JPH0253715B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing wear and tear on heat exchanger tubes placed in a fluidized bed.

Fluidized bed furnaces, which burn fuel (incineration materials) in a fluidized bed made of fluidized fluidized media such as sand, have high combustion efficiency and can burn even flame-retardant materials well, so they are used for incineration of various kinds of waste, etc. It is used in a wide range of fields. When the heat generated in this fluidized bed furnace is recovered as steam or hot water, heat transfer tubes are often placed within the fluidized bed because the heat transfer efficiency within the fluidized bed is much superior to that in the empty column.

Figure 1 shows an outline of a fluidized bed furnace. Fluidized air (combustion air) A that has flowed into the air chamber 2 of the fluidized bed furnace body 1 passes through a perforated plate 3 into a bed filled with a fluidized medium such as sand. A fluidized bed 4 is formed by fluidizing the fluidized fluid. The fuel (incineration material) supplied into the fluidized bed burns while being mixed with the fluidized medium and stirred, and the generated heat is transferred to the intrabed heat transfer tube 5 arranged in the bed.
The heat is recovered and recovered as steam or hot water. In this case, the heated fluidized medium is flowing violently in the fluidized bed 4, and the intrabed heat exchanger tubes 5 are placed under extremely severe conditions. The intensity of the movement of the fluidized medium is approximately proportional to the air passage speed until a situation occurs in which the amount of fluidized air supplied is so large that only air is blown through the bed. The air passing speed varies depending on the properties of the supplied fuel, the true specific gravity of the fluidizing medium, etc., but the average speed within the layer is 2.4 m/
sec. degree is common.

It was confirmed that when a heat transfer tube is placed in a fluidized bed in the above state, the bend portion of the heat transfer tube and the portion located in the upper layer of the fluidized bed are worn out due to friction by the fluidized medium. First, regarding the wear of the bend portion, the passing air velocity near the bend portion is, for example, about 3.4 m/sec, which is higher than other portions, and therefore the movement of the fluid medium is also intense, which causes wear in a short period of time. This is due to the fact that the bend part of the bed heat exchanger tube, which is placed as a stationary object in the fluidized bed, is located opposite the side wall of the fluidized bed furnace and faces a passage with no resistance, so the air passing rate is low near the pipe wall at the bend part. It is thought that this is because the friction speed of the fluid medium becomes faster, and therefore the friction speed of the fluid medium also becomes faster. In addition, in the upper part of the fluidized bed, especially when the fuel supply method is top-filling, the supplied fluidized air expands due to heating compared to the lower part.
Due to the addition of combustion gas, the moving speed of the medium particles increases, and the upper part of the heat transfer tube is severely worn not only at the bend part but also the entire heat transfer tube. , the area around the coal feeding nozzle will be severely worn. When this is shown in FIG. 1, bend portions 5a, 5b, 5c, 5
d, 5e, 5f and 5 located in the upper part of the fluidized bed.
g and 5h have particularly severe wear. If the fluidized bed furnace continues to operate in such a state, there is a risk that the internal fluid will leak into the fluidized bed and cause a major accident.

An object of the present invention is to solve the above-mentioned problems and provide a method for preventing damage to an interlayer heat exchanger tube.

In short, this invention provides a method for preventing wear of a heat exchanger tube arranged in a fluidized bed, in which the bend portion of the heat exchanger tube and at least the outer layer of the uppermost portion of the heat exchanger tube are formed of a wear-resistant material. This is a method for preventing wear of heat exchanger tubes in a fluidized bed.

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

Severely worn parts 5a to 5h of the interlayer heat exchanger tubes
As mentioned above, these are the parts where the speed of the rubbing fluidized medium is higher than the average passing speed of the fluidized air (including combustion gas) passing through the fluidized bed. This part is a part where the speed of the abrasive fluidized medium is 30% or more higher than the estimated speed of fluidized air passing through the perforated plate 3 in the fluidized bed furnace, and this part is particularly abraded. I understand.

FIG. 2 shows the state of formation of the wear-resistant material on the intrabed heat exchanger tubes 5 disposed in the fluidized bed furnace 1. As shown in FIG. Code 6 in the diagram
a, 6b, 6c, 6d, 6e, 6f are bend parts 5
Wear-resistant material layers were formed on a, 5b, 5c, 5d, 5e, and 5f, respectively, and wear-resistant material layers 6g and 6h were formed on heat exchanger tubes 5g and 5h, respectively, located in the upper layer of the fluidized bed.

FIG. 3 shows an example of a method of forming a wear-resistant material layer on the bend portion 5b of FIG. 2. Reference numerals 7a and 7b in the figure are wear-resistant material layer forming members made of wear-resistant material formed so as to be in close contact with the outer wall of the bend portion 5b. The bend portion 5b is completely covered and the joint portion is fixed by welding. FIG. 4 is a cross-sectional view of a heat exchanger tube in which a wear-resistant material layer is formed by the method shown in FIG. 3, and numerals 8 and 8 indicate welded portions. If the wear-resistant material layer is formed by this method, the wear-resistant material layer can be easily formed even in the currently used fluidized bed furnace by removing the fluidized medium in the furnace. As the wear-resistant material, for example, a stainless steel material of 25% Cr and 12% Ni is suitable.

Next, instead of forming the wear-resistant material into a predetermined shape as shown in FIG. 3, the wear-resistant material layer may be formed by thermal spraying or welding the wear-resistant material onto a predetermined portion.

By the above method, a wear-resistant material layer is formed on the surface of the heat exchanger tube at the bend portion of the heat exchanger tube and the upper layer of the fluidized bed, which are subject to severe wear.

By carrying out this invention, it is possible to significantly reduce the wear of heat exchanger tubes placed in a fluidized bed, thereby extending the life of the heat exchanger tubes.
There is no risk of accidents due to leakage of internal fluid.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional fluidized bed furnace, Fig. 2 is a cross-sectional view of a fluidized bed furnace having an intrabed heat exchanger tube in which the wear-resistant method according to the present invention is implemented, and Fig. 3 is a method for forming a wear-resistant material layer. FIG. 4 is a perspective view of the wear-resistant material layer forming member, and FIG. 4 is a cross-sectional view taken along the line AA in FIG. 3 with the wear-resistant material layer formed. 1...Fluidized bed furnace main body, 3...Perforated plate, 4...Fluidized bed, 5a, 5b, 5c, 5d, 5e, 5f...
Bend part, 5g, 5h...Fluidized bed upper heat exchanger tube,
6a, 6b, 6c, 6d, 6e, 6f, 6g, 6
h...Wear-resistant material layer, 7a, 7b... Wear-resistant material layer forming member.

Claims (1)

[Claims] 1. A method for preventing wear of a heat exchanger tube arranged in a fluidized bed, characterized in that the bend portion of the heat exchanger tube and the outer layer of at least the uppermost portion of the heat exchanger tube are formed of a wear-resistant material. A method for preventing wear of heat transfer tubes in a fluidized bed.