Industrial steam supply system and method capable of improving the flexibility of coal-fired units

Abstract

The present application discloses an industrial steam supply system and method capable of improving the flexibility of a coal-fired unit, comprising a main steam pipeline, part of the main steam on the main steam pipeline flows into a high bypass pipeline, a small back pressure machine and a generator are arranged on the high bypass pipeline, the small back pressure machine drives the generator to generate electricity through the main steam and transmits it to the power consumption system, and the exhaust steam of the small back pressure machine enters the boiler reheater; the steam discharged from the boiler reheater is divided into a low-pressure bypass pipeline and a medium-pressure cylinder steam inlet pipeline, the low-pressure bypass pipeline comprises a first pipeline and a reheat extraction pipeline, the reheat extraction pipeline is divided into a second pipeline and a third pipeline, the steam in the first pipeline is transported to a condenser, the steam in the second pipeline is transported to a heat exchanger for heat exchange with desalted water and then enters the condenser, and the steam in the third pipeline is transported to a heating steam manifold for external heating; the present application can greatly improve the flexibility of the coal-fired unit, enhance the low-load industrial steam supply capacity of the steam turbine, and achieve the purpose of thermal and electrical decoupling.

Description

Technical Field

[0001] The present application belongs to the field of energy-saving technology for thermal power generation, and in particular, relates to an industrial steam supply system and method capable of improving the flexibility of coal-fired units. Background Art

[0002] National policies encourage existing coal-fired generating units to replace heating, actively shut down small boilers for heating and industrial steam supply, and carry out heating transformation for pure condensing units that meet heating conditions. At the same time, in order to promote the consumption of clean energy, the existing coal-fired units should be modified as much as possible to improve their deep peak-shaving capabilities. The policy requires their minimum power generation output to reach 35% of the rated load. However, many power generation companies require their subordinate power generation enterprises to have a minimum power generation output of less than 30% of the rated load.

[0003] Power generation companies in southern my country do not need to supply heating heat loads in winter, but most of them provide industrial steam to surrounding companies. Because their heat supply does not meet the heating requirements of cogeneration units, they are all dispatched according to pure condensing units, and they must participate in the deep peak regulation of thermal power units. For different industrial steam users, due to their different processes, the required steam pressure parameters are also different. For large thermal power units, the most common industrial heat user steam pressure is 1-1.5MPa and the temperature is 300-350℃. Power plants generally use reheating stage steam extraction for heating. When the demand of heat users is large, steam is extracted from the hot side, and when the demand is small, steam is extracted from the cold side.

[0004] Limited by the requirements of deep peak-shaving operation of the unit, the hot re-extraction of the steam turbine during low-load operation is sometimes difficult to meet the demand during peak steam demand periods. At the same time, when the unit is in deep peak-shaving operation, the boiler faces the limitation of low-load stable combustion and the problem of too low flue gas temperature at the denitrification inlet, which in turn limits the boiler's ability to perform deep peak-shaving. These two problems result in the evaporation of the boiler being greater than the demand of the steam turbine, and at the same time, the hot re-extraction of the steam turbine cannot be extracted due to the limitation of the main structure. Summary of the invention

[0005] In view of the above problems, the embodiments of the present application provide an industrial steam supply system and method capable of improving the flexibility of coal-fired units, which can greatly improve the flexibility of coal-fired units, enhance the low-load industrial steam supply capacity of steam turbines, and achieve the purpose of thermal and electrical decoupling. The technical solution is as follows:

[0006] The first aspect of the present application provides an industrial steam supply system capable of improving the flexibility of a coal-fired unit, comprising a main steam pipeline, part of the main steam on the main steam pipeline flows into a high bypass pipeline, a small back pressure machine and a generator are arranged on the high bypass pipeline, the small back pressure machine drives the generator to generate electricity through the main steam and transmits it to the power consumption system, and the exhaust steam of the small back pressure machine enters the boiler reheater; the steam discharged from the boiler reheater is divided into a low-pressure bypass pipeline and a medium-pressure cylinder steam inlet pipeline, the low-pressure bypass pipeline comprises a first pipeline and a reheat extraction pipeline, the reheat extraction pipeline is divided into a second pipeline and a third pipeline, the steam in the first pipeline is transported to a condenser, the steam in the second pipeline is transported to a heat exchanger for heat exchange with desalted water and then enters the condenser, and the steam in the third pipeline is transported to a heating steam manifold for external heating.

[0007] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in one embodiment, a make-up water heater is provided on the third pipeline, and the steam in the third pipeline is directly transported to the heating steam manifold or is transported to the heating steam manifold after heat exchange through the make-up water heater.

[0008] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in one embodiment, a heat storage tank is provided on the second pipeline, and the heat storage tank is a cold and hot water separation type heat storage tank, and the cold water in the heat storage tank comes from desalted water. The cold desalted water in the heat storage tank is transported to the heat exchanger to exchange heat with the steam in the second pipeline to increase the temperature, and then returns to the heat storage tank to be stored in the form of hot water.

[0009] For example, in the industrial steam supply system capable of improving the flexibility of coal-fired units provided in one embodiment, the hot water in the heat storage tank is directly transported to the deaerator as deaerator make-up water, or the hot water in the heat storage tank is transported to the make-up water heater to heat exchange with the steam in the third pipeline to increase the temperature before entering the deaerator.

[0010] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in one embodiment, a high bypass stop valve and a high bypass temperature and pressure reducing valve are further provided on the high bypass pipeline, through which part of the main steam on the main steam pipeline flows into the high bypass pipeline, and through which the high bypass temperature and pressure reducing valve allows exhaust steam from the small back pressure machine after work to enter the boiler reheater.

[0011] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in one embodiment, a heat exchanger inlet stop valve and a heat exchanger outlet stop valve are respectively provided at both ends of the heat exchanger on the second pipeline, and the steam in the second pipeline enters the heat exchanger through the heat exchanger inlet stop valve and the heat exchanger outlet stop valve to release heat and cool down, and then enters the condenser.

[0012] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in one embodiment, part of the steam discharged from the boiler reheater enters a low bypass pipeline, a low bypass stop valve A is provided on the low bypass pipeline, the steam passes through the low bypass pipeline and is divided into the first pipeline and the reheat extraction pipeline, the reheat extraction pipeline is divided into the second pipeline and the third pipeline, a low bypass temperature and pressure reducing valve and a low bypass stop valve B are provided on the first pipeline, the steam in the first pipeline is cooled and reduced in pressure by the low bypass temperature and pressure reducing valve and the low bypass stop valve B and then enters the condenser; a reheat extraction steam temperature and pressure reducing valve is provided on the third pipeline, the steam in the third pipeline is cooled and reduced in pressure by the reheat extraction steam temperature and pressure reducing valve and then directly enters the heating steam manifold.

[0013] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in one embodiment, a feed water heater inlet electric door and a feed water heater outlet electric door are respectively provided at both ends of the feed water heater, and a feed water heater bypass electric door connected in parallel with the feed water heater is provided downstream of the reheat extraction steam temperature and pressure reducing valve on the third pipeline.

[0014] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in one embodiment, a water supply bypass inlet electric door is provided on the pipeline connecting the heat storage tank and the water supply heater, a water supply main line electric door is provided on the pipeline connecting the heat storage tank and the deaerator, and a water supply bypass outlet electric door is provided on the pipeline connecting the water supply heater and the deaerator.

[0015] The second aspect of the present application provides an industrial steam supply method capable of improving the flexibility of coal-fired units, utilizing the steam in the third pipeline to meet the steam demand of industrial heat users during peak steam consumption periods, comprising the following steps: Step 1: Open the high bypass stop valve, and control the steam flow in the high bypass pipeline through the high bypass temperature reduction and pressure reducing valve, while the steam passes through the small back pressure machine to perform work, and the exhaust steam after the small back pressure machine performs work enters the boiler reheater; Step 2: Open the low bypass stop valve A and the reheat extraction steam temperature reduction and pressure reducing valve, and the steam in the boiler reheater is adjusted to a pressure and temperature that meets user needs through the reheat extraction steam temperature reduction and pressure reducing valve and then enters the third pipeline, the steam in the third pipeline directly enters the heating steam manifold through the make-up water heater bypass electric door, or the steam in the third pipeline passes through the make-up water heater and then enters the heating steam manifold.

[0016] For example, in an industrial steam supply method capable of improving the flexibility of coal-fired units provided in an embodiment, the steam in the third pipeline is used to meet the steam demand of industrial heat users during the peak period of steam consumption, including the following steps: Step 1: Open the high bypass stop valve, and control the steam flow in the high bypass pipeline through the high bypass temperature and pressure reducing valve. At the same time, the steam passes through the small back pressure machine to perform work, and the exhaust steam after the small back pressure machine performs work enters the boiler reheater; Step 2: Open the low bypass stop valve A and the heat exchanger inlet stop valve, and the steam in the boiler reheater enters the second pipeline. The steam in the second pipeline enters the heat exchanger to release heat and cool down, then open the heat exchanger outlet stop valve to enter the condenser, and the desalted water in the heat exchanger is stored in the heat storage tank after heat exchange and temperature rise.

[0017] For example, in the industrial steam supply method capable of improving the flexibility of coal-fired units provided in one embodiment, when there is no reheat extraction steam in the second pipeline, the water makeup bypass inlet electric door and the water makeup bypass outlet electric door are closed, and the water makeup bypass main line electric door is opened, and the hot water in the heat storage tank directly enters the deaerator as makeup water; when there is reheat extraction steam in the second pipeline, the water makeup bypass inlet electric door and the water makeup bypass outlet electric door are opened, and the water makeup bypass main line electric door is closed, and the hot water in the heat storage tank enters the deaerator as makeup water after the temperature is increased by the makeup water heater.

[0018] The beneficial effects of the industrial steam supply system and method of the present application that can improve the flexibility of coal-fired units are as follows: the present application sets a small back pressure machine on the high bypass pipeline, and integrates its power generation into the plant power system, and uses it for high-power auxiliary machines inside the power plant. Such an arrangement can use high-quality steam to do work, avoid the energy loss caused by direct temperature reduction and pressure reduction, and improve the thermal economy of bypass heating; part of the steam at the outlet of the boiler reheater is divided into three routes for use, one route is used for external heating through the heating steam manifold after temperature reduction and pressure reduction, one route enters the condenser, and the other route heats the desalted water through the heat exchanger and stores the hot water through the heat storage tank to achieve the purpose of energy storage; by setting up the heat storage tank, some excess heat can be stored, which improves the flexibility of boiler operation, and can operate at a higher load during deep peak regulation, avoiding various equipment modifications to achieve low-load operation, thereby improving the reliability and safety of operation. The hot water stored in the heat storage tank enters the deaerator as thermal system water after being heated by the water supply heater, and can also directly enter the deaerator as system water supply. At the same time, due to the heat exchange of the feed water heater, the use of cooling water can be effectively reduced, the steam extraction of industrial steam supply can be increased, the thermal power ratio of the coal-fired power unit can be further improved, and the thermal economy of the unit can be improved. This application can greatly improve the flexibility of the coal-fired unit, enhance the low-load industrial steam supply capacity of the steam turbine, achieve the purpose of thermal and electrical decoupling, and at the same time reduce the amount of engineering modifications to the boiler to meet the deep peak-shaving operation, so that the entire unit can better cope with the heating problem during the deep peak-shaving period. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the process flow of the industrial steam supply system of the present application which can improve the flexibility of the coal-fired unit. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0022] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0023] In a first aspect, the present application provides an industrial steam supply system capable of improving the flexibility of a coal-fired unit, such as Figure 1 As shown, it includes a main steam pipeline 1, part of the main steam on the main steam pipeline 1 flows into a high bypass pipeline 2, and a small back pressure machine 5 and a generator 4 are arranged on the high bypass pipeline 2. The small back pressure machine 5 drives the generator 4 to generate electricity through the main steam and transmits it to the power consumption system for use by auxiliary equipment inside the power plant; the exhaust steam of the small back pressure machine 5 enters the boiler reheater; the steam discharged from the boiler reheater is divided into a low-pressure bypass pipeline and a medium-pressure cylinder steam inlet pipeline, and the low-pressure bypass pipeline includes a first pipeline and a reheat extraction pipeline, and the reheat extraction pipeline 23 is divided into a second pipeline and a third pipeline, the steam in the first pipeline is transported to the condenser, the steam in the second pipeline is transported to the heat exchanger 25 for heat exchange with desalted water and then enters the condenser, and the steam in the third pipeline is transported to the heating steam manifold for external heating.

[0024] Among them, Figure 1 As shown, another part of the main steam on the main steam pipeline 1 flows into the high-pressure cylinder 6, and enters the boiler reheater through the high-pressure cylinder exhaust pipeline 7 and the high-pressure exhaust check valve 8 on the high-pressure cylinder exhaust pipeline 7.

[0025] Among them, Figure 1 As shown, the high bypass cooling water is transported to the high bypass cooling and pressure reducing valve 9 through a high bypass cooling water pipeline 10 and a high bypass cooling water stop valve 12 and a high bypass cooling water regulating valve 11 sequentially arranged on the high bypass cooling water pipeline 10 .

[0026] Among them, Figure 1 As shown, the steam discharged from the boiler reheater is also diverted to a fourth pipeline, which is a reheat steam pipeline 13 . The steam in the reheat steam pipeline 13 enters the intermediate pressure cylinder 17 .

[0027] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in an embodiment, Figure 1 As shown, a make-up water heater 34 is provided on the third pipeline, and the steam in the third pipeline is directly transported to the heating steam manifold or is transported to the heating steam manifold after heat exchange through the make-up water heater 34.

[0028] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in an embodiment, Figure 1 As shown, a heat storage tank 30 is provided on the second pipeline, and the heat storage tank 30 is a cold and hot water separation type heat storage tank. The cold water in the heat storage tank 30 comes from desalted water. The cold desalted water in the heat storage tank 30 is transported to the heat exchanger 25 through the cold water pipeline 28 and the water pump 29 arranged on the cold water pipeline 28, and is heat-exchanged with the steam in the second pipeline to increase the temperature, and then returned to the heat storage tank 30 through the hot water pipeline 27 to be stored in the form of hot water.

[0029] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in an embodiment, Figure 1 As shown, the hot water in the heat storage tank 30 is directly transported to the deaerator as deaerator make-up water, or the hot water in the heat storage tank 30 is transported to the make-up water heater 34 to heat exchange with the steam in the third pipeline and then enter the deaerator.

[0030] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in an embodiment, Figure 1 As shown, a high bypass stop valve 3 and a high bypass temperature and pressure reducing valve 9 are also provided on the high bypass pipeline 2. The high bypass stop valve 3 allows part of the main steam on the main steam pipeline to flow into the high bypass pipeline 2, and the high bypass temperature and pressure reducing valve 9 allows the exhaust steam after the small back pressure machine 5 does work to enter the boiler reheater.

[0031] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in an embodiment, Figure 1 As shown, a heat exchanger inlet stop valve 24 and a heat exchanger outlet stop valve 26 are respectively provided at both ends of the heat exchanger 25 on the second pipeline. Through the heat exchanger inlet stop valve 24 and the heat exchanger outlet stop valve 26, the steam in the second pipeline enters the heat exchanger 25 to release heat and cool down, and then enters the condenser.

[0032] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in an embodiment, Figure 1As shown, part of the steam discharged from the boiler reheater enters the low bypass pipeline 14, and a low bypass stop valve A15 is provided on the low bypass pipeline 14. After passing through the low bypass pipeline 14, the steam is divided into the first pipeline and the reheat extraction pipeline 23. The reheat extraction pipeline 23 is further divided into the second pipeline and the third pipeline. A low bypass temperature and pressure reducing valve 16 and a low bypass stop valve B21 are provided on the first pipeline, and the steam in the first pipeline is cooled and decompressed by the low bypass temperature and pressure reducing valve 16 and the low bypass stop valve B21 before entering the condenser; a reheat extraction temperature and pressure reducing valve 22 is provided on the third pipeline, and the steam in the third pipeline is cooled and decompressed by the reheat extraction temperature and pressure reducing valve 22 before directly entering the heating steam manifold.

[0033] Among them, Figure 1 As shown, the low bypass cooling water is delivered to the low bypass cooling and pressure reducing valve 16 through the low bypass cooling water pipeline 20 and the low bypass cooling water stop valve 19 and the low bypass cooling water regulating valve 18 sequentially arranged on the low bypass cooling water pipeline 20 .

[0034] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in an embodiment, Figure 1 As shown, a feed water heater inlet electric door 35 and a feed water heater outlet electric door 36 are respectively provided at both ends of the feed water heater 34, and a feed water heater bypass electric door 37 connected in parallel with the feed water heater 34 is provided downstream of the reheat extraction steam temperature reduction and pressure reducing valve 22 on the third pipeline.

[0035] For example, in an industrial steam supply system capable of improving the flexibility of a coal-fired unit provided in an embodiment, Figure 1 As shown, a water replenishment bypass inlet electric door 32 is provided on the pipeline connecting the heat storage tank 30 and the water replenishment heater 34, a water replenishment main line electric door 31 is provided on the pipeline connecting the heat storage tank 30 and the deaerator, and a water replenishment bypass outlet electric door 33 is provided on the water replenishment pipeline 38 connecting the water replenishment heater 34 and the deaerator.

[0036] The operation method of the heat storage tank 30 is as follows: during general industrial steam supply, the steam supplied by the heating steam manifold is no longer recovered, so the thermal system needs to simultaneously supplement an equal amount of desalted water to achieve the effect of working medium balance.

[0037] (1) If there is no extraction steam in the unit's reheat extraction steam pipeline 23, close the water supply bypass inlet electric door 32 and the water supply bypass outlet electric door 33, open the water supply bypass main line electric door 31, and the hot water in the heat storage tank 30 directly enters the deaerator as makeup water; (2) If there is extraction steam in the unit's reheat extraction steam pipeline 23, open the water supply bypass inlet electric door 32 and the water supply bypass outlet electric door 33, and close the water supply bypass main line electric door 31. The hot water in the heat storage tank 30 is heated by the makeup water heater 34 and then enters the deaerator as makeup water, which can further improve the thermal economy of the unit.

[0038] The second aspect of the present application provides an industrial steam supply method capable of improving the flexibility of a coal-fired unit. Industrial heat users may need a large amount of steam extraction to meet production needs during the peak period of steam consumption, but the amount of reheat steam extraction is limited by the unit load and the structural characteristics of the steam turbine, and the steam demand may not be met. In this case, the steam in the third pipeline is used to meet the steam demand of the industrial heat users during the peak period of steam consumption, including the following steps:

[0039] Step 1: Open the high bypass stop valve 3, control the steam flow in the high bypass pipeline 2 through the high bypass temperature and pressure reducing valve 9, and at the same time, the steam passes through the small back pressure machine 5 to perform work, and the exhaust steam after the small back pressure machine 5 performs work enters the boiler reheater;

[0040] Step 2: Open the low bypass stop valve A15 and the reheat extraction steam temperature and pressure reducing valve 22. The steam in the boiler reheater is adjusted to a pressure and temperature that meet user requirements through the reheat extraction steam temperature and pressure reducing valve 22 and then enters the third pipeline. The steam in the third pipeline directly enters the heating steam manifold through the make-up water heater bypass electric door 37, or the steam in the third pipeline enters the heating steam manifold after passing through the make-up water heater 34. In this case, no cooling water is required.

[0041] For example, in an industrial steam supply method capable of improving the flexibility of a coal-fired unit provided in an embodiment, Figure 1 As shown, in general, the boiler evaporation corresponds to a certain turbine load. When the unit is equipped with industrial steam supply, the boiler evaporation will be higher than the turbine load. When the turbine load is dispatched by the power grid, it is necessary to maintain the load at a lower load, and the boiler is limited by coal quality or denitrification problems, as well as other factors that prevent it from maintaining the evaporation corresponding to the turbine load, at this time, the present application can achieve thermoelectric decoupling through the heat storage tank 30 and the small back pressure machine 5, and recover the excess evaporation of the boiler, and use the second pipeline and the heat storage tank 30 to achieve thermoelectric decoupling, including the following steps:

[0042] Step 1: Open the high bypass stop valve 3, control the steam flow in the high bypass pipeline 2 through the high bypass temperature and pressure reducing valve 9, and at the same time, the steam passes through the small back pressure machine 5 to perform work, and the exhaust steam after the small back pressure machine 5 performs work enters the boiler reheater;

[0043] Step 2: Open the low bypass stop valve A15 and the heat exchanger inlet stop valve 24, the steam in the boiler reheater enters the second pipeline, the steam in the second pipeline enters the heat exchanger 25 to release heat and cool down, then open the heat exchanger outlet stop valve 26 to enter the condenser, the desalted water in the heat exchanger 25 is heated up and stored in the heat storage tank 30.

[0044] For example, in an industrial steam supply method capable of improving the flexibility of a coal-fired unit provided in an embodiment, Figure 1 As shown, it also includes a method of using the hot water stored in the heat storage tank 30 to improve the economic efficiency of water replenishment. The hot water stored in the heat storage tank 30 has a high energy level and can be directly replenished into the deaerator. It can also be used as cooling water for industrial steam supply. Since the water replenishment heater 34 is a surface heater, unlike water spray cooling, its cooling will not increase the amount of steam. Therefore, compared with water spray cooling, it can increase the amount of steam extraction, so its economy will be better. In general industrial steam supply, the steam supplied by the heating steam manifold is no longer recovered, so the thermal system needs to simultaneously supplement an equal amount of desalted water to achieve the effect of working medium balance. When there is no reheat extraction steam in the second pipeline, the water makeup bypass inlet electric door 32 and the water makeup bypass outlet electric door 33 are closed, and the water makeup bypass main road electric door 31 is opened, and the hot water in the heat storage tank 30 directly enters the deaerator as makeup water; when there is reheat extraction steam in the second pipeline, the water makeup bypass inlet electric door 32 and the water makeup bypass outlet electric door 33 are opened, and the water makeup bypass main road electric door 31 is closed, and the hot water in the heat storage tank 30 is heated by the makeup water heater 34 and then enters the deaerator as makeup water.

[0045] Examples of applications of the industrial steam supply system and method of the present application that can improve the flexibility of coal-fired units:

[0046] 1. When the power generation of the unit is 20% of the rated load, and the minimum evaporation of the boiler is 30% of the rated load, the 10% excess steam evaporated by the boiler enters the high bypass pipeline 2 to drive the small back pressure machine 5 to generate electricity, and the exhaust steam of the small back pressure machine 5 enters the boiler reheater. The excess 10% steam at the outlet of the boiler reheater is supplied to the outside through the reheat extraction pipeline 23. The excess part that cannot be used by the heat user enters the heat exchanger 25 to heat the desalted water, and the hot water is stored in the heat storage tank 30. If the excess 10% steam cannot meet the needs of the heat user, the extraction steam at the outlet of the boiler reheater can be increased, and the heat exchanger inlet stop valve 24 and the heat exchanger outlet stop valve 26 of the heat exchanger 25 are closed at the same time, so that the heat exchanger 25 is out of operation.

[0047] 2. When the power generation of the unit is 20% of the rated load, and the minimum evaporation capacity of the boiler can also maintain 20% of the rated load, but the hot re-extraction capacity is insufficient, the evaporation capacity of the boiler can be increased, and the reheat extraction capacity can be improved through the high bypass line 2 and the low bypass line 14 without increasing the power generation of the unit, so as to achieve the purpose of meeting the needs of heat users.

[0048] Although the embodiments of the present application have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. An industrial steam supply system capable of improving the flexibility of coal-fired units, characterized in that: include: The main steam pipeline, part of the main steam on the main steam pipeline flows into the high bypass pipeline, A small back pressure machine and a generator are arranged on the pipeline. The small back pressure machine drives the generator to generate electricity through main steam and transmits it to the power consumption system. The exhaust steam of the small back pressure machine enters the boiler reheater. The steam discharged from the boiler reheater is divided into a low-pressure bypass pipeline and an intermediate-pressure cylinder steam inlet pipeline. The low-pressure bypass pipeline includes a first pipeline and a reheat extraction pipeline. The reheat extraction pipeline is divided into a second pipeline and a third pipeline. The steam in the first pipeline is transported to the condenser, the steam in the second pipeline is transported to the heat exchanger to exchange heat with desalted water and then enters the condenser. The steam in the third pipeline is transported to the heating steam manifold for external heating. A make-up water heater is provided on the third pipeline, and the steam in the third pipeline is directly transported to the heating steam manifold or is transported to the heating steam manifold after heat exchange by the make-up water heater; A heat storage tank is provided on the second pipeline, and the heat storage tank is a hot and cold water separation type heat storage tank. The cold water in the heat storage tank comes from desalted water. The cold desalted water in the heat storage tank is transported to the heat exchanger to heat exchange with the steam in the second pipeline to increase the temperature, and then returns to the heat storage tank to be stored in the form of hot water. The hot water in the heat storage tank is directly transported to the deaerator as deaerator make-up water, or the hot water in the heat storage tank is transported to the make-up water heater to heat exchange with the steam in the third pipeline and then enter the deaerator.

2. The industrial steam supply system capable of improving the flexibility of coal-fired units according to claim 1, characterized in that: A high bypass stop valve and a high bypass temperature and pressure reducing valve are also provided on the high bypass pipeline. The high bypass stop valve allows part of the main steam on the main steam pipeline to flow into the high bypass pipeline, and the high bypass temperature and pressure reducing valve allows the exhaust steam after the small back pressure machine does work to enter the boiler reheater.

3. The industrial steam supply system capable of improving the flexibility of coal-fired units according to claim 1, characterized in that: A heat exchanger inlet stop valve and a heat exchanger outlet stop valve are respectively provided at both ends of the heat exchanger on the second pipeline, through which the steam in the second pipeline enters the heat exchanger to release heat and cool down, and then enters the condenser.

4. The industrial steam supply system capable of improving the flexibility of coal-fired units according to claim 1, characterized in that: Part of the steam discharged from the boiler reheater enters the low bypass pipeline, and a low bypass stop valve A is provided on the low bypass pipeline. After passing through the low bypass pipeline, the steam is divided into the first pipeline and the reheat extraction pipeline. The reheat extraction pipeline is divided into the second pipeline and the third pipeline. A low bypass temperature and pressure reducing valve and a low bypass stop valve B are provided on the first pipeline. The steam in the first pipeline is cooled and decompressed by the low bypass temperature and pressure reducing valve and the low bypass stop valve B and then enters the condenser; a reheat extraction steam temperature and pressure reducing valve is provided on the third pipeline. The steam in the third pipeline is cooled and decompressed by the reheat extraction steam temperature and pressure reducing valve and then directly enters the heating steam manifold.

5. The industrial steam supply system capable of improving the flexibility of coal-fired units according to claim 4, characterized in that: A feed water heater inlet electric door and a feed water heater outlet electric door are respectively provided at both ends of the feed water heater, and a feed water heater bypass electric door connected in parallel with the feed water heater is provided downstream of the reheat extraction steam temperature reduction and pressure reducing valve on the third pipeline.

6. The industrial steam supply system capable of improving the flexibility of coal-fired units according to claim 5, characterized in that: A water supply bypass inlet electric door is provided on the pipeline connecting the heat storage tank and the water supply heater, a water supply main line electric door is provided on the pipeline connecting the heat storage tank and the deaerator, and a water supply bypass outlet electric door is provided on the pipeline connecting the water supply heater and the deaerator.

7. An industrial steam supply method capable of improving the flexibility of a coal-fired unit, comprising the industrial steam supply system capable of improving the flexibility of a coal-fired unit as claimed in any one of claims 1 to 6, characterized in that: Utilizing the steam in the third pipeline to meet the steam demand of industrial heat users during the peak period of steam consumption includes the following steps: Step 1: Open the high bypass stop valve, control the steam flow in the high bypass pipeline through the high bypass temperature and pressure reducing valve, and at the same time, the steam passes through the small back pressure machine to do work, and the exhaust steam after the small back pressure machine does work enters the boiler reheater; Step 2: Open the low bypass stop valve A and the reheat extraction steam temperature and pressure reducing valve. The steam in the boiler reheater is adjusted to a pressure and temperature that meet user requirements through the reheat extraction steam temperature and pressure reducing valve and then enters the third pipeline. The steam in the third pipeline directly enters the heating steam manifold through the make-up water heater bypass electric door, or the steam in the third pipeline enters the heating steam manifold after passing through the make-up water heater.

8. The industrial steam supply method capable of improving the flexibility of coal-fired units according to claim 7, characterized in that: Thermoelectric decoupling is achieved by using the second pipeline and the heat storage tank, comprising the following steps: Step 1: Open the high bypass stop valve, control the steam flow in the high bypass pipeline through the high bypass temperature and pressure reducing valve, and at the same time, the steam passes through the small back pressure machine to do work, and the exhaust steam after the small back pressure machine does work enters the boiler reheater; Step 2: Open the low bypass stop valve A and the heat exchanger inlet stop valve, the steam in the boiler reheater enters the second pipeline, the steam in the second pipeline enters the heat exchanger to release heat and cool down, then open the heat exchanger outlet stop valve to enter the condenser, the desalted water in the heat exchanger is heated up by heat exchange and stored in the heat storage tank.

9. The industrial steam supply method capable of improving the flexibility of coal-fired units according to claim 8, characterized in that: When there is no reheat extraction steam in the second pipeline, the water supply bypass inlet electric door and the water supply bypass outlet electric door are closed, and the water supply bypass main road electric door is opened, and the hot water in the heat storage tank directly enters the deaerator as water supply; When there is reheat extraction steam in the second pipeline, the water makeup bypass inlet electric door and the water makeup bypass outlet electric door are opened, and the water makeup bypass main line electric door is closed. The hot water in the heat storage tank is heated by the water makeup heater and then enters the deaerator as makeup water.

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