Device and method for regulating and controlling stress of thick-wall element of quick variable-load boiler

Abstract

The invention relates to a device and a method for regulating and controlling the stress of a thick-wall element of a rapid variable-load boiler. The device comprises a working medium lead-in pipe, a first collecting box, a collecting box branch pipe, a second collecting box and a working medium lead-out pipe, the working medium introducing pipe is connected with the first collecting box so as to input an external working medium of which the temperature is synchronously increased or decreased with an internal working medium of the thick-wall element into the first collecting box; the first header and the second header surround the two ends of the thick-wall element respectively, and all the header branch pipes are communicated with all the inlets of the second header from all the outlets of the first header. The first collecting box, the collecting box branch pipes and the second collecting box are all attached to the outer wall face of the thick-wall element, so that when the temperature of an internal working medium of the thick-wall element changes, the outer wall face of the thick-wall element is indirectly heated or cooled through heat exchange by an external working medium. According to the device, the stress level of the thick-wall element in the rapid load changing process can be reduced, and the service life of the thick-wall element is prolonged.

Description

Technical Field

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

[0002] my country's future energy consumption increase will mainly come from clean energy, but new energy sources, mainly wind and solar energy, have the disadvantages of randomness and intermittency. In order to fully absorb new energy, more and more thermal power units frequently participate in peak load regulation tasks. Peak load regulation tasks require boilers to have a high load change rate. Unlike the steady state, during the rapid load change process of the boiler, due to the heat storage effect of the thick-walled components, the steam parameters lag, resulting in a temperature difference between the inner and outer wall surfaces of the thick-walled components, generating transient thermal stress. This causes a surge in the stress level of the thick-walled components, seriously affecting the safety and life of the thick-walled components. This phenomenon is more obvious under high load change rates. Therefore, it is necessary to control the transient stress of the thick-walled components of the rapid load change boiler.

[0003] Since the high-frequency and high-variable load rate peak regulation of boilers is a new topic in the current development of boiler technology, there are few studies on related stress regulation. At present, there are two main ways to regulate stress. One is to use a compensation device to offset the influence of thermal stress, and the other is to increase the metal wall temperature on the working fluid side by means of electric heating, thereby reducing the temperature difference and achieving the purpose of reducing thermal stress. The application scenarios of the former are limited. For some thick-walled components, such as steam-water separators, it is generally difficult to reduce stress through compensators. The latter stress regulation method is not suitable for peak-shaving boilers with high frequency and high variable load rate. Especially in the load reduction stage of the boiler, the inner wall temperature of the thick-walled component is lower than the outer wall temperature. If the outer wall surface continues to be electrically heated, the thermal stress of the thick-walled component will further increase, threatening the safety of the thick-walled component. In addition, the initial investment of electric heating equipment is large, and it consumes high-grade electricity during operation, which is less economical. Summary of the invention

[0004] The object 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 controlling the stress of thick-walled components of a rapid load-changing boiler.

[0006] To achieve the above-mentioned purpose, the present invention provides a device for stress control of thick-walled components of a rapid load change boiler, comprising 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, and the first header is used to distribute the external working fluid to each of the header branches; the second header is used to collect the external working fluid of each of the header branches, and the working fluid outlet pipe is used to output the collected external working fluid; the first header surrounds one end of the thick-walled component, 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 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.

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

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

[0009] Optionally, the header branch pipe is bent and changed direction 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 that is closer to the branching position among the header branch pipes is greater than the bending and direction-changing amplitude of the header branch pipe that is farther from the branching position.

[0011] Optionally, the external working medium is steam, the third extraction point of the steam turbine is provided with a third extraction pipeline, the fourth extraction point of the steam turbine is provided with a fourth extraction pipeline, and 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 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 at 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 the bypass of the third steam extraction pipeline, for increasing or decreasing 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, 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] The second flow control device is arranged 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, 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 fluid 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 fluid 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 at 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 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, 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] The second flow control device is arranged 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 are synchronously increased or decreased.

[0023] Optionally, the external working fluid 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 at the working medium introduction pipe, for detecting the temperature of the heat transfer oil before heat exchange with the thick-walled element;

[0027] The 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 fluid introduction pipe, so that the temperature of the heat transfer oil increases or decreases synchronously with the internal working fluid 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 element 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 a 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 another object, the present invention is a method for controlling stress of thick-walled components of a rapid load-changing boiler, which uses any of the above-mentioned devices for controlling stress of thick-walled components of a rapid load-changing boiler, and the steps include:

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

[0034] S02. The boiler is operated with rapid load change, the stress control device is started, and the external working fluid enters the stress control device to exchange heat with the thick-walled component; the temperature of the external working fluid changes synchronously with the internal working fluid temperature of the thick-walled component; at the same time, the flow rate of the external working fluid is adjusted according to the variable load rate of the boiler;

[0035] S03. The boiler 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 operation state of the boiler, and utilize the external working fluid flowing 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 and method have 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 a device for regulating stress 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 regulating device shown is a reference diagram of the use 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 the high-temperature header in the once-through boiler;

[0040] Figure 4 It is a schematic diagram of the positions of the third steam extraction point and the fourth steam extraction point 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 variable 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 at different variable load rates after the stress control device is installed.

[0044] In the figure:

[0045] 1-working fluid inlet pipe; 2-first header; 3-header branch pipe; 4-second header; 5-working fluid 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 scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0047] In this article, the terms "upper, lower, inside, outside" and the like are established based on the positional relationships shown in the drawings. The corresponding positional relationships may also change depending on the drawings, and therefore cannot be understood as absolute limitations on the scope of protection; moreover, relational terms such as "first" and "second" and the like are merely 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 a device for regulating stress 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 regulating device shown is a reference diagram of the use state when used in a steam-water separator; Figure 3 Schematic diagram of the location 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 regulation of thick-walled components of a rapid load change 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 introduction 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 element into the first header 2. Valves and other components can be set on the working fluid introduction 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 fluid to each manifold branch pipe 3. It is generally in the shape of a ring and surrounds one end of the thick-walled element. The second manifold 4 has a substantially similar structure to the first manifold and is also generally in the shape of a ring and surrounds the other end of the thick-walled element. It is used to collect the external working fluid flowing through each manifold branch pipe 3. The working fluid outlet pipe 5 is connected to the second manifold 4 for outputting the collected external working fluid.

[0052] The first header 2 is provided with a plurality of outlets, the second header 4 is provided with a plurality of inlets of a corresponding number, and 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 pipe 3 and the second header 4 can be circular tubes, semicircular tubes or square tubes, all of which can fit 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 are in 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 internal working fluid temperature 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 direct-current boiler, the thick-walled component may be the steam-water separator 6 or the high-temperature header 7 of the direct-current boiler; if the boiler type is a natural circulation boiler, the thick-walled component may 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 scheme of the present invention, the present invention will be further described in detail below by taking the steam-water separator of a coal-fired unit as an example in combination with the accompanying drawings and specific implementation methods.

[0057] In this embodiment, the thick-walled component is a steam-water separator 6 of a 350MW supercritical tower-type direct-current boiler in a power plant. The steam-water separator 6 is a centrifugal steam-water separator, and the barrel specification is Φ762×120mm. Six inlet pipes 62 are inserted into the straight barrel 61 along the tangential downward and inclined at 15°. The inner diameter of the inlet pipe is 97mm, and the inlet pipe is rotationally symmetrical around the central axis of the barrel, and the rotation angle is 60°.

[0058] The manifold branch pipe 3 is covered on the outer wall of the steam-water separator 6 in a parallel structure, and its arrangement density 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 paste and other materials to enhance heat exchange.

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

[0060] Since the steam-water separator 6 is provided with a total of six inlet pipes 62, the header branch pipe 3 forms a total of six avoidance areas, and five header branch pipes 3 are provided between two adjacent avoidance areas. The header branch pipe 3 in the middle is a straight pipe and does not bend or deform, and the remaining four header branch pipes 3 are symmetrically bent and deformed with the middle header branch pipe 3 as the center. If it is assumed that the header branch pipe 3 has a certain degree of flexibility, the avoidance area is equivalent to the space area formed by pushing the header branch pipe 3 from the position where the inlet pipe 62 penetrates to both sides.

[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, heat transfer oil, etc.) and temperature of the external working medium are not limited, but need to 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 as the working fluid of the stress control device. By adjusting the steam 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 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. 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 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 with the steam temperature inside the steam-water separator 6.

[0068] To this end, 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 introduction 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 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 steam-water separator 6 are synchronously increased or decreased;

[0072] The second flow control device is arranged 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 extraction point and the fourth extraction point 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 introduction pipe 1.

[0075] Similarly, 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 rates 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] To this end, 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 introduction 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 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 steam-water separator 6 are synchronously increased or decreased;

[0080] The second flow control device is arranged 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 introduction 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 fluid inlet pipe 1, so that the temperature of the heat transfer oil increases or decreases synchronously with the internal working fluid 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 variable 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 at different variable load rates after the stress control device is installed.

[0087] In the embodiment of the present invention, a typical operating condition of a generator set with load reduction is selected for research: the steady-state 100% THA drops to 75% THA and then operates stably. The working medium of the stress control device is a mixed steam of the third extraction point steam (452.7-454.7℃) and the fourth extraction point steam (360.4-365.4℃) of the steam turbine.

[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: the steady-state 100% THA dropped to 75% THA and then operated stably. Under the boiler load of 100% THA, the inlet steam temperature and pressure of the steam-water separator 6 were 442.5℃ and 27MPa respectively; under the boiler load of 75% THA, the inlet steam temperature and pressure of the steam-water separator 6 were 410.9℃ and 19.5MPa respectively.

[0090] During the 100%–75% THA load reduction process, the peak total stress variation of the steam-water separator 6 at different load rates is shown in Figure 2. Figure 6As shown. It can be seen that when the 100% THA load is in steady-state operation (at 0s), the peak total stress of the steam-water separator 6 is about 272MPa. When the load reduction process begins, the peak total stress of the steam-water separator 6 increases first and then decreases at different variable load rates. This phenomenon can be explained from the coupling effect of stress. The peak stress is the coupling effect of mechanical stress and thermal stress. The mechanical stress is determined by the internal steam pressure, and the thermal stress originates from the temperature difference between the inner and outer walls of the steam-water separator. During the load reduction process, the internal temperature of the steam-water separator decreases, and the thermal stress generated by the expansion of the outside is greater than the expansion of the inside. The coupling with the mechanical stress generated by the steam pressure of the inner wall is strengthened, resulting in an increase in the peak total stress. The maximum value of the peak total stress increases with the increase of the variable load rate. When the variable load rate increases from 2%THA / min to 6%THA / min, the maximum value of the peak total stress of the steam-water separator 6 decreases from 281MPa to 301MPa.

[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. The temperature of the mixed steam is made close to the inlet steam temperature of the steam-water separator 6 by adjusting the flow rates of the two. Figure 7 The figure shows the change of the peak total stress of the water-gas separator 6 at different variable load rates when the stress control device is provided. It can be seen that after adding the stress control device, the peak total stress of the water-gas separator 6 at different variable load rates continues to decrease during the load reduction process, realizing the stress control of thick-walled components during rapid load changes.

[0092] The above embodiments are only preferred solutions of the present invention, and are not limited thereto. On this basis, targeted adjustments can be made according to actual needs to obtain different implementation methods. For example, the type of heat exchange medium can be selected according to the actual situation of the thick-walled element, and can be steam, heat transfer oil, etc. The temperature of the heat exchange medium is not limited to the above examples, and can be other values ​​that are more in line with actual working conditions. This embodiment will not be listed one by one, etc. Since there are many possible implementation methods, they will not be illustrated one by one here.

[0093] In addition to the above 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 stress control device for 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 silent;

[0095] S02. The boiler is operated with rapid load change, the stress control device is started, and the external working fluid enters the stress control device to exchange heat with the thick-walled component; the temperature of the external working fluid changes synchronously with the internal working fluid temperature of the thick-walled component; at the same time, the flow rate of the external working fluid is adjusted according to the variable load rate of the boiler;

[0096] S03. After the boiler load change operation is completed, the stress control device continues to operate for a period of time t before shutting 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) The present invention utilizes the working fluid in the stress control device to exchange heat with the outer wall of the thick-walled component. According to the variable load operation state of the boiler, the temperature and flow rate of the external working fluid are adjusted, thereby reducing the stress level of the thick-walled component during the rapid load change process.

[0099] 2) The present invention cools (heats) the thick-walled components through the external working fluid in the stress regulating 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, debugging, disassembly maintenance and automation transformation of the present invention have no influence on the normal operation of thick-walled components, and can be installed at the beginning of equipment design or during equipment operation. It has the advantages of easy implementation, simple installation and convenient transformation.

[0101] The above is a detailed introduction to the device and method for stress control of thick-walled components of a rapid load-changing boiler 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 embodiments is only used to help understand the core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these 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 rapid load-changing 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) so as to input an external working medium whose temperature rises or falls synchronously with that of 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 to the first header (2); The first header (2) surrounds one end of the thick-walled element, the second header (4) surrounds the other end of the thick-walled element, and each of the header branch pipes (3) is connected from each outlet of the first header (2) to each inlet of the second header (4); the first header (2), the header branch pipes (3), and the second header (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 header branch pipe (3) is coated on the outer wall surface of the thick-walled element in a parallel structure; or, the header branch pipe (3) is coated on the outer wall surface of the thick-walled element in a winding structure; or, the header branch pipe (3) is coated on 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 branching portion by bending and changing direction, and the spacing between the header branch pipes (3) located on both sides of the branching 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 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 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, a third steam extraction point of the steam turbine is provided with a third steam extraction pipeline, a 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 introduction pipe (1), for detecting the temperature of the external working medium before heat exchange with the thick-walled element; a first flow control device, arranged in the bypass of the third steam extraction pipeline, for increasing or decreasing 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; 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 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 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.

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 introduction pipe (1), for detecting the temperature of the external working medium before heat exchange with the thick-walled element; a first flow control device, arranged 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 introduction 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 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 introduction pipe (1), so that the temperature of the heat transfer oil rises or falls synchronously with the internal working medium of the thick-walled element.

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 element 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 element includes 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 silent; S02. The boiler is operated with rapid load change, the stress control device is started, and the external working fluid enters the stress control device to exchange heat with the thick-walled component; the temperature of the external working fluid changes synchronously with the internal working fluid temperature of the thick-walled component; at the same time, the flow rate of the external working fluid is adjusted according to the variable load rate of the boiler; S03. The boiler 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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