JPH0711326Y2 - Heat transfer tube damage prevention device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a damage prevention device for a heat transfer pipe group, and more particularly to a heat transfer pipe damage prevention device for preventing damage to the heat transfer pipe due to dust contained in combustion gas.

[Conventional technology]

In a device that burns solid fuel such as coal to generate combustion gas and installs a heat transfer tube group in this combustion gas flow to recover the heat of the combustion gas, the unburned fuel contained in the combustion gas It is known that the heat transfer tube surface is abraded by dust such as dust and ash.

In FIG. 5, combustion gas generated by a combustion device (not shown) on the left side of the drawing flows in the direction of arrow A, and then becomes a flow B further downward from the top of the drawing. FIG. 8 shows the installed state, and FIG. 8 shows VIII-VII of FIG.
FIG. 1 is a partial plan view taken along line I, showing a portion of the heat transfer tube 1 bent in the vertical direction in the vicinity of the furnace wall 2 as seen from above, showing that the combustion gas has a flow path 13 perpendicular to the paper surface. Although it flows in the direction (that is, from the top to the bottom), since the flow passage area is different between the vicinity of the furnace wall 2 and the portion distant from the furnace wall 2, the combustion gas flow velocity varies depending on the flow passage position.

FIG. 9 is a sectional view taken along the line IX-IX in FIG. 8, and the flow velocity line C conceptually shows the difference in the flow velocity of the combustion gas flowing through the heat transfer tube gap portion 14, and the closer it is to the furnace wall 2. , Shows that the flow velocity is high. The flow of the combustion gas passing through the tube row portion of the heat transfer tube is slowed down by the resistance to the flow of the tube row. However, since there is a gap with the furnace wall 2 near the bent portion of the heat transfer tube, the flow furnace area is large and the resistance is small. The combustion gas blocked by the heat transfer tube flows in, and the flow velocity increases. This local increase in flow rate and flow velocity is called drift.

The unburned fuel and ash contained in the combustion gas with a higher flow velocity than other parts collide with the surface of the heat transfer tube to cause wear, and this wear amount is the power of the combustion gas to the power of 2-3. Increases in proportion to. The uneven flow of the combustion gas is generally large at the bent portion of the heat transfer tube provided close to the furnace wall or the side wall of the combustion gas passage, and therefore wear due to dust contained in the combustion gas is also shown in FIG. In many cases, it occurs in the bent portion D of the heat transfer tube and the near portion E of the tube draw. In particular, after the combustion gas is generated in the combustion device, it is often introduced into the combustion gas flow path that houses the heat transfer tube group provided adjacent to the combustion device, and as shown in FIG. When the combustion gas flowing in the direction changes in the direction of the arrow B, the dust contained in the combustion gas tends to collect on the rear wall portion 14 side of the flow path due to its inertia. Wear is not necessarily limited to bends.

As shown in FIG. 10, a plurality of heat transfer tubes are horizontally arranged, and the heat transfer tubes are further arranged in a vertical direction to form a group, and a vertical combustion gas flow path is formed between each group. In particular, the combustion gas near the bent portion of the heat transfer tube becomes a flow that bends between the heat transfer tubes arranged vertically, and the surface of each heat transfer tube approximately 45 degrees above the horizontal is dust in the combustion gas. It is subject to abrasion and wear.

In order to prevent wear of the heat transfer tube as described above, FIG.
As shown in FIG. 7, a plate 10 is provided on the furnace wall (or combustion gas passage wall) 2 side, and a fin 11 is provided on the bent portion of the heat transfer tube 1.
There is known a method of attaching each of them by welding to prevent wear due to dust in the combustion gas at the bent portion of the heat transfer tube.

[Problems to be solved by the invention]

In the above-mentioned conventional technique, although wear due to uneven flow in the bent portion of the heat transfer tube is prevented, about wear prevention of the heat transfer tube group other than the bent portion due to the combustion gas having a high dust concentration from the rear wall side of the combustion gas passage. Was lacking in consideration.

An object of the present invention is to reduce the speed at which the dust contained in the combustion gas hits the surface of the heat transfer tube and reduce the wear of the surface of the heat transfer tube due to the dust.

[Means for solving problems]

The above-mentioned problem is that the baffle plate provided with a large number of holes is provided in the direction in which the flow of the combustion gas is obstructed, over the entire cross section of the flow path of the combustion gas corresponding to the heat transfer pipe portion targeted for wear prevention. This is achieved by a heat transfer tube damage prevention device arranged upstream of the combustion gas flow in the section.

[Action]

The hole provided in the baffle acts as an orifice for limiting the flow rate of the combustion gas, and the flow passage cross-sectional area increases after passing through this hole, so that the flow velocity of the combustion gas becomes lower than that before the passage of the baffle plate. When the combustion gas passes through the hole, the resistance received from the edge of the hole also acts to reduce the flow velocity of the combustion gas. When the flow velocity of the combustion gas decreases, the flow velocity of the dust floating in the combustion gas also decreases, and the speed at which the dust hits the surface of the heat transfer tube also decreases. Also, since the dust once collides with the baffle and the kinetic energy that the dust had acquired up to that point is absorbed by the baffle, the flow velocity of the dust obtained after passing through the baffle plate is:
The value does not become large immediately after passing the baffle. Further, since the baffle plate is arranged not on the heat transfer tube but on the upstream side of the heat transfer tube, the heat transfer area is not reduced.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2. 2 is a side view taken along line II-II of FIG. 1 in which a heat transfer tube 1 arranged in a combustion gas flow path formed by a water-cooled furnace wall 2 is supported by a support tube 3 arranged vertically. As shown in the figure, the heat transfer tube 1 is bent in the vertical direction to change its direction by 180 degrees, and other heat transfer tubes which are also bent at the corner of the bent portion are arranged in a group. . The L-shaped steel 8 is horizontally arranged in contact with the upper surface of the uppermost heat transfer tube 1A in this one group and the side surface of the support tube 3, and is fixed to the support tube 3 by a U bolt 9. . Furnace wall 2 at a position higher than the upper surface of the uppermost heat transfer tube 1A
The strip 16 is horizontally fixed to the strip 16, and the end of the baffle 6 having a large number of small holes 17 is fixed to the strip 16. The baffle plate 6 is bent downward along a fold line 18 parallel to the strip plate 16, and the end on the bent side is slidably mounted on the L-shaped steel 8. Baffle board is 3.2m thick
Made of m SUS304, small holes 17 diameter is 9mm, hole pitch is second
As shown in the figure, they are 13.5 mm and 11.7 mm. In the case of this example, the baffle plate has an aperture ratio of 40%.

When combustion gas containing dust hits the baffle plate 6 described above, small holes are generated.
The amount of combustion gas that passes through the baffle plate 6 is limited by 17 and, after passing through the baffle plate 6, the cross-sectional area of the combustion gas flow path increases again, so the flow velocity of the combustion gas decreases, and it floats in the combustion gas. The flow velocity of the dust is also reduced after passing through the baffle. Further, when the combustion gas hits the baffle plate 6, many dust particles in the combustion gas hit the baffle plate, and these dust particles lose their kinetic energy that they had until then and the velocity becomes zero. Since it is carried again by the combustion gas, the flow velocity decreases. Since the dust flow velocity has decreased as described above,
The amount of dust generated on the heat transfer tube was also reduced.

The combustion gas flow passage cross-sectional area S of the portion equipped with the heat transfer tube group is determined from the cross-sectional area of the portion of the combustion gas flow passage not equipped with the heat transfer tubes by setting all uppermost heat transfer tubes 1A in the combustion gas flow direction. Is the value obtained by subtracting the area K projected onto the plate, and the aperture ratio M of the baffle plate when the baffle plate is a perforated plate is Is desirable. The diameter of the holes is preferably smaller than the diameter of the heat transfer tube and larger than three times the average diameter of the dust.

Further, according to the present embodiment, the baffle plate 6 is slidably mounted on the L-shaped steel 8 even if there is a difference in the magnitude and direction of thermal expansion between the furnace wall 2 and the heat transfer tube 1. The baffle plate 6 easily slides on the L-shaped steel, and excessive stress does not occur.

Next, a reference example of the present invention will be described with reference to FIGS. In the embodiment, the baffle plate 6 is installed so as to be substantially perpendicular to the combustion gas flow path direction, but in the reference example, the baffle plate 6 is in contact with the side surface of the group of the heat transfer tubes 1 bent in the vertical direction, The baffle plate made of the wire netting 7 is fixed and attached to the heat transfer tube substantially parallel to the flow direction of the combustion gas. This baffle reduces the flow velocity of the combustion gas that passes through the baffle and bends toward the heat transfer tube, and the velocity of the dust contained in the combustion gas also declines. The surface wear is also reduced.
Further, in this embodiment, since the wire netting 7 is provided substantially parallel to the combustion gas passage, the draft of the combustion gas is not increased.

Further, in the above embodiment, the heat transfer tube can be mounted without welding, and it is not necessary to consider the heat effect of the heat transfer tube material due to welding. Although only one baffle plate is attached in the first embodiment, it is of course possible to arrange a plurality of baffle plates up and down if necessary, and instead of the perforated plate of the embodiment, a wire mesh is obstructed. It is also possible to use it for a plate.

[Effect of device]

According to the present invention, the speed at which the dust contained in the combustion gas hits the heat transfer tube can be reduced without reducing the heat transfer area of the heat transfer tube, and the wear of the surface of the heat transfer tube due to the dust is reduced. Has the effect of Further, by providing the baffle plate at one location in the combustion gas flow path, it is possible to reduce the wear of the plurality of heat transfer tubes on the downstream side due to the dust.

[Brief description of drawings]

1 is a plan view showing an embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a plan view showing a reference example of the present invention. FIG. 4 is a diagram of FIG.
FIG. 5 is a cross-sectional view taken along line IV-IV, FIG. 5 is a side view showing an arrangement of heat transfer tubes in a combustion gas passage, and FIG. 6 is a plan view showing an example of a conventional technique. FIG. 7 is VII- of FIG.
FIG. 8 is a sectional view taken along the line VII, and FIG. 8 is a VII of FIG.
FIG. 9 is a plan view taken along the line I-VIII, and FIG. 9 is a plan view of FIG.
FIG. 10 is a sectional view taken along line IX-IX, and FIG. 10 is a sectional view taken along line XX in FIG. 9. 1 ... Heat transfer tube, 6 ... Baffle plate, 17 ... Hole (small hole).

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. A baffle plate provided with a large number of holes, in the direction of obstructing the flow of combustion gas, over the entire cross section of the flow path of the combustion gas corresponding to the heat transfer tube portion to be subjected to wear prevention. Transfer pipe damage prevention device located upstream of the combustion gas flow in this section.