JPH0467081B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a waste heat recovery device that increases heat recovery efficiency by reducing the amount of exhaust gas bypassed in a flue.

For example, combined cycle power plants have recently been attracting attention as a part of high-efficiency power generation. This combined power generation plant first generates electricity using a gas turbine, and also recovers the heat in the exhaust gas discharged from the gas turbine using a waste heat recovery device (waste heat recovery boiler). Steam is used to operate a steam turbine to generate electricity. This combined power generation plant has high power generation efficiency because it generates electricity with a gas turbine and a steam turbine, and also has high load responsiveness, which is a characteristic of gas turbines, and is therefore able to adequately respond to sudden increases in electricity demand. There is also the advantage of excellent load followability.

Figures 1 to 4 show conventional waste heat recovery boilers. Figure 1 is a schematic system diagram of the waste heat recovery boiler, Figure 2 is a cross-sectional view of the heat insulation structure shown in Figure 1, and Figure 3 is a schematic diagram of the waste heat recovery boiler. FIG. 4 is an enlarged side sectional view of part A in FIG. 1, and FIG. 4 is a sectional view taken along the line B--B in FIG.

Exhaust gas G from a gas turbine (not shown in FIG. 1) flows from the upstream side (left side in FIG. 1) to the downstream side (right side in FIG. 1) in the flue as shown by the arrow. The inside is composed of a group of heat transfer tubes such as a superheater 1, a first-stage high-pressure evaporator 2, a second-stage high-pressure evaporator 4, a high-pressure economizer 7, a low-pressure evaporator 8, and a low-pressure economizer 11. A waste heat recovery boiler is installed.

The exhaust gas G passes through a superheater 1 and a first-stage high-pressure evaporator 2 to reach a denitrification device 3, where nitrogen oxides (NOx) in the exhaust gas are removed. Subsequently, the exhaust gas G is discharged through the second-stage high-pressure evaporator 4, the high-pressure economizer 7, the low-pressure evaporator 8, and the low-pressure economizer 11, and the waste heat in the exhaust gas is recovered. The high-pressure steam S ₁ and low-pressure steam S ₂ generated during this time are used as a power source for the steam turbine and as an internal heat source. Symbols 5 and 9 in the figure are high-pressure drums, respectively;
The low pressure drum is indicated by 6 and 10, downcomer pipes.

As described above, the waste heat recovery boiler is placed in the flue 100 through which exhaust gas from the gas turbine passes, but this flue 100 prevents heat from dissipating to the outside and improves the thermal efficiency of the waste heat recovery boiler. In order to increase the temperature, a heat-retaining structure as shown in Fig. 2 has been adopted. In FIG. 2, reference numerals 17a and 17b indicate side outer casings, 16 indicates a heat insulating material, and 20a and 20b indicate side inner casings. Note that as the exhaust gas G passes through each heat exchanger tube 12 (see FIGS. 3 and 4), the exhaust gas temperature decreases, so the thickness of the heat insulating material 16 is adjusted as shown in FIG. 2 in response to this exhaust gas temperature. The temperature of the insulation material 1 is changed as the temperature increases (upstream side).
The thickness of the heat insulating material 16 is increased to improve the heat insulation properties, and the thickness of the heat insulating material 16 is decreased in the low temperature section (downstream side).

Figure 3 shows an enlarged side sectional view of part A in Figure 1 of a conventional waste heat recovery boiler, and Figure 4 shows the 3rd section of a conventional waste heat recovery boiler.
A sectional view taken along line B-B in the figure is shown.

In addition, in FIG. 3 and FIG. 4, H ₂ and W ₂ indicate the heat transfer space in the flue 100, and H ₁ , H ₃ , W ₁ ,
W ₃ indicates non-heat transfer space.

The heat transfer tube group of the waste heat recovery boiler is shown in Figures 3 and 4.
As shown in the figure, heat exchanger tubes 12, upper and lower headers 1
9, 13, an upper connecting pipe 18, and a lower connecting pipe 21, the heat transfer tube 12 is supported at the bottom by a header support 14, and its outer periphery is surrounded by outer casings 17a, 17b as shown in FIG. ,24,
25, heat insulating material 16, internal casing 20a, 20
b, 22, 23 and is entirely supported on the header support beam 15 with a bottom support structure. In the heat transfer tube group of the waste heat recovery boiler, the heat transfer tubes ₁₂ are arranged in a staggered manner in order to increase the heat recovery rate of the exhaust gas from the turbine _. A finned heat exchanger tube 12a to which fins are attached is used.

On the other hand, as shown in Fig. 4, non-heat transfer spaces H ₁ and H ₃
The upper and lower headers 1 of the heat exchanger tubes 12 located at
In the vicinity of 9 and 13, the heat exchanger tubes 12 are arranged in order to collect them in the upper and lower headers 19 and 13, or to combine the upper and lower headers 19 and 13 with the heat exchanger tubes
For the purpose of connection, a bare heat exchanger tube 12b is used in place of the finned heat exchanger tube 12a.

For this reason, when the exhaust gas G from the gas turbine passes through the flue 100, the finned heat exchanger tube 1 is located in the heat transfer space _H2 in the upper and lower directions of the flue.
The ventilation resistance passing through the part 2a is the non-heat transfer space H ₁ ,
It is larger than the bare heat exchanger tube 12b portion located at _H3 .

Therefore, in the flue shown in Fig. 3, there are non-heat transfer spaces H ₁ and H ₃ near the upper internal casing 22 and lower internal casing 23 that do not participate in upper and lower heat exchange, and the exhaust gas G has low ventilation resistance. Non-heat transfer space H ₁ ,
It flows through H ₃ and becomes difficult to flow into the heat transfer space H ₂ where ventilation resistance is large.

In this way, a heat transfer space H ₂ that participates in heat exchange and non-heat transfer spaces H ₁ and H _{3 that do not directly participate in heat exchange are formed above and below the flue 100 in FIG. 3} .

Next, as shown in Fig. 4, in the width direction of the waste heat recovery boiler, the upper and lower headers 19, 13
Due to the connection between the heat exchanger tubes 12 and the heat exchanger tubes 12, non-heat transfer spaces W ₁ and W ₃ that do not directly participate in heat exchange are created between the heat exchanger tubes 12 and the side internal casings 20a and 20b. In this case, as shown in FIG. 2, the thickness of the heat insulating material 16 becomes thinner as it goes downstream of the flue, and the external dimensions of the upper and lower casings 17a, 17b are constant from upstream to downstream. The non-heat transfer spaces W ₁ and W ₃ become substantially wider. These non-heat transfer spaces W ₁ and W ₃ have less resistance when the exhaust gas G passes through them than in the heat transfer space W ₂ , so the pressure loss is smaller than in the heat transfer space W ₂ . Therefore, a large amount of exhaust gas G bypasses these non-heat transfer spaces W ₁ and W ₃ , and the heat recovery efficiency of the entire boiler is significantly reduced.

In addition, due to the bypass of this exhaust gas G, the headers 19, 13, etc., which are arranged in the non-heat transfer spaces H ₁ and H ₃ , which are not directly involved in heat exchange, are heated by the large amount of bypassed exhaust gas flow, and the metal temperature increases. will rise. For this reason, the design temperature of the members to be placed in this area must be set high, which has the disadvantage of increasing material costs.

Furthermore, since the header support 14, which is one of the members arranged in the non-heat transfer spaces H ₁ , H ₃ , W ₁ , W ₃ , is heated by the exhaust gas G that is unilaterally bypassed, the metal temperature naturally increases. However, since the lower header 13 itself, which is in contact with the support 14, is cooled by the internal fluid, a temperature difference inevitably occurs between the two, which generates stress. For this reason, it is necessary to adopt a structure that absorbs stress due to temperature differences, and the bottom support structure itself becomes even more complex.

Furthermore, the flow velocity increases in the non-heat transfer spaces _{H 1} , H ₃ , _{W 1 , W 3} due to the bypassed large amount of gas flow; There is also a risk that the high-speed gas flow may cause vibrations in the parts that have been exposed.

An object of the present invention is to eliminate the above-mentioned problems and provide a waste heat recovery device that has high heat recovery efficiency, generates little thermal stress, and does not generate vibrations.

In short, the present invention provides an apparatus for disposing a group of heat transfer tubes in a flue through which combustion exhaust gas passes and recovering heat in the exhaust gas, in which the central portion of the heat transfer tubes disposed in the flue, excluding both ends, is a finned heat transfer tube; Both ends are finless tube portions, and the finless tube portion is provided with a drift prevention plate for preventing uneven flow of exhaust gas, and the drift prevention plate is divided into a plurality of pieces and connected to the flue or heat exchanger tube header. This is a waste heat recovery device characterized by a structure that absorbs differences in expansion and contraction due to heat.

Embodiments of the present invention will be described below based on the drawings.

5 to 7 show an embodiment of the present invention, FIG. 5 is a side sectional view corresponding to FIG. 3 of the conventional structure, and FIG. 6 is a sectional view taken along the line C--C in FIG. 5. FIG. 7 is a sectional view taken along the line DD in FIG. 5.

In the embodiments shown in FIGS. 5 to 7, non-heat transfer spaces H ₃ ,
A drift prevention member 26 is arranged at each of H ₁ , W ₃ , and W ₁ .

That is, the exhaust gas G bypasses the non-heat transfer spaces H ₁ and _{H 3} formed above and below the flue as shown in FIGS. 5 to ₇ . In order to prevent this, the upper drift prevention member _26a and the lower drift prevention member _26b are arranged in the direction across the flue. As shown in FIG.
c and 26d.

By arranging the drift prevention members 26a to 26d in the non-heat transfer spaces H ₁ , H ₃ , W ₁ , W ₃ in this way, the drift of the exhaust gas G can be prevented, and the finned heat exchanger tubes 12 a
Improves heat recovery efficiency.

In addition, as shown in FIGS. 5 and 7, the non-heat transfer spaces H ₁ and H ₃ have a distance L ₁ in the flow direction of the exhaust gas G.
An upper drift prevention member 26a and a lower drift prevention member 26b are arranged for each of the non-heat transfer spaces W ₁ and W ₃ at a distance in the flow direction of the exhaust gas G as shown in FIG.
Since the side drift prevention members 26c, d are arranged for each _L2 , there are Since the exhaust gas G stagnation portion 28 is formed, the exhaust gas G can be prevented from bypassing the non-heat transfer spaces H ₁ , H ₃ , W ₁ , and W ₃ .

In addition, in FIGS. 5 to 7, the upper, lower and side drift prevention members 26a, 26b, 26
c and 26d are installed so as to be substantially orthogonal to the flow of the exhaust gas G, reinforcing ribs 27 are arranged on the back surfaces of these drift prevention members 26a, 26b, 26c, and 26d to reinforce them.

FIG. 8 shows details of how the lower drift prevention member 26b is attached to the flue. First, the lower internal casing 23 constituting the flue has the following structure in order to absorb thermal stress. For example, if we take the lower internal casing 23 of the flue as an example, it is divided into parts in the width direction of the flue, as shown by numerals 23 and 38, and each internal casing 23, 38 has a stud bolt 2.
9, is connected to the outer casing 24 by a nut 42 and a washer 44. (The bolt connection on the lower inner casing 38 side is not shown.) 41
is a slide plate, which is connected only to the lower internal casing 23 side, and is configured so that each internal casing 23, 38 can move relatively at the attachment part of this slide plate 41, so that the lower internal casing 23, 38 Comrades lower internal and external casings 23 and 24, 38
The structure is such that it can absorb the displacement caused by the temperature difference between and 24. Therefore, the lower drift prevention member 26b is also designated by the reference numeral 26 like the lower internal casings 23 and 38.
By dividing the flue 100 in the width direction as shown in b and 26b and configuring it to absorb thermal displacement caused by the exhaust gas G, the difference in elongation due to heat absorption between the casings and the drift prevention members can be reduced. It can be absorbed by the slide plate 41.

In the embodiments shown in FIGS. 5 to 7, upper and lower drift prevention members 26a, 26b and side drift prevention members are provided in the non-heat transfer spaces _{H1 , H3} and the non-heat transfer spaces W1, _W3 . Although the members 26c and 26d are arranged separately, as described above, by inserting the slide plate (see FIG. 8) in the vertical and horizontal directions, the upper and lower drift prevention members 26a and 26b are connected to the side drift prevention member 26c. ,2
If it is made into an integral structure by 6d, the drift prevention member 2
The manufacturing process and the installation process can be saved, and by arbitrarily selecting the size of the slide plate 41, the structure can absorb manufacturing errors in the drift prevention member 26 itself.

The one in FIGS. 9 and 10 is the drift prevention member 2.
6 shows another embodiment of the present invention, and the differences from the drift prevention member 26 shown in FIGS. 5 to 7 are as shown in FIGS. 5 to 7.
The drift prevention member 26 in FIG. 7 is arranged vertically to the non-heat transfer spaces H ₁ , H ₃ , W ₁ , W ₃ with respect to the flow direction of the exhaust gas G.
b, 26c, and 26d are arranged, but in the case of the drift prevention members 26 in FIGS. 9 and 10, only the upper and lower drift prevention members 26a and 26b are arranged at an angle with respect to the flow direction of the exhaust gas G. .

In the embodiment shown in FIG. 9, the upper and lower drift prevention members 26a and 26b are mounted obliquely at a predetermined angle α with respect to the flow direction of the exhaust gas G, and their upper ends are bent approximately horizontally. By forming a horizontal portion, the passage resistance of the exhaust gas G is reduced, and the rectification effect is also enhanced, thereby significantly reducing the pressure loss of the exhaust gas as a whole.

FIG. 10 shows a structure in which the vicinity of the lower header 13 is covered with a lower drift prevention member 26b, and instead of the reinforcing rib 27 in FIG.
The lower drift prevention member 26b is connected to the lower header 1 through the
The structure is supported by 3.

In this way, the vicinity of the lower header 13 is
By covering the header support 1 of the lower header 13 with the lower drift prevention member 26b as shown in the figure, the vicinity of the header can be kept at a low temperature.
4 becomes colder and its support structure can be released from the hot exhaust gas G.

Figures 11 to 13 show other embodiments. Figure 11 is a side sectional view of the flue, Figure 12 is a sectional view taken along the line F--F in Figure 11, and Figure 13 is a smoke pipe. It is a perspective view of the drift prevention member in the corner part of the road.

The difference from the ones in FIGS. 5 to 7, and FIGS. 9 and 10 is that in the ones shown in FIGS. Unbalanced flow prevention members 26a, 26b, 26
c, 26d, and the ninth
10, the drift prevention member 26 includes upper and lower drift prevention members 26a, 2
As shown in FIGS. 9 and 10, only the member 6b is inclined at an angle α along the flow direction of the exhaust gas G, and the side drift prevention members 26c and 26d are a combination of flat plate-like members.

On the other hand, those in FIGS. 11 to 13 have upper lower part and side drift prevention members 26a, 26b,
26c and 26d, all non-heat transfer spaces H ₁ ,
H ₃ , W ₁ , and W ₃ were affected.

The ones in Figures 11 to 13 are non-heat transfer spaces.
As shown in FIG. 11, upper drift prevention members 26a and 26a and lower drift prevention members 26b and 26b are connected to H ₁ and H ₃ , as shown in FIG.
26e to cover the non-heat transfer spaces H ₁ and H ₃ , and the non-heat transfer spaces W ₁ and W ₃ are provided with side drift prevention members 2
6c, 26c comrades or side drift prevention member 2
6d and 26d are connected by the unbalanced current prevention member 26e,
26e to cover the non-heat transfer spaces W ₁ and W ₃ .

In this way, the upper, lower, left, and right sides of the flue are covered by the drift prevention members 26, so that the drift of the exhaust gas G can be prevented. Because it is covered, the header 1 can be kept at a low temperature even if the exhaust gas G contains some dust.
It is possible to prevent dust from adhering to the vicinity of 9 and 13.

Note that the upper and lower drift prevention members 26a, 26
Between a, 26b, and 26b is a connecting part drift prevention member 2.
6e and 26e are connected to each other, and as shown in FIG.
A through hole is formed, and this through hole is formed to have a larger outer diameter than the bare heat exchanger tube 12b, and is configured to absorb thermal stress and elongation difference caused by the exhaust gas G. In this case, the connection part drift prevention member 26
A part of the exhaust gas G flows through the through hole e into the stagnation part 28.
Since the exhaust gas G is bypassed to some extent by flowing into the stagnation part 28, the bypass flow can be more effectively prevented by appropriately arranging the baffle 43 in the stagnation part 28.

As described above, in the embodiments of the present invention, only the waste heat boiler of a combined cycle power plant has been described, but the present invention is not limited to the present embodiments, and can be broadly applied to energy saving devices in which heat exchanger tubes are arranged in the flue, etc. It can also be applied to

By implementing this invention, bypass of exhaust gas can be significantly reduced in a non-heat transfer space that is not directly involved in heat exchange, so the heat exchange efficiency of the device can be significantly improved.

Furthermore, since the temperature rise of the members in the non-heat transfer space is small, the design temperature of the members to be installed in this area can be reduced, and the manufacturing cost of the device can be reduced. Furthermore, since the generation of thermal stress in a non-heat transfer space can be reduced, there is no need to employ a complicated structure for stress relief, and various other effects are exhibited.

Even existing ones can be easily modified by installing drift prevention members.

[Brief explanation of the drawing]

Figure 1 is an overall schematic diagram of the waste heat recovery boiler, Figure 2 is a side sectional view of the heat retention structure, and Figure 3 is A in Figure 1.
Figure 4 is a detailed cross-sectional view of the enlarged section of the section B- in Figure 3.
5 is a side view of a boiler device showing the first embodiment of the present invention, and FIG. 6 is a sectional view taken along line C-- in FIG.
A sectional view taken along the line C, FIG. 7 is a sectional view taken along the line D-D in FIG. 5,
FIG. 8 is an enlarged cross-sectional view taken along the line E-E in FIG. 5, and FIG. 9 is a cross-sectional view of the drift prevention member showing the second embodiment.
0 is a sectional view of a drift prevention member showing a modification of FIG. 9, FIG. 11 is a sectional view of a drift prevention member showing a third embodiment, and FIG. 12 is a sectional view taken along the line FF in FIG. 11. , FIG. 13 is a perspective partial view of the drift prevention member at the corner portion of the flue shown in FIGS. 11 and 12. 100... Flue, 12... Heat exchanger tube, 26, 26a,
26b, 26c, 26d, 26e...Difference prevention member, _H1 , _H3 , _W1 , _W3 ...Non-heat transfer space.

Claims (1)

[Claims] 1. In a device that collects heat from exhaust gas by arranging a group of heat transfer tubes in a flue through which combustion exhaust gas passes,
The center part of the heat exchanger tube placed in the flue, excluding both ends, is a heat exchanger tube with fins, and both ends are tubes without fins,
In addition, a drift prevention plate is provided in the finless pipe section to prevent drift of exhaust gas, and the drift prevention plate is divided into a plurality of pieces to absorb the difference in thermal expansion and contraction with the flue or the heat exchanger tube header. A waste heat recovery device characterized by having the following configuration.