JP3934252B2 - Natural circulation water tube boiler - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a natural circulation type water tube boiler in which the circulation of saturated water in a steam drum is improved during start-up operation.
[0002]
[Prior art]
For example, natural circulation water tube boilers applied to thermal power plants or combined cycle power plants include vertical type and horizontal type, and either type is selected depending on the margin of installation area. Yes.
[0003]
Of the natural circulation type water tube boilers, the horizontal type is provided with a steam drum 100 and a precipitation collecting portion 108 on the outer side of a horizontally long duct D, and the steam drum 100 and the precipitation collecting portion 108 are arranged as shown in FIG. The precipitation pipe 101 and the evaporation pipe 103 to be connected to each other are accommodated in the duct D so as to intersect with the flow direction of the hot gas G.
[0004]
Further, the evaporating pipe 103 is provided with a header 102 between the precipitation collecting section 108 and a header 104 and a rising pipe 105 between the steam drum 100.
[0005]
The steam drum 100 contains a steam separator 106 therein.
[0006]
In the horizontal type natural circulation water tube boiler having such a configuration, the saturated water (water supply) supplied from the water supply pipe 109 to the steam drum 100 through the water level adjustment valve 110 is a precipitation pipe using a gravity difference. While being collected in the precipitation collecting section 108 via 101 and flowing from here to the evaporation pipe 103 via the header 102, heat exchange is performed with the hot gas G discharged from, for example, a gas turbine, etc. It circulates to the steam drum 100 through the header 104 and the rising pipe 105.
[0007]
In the steam drum 100, the gas-liquid two-phase flow is separated into saturated water and steam by the steam separator 106, and the separated steam is supplied to the other heat exchanger via the steam outlet 107 and separated. Saturated water is circulated through the downcomer 101 again.
[0008]
  In this way, the saturated water circulates through the steam drum 100 via the downpipe 101, the precipitation collecting portion 108, the header 102, the evaporation pipe 103, the header 104, and the ascending pipe 105 without borrowing external force such as a pump. Is called a natural circulation water tube boiler. Here, the principle of natural circulation will be explained in detail. The density of saturated water in the evaporation pipe 103 and the ascending pipe 105 is saturated from the temperature rise due to heating or a single-phase state as compared with the density of saturated water in the downcomer pipe 101. It becomes smaller due to the phase change to the gas-liquid two-phase state of water-steam, and the density of the saturated water in the evaporation pipe 103 and the ascending pipe 105 is different from the density of the saturated water in the downpipe 101, which corresponds to this density difference. Force acts on saturated water in the downcomer 101ThatIt is used. This force is called circulating force. The saturated water in the evaporating pipe 103 and the ascending pipe 105 whose density has become smaller and lighter due to the higher temperature is pushed up to the steam drum 100 by the saturated water in the downpipe 101 having a higher density and a higher density at a low temperature. The amount of saturated water in the natural circulation is determined from the balance between the circulation force and the pressure loss at which saturated water increases during circulation.
[0009]
Moreover, the circulation power of the saturated water generated in the horizontal natural circulation water tube boiler can be roughly divided into two. One is a portion where saturated water is heated and corresponds to the evaporation pipe 103. The remaining one is a non-heated part and corresponds to the riser 105.
[0010]
Of this circulation force, the circulation force generated in the evaporation pipe 103 is based on a gas-liquid two-phase flow of saturated water-steam due to convection or boiling caused by a rise in temperature of saturated water in the evaporation pipe 130. Further, the circulatory force generated in the rising pipe 105 is also convection or gas-liquid two that is generated as the temperature rises in the gas-liquid two-phase state of relatively high temperature water or saturated water-steam guided from the evaporation pipe 103 to the rising pipe 105. Based on phase flow. The circulation force generated in the ascending pipe 105 is generated with a time delay because the relatively high-temperature water or gas-liquid two-phase flow from the evaporation pipe 103 is supplied to the ascending pipe 105.
[0011]
However, in the horizontal natural circulation type water tube boiler, the length of the evaporation pipe 103 is longer than that of the rising pipe 105 even if there is a time delay of the circulating force in the rising pipe 105, and the evaporation pipe 103 is connected to the drum D. Since the saturated water is boiled immediately by intersecting with the flow of the hot gas G and the circulating force is given to the saturated water of the rising pipe 105, even if there is a time delay in the circulating force of the rising pipe 105 It has not been a big influence.
[0012]
On the other hand, as shown in FIG. 16, the vertical type includes a steam drum 100, a precipitation pipe 101, a precipitation collecting section 108, headers 102 and 104, and an ascending pipe 105 on the outside of a cylindrical duct D, and evaporates. The tube 103 is traversed in the flow direction of the hot gas G and accommodated in the duct D. Other configurations are the same as those of the horizontal type, and the description thereof is omitted.
[0013]
In the vertical-type natural circulation water tube boiler having such a configuration, the evaporation pipe 103 is disposed across the flow direction of the hot gas G, so that the evaporation pipe 103 ensures the circulating power of saturated water. However, the saturation power of the saturated water is ensured by the density difference between the saturated water boiling in the ascending pipe 105 and the saturated water in the downcomer pipe 101. For this reason, in the vertical type, the temperature rise of saturated water, the occurrence of a boiling phenomenon (two-phase flow phenomenon), the securing of the circulating power of saturated water, and the like were accompanied by a further time delay compared to the horizontal type.
[0014]
[Problems to be solved by the invention]
In the vertical natural circulation water tube boiler, the temperature of the saturated water (feed water) is low during start-up operation, the density difference between the saturated water in the riser 105 and the saturated water in the downpipe 101 is low, and almost no circulation force is generated. Therefore, the water is stopped until the saturated water in the evaporation pipe 103 reaches the saturation temperature. For this reason, when the saturated water stopped in the evaporation pipe 103 reaches the saturation temperature, it boils all at once and flows into the ascending pipe 105. At this time, if the temperature difference between the low-temperature saturated water (water supply) in the ascending pipe 105 and the high-temperature steam in the evaporation pipe 103 is large, there is a problem that water hammer is generated.
[0015]
In addition, in a vertical natural circulation water tube boiler, the pressure of saturated water is low during start-up operation, so the volume change rate accompanying the phase change of saturated water is large at the time of boiling, and transient excessive excessive circulation force is required. In addition, the void ratio is increased, and a large flow resistance is given to the evaporation pipe 103 and the ascending pipe 105 to cause pulsation.
[0016]
In addition, in the vertical natural circulation water tube boiler, the saturated water in the evaporation tube 103 flows to the ascending pipe 105 without exchanging heat with the hot gas G during start-up operation. There was a problem that the flow of water became intermittently unstable.
[0017]
The present invention has been made in view of such a problem, and continuously generates the circulating force of saturated water without interruption, and suppresses the pulsation and flow of saturated water to operate in a stable state. An object is to provide a circulating water tube boiler.
[0021]
[Means for Solving the Problems]
  The natural circulation water tube boiler according to the present invention is:To achieve the above objective,Claim 1As described above, a steam drum is mounted on the outside of the casing, a gas passage portion is formed in the casing, and the saturated water in the steam drum is again supplied to the steam through the precipitation pipe, the evaporation pipe, and the riser pipe. Circulate to drumSaddleIn the natural circulation water tube boiler, among the evaporation pipes arranged in the gas passage part, at least one of the uppermost stream side, the intermediate part and the most downstream side evaporation pipe toward the hot gas, and the upstream side toward the hot gas An evaporator pipe and a downstream evaporator pipe are divided, and the divided upstream evaporator pipe and the downstream evaporator pipe are connected by a U vent, and the inlet pipe of the upstream evaporator pipe and the outlet pipe of the downstream evaporator pipe are connected. The close pipe is positioned higher than the U vent.
[0025]
  Moreover, in order to achieve the said objective, the natural circulation type water tube boiler which concerns on this invention,Claim 2As described inSaidPlate-like fins are provided on the upstream side evaporation pipe and the downstream side evaporation pipe.
[0026]
  Moreover, in order to achieve the said objective, the natural circulation type water tube boiler which concerns on this invention,Claim 3As described inSaidThe plate-like fins are arranged in the same direction as the hot gas flow direction.
[0027]
  Moreover, in order to achieve the said objective, the natural circulation type water tube boiler which concerns on this invention,Claim 4As described inSaidThe plate-like fins are arranged with the density gradually increased from the inlet header of the evaporation tube toward the outlet header.
[0028]
  Moreover, in order to achieve the said objective, the natural circulation type water tube boiler which concerns on this invention,Claim 5As described inSaidA spiral fin is provided on the upstream side evaporation pipe and the downstream side evaporation pipe.
[0029]
  Moreover, in order to achieve the said objective, the natural circulation type water tube boiler which concerns on this invention,Claim 6As described inSaidThe spiral fins are arranged so that the front side and the back side of the evaporation tube are axisymmetric.
[0030]
  Moreover, in order to achieve the said objective, the natural circulation type water tube boiler which concerns on this invention,Claim 7As described inSaidThe riser pipe connected from the outlet pipe of the evaporation pipe arranged in the gas passage portion via the outlet connection pipe is connected to the steam drum as a single unit.
[0031]
  Moreover, in order to achieve the said objective, the natural circulation type water tube boiler which concerns on this invention,Claim 8As described inSaidThe ascending pipe is divided into a vertical portion in the same direction as the flow direction of the hot gas and an inclined portion that intersects the gas passage portion and is connected to the steam drum.
[0032]
  Moreover, in order to achieve the said objective, the natural circulation type water tube boiler which concerns on this invention,Claim 9As described inSaidThe vertical part of the rising pipe is accommodated in a hot box formed in the casing and formed outside the gas passage part.
[0033]
  Moreover, in order to achieve the said objective, the natural circulation type water tube boiler which concerns on this invention,Claim 10As described inSaidOut of the evaporation pipes arranged in the gas passage portion, the inlet pipe of the most upstream side, the middle part and the most downstream side of the evaporation pipe toward the hot gas, and the downcomer pipe are formed in the casing, and the gas It is housed in a hot box on the steam drum side formed outside the passage portion.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a natural circulation water tube boiler according to the present invention will be described with reference to the drawings and the reference numerals attached in the drawings.
[0037]
FIG. 1 is a schematic view showing a first embodiment of a natural circulation water tube boiler according to the present invention.
[0038]
The natural circulation water tube boiler according to the present embodiment includes a space-like hot box 11, 11 partitioned by gas baffles 9, 9 on both sides inside the casing 10 of a long cylindrical casing 10 arranged in a vertical direction. The gas passage section 12 is formed between the hot boxes 11 and 11 and guides the hot gas G discharged from the gas turbine, for example.
[0039]
The gas passage portion 12 accommodates the evaporation pipes 5 a and 5 h so as to intersect with the hot gas G flowing along the long cylindrical casing 10. The evaporation pipes 5a and 5h are connected to the steam drum 1 mounted on the outside of the casing 10 with the inlet pipes 4 and 4a, the inlet connection pipes 3 and 3 and the downcomer pipe 2 housed in the hot box 11 at one end. While being connected, the other end is connected to the steam drum 1 via outlet pipes 6 and 6 a, outlet connection pipes 7 and 7, and rising pipes 8 and 8 that are accommodated in the hot box 11.
[0040]
The steam drum 1 is separated by a steam / water separator 13 for separating the steam / saturated water gas-liquid two-phase flow guided from the risers 8 and 8 into steam and saturated water, and the steam / water separator 13. For example, a steam outlet 14 for supplying the steam to a steam turbine or the like. Of the evaporation pipes 5a and 5h, the most upstream and the most downstream evaporation pipes 5a and 5a facing the hot gas G are so-called from the inlet header pipes 4a and 4a to the outlet header pipes 6a and 6a. The upper right inclined straight pipe and the evaporation pipe 5h in the middle thereof are accommodated in the gas passage portion 12 as a so-called horizontal straight pipe from the inlet header 4 toward the outlet header 6.
[0041]
Next, the operation of the natural circulation water tube boiler according to the present embodiment will be described.
[0042]
The hot gas G flowing in the gas passage portion 12 in the vertical direction exchanges heat with saturated water (feed water) flowing in the evaporation pipes 5a and 5h. At that time, the saturated water flowing in the evaporation pipes 5a and 5h starts to boil, becomes a vapor-liquid two-phase flow of steam-saturated water, and rises through the outlet header pipes 6 and 6a and the outlet connection pipes 7 and 7. It flows into the tubes 8 and 8. Then, the fluid that has become a two-phase flow of gas-liquid mixing rises through the risers 8 and 8 and flows into the steam drum 1 through the steam separator 13.
[0043]
The steam drum 1 separates the gas-liquid two-phase flow of steam-saturated water into steam and saturated water by the steam-water separator 13. The separated steam is supplied to, for example, a steam turbine through the steam outlet 14. The separated saturated water descends the downcomer pipe 2 and circulates again to the evaporation pipes 5a and 5h via the inlet connecting pipes 3 and 3 and the inlet headers 4a and 4.
[0044]
During the start-up operation, the saturated water in the downcomer pipe 2 and the ascending pipes 8 and 8 are both in a stopped state because the temperature is low, the temperature difference is small, and no circulatory force is generated. For this reason, the saturated water in the evaporation pipes 5a and 5h reaches the saturation temperature by heat exchange with the hot gas G, and starts boiling at once. The fluid that has become a gas-liquid two-phase flow flows into the steam drum 1 through the outlet header pipes 6 a and 6, the outlet connection pipes 7 and 7, and the ascending pipes 8 and 8. At this time, the rising water 8 and the saturated water of the steam drum 1 are heated by mixing with the high-temperature gas-liquid two-phase flow. The heated saturated water is circulated again with a slight temperature rise to the evaporation pipes 5a and 5h through the downcomer pipe 2, the inlet connecting pipes 3 and 3, and the inlet header pipes 4a and 4.
[0045]
At that time, the uppermost stream side and the most downstream side evaporation pipes 5a, 5a toward the hot gas G are so-called upper right inclined straight pipes toward the outlet headers 6a, 6a. When heat exchanges with the hot gas G, a circulatory force is generated by convection, and the circulatory force is generated before the gas-liquid two-phase flow. The saturated water that has become high-temperature water flows into the rising pipes 8 and 8 through the outlet header pipes 6a and 6 and the outlet connecting pipes 7 and 7, and the temperature of the saturated water in the rising pipes 8 and 8 is increased by convection. Promote. Further, the saturated water in the evaporation pipes 5a and 5h becomes higher as it goes to the outlet header 6a and 6 side by convection, and the saturated water on the outlet header 6a and 6 side quickly reaches the saturation temperature and boils. Therefore, the circulation force by the gas-liquid two-phase flow is promoted more quickly.
[0046]
Thus, in the present embodiment, the evaporation pipes 5a and 5a arranged on the most upstream side and the most downstream side facing the hot gas G are formed in a so-called upper right inclined straight pipe, which is much faster than before. Since the circulation force of the saturated water is promoted, the start-up operation can be further shortened without causing pulsation or stoppage in the water hammer and the saturated water during the start-up operation.
[0047]
FIG. 2 is a schematic view showing a second embodiment of the natural circulation water tube boiler according to the present invention. In addition, the same code | symbol is attached | subjected to the same part as the component of 1st Embodiment or a corresponding part.
[0048]
The natural circulation water tube boiler according to the present embodiment includes bent portions 15a and 15a that are bent toward the downstream side of the hot gas G at the intermediate portion of the most upstream and downstreammost evaporation tubes 5a and 5a that face the hot gas G. An inclined straight pipe having a steep angle is formed from the bent portions 15a and 15a toward the outlet header pipes 6a and 6a. Since other configurations are the same as those of the first embodiment, description thereof is omitted.
[0049]
Thus, in the present embodiment, the bent portions 15a and 15a are formed toward the downstream side of the hot gas G in the middle part of the most upstream and downstreammost evaporation pipes 5a and 5a facing the hot gas G, A straight straight pipe with a steep angle from the bent portions 15a, 15a toward the outlet header pipes 6a, 6a is formed to promote the circulating power of the saturated water. The start-up operation can be further shortened without causing any other problems.
[0050]
FIG. 3 is a schematic view showing a third embodiment of the natural circulation water tube boiler according to the present invention. In addition, the same code | symbol is attached | subjected to the same part as the component of 1st Embodiment or a corresponding part.
[0051]
The natural circulation water tube boiler according to the present embodiment accommodates the inlet headers 4a, 4, 4a and the outlet headers 6a, 6, 6a in the hot box 11 on the steam drum 1 side, and is suitable for the hot gas G. The most upstream side, intermediate portion, and most downstream side evaporation pipes 5a, 5h, 5a are connected to the upstream side evaporation pipe 5a.₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂The upstream side evaporating pipe 5a₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂Are formed in a so-called U-shaped pipe connected by a U vent 16, while the uppermost stream side and the most downstream side evaporation pipes 5 a, 5 a are formed in a so-called right-downward slope with respect to the flow direction of the hot gas G. Is.
[0052]
In the natural circulation type water tube boiler having such a configuration, during the start-up operation, the upstream of the evaporation tubes 4a, 4 and 4a from the steam drum 1 through the precipitation tube 2, the inlet connection tube 3, and the inlet header 4a. Side evaporation pipe 5a₁, 5a₁The saturated water supplied to is heated to a high temperature by heat exchange with the hot gas G, and a circulation force is generated due to the density difference based on the high temperature. In this case, the upstream-side evaporation pipe 5a formed in a right-downward inclined shape among the most upstream-side and most downstream-side evaporation pipes 5a, 5a.₁, 5a₁Since the head on the U vent 16 side is slightly higher than the head on the inlet side, the water head on the U vent 16 side becomes relatively high, and boiling occurs during heat exchange with the hot gas G. It is possible to suppress the generation of bubbles based on the above and maintain a good circulation force based on the density difference of saturated water.
[0053]
The U-vent 16 is reversed and the downstream side evaporation pipe 5a₂, 5a₂The saturated water toward the heat exchanges again with the hot gas G, and the temperature rises to generate bubbles based on boiling. However, the saturated water at this time has a low density, and the upstream side evaporation pipe 5a.₁, 5a₁Since the pressing force (circulating force) of saturated water guided from the air overcomes bubbles that become flow resistance, the pressing force (circulating force) causes the steam drum 1 to pass through the outlet header pipe 6a and the ascending pipe 8. Flows well.
[0054]
  Thus, in this embodiment, the inlet header 4a, 4, 4a and the outlet header 6a, 6, 6a are accommodated in the hot box 11 on the steam drum 1 side, and the evaporation tubes 5a, 5a are connected to the hot gas G. And the upper evaporating pipe 5a out of the evaporating pipes 5a and 5a.₁, 5a₁Slightly on the U vent 16 sideIs getting higherSince the generation of bubbles based on boiling of saturated water is suppressed using the water head and the circulating power of saturated water is secured, the start-up operation does not cause pulsation or stoppage of the saturated water during start-up operation. Can be further shortened.
[0055]
FIG. 4 is a schematic view showing a fourth embodiment of the natural circulation water tube boiler according to the present invention. In addition, the same code | symbol is attached | subjected to the same part as the component of 1st Embodiment or a corresponding part.
[0056]
The natural circulation type water tube boiler according to the present embodiment intersects with the flow of the hot gas G and is divided toward the flow of the hot gas G, the most upstream side, the middle portion, and the most downstream side evaporation tubes 5a, 5h. , 5a, at least two or more evaporator tubes are bent as separate evaporator tubes, and the evaporator tube 17a is bent.₁17a₂Is provided.
[0057]
Bent evaporator tube 17a₁17a₂May be formed in a V-shape toward the flow of the hot gas G, and is initially made to be horizontal and transverse to the flow of the hot gas G. A so-called upper right slope may be used.
[0058]
As described above, in the present embodiment, at least two or more of the most upstream side, intermediate portion, and most downstream side evaporation pipes 5a, 5h, 5a divided toward the flow of the hot gas G are separated. The evaporation tube 17a is bent as the evaporation tube₁17a₂Since the circulatory force of saturated water is reliably ensured, saturated water can be flowed satisfactorily during start-up operation.
[0059]
FIG. 5 is a schematic view showing a fifth embodiment of the natural circulation water tube boiler according to the present invention. In addition, the same code | symbol is attached | subjected to the same part as the component part of 1st Embodiment and 3rd Embodiment, or a corresponding part.
[0060]
As in the third embodiment, the natural circulation water tube boiler according to the present embodiment accommodates the inlet headers 4a, 4, 4a and the outlet headers 6a, 6, 6a in the hot box 11 on the steam drum 1 side. At the same time, the most upstream side and the most downstream side evaporation pipes 5a, 5h, 5a facing the hot gas G are connected to the upstream side evaporation pipe 5a.₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂The upstream side evaporating pipe 5a₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂Are formed in a so-called U-shaped pipe connected by a U vent 16, while the most upstream side and the most downstream side evaporation pipes 5 a, 5 a are formed in a so-called downward sloping shape in the flow direction of the hot gas G, Upstream evaporator tube 5a₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂Each is provided with a plate-like fin 18.
[0061]
As shown in FIG. 6, the plate-like fins 18 are formed on the upstream side evaporation pipe 5a.₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂The upstream-side evaporation pipe 5a is at an angle θ with respect to the horizontal pipe axis HL and the vertical pipe axis VL and is in the same direction as the flow direction of the hot gas G.₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂Is fixed.
[0062]
Thus, in the present embodiment, the upstream side evaporation pipe 5a₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂The plate-like fins 18 are respectively provided, and the plate-like fins 18 are arranged at positions that are at the same angle as the flow direction of the hot gas G with respect to the horizontal tube axis HL and the vertical tube axis VL. Since the rectifying effect is given to the flow of the gas, the upstream-side evaporation pipe 5a without causing the hot gas G to drift.₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂Each saturated water can be heated evenly.
[0063]
FIG. 7 is a schematic view showing a sixth embodiment of the natural circulation water tube boiler according to the present invention. In addition, the same code | symbol is attached | subjected to the same part as the component part of 1st Embodiment and 3rd Embodiment, or a corresponding part.
[0064]
The natural circulation type water tube boiler according to the present embodiment includes an upstream-side evaporation tube 5a in the most upstream, intermediate and downstream-side evaporation tubes 5a, 5h, 5a facing the hot gas G shown in the third embodiment.₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂Each is provided with a helical fin 19.
[0065]
As shown in FIG. 8, when the same direction as the flow direction of the hot gas G is defined as the hot gas flow reference line HGVL, the spiral fin 19 has an angle θ with respect to the hot gas flow reference line HGVL.₂Are arranged. The upstream side evaporation pipe 5a₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂When the angle between each horizontal tube axis HL and the transverse cross section of the flow of the hot gas G is θ1, the spiral fin 19 has an angle (θ₂−θ₁) Or angle (θ₂+ Θ₁) And the vertical evaporation pipe 5a as a reference.₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂Is arranged.
[0066]
In addition, the spiral fin 19 has an upstream side evaporation pipe 5a on the front side (front side toward the paper surface) with the vertical pipe axis VL as a reference.₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂However, the rear side (back side toward the paper surface) is also upstream of the above-mentioned vertical pipe axis VL as the upstream side evaporation pipe 5a.₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂It is so-called axially symmetric.
[0067]
Thus, in the present embodiment, the upstream side evaporation pipe 5a₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂Are provided with spiral fins 19, and the spiral fins 19 are connected to the respective evaporation tubes 5 a with respect to the vertical tube axis VL.₁, 5a₂, 5h₁, 5h₂,... Are arranged on the front side and the back side, and the flow of the hot gas G with respect to the spiral fins 19 provided on the front side and the back side is made symmetrical. Side evaporation pipe 5a₁, 5h₁, 5a₁And the downstream evaporation pipe 5a₂, 5h₂, 5a₂Each saturated water can be heated evenly.
[0068]
FIG. 9 is a schematic view showing a seventh embodiment of the natural circulation water tube boiler according to the present invention. In addition, the same code | symbol is attached | subjected to the same part as the component of 1st Embodiment or a corresponding part.
[0069]
The natural circulation type water pipe boiler according to the present embodiment includes outlet headers 6a, 6, 6a and ascending pipes 8 in the uppermost stream side, the middle part and the most downstream side evaporation pipes 5a, 5h, 5a facing the hot gas G, The outlet connecting pipes 7, 7, 7 that connect 8, 8 are arranged in an inclined shape toward the downstream side in the flow direction of the hot gas G.
[0070]
During the start-up operation, the saturated water is in a stopped state because the temperature difference between the saturated water (feed water) in the downcomer pipe 2 and the ascending pipes 8, 8, and 8 is small and no circulation force is generated. For this reason, until the saturated water in the evaporation pipes 5a, 5h, 5a starts to boil by heat exchange with the hot gas G, only the circulation force by convection is generated until the circulation force by the two-phase flow is generated.
[0071]
In addition, the outlet connection pipes 6a, 6, 6a and the outlet connection pipes 7, 7, 7 are non-heated portions. When the outlet connection pipes 7, 7, 7 are arranged horizontally or vertically, convection is suppressed. Moreover, the generation of circulating force is also suppressed.
[0072]
This embodiment pays attention to such a point, and the outlet connection pipes 7, 7, and 7 are arranged in a so-called upper right slope toward the downstream side in the flow direction of the hot gas G. .
[0073]
Therefore, according to the present embodiment, the outlet connecting pipes 7, 7, and 7 are arranged in an inclined shape on the upper right side toward the downstream side in the flow direction of the hot gas G to promote convection. The heating power of the saturated water can secure the circulating power of the saturated water, the securing of the circulating power of the saturated water allows the saturated water to reach the saturation temperature earlier and the boiling can be accelerated, and the saturated water can be circulated well. it can.
[0074]
FIG. 10 is a schematic view showing an eighth embodiment of a natural circulation water tube boiler according to the present invention. In addition, the same code | symbol is attached | subjected to the same part as the component of 1st Embodiment and 5th Embodiment, or a corresponding part.
[0075]
The natural circulation water tube boiler according to the present embodiment is a plate-like fin 18 fixed to the uppermost stream side, the middle part, and the most downstream side evaporation pipes 5a, 5h, 5a facing the hot gas G shown in the fifth embodiment. Are arranged with gradually increasing density from the inlet header pipes 4a, 4, 4a toward the outlet header pipes 6a, 6, 6a.
[0076]
Thus, in this embodiment, since the plate-like fins 18 are arranged with the density gradually increased from the inlet header pipes 4a, 4, 4a toward the outlet header pipes 6a, 6, 6a, The generation of circulating force due to convection can be accelerated even more quickly.
[0077]
FIG. 11 is a schematic view showing a ninth embodiment of the natural circulation water tube boiler according to the present invention. In addition, the same code | symbol is attached | subjected to the same part as the component of 1st Embodiment or a corresponding part.
[0078]
The natural circulation type water tube boiler according to the present embodiment includes the outlet pipes 6a, 6, 6a and the outlet connecting pipe 7 from the most upstream side, intermediate part, and most downstream side evaporation pipes 5a, 5h, 5a facing the hot gas G. , 7, 7 and the riser pipe 8 connected together as one, and the riser pipe 8 crosses the vertical part 8 a and the gas passage part 12 facing the same direction as the flow direction of the hot gas G, It is divided into inclined portions 8b intersecting with the flow of the hot gas G.
[0079]
Since the upstreammost and downstreammost evaporating pipes 5a and 5a facing the hot gas G are inclined toward the downstream side with respect to the flow of the hot gas G, the saturated water (feed water) is hot gas. When heated with G, convection occurs and the circulation force is generated quickly. However, since the middle portion of the evaporation pipe 5h is disposed horizontally across the hot gas G, even if the saturated water is heated by the hot gas G, no circulating force is generated until it boils.
[0080]
Further, during the start-up operation, the heat of the hot gas G before the operation remains in the gas passage portion 12.
[0081]
The present embodiment pays attention to such points, and the rising pipes 8 are collectively shared and are generated earlier in the uppermost stream side and the most downstream side evaporation pipes 5a and 5a facing the hot gas G. The circulatory force of saturated water is transmitted to the saturated water in the middle portion of the evaporation pipe 5h to promote the circulatory force.
[0082]
In the present embodiment, the rising pipe 8 is divided into a vertical portion 8a and an inclined portion 8b, and the residual heat of the hot gas G remaining in the gas passage portion 12 is used to circulate saturated water in the inclined portion 8b. It promotes power.
[0083]
Therefore, according to the present embodiment, the saturation in the evaporation pipe 5h in the middle portion is compared with the generation of the circulating force of saturated water in the evaporation pipes 5a and 5a on the most upstream side and the most downstream side toward the hot gas G. Since the point where the generation of the water circulation force is delayed is compensated, the generation of the circulation force of the saturated water in the middle portion of the evaporation pipe 5h can be further accelerated.
[0084]
In the present embodiment, the rising pipe 8 is shared and shared, and the rising pipe 8 is divided into a vertical portion 8a and an inclined portion 8b, and the vertical portion 8a is disposed outside the casing 10. However, not limited to this embodiment, the vertical portion 8a may be installed in the hot box 11, for example, as shown in FIG. 12, and the downcomer 2, for example, as shown in FIG. You may install in the hot box 11 by the side of the steam drum 1. Since the heat of the hot gas remains in each hot box 11, it is advantageous to accelerate the circulation force of the saturated water in each of the evaporation pipes 5a, 5h, 5a even more quickly.
[0085]
FIG. 14 is a schematic view showing a tenth embodiment of a natural circulation water tube boiler according to the present invention. In addition, the same code | symbol is attached | subjected to the same part as the component part of 1st Embodiment and 8th Embodiment, or a corresponding part.
[0086]
  The natural circulation water tube boiler according to the present embodiment includes evaporation pipes 5a, 5h, and 5a including plate fins 18 on the most upstream side, the middle part, and the most downstream side toward the hot gas G shown in the eighth embodiment. The riser pipes 8a, 6, 6a and the riser pipes 8 connected via the outlet connection pipes 7, 7, 7 are collectively shared, and the shared riser pipe 8 and the downcomer pipe 2 are shared with the steam drum 1. In the hot box 11 on the sideWith placementThe outlet connecting pipes 7, 7, 7 that connect the outlet pipes 6 a, 6, 6 a and the shared ascending pipe 8 are arranged in an inclined manner toward the downstream side in the flow direction of the hot gas G.
[0087]
Thus, in the present embodiment, the shared riser pipe 8 and the downcomer pipe 2 are disposed in the hot box 11 on the steam drum 1 side, and the outlet connection pipes 7, 7, 7 are arranged in the flow direction of the hot gas G. Since the residual heat of the hot gas G in the hot box 11 is effectively utilized by being arranged in an inclined shape toward the downstream side, the generation of the circulating force of saturated water in each of the evaporation pipes 5a, 5h, 5a is made even faster. Can be promoted.
[0088]
【The invention's effect】
As described above, the natural circulation type water tube boiler according to the present invention adds various devices to the precipitation pipe, the evaporation pipe, the outlet connection pipe, and the riser pipe, thereby increasing the circulation force by the convection of saturated water (feed water) in each pipe. Since it was generated even earlier, the start-up operation can be further shortened without causing water hammer, pulsation, and flow stoppage in the saturated water during the start-up operation.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a first embodiment of a natural circulation water tube boiler according to the present invention.
FIG. 2 is a schematic view showing a second embodiment of a natural circulation water tube boiler according to the present invention.
FIG. 3 is a schematic view showing a third embodiment of a natural circulation water tube boiler according to the present invention.
FIG. 4 is a schematic view showing a fourth embodiment of a natural circulation water tube boiler according to the present invention.
FIG. 5 is a schematic view showing a fifth embodiment of a natural circulation water tube boiler according to the present invention.
FIG. 6 is an enlarged view showing a plate-like fin in the fifth embodiment.
FIG. 7 is a schematic view showing a sixth embodiment of the natural circulation water tube boiler according to the present invention.
FIG. 8 is an enlarged view showing a spiral fin in the sixth embodiment.
FIG. 9 is a schematic view showing a seventh embodiment of the natural circulation water tube boiler according to the present invention.
FIG. 10 is a schematic view showing an eighth embodiment of a natural circulation water tube boiler according to the present invention.
FIG. 11 is a schematic view showing a ninth embodiment of the natural circulation water tube boiler according to the present invention.
FIG. 12 shows a ninth embodiment of a natural circulation water tube boiler according to the present invention.1st modification is shownSchematic.
FIG. 13 shows a ninth embodiment of a natural circulation water tube boiler according to the present invention.2nd modification is shownSchematic.
FIG. 14 is a schematic view showing a tenth embodiment of a natural circulation water tube boiler according to the present invention.
FIG. 15 is a schematic view showing a conventional horizontal type natural circulation water tube boiler.
FIG. 16 is a schematic view showing a conventional vertical-type natural circulation water tube boiler.
[Explanation of symbols]
1 Steam drum
2 downpipe
3 Inlet connection pipe
4,4a Entrance pipe
5a, 5h Evaporating tube
5a₁, 5h₁  Upstream evaporator tube
5a₂, 5h₂  Downstream evaporation pipe
6,6a outlet outlet
7 Outlet connection pipe
8 Ascending pipe
8a Vertical section
8b Inclined part
9 Gas baffle
10 Casing
11 Hot box
12 Gas passage
13 Air-water separator
14 Steam outlet
15a bent part
16 U vent
17a₁17a₂  Bent evaporator tube
18 plate fins
19 Spiral fin
100 steam drum
101 downpipe
102
103 Evaporation tube
104 header
105 riser
106 Air-water separator
107 Steam outlet
108 Precipitation set
109 Water supply pipe
110 Water level adjustment valve

Claims (10)

A vertical type in which a steam drum is mounted on the outside of the casing, a gas passage is formed in the casing, and the saturated water in the steam drum is circulated again to the steam drum through the precipitation pipe, the evaporation pipe, and the riser pipe In the natural circulation water tube boiler, among the evaporation pipes arranged in the gas passage part, at least one of the most upstream side, the middle part and the most downstream side evaporation pipes toward the hot gas, and upstream toward the hot gas. A side evaporation pipe and a downstream evaporation pipe are divided, and the divided upstream evaporation pipe and the downstream evaporation pipe are connected by a U vent, and the inlet egress pipe of the upstream evaporation pipe and the outlet of the downstream evaporation pipe are connected. A natural circulation type water pipe boiler characterized in that a header pipe is positioned higher than the U vent. Natural circulation water tube boiler according to claim 1, characterized in that a plate-shaped fins on the upstream evaporator tube and downstream evaporator tube. The natural circulation water tube boiler according to claim 2 , wherein the plate fins are arranged in the same direction as a flow direction of the hot gas. 3. The natural circulation water tube boiler according to claim 2 , wherein the plate-like fins are arranged with a density gradually increased from an inlet header of the evaporation tube toward an outlet header. Natural circulation water tube boiler according to claim 1, characterized in that a spiral fin to the upstream evaporator tube and downstream evaporator tube. 6. The natural circulation water tube boiler according to claim 5 , wherein the spiral fins are arranged so that the front side and the back side of the evaporation tube are axisymmetric. The riser which connects via an outlet connection pipe from the outlet pipe pulling tube evaporator tube disposed in the gas passage, and to one of claims 1 to 6, characterized in that is connected to the steam drum The natural circulation water tube boiler according to any one of the preceding claims. 8. The natural circulation type according to claim 7 , wherein the rising pipe is connected to a steam drum by being divided into a vertical portion in the same direction as the flow direction of the hot gas and an inclined portion intersecting the gas passage portion. Water tube boiler. 9. The natural circulation water tube boiler according to claim 8, wherein the vertical portion of the rising pipe is housed in a hot box formed in the casing and formed outside the gas passage portion. Wherein among the evaporation pipe be placed in the gas passage, the most upstream side toward the hot gas, an inlet pipe pulling tube evaporator tubes of the intermediate portion and the most downstream side, the downcomer, formed in the casing, the The natural circulation type water tube boiler according to any one of claims 1 to 9, wherein the natural circulation water tube boiler is housed in a hot box on the steam drum side formed outside the gas passage portion.

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