Boiler steam-water circulation system

Abstract

The utility model provides a boiler steam-water circulation system. The boiler steam-water circulation system comprises a water supply device, an economizer, a water cooling wall and a steam-water separator. The water supply device comprises a water supply pipe for providing water, and the water supply pipe comprises an ascending pipeline and a descending pipeline communicated with the ascending pipeline; an inlet of the coal economizer is communicated with the descending pipeline; an inlet of the water cooling wall is communicated with an outlet of the coal economizer; an inlet of the steam-water separator is communicated with an outlet of the water cooling wall, a water outlet of the steam-water separator is communicated with the water supply device to form water circulation, and a steam outlet of the steam-water separator is used for discharging steam. By arranging the ascending pipeline and the descending pipeline, the water flow quality in the heating surface of the economizer is enhanced by utilizing the water flow of the descending section of the descending pipeline.

Description

Technical Field

[0001] This application relates to the field of boiler steam-water circulation technology, and in particular to a boiler steam-water circulation system. Background Technology

[0002] Steam boilers, as core equipment in thermal power plants, primarily function to absorb the heat energy released from the combustion of fuels (such as coal and oil) through a working fluid called water, thereby evaporating the water into high-temperature, high-pressure steam to drive a steam turbine generator for electricity production. This equipment is widely used in the energy industry. A boiler mainly consists of key components such as the water-cooled wall heating surfaces that form the combustion chamber, a superheater, and an economizer.

[0003] With the rapid development of the power industry, boiler steam parameters have continuously improved, gradually evolving from subcritical (steam pressure below 21.4 MPa) to supercritical and even ultra-supercritical (main steam pressure exceeding 28 MPa). The boiler feedwater temperature has also increased accordingly, leading to vaporization of water in the economizer under certain complex operating conditions. If there are design flaws in the boiler, this vaporization can easily cause blockage inside the economizer. In a high-temperature environment, the wall temperature of the blocked economizer heating surface will rise sharply, causing irreversible expansion and deformation, which in severe cases can even lead to economizer tube rupture. Utility Model Content

[0004] Therefore, it is necessary to provide a boiler steam-water circulation system that can mitigate or avoid the problem of blockage caused by excessive vaporization of the working fluid (water) on the heating surface of the supercritical economizer.

[0005] This application provides a boiler steam-water circulation system, which includes a feedwater device, an economizer, a water-cooled wall, and a steam-water separator. The feedwater device includes a feedwater pipe for supplying water, comprising an ascending pipe and a descending pipe connected to the ascending pipe; the inlet of the economizer is connected to the descending pipe; the inlet of the water-cooled wall is connected to the outlet of the economizer; the inlet of the steam-water separator is connected to the outlet of the water-cooled wall, and the outlet of the steam-water separator is connected to the feedwater device to form a water circulation; the steam outlet of the steam-water separator is used to discharge steam. By configuring the ascending pipe of the feedwater pipe and the descending pipe connected to the ascending pipe, the water flow in the descending section of the descending pipe is utilized to enhance the water flow quality in the heating surface of the economizer.

[0006] In one embodiment, the inlet height of the economizer is lower than the maximum height of the rising pipe; the outlet height of the economizer is lower than the maximum height of the rising pipe; the inlet height of the economizer is lower than the outlet height of the economizer; and the minimum height of the descending pipe is lower than the inlet height of the economizer.

[0007] In one embodiment, the water supply pipe further includes a first connecting pipe and a second connecting pipe. The first connecting pipe is horizontally connected between the highest point of the rising pipe and the highest point of the falling pipe. The second connecting pipe includes a horizontal section and a rising section. The horizontal section is connected between the lowest point of the falling pipe and the lowest point of the rising section. The rising section is connected to the inlet of the economizer and provides an upward water path to the inlet of the economizer.

[0008] In one embodiment, the water supply device further includes a water supply pump, which is connected to both the outlet of the steam-water separator and the water supply pipe, for supplying water with a preset flow potential energy to the water supply pipe. By connecting the outlet to the water supply pipe, the water separated by the steam-water separator is reintroduced into the water supply pipe, and simultaneously, under pressure from the water supply pump, water with a preset flow potential energy is supplied to the water supply pipe, thus forming a water circulation cycle again.

[0009] In one embodiment, the system further includes a steam venting pipeline for the economizer, the steam venting pipeline being connected between the outlet of the economizer and the steam-water separator, for introducing steam from the outlet of the economizer into the steam-water separator.

[0010] In one embodiment, a steam venting valve is provided in the steam venting pipeline, which is used to control the opening, closing, and / or on / off degree of the steam venting pipeline. In this embodiment, the steam venting pipeline is connected to the steam-water separator. By providing the steam venting pipeline and the steam venting valve between the economizer outlet and the steam-water separator, excess steam generated in the economizer can be discharged in a timely manner under low boiler load conditions, preventing steam blockage.

[0011] In one embodiment, the system further includes a superheater connected to the steam outlet of the steam-water separator for cooling the steam from the steam-water separator before discharge.

[0012] In one embodiment, the steam outlet of the steam-water separator is connected to the inlet of the superheater via a downcomer, and the steam is discharged from the outlet of the superheater via a riser. In this embodiment, the separated steam enters the superheater through the downcomer at the steam outlet of the steam-water separator, is further heated to the required parameters, and is finally introduced into the turbine for power generation through the riser at the outlet of the superheater, completing the entire thermodynamic cycle.

[0013] In one embodiment, the inlet of the water-cooled wall is provided with a lower water-cooled wall header; the outlet of the water-cooled wall is provided with an upper water-cooled wall header; the inlet of the economizer is provided with an economizer inlet header; and the outlet of the economizer is provided with an economizer outlet header.

[0014] In one embodiment, the system further includes a recirculation pump connected between the outlet of the steam-water separator and the water supply device to maintain water circulation in the system. By providing the recirculation pump, the water separated by the steam-water separator is reintroduced into the recirculation pump and then into the water supply pipe, thus forming a water circulation again. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the planar structure of a boiler steam-water circulation system according to this application;

[0017] Figure 2 This is a schematic diagram of parallel piping in a boiler steam-water circulation system according to this application;

[0018] Figure 3 This is a schematic diagram of the natural circulation principle of a boiler steam-water circulation system according to this application. Detailed Implementation

[0019] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0020] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "inner," "outer," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Please see Figure 1 As shown in the figure, this application provides a boiler steam-water circulation system 100, which includes a water supply device 1, an economizer 2, a water-cooled wall 3, and a steam-water separator 4. The water supply device 1 includes a water supply pipe 11 for supplying water, the water supply pipe 11 including an ascending pipe 11a and a descending pipe 11b connected to the ascending pipe 11a; the inlet 21 of the economizer 2 is connected to the descending pipe 11b; the inlet 31 of the water-cooled wall 3 is connected to the outlet 22 of the economizer 2; the inlet 41 of the steam-water separator 4 is connected to the outlet 32 ​​of the water-cooled wall 3, the outlet 42a of the steam-water separator 4 is connected to the water supply device 1 to form a water circulation, and the steam outlet 42b of the steam-water separator 4 is used to discharge steam.

[0023] It is understandable that the existing boiler body 200 typically includes structures such as an economizer 2 and a water-cooled wall 3. Under low-load operation, the pressure of the feedwater pump in a high-parameter boiler can be as low as 10 MPa or even lower, which is far below the pressure required for the working fluid (water) to reach the supercritical state. This causes the water to vaporize after being heated to a certain temperature. In addition, because the boiler releases less heat and produces less steam when operating at low load, the water flow velocity in the economizer is greatly reduced, causing the water to be overheated in the economizer. At the same time, due to the reduced pressure level, the boiling point of water becomes lower. These factors combined cause a large amount of water in the economizer to vaporize. The vaporized steam has low density and large volume, occupying the upper space of the economizer, which may cause a "steam blockage" phenomenon, resulting in an increase in the flow deviation between the parallel pipe groups of the economizer. At this time, the steam in some tube groups of the economizer is in a state of no flow or slow flow, and continues to be heated by the flue gas, causing the temperature to rise further. This leads to excessive temperature difference and uneven expansion in the horizontal direction of the parallel tube groups of the economizer, which may eventually cause accidents such as tube rupture. In this embodiment, water flows into the economizer 2 from the inlet 21 through the water supply device 1. The water inside the economizer 2 absorbs heat from the flue gas and reduces the flue gas temperature. The heated water collects at the outlet 22 of the economizer 2 and flows to the water-cooled wall 3 through the outlet 22. Subsequently, the water enters the water-cooled wall 3, absorbs heat from the high-temperature flue gas and evaporates, generating a large amount of steam. The steam-water mixture is led out from the outlet 32 ​​of the water-cooled wall 3 and enters the steam-water separator 4 for steam-water separation. The separated steam is discharged through the steam outlet 42b of the steam-water separator 4, and the separated water is connected to the water supply device 1 through the water outlet 42a of the steam-water separator 4 to form a water circulation, and re-undergoes the heating, evaporation and heating processes. By configuring the rising pipe 11a of the feedwater pipe 11 and the descending pipe 11b connected to the rising pipe 11a, the water flow in the descending section of the descending pipe 11b is used to enhance the water flow quality in the heating surface of the economizer 2. Furthermore, this embodiment is applicable to all subcritical, supercritical, and ultra-supercritical boilers with an economizer 2 structure, and is not limited by boiler type.

[0024] Furthermore, the height of the inlet 21 of the economizer 2 is lower than the maximum height D2 of the rising pipe 11a; the height D1 of the outlet 22 of the economizer 2 is lower than the maximum height D2 of the rising pipe 11a; the height of the inlet 21 of the economizer 2 is lower than the height D1 of the outlet 22 of the economizer 2; and the minimum height of the descending pipe 11b is lower than the height of the inlet 21 of the economizer 2.

[0025] Furthermore, the water supply pipe 11 also includes a first connecting pipe 11c and a second connecting pipe 11d. The first connecting pipe 11c is horizontally connected between the highest point of the rising pipe 11a and the highest point of the falling pipe 11b. The second connecting pipe 11d includes a horizontal section 11e and a rising section 11f. The horizontal section 11e is connected between the lowest point of the falling pipe 11b and the lowest point of the rising section 11f. The rising section 11f is connected to the inlet 21 of the economizer 2 and provides an upward water path to the inlet 21 of the economizer 2.

[0026] In this embodiment, the water supply pipe 11 is not directly connected to the inlet 21 of the economizer 2 located at a lower position of the boiler. Instead, it first extends upward through the rising pipe 11a to a height D1 exceeding the outlet 22 of the economizer 2, then descends through the falling pipe 11b, and after being buffered by the horizontal section 11e of the second connecting pipe 11d, it connects to the inlet 21 of the economizer 2 through the rising section 11f of the second connecting pipe 11d. By utilizing the more uniform water flow characteristics of the falling pipe 11b, the horizontal section 11e, and the rising section 11f, the input water flow of the economizer 2 is optimized, reducing the eddy current phenomenon that may exist in the high-speed water flow, and making it more conducive to the uniform distribution of fluid at the inlet 21 of the economizer 2.

[0027] Furthermore, the water supply device 1 also includes a water supply pump 12, which is connected to the outlet 42a of the steam-water separator 4 and the water supply pipe 11, respectively, for supplying water with a preset flow potential energy to the water supply pipe 11. In this embodiment, the outlet 42a of the steam-water separator 4 is directly connected to the water supply pipe 11. By connecting the outlet 42a to the water supply pipe 11, the water separated by the steam-water separator 4 is reintroduced into the water supply pipe 11. At the same time, under the pressure of the water supply pump 12, water with a preset flow potential energy is supplied to the water supply pipe 11, thus forming a water circulation again.

[0028] Furthermore, the system 100 also includes a steam venting pipe 5 for the economizer 2, which connects the outlet 22 of the economizer 2 and the steam-water separator 4, for introducing steam from the outlet 22 of the economizer 2 into the steam-water separator 4. By adding the steam venting pipe 5 to the economizer 2, the natural circulation effect of the water system is enhanced, thereby preventing or mitigating vaporization blockage in the economizer 2.

[0029] Furthermore, a steam venting valve 51 is provided in the steam venting pipeline 5. The steam venting valve 51 is used to control the opening, closing, and / or switching degree of the steam venting pipeline 5. In this embodiment, the steam venting pipeline 5 is connected to the steam-water separator 4. By providing the steam venting pipeline 5 and the steam venting valve 51 between the outlet 22 of the economizer 2 and the steam-water separator 4, excess steam generated in the economizer 2 can be discharged in a timely manner under low boiler load conditions to prevent steam blockage. At the same time, when the steam venting valve 51 controls the steam venting pipeline 5 to be in the open state, it can also form... Figure 2 The parallel pipes shown can discharge excess steam generated in the economizer 2 in a timely manner to prevent steam blockage.

[0030] Furthermore, the system 100 also includes a superheater 6, which is connected to the steam outlet 42b of the steam-water separator 4, and is used to cool the steam from the steam-water separator 4 before discharge. The steam outlet 42b of the steam-water separator 4 is connected to the inlet 61 of the superheater 6 through a downcomer 42c, and the steam is discharged from the outlet 62 of the superheater 6 through an upcomer 62a. In this embodiment, the separated steam enters the superheater 6 through the downcomer 42c of the steam outlet 42b of the steam-water separator 4, is further heated to the required parameters, and is finally introduced into the steam turbine for power generation through the upcomer 62a of the outlet 62 of the superheater 6, completing the entire thermodynamic cycle.

[0031] Furthermore, the inlet 31 of the water-cooled wall 3 is provided with a lower header 31a; the outlet 32 ​​of the water-cooled wall 3 is provided with an upper header 31b; the inlet 21 of the economizer 2 is provided with an inlet header 21a; and the outlet 22 of the economizer 2 is provided with an outlet header 21b. It can be understood that the boiler main feedwater enters the inlet header 21a of the economizer 2 through the feedwater pipe 11, and then flows into the economizer 2. The heated water collects in the outlet header 21b of the economizer 2 and flows through the pipe at the outlet 22 of the economizer 2 to the lower header 31a of the water-cooled wall 3. Subsequently, the water enters the heating surface of the water-cooled wall 3 in the furnace, absorbs heat from the high-temperature flue gas, and evaporates to generate a large amount of steam. The steam-water mixture is drawn out from the upper header 31b of the water-cooled wall 3 and enters the steam-water separator 4 for steam-water separation. The separated steam enters the superheater 6 through the downcomer pipe 42c of the steam outlet 42b of the steam-water separator 4, where it is further heated to the required parameters. Finally, it is introduced into the steam turbine for power generation through the upcomer pipe 62a of the outlet 62 of the superheater 6, completing the entire thermodynamic cycle.

[0032] Furthermore, the system 100 also includes a recirculation pump 7, which is connected between the outlet 42a of the steam-water separator 4 and the water supply device 1, for maintaining the water circulation of the system 100. By setting the recirculation pump 7, the water separated by the steam-water separator 4 is reintroduced into the recirculation pump 7, thereby entering the water supply pipe 11 and forming a water circulation again. It should be noted that if this embodiment is used on a boiler that does not already have a recirculation pump 7, it is usually necessary to add the recirculation pump 7; if it is used on a boiler that already has a recirculation pump 7, it is usually necessary to recalculate the pressure, heat, and other parameters of the boiler steam-water system to determine the required recirculation pressure, and based on the calculation results, it may be necessary to reselect a suitable recirculation pump 7. In this embodiment, the water separated in the steam-water separator 4 is returned to the water supply device 1 through the recirculation pump 7, and undergoes heating, evaporation, and reheating processes again. The function of the recirculation pump 7 is to maintain the natural circulation characteristics of the parallel pipeline. According to thermodynamic principles, a pipe that is heated more will produce more steam, leading to a decrease in steam-water density, reduced flow resistance, and an increase in the effective head of the flow. This ultimately increases the flow rate and lowers the pipe wall temperature. This phenomenon is known in the industry as the self-compensating ability of natural circulation.

[0033] To facilitate understanding of the natural circulation principle of soft drinks involved in this application, please refer to [reference needed]. Figure 3 As shown, the steam-water separator 4, the economizer 2, and the water-cooled wall 3 form a natural steam-water circulation system 100. This application integrates the advantages of ultra-supercritical steam-water forced circulation and subcritical water-water natural circulation under different loads and steam pressures. By introducing the structural design of the rising pipe 11a and the falling pipe 11b of the feedwater pipe 11, this application optimizes the flow pattern of the water flow at the inlet 21 of the economizer 2, aiming to reduce the eddy current effect and improve the water flow distribution in the header 21a of the inlet 21 of the economizer 2. At the same time, by adding the steam venting pipe 5 at the end of the economizer 2, a natural circulation mechanism is constructed within the water system 100 to increase the water or steam-water flow rate in the heating surface of the supercritical boiler economizer 2, thereby reducing or avoiding the blockage problem caused by excessive vaporization of the working fluid (water) in the heating surface of the supercritical economizer 2. This allows the boiler to make full use of natural circulation and forced circulation under different pressure conditions to improve the water circulation quality and avoid the aforementioned possible accidents.

[0034] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The embodiments described above only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the utility model patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A boiler steam-water circulation system, characterized in that, The boiler steam-water circulation system includes: A water supply device includes a water supply pipe for supplying water, the water supply pipe including an ascending pipe and a descending pipe communicating with the ascending pipe; An economizer, wherein the inlet of the economizer is connected to the descending pipe, and the inlet height of the economizer is lower than the maximum height of the ascending pipe or the outlet height of the economizer is lower than the maximum height of the ascending pipe; A water-cooled wall, the inlet of which is connected to the outlet of the economizer; and A steam-water separator, wherein the inlet of the steam-water separator is connected to the outlet of the water-cooled wall, the outlet of the steam-water separator is connected to the water supply device to form a water circulation, and the steam outlet of the steam-water separator is used to discharge steam.

2. The boiler steam-water circulation system according to claim 1, characterized in that, The economizer inlet height is lower than the economizer outlet height; and / or The minimum height of the descending pipe is lower than the inlet height of the economizer.

3. The boiler steam-water circulation system according to claim 1, characterized in that, The water supply pipe also includes a first connecting pipe and a second connecting pipe. The first connecting pipe is horizontally connected between the highest point of the rising pipe and the highest point of the falling pipe. The second connecting pipe includes a horizontal section and a rising section. The horizontal section is connected between the lowest point of the falling pipe and the lowest point of the rising section. The rising section is connected to the inlet of the economizer and provides an upward water path to the inlet of the economizer.

4. The boiler steam-water circulation system according to claim 1, characterized in that, The water supply device also includes a water supply pump, which is connected to the outlet of the steam-water separator and the water supply pipe, respectively, and is used to supply water with a preset flow potential energy to the water supply pipe.

5. The boiler steam-water circulation system according to claim 1, characterized in that, The system also includes a steam venting pipeline for the economizer, which is connected between the outlet of the economizer and the steam-water separator, for introducing the steam from the outlet of the economizer into the steam-water separator.

6. The boiler steam-water circulation system according to claim 5, characterized in that, The steam venting pipeline is equipped with a steam venting valve, which is used to control the opening, closing and / or switching degree of the steam venting pipeline.

7. The boiler steam-water circulation system according to claim 1, characterized in that, The system also includes a superheater, which is connected to the steam outlet of the steam-water separator and is used to cool the steam from the steam-water separator before discharging it.

8. The boiler steam-water circulation system according to claim 7, characterized in that, The steam outlet of the steam-water separator is connected to the inlet of the superheater via a downcomer, and the steam is discharged from the outlet of the superheater via an upcomer.

9. The boiler steam-water circulation system according to claim 1, characterized in that, The inlet of the water-cooled wall is provided with a lower water-cooled wall header; the outlet of the water-cooled wall is provided with an upper water-cooled wall header. The economizer is equipped with an economizer inlet header and an economizer outlet header.

10. The boiler steam-water circulation system according to claim 1, characterized in that, The system also includes a recirculation pump connected between the outlet of the steam-water separator and the water supply device to maintain water circulation in the system.

Images