A high-parameter drainage treatment system for boiler-turbine decoupling

Abstract

A high-parameter drain water treatment system for boiler-turbine decoupling is applied to the thermal system of boiler-turbine decoupling. High-quality steam generated during boiler-turbine decoupling is used for medium heat exchange and energy storage, and the high-parameter drain water generated is treated by the system. The system includes two-stage heat exchangers, and the first-stage heat exchanger and the second-stage heat exchanger are arranged in series. The inlet of the first-stage heat exchanger is connected to the high-parameter drain water generated by the thermal system, and the outlet outputs medium-parameter drain water, which is connected to the inlet of the second-stage heat exchanger through an inter-stage connecting pipeline. The medium-parameter drain water continues to flow into the second-stage heat exchanger, and the low-parameter drain water is output from the outlet of the second-stage heat exchanger. The outlet of the second-stage heat exchanger is connected to the thermal system through a return water pipeline. It realizes the online operation of the fine treatment system and the deaerator, ensures the controllability of the boiler water quality. In addition, through the above drain water treatment, the energy storage system no longer needs to store the heat of the drain water, greatly reducing the amount of energy storage medium used, reducing the energy storage investment, and the energy is recovered in a cascaded manner, with a significant energy-saving effect.

Description

Technical Field

[0001] The present invention belongs to the field of flexible peak shaving of thermal power plants, can meet the large-scale and long-term up and down peak shaving requirements of the power grid, can be used for all reheating units, is not restricted by heating / non-heating conditions, meets the requirements of the new power system, and specifically relates to a high-parameter drain water treatment system for boiler-turbine decoupling. Background Art

[0002] At present, deep thermal power decoupling can be achieved under the boiler-turbine decoupling condition, meeting flexible peak shaving and generating a large amount of high-quality steam for thermal energy storage. For details, reference can be made to the related patent CN219159037U. In the past, the steam ejector was used as an important device for hot reheat recirculation in the boiler-turbine decoupling system, which had two problems: 1) It needed to consume a large amount of high bypass steam as motive steam A and convert it into the flow of the cold reheat section. At the same time, the suction steam of the ejector was obtained by desuperheating the hot reheat steam, and the desuperheating water volume W was large. The sum of the motive steam and the desuperheating water volume became the hot reheat increment M = A + W. When the unit was not in heating mode, this part of the hot reheat steam increment M could only enter the intermediate pressure cylinder or go to the auxiliary steam. However, such treatment would lead to thrust imbalance and losses. 2) In addition, the high-temperature drain water generated after thermal energy storage was not suitable for connecting to the thermal system. The main drain water problems were as follows: When ternary salt was used to store high bypass extraction steam, high-temperature drain water would be generated. Its temperature range was between 200 and 350 °C. This part of the drain water had a high temperature and a large flow rate, especially difficult to dispose of under the condition of "shutting down the turbine but not the boiler". There were three conventional drain water treatment methods, but all had problems: One was to directly use a booster pump to pump it into the feed water header, and the drain water did not return to the deaerator, which would deteriorate the boiler water quality and affect safety. The second was to enter the drain water flash tank for flashing, reduce the temperature and pressure to reasonable parameters and then return to the deaerator. In this way, the heat loss was too large, and the drain water did not pass through the fine treatment device, so it was difficult to ensure the boiler water quality. The third was to return to the condenser after flashing, but the heat and working medium losses were also too large. Summary of the Invention

[0003] In order to effectively solve a series of problems of the current thermal power decoupling and the high-parameter drain water flowing back to the thermal system after decoupling and heat storage, the present invention proposes a high-parameter drain water treatment system for boiler-turbine decoupling.

[0004] A high-parameter drain water treatment system for boiler-turbine decoupling, which is applied to the thermal system of boiler-turbine decoupling. It is characterized in that the high-quality steam generated during boiler-turbine decoupling is used for medium heat exchange energy storage. The high-parameter drain water generated after medium heat exchange energy storage is processed by the high-parameter drain water treatment system. The high-parameter drain water treatment system includes two-stage heat exchangers, and the first-stage heat exchanger and the second-stage heat exchanger are arranged in series. The inlet of the first-stage heat exchanger is connected to the high-parameter drain water generated by the thermal system, and the outlet outputs medium-parameter drain water, which is connected to the inlet of the second-stage heat exchanger through an inter-stage connecting pipeline. The medium-parameter drain water continues to flow into the second-stage heat exchanger, and the low-parameter drain water is output from the outlet of the second-stage heat exchanger. The outlet of the second-stage heat exchanger is connected to the thermal system through a return water pipeline.

[0005] Furthermore, a boiler-turbine decoupling subsystem is used to achieve boiler-turbine decoupling. The boiler-turbine decoupling subsystem includes a high-pressure bypass, a hot reheat steam recirculation pipeline, and an out-of-furnace decoupling reheater. The exhaust steam from the high-pressure cylinder is heated by the out-of-furnace decoupling reheater. The heat source of the out-of-furnace decoupling reheater is the hot reheat steam from the hot reheat steam recirculation pipeline. After heating, the hot reheat steam becomes cold reheat steam, and the cold reheat steam is mechanically pressurized by a steam compressor and then returns to the boiler reheater to start the next cycle, achieving boiler-turbine decoupling. The high-pressure bypass generates high-bypass steam and inputs it into the energy storage module for energy storage.

[0006] Furthermore, a first pressure reducing valve is installed on the inter-stage connecting pipeline between the first-stage heat exchanger and the second-stage heat exchanger to maintain pressure isolation between the first-stage heat exchanger and the second-stage heat exchanger.

[0007] Furthermore, a second pressure reducing valve is also installed at the outlet of the second-stage heat exchanger to maintain the working pressure of the second-stage heat exchanger.

[0008] Furthermore, the thermal system includes a feed water system. The first-stage heat exchanger is connected in parallel with the high-pressure heater in the feed water system, and parallel bypasses are respectively led out from the feed water headers on the inlet and outlet sides of the high-pressure heater and connected to the first-stage heat exchanger.

[0009] Furthermore, the second-stage heat exchanger is connected in parallel with the low-pressure heater in the feed water system, and parallel bypasses are respectively led out from the feed water headers on the inlet and outlet sides of the low-pressure heater and connected to the second-stage heat exchanger.

[0010] Furthermore, a return water bypass is also led out from the inter-stage connecting pipeline. The return water bypass is connected to a drain water flash tank, and after flowing through the drain water flash tank, it is connected to the deaerator in the feed water system.

[0011] Furthermore, both the first-stage heat exchanger and the second-stage heat exchanger adopt tube bundle heat exchangers, where the high-pressure medium enters the tube side and the low-pressure medium enters the shell side.

[0012] Furthermore, the thermal system includes an energy storage module. The high-pressure steam in the thermal system enters the energy storage module, releases heat, and then outputs high-parameter drain water.

[0013] Furthermore, the hydrophobic flash tank is used as the flash tank.

[0014] The beneficial effects of the present invention are as follows:

[0015] The present invention proposes a brand-new solution, adding two-stage hydrophobic coolers. The first stage is a hydrophobic / water feed heat exchanger (3); the second stage is a hydrophobic / condensate heat exchanger (11). It realizes the online commissioning of the polishing system and the deaerator, ensuring the controllability of the boiler water quality. Through the above-mentioned method for hydrophobic treatment, the original molten salt energy storage system no longer needs to store the heat of the hydrophobic water, greatly reducing the amount of molten salt used and lowering the energy storage investment. The energy is recovered in a cascaded manner, with a significant energy-saving effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the system connection for Embodiment 1.

[0017] Figure 2 It is a schematic diagram of the system connection for Embodiment 2.

[0018] In the figure: high-temperature heat exchanger 1, low-temperature heat exchanger 2, first-stage heat exchanger 3, pressure reducing valve 4, deaerator 5, electric control regulating valve 6, electric control regulating valve 7, stop valve 8, steam compressor 9, out-of-furnace decoupling reheater 10, second-stage heat exchanger 11, electric control regulating valve 12, condenser 13, condensate pump 14, polishing equipment 15, electric control regulating valve 16, electric control regulating valve 17, hot re-steam recirculation pipeline 18, hot salt tank 19, cold salt tank 20, electric control regulating valve 21, hydrophobic flash tank 22, high-pressure bypass 23, high-pressure cylinder exhaust bypass 24, steam ejector 91. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] The technical solution of the present invention is not limited by the capacity of the power plant unit. It is not limited by the type of heat exchanger (such as tube bundle type, mixed type, etc.), steam compressor (which can also be a turbine compressor, axial flow compressor, centrifugal compressor, etc., can be electrically driven, or steam driven, such as equipment like steam ejectors, and can also be in different combined forms of series and parallel of multiple devices), etc., and can also be other devices with the same function.

[0021] The technical solution of the present invention is not restricted by the steam source of the steam energy storage method, nor by whether there is a boiler-turbine decoupling system and the drain water treatment system for high-pressure steam energy storage. It is also applicable to the drain water treatment method generated after heat exchange of high-pressure steam in other forms.

[0022] The technical solution of the present invention is not restricted by the participation of power plant units in deep heat and power decoupling and the number of heating units.

[0023] The technical solution of the present invention is not restricted by the steam parameters of power plant units.

[0024] The technical solution of the present invention is not restricted by the combined heat and power generation or pure condensation operation mode of power plant units.

[0025] The technical solution of the present invention is not restricted by the heat supply thermodynamic system of the power plant.

[0026] The technical solution of the present invention is not restricted by the energy storage working medium (molten salt, heat transfer oil, solid heat storage, phase change heat storage, etc.), the type and position of the energy storage reheater.

[0027] A high-parameter drain water treatment system for boiler-turbine decoupling, in which the boiler-turbine decoupling subsystem includes a high-pressure bypass 23, a hot re-steam recirculation pipeline 18, an out-of-boiler decoupling reheater 10, and a steam compressor 9. The hot re-steam recirculation pipeline 18 includes an inlet pipeline on the upstream side and an outlet pipeline on the downstream side of the out-of-boiler decoupling reheater 10. A steam compressor 9 is provided on the outlet pipeline, as well as related desuperheating water devices and necessary valves and control systems, etc. The exhaust steam from the high-pressure cylinder does not directly return to the original boiler reheater for heating, but is heated by the out-of-boiler decoupling reheater 10 through the high-pressure cylinder exhaust bypass 24. The heat source of the out-of-boiler decoupling reheater 10 is the hot re-steam from the hot re-steam recirculation pipeline 18. After the heating is completed, the hot re-steam becomes cold re-steam, which is pressurized by the steam compressor 9 and then returns to the boiler reheater to start the next cycle, realizing the complete decoupling of the boiler and the steam turbine. The boiler and the steam turbine change from the original strong correlation to a weak correlation, meeting the requirements of the deep peak shaving flexibility transformation. After the boiler-turbine decoupling, high-quality parameter steam can be generated, and high bypass steam GP is generated through the high-pressure bypass 23 and input into the molten salt system (the molten salt system shown in the dotted box is mainly composed of a hot salt tank 19, a cold salt tank 20, a high-temperature heat exchanger 1, a low-temperature heat exchanger 2, and the connected pipelines and pumps) for energy storage; after energy storage, high-parameter drain water will be generated and then enter the drain water system for treatment.

[0028] The drain water system includes two-stage heat exchangers, and the first-stage heat exchanger 3 and the second-stage heat exchanger 11 are arranged in series.

[0029] Both the first-stage heat exchanger 3 and the second-stage heat exchanger 11 adopt tube bundle heat exchangers, where the high-pressure medium enters the tube side and the low-pressure medium enters the shell side.

[0030] The tube side of the first - stage heat exchanger 3 is connected in series with the tube side of the second - stage heat exchanger 11. High - parameter drain water enters and flows through the tube side of the first - stage heat exchanger and then enters and flows through the tube side of the second - stage heat exchanger.

[0031] The inlet of the tube side of the first - stage heat exchanger is connected to the high - parameter drain water generated by the thermal system. The outlet of the tube side is connected to the inlet of the tube side of the second - stage heat exchanger through an inter - stage connecting pipeline. The high - parameter drain water continues to flow into the tube side of the second - stage heat exchanger and finally low - parameter drain water is output from the outlet of the tube side of the second - stage heat exchanger. The outlet of the tube side is connected to the thermal system through a return water pipeline.

[0032] The first - stage heat exchanger 3 is used for heat exchange of high - temperature media, and its shell side is connected to the high - temperature media.

[0033] The second - stage heat exchanger 11 is used for heat exchange of low - temperature media, and its shell side is connected to the low - temperature media.

[0034] The high - temperature medium and the low - temperature medium can be homologous media in the same thermal - system pipeline or heterologous media in different thermal - system pipelines.

[0035] An adjustable first pressure reducing valve 4 is installed on the inter - stage connecting pipeline between the first - stage heat exchanger and the second - stage heat exchanger, which is used to maintain pressure isolation between the first - stage heat exchanger and the second - stage heat exchanger.

[0036] Similarly, an adjustable second pressure reducing valve is also installed at the outlet of the tube side of the second - stage heat exchanger, which is used to maintain the working pressure of the second - stage heat exchanger.

[0037] A return water bypass is led out from the downstream side of the first pressure reducing valve on the inter - stage connecting pipeline. The return water bypass is connected to the drain water flash tank 22 and then connected to the thermal system after flowing through the drain water flash tank.

[0038] Example 1:

[0039] Taking a 300MW sub - critical unit as an example, the main steam flow of this model under THA is 928t and the output is 300MW. The system schematic diagram is as Figure 1 shown:

[0040] The thermal system includes a main steam pipeline, a high - pressure cylinder of the steam turbine, and a boiler reheater;

[0041] The main steam pipeline of the power plant is connected to the high - pressure bypass 23 pipeline and the main steam pipeline of the power plant is connected to the high - pressure cylinder of the steam turbine. The high - temperature and high - pressure main steam GB from the main steam pipeline, a part of the main steam GO enters the high - pressure cylinder of the steam turbine, and another part of the high - bypass steam GP enters the high - pressure bypass 23 pipeline.

[0042] The thermal system also includes an intermediate - pressure cylinder of the steam turbine and an intermediate - pressure cylinder steam inlet pipeline.

[0043] The system further includes a hot re-steam recirculation pipeline 18, a decoupled reheater 10 outside the furnace, and a high-pressure cylinder extraction bypass 24.

[0044] The decoupled reheater 10 outside the furnace is arranged on the hot re-steam recirculation pipeline 18 and is connected to the high-pressure cylinder extraction bypass 24 at the same time, and is used to heat the high-pressure cylinder extraction steam.

[0045] The high-pressure cylinder extraction bypass 24 is taken out from the high-pressure cylinder extraction pipeline of the original system. The high-pressure cylinder extraction bypass 24 is connected to the decoupled reheater 10 outside the furnace, and its outlet is connected to the intermediate-pressure cylinder inlet pipeline. The decoupled reheater 10 outside the furnace completes the heating of the high-pressure cylinder extraction steam and inputs it into the intermediate-pressure cylinder.

[0046] Part or all of the high-pressure cylinder extraction steam enters the shell side of the decoupled reheater 10 outside the furnace through the high-pressure cylinder extraction bypass 24, and after being heated, enters the intermediate-pressure cylinder inlet pipeline.

[0047] Through the above process, the high-pressure cylinder extraction steam that originally entered the boiler reheater is introduced. After the high-pressure cylinder extraction steam passes through the decoupled reheater 10 outside the furnace and completes the heating process, it enters the intermediate-pressure cylinder to do work and generate electricity.

[0048] The through-flow rate of the decoupled reheater 10 outside the furnace has a relatively large selection range, and it can be designed according to the full flow of the high-pressure cylinder extraction or partial flow to reduce the equipment cost.

[0049] The decoupled reheater 10 outside the furnace is connected in series on the hot re-steam recirculation pipeline 18. The hot re-steam recirculation pipeline 18 includes an inlet pipeline on the upstream side of the decoupled reheater 10 outside the furnace and an outlet pipeline on the downstream side. The pipeline taken out from the hot end outlet of the boiler reheater is connected to the tube side of the decoupled reheater 10 outside the furnace through the inlet pipeline, and the superheated steam in the hot re-steam recirculation pipeline 18 reheats the high-pressure cylinder extraction steam flowing through the shell side of the decoupled reheater 10 outside the furnace. The superheated steam in the hot re-steam recirculation pipeline 18 becomes cooler after passing through the decoupled reheater 10 outside the furnace and enters the cold end of the boiler reheater along the outlet pipeline.

[0050] A steam compressor 9 is arranged on the outlet pipeline and is driven by electricity. The steam compressor 9 adopts a turbine, axial flow or centrifugal compressor. By increasing the pressure value of the superheated steam at the outlet of the decoupled reheater 10 outside the furnace through the steam compressor 9, the steam parameters at the cold end of the boiler reheater can be matched. By using the mechanical pressurization method of driving the compressor by electricity, compared with another method of using a steam ejector to suck and pressurize the high-pressure cylinder extraction steam with the main steam, it will not introduce too much surplus steam in the hot re-circulation. The energy storage system only needs to connect to the high bypass steam for heat energy storage, which can reduce the construction scale and construction cost of the energy storage system.

[0051] The hot reheat steam recirculation pipeline 18, the out-of-furnace decoupled reheater 10 and the steam compressor 9 constitute the hot reheat steam recirculation module. The discharged steam of the steam compressor ensures that the inlet parameters of the boiler reheater meet the requirements of the boiler. Especially when the unit is in the pure condensing decoupled operating mode, the temperature of the ejector exhaust steam can be artificially controlled to increase, the exhaust steam flow can be reduced, the heat absorption of the boiler reheater can be reduced, the operating conditions of the tail flue can be optimized, and the operating conditions of the desulfurization and denitrification system and the air preheater at low boiler loads can be improved.

[0052] The exhaust steam from the high-pressure cylinder of the steam turbine can also be directly connected to the inlet of the cold section of the boiler reheater, and there is a valve control on the connecting pipeline. When the boiler and turbine are decoupled, it is gradually closed until fully closed.

[0053] The hot-end outlet of the boiler reheater can also be directly connected to the intermediate-pressure cylinder of the steam turbine through a pipeline to drive the intermediate-pressure cylinder of the steam turbine to do work, and there is a valve control on the pipeline to close or adjust the opening degree.

[0054] The exhaust steam from the intermediate-pressure cylinder further enters the low-pressure cylinder to work. The exhaust steam from the low-pressure cylinder is connected to the condenser 13 and generates condensate.

[0055] The thermal system also includes a feed water system. The condenser 13 generates condensate, which is driven by the condensate pump 14, passes through the fine treatment equipment 15 and the low-pressure heaters, and then is connected to the deaerator 5; the water outlet of the deaerator 5 returns to the boiler feed water inlet pipe after passing through the high-pressure heaters.

[0056] The exhaust steam from the intermediate-pressure cylinder also returns to the boiler feed water inlet pipe after passing through the deaerator 5 and the high-pressure heaters.

[0057] The thermal system further includes an energy storage module.

[0058] The heat source of the energy storage module is the high bypass steam GP in the high-pressure bypass 23. In addition, the energy storage module is composed of a hot salt tank 19, a cold salt tank 20, a high-temperature heat exchanger 1, a low-temperature heat exchanger 2, and the connected pipelines, pumps, etc. The heat exchanger adopts a shell-and-tube heat exchanger. The two ends of the shell side are respectively connected to the hot salt tank 19 and the cold salt tank 20, and the molten salt flows in the shell side and exchanges heat with the heat medium passing through the tube side of the high-temperature heat exchanger and the low-temperature heat exchanger. The heat exchange is surface heating, and the molten salt exchanges heat with the incoming steam or feed water, using steam to heat the low-temperature molten salt or using high-temperature molten salt to heat the feed water; the molten salt energy storage module is not limited to the above composition method, and the heat exchanger can also be of other forms.

[0059] Two groups of tube sides can be respectively arranged in the heat exchanger. The first group of tube sides is used for the steam to flow through; the high-pressure steam bypass is connected to the first group of tube sides. When the energy storage absorbs heat, the high bypass steam GP in the high-pressure steam bypass enters the first group of tube sides after being desuperheated and depressurized, and then cools and condenses to release heat for heating the molten salt medium in the shell side. The high-parameter drain water generated by the cooling and condensation enters the drain water treatment system.

[0060] The second set of tube passes (not shown in the figure) is used for flowing water medium and is connected to the feed water bypass. When releasing energy and heat, boiler feed water flows through the second set of tube passes and releases heat through the high-temperature molten salt medium in the shell pass, which can heat up the boiler feed water.

[0061] A hydrophobic treatment system, which includes two-stage heat exchangers. The first-stage heat exchanger 3 and the second-stage heat exchanger 11 are arranged in series.

[0062] Two-stage heat exchangers are provided. The first-stage heat exchanger 3 is a hydrophobic / water heat exchanger, which cools the 350 °C high-temperature hydrophobic water from the thermal system to the medium-temperature hydrophobic water range of 180 - 200 °C; the feed water in the hydrophobic / water heat exchanger cools the high-temperature hydrophobic water, rather than relying on the molten salt in the energy storage system to cool the high-temperature hydrophobic water, which can ensure the deaeration effect of the medium-temperature hydrophobic water output at 180 - 200 °C, while reducing the construction scale and construction cost of the energy storage system and saving the amount of salt used.

[0063] The second-stage heat exchanger 11 is a hydrophobic / condensate heat exchanger, which cools the hydrophobic water to the range of 60 - 120 °C. The condensate water in the hydrophobic / condensate heat exchanger cools the medium-temperature hydrophobic water, so that the hydrophobic water finally returns to the condenser at the low-temperature hydrophobic water range of 60 - 120 °C, preferably less than or equal to 80 °C. This can effectively ensure the operation of the fine treatment equipment in the feed water system. The suitable working temperature range of the medium in the fine treatment equipment is 60 - 120 °C, and a suitable return water temperature is required. At the same time, the low-temperature hydrophobic water reflux can further reduce the cold-end loss of the system.

[0064] Both the first-stage heat exchanger 3 and the second-stage heat exchanger 11 adopt tube bundle heat exchangers, where the high-pressure medium enters the tube pass and the low-pressure medium enters the shell pass.

[0065] The tube passes of the first-stage heat exchanger 3 and the second-stage heat exchanger 11 are connected in series. The high-parameter hydrophobic water enters the tube pass of the first-stage heat exchanger 3 and then enters the tube pass of the second-stage heat exchanger 11.

[0066] The inlet of the tube pass of the first-stage heat exchanger 3 is connected to the high-parameter 350 °C hydrophobic water generated by the thermal system. The outlet of the tube pass is connected to the inlet of the tube pass of the second-stage heat exchanger 11 through an inter-stage connecting pipeline. The high-parameter hydrophobic water continues to flow into the tube pass of the second-stage heat exchanger 11 and finally outputs low-parameter hydrophobic water at 60 - 120 °C from the outlet of the tube pass of the second-stage heat exchanger 11. The outlet of the tube pass is connected to the condenser 13 in the thermal system through a return water pipeline.

[0067] The first-stage heat exchanger 3 is used for heat exchange of high-temperature media, and its shell pass is connected to the high-temperature medium.

[0068] The first-stage heat exchanger 3 is connected in parallel with the high-pressure heater in the feed water system. Parallel bypasses are respectively led out from the front and rear sides (inlet and outlet sides) of the high-pressure heater to the feed water main pipes and connected to the shell side of the first-stage heat exchanger 3. Electric control regulating valves 6 and 7 are provided on the feed water pipeline and the parallel bypass, enabling the switching of the flow through the high-pressure heater and the first-stage heat exchanger 3.

[0069] An adjustable first pressure reducing valve 4 is installed on the inter-stage connecting pipeline between the first-stage heat exchanger 3 and the second-stage heat exchanger 11, which is used to maintain the pressure isolation between the first-stage heat exchanger 3 and the second-stage heat exchanger 11.

[0070] By setting an adjustable pressure reducing valve 4 in the downstream pipeline of the first-stage heat exchanger 3 (the drain / feed water heat exchanger), the pressure on the upstream steam side (drain side) is maintained, and the upstream and downstream pressure differences are isolated, enabling the heat exchanger of the energy storage module to maintain a high-pressure heat exchange state during the energy storage process.

[0071] The second-stage heat exchanger 11 is used for heat exchange of low-temperature media, and its shell side is connected to the low-temperature media.

[0072] The second-stage heat exchanger 11 is connected in parallel with the low-pressure heater in the feed water system. Parallel bypasses are respectively led out from the front and rear sides (inlet and outlet sides) of the low-pressure heater to the feed water main pipes and connected to the shell side of the second-stage heat exchanger 11. Electric control regulating valves 16 and 17 are provided on the feed water pipeline and the parallel bypass, enabling the switching of the flow through the low-pressure heater and the second-stage heat exchanger 11.

[0073] The high-temperature medium of the first-stage heat exchanger 3 and the low-temperature medium of the second-stage heat exchanger 11 are led out from the feed water main pipe. By setting electric control valves for shut-off and flow control, on the one hand, the heat exchange working condition can be adjusted (adjusting the temperature range of the drain); on the other hand, when the energy storage system is not operating, the thermal system can be switched to the original state to maintain the efficient operation of the unit.

[0074] Among them, the high-temperature medium and the low-temperature medium can be homologous media in the same thermal system pipeline, such as the boiler feed water in the same feed water system, or heterologous media in different thermal system pipelines.

[0075] Similarly, an adjustable second pressure reducing valve 4 is also installed at the tube side outlet of the second-stage heat exchanger 11 to maintain the working pressure of the second-stage heat exchanger 11. A second pressure reducing valve 4 is provided downstream of the second-stage heat exchanger 11, and a large-flow spraying device is installed at the throat of the condenser. The drain also maintains an appropriate pressure after passing through the second pressure reducing valve 4, enabling the drain to enter the spraying device under pressure. An exhaust valve to the atmosphere is also installed at the upper part of the condenser, and at this time, the condenser does not need to be evacuated.

[0076] The second-stage heat exchanger (drain / condensate heat exchanger) adopts the same pressure isolation design, so that the drain will not vaporize during the drain / condensate heat exchange process (vaporization will affect the heat exchange effect).

[0077] The specifically set drain pressure reducing valve 4 in the system is a key device, which can adjust the upstream heat exchange parameters, affect the downstream operating parameters, and maintain the good working conditions of the two-stage heat exchangers.

[0078] A return water bypass is led out on the downstream side of the first pressure reducing valve 4 in the inter-stage connecting pipeline. The return water bypass is connected to the drain flash tank 22 and then connected to the deaerator 5 in the thermal system after flowing through the drain flash tank 22.

[0079] Downstream of the first-stage heat exchanger 3, the drain can be divided into two paths. One path goes to the second-stage heat exchanger 11 through the inter-stage connecting pipeline, and the other path goes to the drain flash tank 22 through the return water bypass and then returns to the deaerator 5. The return water bypass is used to connect the medium-parameter drain at 180 - 200 °C to maximize the recovery of high-quality heat within the allowable range of boiler water quality and improve the unit

[0080] efficiency. And when the system operates in the "shutdown without boiler shutdown" mode, at this time, the exhaust steam flow of the steam turbine is zero, the drain no longer goes to the drain flash tank 22, and all enters the second-stage heat exchanger 11 and finally returns to the condenser 13 to ensure the water volume for fine treatment and ensure the safety of boiler water quality.

[0081] When the decoupling degree between the boiler and the turbine is not too large, the high bypass steam GP flow in the high-pressure bypass 23 is small, and the main steam inlet GO of the steam turbine is large. At this time, the output power generation still has value, and the efficiency still makes sense. To reduce the cold-end loss, without affecting the boiler water quality, the drain flash tank 22 (flash tank) can be put into operation. At this time, the exhaust steam volume of the steam turbine is large, and this part of the water volume can maintain the stability of the boiler water quality after being treated.

[0082] Through calculation and analysis, after the decoupling of the 300MW boiler and turbine, the boiler combustion is at 30% load rate and the steam turbine is shut down. At this time, the main steam is about 350t and all the energy is stored. The cold-end loss of the unit is only 350t of water, and the water temperature drops from 60 - 70 °C to 50 - 60 °C. The cold-end loss is: 350 * 4.1868 * 10 °C = 14.7 GJ / h, which is equivalent to 4.1 MW. The total heat of the boiler at this time is: 750 GJ / h, 235 MW. The cold-end loss is: 1.75%.

[0083] Embodiment 2:

[0084] Taking a 300MW subcritical unit as an example, the main steam flow of this model at THA is 928t and the output is 300MW. The system schematic diagram is as Figure 2As shown in the figure: The system further includes a hot re-steam recirculation pipeline 18 and a steam injector system.

[0085] The high-pressure bypass 23 pipeline is connected to the motive steam inlet of the steam injector system. A desuperheater and pressure reducer is provided on the high-pressure bypass 23 pipeline, and the diverted high bypass steam GP is used as the motive steam of the steam injector after being desuperheated and depressurized;

[0086] A pipeline is led out from the hot end outlet of the boiler reheater and is connected to the suction steam port of the steam injector 91 through the hot re-steam recirculation pipeline 18.

[0087] The steam from the hot re-steam recirculation pipeline 18 serves as the suction steam of the steam injector.

[0088] The exhaust steam port of the steam injector is connected to the cold end inlet of the boiler reheater through an exhaust steam pipeline.

[0089] An out-of-furnace decoupling reheater 10 is connected in series on the hot re-steam recirculation pipeline 18. The hot re-steam recirculation pipeline 18 includes an inlet pipeline on the upstream side and an outlet pipeline on the downstream side of the out-of-furnace decoupling reheater 10. The tube side of the out-of-furnace decoupling reheater 10 is accessed through the inlet pipeline, and then the suction steam port of the steam injector 91 is accessed through the outlet pipeline. The superheated steam in the hot re-steam recirculation pipeline is used to reheat the exhaust steam from the high-pressure cylinder flowing through the shell side of the out-of-furnace decoupling reheater 10. The superheated steam in the hot re-steam recirculation pipeline becomes cooler after passing through the out-of-furnace decoupling reheater and enters the suction steam port of the injector 91 along the outlet pipeline.

[0090] The hot re-steam recirculation pipeline and the steam injector form a hot re-steam recirculation module. The exhaust steam of the steam injector ensures that the inlet parameters of the reheater meet the boiler requirements. Especially when the unit is in a pure condensing decoupling condition, the temperature of the exhaust steam of the injector can be artificially controlled to increase, the exhaust steam flow can be reduced, the heat absorption of the boiler reheater can be reduced, the tail flue condition can be optimized, and the operation conditions of the desulfurization and denitration systems and the air preheater at low boiler loads can be improved.

[0091] The steam injector system can use a single steam injector or multiple steam injectors. Multiple steam injectors form a steam injector group through combination methods such as series connection, parallel connection, or series-parallel connection to realize the adjustment and optimization of parameters such as the injection ratio, complete variable working conditions, and the nozzles of the steam injectors can use fixed nozzles or adjustable nozzles.

[0092] In more implementation applications, the high-parameter hydrophobic treatment system in this application does not distinguish the size and type of the thermal system unit, does not distinguish whether the thermal system is provided with a decoupling module, whether it is provided with an energy storage system, and whether it uses a molten salt system. As long as the high-parameter hydrophobic water generated in the thermal system can be reasonably applied.

[0093] Finally, it should be noted that the above description is only an explanation of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail, those skilled in the art can still modify the technical solutions described above or make equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-parameter drainage treatment system for decoupling of turbine and boiler, which is applied to the thermal system for decoupling of turbine and boiler, is characterized in that The high-quality steam generated during the decoupling of the boiler and turbine is used for medium heat exchange energy storage. The high-parameter drain water generated after the medium heat exchange energy storage is processed by the high-parameter drain water treatment system. The high-parameter drain water treatment system includes two-stage heat exchangers, and the first-stage heat exchanger and the second-stage heat exchanger are arranged in series. The inlet of the first-stage heat exchanger is connected to the high-parameter drain water generated by the thermal system, and the outlet outputs medium-parameter drain water, which is connected to the inlet of the second-stage heat exchanger through an inter-stage connecting pipeline. The medium-parameter drain water continues to flow into the second-stage heat exchanger, and the low-parameter drain water is output from the outlet of the second-stage heat exchanger. The outlet of the second-stage heat exchanger is connected to the thermal system through a return water pipeline. The thermal system includes a feed water system. The first-stage heat exchanger is connected in parallel with the high-pressure heater in the feed water system, and parallel bypasses are respectively led out from the feed water headers on the inlet and outlet sides of the high-pressure heater and connected to the first-stage heat exchanger.

2. The high-parameter drain water treatment system for boiler-turbine decoupling according to claim 1, characterized in that, The decoupling of the boiler and turbine is realized by using the boiler-turbine decoupling subsystem. The boiler-turbine decoupling subsystem includes a high-pressure bypass, a hot reheat steam recirculation pipeline, and an out-of-furnace decoupling reheater. The exhaust steam from the high-pressure cylinder is heated by the out-of-furnace decoupling reheater. The heat source of the out-of-furnace decoupling reheater is the hot reheat steam from the hot reheat steam recirculation pipeline. After heating, the hot reheat steam becomes cold reheat steam. The cold reheat steam is mechanically pressurized by a steam compressor and then returns to the boiler reheater to start the next cycle, realizing the decoupling of the boiler and turbine. The high-pressure bypass generates high-bypass steam and inputs it into the energy storage module for energy storage.

3. The high-parameter drain water treatment system for boiler-turbine decoupling according to claim 1, wherein A first pressure reducing valve is installed on the inter-stage connecting pipeline between the first-stage heat exchanger and the second-stage heat exchanger to maintain pressure isolation between the first-stage heat exchanger and the second-stage heat exchanger.

4. The high-parameter drain water treatment system for boiler-turbine decoupling according to claim 3, wherein A second pressure reducing valve is also installed at the outlet of the second-stage heat exchanger to maintain the working pressure of the second-stage heat exchanger.

5. The high-parameter drain water treatment system for boiler-turbine decoupling according to claim 1, wherein, The second-stage heat exchanger is connected in parallel with the low-pressure heater in the feed water system, and parallel bypasses are respectively led out from the feed water headers on the inlet and outlet sides of the low-pressure heater and connected to the second-stage heat exchanger.

6. The high-parameter drain water treatment system for boiler-turbine decoupling according to claim 3, characterized in that, A return water bypass is also led out from the inter-stage connecting pipeline. The return water bypass is connected to a flash tank, and after flowing through the flash tank, it is connected to the deaerator in the feed water system.

7. The high-parameter drainage treatment system for boiler-turbine decoupling according to claim 1, wherein Both the first-stage heat exchanger and the second-stage heat exchanger adopt tube bundle heat exchangers, where the high-pressure medium enters the tube side and the low-pressure medium enters the shell side.

8. The high-parameter drainage treatment system for boiler-turbine decoupling according to claim 1, wherein The thermal system includes an energy storage module. The high-pressure steam in the thermal system enters the energy storage module, releases heat, and then outputs high-parameter drain water.

9. The high-parameter drainage treatment system for decoupling of boiler and turbine according to claim 6, characterized in that The flash tank is used as the flash tank.

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