A top and bottom tangential throttling steam distribution structure and a reforming method thereof

Abstract

The present application belongs to the field of thermal power generation, and discloses a tangential throttling steam distribution structure and a reforming method thereof. The steam distribution structure is used to solve the problem of high investment cost of reforming a four-nozzle steam distribution unit into a valve-cylinder direct connection throttling steam distribution unit. The steam distribution structure comprises a high-pressure main steam valve, a high-pressure regulating valve, a high-pressure main steam pipe, a high-pressure outer cylinder, a high-pressure inner cylinder and a high-pressure steam inlet pipe. The high-pressure main steam regulating valve group is designed as a main-regulating structure. The steam inlet interface of the valve is matched with the original main steam pipe without reforming the valve support at the original valve position. The high-pressure main steam pipe arrangement and the cylinder structure are locally optimized. The steam inlet pressure loss is reduced by using the up-down tangential throttling steam distribution scheme, the high-pressure cylinder efficiency of the unit is improved, the economic efficiency of the unit reform is maximized, and the reform investment cost of the power plant is reduced.

Description

Technical Field

[0001] This invention belongs to the field of thermal power generation, and specifically relates to an upper and lower tangential throttling steam distribution structure and its modification method. Background Technology

[0002] Domestic chemical and petroleum enterprises have high-temperature and high-pressure units that have been in operation for many years. Most of these units use four-corner steam inlet nozzles for steam distribution. Two high-pressure main steam regulating groups are arranged on both sides of the operating platform and supported by rigid brackets. Each high-pressure main steam regulating valve group consists of one high-pressure main steam valve and two regulating valve groups. The main steam valve body and the regulating valve body are welded together, and the two high-pressure main steam regulating valve groups are independent of each other. The four regulating valves are connected to four symmetrically distributed steam inlets on the upper and lower parts of the high-pressure outer cylinder through four high-pressure main steam pipes. The main steam enters the independent nozzle chamber through the corresponding high-pressure main steam pipe. Nozzle steam distribution is generally divided into four groups, with each nozzle group corresponding to one regulating valve. The steam inlet is adjusted by controlling the nozzle group area. This method has good regulating performance and high efficiency in partial load cycles, but the low efficiency of the regulating stage limits the improvement of high-pressure cylinder efficiency. For self-owned power plants that operate at more than 75% load year-round and have long operating hours, the economics of nozzle steam distribution are worse than those of throttling steam distribution, and throttling steam distribution is more suitable.

[0003] Currently, the tangential throttling steam distribution technology with direct valve-cylinder connection is widely used in newly built units. However, for units using four-corner nozzle steam distribution to be converted to throttling steam distribution with direct valve-cylinder connection, it is often necessary to modify the foundation of the operating platform to meet the valve arrangement requirements. This will increase the investment cost of power plant conversion, and the economic recovery period of conversion is long, so it does not have universal applicability. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an up-and-down tangential throttling steam distribution structure and its modification method. Specifically, the nozzle steam distribution is modified to an up-and-down tangential throttling steam distribution structure by changing the one-main-two-regulator structure of the high-pressure main steam regulating valve group to a one-main-one-regulator structure. The valves are arranged in their original positions, the valve supports remain unchanged, the valve inlet interfaces are matched with the original main steam pipeline, and the layout of the high-pressure main steam pipeline and cylinder structure are locally optimized. By adopting an up-and-down tangential throttling steam distribution scheme, the inlet steam pressure loss is reduced, thereby improving the efficiency of the unit's high-pressure cylinder.

[0005] To achieve the objective of this invention, the technical solution adopted is as follows: A tangential throttling steam distribution structure includes two high-pressure main steam regulating valve groups, a high-pressure main steam pipe 3, a high-pressure outer cylinder 4, a high-pressure inner cylinder 5, and a high-pressure steam inlet pipe 6; wherein, the high-pressure main steam regulating valve groups include a high-pressure main steam valve 1 and a high-pressure regulating valve 2; wherein, the high-pressure main steam valve 1 is connected to the main steam inlet pipe before the valve, and the steam outlet after the valve of the high-pressure regulating valve 2 is connected to the high-pressure steam inlet pipe 6 installed on the cylinder through the high-pressure main steam pipe 3.

[0006] Furthermore, the high-pressure main steam valve 1 and the high-pressure regulating valve 2 in the high-pressure main steam regulating valve group are welded together.

[0007] Furthermore, the high-pressure steam inlet pipe 6 and the high-pressure outer cylinder 4 are combined together.

[0008] Furthermore, the high-pressure steam inlet pipe 6 is connected to the steam inlet of the high-pressure inner cylinder 5.

[0009] Furthermore, the two high-pressure regulating valves are the same size.

[0010] Furthermore, the two high-pressure main steam regulating valve groups are respectively arranged on the turbine operating platform on both sides of the turbine.

[0011] This invention provides a method for modifying an upper and lower tangential throttling steam distribution structure, used for modifying the original nozzle steam distribution. The specific modification method steps are as follows: (1) The two high-pressure main steam regulating valve groups (MSV-1 and CV-1, MSV-2 and CV-2) are arranged at their original installation positions on the operating platforms on both sides of the steam turbine. Under the premise that the valve inlet center line, valve support and foundation remain unchanged, the high-pressure regulating valve in each high-pressure main steam regulating valve group is reduced from two to one and combined with the high-pressure main steam valve to form a one-main-one-regulating structure. The steam outlet center line of the modified high-pressure regulating valves CV-1 and CV-2 is consistent with the outlet center line of the original valve group high-pressure regulating valves CV-3 and CV-4. (2) Looking from the turbine to the generator, the outlet of the left high pressure regulating valve passes through the left high pressure main steam pipe from the original middle layer position and connects with the high pressure steam inlet pipe on the lower left side of the high pressure cylinder to enter the high pressure steam inlet chamber. The outlet of the right regulating valve passes through the right high pressure main steam pipe from the original middle layer position and avoids the high pressure cylinder and the pit, and connects with the high pressure steam inlet pipe on the upper right side of the high pressure cylinder to enter the high pressure steam inlet chamber. The original main steam pipe and the inlet position of the high pressure main steam valve are aligned and welded together. (3) The high-pressure steam inlet pipe is combined with the high-pressure outer cylinder, and the high-pressure steam inlet pipe is connected to the high-pressure inner cylinder steam inlet. The high-pressure inner cylinder and the steam inlet chamber are optimized into a whole. The high-pressure inner cylinder steam inlet chamber is optimized from four steam inlets at the top and bottom to two tangential steam inlets at the top and bottom. The independent nozzle chamber and regulating stage are eliminated. (4) The high-pressure main steam pipe was changed from four pipes to two pipes to match the upper and lower tangential steam inlet method, and the pipe diameter was increased to ensure that the pipe flow velocity was within the design specifications to prevent the pipe from vibrating due to overspeed.

[0012] The above technical solution has the following beneficial effects: 1. The present invention provides an upper and lower tangential throttling steam distribution structure and its modification method, which can complete the modification of nozzle steam distribution to upper and lower tangential throttling steam distribution operation under the condition of limited modification boundary. The valve support and foundation are not modified. Only the high-pressure main steam regulating valve, high-pressure inner and outer cylinder structure and high-pressure main steam pipeline layout need to be optimized. After the modification, the weight of each component is equivalent to the weight of the original unit. It has no impact on the load distribution and structural strength of the original unit foundation, and can reduce the investment cost of power plant modification. There is basically no safety operation risk, and the maximum modification benefit is obtained.

[0013] 2. By modifying the upper and lower tangential throttling steam distribution, the pressure loss of high-pressure steam is reduced, which helps to improve high-pressure efficiency, thereby improving the unit's economy and reducing the unit's operating heat consumption rate. Attached Figure Description

[0014] Figure 1 This is a diagram showing the arrangement of the upper and lower tangential throttling steam distribution structure of the present invention; Figure 2 This is a comparison diagram of the structural changes of the high-pressure main steam regulating valve group before and after the modification of this invention; Figure 3 This is a schematic diagram of the arrangement of the high-pressure main steam regulating valve, pipeline and cylinder of the present invention; Figure 4 This is a schematic diagram of the high-pressure inner and outer cylinders, the steam inlet pipe assembly, and the steam inlet chamber of the present invention. Figure 5 This is a comparison diagram of the structural changes of the high-pressure main steam pipe before and after the modification of this invention.

[0015] In the diagram: 1-High-pressure main steam valve, 2-High-pressure regulating valve, 3-High-pressure main steam pipe, 4-High-pressure outer cylinder, 5-High-pressure inner cylinder, 6-High-pressure steam inlet pipe. Detailed Implementation

[0016] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0017] Example 1 A vertically tangentially throttling steam distribution structure includes two high-pressure main steam regulating valve groups, a high-pressure main steam pipe 3, a high-pressure outer cylinder 4, a high-pressure inner cylinder 5, and a high-pressure steam inlet pipe 6. The high-pressure main steam regulating valve groups include a high-pressure main steam valve 1 and a high-pressure regulating valve 2. The high-pressure main steam valve 1 is connected upstream to the main steam inlet pipe, and the steam outlet downstream of the high-pressure regulating valve 2 is connected via the high-pressure main steam pipe 3 to the high-pressure steam inlet pipe 6 mounted on the cylinder. The high-pressure main steam valve 1 and the high-pressure regulating valve 2 are welded together. The high-pressure steam inlet pipe 6 is connected to the high-pressure outer cylinder 4 and to the steam inlet of the high-pressure inner cylinder 5. The two high-pressure main steam regulating valve groups are respectively arranged on the turbine operating platforms on both sides of the turbine.

[0018] Example 2 Unit 2 of a power plant is a high-temperature, high-pressure, twin-cylinder, double-exhaust, impulse-type, single-shaft direct-drive air-cooled condensing steam turbine manufactured by a certain company. The unit model is C125-8.83 / 1.0. It was put into operation in 2009. After more than ten years of operation, the unit has developed problems such as high heat consumption, poor efficiency, and poor reliability, affecting its economic efficiency and safety.

[0019] Operating data of a power plant unit was collected. Unit 2 operated at full load for more than 8,000 hours throughout the year, with loads consistently above 105MW. In response to the unit's long-term high load and numerous operating hours, during the unit's flow path modification from 2022 to 2024, the modification of the upper and lower tangential throttling steam distribution was completed under the premise of limited modification boundaries.

[0020] The modification method is as follows: a vertically tangentially throttling steam distribution structure, including two high-pressure main steam valves, two high-pressure regulating valves, two high-pressure main steam pipes, one high-pressure outer cylinder, one high-pressure inner cylinder, and two high-pressure steam inlet pipes, such as... Figure 1 , 3 As shown. Compared to before the modification, the valve rigidity support remains unchanged, the single-sided high-pressure regulating valve has been changed from two to one, and the high-pressure regulating valves on both sides use the same size, such as... Figure 2 As shown; looking from the turbine towards the generator, the outlet of the left regulating valve connects to the high-pressure inlet pipe on the lower left side of the high-pressure outer cylinder via the left high-pressure main steam pipe, entering the high-pressure flow path. The outlet of the right regulating valve connects to the high-pressure inlet pipe on the upper right side of the high-pressure outer cylinder via the right high-pressure main steam pipe, entering the high-pressure flow path. Figure 3 As shown; the high-pressure inner and outer cylinder structures have been optimized. The independent nozzle chamber and regulating stage of the high-pressure inner cylinder have been eliminated. The high-pressure inner cylinder and the steam inlet chamber have been optimized into a single unit, changing from a top-to-bottom symmetrical four steam inlets to a top-to-bottom asymmetrical tangential two steam inlets. The high-pressure outer cylinder and the high-pressure inner cylinder are connected by a high-pressure pipe, as shown. Figure 4 As shown; after the modification, the high-pressure main steam pipe was reduced from four to two, and the pipe diameter was changed from φ273×25mm to φ325×25mm, matching the upper and lower tangential steam inlet method, as shown. Figure 5 As shown in the figure. After the modification, a throttling steam distribution operation mode is adopted, which uses the opening and closing of high-pressure regulating valves to increase or decrease the load, thereby improving the unit's load response speed and meeting the grid's requirements for primary frequency regulation and AGC assessment.

[0021] The unit is operating well after the modification, and the modification effect is better than the design value. The efficiency of the high-pressure cylinder has increased from 83.54% before the modification to 92.98% (design value 91.8%), which has greatly improved the unit efficiency, reduced the unit's operating heat consumption, and achieved significant energy saving and emission reduction effects.

[0022] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for modifying an upper and lower tangential throttling steam distribution structure, characterized in that: The modification method involves transforming the nozzle steam distribution into an upper and lower tangential throttling steam distribution structure, including the following steps: (1) The two high-pressure main steam regulating valve groups are arranged at the original installation positions of the operating platforms on both sides of the steam turbine. Under the premise that the valve inlet center line, valve support and foundation remain unchanged, the high-pressure regulating valve in each high-pressure main steam regulating valve group is reduced from two to one and combined with the high-pressure main steam valve to form a one-main-one-regulating structure. (2) Looking from the turbine to the generator, the outlet of the left high pressure regulating valve passes through the left high pressure main steam pipe from the original middle layer position and connects with the high pressure steam inlet pipe on the lower left side of the high pressure cylinder to enter the high pressure steam inlet chamber. The outlet of the right regulating valve passes through the right high pressure main steam pipe from the original middle layer position and avoids the high pressure cylinder and the pit, and connects with the high pressure steam inlet pipe on the upper right side of the high pressure cylinder to enter the high pressure steam inlet chamber. The original main steam pipe and the inlet position of the high pressure main steam valve are aligned and welded together. (3) The high-pressure steam inlet pipe is combined with the high-pressure outer cylinder, and the high-pressure steam inlet pipe is connected to the high-pressure inner cylinder steam inlet. The high-pressure inner cylinder and the steam inlet chamber are optimized into a whole. The high-pressure inner cylinder steam inlet chamber is optimized from four steam inlets at the top and bottom to two tangential steam inlets at the top and bottom. The independent nozzle chamber and regulating stage are eliminated. (4) The high-pressure main steam pipe was changed from four pipes to two pipes to match the upper and lower tangential steam inlet method, and the pipe diameter was increased to ensure that the pipe flow velocity was within the design specifications to prevent the pipe from vibrating due to overspeed. The upper and lower tangential throttling steam distribution structure includes two high-pressure main steam regulating valve groups, a high-pressure main steam pipe (3), a high-pressure outer cylinder (4), a high-pressure inner cylinder (5), and a high-pressure steam inlet pipe (6); the high-pressure main steam regulating valve group includes a high-pressure main steam valve (1) and a high-pressure regulating valve (2); the high-pressure main steam valve (1) is connected to the main steam inlet pipe before the valve, and the steam outlet after the valve of the high-pressure regulating valve (2) is connected to the high-pressure steam inlet pipe (6) installed on the cylinder through the high-pressure main steam pipe (3); The high-pressure main steam valve (1) and the high-pressure regulating valve (2) in the high-pressure main steam regulating valve group are welded together. The high-pressure steam inlet pipe (6) is joined together with the high-pressure outer cylinder (4); The high-pressure steam inlet pipe (6) is connected to the steam inlet of the high-pressure inner cylinder (5); The high-pressure regulating valves in the two high-pressure main steam regulating valve groups are of the same size. The two high-pressure main steam regulating valve groups are respectively arranged on the steam turbine operating platform on both sides of the steam turbine.

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