Feed water temperature increasing system and thermal power generating unit
By introducing steam ejectors into thermal power units and using high-pressure steam to extract steam from turbines to increase the feed water temperature, the problem of insufficient flue gas temperature at the SCR device inlet under low load was solved, and safe and stable operation of the equipment was achieved.
Patent Information
- Application Number
- CN202422592083.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-25
- Publication Date
- 2025-09-05
- Estimated Expiration
- 2034-10-25
AI Technical Summary
Under low-load conditions, the flue gas temperature at the inlet of the SCR device of a thermal power unit cannot meet the minimum temperature requirement for denitrification, resulting in ammonia escape and equipment safety and stability problems.
A steam ejector is introduced into the thermal power unit, and high-pressure steam is extracted from the boiler to a section of the steam turbine. After mixing, the steam is reduced in pressure and injected into the high-pressure heater to increase the feed water temperature and ensure that the flue gas temperature at the inlet of the SCR device meets the denitrification requirements.
It effectively improves the inlet flue gas temperature of the SCR device, avoids ammonia escape and equipment resistance increase, ensures the safe and stable operation of the unit, and has low construction difficulty and low transformation cost.
Smart Images
Figure CN223306902U_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a feedwater heating system for a thermal power unit, and in particular to a feedwater temperature increasing system and a thermal power unit. Background Art
[0002] In my country, coal-fired power plants generally use selective catalytic reduction (SCR) for denitrification. This process involves a catalyst reacting NOx with NH3 to produce water vapor and nitrogen. To ensure effective denitrification, the flue gas temperature must be within a certain range. In practical projects, the SCR device is installed after the economizer and before the air preheater to meet the required flue gas temperature for denitrification.
[0003] When the unit load decreases, the flue gas flow rate also decreases, the flue gas temperature at the furnace outlet decreases, and the reheat steam temperature and boiler feed water temperature both decrease, resulting in a decrease in the flue gas temperature at the economizer outlet. The flue gas temperature at the SCR device inlet cannot meet the minimum temperature requirement for denitrification. This not only fails to meet the unit's deep peak regulation requirements, but also causes ammonia escape, causing the air preheater flue gas differential pressure and the air and smoke system resistance to increase rapidly, affecting the safe and stable operation of the equipment. Utility Model Content
[0004] The present disclosure aims to provide a feedwater temperature raising system and a thermal power unit to solve the technical problem that the inlet flue gas temperature of the SCR device cannot meet the minimum temperature requirement for denitrification under low-load conditions of the thermal power unit.
[0005] In order to achieve the above-mentioned objectives, the present disclosure provides a feed water temperature raising system, comprising: a boiler, a steam turbine, the boiler providing main steam to the steam turbine, a high-pressure heater, the water outlet side of the high-pressure heater being fluidically connected to the boiler, and a steam ejector, the high-pressure steam inlet of the steam ejector being fluidically connected to the boiler via a main pipe, the low-pressure steam inlet of the steam ejector being fluidically connected to the steam turbine via a low-pressure steam pipeline, and the steam outlet of the steam ejector being fluidly connected to the high-pressure heater via a mixed steam pipeline.
[0006] Optionally, the boiler further includes a low-temperature superheater and a partition screen superheater, the outlet header of the low-temperature superheater is connected to the steam inlet end of the main pipe via a first sampling tube, and the inlet header of the partition screen superheater is connected to the steam inlet end of the main pipe via a second sampling tube.
[0007] Optionally, a cooler is provided on the first sampling tube.
[0008] Optionally, the main pipe is provided with: a first electric valve for controlling the on-off of the main pipe, a first pneumatic regulating valve, arranged downstream of the first electric valve, for controlling the high-pressure steam flow in the main pipe, and a backup manual valve, arranged upstream of the first electric valve, for controlling the on-off of the main pipe.
[0009] Optionally, the main pipe and the high-pressure heater are fluidically connected in an on-off manner through a standby bypass, and a pressure reducing device is provided on the standby bypass, and the pressure reducing device is used to reduce the pressure of the high-pressure steam from the main pipe and send it into the high-pressure heater. The feed water temperature increasing system is configured as follows: when the standby bypass is connected, the low-pressure steam pipeline and the mixed steam pipeline are disconnected; when the low-pressure steam pipeline and the mixed steam pipeline are connected, the standby bypass is disconnected.
[0010] Optionally, a second electric valve is further provided on the backup bypass, and the second electric valve is provided upstream of the pressure reducing device and is used to control the on-off of the backup bypass.
[0011] Optionally, a third electric valve is provided on the low-pressure steam pipeline, and a fourth electric valve is provided on the mixed steam pipeline.
[0012] Optionally, the steam turbine and the high-pressure heater are fluidically connected in a disconnectable manner through a section of steam extraction pipeline, and the feed water temperature increasing system is configured as follows: when the main pipe is connected, the section of steam extraction pipeline is disconnected; when the section of steam extraction pipeline is connected, the main pipe is disconnected.
[0013] Optionally, a fifth electric valve is provided on the section of the steam extraction pipeline, and the fifth electric valve is used to control the on-off of the section of the steam extraction pipeline.
[0014] On the basis of the above technical solution, the present disclosure further provides a thermal power unit, comprising the feed water temperature increasing system in the above technical solution.
[0015] Through the above-mentioned technical solution, in the feedwater temperature raising system provided by the present disclosure, when the unit load is low or the unit has just been started, the boiler feedwater temperature is low, resulting in the SCR device inlet flue gas temperature not meeting the minimum denitrification temperature requirement. The steam ejector can use high-quality, high-pressure steam from the boiler to inject a section of extracted steam from the turbine to improve the steam inlet parameters and steam volume. The steam ejector can then inject the mixed steam into the high-pressure heater after reducing the pressure through the diffuser tube to raise the feedwater temperature of the high-pressure heater. In addition, by adding a steam ejector to the thermal power unit, only some pipe sockets need to be installed on the basis of the existing pipeline, which is easy to construct, with a short renovation period and low renovation cost. In addition, the operating state of the steam ejector can be adjusted in real time by controlling the opening and closing of the main pipe, low-pressure steam pipeline, and mixed steam pipeline in response to changes in the unit load. The thermal power unit provided by the present disclosure has the same technical effects as the feedwater temperature raising system of the above-mentioned technical solution. To avoid unnecessary repetition, it will not be described here.
[0016] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:
[0018] Figure 1 It is a connection diagram of the water supply temperature raising system in a specific embodiment of the present disclosure.
[0019] Description of Reference Numerals
[0020] 1- boiler, 11- low temperature superheater, 12- partition screen superheater,
[0021] 2- Steam turbine,
[0022] 3-steam ejector, 31-high pressure steam inlet, 32-low pressure steam inlet, 33-steam outlet,
[0023] 4- High voltage heater,
[0024] 50-main pipe, 501-first electric valve, 502-first pneumatic regulating valve, 503-spare manual valve, 51-first sampling pipe, 511-desuperheater, 52-second sampling pipe, 53-spare bypass, 531-second electric valve, 532-pressure reducing device, 54-low-pressure steam pipeline, 541-third electric valve, 55-mixed steam pipeline, 551-fourth electric valve, 56-first stage steam extraction pipeline, 561-fifth electric valve. DETAILED DESCRIPTION
[0025] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.
[0026] In this disclosure, unless otherwise indicated, directional terms such as "inside" and "outside" generally refer to the inside and outside relative to the outline of the corresponding component itself. "Upstream" and "downstream" refer to upstream and downstream along the direction of steam flow, that is, steam flows from upstream to downstream. Terms such as "first" and "second" are used in this disclosure to distinguish one element from another and do not convey order or importance. Furthermore, when the following description refers to the drawings, unless otherwise indicated, identical numbers in different drawings represent identical or similar elements.
[0027] According to the specific embodiment of the present disclosure, a water temperature raising system is provided, referring to Figure 1 As shown, the feed water temperature raising system may include a boiler 1, a steam turbine 2, a steam ejector 3 and a high pressure heater 4, wherein the boiler 1 provides main steam to the steam turbine 2. Figure 1 The main steam pipeline between the boiler 1 and the steam turbine 2 is not shown. The water outlet side of the high-pressure heater 4 is fluidically connected to the boiler 1 to supply water to the boiler 1. The high-pressure steam inlet 31 of the steam ejector 3 can be fluidically connected to the boiler 1 through the main pipe 50 to obtain high-pressure steam from the boiler 1. The low-pressure steam inlet 32 of the steam ejector 3 can be fluidically connected to the steam turbine 2 through the low-pressure steam pipeline 54 to obtain a section of extraction steam from the steam turbine 2. The steam outlet 33 of the steam ejector 3 can be fluidically connected to the high-pressure heater 4 through the mixed steam pipeline 55.
[0028] The working process of the steam ejector 3 is as follows: the high-pressure steam in the boiler 1 can form a negative pressure therein after entering the steam ejector 3, so as to draw a large amount of first-stage extraction steam from the steam turbine 2. The high-pressure steam and the first-stage extraction steam are mixed and reduced in pressure in the diffuser pipe and then injected into the high-pressure heater 4.
[0029] Through the above-described technical solution, in the feedwater temperature raising system provided by the present disclosure, when the unit load is low or the unit has just been started, the feedwater temperature of boiler 1 is low, resulting in the flue gas temperature at the inlet of the SCR device failing to meet the minimum denitrification temperature requirement, the steam ejector 3 can use high-quality, high-pressure steam from the boiler 1 to inject a section of extracted steam from the steam turbine 2 to improve the inlet steam parameters and amount. The steam ejector 3 can then inject the mixed steam into the high-pressure heater 4 after reducing the pressure through the diffuser tube to raise the feedwater temperature of the high-pressure heater. In addition, by adding the steam ejector 3 to the thermal power unit, only some pipe sockets need to be installed on the basis of the existing pipeline, which reduces the construction difficulty, shortens the renovation period, and reduces the renovation cost. In addition, the operating state of the steam ejector 3 can be adjusted in real time by controlling the opening and closing of the main pipe 50, the low-pressure steam pipeline 54, and the mixed steam pipeline 55 in response to changes in the unit load.
[0030] In the specific embodiments of the present disclosure, reference is made to Figure 1 As shown, the boiler 1 may further include a low-temperature superheater 11 and a partitioned superheater 12. The steam ejector 3 can obtain high-pressure steam from each of the low-temperature superheater 11 and the partitioned superheater 12 in the boiler 1. To sample each of the low-temperature superheater 11 and the partitioned superheater 12, a first sampling tube 51 connects the outlet header of the low-temperature superheater 11 to the steam inlet end of the main pipe 50, and a second sampling tube 52 connects the inlet header of the partitioned superheater 12 to the steam inlet end of the main pipe 50. Specifically, the first sampling tube 51, the second sampling tube 52, and the main pipe 50 can be connected via a reducing tee joint. The high-pressure steam flowing out of the low-temperature superheater 11 and the high-pressure steam flowing to the partitioned superheater 12 flow into the main pipe 50 through the first sampling tube 51 and the second sampling tube 52, respectively, where they mix to form the high-pressure steam supplied to the steam ejector 3.
[0031] Since the steam output from the low-temperature superheater 11 reaches a temperature of 400-420°C, while the shell-side operating temperature of the high-pressure heater 4 is approximately 383.6°C, a desuperheater 511 can be installed on the first sampling pipe 51, taking into account the ejection steam pressure level and temperature. This reduces the temperature of the high-pressure steam entering the main pipe 50 to approximately 380°C, matching the temperature of the first-stage extraction steam. Furthermore, by supplying desuperheated high-pressure steam to the steam ejector 3, the steam inlet volume on the low-pressure steam side can be increased, facilitating main steam extraction and reducing the risk of overheating caused by low-load steam extraction.
[0032] In order to control the on-off of the mother pipe 50, refer to Figure 1As shown, the main pipe 50 can be provided with a first electric valve 501, which is used to control the opening and closing of the main pipe 50. In addition, the main pipe 50 can also be provided with a first pneumatic control valve 502, which can be located downstream of the first electric valve 501. By controlling the opening of the first pneumatic control valve 502, the high-pressure steam flow in the main pipe 50 can be controlled, thereby facilitating more precise regulation of the operating state of the steam ejector 3. In addition, to prevent failure of the first electric valve 501, the main pipe 50 can also be provided with a backup manual valve 503, which can be located upstream of the first electric valve 501 and is used to control the opening and closing of the main pipe 50. When the first electric valve 501 is functioning normally, the backup manual valve 503 is normally open. If the first electric valve 501 fails, the staff can manually operate the backup manual valve 503 to control the opening and closing of the main pipe 50.
[0033] In addition, to avoid steam ejector 3 failure, refer to Figure 1 As shown, the main pipe 50 and the high-pressure heater 4 can also be fluidically connected in an on-off manner through a spare bypass 53. A pressure reducing device 532 can be provided on the spare bypass 53. The pressure reducing device 532 is used to reduce the pressure of the high-pressure steam from the main pipe 50 and send it into the high-pressure heater 4.
[0034] Accordingly, the feed water temperature increasing system can be configured as follows: when the standby bypass 53 is connected, the low-pressure steam pipeline 54 and the mixed steam pipeline 55 are disconnected; when the low-pressure steam pipeline 54 and the mixed steam pipeline 55 are connected, the standby bypass 53 is disconnected.
[0035] When the unit load is low or the unit has just been started, the feed water temperature of the boiler 1 is low, resulting in the flue gas temperature at the inlet of the SCR device failing to meet the minimum denitrification temperature requirement. If the steam ejector 3 fails, the low-pressure steam pipeline 54 and the mixed steam pipeline 55 are controlled to be disconnected, and the standby bypass 53 is controlled to be connected to bypass the steam ejector 3 outside the feed water temperature raising system, and the high-quality steam after pressure reduction is directly injected into the high-pressure heater 4 through the standby bypass 53 to heat the feed water. If the steam ejector 3 can work normally, the low-pressure steam pipeline 54 and the mixed steam pipeline 55 are controlled to be connected, and the standby bypass 53 is controlled to be disconnected to use the steam ejector 3 to raise the feed water temperature.
[0036] In order to control the on-off of the standby bypass 53, refer to Figure 1 As shown, a second electric valve 531 may be further provided on the standby bypass 53 . The second electric valve 531 may be provided upstream of the pressure reducing device 532 and used to control the on / off of the standby bypass 53 .
[0037] In order to control the on-off of the low-pressure steam pipeline 54 and the mixed steam pipeline 55, refer to Figure 1As shown, a third electric valve 541 may be provided on the low-pressure steam pipeline 54 , and a fourth electric valve 551 may be provided on the mixed steam pipeline 55 .
[0038] In addition, reference Figure 1 As shown, the steam turbine 2 and the high-pressure heater 4 can also be connected to each other in a switchable fluid connection via a steam extraction line 56. Accordingly, the feedwater temperature raising system can be configured such that when the main pipe 50 is open, the steam extraction line 56 is disconnected; and when the steam extraction line 56 is open, the main pipe 50 is disconnected.
[0039] When the unit is running at high load and the steam ejector 3 is not required to work, the main pipe 50 can be controlled to be disconnected and a section of the extraction steam pipeline 56 can be controlled to be connected to heat the feed water of the high-pressure heater 4 through a section of the extraction steam in the turbine 2.
[0040] When the unit load is low or the unit has just been started, the feed water temperature of the boiler 1 is low, resulting in the flue gas temperature at the inlet of the SCR device failing to meet the minimum denitrification temperature requirement, the main pipe 50 can be controlled to be open and a section of the steam extraction pipeline 56 can be controlled to be disconnected to increase the feed water temperature through the steam ejector 3.
[0041] In order to control the on-off of a section of the extraction steam pipeline 56, refer to Figure 1 As shown, a fifth electric valve 561 may be provided on the first section of the steam extraction pipeline 56 , and the fifth electric valve 561 is used to control the on-off of the first section of the steam extraction pipeline 56 .
[0042] On the basis of the above technical solution, the present disclosure further provides a thermal power unit, comprising the feed water temperature increasing system in the above technical solution.
[0043] Through the above technical solution, the thermal power unit provided by the present disclosure has the same technical effect as the feed water temperature increasing system in the above technical solution. In order to avoid unnecessary repetition, it will not be described here.
[0044] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.
[0045] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.
[0046] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.
Claims
1. A water temperature raising system, characterized in that: include: boiler, a steam turbine, the boiler providing main steam to the steam turbine, a high-pressure heater, the outlet side of the high-pressure heater being in fluid communication with the boiler, and A steam ejector, wherein the high-pressure steam inlet of the steam ejector is in fluid communication with the boiler via a main pipe, the low-pressure steam inlet of the steam ejector is in fluid communication with the steam turbine via a low-pressure steam pipeline, and the steam outlet of the steam ejector is in fluid communication with the high-pressure heater via a mixed steam pipeline.
2. The water supply temperature raising system according to claim 1, characterized in that: The boiler also includes a low-temperature superheater and a partition screen superheater. The outlet header of the low-temperature superheater is connected to the steam inlet end of the main pipe through a first sampling pipe, and the inlet header of the partition screen superheater is connected to the steam inlet end of the main pipe through a second sampling pipe.
3. The water temperature raising system according to claim 2, characterized in that: The first sampling tube is provided with a desuperheater.
4. The water supply temperature raising system according to claim 1, characterized in that: The mother tube is provided with: The first electric valve is used to control the on-off of the main pipe. a first pneumatic regulating valve, disposed downstream of the first electric valve, for controlling the flow of high-pressure steam in the mother pipe, and A spare manual valve is provided upstream of the first electric valve and is used to control the on-off of the main pipe.
5. The water supply temperature raising system according to claim 1, characterized in that: The main pipe is in fluid communication with the high-pressure heater via a standby bypass, and a pressure reducing device is provided on the standby bypass for reducing the pressure of the high-pressure steam from the main pipe and then sending it to the high-pressure heater. The feed water temperature raising system is configured such that: when the standby bypass is connected, the low-pressure steam pipeline and the mixed steam pipeline are disconnected; When the low-pressure steam pipeline and the mixed steam pipeline are connected, the standby bypass is disconnected.
6. The water supply temperature raising system according to claim 5, characterized in that: The standby bypass is further provided with a second electric valve, which is arranged upstream of the pressure reducing device and is used to control the on-off of the standby bypass.
7. The water supply temperature raising system according to claim 1, characterized in that: The low-pressure steam pipeline is provided with a third electric valve, and the mixed steam pipeline is provided with a fourth electric valve.
8. The water temperature raising system according to claim 1, characterized in that: The steam turbine and the high-pressure heater are in fluid communication with each other through a steam extraction pipeline. The feed water temperature raising system is configured as follows: when the main pipe is connected, the section of the steam extraction pipeline is disconnected; when the section of the steam extraction pipeline is connected, the main pipe is disconnected.
9. The water supply temperature raising system according to claim 8, characterized in that: A fifth electric valve is provided on the section of the steam extraction pipeline, and the fifth electric valve is used to control the on-off of the section of the steam extraction pipeline.
10. A thermal power unit, characterized in that: The water supply temperature raising system comprises the system according to any one of claims 1 to 9.