Transformation method of medium-pressure main steam regulating valve group for steam extraction of steam turbine of combined cycle unit, medium-pressure main steam regulating valve group and use method of medium-pressure main steam regulating valve group

Abstract

The invention discloses a transformation method of a medium-pressure main steam regulating valve group for steam extraction of a steam turbine of a combined cycle unit, the medium-pressure main steam regulating valve group and a use method of the medium-pressure main steam regulating valve group, and the transformation method comprises the following steps: S1, during transformation, keeping the steam inlet center line of an original medium-pressure main steam valve and a valve foundation pit unchanged; s2, the original medium-pressure regulating valve is split into two medium-pressure regulating valves connected in parallel, and steam inlets of the two medium-pressure regulating valves are combined into a whole and are welded with the original medium-pressure main steam valve to form an integrated structure; s3, the two medium-pressure regulating valves are configured into a large medium-pressure regulating valve and a small medium-pressure regulating valve, and the steam outlet center lines of the medium-pressure regulating valves are symmetrically distributed on the two sides of the steam outlet center line of the original medium-pressure regulating valve; s4, integrally moving the medium-pressure main steam regulating valve group to the steam inlet side of the original medium-pressure main steam valve; and S5, steam outlets of the two medium-pressure adjusting valves in the step S3 are connected through a special-shaped tee joint, and a steam output connector of the special-shaped tee joint is connected with the original medium-pressure steam guide pipe through a bent pipe. The steam supply parameter timing valve is simple to modify and low in modifying cost, and the adjusting performance of the steam supply parameter timing valve is improved.

Description

Technical Field

[0001] The present invention belongs to the field of cogeneration of gas-steam combined cycle units, and specifically provides a method for modifying a medium-pressure main steam regulating valve group for extracting steam from a steam turbine of a combined cycle unit, a medium-pressure main steam regulating valve group, and a method for using the same. Background Art

[0002] Gas-steam combined cycle units located in industrial parks are responsible for industrial steam extraction. External heat supply typically involves extracting steam from the main engine, using medium-pressure extraction from the main engine in combination with a gas-fired boiler, or using a gas-fired boiler after the main engine is shut down. As industrial parks continue to grow, steam consumption will increase significantly, and existing steam supply capacity will be unable to meet this growth.

[0003] To improve the steam supply capacity of gas-steam combined cycle units, a method for modifying the medium-pressure main steam control valve used in the turbine extraction of combined cycle units was proposed, with the goal of increasing the steam supply capacity of the steam turbine. By optimizing the structure of the medium-pressure control valve, the control performance and stability were improved, meeting the steam supply pressure and flow rate requirements. This method safely and efficiently increases the turbine's medium-pressure extraction steam flow rate for external heat supply, thereby increasing the unit's steam supply capacity. This modification improves the steam supply capacity of the steam turbine without modifying the gas boiler, meeting the growing steam demand of heat users with minimal investment, and demonstrates excellent practicality and economic benefits. Summary of the Invention

[0004] The object of the present invention is to provide a method for modifying a medium-pressure main steam regulating valve group for steam turbine extraction of a combined cycle unit, a medium-pressure main steam regulating valve group and a method of using the same, which are simple to modify and have low modification costs, and can improve the adjustment performance and safety of the valve during steam supply parameter adjustment, thereby achieving the purpose of increasing the steam turbine extraction capacity.

[0005] The technical objectives of the present invention are achieved through the following technical solutions: A method for modifying a medium-pressure main steam regulating valve group for extracting steam from a steam turbine of a combined cycle unit comprises the following steps: S1. During the renovation, the original steam inlet centerline and valve foundation pit of the medium-pressure main steam valve shall remain unchanged; S2. Split the original medium-pressure regulating valve into two parallel medium-pressure regulating valves, combine the steam inlets of the two medium-pressure regulating valves into one, and weld them together with the original medium-pressure main steam valve to form an integrated structure; S3. The two medium-pressure regulating valves are configured as one large and one small, with their steam outlet centerlines symmetrically distributed on both sides of the steam outlet centerline of the original medium-pressure regulating valve; S4. Move the medium-pressure main steam regulating valve group as a whole toward the steam inlet side of the original medium-pressure main steam valve to meet the rooting requirements of the valve support and hanger; S5. Connect the steam outlets of the two medium-pressure regulating valves in step S3 respectively through special-shaped tees, and connect the steam output interface of the special-shaped tee to the original medium-pressure steam pipe through an elbow.

[0006] Preferably, in step S4, the method further includes: Part of the original medium-pressure reheat pipeline is cut to form installation and support space for the medium-pressure main steam regulating valve group.

[0007] Preferably, in step S4, the method further includes: Part of the original medium-pressure steam pipe is cut to leave enough space for the installation of the elbow.

[0008] Preferably, in step S4, the valve support and hanger adopts a split structure corresponding to the two medium-pressure regulating valves, and the lateral size of the valve support and hanger is enlarged.

[0009] Preferably, in step S5, when the elbow is connected to the original medium-pressure steam pipe, on-site adjustment is performed through a straight pipe alignment section with adjustable length to achieve precise alignment welding of the special-shaped tee and the original medium-pressure steam pipe.

[0010] A medium-pressure main steam regulating valve group for extracting steam from a steam turbine of a combined cycle unit is modified using the method for modifying a medium-pressure main steam regulating valve group for extracting steam from a steam turbine of a combined cycle unit as described in the preceding claims, comprising: a medium-pressure main steam valve; The internal valve core is matched with two medium-pressure regulating valves with different diameters, one large and one small, which are arranged in parallel and share a valve housing; the valve housing includes a medium-pressure regulating valve steam inlet connected to the medium-pressure main steam valve and a medium-pressure regulating valve steam outlet respectively matched with the two internal valve cores, and the medium-pressure regulating valve steam outlets are symmetrically distributed along the center line of the medium-pressure regulating valve steam outlets; one end of the medium-pressure regulating valve steam inlet of the valve housing is connected to one end of the steam outlet of the medium-pressure main steam valve and welded into an integral structure.

[0011] Preferably, one end of the medium-pressure regulating valve steam outlet of the valve housing is connected to a special-shaped tee; the two special-shaped tee steam input interfaces of the special-shaped tee are respectively connected to the two medium-pressure regulating valve steam outlets, and the special-shaped tee steam input interface is asymmetric in design; the steam output interface of the special-shaped tee is connected to the original medium-pressure steam pipe through a bend pipe.

[0012] Preferably, the special-shaped tee is a casting.

[0013] A method for using the medium-pressure main steam regulating valve group as described above includes: during heat supply regulation, as the amount of heat supply and steam extraction increases, gradually closing the internal valve core and the large medium-pressure regulating valve with a large diameter to a minimum value to ensure stable steam extraction pressure; If the steam extraction volume continues to increase, gradually close the internal valve core and match the small medium-pressure regulating valve with a small diameter to the allowable opening value to ensure the stability of the steam extraction pressure.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The method for modifying the medium-pressure main steam regulating valve group for combined cycle unit steam turbine extraction, under the premise of the existing valve foundation pit and valve pipeline layout of the power plant, only needs to optimize the overall structure of the medium-pressure main steam regulating valve, the pipeline and support bracket layout, and adaptively modify the valve support bracket and the medium-pressure steam pipe. The scope of modification is relatively small, and basically will not affect the load distribution and structural strength of the reuse foundation. The risk of safe operation after the modification is relatively small, which improves the market competitiveness of the company's steam supply modification products. At the same time, the power plant can obtain the maximum benefit with the least investment. The adoption of this technical measure has the advantages of simple modification, low modification cost, and can improve the adjustment performance and safety of the valve during steam supply parameter adjustment, thereby increasing the steam extraction capacity of the steam turbine.

[0015] 2. The medium-pressure main steam regulating valve group for extracting steam from the steam turbine of a combined cycle unit of the present invention adopts a structure in which a medium-pressure main steam valve and two parallel medium-pressure regulating valves of different sizes share a valve housing, which simplifies the structure of the equipment, reduces the number of parts, and reduces the manufacturing cost and maintenance difficulty. At the same time, since the steam outlet center lines of the two regulating valves are symmetrically distributed, and the valve housing and the medium-pressure main steam valve are welded into an integral structure, the force on the entire valve group is more balanced, the operation is more stable and reliable, the steam flow is smoother, and the risk of energy loss and equipment failure is reduced. The design of the special-shaped tee can effectively collect the steam from the outlets of the two regulating valves, and connect the original medium-pressure steam pipe through a bend pipe, thereby realizing the reasonable distribution and transportation of steam and ensuring the normal operation of the steam system. Its unique structure helps to optimize the flow rate and pressure distribution of steam, and improve the overall performance and efficiency of the system.

[0016] 3. The present invention can increase the opening of the medium-pressure regulating valve and reduce throttling losses while achieving the same steam extraction effect. It can not only improve the operating economy of the unit and reduce the vibration risk of the valve at a small opening, but also effectively reduce the use of gas boilers to supply steam to the outside during multi-unit operation or single-unit operation, thereby improving the economic benefits of the power plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 This is a structural diagram of the original medium-pressure main steam valve and the original medium-pressure regulating valve; Figure 3 yes Figure 1 The structural diagram of the original medium-pressure main steam valve and medium-pressure regulating valve; Figure 4This is a schematic diagram of the arrangement of the medium-pressure main steam regulating valve group, special-shaped tees, elbows, and valve supports and hangers of the present invention; Figure 5 It is a schematic diagram of the cutting positions of the original medium-pressure reheat pipe and the original medium-pressure steam guide pipe of the present invention; Figure 6 yes Figure 1 Schematic diagram of the structure of the special-shaped tee; Reference numerals: 1—original medium-pressure main steam valve; 11—original medium-pressure main steam valve steam inlet centerline; 12—medium-pressure main steam valve steam inlet side; 2—medium-pressure regulating valve; 21—valve housing; 22—center line of steam outlet of medium-pressure regulating valve; 3—valve support and hanger; 4—special-shaped tee; 41—special-shaped tee steam input interface; 5—elbow pipe; 6—straight pipe alignment section; 7—original medium-pressure reheat pipe; 8—original medium-pressure steam pipe; 100—Original medium-pressure regulating valve; 101—Original steam outlet center line of the medium-pressure regulating valve. DETAILED DESCRIPTION

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0020] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. In addition, the terms "first," "second," etc. are used only to distinguish the descriptions and are not to be understood as indicating or implying relative importance.

[0021] Example 1 like Figure 1 — Figure 6 As shown, a method for modifying a medium-pressure main steam regulating valve group for extracting steam from a steam turbine of a combined cycle unit includes the following steps: S1. During the renovation, the original steam inlet centerline 11 of the medium-pressure main steam valve and the valve foundation pit shall remain unchanged; S2. Split the original medium-pressure regulating valve 100 into two parallel medium-pressure regulating valves 2. Combine the steam inlets of the two medium-pressure regulating valves 2 into one and weld them together with the original medium-pressure main steam valve 1 to form an integrated structure. S3. Configure the two medium-pressure regulating valves 2 into one large and one small type, with their steam outlet center lines symmetrically distributed on both sides of the original medium-pressure regulating valve steam outlet center line 101; S4. Move the medium-pressure main steam regulating valve group as a whole to the steam inlet side of the original medium-pressure main steam valve 1 to meet the rooting requirements of the valve support bracket 3; S5. Connect the steam outlets of the two medium-pressure regulating valves 2 in step S3 respectively through the special-shaped tee 4. The steam output interface of the special-shaped tee 4 is connected to the original medium-pressure steam pipe 8 through the elbow 5.

[0022] Given the existing power plant valve pit and valve piping layout, only the overall structure of the medium-pressure main steam regulating valve group, piping, and support and hanger layout need to be optimized. The valve support and hanger 3 and the original medium-pressure steam guide 8 need to be adaptively modified. This modification is relatively small and will have little impact on the load distribution and structural strength of the reused foundation. The post-modification safety operation risk is relatively low, enhancing the market competitiveness of the company's steam supply modification products. At the same time, power plants can achieve maximum returns with minimal investment. This technical measure offers the advantages of simple and low-cost modification, improved valve adjustment performance and safety during steam supply parameter adjustment, and increased turbine extraction capacity.

[0023] In specific implementation, Unit 2 of a certain company is an M701F4 gas-steam combined cycle cogeneration unit equipped with a twin-cylinder, twin-exhaust steam turbine, a reheat, no-afterburning, natural circulation waste heat boiler, and a single-shaft, one-on-one arrangement. The M701F4 gas turbine, designed and manufactured by Mitsubishi Heavy Industries, Japan, is equipped with a twin-cylinder, lower-exhaust TC2F-35.4-inch, high-pressure, intermediate-reheat, twin-cylinder, twin-exhaust condensing steam turbine. The unit's rated heat supply is 111 t / h during operation. To ensure continuous and stable heat supply, two 50 t / h gas-fired boilers and one 75 t / h gas-fired boiler are also installed. With increasing industrial steam consumption in the industrial park where the power plant is located, the unit's steam supply capacity is insufficient. An urgent need exists to increase steam supply capacity through unit steam supply modifications to meet heat user demand.

[0024] Data from the power plant's previous steam extraction operations revealed an average steam supply of 116 t / h. By the end of 2022, the unit's peak daily heat supply reached 195 t / h. Given the unit's adjustable steam extraction capacity of 0 to 214 t / h (including 34 t / h of desuperheating water) under heating conditions, a steam supply modification was completed in 2024.

[0025] like Figure 1 — Figure 6As shown; the steam supply transformation scheme of the medium-pressure main steam regulating valve of the combined cycle unit steam turbine of the present invention is adopted, and the specific implementation steps are as follows: S1. During the renovation, the original steam inlet centerline 11 of the medium-pressure main steam valve and the valve foundation pit shall remain unchanged; This renovation method maintains the original medium-pressure main steam valve inlet centerline 11 and valve foundation pit, maximizing the use of the original equipment installation foundation and layout. This reduces the potential for significant adjustments to the entire unit structure, lowers renovation costs and difficulty, and shortens the renovation period. It offers the advantages of simple renovation and low cost.

[0026] S2. Split the original medium-pressure regulating valve 100 into two parallel medium-pressure regulating valves 2. Combine the steam inlets of the two medium-pressure regulating valves 2 into one, and weld them with the original medium-pressure main steam valve 1 to form an integrated structure.

[0027] In this embodiment, improvements are primarily made to the original medium-pressure regulating valve 100, while retaining the original medium-pressure main steam valve 1. In specific implementations, the original medium-pressure main steam valve 1 can be replaced with a new medium-pressure main steam valve, depending on actual needs. The steam inlet centerline of the new medium-pressure main steam valve aligns with the steam inlet centerline 11 of the original medium-pressure main steam valve 1. One end of the new medium-pressure main steam valve is connected to the medium-pressure regulating valve 2, and the other end is connected to the original medium-pressure reheat pipe 7.

[0028] S3. Configure the two medium-pressure regulating valves 2 into one large and one small type, with their steam outlet center lines symmetrically distributed on both sides of the original medium-pressure regulating valve steam outlet center line 101; In this embodiment, if Figure 1 As shown in Figure 3, compared to before the modification, the number of medium-pressure regulating valves 2 has been increased from one to two. These valves are designed with one large and one small. Specifically, the valve cores are arranged to fit two medium-pressure regulating valves 2, one with a larger diameter and the other with a smaller diameter. The valve core with the larger diameter has high flow capacity, while the valve core with the smaller diameter has the ability to precisely control low flows.

[0029] Specifically, the original medium-pressure regulating valve 100 is split into two parallel medium-pressure regulating valves 2, the steam inlets of the two medium-pressure regulating valves 2 are combined into one, and are welded into an integral structure with the original medium-pressure main steam valve 1; this can not only increase the adjustment range and accuracy of the steam flow, meet the steam flow requirements under different working conditions, but also ensure the tightness and integrity of the valve connection, thereby improving the reliability and stability of the system.

[0030] Configuring a large and a small medium-pressure regulating valve 2, with the steam outlet center lines 22 of the medium-pressure regulating valves symmetrically distributed on both sides of the original medium-pressure regulating valve steam outlet center line 101, helps to optimize the flow distribution of steam, reduce the impact and eddy current of steam in the valve, reduce energy loss, and make the force on the valve group more uniform, thereby extending the service life of the equipment.

[0031] S4. Move the medium-pressure main steam regulating valve group as a whole to the steam inlet side of the original medium-pressure main steam valve 1 to meet the rooting requirements of the valve support bracket 3.

[0032] In this embodiment, the medium-pressure main steam regulating valve group is moved as a whole about 184 mm toward the steam inlet side of the original medium-pressure main steam valve 1 to meet the rooting requirements of the valve support bracket 3.

[0033] like Figure 1-Figure 3 As shown, in this embodiment, the medium-pressure main steam regulating valve group includes the original medium-pressure main steam valve 1 and the medium-pressure regulating valve 2; the medium-pressure main steam regulating valve group is moved as a whole to the steam inlet side 12 of the medium-pressure main steam valve to meet the rooting requirements of the valve support bracket 3, ensure that the valve support bracket 3 can be firmly installed on a reliable supporting structure, avoid valve vibration, deformation and other problems caused by improper installation of the valve support bracket 3, and ensure the safe operation of the valve and the entire pipeline system.

[0034] Furthermore, in step S4, the original medium-pressure reheat pipe 7 is partially cut to form a space for installing and supporting the medium-pressure main steam regulating valve group.

[0035] In this embodiment, if Figure 4 As shown, one end of the original medium-pressure main steam valve 1 is connected to the original medium-pressure reheat pipe 7, and the other end is connected to the medium-pressure regulating valve 2. The original medium-pressure reheat pipe 7 is cut at the end where it connects to the original medium-pressure main steam valve 1. A total of 368 mm of the original medium-pressure reheat pipe 7 is cut to accommodate the installation space and support position of the entire original medium-pressure main steam valve group 1.

[0036] The adoption of this technical measure provides a suitable location and sufficient space for the modified medium-pressure main steam regulating valve group, ensuring the rationality and feasibility of the installation of the medium-pressure main steam regulating valve group. It is also conducive to subsequent maintenance and overhaul work, avoiding problems such as installation difficulties and maintenance inconveniences caused by limited space.

[0037] Furthermore, in step S4 , the original medium-pressure steam conduit 8 is partially cut to leave enough space for the installation of the elbow 5 .

[0038] In this embodiment, if Figure 4 As shown, the cutting position of the original medium-pressure steam pipe 8 is the end where the original medium-pressure steam pipe 8 is connected to the elbow 5; about 184mm of the original medium-pressure steam pipe 8 is cut off to meet the installation space of the elbow 5. This technical measure leaves sufficient installation space for the newly added elbow 5, providing a basic guarantee for the smooth assembly of the entire equipment component and the reasonable connection and matching between the various parts. It avoids installation difficulties and misalignment caused by inconsistent pipe lengths, helps to improve installation efficiency and quality, and ensures that the equipment can be effectively integrated and operated according to the predetermined design plan.

[0039] Furthermore, in step S4, the valve support bracket 3 corresponding to the two medium-pressure regulating valves 2 adopts a split structure, and the lateral size of the valve support bracket 3 is enlarged.

[0040] This technical measure can better adapt to the layout and force characteristics of the two parallel control valves, provide more stable and uniform support force, effectively disperse the weight and pressure of the valves during operation, reduce valve deformation and wear, and increase the service life and operational stability of the valves. At the same time, it also enhances the valve group's ability to adapt to external factors such as pipeline thermal expansion.

[0041] S5. Connect the steam outlets of the two medium-pressure regulating valves 2 in step S3 respectively through the special-shaped tee 4. The steam output interface of the special-shaped tee 4 is connected to the original medium-pressure steam pipe 8 through the elbow 5.

[0042] In this embodiment, the steam outlets of the two medium-pressure regulating valves 2 are combined into one, the original medium-pressure steam pipe 8 is adaptively cut and the pipeline layout is adjusted, and a special-shaped tee 4 and an elbow 5 are added to connect with the original medium-pressure steam pipe 8.

[0043] Furthermore, in step S5 , when the elbow 5 is connected to the original medium-pressure steam pipe 8 , on-site adjustment is performed through the straight pipe alignment section 6 with adjustable length to achieve precise alignment welding of the special-shaped tee 4 and the original medium-pressure steam pipe 8 .

[0044] The use of this technical measure ensures welding quality, avoids problems such as pipeline leakage and stress concentration caused by inaccurate alignment, improves the sealing and safety of the entire system, and also increases the flexibility and convenience of installation, which can better adapt to the complex installation environment and conditions on site.

[0045] During implementation, the unit retrofit achieved its interim steam supply goals. Without external steam extraction from the gas-fired boiler, the combined cycle unit's steam turbine verified adjustable steam extraction from 0 to 136 t / h at 225-450 MW (50%-100%). The current maximum steam extraction rate has reached 180 t / h (due to current user-side steam consumption constraints, this has not reached the maximum design value). Steam supply capacity has been significantly improved during partial load operation. Following the steam supply retrofit, the unit's thrust bearing temperature and vibration performance remained stable, with no pipeline or valve vibration issues reported.

[0046] Example 2 like Figure 1 — Figure 6 As shown, a medium-pressure main steam regulating valve group for extracting steam from a steam turbine of a combined cycle unit is modified using the method for modifying a medium-pressure main steam regulating valve group for extracting steam from a steam turbine of a combined cycle unit in Example 1, comprising: A medium-pressure main steam valve; the medium-pressure main steam valve steam inlet center line of the medium-pressure main steam valve is consistent with the original medium-pressure main steam valve steam inlet center line 11.

[0047] The internal valve core is matched with two medium-pressure regulating valves 2 with a larger and smaller diameters, which are arranged in parallel and share a valve housing 21; the valve housing 21 includes a steam inlet of the medium-pressure regulating valve 2 connected to the medium-pressure main steam valve and a steam outlet of the medium-pressure regulating valve 2 matched with the two internal valve cores respectively, and the steam outlet center lines 22 of the medium-pressure regulating valve 2 steam outlets are symmetrically distributed; one end of the steam inlet of the medium-pressure regulating valve 2 of the valve housing 21 is connected to one end of the steam outlet of the medium-pressure main steam valve, and are welded into an integral structure.

[0048] In specific implementation, the medium-pressure main steam valve can use the original medium-pressure main steam valve 1 or set a new medium-pressure main steam valve, and the medium-pressure main steam valve steam inlet center line of the new medium-pressure main steam valve is consistent with the original medium-pressure main steam valve steam inlet center line 11.

[0049] like Figure 1 — Figure 5 As shown, in this embodiment, the medium-pressure main steam valve adopts the original medium-pressure main steam valve 1.

[0050] It avoids a series of problems caused by replacing the medium-pressure main steam valve, such as the selection, procurement, installation and adaptation of the new valve, and can make full use of existing equipment resources and reduce the investment cost and time cost of equipment renewal and transformation.

[0051] At the same time, it allows the installation of a new medium-pressure main steam valve, and the steam inlet center line of the new medium-pressure main steam valve is consistent with the steam inlet center line 11 of the original medium-pressure main steam valve. This design can ensure the consistency of the new valve with the original system in installation position and connection method when the medium-pressure main steam valve needs to be upgraded, replaced or optimized, ensuring seamless docking of new and old equipment, improving the system's compatibility with different medium-pressure main steam valves, and providing convenience for future equipment updates or technical improvements.

[0052] In this embodiment, the two medium-pressure regulating valves 2 with internal valve cores having a large and a small diameter are respectively a large medium-pressure regulating valve (large valve) with an internal valve core having a large diameter and a small medium-pressure regulating valve (small valve) with an internal valve core having a small diameter.

[0053] This technical measure simplifies the equipment structure, reduces the number of components, and lowers manufacturing costs and maintenance. Furthermore, because the two intermediate-pressure regulating valves 2 are symmetrically distributed along their steam outlet centerlines 22, and the valve housing 21 is welded integrally to the original intermediate-pressure main steam valve 1, the entire valve assembly is more evenly stressed, operating more stably and reliably, and providing smoother steam flow, reducing energy loss and the risk of equipment failure.

[0054] like Figure 1 、 Figure 6As shown, one end of the steam outlet of the medium-pressure regulating valve 2 of the valve housing 21 is connected to the special-shaped tee 4; the two special-shaped tee steam input interfaces 41 of the special-shaped tee 4 are respectively connected to the two steam outlets of the medium-pressure regulating valve 2, and the special-shaped tee steam input interface 41 is asymmetrically designed; the steam output interface of the special-shaped tee 4 is connected to the original medium-pressure steam pipe 8 through the elbow 5.

[0055] During implementation, the special-shaped tee 4, elbow 5, and original medium-pressure steam conduit 8 are welded together. The design of the special-shaped tee 4 effectively collects the steam from the outlets of the two medium-pressure regulating valves 2 and connects to the original medium-pressure steam conduit 8 through the elbow 5, achieving rational distribution and delivery of steam and ensuring the normal operation of the steam system. Its unique structure helps optimize the flow rate and pressure distribution of steam, improving the overall performance and efficiency of the system. The special-shaped tee steam input interface 41 is an asymmetric design that can better match the steam outlets of the two medium-pressure regulating valves 2 of different sizes, allowing steam to flow more evenly and smoothly after entering the special-shaped tee 4, reducing steam disturbance and energy loss, and improving the efficiency and quality of steam delivery.

[0056] Furthermore, the special-shaped tee 4 is a casting. The special-shaped tee 4 is a casting, which has high strength and good pressure resistance, can withstand the high temperature and high pressure environment of steam, and ensure the safety and reliability of the equipment during long-term operation.

[0057] A method for using the above-mentioned medium-pressure main steam regulating valve group includes: During heat supply regulation, as the heat supply and steam extraction increase, the internal valve core is gradually closed in conjunction with the large-diameter medium-pressure regulating valve to the minimum value to ensure stable steam extraction pressure. If the steam extraction volume continues to increase, gradually close the internal valve core and match the small medium-pressure regulating valve with a small diameter to the allowable opening value to ensure the stability of the steam extraction pressure.

[0058] By adopting this technical measure, the opening of the medium-pressure regulating valve 2 can be increased to reduce throttling losses while achieving the same steam extraction effect. This can not only improve the operating economy of the unit and reduce the vibration risk of the valve at a small opening, but also effectively reduce the use of gas boilers to supply external steam when multiple units are operating or a single unit is operating, thereby improving the economic benefits of the power plant. First, gradually close the large valve (large medium pressure regulating valve) to the minimum value to ensure stable extraction pressure. This regulation method can accurately control the large flow steam channel and avoid large fluctuations in extraction pressure caused by sudden and large closing or opening of the large valve. Because the flow regulation range of the large valve is relatively wide, in the initial stage, the main reliance on the large valve regulation can quickly adapt to changes in extraction volume. At the same time, by gradually closing it to the minimum value, the extraction pressure can change within a relatively stable range. When the extraction volume needs to increase further, the small valve (small-medium pressure regulating valve) is gradually closed to the allowable opening value to maintain stable extraction pressure. The small valve has a relatively small flow rate, and fine adjustment of its opening can fine-tune the extraction pressure. When the large valve has been closed to a certain degree, the regulation of the small valve can further precisely control the extraction pressure, ensuring that it always meets the heating system's requirements for extraction pressure stability. This phased adjustment sequence, first adjusting the large valve and then the small valve, effectively reduces fluctuations in extraction pressure and improves the operational stability of the entire heating system.

[0059] At the same time, adjusting the large valve first can quickly meet the initial demand for increased steam extraction. Subsequent adjustment of the small valve enables more precise flow control. The large and small valves each handle different ranges of regulation. The large valve primarily handles larger variations in steam extraction, while the small valve handles finer adjustments within a smaller range. This combined regulation method expands the regulation range of the entire regulation system while improving regulation accuracy. For example, when precise steam flow control is required to meet specific heating conditions, fine adjustment of the small valve can ensure that the steam flow closely matches demand, avoiding over- or under-regulation.

[0060] Gradually closing the large valve to its minimum setting, rather than initially assigning primary control to the small valve, can reduce the frequent adjustments and impacts on the small valve under high flow rates and large pressure differentials, thereby minimizing the risk of vibration. Overworking the small valve at high steam extraction rates can accelerate wear of components such as the valve core due to the impact of high-velocity steam. By adjusting the large valve first, the small valve primarily operates within a relatively small flow rate and pressure differential range, reducing wear and extending its service life. Furthermore, gradually closing the large valve prevents excessive mechanical stress on its internal components caused by sudden, large movements, helping to protect the structural integrity of the large valve and reduce equipment maintenance costs and frequency.

[0061] This regulation method enables the system to better adapt to changes in heating demand. Whether the extraction rate increases slowly or changes relatively quickly, the sequence of adjusting the large valve first and then the small valve ensures a timely and effective response. For example, under conditions where the heating system load gradually increases, such as when falling temperatures in winter lead to a gradual increase in heating demand, this regulation method can flexibly adjust the extraction rate to meet heating demand at different stages. Furthermore, when the heating system requires rapid adjustments to the extraction rate, the coordinated regulation of the large and small valves provides sufficient adjustment capacity, enhancing the system's adaptability and flexibility.

[0062] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for modifying a medium-pressure main steam regulating valve group for extracting steam from a combined cycle unit turbine, characterized in that: The following steps are involved: S1. During the renovation, the original steam inlet centerline and valve foundation pit of the medium-pressure main steam valve shall remain unchanged; S2. Split the original medium-pressure regulating valve into two parallel medium-pressure regulating valves, combine the steam inlets of the two medium-pressure regulating valves into one, and weld them together with the original medium-pressure main steam valve to form an integrated structure; S3. The two medium-pressure regulating valves are configured as one large and one small, with their steam outlet centerlines symmetrically distributed on both sides of the steam outlet centerline of the original medium-pressure regulating valve; S4. Move the medium-pressure main steam regulating valve group as a whole toward the steam inlet side of the original medium-pressure main steam valve to meet the rooting requirements of the valve support and hanger; S5. Connect the steam outlets of the two medium-pressure regulating valves in step S3 respectively through special-shaped tees, and connect the steam output interface of the special-shaped tee to the original medium-pressure steam pipe through an elbow.

2. The method for modifying a medium-pressure main steam regulating valve group for extracting steam from a combined cycle unit steam turbine according to claim 1, characterized in that: In step S4, it also includes: Part of the original medium-pressure reheat pipeline is cut to form installation and support space for the medium-pressure main steam regulating valve group.

3. The method for modifying a medium-pressure main steam regulating valve group for extracting steam from a combined cycle unit steam turbine according to claim 1, characterized in that: In step S4, it also includes: Part of the original medium-pressure steam pipe is cut to leave enough space for the installation of the elbow.

4. The method for modifying a medium-pressure main steam regulating valve group for extracting steam from a combined cycle unit steam turbine according to claim 1, characterized in that: In step S4, the valve support and hanger adopts a split structure corresponding to the two medium-pressure regulating valves, and the lateral size of the valve support and hanger is expanded.

5. The method for modifying a medium-pressure main steam regulating valve group for extracting steam from a combined cycle unit steam turbine according to claim 1, characterized in that: In step S5, when the elbow is connected to the original medium-pressure steam pipe, on-site adjustment is performed through the straight pipe alignment section with adjustable length to achieve precise alignment welding of the special-shaped tee and the original medium-pressure steam pipe.

6. A medium-pressure main steam regulating valve group for extracting steam from a steam turbine of a combined cycle unit, characterized in that: The method for modifying a medium-pressure main steam regulating valve group for extracting steam from a combined cycle unit steam turbine according to claim 1, 2, 3, 4 or 5 comprises: a medium-pressure main steam valve; The internal valve core is matched with two medium-pressure regulating valves with different diameters, one large and one small, which are arranged in parallel and share a valve housing; The valve housing includes a medium-pressure regulating valve steam inlet connected to the medium-pressure main steam valve and a medium-pressure regulating valve steam outlet respectively matched with two internal valve cores, and the medium-pressure regulating valve steam outlets are symmetrically distributed along the steam outlet center line of the medium-pressure regulating valve; One end of the steam inlet of the medium-pressure regulating valve of the valve housing is connected to one end of the steam outlet of the medium-pressure main steam valve and welded into an integral structure.

7. The medium-pressure main steam regulating valve group for extracting steam from a steam turbine of a combined cycle unit according to claim 6, characterized in that: One end of the steam outlet of the medium-pressure regulating valve of the valve housing is connected to a special-shaped tee; The two special-shaped three-way steam input interfaces of the special-shaped three-way are respectively connected to the steam outlets of the two medium-pressure regulating valves, and the special-shaped three-way steam input interfaces are asymmetrically designed; The steam output interface of the special-shaped tee is connected to the original medium-pressure steam pipe through an elbow.

8. The medium-pressure main steam regulating valve group for extracting steam from a steam turbine of a combined cycle unit according to claim 7, characterized in that: The special-shaped tee is a casting.

9. A method for using the medium-pressure main steam regulating valve group according to any one of claims 6 to 8, characterized in that: include: During heating adjustment; As the heat supply and steam extraction increase, gradually close the internal valve core and the large-diameter medium-pressure regulating valve to the minimum value to ensure stable steam extraction pressure. If the steam extraction volume continues to increase, gradually close the internal valve core and match the small medium-pressure regulating valve with a small diameter to the allowable opening value to ensure the stability of the steam extraction pressure.

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