. 3 shows an embodiment of the present invention, in which a corrosion-resistant anchor bolt is provided with a protective material 6 made of a block-shaped fireproof material made of alumina in the short bend part 2. 5 and eliminates the space where combustion ash can easily accumulate. Figure 4 shows details of the protective material 6 made of block-shaped fireproof material.
The upper part of the protective material 6 has a saddle shape that rises up from the pipes on both sides, and is formed into a sharp peak shape that does not allow the accumulation of combustion ash, and the lower part has a shape that covers the short bend part 2. A groove 8 that fits the anchor bolt 5 is bored in the joining surface, and a bolt hole 9 is provided for fixing both, and the bolts and nuts 7 are fixedly connected.

Since the present invention has such a configuration, when combustion ash falls on the short bend portion 2 where high-temperature corrosion has conventionally occurred, the shape of the protective material 8 prevents it from accumulating and all of the ash falls on the short bend portion 2. Therefore, the occurrence of high-temperature corrosion due to combustion ash can be completely prevented.

Therefore, there is no need to change the shape of the coil, and there is no reduction in heat transfer efficiency. The present invention is economically advantageous compared to manufacturing the entire superheater tube or reheater tube with high-grade corrosion-resistant material, and furthermore, the shape of the heat exchanger tube coil of the superheater or reheater can be changed. There is no need to make any changes, and high-temperature corrosion of short bends can be prevented without reducing heat transfer efficiency, which is highly effective.

[Brief explanation of the drawing]

Figure 1 shows the heat exchanger tube coil 1 of the boiler superheater and reheater.
Figure 2 is a schematic diagram showing the accumulation of combustion ash and thinning in the short bend section of Figure 1.
FIG. 3 is a diagram in which the protective material 6 formed of a block-shaped fireproof material is attached, and FIG. 4 is a perspective view showing details of the protective material 6. 1...Superheater/reheater heat exchanger tube coil, 2...
... Short bend part, 3 ... Heat exchanger tube, 4.
... Combustion ash, 5 ... Anchor bolt, 6
...Protective material for alumina-based refractory materials, 7...
- Bolt nut, 8...groove, 9...bolt hole.

Claims (1)

[Claims] 1 Boiler superheater tubes and reheater tubes bent in a serpentine shape are arranged in a vertical position, and the inside of the short bend part of the boiler superheater tube and reheater tube is covered with a protective material, and the short bend part is A method for preventing corrosion of short bend parts of boiler superheater tubes and reheater tubes, which is characterized by distributing combustion ash and letting it fall.