Device and method for stress control of thick-walled components of rapidly variable load boilers

Abstract

The present invention relates to a device and method for stress control of thick-walled components of a rapidly changing load boiler. The device includes a working fluid inlet pipe, a first header, a header branch pipe, a second header, and a working fluid outlet pipe; the working fluid inlet pipe is connected to the first header to input an external working fluid whose temperature rises or falls synchronously with the internal working fluid of the thick-walled component into the first header; the first header and the second header respectively surround the two ends of the thick-walled component, and each of the header branches is connected from each outlet of the first header to each inlet of the second header; the first header, the header branch pipe, and the second header are all attached to the outer wall surface of the thick-walled component, so that when the temperature of the internal working fluid of the thick-walled component changes, the external working fluid indirectly heats or cools the outer wall surface of the thick-walled component through heat exchange. The device can reduce the stress level of the thick-walled component during rapid load changes and extend the service life of the thick-walled component.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-fired power generation, and in particular to a device and method for regulating stress of thick-walled components of a rapid load-changing boiler. Background Art

[0002] my country's future energy consumption growth will primarily come from clean energy. However, renewable energy sources, primarily wind and solar, have the drawbacks of randomness and intermittency. To fully absorb these new energy sources, an increasing number of thermal power units are frequently participating in peak-shaving operations. Peak-shaving operations require boilers to have high load-variation rates. Unlike steady-state operations, during rapid load-variation, steam parameters lag due to the heat storage of thick-walled components. This leads to temperature differences between the inner and outer surfaces of thick-walled components, generating transient thermal stresses. This causes a surge in stress levels in thick-walled components, seriously impacting their safety and lifespan. This phenomenon is more pronounced at high load-variation rates. Therefore, it is necessary to control transient stresses in thick-walled components of rapidly varying load-variable boilers.

[0003] Because high-frequency, high-variable load rate peak shaving is a new topic in current boiler technology development, research on related stress control is relatively limited. Currently, there are two main methods for stress control: using compensating devices to offset the effects of thermal stress, and increasing the metal wall temperature on the working fluid side through methods such as electric heating to reduce temperature differences and ultimately reduce thermal stress. The former has limited application scenarios. For certain thick-walled components, such as steam-water separators, stress reduction through compensators is generally difficult. The latter stress control method is not suitable for peak-shaving boilers with high frequency and high-variable load rates. This is especially true during the boiler's load reduction phase, when the inner wall temperature of thick-walled components is lower than the outer wall temperature. Continued electric heating of the outer wall would further increase thermal stress in the thick-walled components, threatening their safety. Furthermore, electric heating equipment requires a large initial investment and consumes high-grade electricity during operation, making it less cost-effective. Summary of the Invention

[0004] The purpose of the present invention is to provide a device for regulating the stress of thick-walled components of a rapid load-changing boiler to solve the above-mentioned technical problems.

[0005] The object of the present invention is to provide a method for regulating the stress of thick-walled components of a rapid load-changing boiler.

[0006] To achieve the above-mentioned objectives, the present invention provides a device for stress control of thick-walled components of a rapid load-changing boiler, comprising a working medium inlet pipe, a first header, a header branch pipe, a second header and a working medium outlet pipe; the working medium inlet pipe is connected to the first header to input an external working medium whose temperature rises or falls synchronously with the internal working medium of the thick-walled component into the first header, and the first header is used to distribute the external working medium to each of the header branches; the second header is used to collect the external working medium of each of the header branches, and the working medium outlet pipe is used to output the collected external working medium; the first header surrounds one end of the thick-walled component, and the second header surrounds the other end of the thick-walled component, and each of the header branches is connected from each outlet of the first header to each inlet of the second header; the first header, the header branch pipe and the second header are all attached to the outer wall surface of the thick-walled component, so that when the temperature of the internal working medium of the thick-walled component changes, the external working medium indirectly heats or cools the outer wall surface of the thick-walled component through heat exchange.

[0007] Optionally, the manifold branch pipes are covered on the outer wall surface of the thick-walled element in a parallel structure; or, the manifold branch pipes are covered on the outer wall surface of the thick-walled element in a winding structure; or, the manifold branch pipes are covered on the outer wall surface of the thick-walled element in a grid structure.

[0008] Optionally, a branch portion is provided on an outer wall surface of the thick-walled element, and an avoidance area corresponding to the branch portion is formed between the manifold branches.

[0009] Optionally, the header branch pipes are bent and redirected to avoid the branching portion, and the spacing between the header branch pipes on both sides of the branching portion first gradually decreases and then gradually increases.

[0010] Optionally, the bending and direction-changing amplitude of the header branch pipe closer to the branching portion among the header branch pipes is greater than the bending and direction-changing amplitude of the header branch pipe farther from the branching portion.

[0011] Optionally, the external working medium is steam, the third steam extraction point of the steam turbine is provided with a third steam extraction pipeline, and the fourth steam extraction point of the steam turbine is provided with a fourth steam extraction pipeline, and the bypass of the third steam extraction pipeline and the fourth steam extraction pipeline are connected in a mixed manner and then communicated with the working medium inlet pipe.

[0012] Optionally, it also includes:

[0013] a first temperature detection device, provided on the thick-walled element, for detecting the temperature of the working medium inside the thick-walled element;

[0014] a second temperature detection device, provided on the working medium introduction pipe, for detecting the temperature of the external working medium before heat exchange with the thick-walled element;

[0015] a first flow control device, provided in a bypass of the third steam extraction pipeline, for increasing or decreasing the flow rate of the bypass of the third steam extraction pipeline according to a difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium inlet pipe, so that the temperature of the external working medium and the internal working medium of the thick-walled element are synchronously increased or decreased;

[0016] A second flow control device is provided in the bypass of the fourth steam extraction pipeline, and is used to reduce or increase the flow rate of the bypass of the fourth steam extraction pipeline according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium inlet pipe, so that the temperature of the external working medium and the internal working medium of the thick-walled element are synchronously increased or decreased.

[0017] Optionally, the external working medium is steam, the low-temperature section of the turbine reheat steam is provided with a low-temperature steam extraction pipeline, and the high-temperature section of the turbine reheat steam is provided with a high-temperature steam extraction pipeline, and the low-temperature steam extraction pipeline and the high-temperature steam extraction pipeline are connected in a mixed manner and then communicated with the working medium inlet pipe.

[0018] Optionally, it also includes:

[0019] a first temperature detection device, provided on the thick-walled element, for detecting the temperature of the working medium inside the thick-walled element;

[0020] a second temperature detection device, provided on the working medium introduction pipe, for detecting the temperature of the external working medium before heat exchange with the thick-walled element;

[0021] a first flow control device, provided in the low-temperature steam extraction pipeline, for increasing or decreasing the flow rate of the low-temperature steam extraction pipeline according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium inlet pipe, so that the temperature of the external working medium and the internal working medium of the thick-walled element are synchronously increased or decreased;

[0022] A second flow control device is provided in the high-temperature steam extraction pipeline, and is used to reduce or increase the flow of the high-temperature steam extraction pipeline according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium inlet pipe, so that the temperature of the external working medium and the internal working medium of the thick-walled element rise or fall synchronously.

[0023] Optionally, the external working medium is heat transfer oil.

[0024] Optionally, it also includes:

[0025] a first temperature detection device, provided on the thick-walled element, for detecting the temperature of the working medium inside the thick-walled element;

[0026] a second temperature detection device, provided on the working medium inlet pipe, for detecting the temperature of the heat transfer oil before heat exchange with the thick-walled element;

[0027] A heat transfer oil control device is used to adjust the heating amount or mass flow rate of the heat transfer oil according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the heat transfer oil entering the working medium inlet pipe, so that the temperature of the heat transfer oil increases or decreases synchronously with the internal working medium of the thick-walled element.

[0028] Optionally, the temperature of the external working medium is controlled between the outer wall temperature of the thick-walled element and the internal working medium temperature.

[0029] Optionally, the thick-walled component includes a steam-water separator, a high-temperature header or a steam drum.

[0030] Optionally, the gap between the header branch pipe and the thick-walled element is filled with heat-conducting material.

[0031] Optionally, the cross-sections of the first header, the header branch pipe, and the second header are circular tubes, semicircular tubes, or square tubes.

[0032] To achieve the above-mentioned another object, the present invention provides a method for controlling stress of thick-walled components in a rapid load-changing boiler, which utilizes any of the above-mentioned devices for controlling stress of thick-walled components in a rapid load-changing boiler, and comprises the following steps:

[0033] S01. When the boiler is in steady-state operation, the stress control device does not start and remains in silent state;

[0034] S02. The boiler is operating with rapid load changes. The stress control device is activated, and the external working fluid enters the stress control device to exchange heat with the thick-walled component. The external working fluid temperature changes synchronously with the internal working fluid temperature of the thick-walled component. Simultaneously, the external working fluid flow rate is adjusted according to the boiler's load change rate.

[0035] S03. The boiler's variable load operation ends, and the stress control device continues to operate for a period of time t before shutting down.

[0036] The stress control device and method for thick-walled components of a rapidly changing load boiler provided by the present invention can adjust the temperature and flow rate of an external working fluid entering the stress control device according to the rapidly changing load operating state of the boiler, and utilize the external working fluid circulating in the stress control device to exchange heat with the outer wall surface of the thick-walled component to achieve stress control of the thick-walled component, thereby reducing the stress level of the thick-walled component during the rapidly changing load process and extending the service life of the thick-walled component. The device has the advantages of low cost, wide adaptability, easy implementation and convenient modification. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1A schematic diagram of the partial structure of the device for stress control of thick-walled components of a rapid load-changing boiler provided in the first embodiment of the present invention;

[0038] Figure 2 for Figure 1 The stress control device shown is a reference diagram of the usage state when used in a steam-water separator;

[0039] Figure 3 This is a schematic diagram of the positions of the steam-water separator and high-temperature header in a once-through boiler;

[0040] Figure 4 This is a schematic diagram of the locations of the third and fourth steam extraction points of the steam turbine;

[0041] Figure 5 It is a graph of material property changes related to temperature;

[0042] Figure 6 The peak total stress variation diagram of the steam-water separator at different load rates during the 100%–75% THA load reduction process;

[0043] Figure 7 This is a graph showing the change in peak total stress of the steam-water separator under different variable load rates after the stress control device is installed.

[0044] In the picture:

[0045] 1-working medium inlet pipe; 2-first header; 3-header branch pipe; 4-second header; 5-working medium outlet pipe; 6-steam-water separator; 61-straight section of cylinder; 62-inlet pipe; 7-high-temperature header. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0047] In this article, terms such as "upper, lower, inside, outside" are established based on the positional relationships shown in the drawings. Depending on the different drawings, the corresponding positional relationships may also change accordingly. Therefore, they cannot be understood as absolute limitations on the scope of protection; moreover, relational terms such as "first" and "second" are only used to distinguish one component from another with the same name, and do not necessarily require or imply any actual relationship or order between these components.

[0048] Please refer to Figure 1 、 Figure 2 、 Figure 3 , Figure 1 A schematic diagram of the partial structure of the device for stress control of thick-walled components of a rapid load-changing boiler provided in the first embodiment of the present invention; Figure 2 for Figure 1 The stress control device shown is a reference diagram of the usage state when used in a steam-water separator; Figure 3 Schematic diagram of the position of the steam-water separator and high-temperature header in the direct current boiler.

[0049] As shown in the figure, in a specific embodiment, the device for stress control of thick-walled components of a rapid load-changing boiler provided by the present invention is mainly composed of a working fluid inlet pipe 1, a first header 2, a header branch pipe 3, a second header 4 and a working fluid outlet pipe 5.

[0050] Among them, the working fluid inlet pipe 1 is connected to the first header 2 to input the external working fluid whose temperature can rise or fall synchronously with the internal working fluid of the thick-walled component into the first header 2. Valves and other components can be set on the working fluid inlet pipe 1 to achieve control of the flow rate of the external working fluid.

[0051] The first manifold 2 is used to distribute the external working medium to each manifold branch 3. It is generally in the shape of a circular ring and surrounds one end of the thick-walled element. The second manifold 4 has a structure substantially the same as that of the first manifold and is also generally in the shape of a circular ring and surrounds the other end of the thick-walled element. It is used to collect the external working medium flowing through each manifold branch 3. The working medium outlet pipe 5 is connected to the second manifold 4 for outputting the collected external working medium.

[0052] The first header 2 is provided with a plurality of outlets, and the second header 4 is provided with a corresponding number of inlets. Each header branch pipe 3 is connected from each outlet of the first header 2 to each inlet of the second header 4 .

[0053] The cross-sections of the first header 2, the header branch 3, and the second header 4 can be circular tubes, semicircular tubes, or square tubes, all of which can fit onto the outer wall of the thick-walled component. If they are semicircular tubes or square tubes, they mainly contact the outer wall of the thick-walled component through the straight surface to increase the heat exchange contact area between the two.

[0054] During operation, the inner wall surfaces of the first header 2, the header branch pipe 3, and the second header 4 come into contact with the flowing external working fluid, which is then transferred to the outer wall of the thick-walled component through the outer wall surface, thereby realizing energy exchange between the external working fluid and the thick-walled component. When the temperature of the internal working fluid of the thick-walled component changes, the external working fluid indirectly heats or cools the outer wall of the thick-walled component through heat exchange.

[0055] If the boiler type is a once-through boiler, the thick-walled component can be the steam-water separator 6 or the high-temperature header 7 of the once-through boiler. If the boiler type is a natural circulation boiler, the thick-walled component can also be the steam drum located at the top of the boiler.

[0056] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below by taking a steam-water separator of a coal-fired unit as an example in conjunction with the accompanying drawings and specific implementation methods.

[0057] In this embodiment, the thick-walled component is the separator 6 of a 350MW supercritical tower-type once-through boiler at a power plant. This separator 6 is a centrifugal separator with a barrel measuring 762 x 120mm. Six inlet pipes 62 are inserted tangentially downward at a 15° angle into the straight barrel section 61. The inlet pipes have an inner diameter of 97mm and are rotationally symmetrical about the barrel's central axis, with a rotation angle of 60°.

[0058] The manifold branch pipe 3 is covered on the outer wall of the steam-water separator 6 in a parallel structure. The arrangement density thereof can be adjusted according to the shape of the steam-water separator 6, but it needs to fit the outer wall of the steam-water separator 6 to achieve heat exchange. The gap between the manifold branch pipe 3 and the steam-water separator 6 can also be filled with thermal conductive putty or other materials to enhance heat exchange.

[0059] Specifically, the manifold branch pipe 3 avoids the inlet pipe 62 by bending and changing direction. The distance between the manifold branch pipes 3 on both sides of the inlet pipe 62 first gradually decreases and then gradually increases. The manifold branch pipe 3 closer to the inlet pipe 62 has a larger bending and changing direction amplitude, while the manifold branch pipe 3 farther away from the inlet pipe 62 has a smaller bending and changing direction amplitude, thereby forming an avoidance area corresponding to the inlet pipe 62 between the manifold branch pipes 3.

[0060] Because the steam-water separator 6 has six inlet pipes 62, the manifold branch pipes 3 form six escape zones. Five manifold branch pipes 3 are located between two adjacent escape zones. The central manifold branch pipe 3 is straight and does not bend or deform. The remaining four manifold branch pipes 3 bend and deform symmetrically around the central manifold branch pipe 3. Assuming the manifold branch pipes 3 have a certain degree of flexibility, the escape zones are equivalent to the spaces formed by spreading the manifold branch pipes 3 apart from the point where they enter the inlet pipes 62.

[0061] Of course, in other embodiments, the header branch pipe 3 may also be wrapped around the outer wall of the steam-water separator 6 in a winding structure; or, the header branch pipe 3 may be wrapped around the outer wall of the steam-water separator 6 in a grid structure.

[0062] The external working medium is used to cool or heat the outer wall of the steam-water separator 6. The type (steam, thermal oil, etc.) and temperature of the external working medium are not limited, but must meet the heat exchange requirements.

[0063] Please refer to Figure 4 , Figure 4 This is a schematic diagram of the locations of the third and fourth steam extraction points of the steam turbine.

[0064] As shown in the figure, in this embodiment, the external working fluid is steam, and a high-temperature steam source (the fourth steam extraction port) and a low-temperature steam source (the third steam extraction port) are selected and mixed to serve as the working fluid of the stress control device. By adjusting the extraction mass flow rates of the two steam sources, the temperature of the mixed steam is controlled so that the temperature of the mixed steam is close to the inlet steam temperature of the steam-water separator 6.

[0065] Specifically, the steam turbine is usually equipped with the first extraction point, the second extraction point, the third extraction point, the fourth extraction point and other extraction points. The extraction points usually correspond to the high-pressure heaters. For example, the first extraction point corresponds to the #1 high-pressure heater (HTR-1), the second extraction point corresponds to the #2 high-pressure heater (HTR-2), and so on (Note: the fourth extraction point corresponds to the deaerator DRTR).

[0066] The third extraction point of the steam turbine is provided with a third extraction pipeline, and the fourth extraction point of the steam turbine is provided with a fourth extraction pipeline. The bypass of the third extraction pipeline and the fourth extraction pipeline are connected in a mixed manner and then communicated with the working medium introduction pipe 1.

[0067] In order to achieve automatic synchronous change of the mixed steam temperature and the working medium temperature inside the steam-water separator 6, the mixed steam temperature can be detected and used to regulate the steam extraction flow of the high-temperature steam source and the low-temperature steam source to achieve the consistency of the mixed steam temperature and the steam temperature inside the steam-water separator 6.

[0068] For this purpose, the following device is further provided:

[0069] A first temperature detection device is provided in the steam-water separator 6 and is used to detect the temperature of the working medium inside the steam-water separator 6;

[0070] The second temperature detection device is provided on the working medium inlet pipe 1 and is used to detect the temperature of the external working medium before heat exchange with the steam-water separator 6;

[0071] a first flow control device, provided in a bypass of the third steam extraction pipeline, for increasing or decreasing the flow rate of the bypass of the third steam extraction pipeline according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium inlet pipe 1, so that the temperature of the external working medium and the working medium inside the steam-water separator 6 are synchronously increased or decreased;

[0072] The second flow control device is provided in the bypass of the fourth steam extraction pipeline and is used to reduce or increase the flow of the bypass of the fourth steam extraction pipeline according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium inlet pipe 1, so that the temperature of the external working medium and the internal working medium of the steam-water separator 6 are synchronously increased or decreased.

[0073] In another embodiment, in addition to extracting steam from the third and fourth extraction points of the steam turbine, steam can also be extracted from the low-temperature section (about 300°C) and high-temperature section (about 500°C) of the steam turbine reheat steam and mixed.

[0074] Specifically, the low-temperature section of the turbine reheat steam is provided with a low-temperature steam extraction pipeline, and the high-temperature section of the turbine reheat steam is provided with a high-temperature steam extraction pipeline. The low-temperature steam extraction pipeline and the high-temperature steam extraction pipeline are connected in a mixed manner and then communicated with the working medium inlet pipe 1.

[0075] Similarly, in order to achieve automatic synchronous changes in the mixed steam temperature and the working medium temperature inside the steam-water separator 6, the mixed steam temperature can be detected and used to regulate the steam extraction flow of the high-temperature steam source and the low-temperature steam source to achieve the consistency between the mixed steam temperature and the steam temperature inside the steam-water separator 6.

[0076] For this purpose, the following device is further provided:

[0077] A first temperature detection device is provided in the steam-water separator 6 and is used to detect the temperature of the working medium inside the steam-water separator 6;

[0078] The second temperature detection device is provided on the working medium inlet pipe 1 and is used to detect the temperature of the external working medium before heat exchange with the steam-water separator 6;

[0079] A first flow control device is provided in the low-temperature steam extraction pipeline, and is used to increase or decrease the flow rate of the low-temperature steam extraction pipeline according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium inlet pipe 1, so that the temperature of the external working medium and the internal working medium of the steam-water separator 6 are synchronously increased or decreased;

[0080] The second flow control device is provided in the high-temperature steam extraction pipeline, and is used to reduce or increase the flow of the high-temperature steam extraction pipeline according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium inlet pipe 1, so that the temperature of the external working medium and the internal working medium of the steam-water separator 6 are synchronously increased or decreased.

[0081] In another embodiment, the external working medium may also be heat transfer oil. In order to achieve automatic synchronous change of the temperature of the heat transfer oil and the working medium inside the steam-water separator 6, the following device is further provided:

[0082] A first temperature detection device is provided in the steam-water separator 6 and is used to detect the temperature of the working medium inside the steam-water separator 6;

[0083] The second temperature detection device is provided on the working medium inlet pipe 1 and is used to detect the temperature of the heat transfer oil before heat exchange with the steam-water separator 6;

[0084] The heat transfer oil control device is used to adjust the heating amount or mass flow of the heat transfer oil according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the heat transfer oil entering the working medium inlet pipe 1, so that the temperature of the heat transfer oil increases or decreases synchronously with the internal working medium of the thick-walled component.

[0085] In the above embodiment, the temperature of the external working medium can be controlled between the temperature of the outer wall of the thick-walled element and the temperature of the internal working medium, so that heat exchange can be carried out more smoothly between them.

[0086] Please refer to Figures 5 to 7 , Figure 5 It is a graph of material property changes related to temperature; Figure 6 The peak total stress variation diagram of the steam-water separator at different load rates during the 100%–75% THA load reduction process; Figure 7 This is a graph showing the change in peak total stress of the steam-water separator under different variable load rates after the stress control device is installed.

[0087] In this embodiment of the present invention, a typical generator set load reduction condition was studied: stable operation after a steady-state THA of 100% was reduced to 75% THA. The working fluid of the stress control device was a mixture of steam from the turbine's third extraction point (452.7–454.7°C) and fourth extraction point (360.4–365.4°C).

[0088] The structural material of the steam-water separator is 15CrMoG, with a density of 7770kg / m 3 , the embodiment takes into account the temperature-related changes in material properties such as Figure 5 shown.

[0089] A typical load reduction condition was selected for study: stable operation after the steady-state load dropped from 100% THA to 75% THA. At 100% THA, the inlet steam temperature and pressure to separator 6 were 442.5°C and 27 MPa, respectively; at 75% THA, the inlet steam temperature and pressure to separator 6 were 410.9°C and 19.5 MPa, respectively.

[0090] During the load reduction process from 100% to 75% THA, the peak total stress of the steam-water separator 6 changes at different load rates as shown in the following figure: Figure 6As shown in the figure, during steady-state operation at 100% THA load (at time 0s), the peak total stress of separator 6 is approximately 272 MPa. Once the load reduction process begins, the peak total stress of separator 6 increases and then decreases at various load rates. This phenomenon can be explained by the coupling effect of stresses: peak stress is the result of the coupling of mechanical and thermal stresses. Mechanical stress is determined by the internal steam pressure, while thermal stress originates from the temperature difference between the inner and outer walls of the separator. During the load reduction process, the internal temperature of the separator decreases, and the thermal stress generated by the greater expansion of the outer wall than the inner wall couples more strongly with the mechanical stress generated by the steam pressure on the inner wall, leading to an increase in the peak total stress. The maximum peak total stress increases with increasing load rate. When the load rate increases from 2% THA / min to 6% THA / min, the maximum peak total stress of separator 6 decreases from 281 MPa to 301 MPa.

[0091] In this embodiment, steam from the third extraction point of the steam turbine (452.7–454.7°C) and steam from the fourth extraction point (360.4–365.4°C) are selected and mixed as the working fluid of the stress control device. By adjusting the flow rates of the two, the temperature of the mixed steam is made close to the inlet steam temperature of the steam-water separator 6. Figure 7 The figure shows the change in peak total stress of the separator 6 at different load rates when the stress control device is installed. It can be seen that after adding the stress control device, the peak total stress of the separator 6 continues to decrease during the load reduction process at different load rates, achieving stress control for thick-walled components during rapid load changes.

[0092] The above embodiments are merely preferred solutions of the present invention and are not intended to be limiting. Based on these solutions, targeted adjustments can be made based on actual needs, resulting in different implementations. For example, the type of heat exchange medium can be selected based on the actual conditions of the thick-walled components, such as steam or thermal oil. The temperature of the heat exchange medium is not limited to the above examples and can be other values ​​that better suit actual operating conditions. This embodiment will not list all of these examples, etc. Due to the numerous possible implementations, we will not provide a detailed description here.

[0093] In addition to the above-mentioned stress control device, the present invention also provides a method for controlling stress of thick-walled components of a rapid load-changing boiler, which utilizes the above-mentioned device for controlling stress of thick-walled components of a rapid load-changing boiler and includes the following steps:

[0094] S01. When the boiler is in steady-state operation, the stress control device does not start and remains in silent state;

[0095] S02. The boiler is operating with rapid load changes. The stress control device is activated, and the external working fluid enters the stress control device to exchange heat with the thick-walled component. The external working fluid temperature changes synchronously with the internal working fluid temperature of the thick-walled component. Simultaneously, the external working fluid flow rate is adjusted according to the boiler's load change rate.

[0096] S03. After the boiler load change operation is completed, the stress control device continues to operate for a period of time t and then shuts down (the time t is related to the boiler load change rate and the thermal physical properties of the thick-walled components).

[0097] The present invention has at least the following beneficial effects:

[0098] 1) This invention utilizes heat exchange between the working fluid within the stress control device and the outer surface of the thick-walled component. The temperature and flow rate of the incoming working fluid are adjusted according to the boiler's variable load operation, reducing the stress level in the thick-walled component during rapid load changes.

[0099] 2) The present invention cools (heats) the thick-walled components through the external working fluid in the stress control device, thereby reducing the heat exchange between the thick-walled components and the boiler steam, and weakening the influence of the thermal inertia of the thick-walled components on the boiler steam parameters.

[0100] 3) The installation, commissioning, disassembly, maintenance, and automation modification of this invention have no impact on the normal operation of thick-walled components. It can be installed at the beginning of equipment design or during equipment operation. It has the advantages of easy implementation, simple installation, and convenient modification.

[0101] The above describes in detail the device and method for stress control of thick-walled components in rapidly variable-load boilers provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above examples is intended only to facilitate understanding of the core concepts of the present invention. It should be noted that those skilled in the art may make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A device for controlling stress of thick-walled components of a rapidly changing load boiler, characterized in that: The invention comprises a working medium inlet pipe (1), a first header (2), a header branch pipe (3), a second header (4) and a working medium outlet pipe (5); the working medium inlet pipe (1) is connected to the first header (2) to input an external working medium whose temperature rises or falls synchronously with the internal working medium of the thick-walled element into the first header (2); the first header (2) is used to distribute the external working medium to each of the header branch pipes (3); the second header (4) is used to collect the external working medium of each of the header branch pipes (3); the working medium outlet pipe (5) is used to output the collected working medium. The first manifold (2) surrounds one end of the thick-walled element, the second manifold (4) surrounds the other end of the thick-walled element, and each of the manifold branch pipes (3) is connected from each outlet of the first manifold (2) to each inlet of the second manifold (4); the first manifold (2), the manifold branch pipe (3), and the second manifold (4) are all attached to the outer wall surface of the thick-walled element, so that when the temperature of the internal working medium of the thick-walled element changes, the external working medium indirectly heats or cools the outer wall surface of the thick-walled element through heat exchange.

2. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to claim 1, characterized in that: The manifold branch pipe (3) is wrapped around the outer wall surface of the thick-walled element in a parallel structure; or, the manifold branch pipe (3) is wrapped around the outer wall surface of the thick-walled element in a winding structure; or, the manifold branch pipe (3) is wrapped around the outer wall surface of the thick-walled element in a grid structure.

3. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to claim 2, characterized in that: The outer wall surface of the thick-walled element is provided with a branching portion, and an escape area corresponding to the branching portion is formed between the header branch pipes (3).

4. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to claim 3, characterized in that: The header branch pipe (3) avoids the branch portion by bending and changing direction, and the spacing between the header branch pipes (3) located on both sides of the branch portion first gradually decreases and then gradually increases.

5. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to claim 4, characterized in that: The bending and direction-changing amplitude of the header branch pipe (3) closer to the branching portion among the header branch pipes (3) is greater than the bending and direction-changing amplitude of the header branch pipe (3) farther from the branching portion.

6. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to claim 1, characterized in that: The external working medium is steam, the third steam extraction point of the steam turbine is provided with a third steam extraction pipeline, the fourth steam extraction point of the steam turbine is provided with a fourth steam extraction pipeline, the third steam extraction pipeline and the bypass of the fourth steam extraction pipeline are connected in a mixed manner and then communicated with the working medium introduction pipe (1).

7. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to claim 6, characterized in that: Also includes: a first temperature detection device, provided on the thick-walled element, for detecting the temperature of the working medium inside the thick-walled element; A second temperature detection device, provided on the working medium inlet pipe (1), for detecting the temperature of the external working medium before heat exchange with the thick-walled element; A first flow control device is provided in the bypass of the third steam extraction pipeline, and is used to increase or decrease the flow of the bypass of the third steam extraction pipeline according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium introduction pipe (1), so that the temperature of the external working medium and the internal working medium of the thick-walled element are synchronously increased or decreased; The second flow control device is provided in the bypass of the fourth steam extraction pipeline and is used to reduce or increase the flow of the bypass of the fourth steam extraction pipeline according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium inlet pipe (1), so that the temperature of the external working medium and the internal working medium of the thick-walled element are synchronously increased or decreased.

8. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to claim 1, characterized in that: The external working medium is steam, the low-temperature section of the turbine reheat steam is provided with a low-temperature steam extraction pipeline, and the high-temperature section of the turbine reheat steam is provided with a high-temperature steam extraction pipeline, and the low-temperature steam extraction pipeline and the high-temperature steam extraction pipeline are connected in a mixed manner and then communicated with the working medium introduction pipe (1).

9. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to claim 8, characterized in that: Also includes: a first temperature detection device, provided on the thick-walled element, for detecting the temperature of the working medium inside the thick-walled element; A second temperature detection device, provided on the working medium inlet pipe (1), for detecting the temperature of the external working medium before heat exchange with the thick-walled element; a first flow control device, provided in the low-temperature steam extraction pipeline, for increasing or decreasing the flow of the low-temperature steam extraction pipeline according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium introduction pipe (1), so that the temperature of the external working medium and the internal working medium of the thick-walled element are synchronously increased or decreased; A second flow control device is provided in the high-temperature steam extraction pipeline and is used to reduce or increase the flow of the high-temperature steam extraction pipeline according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the water vapor entering the working medium introduction pipe (1), so that the temperature of the external working medium and the internal working medium of the thick-walled element are synchronously increased or decreased.

10. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to claim 1, characterized in that: The external working medium is heat transfer oil.

11. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to claim 10, characterized in that: Also includes: a first temperature detection device, provided on the thick-walled element, for detecting the temperature of the working medium inside the thick-walled element; A second temperature detection device, provided on the working medium inlet pipe (1), for detecting the temperature of the heat transfer oil before heat exchange with the thick-walled element; A heat transfer oil control device is used to adjust the heating amount or mass flow of the heat transfer oil according to the difference between the first temperature detection device and the second temperature detection device, so as to control the temperature of the heat transfer oil entering the working medium introduction pipe (1), so that the temperature of the heat transfer oil and the internal working medium of the thick-walled element are synchronously increased or decreased.

12. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to any one of claims 1 to 11, characterized in that: The temperature of the external working medium is controlled between the outer wall temperature of the thick-walled component and the internal working medium temperature.

13. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to any one of claims 1 to 11, characterized in that: The thick-walled components include a steam-water separator (6), a high-temperature header (7), or a steam drum.

14. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to any one of claims 1 to 11, characterized in that: The gap between the header branch pipe (3) and the thick-walled element is filled with heat-conducting material.

15. The device for controlling stress of thick-walled components of a rapid load-changing boiler according to any one of claims 1 to 11, characterized in that: The cross sections of the first header (2), the header branch pipe (3), and the second header (4) are circular tubes, semicircular tubes, or square tubes.

16. A method for controlling stress of thick-walled components of a rapid load-changing boiler, characterized in that: The device for controlling stress of thick-walled components of a rapid load-changing boiler according to any one of claims 1 to 15 comprises the following steps: S01. When the boiler is in steady-state operation, the stress control device does not start and remains in silent state; S02. The boiler is operating with rapid load changes. The stress control device is activated, and the external working fluid enters the stress control device to exchange heat with the thick-walled component. The external working fluid temperature changes synchronously with the internal working fluid temperature of the thick-walled component. Simultaneously, the external working fluid flow rate is adjusted according to the boiler's load change rate. S03. The boiler's variable load operation ends, and the stress control device continues to operate for a period of time t before shutting down.

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