JPH0449441Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a fluidized bed boiler in which heat transfer tubes are arranged within a fluidized combustion bed.

[Conventional technology]

As shown in FIG. 4, a fluidized bed boiler has heat transfer tubes 12 such as evaporator tubes, superheater tubes, or reheater tubes installed in a fluidized combustion bed 11. Limestone (CaCO ₃ ) is generally used as a material and has an intralayer desulfurization effect, so in recent years,
More and more cases are being used as coal-fired boilers.

[Problems with conventional technology]

However, inside the fluidized combustion bed 11, coal as a fuel and limestone particles as a fluidized material are mixed and are fluidized by the air supplied from the bottom of the furnace. As shown in FIG. 5, the floating particles of the tube 12 cause erosion on the lower side of the tube, resulting in a problem that the life of the tube is significantly shortened.

[Purpose of invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a fluidized bed boiler that can prevent the heat transfer tubes from being worn out while preventing the heat transfer effect of the heat transfer tubes from decreasing.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a fluidized bed boiler in which a heat exchanger tube is disposed within a fluidized combustion bed, in which 9% or more of Cr is added to the entire outer peripheral surface of the heat exchanger tube.
A plurality of circumferential fins with a circular outer periphery made of high Cr steel containing Cr are welded at appropriate intervals, and only the lower outer periphery of the circumferential fin has a curved surface that conforms to the outer periphery of the circumferential fin and has a semicircular cross section. A fluidized bed boiler is provided, characterized in that it is equipped with a wear-resistant protector made of a shaped plate.

[Effect]

The present invention covers the entire outer periphery of the heat transfer tube with multiple circumferential fins and attaches a protector with a semicircular cross section that covers only the lower outer periphery of the circumferential fins. It is possible to prevent a decrease in heat area and a decrease in heat transfer efficiency. In addition, by making the fins of high Cr steel containing 9% or more of Cr, a hard oxide protective film is formed on the surface of the fins in a metal temperature distribution of approximately 500 degrees Celsius or higher. Therefore, wear of the fins can be more effectively prevented.

〔Example〕

The present invention will be explained based on the embodiment shown in FIGS. 1 to 3.

In FIGS. 1 to 3, a heat transfer tube 2 such as an evaporator tube, a superheater tube, or a reheater tube, in which a plurality of fins 3 are welded to the entire outer peripheral surface, is arranged in a fluidized combustion bed 1. has been done. On the lower outer periphery of the fin 3,
A protector 4 made of high Cr steel containing 9% or more of Cr is arranged;
It is held by a band 5 made of high Cr steel containing Cr.

The protector 4 is preferably made of high Cr steel from the viewpoint of ease of installation, but ceramic may also be used.

Air bubbles rising from the bottom of the furnace form the fluidized combustion bed 1.
It collides with the protector 4 on the lower side of the heat exchanger tube 2 inside and decomposes into small air bubbles. At this time, since the behavior of the fluid material becomes active, without the protector 4,
Although the lower surface of the heat transfer tube 2 is worn out, the protector 4
Since the heat exchanger tube 2 is protected by this, wear of the heat exchanger tube 2 is prevented. However, the installation of the protector 4 reduces the effective heat transfer area of the heat transfer tube 2, resulting in a decrease in heat transfer efficiency. A decrease in heat transfer efficiency is prevented by welding fins 3 to the entire outer peripheral surface of the heat transfer tube 2 to prevent a substantial decrease in the effective heat transfer area. The fins 3 are made of high Cr steel containing 9% or more of Cr steel, and the thickness of the heat transfer tube 2 is adjusted such that the temperature distribution of most of the metal, including the tip of the fins 3, is approximately 500 degrees Celsius or higher. By designing the thickness, the thickness of the fins 3, and the height of the fins 3, it is possible to form a hard and stable oxide protective film on the surface of the fins 3. Wear on the upper side of the heating tube 2 is also prevented. That is, the degree of wear on the upper side of the heat exchanger tube 2 where the protector 4 is not provided is
Although it is lower than the lower side, it occurs due to the decomposition of regrown air bubbles due to the merging of remaining large air bubbles or small air bubbles.
The wear caused by this is resolved by the fins 3 decomposing the remaining large air bubbles and regrowth air bubbles, and the heat transfer tube 2
protect the upper surface of the At this time, as described above, since a hard oxide protective film is formed on the surface of the fins 3, the fins 3 are not worn. In the case of a circumferential fin heat exchanger tube with a protector, the movement of the fluid material above the heat exchanger tube 2 becomes extremely slow at the base of the fins, that is, near the surface of the heat exchanger tube, by appropriately selecting the height and pitch of the circumferential fins. This has been confirmed through model experiments, and since the metal temperature increases closer to the tips of the fins, a hard oxide protective film is formed, so that the heat exchanger tubes 2 and fins 3 do not wear out.

[Effect of idea]

As described above, the present invention has been explained using examples.
The present invention provides a fluidized bed boiler in which a heat exchanger tube is arranged in a fluidized combustion bed, in which the entire outer circumferential surface of the heat exchanger tube is made of a high chromium steel containing 9% or more of Cr and has a circular outer circumference. A plurality of circumferential fins are welded at appropriate intervals, and a wear-resistant protector made of a curved plate with a semicircular cross section that conforms to the outer circumference of the circumferential fin is provided only on the lower outer periphery of the circumferential fin. The present invention provides a fluidized bed boiler characterized by the following, whereby it is possible to prevent wear of the heat transfer tubes while preventing a decrease in heat transfer efficiency of the heat transfer tubes arranged in the fluidized combustion bed.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of an embodiment of the present invention, and FIG.
The figure is an enlarged view of the part in Figure 1, and Figure 3 is an enlarged view of the part in Figure 2.
4 is a front sectional view of a conventional fluidized bed boiler, and FIG. 5 is a view taken along the line V-V in FIG. 4.
It is an arrow view. 1, 11... fluidized combustion bed, 2, 12... heat transfer tube, 3... fin, 4... protector, 5... band.

Claims (1)

[Scope of utility model registration request] In a fluidized bed boiler in which a heat transfer device is arranged in a fluidized combustion bed, 9% is applied to the entire outer peripheral surface of the heat transfer tube.
A plurality of circumferential fins with a circular outer circumference made of high Cr steel containing the above Cr are welded at appropriate intervals, and only the lower outer circumference of the circumferential fin matches the outer circumference of the circumferential fin and has a half cross section. A fluidized bed boiler characterized by being equipped with a wear-resistant protector made of a circular curved plate.