Boiler steam-water circulation system

Abstract

The invention 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] The present application relates to the technical field of boiler steam-water circulation, and in particular to a boiler steam-water circulation system. Background Art

[0002] As the core equipment of thermal power plants, steam boilers primarily absorb the heat energy released by the combustion of fuels (such as coal and oil) through the working medium water, evaporating the water into high-temperature, high-pressure steam to drive turbine generators for electricity production. This equipment is widely used in the energy industry. Boilers primarily consist of key components such as the water-cooled heating surface of the combustion chamber, a superheater, and an economizer.

[0003] With the rapid development of the power industry, boiler steam parameters have continued to rise, evolving from subcritical (steam pressure below 21.4 MPa) to supercritical and even ultra-supercritical (main steam pressure exceeding 28 MPa). This has led to a corresponding increase in boiler feedwater temperature, which can cause water vaporization in economizers under certain complex operating conditions. If the boiler design is flawed, this vaporization can easily lead to internal vaporization blockage within the economizer. A clogged economizer heating surface, exposed to high temperatures, can experience a sharp increase in wall temperature, causing irreversible expansion and deformation, and in severe cases, even leading to economizer tube bursts. Summary of the Invention

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

[0005] The embodiment of the present application provides a boiler steam-water circulation system, which includes a water supply device, an economizer, a water-cooled wall, and a steam-water separator. The water supply device includes a water supply pipe for providing water, and the water supply pipe includes 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 water 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. By providing the ascending pipe of the water supply 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. At the same time, by adding the steam outlet of the steam-water separator, the natural circulation effect of the water system is enhanced to prevent or alleviate the vaporization blockage phenomenon in the economizer, making the economizer safer and more efficient.

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

[0007] In one embodiment, 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 ascending pipe and the highest point of the descending pipe, the second connecting pipe includes a horizontal section and an ascending section, the horizontal section is connected between the lowest point of the descending pipe and the lowest point of the ascending section, the ascending section is connected to the inlet of the economizer and provides an ascending 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 the water outlet of the steam-water separator and the water supply pipe, respectively, and is configured to supply water with a preset flow potential energy to the water supply pipe. By connecting the water outlet to the water supply pipe, the water separated by the steam-water separator is re-introduced into the water supply pipe. Simultaneously, the water supply pump supplies water with a preset flow potential energy to the water supply pipe under pressure, thereby re-establishing a water circulation.

[0009] In one embodiment, the system further comprises a steam venting line for the economizer, wherein the steam venting line is connected between the outlet of the economizer and the steam-water separator, and is used for introducing the steam at the outlet of the economizer into the steam-water separator.

[0010] In one embodiment, a steam bleed valve is provided in the steam bleed line, and the bleed valve is used to control the opening, closing, and / or switching degree of the steam bleed line. In this embodiment, the steam bleed line is connected to the steam-water separator. By providing the steam bleed line and the bleed valve between the economizer outlet and the steam-water separator, excess steam generated in the economizer can be promptly discharged under low boiler load conditions to prevent steam lock.

[0011] In one embodiment, the system further includes a superheater, which is connected to the steam outlet of the steam-water separator and is used to cool the steam in the steam-water separator before discharging it.

[0012] In one embodiment, the steam outlet of the steam-water separator is connected to the inlet of the superheater via a downpipe, and the steam is discharged from the superheater outlet via an uppipe. In this embodiment, the separated steam enters the superheater through the downpipe at the steam outlet of the steam-water separator, is further heated to the desired parameters, and is finally introduced into the steam turbine through the uppipe at the superheater outlet to generate electricity, completing the entire thermodynamic cycle.

[0013] In one embodiment, the inlet of the water-cooled wall is provided with a water-cooled wall lower header; the outlet of the water-cooled wall is provided with a water-cooled wall upper 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 water 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 re-injected into the recirculation pump and then enters the water supply pipe, thereby forming a water cycle again. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

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

[0017] Figure 2 This is a schematic diagram of parallel pipes in a boiler steam-water circulation system of the present application;

[0018] Figure 3 This is a schematic diagram of the natural circulation principle of steam and water in a boiler steam and water circulation system of the present application. DETAILED DESCRIPTION

[0019] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present 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 comprehensive understanding of the disclosure of the present application.

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

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] See also Figure 1 As shown, an embodiment of the present 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 providing water, and the water supply pipe 11 includes 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, and the water outlet 42a of the steam-water separator 4 is connected to the water supply device 1 to form a water circulation. The steam outlet 42b of the steam-water separator 4 is used to discharge steam.

[0023] It can be understood that the boiler body 200 in the prior art usually includes structures such as an economizer 2 and a water-cooled wall 3. When a high-parameter boiler is operating at low load, the pressure of the feed water pump can be as low as 10 MPa or even lower, which is far less than the pressure requirement for the working medium (water) to reach a supercritical state. This causes the water to vaporize after being heated to a certain temperature. In addition, since the heat released by combustion is small and the amount of steam generated is low when the boiler is operating at low load, the water flow rate in the economizer is greatly reduced, causing the water to be overheated in the economizer. At the same time, due to the reduction in pressure level, the boiling point of water becomes lower. These factors combine to cause a large amount of vaporization of the water in the economizer. The vaporized steam has low density and large volume, occupying the upper space of the economizer, which may cause a "steam plug" phenomenon, resulting in an increase in the flow deviation between the parallel tube groups of the economizer. At this point, the steam within some of the economizer tube groups is stagnant or flowing slowly. It continues to be heated by the flue gas, further increasing its temperature. This can lead to large horizontal temperature differences and uneven expansion across the economizer's parallel tube groups, potentially causing tube bursts and other accidents. In this embodiment, water flows into the economizer 2 from the inlet 21 via the water supply device 1. The water within the economizer 2 absorbs heat from the flue gas, lowering its temperature. The heated water collects at the outlet 22 of the economizer 2 and flows through it to the water-cooled wall 3. The water then enters the water-cooled wall 3, absorbing heat from the high-temperature flue gas and evaporating, producing a large amount of steam. The steam-water mixture exits the outlet 32 ​​of the water-cooled wall 3 and enters the steam-water separator 4 for separation. The separated steam is discharged through the steam outlet 42b of the steam-water separator 4. The separated water then connects to the water supply device 1 through the water outlet 42a of the steam-water separator 4, completing the water cycle and undergoing the heating, evaporation, and heating process again. By providing the ascending pipe 11a of the water supply pipe 11 and the descending pipe 11b connected to the ascending pipe 11a, the water flow in the descending section of the descending pipe 11b is utilized 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 having an economizer 2 structure, regardless of the boiler type.

[0024] Furthermore, the height of the inlet 21 of the economizer 2 is lower than the maximum height D2 of the ascending pipe 11a; the height D1 of the outlet 22 of the economizer 2 is lower than the maximum height D2 of the ascending 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; the lowest 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 ascending pipe 11a and the highest point of the descending pipe 11b, the second connecting pipe 11d includes a horizontal section 11e and an ascending section 11f, the horizontal section 11e is connected between the lowest point of the descending pipe 11b and the lowest point of the ascending section 11f, the ascending section 11f is connected to the inlet 21 of the economizer 2 and provides an ascending 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, but first extends upward through the ascending pipe 11a to a height D1 exceeding the outlet 22 of the economizer 2, and then descends through the descending pipe 11b. After being buffered by the horizontal section 11e of the second connecting pipe 11d, it is connected to the inlet 21 of the economizer 2 through the ascending section 11f of the second connecting pipe 11d. By utilizing the more uniform water flow characteristics in the descending pipe 11b, the horizontal section 11e and the ascending section 11f, the input water flow of the economizer 2 is optimized, the vortex phenomenon that may exist in the high-speed water flow is reduced, and it is more conducive to the uniform distribution of the fluid at the inlet 21 of the economizer 2.

[0027] Furthermore, the water supply device 1 further includes a water supply pump 12, which is respectively connected to the water outlet 42a of the steam-water separator 4 and the water supply pipe 11, and is used to provide water with a preset flow potential energy to the water supply pipe 11. In this embodiment, the water outlet 42a of the steam-water separator 4 is directly connected to the water supply pipe 11. By connecting the water outlet 42a with the water supply pipe 11, the water separated by the steam-water separator 4 is re-input 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, thereby forming a water circulation again.

[0028] Furthermore, the system 100 also includes a steam venting line 5 for the economizer 2. The steam venting line 5 is connected between the outlet 22 of the economizer 2 and the steam-water separator 4 and is used to guide the steam at the outlet 22 of the economizer 2 into the steam-water separator 4. The addition of the steam venting line 5 for the economizer 2 enhances the natural circulation effect of the water system, thereby preventing or reducing vaporization blockage in the economizer 2.

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

[0030] Furthermore, the system 100 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 discharging it. The steam outlet 42b of the steam-water separator 4 is connected to the inlet 61 of the superheater 6 via a downcomer 42c, and the outlet 62 of the superheater 6 discharges the steam via 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 desired parameters, and is ultimately introduced into the steam turbine through the upcomer 62a of the outlet 62 of the superheater 6 to generate electricity, completing the entire thermodynamic cycle.

[0031] Furthermore, the inlet 31 of the water-cooled wall 3 is provided with a lower header 31a of the water-cooled wall 3; the outlet 32 ​​of the water-cooled wall 3 is provided with an upper header 31b of the water-cooled wall 3; the inlet 21 of the economizer 2 is provided with an economizer 2 inlet header 21a; and the outlet 22 of the economizer 2 is provided with an economizer 2 outlet header 21b. It can be understood that the boiler main feed water enters the inlet header 21a of the economizer 2 through the feed water pipe 11 and then flows into the economizer 2. The heated water is collected in the outlet header 21b of the economizer 2 and flows through the pipe at the economizer 2 outlet 22 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 the heat of the high-temperature flue gas, and evaporates, generating a large amount of steam. The steam-water mixture is then 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 downpipe 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 uppipe 62a of the outlet 62 of the superheater 6, completing the entire thermodynamic cycle.

[0032] Furthermore, the system 100 includes a recirculation pump 7, which is connected between the water outlet 42a of the steam-water separator 4 and the water supply device 1 to maintain water circulation in the system 100. The recirculation pump 7 allows the water separated by the steam-water separator 4 to be re-injected into the recirculation pump 7 and then enter the water supply pipe 11, thus re-circulating the water. It should be noted that if this embodiment is used on a boiler that does not already have a recirculation pump 7, it is generally necessary to add the recirculation pump 7. If it is used on a boiler that already has a recirculation pump 7, it is generally necessary to recalculate the pressure, thermal parameters, and other parameters of the boiler steam-water system to determine the required recirculation pressure. Based on the calculation results, a new appropriate recirculation pump 7 may be selected. In this embodiment, the water separated in the steam-water separator 4 is returned to the water supply device 1 via the recirculation pump 7, undergoing the heating, evaporation, and heating processes again. The function of the recirculation pump 7 is to maintain the natural circulation characteristics of the parallel pipes. According to thermodynamic principles, pipes that are heated more strongly produce more steam, which reduces the density of the steam and water, decreases flow resistance, and increases the effective pressure head, ultimately increasing flow rate and reducing pipe wall temperature. This phenomenon is known in the industry as the self-compensation capacity of natural circulation.

[0033] In order to understand the principle of natural circulation of soda water involved in this application, please refer to Figure 3 As shown, the steam-water separator 4, the economizer 2 and the water-cooled wall 3 form a natural circulation system 100 of steam and water. The present application integrates the advantages of ultra-supercritical steam-water forced circulation and subcritical water natural circulation under different loads and different steam pressures. The present application optimizes the flow pattern of the water flow at the inlet 21 of the economizer 2 by introducing the structural design of the rising pipe 11a and the descending pipe 11b of the water supply pipe 11, aiming to reduce the vortex 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 in 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 medium (water) on the heating surface of the supercritical economizer 2, so that the boiler can make full use of natural circulation and forced circulation under different pressure conditions to improve the water circulation quality, thereby avoiding the above-mentioned possible accidents.

[0034] The technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above-described embodiments only express several implementation methods of the present application, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all fall within the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.

Claims

1. A boiler steam-water circulation system, characterized in that: The boiler steam-water circulation system comprises: A water supply device, comprising a water supply pipe for providing water, wherein the water supply pipe comprises an ascending pipe and a descending pipe communicating with the ascending pipe; an economizer, wherein the inlet of the economizer is connected to the downcomer; a water-cooled wall, an inlet of the water-cooled wall being in communication with an 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 water 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 inlet height of the economizer is lower than the highest height of the rising pipe; The outlet height of the economizer is lower than the highest height of the rising pipe; The inlet height of the economizer is lower than the outlet height of the economizer; The lowest height of the downcomer 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 ascending pipe and the highest point of the descending pipe, the second connecting pipe includes a horizontal section and an ascending section, the horizontal section is connected between the lowest point of the descending pipe and the lowest point of the ascending section, the ascending section is connected to the inlet of the economizer and provides an ascending 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 further comprises a water supply pump, which is respectively connected to the water outlet of the steam-water separator and the water supply pipe, and is used for providing water with 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 further comprises a steam venting pipeline of the economizer, wherein the steam venting pipeline is connected between the outlet of the economizer and the steam-water separator and is used for introducing the steam at 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 release pipeline is provided with a steam release valve, and the steam release valve is used to control the opening, closing and / or switching degree of the steam release pipeline.

7. The boiler steam-water circulation system according to claim 1, characterized in that: The system further comprises a superheater, which is communicated with the steam outlet of the steam-water separator and is used for cooling the steam in the steam-water separator before discharging it.

8. The boiler steam-water circulation system according to claim 1, characterized in that: The steam outlet of the steam-water separator is connected to the inlet of the superheater through a downpipe, and the outlet of the superheater discharges the steam through an uppipe.

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 water-cooled wall lower header; the outlet of the water-cooled wall is provided with a water-cooled wall upper header: The inlet of the economizer is provided with an economizer inlet header; the outlet of the economizer is provided with an economizer outlet header.

10. The boiler steam-water circulation system according to claim 1, characterized in that: The system further comprises a recirculation pump, which is connected between the water outlet of the steam-water separator and the water supply device and is used to maintain water circulation in the system.

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