JP6389723B2 - Multi-pipe once-through boiler - Google Patents

Description

  The present invention relates to a multitubular once-through boiler to which a steam separator is connected.

  Conventionally, in this type of multi-tube once-through boiler, steam generated in the water pipe becomes a steam-water mixture with saturated water and is sent to the steam-water separator through a connecting pipe connected to the upper header. Saturated water is swirled through a swirl flow forming part such as swirl vanes and centrifugal nozzles in the water separator, and due to the centrifugal action of the swirl flow, saturated water is brought into the inner wall side of the steam-water separator body due to the density difference between the steam and saturated water. The steam is biased to the inside of the swirling saturated water and discharged from the steam discharge pipe connected to the upper center of the steam separator, so that it is separated into steam and saturated water. The saturated water is sent and returned to the lower header of the boiler body by a return pipe connected to the lower part of the steam separator, and recirculated. With regard to this saturated water recirculation, the once-through boiler is defined by law as “the ratio of the circulation amount to the maximum water supply amount is 2 or less”.

  However, when the amount of circulating water is extremely small, the temperature and pH of the return pipe and the lower header at the lower part of the steam / water separator are lowered, which easily causes a corrosion failure. Therefore, in a once-through boiler, it is important to secure an appropriate amount of circulating water in all combustion regions within a range that does not exceed legal regulations.

  In the case of a once-through boiler using multistage control or proportional control for combustion amount control, the circulating water amount tends to decrease as the operating state shifts from a high load to a low load. This is because the boiling state in the water pipe is different and the absolute amount of steam flowing into the steam separator is different. In recent years, attention has been focused on boilers that reduce the purge loss by increasing the turn-down ratio (hereinafter referred to as TDR) from the viewpoint of energy saving and reducing the number of times the boiler starts and stops.

  However, if the TDR is wide, there is an ultra-low load state that is lower than the conventional minimum combustion amount. In such an ultra-low load state, the amount of circulating water is extremely reduced, and the pH of the return pipe and the lower header at the lower part of the steam-water separator will deviate from an appropriate management reference value.

  Therefore, as shown in FIG. 7, the connection pipe 22 that draws the connection pipe between the steam separator 20 and the upper header 21 from the side face of the upper header 21 and the connection pipe 23 that draws from the upper surface of the upper header 21. A connection structure of a multi-pipe once-through boiler air / water separator in which two connection pipes are installed is known (Patent Document 1).

  According to the connection structure shown in FIG. 7, the connection pipe 22 drawn from the side surface of the upper header 21 has less pressure loss than the connection pipe 23 drawn from the top, so that the amount of air-water mixture generated is low and the combustion is low. The majority of the air / water mixture flows into the steam / water separator 20 from the connecting pipe 22 drawn from the side surface of the upper header 21 and can secure a predetermined amount of saturated water return via the return pipe 24. Sometimes the flow rate of the air / water mixture is increased and the amount of steam supplied to the steam load is increased, so that the air / water mixture cannot be flowed only by the connecting pipe 22 drawn from the side but flows to the upper drawing connecting pipe 23. The amount of saturated water return can be increased or decreased by the flow rate to the upper drawer connecting pipe 23, and the return amount (circulation ratio) for high combustion and low combustion can be determined. As a result, an appropriate amount of return can be obtained even at low combustion. Is therefore the lower header in the reactor water can be kept in the proper pH, there is a corrosion of the can body with a low pH is reduced.

Japanese Utility Model Publication No. 6-40604

  However, as shown in FIG. 8, conventionally, in the swirl type steam / water separator 20, the swirl blade 25 (swirl flow forming portion) is affected by the centrifugal force due to swirling of the saturated water W, and is necessary in a low load region. Inflow of a large amount of circulating water is hindered, and in a high load region, saturated water W flows backward to the boiler side, which may cause a problem that the dryness of steam V separated and discharged is deteriorated.

  Therefore, the present invention reduces the influence of centrifugal force caused by swirling of saturated water in the steam separator, ensures a constant circulating water amount even in a low load state, and prevents a decrease in steam dryness. The main purpose is to provide a once-through boiler.

  In order to solve the above problems, a multitubular once-through boiler according to the present invention includes a connecting pipe that sends a mixture of steam and saturated water from the upper header to the swirl flow forming portion of the steam separator, the upper header, and the air header. A bypass pipe that communicates with a position lower than the swirl flow forming portion of the water separator, and the bypass pipe is provided with a distal end portion provided with a discharge port protruding into the steam-water separator. It is characterized by.

  The discharge port is preferably opened toward the downstream side of the saturated water swirl generated in the steam separator.

  It is preferable that the end of the bypass pipe is closed at the end, and the discharge port is formed on the side of the end.

  It is preferable to include a control valve interposed in the bypass pipe and a control device that controls the control valve to open when the boiler load is a predetermined value or less.

  The bypass pipe is preferably located at a position where the connection position to the steam separator is lower than the connection position to the upper header.

  It is preferable that the bypass pipe is connected to the steam / water separator at a height position that is the same level as a feed pipe connection position of the steam / water separator.

  The bypass pipe is preferably a pipe having an inner diameter smaller than that of the connecting pipe.

  According to the present invention, by projecting the tip of the bypass pipe into the steam / water separator, the bypass pipe becomes less susceptible to the centrifugal force of the swirling flow of saturated water, and the inflow of the necessary circulating water amount in the low load region. It is possible to prevent the saturated water from flowing back to the boiler side in a high load range.

It is a schematic structure figure showing a 1st embodiment of a multi-tube type once-through boiler concerning the present invention. It is a principal part cross-sectional view of the multitubular once-through boiler of FIG. It is a principal part cross-sectional view which shows 2nd Embodiment of the multi-tube type once-through boiler which concerns on this invention. It is a schematic block diagram which shows 3rd Embodiment of the multi-tube type once-through boiler which concerns on this invention. It is a schematic block diagram which shows 4th Embodiment of the multitubular once-through boiler which concerns on this invention. It is a schematic block diagram which shows 5th Embodiment of the multitubular once-through boiler which concerns on this invention. It is a schematic block diagram of the conventional multitubular once-through boiler. It is a center longitudinal cross-sectional view of the conventional steam separator.

  An embodiment of a multitubular once-through boiler according to the present invention will be described with reference to FIGS. In the present invention, the same or similar components are denoted by the same reference numerals throughout the drawings and the embodiments.

  As shown in FIG. 1, a first embodiment of a multi-tube once-through boiler according to the present invention includes a multi-tube once-through boiler 1, a boiler main body 2, a water pipe 3 disposed around the boiler main body 2, a water pipe 3, A lower header 4 and an upper header 5 connected to each other, a connecting pipe 7 for connecting the upper header and the steam separator 6, and a swirl flow forming unit 8 for rotating the air / water mixture sent from the connecting pipe 7; A bypass pipe 9 for connecting the upper header 5 and the steam separator 6 below the swirling flow forming section 8, a steam pipe 10 for exhausting steam separated from the saturated water by the swirling flow forming section 8, and a gas A return pipe 11 for connecting the water separator 6 and the lower header 4 and a water supply pipe 12 for supplying water to the steam separator 6 are provided. The combustion burner is not shown, and multistage control or proportional control is used for combustion control.

  The swirl flow forming portion 8 of the first embodiment is formed by guide vanes 8a fixed in the steam separator 6, and the steam boiled in the water pipe 3 passes through the connecting pipe 7 along with the saturated water and the guide vanes. When sent to the upper space 6a of the 8a, the steam-saturated water-water mixture becomes a swirling flow when passing through the guide vanes 8a, and a swirling flow of the air-water mixture is generated in the lower space 6b of the guide vanes 8a. Under the action of force, the steam and the saturated water are centrifuged due to the density difference, the steam is discharged from the steam pipe 10, and the saturated water becomes a swirling flow and is returned to the lower header 4 through the return pipe 11.

  As shown in an enlarged view in FIG. 2, the bypass pipe 9 has a distal end portion 9 b in which a discharge port 9 a is formed so as to protrude into the steam / water separator 6. By projecting the distal end portion 9b into the steam / water separator 6, the bypass pipe 9 is less likely to receive the centrifugal force of the swirling flow F of saturated water. As a result, it is possible to prevent the inflow of the necessary circulating water amount in the low load region, and to prevent the saturated water from flowing back to the boiler side in the high load region.

  The discharge port 9a of the tip 9b of the bypass pipe 9 is located away from the inner wall surface of the steam / water separator 6 and opens toward the downstream side in the swirling direction of the swirling flow F of the saturated water. With such a configuration, the distal end portion 9b of the bypass pipe 9 receives the swirling flow F of the saturated water on the peripheral side opposite to the discharge port 9a, and thus the influence of the centrifugal force of the swirling flow F of the saturated water is further reduced. The effect of preventing the inflow of the necessary circulating water amount in the load region and preventing the saturated water from flowing back to the boiler side in the high load region can be further enhanced. The discharge port 9a at the tip 9b of the bypass pipe 9 may be plural or one.

  Further, the distal end portion 9b of the bypass pipe 9 is closed at the distal end surface 9c, and the discharge port 9a is formed on the side surface of the distal end portion 9b, thereby preventing the flow of necessary circulating water in the low load region. Moreover, the effect which prevents that saturated water flows backward to the boiler side can be further heightened in a high load area.

  The bypass pipe 9 is preferably a pipe having an inner diameter smaller than that of the connecting pipe 7, and it is preferable that the air-water mixture is less likely to pass than the connecting pipe 7. A throttle (not shown) may be interposed in the bypass pipe 9.

  FIG. 3 shows a second embodiment of the multi-tube once-through boiler according to the present invention. In the second embodiment, the discharge port 9a of the distal end portion 9b of the bypass pipe 9 has a shape in which the pipe end is cut obliquely. It is said that. Also in this case, since the discharge port 9a opens toward the downstream side of the swirling flow F, the same technical effect as in the first embodiment can be obtained.

  FIG. 4 shows a third embodiment of the multi-tube once-through boiler according to the present invention. In 3rd Embodiment, the control valve 13 is interposed in the bypass pipe 9, and the control apparatus 14 which controls to open the control valve 13 when a boiler load is below a setting value is provided.

  The boiler load is a combustion amount by a combustion burner (not shown) of the boiler, and the combustion amount is proportional to the flow rate of the fuel gas supplied to the combustion burner. Therefore, the boiler load is known by measuring the flow rate of the fuel gas with a flow meter. be able to. When the combustion amount of the boiler (actual boiler load b) becomes equal to or less than the predetermined combustion amount (set boiler load a), the control valve 13 is controlled so that the control valve is “open”. The air / water mixture from the boiler body 2 is reliably supplied into the air / water separator 6 only during the low-load combustion operation that needs to be ensured, thereby ensuring the amount of circulating water. In addition, during high load combustion where the amount of circulating water can be secured and the control valve 13 is not required, the control valve is “closed”, so that the dryness of the saturated water flows back from the control valve 13 to the upper header 5. Decline can be prevented.

  FIG. 5 shows a fourth embodiment of the multi-tube tubular boiler according to the present invention. In the fourth embodiment, the bypass pipe 9 is connected to the steam separator 6 at a position lower than the connection position to the upper header 5. Since the high-temperature steam generated in the water pipe 3 tends to rise, this structure makes it difficult for steam to enter the steam-water separator 6 from the upper header 5 through the bypass pipe 9, and from the steam-water separator 6. The backflow of saturated water can also be limited.

  Moreover, in 4th Embodiment shown in FIG. 5, the bypass pipe 9 is connected with the steam-water separator 6 in the height position of the same level as the connection position of the water supply pipe 12 of the steam-water separator 6. A predetermined amount of a chemical such as sodium hydroxide is added to the water flowing through the water supply pipe 12 to prevent the corrosion of the boiler, and the steam separator is connected to the bypass pipe 9 and the water supply pipe 12 at the same level. By connecting to 6, the saturated water from the bypass pipe 9 and the water supplied from the water supply pipe 12 are quickly mixed, and the drug can be rapidly stirred. Further, the water supply pipe 12 is usually provided at a position lower than the water level at the neutral level of the steam separator 6, and the bypass pipe 9 is connected to the height position at the same level as the water supply pipe 12. The tip discharge outlet of the steam pipe 10 is installed at a position sufficiently away from the inlet 10a of the steam pipe 10, and the steam-water mixture from the bypass pipe 9 becomes difficult to be discharged from the steam pipe 10, and the steam exhausted from the steam pipe 10 This can prevent a decrease in dryness.

  FIG. 6 shows a fifth embodiment of the multitubular tube flow boiler according to the present invention, which is different from the first embodiment in that the swirling flow forming portion 8 is constituted by a centrifugal nozzle 8b, and other configurations. Since this is the same as that of the first embodiment, detailed description thereof is omitted. The swirl flow forming unit is not limited to the form of the first embodiment and the fifth embodiment, and other forms that make the flow of the air-water mixture from the connecting pipe 7 swirl can be adopted.

  The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Multipipe once-through boiler 2 Boiler main body 3 Water pipe 4 Lower header 5 Upper header 6 Gas-water separator 7 Connection pipe 8 Swirling flow formation part 9 Bypass pipe 9a Discharge port 9b Tip part 12 Water supply pipe 13 Control valve 14 Control apparatus

Claims (5)

A connecting pipe for sending a mixture of steam and saturated water from the upper header to the swirl flow forming section of the steam separator,
And a bypass pipe for connecting communicating the position lower than the swirling flow of the steam-water separator and the upper header,
The bypass pipe is provided with a distal end provided with a discharge port protruding into the steam-water separator, and the discharge port is opened toward the downstream side of the saturated water swirl flow generated in the steam-water separator. And a multi-pipe once-through boiler characterized in that the connection position to the steam separator is lower than the connection position to the upper header . A connecting pipe for sending a mixture of steam and saturated water from the upper header to the swirl flow forming section of the steam separator,
A bypass pipe that communicatively connects the upper header and a position lower than the swirl flow forming portion of the steam separator,
The bypass pipe is provided with a distal end provided with a discharge port protruding into the steam-water separator, and the discharge port is opened toward the downstream side of the saturated water swirl flow generated in the steam-water separator. And a multi-pipe once -through boiler characterized in that the inner diameter is smaller than that of the connecting pipe . The multi-pipe once -through boiler according to claim 1 or 2 , wherein an end face of the tip of the bypass pipe is closed and the discharge port is formed on a side surface of the tip. A control valve interposed in the bypass pipe, the boiler load according to claim 1, characterized in that it comprises a control device for controlling to open the control valve when the predetermined value or less Multi-tube once-through boiler. 2. The multi-pipe once -through boiler according to claim 1 , wherein the bypass pipe is connected to the steam / water separator at a height position that is the same level as a feed pipe connection position of the steam / water separator.

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