Low-pressure bypass valve group suitable for ultrahigh-parameter efficient unit steam turbine

Abstract

A high-temperature reheat steam system comprises a reheater, an intermediate-pressure cylinder, low-pressure cylinders, a generator and a condenser, an outlet of the reheater is connected with the intermediate-pressure cylinder through a pipeline, the intermediate-pressure cylinder is connected with the two low-pressure cylinders in parallel, and outlets of the low-pressure cylinders are connected with the condenser; the low-pressure bypass system comprises a first-stage low-pressure bypass valve, a second-stage low-pressure bypass valve and a low-pressure bypass pipeline, and the first-stage low-pressure bypass valve and the second-stage low-pressure bypass valve are arranged on the low-pressure bypass pipeline in series; the method avoids the diameter limitation of a nickel-iron-based alloy high-temperature material HT700 forge piece which is independently developed in China at present and can be used at the temperature of 650 DEG C or above, and solves the problem that machining and manufacturing of a conventional low-pressure bypass valve of an ultrahigh-parameter efficient unit steam turbine cannot be achieved in a short time. The first-stage low-pressure bypass valve can be manufactured according to the diameter of an existing nickel-iron-based alloy high-temperature material HT700 forged piece.

Description

Technical Field

[0001] The invention relates to the technical field of coal-fired power generation, and in particular to a low-pressure bypass valve group suitable for a steam turbine of an ultra-high parameter high-efficiency unit. Background Art

[0002] With the in-depth development of coal-fired power energy conservation and emission reduction, high-parameter power generation technology has been increasingly valued and has become a hot spot for research and development worldwide. In the past 20 years, the main steam parameters of my country's coal-fired power generation units have gradually developed from subcritical (16.7MPa, 535℃) to supercritical (24.2MPa, 566℃), then to ultra-supercritical (25MPa, 600℃), and then to high-parameter secondary reheating ultra-supercritical. The main steam temperature has reached a maximum of 615℃, and the reheat temperature has reached a maximum of 630℃. 630~650℃ will be an important development goal for the new round of steam parameter upgrades for thermal power units. 650℃ high-efficiency ultra-supercritical coal-fired power generation technology is a key technology for fundamentally reducing the overall energy consumption level of the unit, realizing the inter-generational upgrade of the unit and the efficient and clean coal-fired power generation. Compared with the current ultra-supercritical coal-fired power generation technology, the efficiency has been greatly improved and the CO2 emissions have been greatly reduced, which plays an important role in achieving my country's "3060" dual carbon goals.

[0003] The main steam and high-temperature reheat steam temperatures of conventional single-reheat units are 600°C and 620°C respectively, but the main steam and high-temperature reheat steam temperatures of ultra-high parameter high-efficiency coal-fired units will be increased to 650°C and above. At this time, conventional low-pressure bypass valves are no longer applicable. It is necessary to develop low-pressure bypass valves that can be manufactured with high-temperature materials suitable for 650°C and above, or to find a low-pressure bypass valve layout solution that can be satisfied by existing high-temperature materials.

[0004] The arrangement of the low-pressure bypass valve used in the prior art is a high-low pressure bypass system as disclosed in patent announcement number CN101737101A, in which the reheated steam flowing out of the boiler reheater is connected to the medium-pressure cylinder and the low-pressure bypass steam valve respectively, and only one low-pressure bypass steam valve is used to regulate the reheated steam. The low-pressure bypass valve used in this scheme can meet the main steam of 600°C and the high-temperature reheat steam of 620°C of the conventional single-reheat unit, but cannot meet the main steam and high-temperature reheat steam temperatures of 650°C and above of the ultra-high parameter high-efficiency coal-fired unit.

[0005] According to the bypass function requirements of 1000MW ultra-supercritical units, the conventional bypass system of the single reheat unit is a two-stage series bypass system, which is characterized by: the main steam is cooled and reduced in pressure by the high-pressure bypass and discharged to the low-temperature reheat steam pipeline, thereby bypassing the high-pressure cylinder; after that, the steam passes through the reheater to the high-temperature reheat hot section pipeline, and is cooled and reduced in pressure by the low-pressure bypass and discharged to the condenser, thereby bypassing the medium-pressure cylinder and the low-pressure cylinder.

[0006] In order to meet the requirements of low steam inlet pressure of the intermediate pressure cylinder and minimum flow rate of the boiler under various startup conditions, the volume flow rate of steam inlet of the low-pressure bypass valve is relatively large. At the same time, the pressure before the low-pressure bypass valve under rated conditions is relatively high, which is ~7MPa for ultra-high parameter single reheat units. The condenser is directly connected after the valve, and the pressure is usually required to be lower than 0.8. Therefore, the pressure reduction ratio of the low-pressure bypass valve is close to 10 times. Due to the low pressure after decompression and the large specific volume of steam, the valve shell diameter on the outlet side of the low-pressure bypass valve needs to reach more than 1100mm. The processing and manufacturing difficulty of nickel-iron-based alloy or nickel-based alloy forgings suitable for high-temperature materials of 650°C and above is higher than that of conventional ferrite alloy materials. At present, the diameter of nickel-iron-based alloy high-temperature material forgings independently developed by my country for 650°C and above can only be within 800mm. Therefore, if the low-pressure bypass valve is set according to the conventional low-pressure bypass valve, it will bring great difficulties to processing and manufacturing, and it is difficult to achieve in the short term. Therefore, the present invention designs a steam turbine low-pressure bypass system that is applicable to ultra-high parameter high-efficiency units of 650°C and above and can meet the current independently developed process manufacturing conditions in my country. Summary of the invention

[0007] The main purpose of the present invention is to provide a low-pressure bypass valve group suitable for a steam turbine of an ultra-high parameter high-efficiency unit, aiming to solve the existing technical problems.

[0008] To achieve the above object, the present invention provides a low-pressure bypass valve group suitable for a steam turbine of an ultra-high parameter high-efficiency unit, comprising a high-temperature reheat steam system and a low-pressure bypass system.

[0009] The high-temperature reheat steam system comprises a reheater, an intermediate pressure cylinder, a low pressure cylinder, a generator and a condenser, wherein the outlet of the reheater is connected to the intermediate pressure cylinder through a pipeline, the intermediate pressure cylinder is connected to two low pressure cylinders in parallel, and the outlet of the low pressure cylinder is connected to the condenser;

[0010] The low-pressure bypass system includes a primary low-pressure bypass valve, a secondary low-pressure bypass valve and a low-pressure bypass pipeline. Both ends of the low-pressure bypass pipeline are respectively connected to the high-temperature reheat steam pipeline at the outlet of the reheater and the condenser. The primary low-pressure bypass valve and the secondary low-pressure bypass valve are arranged in series on the low-pressure bypass pipeline.

[0011] Furthermore, the primary low-pressure bypass valve includes a primary low-pressure bypass valve A and a primary low-pressure bypass valve B.

[0012] Furthermore, the secondary low-pressure bypass valve includes a secondary low-pressure bypass valve A and a secondary low-pressure bypass valve B.

[0013] Furthermore, the low-pressure bypass pipeline includes a low-pressure bypass pipeline A and a low-pressure bypass pipeline B, the first-level low-pressure bypass valve A and the second-level low-pressure bypass valve A are arranged in series on the low-pressure bypass pipeline A, the first-level low-pressure bypass valve B and the second-level low-pressure bypass valve B are arranged in series on the low-pressure bypass pipeline B, and the low-pressure bypass pipeline A and the low-pressure bypass pipeline B are respectively connected to the condensers corresponding to the two low-pressure cylinders.

[0014] Furthermore, the first-stage low-pressure bypass valve is composed of a pressure reducing valve and a temperature reducing device. The pressure reducing valve adopts a constant pressure ratio first-stage pressure reduction and a straight-through valve body structure. The temperature reducing device is arranged on the valve body downstream of the pressure reducing valve core, reducing the pressure from 7MPa to 3.5MPa, and at the same time reducing the temperature after the valve to 500°C through temperature reducing water.

[0015] Furthermore, the secondary low-pressure bypass valve is composed of a pressure reducing valve and a temperature reducing device. The pressure reducing valve adopts multi-stage pressure reduction with adjustable pressure reduction ratio and an angle valve body structure. The temperature reducing device is arranged on the valve body downstream of the pressure reducing valve core, reducing the pressure from 3.5MPa to 0.8MPa, and at the same time reducing the temperature after the valve to 180°C through temperature reducing water.

[0016] Furthermore, a temperature measuring point is arranged at the outlet of the first-stage low-pressure bypass valve close to the inlet of the second-stage low-pressure bypass valve, and when the temperature exceeds a set value, the first-stage low-pressure bypass valve is closed in a chain manner.

[0017] Furthermore, the valve body of the first-stage low-pressure bypass valve is entirely made of nickel-iron-based alloy high-temperature material forgings.

[0018] Furthermore, the connecting pipeline after the first-stage low-pressure bypass valve is made of nickel-iron-based alloy high-temperature material pipeline.

[0019] The beneficial effects of the present invention are embodied in:

[0020] The present invention circumvents the diameter limitation of the HT700 forgings of nickel-iron-based alloy high temperature materials that can be used for temperatures above 650°C, which is currently independently developed in my country, and solves the dilemma of being unable to realize the processing and manufacturing of conventional low-pressure bypass valves for ultra-high parameter high-efficiency units in the short term. The first-level low-pressure bypass valve can be manufactured according to the diameter of the existing HT700 forgings of nickel-iron-based alloy high temperature materials;

[0021] The present invention reduces the pressure reduction ratio of a primary low-pressure bypass valve manufactured using nickel-iron-based alloy high-temperature materials, and reduces the difficulty of manufacturing the valve core. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of the low-pressure bypass valve group of the present invention.

[0023] Description of reference numerals:

[0024] 1. Reheater; 2. Primary low-pressure bypass valve; 2.1. Primary low-pressure bypass valve A; 2.2. Primary low-pressure bypass valve B; 3. Secondary low-pressure bypass valve; 3.1. Secondary low-pressure bypass valve A; 3.2. Secondary low-pressure bypass valve B; 4. Intermediate-pressure cylinder; 5. Low-pressure cylinder; 5.1 Low-pressure cylinder A; 5.2. Low-pressure cylinder B; 6. Generator; 7. Condenser; 7.1. Condenser A; 7.2. Condenser B; 8. Low-pressure bypass pipeline; 8.1. Low-pressure bypass pipeline A; 8.2. Low-pressure bypass pipeline B. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] The low-pressure bypass valve installed in ultra-high parameter high-efficiency units of 650℃ and above needs to handle large volume flow of steam and reduce the steam pressure to about 1 / 10 of the air inlet. If it is set according to the conventional low-pressure bypass valve, the valve shell diameter (1100mm) required on its outlet side exceeds the maximum diameter (800mm) that can be achieved by domestic nickel-iron-based alloy high-temperature material forgings that can be used for 650℃ and above.

[0027] See also Figure 1 The present invention provides a low-pressure bypass valve group suitable for a super-high parameter high-efficiency unit steam turbine, including a high-temperature reheat steam system and a low-pressure bypass system.

[0028] The high-temperature reheat steam system includes a reheater 1, an intermediate pressure cylinder 4, a low pressure cylinder 5, a generator 6 and a condenser 7. The outlet of the reheater 1 is connected to the intermediate pressure cylinder 4 through a pipeline. The intermediate pressure cylinder 4 is connected in parallel with two low pressure cylinders 5, namely low pressure cylinder A5.1 and low pressure cylinder B5.2. The outlet of the low pressure cylinder 5 is connected to the condenser 7.

[0029] The low-pressure bypass system includes a primary low-pressure bypass valve 2, a secondary low-pressure bypass valve 3 and a low-pressure bypass pipe 8. Both ends of the low-pressure bypass pipe 8 are respectively connected to the high-temperature reheat steam pipe at the outlet of the reheater 1 and the condenser 7. The primary low-pressure bypass valve 2 and the secondary low-pressure bypass valve 3 are arranged in series on the low-pressure bypass pipe 8.

[0030] The working process of the present invention is that the reheated steam at 650°C and above at the outlet of the reheater 1 enters the medium-pressure cylinder 4 to perform work under normal operating conditions and then enters two parallel low-pressure cylinders 5 in two ways, and the steam coming out of the low-pressure cylinder enters the condenser 7; during startup or shutdown conditions, the reheated steam at 650°C and above at the outlet of the reheater 1 enters the low-pressure bypass system, that is, passes through the low-pressure bypass pipe 8, and then passes through two stages of low-pressure bypass valve groups connected in series: a first-stage low-pressure bypass valve 2 and a second-stage low-pressure bypass valve 3, and the steam from the outlet of the second-stage low-pressure bypass valve 3 enters the condenser 7.

[0031] The present invention circumvents the diameter limitation of the HT700 forgings of nickel-iron-based alloy high-temperature materials that can be used above 650°C, which is currently independently developed in my country, and solves the dilemma that the processing and manufacturing of conventional low-pressure bypass valves for ultra-high-parameter high-efficiency unit steam turbines cannot be realized in the short term. A first-level low-pressure bypass valve can be manufactured according to the diameter of the existing HT700 forgings of nickel-iron-based alloy high-temperature materials.

[0032] The present invention reduces the pressure reduction ratio of a primary low-pressure bypass valve manufactured using nickel-iron-based alloy high-temperature materials, and reduces the difficulty of manufacturing the valve core.

[0033] Specifically, the low-pressure bypass pipeline includes a low-pressure bypass pipeline A8.1 and a low-pressure bypass pipeline B8.2. The first-level low-pressure bypass valve A2.1 and the second-level low-pressure bypass valve A3.1 are arranged in series on the low-pressure bypass pipeline A8.1. The first-level low-pressure bypass valve B2.2 and the second-level low-pressure bypass valve B3.2 are arranged in series on the low-pressure bypass pipeline B8.2. The low-pressure bypass pipeline A8.1 and the low-pressure bypass pipeline B8.2 are respectively connected to the condensers 7 corresponding to the two low-pressure cylinders 5.

[0034] Specifically, the first-stage low-pressure bypass valve 2 is composed of a pressure reducing valve and a temperature reducing device. The pressure reducing valve adopts a constant pressure ratio first-stage pressure reduction and a straight-through valve body structure. The temperature reducing device is arranged on the valve body downstream of the pressure reducing valve core, reducing the pressure from 7MPa to 3.5MPa, and at the same time reducing the temperature after the valve to 500°C through temperature reducing water.

[0035] Specifically, the secondary low-pressure bypass valve 3 is composed of a pressure reducing valve and a temperature reducing device. The pressure reducing valve adopts a multi-stage pressure reducing with an adjustable pressure reducing ratio and an angle valve body structure. The temperature reducing device is arranged on the valve body downstream of the pressure reducing valve core, reducing the pressure from 3.5MPa to 0.8MPa, and at the same time reducing the temperature after the valve to 180°C through the temperature reducing water.

[0036] Specifically, the primary low-pressure bypass valve 2 includes a primary low-pressure bypass valve A2.1 and a primary low-pressure bypass valve B2.2.

[0037] Specifically, the secondary low-pressure bypass valve 3 includes a secondary low-pressure bypass valve A3.1 and a secondary low-pressure bypass valve B3.2.

[0038] Specifically, a temperature measuring point is set at the outlet of the first-stage low-pressure bypass valve 2 close to the inlet of the second-stage low-pressure bypass valve 3, and when the temperature exceeds the set value, the first-stage low-pressure bypass valve 2 is closed in a chain manner.

[0039] Specifically, the valve body of the first-stage low-pressure bypass valve 2 is entirely made of nickel-iron-based alloy high-temperature material forgings.

[0040] Specifically, the connecting pipeline after the first-stage low-pressure bypass valve 2 adopts a nickel-iron-based alloy high-temperature material pipeline.

[0041] It should be noted that if the embodiments of the present invention involve directional indications such as up, down, left, right, front, back, etc., then the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture as shown in the accompanying drawings. If the specific posture changes, the directional indication will also change accordingly.

[0042] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or schemes that A and B meet at the same time. In addition, "multiple" refers to more than two. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-pressure bypass valve group suitable for ultra-high parameter high-efficiency unit steam turbine, characterized in that: Including high-temperature reheat steam system and low-pressure bypass system, The high-temperature reheat steam system comprises a reheater, an intermediate pressure cylinder, a low pressure cylinder, a generator and a condenser, wherein the outlet of the reheater is connected to the intermediate pressure cylinder through a pipeline, the intermediate pressure cylinder is connected to two low pressure cylinders in parallel, and the outlet of the low pressure cylinder is connected to the condenser; The low-pressure bypass system includes a primary low-pressure bypass valve, a secondary low-pressure bypass valve and a low-pressure bypass pipeline. Both ends of the low-pressure bypass pipeline are respectively connected to the high-temperature reheat steam pipeline at the outlet of the reheater and the condenser. The primary low-pressure bypass valve and the secondary low-pressure bypass valve are arranged in series on the low-pressure bypass pipeline.

2. A low-pressure bypass valve group for a steam turbine of an ultra-high parameter high-efficiency unit as claimed in claim 1, characterized in that: The primary low-pressure bypass valve includes a primary low-pressure bypass valve A and a primary low-pressure bypass valve B.

3. A low-pressure bypass valve group for a steam turbine of an ultra-high parameter high-efficiency unit as claimed in claim 2, characterized in that: The secondary low-pressure bypass valve includes a secondary low-pressure bypass valve A and a secondary low-pressure bypass valve B.

4. A low-pressure bypass valve group for a steam turbine of an ultra-high parameter high-efficiency unit as claimed in claim 3, characterized in that: The low-pressure bypass pipeline includes a low-pressure bypass pipeline A and a low-pressure bypass pipeline B. The first-level low-pressure bypass valve A and the second-level low-pressure bypass valve A are arranged in series on the low-pressure bypass pipeline A, and the first-level low-pressure bypass valve B and the second-level low-pressure bypass valve B are arranged in series on the low-pressure bypass pipeline B. The low-pressure bypass pipeline A and the low-pressure bypass pipeline B are respectively connected to the condensers corresponding to the two low-pressure cylinders.

5. A low-pressure bypass valve group for a steam turbine of an ultra-high parameter high-efficiency unit as claimed in claim 1, characterized in that: The first-stage low-pressure bypass valve is composed of a pressure reducing valve and a temperature reducing device. The pressure reducing valve adopts a constant pressure ratio first-stage pressure reduction and a straight-through valve body structure. The temperature reducing device is arranged on the valve body downstream of the pressure reducing valve core, reducing the pressure from 7MPa to 3.5MPa, and at the same time reducing the temperature after the valve to 500°C through temperature reducing water.

6. A low-pressure bypass valve group for a steam turbine of an ultra-high parameter high-efficiency unit as claimed in claim 1, characterized in that: The secondary low-pressure bypass valve is composed of a pressure reducing valve and a temperature reducing device. The pressure reducing valve adopts a multi-stage pressure reducing method with an adjustable pressure reducing ratio and an angle valve body structure. The temperature reducing device is arranged on the valve body downstream of the pressure reducing valve core, which reduces the pressure from 3.5MPa to 0.8MPa and reduces the temperature after the valve to 180°C through temperature reducing water.

7. A low-pressure bypass valve group for a steam turbine of an ultra-high parameter high-efficiency unit as claimed in claim 1, characterized in that: A temperature measuring point is arranged at the outlet of the first-stage low-pressure bypass valve close to the inlet of the second-stage low-pressure bypass valve, and the first-stage low-pressure bypass valve is interlocked and closed when the temperature exceeds the set value.

8. A low-pressure bypass valve group for a steam turbine of an ultra-high parameter high-efficiency unit as claimed in claim 1, characterized in that: The valve body of the first-stage low-pressure bypass valve is entirely made of nickel-iron-based alloy high-temperature material forgings.

9. A low-pressure bypass valve group for a steam turbine of an ultra-high parameter high-efficiency unit as claimed in claim 1, characterized in that: The pipeline connected after the primary low-pressure bypass valve is made of nickel-iron-based alloy high-temperature material pipeline.

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