JP5514709B2 - A once-through boiler capable of adjusting the fluid temperature in the heat transfer tube at the furnace outlet - Google Patents

Description

  The present invention relates to a once-through boiler, and more particularly to a once-through boiler suitable for suppressing an unbalance of steam temperature of a fluid in a heat transfer pipe passing through each part of a furnace water wall at a furnace outlet.

  The temperature of the fluid in the furnace outlet heat transfer tube of the once-through boiler can be controlled by configuring a spiral wall that rises spirally in the furnace, thereby suppressing steam temperature imbalance due to uniform heat absorption and heat transfer tubes at the furnace inlet. The steam temperature is made uniform by installing an orifice in the connecting pipe and adjusting the flow rate of each part of the furnace water wall. However, the combustion in the furnace is not necessarily uniform and changes dynamically, so that it is difficult to eliminate the fluid temperature imbalance by the above-described method.

  As a prior art for eliminating the imbalance of the fluid temperature in the heat transfer tube at the furnace outlet, for example, Patent Document 1 proposes to provide a mixing device in the middle part of the furnace. An embodiment disclosed in Patent Document 1 is shown in FIG. According to the embodiment shown in FIG. 5, by installing the furnace intermediate mixing device 23, the enthalpy of the steam flowing into each mixing device is made uniform, but there is no connecting pipe that connects the left and right and front and rear of the furnace, It has a structure in which the left and right and front and rear fluids of the furnace cannot be interchanged. With this structure, the imbalance between the front wall of the furnace and the left and right fluid temperatures cannot be resolved.

  Moreover, sectional drawing of the furnace intermediate header part of another Example of patent document 1 is shown in FIG. 6, and the side view is shown in FIG. According to another embodiment shown in FIG. 6 and FIG. 7, by installing a header partition wall 34 inside the intermediate header 35 of the furnace and inserting a twist in the central portion of the header, It is structured to mix and replace the fluid. In this structure, since the fluid is exchanged only inside each furnace intermediate gap, it is limited to the left and right exchange and fluid mixing limited to the inside of the header, and left and right of the entire furnace water wall caused by combustion. And fluid temperature imbalance before and after has not been resolved.

JP-A-8-327007

  The prior art as disclosed in the above-mentioned Patent Document 1 does not replace the left and right or the front and rear of the entire furnace, and does not directly pour water into the middle of the furnace. It is difficult to eliminate the fluid temperature imbalance in the heat transfer tube at the furnace outlet due to the difference in the amount of heat absorption between left and right or front and rear.

  On the other hand, in a boiler with a high steam condition (for example, a high steam temperature of 700 ° C.) in which the superheater outlet steam temperature is increased compared to the conventional one, the size of the furnace is determined from the combustion performance, and the relative Even if the heat absorption rate is equivalent to that of a conventional boiler, the superheater outlet steam enthalpy rises, so the enthalpy of the furnace outlet fluid also rises, and the furnace outlet fluid temperature (the output of the furnace upper outlet header leading to the superheater) Temperature) increases, so fluid temperature imbalance increases. There is a risk that the furnace will be damaged by the thermal stress generated by this fluid temperature imbalance. For this reason, in a boiler in which the boiler superheater outlet temperature has been raised compared to the conventional boiler, it is necessary to suppress the unbalance of the expanded fluid temperature and reduce the furnace outlet fluid temperature for the suppression, compared to the conventional boiler. There is.

  Even if the fluid is partially mixed in the middle of the furnace as in the prior art disclosed in Patent Document 1 above, the front wall from the front wall to the front wall at the lower part of the furnace and the upper part of the furnace, the rear wall When the internal fluid passes through the same location on the cross section of the furnace to the rear wall, the left and right or front and rear heat absorption imbalance due to combustion is not eliminated.

  An object of the present invention is to suppress an imbalance in the boiler outlet fluid temperature of the boiler by replacing the left and right walls or the front and rear walls of the heat transfer pipe fluid passing through each part of the furnace water wall at the middle part of the furnace.

In order to solve the above problems, the present invention adopts the following configuration.
A furnace having an inner wall consisting of a front wall, a rear wall, a left side wall, and a right side wall; a heat transfer tube provided on the inner wall; and a burner provided at a lower portion of the furnace, wherein the fluid in the heat transfer tube In the once-through boiler that absorbs heat from the combustion gas in the furnace,
Four furnace lower outlet headers that draw fluid in the heat transfer tubes corresponding to the inner walls are provided in the middle of the furnace above the burner, and the fluids fed from the four furnace lower outlet headers are mixed. Two fluid mixing means are provided, and two fluid distribution means are provided to supply the mixed fluid from the two fluid mixing means through respective connecting pipes, and the fluid is supplied from the two fluid distribution means. Provided in the middle part of the furnace, and the two fluid mixing means collect and mix the fluid from the furnace lower outlet header arranged on the left and right sides of the furnace, left and right respectively. The mixed fluid is supplied to each fluid distribution means through each communication pipe, and the two fluid distribution means exchange the fluid in the left and right heat transfer tubes of the furnace between the lower part and the upper part of the furnace. A structure forming a fluid flow path to the on so that four of the furnace upper inlet pipe pulling.

  Further, in the once-through boiler, instead of collecting and mixing the fluids at the left and right sides of the furnace, the fluids are collected and mixed before and after the furnace, and between the lower and upper parts of the furnace, Forming a fluid flow path to replace the fluid. Furthermore, a spray device for injecting water from the boiler feed pump outlet or water branched from a plurality of high-pressure feed water heaters is provided in the connecting pipe. Furthermore, the fluid temperature at the furnace outlet is measured, and the amount of water injected into each of the connecting pipes is controlled according to the measured fluid temperature to suppress the fluid temperature unbalance.

  ADVANTAGE OF THE INVENTION According to this invention, the imbalance of the furnace exit fluid temperature of a once-through boiler can be suppressed by replacing the right-and-left wall or front-and-back wall of the fluid in a heat exchanger tube which passes through each part of a furnace water wall.

  Moreover, by providing a water injection spray to the connecting pipe of the furnace intermediate mixing part for replacing the fluid in the heat transfer pipe passing through each part of the furnace wall, the imbalance of the furnace outlet fluid temperature can be suppressed more accurately, Furthermore, by controlling the spray water of the water injection spray in a boiler with a high steam temperature condition, it is possible to suppress the generation of thermal stress at the furnace outlet and prevent the furnace from being damaged.

It is a figure showing a schematic structure of a once-through boiler concerning an embodiment of the present invention, and a schematic system of boiler feed water. It is a systematic diagram of fluid in a heat exchanger tube from a economizer to a furnace exit in a once-through boiler concerning this embodiment. It is sectional drawing of the fluid system | strain in the furnace intermediate mixing part in the once-through boiler which concerns on this embodiment. It is a schematic side view of the intermediate mixing part regarding this embodiment. It is a figure which shows the fluid system | strain in the furnace intermediate mixing part regarding a prior art. It is explanatory drawing which shows the fluid system | strain in the furnace intermediate mixing part regarding another prior art. It is a side view which shows the fluid system | strain in the furnace intermediate mixing part regarding another prior art.

  The fluid flow flowing through the heat transfer tube and the fluid temperature adjustment in the once-through boiler according to the embodiment of the present invention will be described below with reference to FIGS. In the drawings, 1 is a boiler feed pump, 2 is a high-pressure feed heater, 3 is a boiler feed pipe, 4 is a economizer, 5 is a furnace (lower part), 6 is a furnace (upper part), 7 is a burner, and 8 is a superheater. , 9 is a reheater, 10 is a furnace intermediate mixing section, 11 is a economizer inlet header, 12 is a economizer outlet header, 13 is a furnace inlet precipitation pipe, 14 is a furnace inlet distribution manifold, and 15 is a furnace. Inlet distribution pipe, 16 is a furnace inlet header, 17 is a left lower wall of the furnace, 18 is a lower front wall of the furnace, 19 is a lower right wall of the furnace, 20 is a lower rear wall of the furnace, 21 is a lower outlet outlet header, and 22 is a furnace Lower outlet mixing device connection pipe, 23 is a furnace intermediate mixing device, 24 is a furnace intermediate connecting pipe, 25 is a furnace intermediate spray device, 26 is a furnace upper inlet distribution manifold, 27 is a furnace upper inlet distribution pipe, and 28 is a furnace upper inlet The header, 29 is the upper left wall of the furnace, 30 is the upper part of the furnace Wall 31 furnace top right side wall, 32 furnace upper rear wall, 33 denotes the furnace top outlet pipe pulling, respectively.

  In FIG. 1, feed water to a boiler is supplied from a boiler feed pump 1 through a high-pressure feed heater 2 through a boiler feed pipe 3 to a economizer 4 in the boiler. The feed water is heated by the furnace (lower part) 5, the furnace (upper part) 6, the superheater 8 and the like in which the burner 7 is installed, and is supplied to the high-pressure turbine as steam. The steam returned from the high-pressure turbine is heated by the reheater 9 and supplied to the intermediate-pressure turbine to generate power. Here, a furnace intermediate mixing unit 10 is installed between the furnace (lower part) 5 and the furnace (upper part) 6.

  2, 3 and 4, the feed water from the economizer 4 is sent to the furnace (lower part) 5 through the furnace inlet precipitation pipe 13 and the like, and the furnace lower front wall 18, the furnace lower rear wall 20, and the furnace lower left side The peripheral wall composed of the four heat transfer tubes of the wall 17 and the furnace lower right wall 19 is heated and raised by the combustion gas of the furnace. In the furnace intermediate mixing section 10, the fluid in the heat transfer tube is once taken out of the furnace at the furnace lower outlet header 21, and the furnace intermediate mixing device 23 installed beside the both side walls at the furnace lower outlet mixer connecting pipe 22. Collected and mixed.

  Next, the mixed fluid is sent to the left and right sides of the furnace through the furnace intermediate connecting pipe 24 (see FIG. 3). A furnace intermediate spray device 25 is installed in the middle of the connecting pipe 24, and the boiler feed pump Inject 1 outlet water supply. The fluid sent to the opposite side of the furnace is sent to the furnace upper inlet header 28 via the furnace upper inlet manifold 26 and the furnace inlet distribution pipe 27, and again comprises a heat transfer tube constituting the furnace (upper) 6. The four peripheral walls, that is, the furnace upper front wall 30, the furnace upper rear wall 32, the furnace upper left wall 29, and the furnace upper right wall 31 are heated and risen to become steam and reach the furnace outlet header 33. Although not shown, a temperature sensor for measuring the furnace outlet fluid temperature is provided on the output side of the furnace outlet header 33.

  Next, the detailed system of the flow of the fluid in the intermediate mixing part 10 is demonstrated using FIG. 2 and FIG. In the furnace intermediate mixing device 10 installed beside the both side walls of the boiler, the right mixing device 23-1 includes all of the furnace lower right wall 19 and the right side of each of the furnace lower front wall 18 and the furnace lower rear wall 20. Half of the fluid is collected, and the left mixing device 23-2 collects all of the lower left wall 17 of the furnace and the left half of each of the lower front wall 18 and the lower rear wall 20 of the furnace. In the mixing devices 23-1 and 23-2, the enthalpies of the fluid in the right half and the left half of the furnace are made uniform.

  Here, in the case where there is an imbalance in combustion before and after the boiler in the burner section 7, the front wall 18 and the rear wall 20 are mixed by the mixing devices 23-1 and 23-2, respectively. Therefore, the enthalpy difference between the front and rear fluids is eliminated.

  On the other hand, when the combustion imbalance has arisen on right and left, a difference will arise in the fluid enthalpy of the two mixing apparatuses 23-1 and 23-2. Therefore, the left and right sides of the mixed fluid are exchanged in the furnace intermediate connecting pipe 24, and the fluid heated in the right half of the lower part of the furnace (all of the right side wall, the right half of the front wall and the right half of the rear wall) Sent to the left half of the upper left wall 29 and the upper front wall 30 of the furnace and the left half of the upper rear wall 32 of the furnace, and the left half of the lower part of the furnace (the entire left wall, the left half of the front wall and the left half of the rear wall) The heated fluid is sent to the right half of the furnace upper right wall 31 and the furnace upper front wall 30 and the right half of the furnace upper rear wall 32, so that the fluid heated in the lower part of the furnace is completely left and right in the upper part. Will be replaced.

  Here, the unbalance of the combustion generated in the lower part of the furnace affects the wake side of the upper part of the furnace and the superheater as the unbalance of the front and rear and the left and right as it is. Therefore, even if there is a difference in the fluid enthalpy between the left and right mixing devices, the difference in the enthalpy of the furnace outlet fluid is mitigated by replacing the internal fluid in the heat transfer tube between the lower part and the upper part of the furnace. Even when the fluid in the pipe is a two-phase flow of water and steam, superheated steam, or supercritical pressure steam, temperature imbalance can be suppressed. This is the same even if a mixing device is arranged before and after the furnace.

  Also, in the furnace intermediate connecting pipe 24 connecting the furnace intermediate mixing device 23 and the furnace upper inlet distribution manifold 26, the feed water at the boiler feed pump outlet is injected by using the furnace intermediate spray device 25, thereby reducing the fluid enthalpy at the furnace outlet. By reducing, the fluid temperature imbalance can be suppressed. At that time, if a temperature difference occurs on the left and right at the furnace outlet, measure the temperature at the part corresponding to each outlet, and control each injection amount according to the temperature, so that the temperature difference is further reduced It can be effectively suppressed.

  Furthermore, by using spray water injection by the furnace intermediate spray device 25, the furnace outlet fluid temperature in the boiler with high steam temperature conditions is reduced, the generation of thermal stress at the furnace outlet is suppressed, and damage to the furnace is prevented. can do. In the above description, in the furnace intermediate mixing unit 10, the four inner walls (front wall, rear wall, right side wall, left side wall) of the furnace are divided into left and right, using the mixing means, the connecting pipe, and the distributing means. Although it has been described that the fluid in the heat transfer tube is replaced on the left and right, the same effect can be obtained even if the fluid in the heat transfer tube is replaced before and after the furnace.

  In this embodiment, the spray water that is poured into the middle of the furnace is branched from the outlet of the boiler feed pump 1 instead of the inlet or outlet of the economizer 4. The meaning of branching from the outlet of the pump 1 is that the pressure of the feed water is lowered when the boiler feed water passes through the high-pressure feed water heater 2, so the pressure difference with the furnace intermediate mixing section 10 is greater than the entrance or exit of the economizer. This is because the outlet of the boiler feed pump 1 becomes larger, and spraying of the spray can be easily performed.

  Further, in the high-pressure feed water heater 2 (see FIG. 1), the feed water is heated by the extracted steam of the turbine. Therefore, the feed water temperature at the outlet of the boiler feed pump 1 is lower than the inlet temperature of the economizer 4, and the spray water is heated. Is less than the economizer inlet or outlet, reducing the enthalpy of the fluid in the furnace intermediate mixing section 10, greatly reducing the furnace outlet fluid temperature, and being excellent in controllability.

  As described above, the features of the embodiment of the present invention will be described repeatedly. The fluid in the heat transfer tube heated and raised in the lower part of the furnace is uniformly distributed by 50% each by the two fluid mixing devices installed in the middle of the furnace. By connecting the fluid to the left and right or front and back opposite sides of the furnace with two connecting pipes and heating at the top of the furnace, the fluid temperature at the left and right or front and rear furnace outlets caused by combustion in the furnace Unbalance can be suppressed.

  Furthermore, when water is injected by the spray device in the two connecting pipes, the fluid temperature imbalance can be effectively suppressed by changing the water injection amount of the two connecting pipes according to the furnace outlet fluid temperature. Moreover, in the boiler of high steam temperature conditions, by controlling the spray water of the water injection spray, it is possible to reduce the furnace outlet fluid temperature and suppress the generation of thermal stress at the furnace outlet.

  In the once-through boiler, the spray water to the superheater branches off from the feed water at the inlet or outlet of the economizer, whereas the spray water into the connecting pipe in the middle of the furnace is at the inlet or outlet of the economizer. By using feed water branched from the boiler feed water pump outlet or the middle of multiple high-pressure feed water heaters, which can take a larger pressure difference from the fluid in the communication pipe and lower in temperature than the feed water, the amount of water injection and fluid temperature can be reduced. Can be spread. As a result, generation of thermal stress can be suppressed and damage to the furnace can be prevented by suppressing the fluid temperature imbalance and reducing the furnace outlet fluid temperature.

DESCRIPTION OF SYMBOLS 1 Boiler feed pump 2 High pressure feed water heater 3 Boiler feed pipe 4 Carbon-saving device 5 Furnace (lower part)
6 Furnace (upper part)
7 Burner 8 Superheater 9 Reheater 10 Furnace intermediate mixing section 11 Fuel saver inlet header 12 Fuel saver outlet header 13 Furnace inlet precipitation tube 14 Furnace inlet distribution pipe manifold 15 Furnace inlet distribution pipe 16 Furnace inlet header 17 Furnace lower left wall 18 Furnace lower front wall 19 Furnace lower right wall 20 Furnace lower rear wall 21 Furnace lower outlet header 22 Furnace lower outlet mixer connecting pipe 23 Furnace intermediate mixing device 24 Furnace intermediate connecting pipe 25 Furnace intermediate spray device 26 Furnace Upper inlet distribution manifold 27 Furnace upper inlet distribution pipe 28 Upper furnace inlet inlet 29 Upper furnace left wall 30 Upper furnace front wall 31 Upper furnace right wall 32 Upper furnace rear wall 33 Upper furnace outlet header 34 Upper divider wall 35 Furnace Peripheral wall header

Claims (5)

A furnace having an inner wall consisting of a front wall, a rear wall, a left side wall, and a right side wall; a heat transfer tube provided on the inner wall; and a burner provided at a lower portion of the furnace, wherein the fluid in the heat transfer tube In the once-through boiler that absorbs heat from the combustion gas in the furnace,
In the middle part of the furnace above the burner, four furnace lower outlet headers for bringing fluid in the heat transfer tubes corresponding to the inner walls are provided,
Two fluid mixing means for mixing fluids fed from the four furnace lower outlet headers are provided,
Two fluid distribution means for supplying the mixed fluid from the two fluid mixing means through respective connecting pipes;
Four furnace upper inlet headers to which fluid is fed from the two fluid distribution means are provided in the middle of the furnace,
The two fluid mixing means collect and mix the fluid from the bottom outlet outlets arranged at the left and right sides of the furnace for each left and right, and send the mixed fluid to the respective fluid distribution means through the respective connecting pipes. And
The two fluid distribution means form a fluid flow path for the four furnace upper inlet headers so that the fluid in the left and right heat transfer tubes of the furnace is exchanged between the lower and upper parts of the furnace. A once-through boiler. In claim 1,
A furnace in which the two fluid mixing means are arranged in front of and behind the furnace instead of collecting and mixing the fluid from the bottom outlet outlet of the furnace in which the two fluid mixing means are arranged on the left and right of the furnace, respectively. The fluid from the lower outlet header is collected and mixed on the front and back sides, and the two fluid distribution means are arranged so that the fluid in the heat transfer tubes before and after the furnace is exchanged between the lower part and the upper part of the furnace. A once-through boiler characterized in that a fluid flow path is formed with respect to a furnace upper inlet header. In claim 1 or 2,
A once-through boiler, wherein a spray device for injecting water from an outlet of a boiler feed water pump or water branched from between a plurality of high-pressure feed water heaters is provided in the connecting pipe. In claim 3,
A once-through boiler, wherein a fluid temperature at a furnace outlet is measured, and an unbalance of the fluid temperature is suppressed by controlling a water injection amount to each of the connecting pipes according to the measured fluid temperature. In claim 3,
It measures the fluid temperature at the furnace outlet in a boiler with high steam temperature conditions, and controls the amount of water injected into each of the connecting pipes according to the measured fluid temperature to reduce the fluid temperature at the furnace outlet. Once-through boiler.

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