Full load high efficiency steam turbine unit, thermal system and operation method

Abstract

This invention provides a full-load high-efficiency steam turbine unit, a thermal system, and an operating method. At least two steam channels (7) are radially arranged in the regulating stage (6) at the front end of the high-pressure cylinder (4). When the thermal system is in different load ranges, it can switch to the corresponding steam channel (7) for operation. The different steam flow capacities between different steam channels (7) and the different number of pressure stages they are equipped with are used to adapt to different load conditions, ensuring high circulation efficiency and low system energy consumption under medium and low loads. The main steam valve (5) and regulating valve (51) set in the pipeline system are used to control the opening and closing of each steam channel (7). In addition, by setting up a multi-level branch steam network, a smooth transition can be achieved when switching between different steam channels (7), avoiding sudden changes in steam flow. Under medium and low loads, by leading an extraction pipe out of the end of the regulating stage (6) and connecting it to the adjustable heater (19), the water temperature at the inlet of the boiler (1) is increased. The flue gas temperature at the denitrification point is adjusted according to actual needs to meet the denitrification requirements.

Description

Technical Field

[0001] This invention belongs to the field of thermal cycle technology, and particularly relates to a full-load high-efficiency steam turbine unit, thermal system and operation method. Background Technology

[0002] With the large-scale grid connection of renewable energy sources such as photovoltaic and wind power, which exhibit random fluctuations, the basic power system, primarily composed of coal-fired power, is forced to fully participate in deep peak shaving. Coal-fired power units are designed mainly for operating efficiency under rated load conditions. However, during deep peak shaving, the power generation efficiency of these units deteriorates sharply under medium- and low-load conditions. Compared to rated load conditions, conventional coal-fired power units consume 30-40 g / kW·h more coal at 30% of their rated load. This significantly diminishes the overall energy conservation and emission reduction benefits for society resulting from making way for renewable energy.

[0003] Based on the existing technical and structural characteristics of steam turbines and thermal systems, under low-load conditions, regardless of whether the main steam pressure operates in sliding pressure, constant pressure, or "constant-sliding-constant" mode, the pressures after the regulating stage drop significantly. Furthermore, under medium- and low-load conditions, the large ideal enthalpy drop between the rated main steam pressure provided by the boiler and the pressure after the regulating stage cannot be effectively utilized by existing technologies. This directly leads to a significant decrease in the cycle efficiency of the thermal system and a substantial increase in system energy consumption under medium- and low-load conditions.

[0004] Solving the problem of reduced operating efficiency under low load conditions during deep peak shaving of coal-fired power units is crucial to the timely and high-quality achievement of the national "dual carbon" targets, which are related to enterprise energy conservation and emission reduction, overall energy conservation and emission reduction, and even the achievement of national "dual carbon" targets. Therefore, there is an urgent need for a turbine unit and thermal system that can maintain high cycle efficiency under medium and low load conditions to solve the current problem. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a full-load high-efficiency steam turbine unit, thermal system and operation method, which is mainly used to solve the problems of low operating efficiency and poor regulation capacity of coal-fired power units under medium and low loads when participating in deep peak shaving.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a full-load high-efficiency steam turbine unit, including a working cylinder body, wherein the working cylinder body is any one of a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder, and a regulating stage is provided in the working cylinder body. The regulating stage is provided with at least two steam passages in a radial direction. At least one regulating valve for controlling the on / off of steam flow is connected to the front end of the steam passages. At least one pressure stage is provided in at least one of the steam passages, and each pressure stage consists of a stationary blade plate located at the front end and a moving blade plate located at the rear end.

[0008] Furthermore, at least one of the steam passages may be provided without a stationary blade grid or with a stationary blade grid having a constant axial flow area, while also without a moving blade grid or with a moving blade grid having no reaction degree.

[0009] Furthermore, at least one pair of stator vanes in adjacent steam passages are radially connected. The radially connected stator vanes are defined as a stator vane pair. The stator vane pair forms a circumferentially extending annular stator vane isolation band at the connection point. The annular stator vane isolation band is connected to the end of the partition wall between adjacent steam passages.

[0010] Furthermore, the stationary blades extend directly to the innermost steam passage or through a partition to the innermost steam passage, and the partition has a first steam vent hole in the flow area corresponding to each steam passage.

[0011] Furthermore, at least one pair of moving blades in adjacent steam passages are radially connected, and the radially connected moving blades are defined as a moving blade pair, which forms a circumferentially extending annular moving blade isolation zone at the connection point.

[0012] Furthermore, one of the moving blades near the inner side of the moving blade pair is directly fixed to the turbine hub or fixed to the turbine hub via a wheel disc, and the wheel disc has a second steam vent hole in the flow area corresponding to each steam passage.

[0013] Furthermore, there is a fitting gap between the annular moving blade grid isolation strip and the annular stationary blade grid isolation strip or the end of the partition wall, and a radial steam seal assembly is provided in the fitting gap.

[0014] Furthermore, the number of pressure stages in any one of the steam passages is not less than the number of pressure stages in any one of the steam passages located outside it.

[0015] Furthermore, the steam flow capacity of the steam channel gradually decreases from the outside to the inside.

[0016] Furthermore, at least one of the steam passages employs a full-circuit steam intake method.

[0017] Secondly, the present invention provides a full-load high-efficiency thermal system, including a boiler and the above-mentioned full-load high-efficiency steam turbine unit, wherein the working cylinder is a high-pressure cylinder, the boiler is connected to the steam passages one by one through a pipeline system, the pipeline system is provided with a main steam valve for controlling the on and off of the main steam flow of the boiler, and at least one regulating valve is provided between the main steam valve and each steam passage.

[0018] Furthermore, the pipeline system includes a main steam pipeline and at least one branch steam pipeline network. The main steam valve is located on the main steam pipeline, and the branch steam pipeline network consists of several branch steam pipelines, each of which is equipped with a regulating valve.

[0019] Furthermore, it also includes a regenerative system, which includes an adjustable heater. The regulating stage is connected to the adjustable heater via an extraction pipe, and the extraction pipe is equipped with an adjusting valve assembly. The adjustable heater is connected to the boiler.

[0020] Thirdly, the present invention provides a method for operating a full-load high-efficiency thermal system, comprising the following steps: sorting the steam flow capacity of each steam channel from largest to smallest, and sequentially determining the first steam channel, the second steam channel, ... the nth steam channel;

[0021] The operating load of the thermal system is divided into m load intervals, and each load interval is associated with one or more steam channels.

[0022] Based on the current operating load rate of the thermal system or the set target load rate, determine the target load range that the thermal system needs to enter, and switch to the steam channel corresponding to the target load range.

[0023] Furthermore, when the thermal system is being loaded, the final steam channel to be switched to is determined based on the load increase rate or target load rate requirement;

[0024] Directly open the final steam passage, or;

[0025] If there are other intermediate steam channels between the final steam channel and the current steam channel, the intermediate steam channels shall be opened sequentially or simultaneously starting from the current steam channel until the final steam channel is opened.

[0026] Determine if the current load has reached the set value. If it has, gradually shut down all steam passages except the final steam passage.

[0027] Furthermore, when the thermal system is being deloaded, the final steam channel to which it needs to be switched is determined based on the required deload rate.

[0028] Gradually close the regulating valve corresponding to the current steam passage;

[0029] Determine if the current load has reached the set value. If it has, gradually open the regulating valve corresponding to the final steam channel and close the regulating valve corresponding to the current steam channel.

[0030] Furthermore, when the load rate of the thermal system is lower than X% of the rated load, the gas regulating valve assembly is opened to input the steam in the regulating stage into the adjustable heater.

[0031] Furthermore, the boiler flue temperature is detected. If the boiler flue temperature is lower than the set temperature value, the gas regulating valve assembly is opened. By controlling the opening degree of the gas regulating valve assembly, the boiler flue temperature is adjusted to be higher than the set temperature value.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] At least two steam passages are radially arranged in the regulating stage at the front end of the high-pressure cylinder. When the thermal system is in different load ranges, it can switch to the corresponding steam passage for operation. By utilizing the different steam flow capacities between different steam passages and the different number of pressure stages they are equipped with, it can adapt to different load conditions and ensure higher cycle efficiency and lower system energy consumption under medium and low loads.

[0034] The main steam valve and regulating valves installed in the pipeline system are used to control the opening and closing of each steam passage. In addition, by setting up a multi-level branch steam network, a smooth transition can be achieved when switching between different steam passages, avoiding sudden changes in steam flow.

[0035] Under low and medium load conditions, the boiler flue temperature is low, which may not meet the denitrification requirements. By leading an extraction pipe from the end of the regulating stage and connecting it to an adjustable heater, the water temperature at the boiler inlet can be increased. The flue temperature at the denitrification point can be adjusted according to actual needs to meet the denitrification requirements.

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0037] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0038] Figure 1 This is a half-section schematic diagram of a full-load high-efficiency steam turbine unit according to the present invention.

[0039] Figure 2 This is an overall schematic diagram of a full-load high-efficiency thermal system according to the present invention.

[0040] Figure 3 This is a schematic diagram of a piping system in one implementation method.

[0041] Figure 4 This is a schematic diagram of a piping system in another implementation method. Detailed Implementation

[0042] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0044] In the description of this invention, when a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other devices without an intermediary device, or it may not be directly connected to the other devices but may have an intermediary device.

[0045] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0046] Firstly, referring to Figure 1This embodiment discloses a full-load high-efficiency steam turbine unit, including a working cylinder 2, which is any one of a high-pressure cylinder 4, an intermediate-pressure cylinder, and a low-pressure cylinder. The working cylinder 2 is provided with a regulating stage 6, and the regulating stage 6 is provided with at least two steam passages 7 arranged radially. The front end of the steam passage 7 is connected to at least one regulating valve 51 for controlling the on / off of steam flow. At least one pressure stage is provided in at least one steam passage 7. Each pressure stage consists of a stationary vane 8 located at the front end and a moving vane 9 located at the rear end. The stationary vane 8 consists of multiple stationary vanes arranged circumferentially, and the moving vane 9 consists of multiple moving vanes arranged circumferentially. A pressure stage is formed by two stationary vanes 8 and two moving vanes 9 arranged one in front and one behind. The pressure stage performs work in response to the main steam generated from the boiler 1.

[0047] It should be noted that the working cylinders in the steam turbine unit can be high-pressure cylinders, intermediate-pressure cylinders, and low-pressure cylinders. All of the high-pressure, intermediate-pressure, and low-pressure cylinders can be equipped with regulating stages with steam passages. Therefore, it should be considered that any one or more working cylinders equipped with regulating stages with steam passages are within the scope of protection claimed in this embodiment, and will not be described in detail here.

[0048] Each steam passage 7 has a corresponding regulating valve 51 that controls the flow of steam. It should be noted that one regulating valve 51 can control one steam passage 7, or one regulating valve 51 can control two or more steam passages 7, or multiple regulating valves 51 can control one steam passage 7, or a combination of the above methods.

[0049] Furthermore, each steam channel 7 has at least two configuration parameters: the flow area of ​​the steam channel 7 and the number of pressure stages set within the steam channel 7. The flow area of ​​each steam channel 7 may be the same or different, and the number of pressure stages set within each steam channel 7 may also be the same or different. Under medium and low load conditions, the inlet of regulating stage 6 is close to the rated main steam pressure, while the pressure of each stage after regulating stage 6 drops significantly. Therefore, a large ideal enthalpy drop is formed at the inlet and outlet of regulating stage 6. In order to improve the cycle efficiency under medium and low load conditions, it is necessary to make full use of the enthalpy drop in this region of regulating stage 6. Therefore, different steam channels 7 are configured with different enthalpy drop handling capabilities. There are many ways to regulate this. For example, while ensuring that the flow area of ​​each steam channel 7 is the same, the number of pressure stages of each steam channel 7 can be changed, or while ensuring that the number of pressure stages of each steam channel 7 is the same, the flow area of ​​each steam channel 7 can be changed, or the number of pressure stages and the flow area of ​​the steam channels 7 can be changed at the same time, so that one or more steam channels 7 are more suitable for operation in a specific load range. It should be noted that under a specific load, one steam channel 7 can be turned on or multiple steam channels 7 can be turned on. There is no restriction here.

[0050] In this embodiment, the steam passage 7 closer to the internal axis has more pressure stages. When the load condition changes, the corresponding steam passage 7 can be switched by controlling the regulating valve 51. That is, the lower the load, the more pressure stages the steam passage 7 has, making full use of the enthalpy drop under medium and low load conditions to improve cycle efficiency and reduce system energy consumption.

[0051] Of course, in addition to setting different numbers of pressure stages in multiple steam channels 7, different flow areas can also be set to increase the pressure at the outlet of the regulating stage 6 and increase the intake pressure of the high-pressure cylinder 4.

[0052] In some embodiments, at least one steam passage 7 is provided without a stationary vane 8 or with a stationary vane 8 having a constant axial flow area, and at the same time, it is provided without a moving vane 9 or with a moving vane 9 without reaction degree. That is, there is no pressure stage capable of doing work in such a steam passage 7. The purpose of this design is that when the unit is running under full / high load conditions, the regulating stage 6 does not need to participate in the regulating work, and the main steam is directly passed to the high-pressure cylinder 4 to do work, so as to improve the operating efficiency under full / high load conditions.

[0053] In some embodiments, a partition wall is provided between adjacent steam passages 7 to prevent cross-flow of gas between different steam passages 7. The partition wall extending along the steam flow direction is shorter the closer it is to the inner side, and there is a step difference between two adjacent partition walls. At least one pair of stationary vanes 8 in adjacent steam passages 7 are connected radially. A radially connected pair of stationary vanes 8 is defined as a stationary vane pair. A stationary vane pair spans two steam passages 7 simultaneously. At the connection of the two stationary vanes 8, the stationary vane pair forms a circumferentially extending annular stationary vane isolation zone 10, which is used to separate different steam passages 7. The steam is fed through an annular stationary blade isolation strip 10 connected to the end of the corresponding partition wall. Since the stationary blades are stationary, to improve their fixing strength under steam impact, two radially adjacent stationary blade grids 8 are connected by the annular stationary blade isolation strip 10 at the step difference between two adjacent partition walls. The annular stationary blade isolation strip 10 is then fixed to the corresponding partition wall. It should be understood that the annular stationary blade isolation strip 10 can be part of the end structure of the partition wall or a separate component. This component connects two stationary blade grids 8 in both the upper and lower radial directions and connects to the end of the partition wall in the axial direction. Furthermore, each steam passage 7 is opened in the inner cylinder 11 of the turbine, forming multiple partition walls within the inner cylinder 11. The annular stationary blade isolation strip 10 is thus fixed to the inner cylinder 11 of the turbine.

[0054] In one implementation, the stationary vane 8 in the innermost steam passage can extend directly into the innermost steam passage 7. If there is only one pressure stage in the other steam passages besides the innermost one, the stationary vane of this pressure stage and the stationary vane of the last pressure stage in the innermost steam passage form a stationary vane pair. If there are multiple pressure stages in the other steam passages, the stationary vanes of the second and subsequent pressure stages, except for the first pressure stage, can extend to the innermost steam passage 7 through the partition 16. The partition 16 ensures the stability of the bottom of the stationary vane 8. At the same time, the partition 16 has a first steam vent in the flow area corresponding to each steam passage 7 to allow steam to flow. The function of this first steam vent is only for ventilation and does not have the function of doing work. Of course, the stationary vanes of the second and subsequent pressure stages can be a single stationary vane, or they can form a stationary vane pair with the stationary vanes of the adjacent steam passages. Alternatively, they can be without the partition 16, and the stationary vane body can extend or not extend. In embodiments where the stationary blades extend directly or through a diaphragm to the innermost steam passage 7, a steam seal can be provided at the bottom of the stationary blades 8 or the diaphragm 16 to ensure a seal between them and the turbine hub 13. Similarly, at the connection between the stationary blades 8 and the diaphragm 16, there may be a corresponding annular moving blade isolation strip 14 or a wheel 12 in space, so a steam seal assembly must also be provided in the dynamic-static gap.

[0055] Furthermore, the radial projections of the two stator blades 8 that constitute a stator blade pair overlap each other. The two stator blades 8 have the same shape because, considering that when switching steam passage 7, the unit load changes, it is often necessary to switch from one stator blade pair to the other. In order to ensure smooth switching and reduce the impact of unit vibration, noise and other factors caused by changes in load and / or pressure level and / or flow area, the two stator blades 8 on the stator blade pair are designed with the same shape.

[0056] In some embodiments, at least one pair of moving blades 9 in adjacent steam passages 7 are connected radially. A pair of moving blades 9 connected radially is defined as a pair of moving blades 9. A pair of moving blades 9 spans two steam passages 7 at the same time. The pair of moving blades 9 forms an annular moving blade isolation band 14 extending circumferentially at the connection of the two moving blades 9. The annular moving blade isolation band 14 is used to connect the upper and lower moving blades 9, which has the function of strengthening the connection and isolating the steam in different steam passages 7.

[0057] In one implementation, for the innermost pair of moving blades, one of the moving blades 9 closest to the innermost side is directly fixed to the hub 13 of the turbine unit 2; while for the remaining pairs of moving blades, one of the moving blades 9 closest to the innermost side is fixed to the hub 13 of the turbine unit 2 via a wheel 12. The wheel 12 is provided with a fixing groove, and the inner moving blade 9 is fixed in this fixing groove. The wheel 12 serves two purposes: firstly, it transmits force by connecting the moving blade 9 to the hub 13; secondly, the wheel 12 has a second steam vent 17 in the flow area corresponding to each steam passage 7. The size and position of the second steam vent 17 correspond to the first steam vent, and it can also serve to circulate steam.

[0058] Similarly, going a step further, the radial projections of the two moving blade grids 9 that constitute a moving blade grid pair overlap each other, and the principle of their arrangement is the same as that of the stationary blade grid 8, which will not be repeated here.

[0059] In one implementation, the stationary vane 8 and moving vane 9 that make up a pressure stage belong to the same stationary vane pair and moving vane pair, respectively, which span the same steam passage 7. Since the stationary vane pair and moving vane pair will span at least two steam passages 7 at the same time, and the pressure stage is composed of a stationary vane 8 located at the front end and a moving vane 9 located at the rear end, for the stationary vane 8 and moving vane 9 in the same steam passage 7 of the stationary vane pair and moving vane pair, a pressure stage is formed under the condition that the stationary vane 8 is in front and the moving vane 9 is behind. This avoids the stationary vane 8 and moving vane 9 in the same steam passage 7 of the stationary vane pair and moving vane pair that span different steam passages 7 from forming a pressure stage, and avoids the potential for operational imbalance and impact on adjacent steam passages 7 during the operation of the pressure stage.

[0060] In this embodiment, there is a fitting gap between the annular moving blade isolation strip 14 and the annular stationary blade isolation strip 10 or the end of the partition wall. A radial steam seal assembly 15 is provided in the fitting gap. This means that the annular stationary blade isolation strip 10 and the end of the partition wall are stationary structural components. Regardless of the connection relationship between the annular stationary blade isolation strip 10 and the end of the partition wall, there is a fitting gap between the annular moving blade isolation strip 14 and at least one of the structural components. In order to prevent steam from crossing between different steam channels 7 and affecting the normal flow of air in the corresponding flow channel, a radial steam seal assembly 15 is provided in the fitting gap to achieve a sealed connection between the annular moving blade isolation strip 14 and the annular stationary blade isolation strip 10 or the end of the partition wall.

[0061] In this embodiment, the number of pressure stages in any steam passage 7 is not less than the number of pressure stages in any steam passage 7 located outside it. Preferably, the number of pressure stages in the steam passage 7 increases from the outside to the inside. For example, four steam passages 7 are arranged sequentially from the outside to the inside. The outermost steam passage 7 has no pressure stages, the next outermost steam passage 7 has one pressure stage, the next innermost steam passage 7 has two pressure stages, and the innermost steam passage 7 has three pressure stages. Furthermore, in the last pressure stage of the innermost steam passage 7, the stationary blade pair and the moving blade pair to which the stationary blade 8 and the moving blade 9 belong are also located in the next innermost steam passage 7. The other stationary blade 8 and moving blade 9 of this stationary blade pair and moving blade pair constitute the first pressure stage in the next innermost steam passage 7. The situation of the remaining steam passages 7 and pressure stages can be referred to. Figure 1 .

[0062] In one implementation, the steam flow capacity of the steam passage 7 gradually decreases from the outside to the inside; in another implementation, the steam flow capacity of the steam passage 7 can also be the same for all of them.

[0063] Preferably, at least one steam passage 7 adopts a full-circuit steam intake method.

[0064] Secondly, referring to Figure 2 This embodiment provides a full-load high-efficiency thermal system, including a boiler 1 and a full-load high-efficiency steam turbine unit as described in the above embodiment. The working cylinder 2 is a high-pressure cylinder 4. The boiler 1 is connected to the steam passages 7 one by one through a pipeline system. The pipeline system is equipped with a main steam valve 5 for controlling the on / off flow of the main steam of the boiler 1. At least one regulating valve 51 is provided between the main steam valve 5 and each steam passage 7. The main steam valve 5 is used to control the on / off flow of the main steam at the outlet of the boiler 1, while the regulating valve 51 is used to control the on / off flow of one or more corresponding steam passages 7. Of course, a regulating valve 51 that can control the flow ratio can also be adopted, and the steam flow rate can be changed by controlling the opening of the regulating valve 51.

[0065] It should be noted that in order to achieve the operation switching between steam channels 7, there are many ways to correspond the regulating valve 51 to the steam channel 7. These correspondences are all achieved by the pipeline system. More specifically, the pipeline system includes a main steam pipeline and at least one branch steam network. The main steam valve 5 is located on the main steam pipeline, and the branch steam network consists of several branch steam pipelines. Each branch steam pipeline is equipped with a regulating valve 51.

[0066] Reference Figure 3 As one implementation method, a one-to-many approach is adopted, with one main steam pipeline paired with a primary branch steam pipeline network. The number of branch steam pipelines is equal to the number of steam channels 7. One regulating valve 51 directly controls one steam channel 7, and there is only one regulating valve 51 between the steam channel 7 and the main steam valve 5.

[0067] Reference Figure 4 As another implementation method, a "one-to-many" approach is adopted, with one main steam pipeline connected to two levels of branch steam networks. That is, the main steam pipeline is directly connected to the first-level branch steam network, and the first-level branch steam network is then directly connected to the second-level branch steam network. In an embodiment with four steam channels 7, the first-level branch steam network has three branch gas pipelines, and the second-level branch steam network has four branch gas pipelines. Each branch gas pipeline in the first-level branch steam network is simultaneously connected to two branch gas pipelines in the second-level branch steam network. The advantage of this arrangement is that when it is necessary to switch and adjust across steam channels 7, the intermediate steam channel 7 can play a transitional role, providing a transitional phase.

[0068] Additionally, if the working cylinder 2 is an intermediate-pressure cylinder, a regulating stage with a steam passage is installed in the intermediate-pressure cylinder. This regulating stage is connected to the reheated pipeline in the boiler. Similarly, the connection relationship between the reheated pipeline and the regulating stage of the intermediate-pressure cylinder can be referred to the connection relationship between the main steam pipeline of the boiler and the regulating stage of the high-pressure cylinder. The same applies if the working cylinder 2 is a low-pressure cylinder. These details will not be elaborated here.

[0069] Reference Figure 2 In some embodiments, a regenerative system 3 is also included, which includes an adjustable heater 19. The end of the regulating stage 6 is connected to the adjustable heater 19 via an extraction pipe, which is typically connected after the pressure stage of each steam passage 7. An air regulating valve assembly 18 is provided on the extraction pipe, which can adjust the opening and closing of the extraction pipe and its flow rate. The adjustable heater 19 is connected to the boiler 1. The purpose of this is that when the boiler 1 is under medium and low load, the flue gas temperature is low, which may not meet the denitrification requirements. By leading an extraction pipe from the end of the regulating stage 6 to the adjustable heater 19, the water temperature at the inlet of the boiler 1 is increased, and the flue gas temperature at the denitrification point is adjusted according to actual needs to meet the denitrification requirements.

[0070] Thirdly, this embodiment provides a method for operating a full-load high-efficiency thermal system, including the following steps:

[0071] S1: Sort the steam flow capacity of each steam channel 7 from largest to smallest, and determine the first steam channel, the second steam channel, ... the nth steam channel in sequence. It should be noted that the steam flow capacity can be defined based on the flow area of ​​the steam channel 7, or based on the number of pressure stages in the steam channel 7, or a combination of the above two, or other situations. In short, the purpose of this sorting is to plan the classification of steam handling capacity of each steam channel 7 in advance, so as to adapt to the operating conditions under different loads.

[0072] S2: Divide the operating load of the thermal system into m load intervals, and associate each load interval with one or more steam channels 7. It should be noted that the number of load intervals can be the same as the number of steam channels 7. In this case, there can be a one-to-one correspondence between a load interval and a steam channel 7, or there can be a case where a load interval corresponds to at least one steam channel 7. Of course, the number of load intervals can also be different from the number of steam channels 7. Correspondingly, there can be multiple load intervals bound to steam channels 7.

[0073] In this embodiment, n=4, meaning there are four steam channels 7 arranged sequentially from the outside to the inside. The outermost steam channel has no stationary vane 8 or has a stationary vane 8 with a constant axial flow area, and also has no moving vane 9 or has a moving vane 9 with no reaction degree. The steam flow capacity of this steam channel is considered infinite, so the outermost steam channel has the largest steam flow capacity and is defined as the first steam channel. The next outermost steam channel has one pressure stage, the next innermost steam channel has two pressure stages, and the innermost steam channel has three pressure stages. Since when a steam channel 7 contains one or more pressure stages simultaneously, in this... With the regulating valve 51 of steam passage 7 fully open, the main steam parameters after the main steam valve 5 are used as the rated parameters as the inlet conditions of steam passage 7. The back pressure of steam passage 7 is adjusted, and the flow rate when a certain pressure stage reaches the critical state is the maximum flow rate. Based on this, the flow capacity of the remaining 3 steam passages is sorted from largest to smallest, and the steam passages from the outside to the inside are defined as the second steam passage, the third steam passage, and the fourth steam passage. In addition, as an implementation method, the throat area of ​​the nozzle of each pressure stage is the same, so the flow capacity of the three innermost stages is the smallest, and the flow capacity of the steam passages outwards increases sequentially.

[0074] More specifically, four load ranges are set, i.e., m=n=4, namely [100%, 80%], [80%, 60%], [60%, 40%] and [40%, 20%]. The [100%, 80%] load range corresponds to the first steam channel, the [80%, 60%] load range corresponds to the second steam channel, the [60%, 40%] load range corresponds to the third steam channel, and the [40%, 20%] load range corresponds to the fourth steam channel.

[0075] S3: Based on the current operating load rate of the thermal system or the set target load rate, determine the target load range that the thermal system needs to enter, and switch to the steam channel corresponding to the target load range. If the load range does not change, maintain the current steam channel operation. If the load range changes, switch from the current steam channel to the steam channel corresponding to the target load range.

[0076] As can be seen, the optimal steam flow capacity changes with the unit load. By automatically reconfiguring the thermal system state and switching to different steam channels or groups of steam channels, the reconfigured steam flow capacity is better matched to the current load rate. To achieve this, there are various combinations of load ranges and steam channels. The most basic is one load range corresponding to one steam channel, but it is also possible for one load range to correspond to two or more steam channels. The reason for switching steam channels can be passive or active. That is, the steam channel can switch when the unit load changes; or a target load rate can be set manually, and while other devices in the thermal system are adjusting, steam channel 7 is also actively switching.

[0077] In some embodiments, when the load of the thermal system is increased, the final steam channel to which it needs to be switched is determined according to the load increase rate or target load rate requirement. It should be noted that, whether the steam channel 7 is switched actively or passively, as long as the triggering condition for switching the steam channel 7 is met, a parameter of the load increase rate or target load rate requirement will be generated, such as whether it is necessary to switch from the fourth steam channel to the second steam channel or to the third steam channel, which will form a final steam channel.

[0078] Once the final steam channel is determined, it can be opened directly. This approach aims to improve the load adjustment rate. After opening the final steam channel, other factors are then used to stabilize the load. This method is a static adjustment method.

[0079] Alternatively, this approach can be adopted: if there are other intermediate steam channels between the final steam channel and the current steam channel, then the intermediate steam channels are opened sequentially or simultaneously, starting from the current steam channel, until the final steam channel is opened. This means that if it is necessary to switch from the fourth steam channel to the second steam channel, and there is a third steam channel in between, then during the switching process, the third steam channel needs to be opened first as a transition, and the second steam channel is opened last. It can be seen that this method is a dynamic adjustment method, and the opening status of each steam channel will change during the load increase process.

[0080] During the switching of steam channels, it is determined whether the current load has reached the set value. If it has, and the load is stabilized by adjusting boiler 1, then no further steam channels are opened. Instead, all steam channels except the final steam channel are gradually closed. That is, the fourth steam channel is closed first, followed by the third steam channel. It should be noted that when gradually closing the other steam channels, the steam channels are closed in ascending order of steam flow capacity. Of course, they can also be closed simultaneously, but the closure process must be slow. In addition, if a dynamic adjustment occurs, such as when switching from the fourth steam channel to the second steam channel, and the load has already reached the set value when the third steam channel is opened, then the third steam channel is used, and the second steam channel is not opened. It can be seen that in some implementations, whether the current load has reached the set value is the first priority for determining the opening of the steam channel.

[0081] Additionally, during the transition phase, i.e. when the third steam channel is opened, a certain proportion of the third steam channel can be opened first, and a certain proportion of the fourth steam channel can be closed. When the third steam channel is opened to the set proportion or when the fourth steam channel is closed to a certain proportion, the second steam channel is then opened. The sum of the openings of the three steam channels can be controlled according to a certain functional relationship or a certain value, so that the second steam channel is fully opened and the fourth and third steam channels are closed accordingly.

[0082] In some embodiments, when the thermal system is reducing its load, the final steam channel to which it needs to switch is determined according to the load reduction rate requirement. It should be noted that, whether the steam channel is switched actively or passively, as long as the triggering condition for switching the steam channel 7 is met, a parameter for the load reduction rate requirement will be generated, such as whether it is necessary to switch from the second steam channel to the third steam channel or to the fourth steam channel, which will form a final steam channel.

[0083] Gradually close the regulating valve 51 corresponding to the current steam passage;

[0084] Determine whether the current load has reached the set value. If it has reached and the load is stabilized by adjusting Boiler 1, gradually open the regulating valve 51 corresponding to the final steam channel and close the regulating valve 51 corresponding to the current steam channel.

[0085] More specifically, if it is necessary to switch from the second steam channel to the fourth steam channel, first, according to the requirement of the load reduction rate in the dispatching, gradually close the regulating valve 51 of the second channel. When the load reaches the set value, while stabilizing the load by adjusting Boiler 1, gradually open the regulating valve 51 of the fourth steam channel and slowly close the regulating valve 51 of the second steam channel.

[0086] In some embodiments, when the load rate of the thermal system is lower than X% of the rated load, open the gas regulating valve assembly 18 and input the steam in the regulating stage 6 into the adjustable heater 19, where 20% < x% < 60%. Preferably, according to system optimization, for a conventional subcritical unit, x% can be determined to be about 40% through calculation verification. That is, when the unit load rate is lower than the set value, the steam in the regulating stage 6 needs to be refluxed to the adjustable heater 19 and then flow back to Boiler 1.

[0087] In some embodiments, detect the flue gas temperature of Boiler 1. If the flue gas temperature of Boiler satisfies the脱硝需求, open the gas regulating valve assembly 18 and adjust the reflux amount of the steam extracted from the regulating stage 6 by controlling the opening degree of the gas regulating valve assembly 18, thereby adjusting the flue gas temperature of Boiler 1 to be higher than the set temperature value.

[0088] In summary, compared with the prior art, the above embodiments provide a full-load high-efficiency steam turbine unit, a thermal system and an operation method. At least two steam channels 7 are arranged radially in the regulating stage 6 at the front end of the high-pressure cylinder 4. When the thermal system is in different load intervals, it can be switched to the corresponding steam channel 7 for operation, and the different steam flow capacities between different steam channels 7 and the different numbers of pressure stages configured therein are utilized to adapt to different load conditions, ensuring a relatively high cycle efficiency and low system energy consumption at medium and low loads;

[0089] The on-off of each steam channel 7 is controlled by the main steam valve 5 and the regulating valve 51 arranged in the pipeline system. By setting up a multi-stage branch steam pipe network, a smooth transition can be achieved when switching between different steam channels 7, avoiding sudden changes in the steam flow rate;

[0090] At medium and low loads, the flue gas temperature of Boiler 1 is relatively low, and there is a risk of not meeting the denitration requirement. By leading out an extraction pipeline at the end of the regulating stage 6 and connecting it to the adjustable heater 19, the water temperature at the inlet end of Boiler 1 is increased, and the flue gas temperature at the denitration location is adjusted according to actual needs to meet the denitration requirement.

[0091] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A full-load high-efficiency steam turbine unit, comprising a power cylinder body, wherein the power cylinder body is any one of a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder, and wherein the power cylinder body is provided with an adjusting stage, characterized in that, The regulating stage is provided with at least two steam passages in the radial direction. The front end of each steam passage is connected to at least one regulating valve for controlling the flow of steam. At least one pressure stage is provided in at least one of the steam passages. Each pressure stage consists of a stationary vane at the front end and a moving vane at the rear end. Each of the steam passages has at least two configuration parameters: the flow area of ​​the steam passage and the number of pressure stages set within the steam passage. The number of pressure stages in any one of the steam passages is not less than the number of pressure stages in any one of the steam passages located outside it. The steam passages closer to the inner axis have more pressure stages. When the load is low, the system switches to the steam passage with more pressure stages.

2. The full-load high-efficiency steam turbine unit according to claim 1, characterized in that, At least one of the steam passages is provided with either no stationary blades or a stationary blade with a constant axial flow area, and at the same time, no moving blades or a moving blade with no reaction degree is provided.

3. The full-load high-efficiency steam turbine unit according to claim 1, characterized in that, At least one pair of stationary blades in adjacent steam passages are radially connected. The radially connected stationary blades are defined as a stationary blade pair. The stationary blade pair forms a circumferentially extending annular stationary blade isolation band at the connection point. The annular stationary blade isolation band is connected to the end of the partition wall between adjacent steam passages.

4. The full-load high-efficiency steam turbine unit according to claim 1, characterized in that, The stationary blades extend directly to the innermost steam passage or through a partition to the innermost steam passage, and the partition has a first steam vent in the flow area corresponding to each steam passage.

5. A full-load high-efficiency steam turbine unit according to claim 3, characterized in that, At least one pair of moving blades in adjacent steam passages are radially connected. The radially connected moving blades are defined as a moving blade pair, and the moving blade pair forms a circumferentially extending annular moving blade isolation zone at the connection point.

6. A full-load high-efficiency steam turbine unit according to claim 5, characterized in that, One of the moving blades near the inner side of the moving blade pair is directly fixed to the turbine hub or fixed to the turbine hub by a wheel disc, and the wheel disc has a second steam vent in the flow area corresponding to each steam passage.

7. A full-load high-efficiency steam turbine unit according to claim 6, characterized in that, There is a fitting gap between the annular moving blade grid isolation strip and the annular stationary blade grid isolation strip or the end of the partition wall, and a radial steam seal assembly is provided in the fitting gap.

8. A full-load high-efficiency steam turbine unit according to claim 2, characterized in that, The steam flow capacity of the steam passage gradually decreases from the outside to the inside.

9. A full-load high-efficiency steam turbine unit according to any one of claims 1 to 8, characterized in that, At least one of the steam passages employs a full-circumference steam inlet method.

10. A full-load high-efficiency thermal system, characterized in that, The system includes a boiler and a full-load high-efficiency steam turbine unit as described in any one of claims 1 to 9, wherein the working cylinder is a high-pressure cylinder, the boiler is connected to each of the steam passages through a pipeline system, the pipeline system is provided with a main steam valve for controlling the on / off flow of the main steam of the boiler, and at least one regulating valve is provided between the main steam valve and each of the steam passages.

11. A full-load high-efficiency thermal system according to claim 10, characterized in that, The pipeline system includes a main steam pipeline and at least one branch steam pipeline network. The main steam valve is located on the main steam pipeline. The branch steam pipeline network consists of several branch steam pipelines, and each branch steam pipeline is equipped with a regulating valve.

12. The full-load high-efficiency thermal system according to claim 11, characterized in that, It also includes a regenerative system, which includes an adjustable heater. The regulating stage is connected to the adjustable heater via an extraction pipe. An air regulating valve assembly is provided on the extraction pipe. The adjustable heater is connected to the boiler.

13. A method for operating a full-load high-efficiency thermal system, applied to a full-load high-efficiency thermal system as described in any one of claims 10 to 12, characterized in that, Includes the following steps: The steam passages are sorted from largest to smallest according to their steam flow capacity, and the first steam passage, the second steam passage, ..., the nth steam passage are determined in sequence. The operating load of the thermal system is divided into m load intervals, and each load interval is associated with one or more steam channels. Based on the current operating load rate of the thermal system or the set target load rate, determine the target load range that the thermal system needs to enter, and switch to the steam channel corresponding to the target load range.

14. The method for operating a full-load high-efficiency thermal system according to claim 13, characterized in that, When the thermal system is being loaded, the final steam channel to be switched to is determined based on the load increase rate or target load rate requirement. Directly open the final steam passage, or; If there are other intermediate steam channels between the final steam channel and the current steam channel, the intermediate steam channels shall be opened sequentially or simultaneously starting from the current steam channel until the final steam channel is opened. Determine if the current load has reached the set value. If it has, gradually shut down all steam passages except the final steam passage.

15. The method for operating a full-load high-efficiency thermal system according to claim 14, characterized in that, When the thermal system is being reduced in load, the final steam channel to which it needs to be switched is determined based on the required load reduction rate. Gradually close the regulating valve corresponding to the current steam passage; Determine if the current load has reached the set value. If it has, gradually open the regulating valve corresponding to the final steam channel and close the regulating valve corresponding to the current steam channel.

16. The method for operating a full-load high-efficiency thermal system according to any one of claims 13 to 15, characterized in that, When the load rate of the thermal system is lower than the set rated load, the gas regulating valve assembly is opened to input the steam in the regulating stage into the adjustable heater.

17. The method for operating a full-load high-efficiency thermal system according to any one of claims 13 to 15, characterized in that, The boiler flue temperature is detected. If the boiler flue temperature is lower than the set temperature value, the gas regulating valve assembly is opened. By controlling the opening degree of the gas regulating valve assembly, the boiler flue temperature is adjusted to be higher than the set temperature value.

Images