Backpressure turbine heat and steam supply system capable of achieving isolated network operation

Abstract

The invention discloses a back pressure turbine heat and steam supply system capable of achieving isolated network operation. The back pressure turbine heat and steam supply system comprises a main steam pipeline, a back pressure turbine, a high-pressure cylinder, a reheater and an industrial steam supply pipeline. An outlet of the main steam pipeline is communicated with an inlet of the backpressure turbine through a backpressure turbine main steam valve and a backpressure turbine control valve, the outlet of the main steam pipeline is communicated with an inlet of the high-pressure cylinder through a high-pressure main steam valve and a high-pressure control valve, and the outlet of the main steam pipeline is communicated with an inlet of the reheater through a high bypass control valve and a high-pressure bypass. An outlet of the main steam pipeline is divided into two paths after passing through a newly-added bypass and a newly-added bypass adjusting valve, one path is communicated with an industrial steam supply pipeline through a steam supply pressure adjusting valve and a second desuperheater, and the other path is communicated with an inlet of a reheater through a steam inlet shut-off door, a steam ejector and a first desuperheater. The system can improve the peak regulation capacity of the unit and the flexibility of steam and heat supply.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of thermal power generation and cogeneration, and relates to a back pressure turbine heat supply and steam supply system capable of realizing isolated network operation. BACKGROUND

[0002] Under the background of "carbon peak and carbon neutral", improving energy utilization efficiency and increasing renewable energy consumption capacity have become the core direction of the development of the power industry. Coal-fired power generating units, as the cornerstone of China's power supply, are changing from main power supply to peak shaving power supply and guarantee power supply, and are bearing the increasing demand for winter heating and industrial steam supply. Under this situation, how to realize flexible peak shaving and efficient energy supply of thermal power generating units and meet the demand for high-grade industrial steam has become a key problem to be solved in the industry.

[0003] The existing heat supply and steam supply technology of thermal power generating units mainly has the following two mainstream modes and their inherent defects: 1. Steam extraction heat supply technology of pure condensing steam turbine This is the most widely used heat supply modification scheme at present. Its principle is to open a steam extraction port on the medium and low pressure connecting pipe of the pure condensing steam turbine to extract part of the steam that has done part of the work for heat supply.

[0004] Defect one: unreasonable utilization of energy grade, huge loss of power generation.

[0005] Extracting part of the steam with high parameters and high grades for low-grade heat supply is a typical "high-quality low use". This part of the extracted steam can continue to expand in the subsequent stages of the steam turbine to do a lot of high-value work. Therefore, every ton of steam extracted is accompanied by hundreds of kilowatt-hour loss of power generation, resulting in a decrease in the power supply coal consumption of the unit during the heat supply period, and sometimes even an increase, which is not high in "quality and efficiency" of energy utilization.

[0006] Defect two: "heat determines electricity" contradiction is prominent, peak shaving capacity is limited.

[0007] When steam extraction heat supply is used, the power generation of the unit is strongly coupled with the heat supply. In order to meet the heat load demand, the unit has to maintain a high power operation, which seriously weakens its deep peak shaving capacity and cannot meet the requirements of flexibility of the power grid. When the heat load is large, the unit cannot operate at a reduced load; when there is no need for heat supply, its efficiency is also lower than that of the pure condensing condition.

[0008] Defect three: steam supply parameters (pressure and temperature) are limited and difficult to meet the needs of high-end industries.

[0009] The steam parameters of the extraction port are limited by the flow design of the steam turbine, and generally only steam with a low pressure (such as 0.8-1.5 MPa) can be provided. For many industrial users in the chemical, pharmaceutical, food processing and other industries that require higher pressure (such as 2.5 MPa or more), the existing technology is often unable to meet the requirements, or additional pressurizing equipment is needed, resulting in a complex system and increased energy consumption.

[0010] 2. Back pressure turbine direct heating technology The technology uses a back pressure turbine to directly supply heat or steam to the user by using the exhaust steam. The technical defects are: poor flexibility, and the "heat determines electricity" characteristic is rigid.

[0011] The power generation of the back pressure unit is completely dependent on the exhaust steam flow (i.e. the heat load). When the steam consumption of the industrial user fluctuates or is interrupted, the power generation of the unit will also fluctuate sharply or even stop, and the unit almost has no grid peak shaving capability. This makes the operation of the back pressure unit heavily dependent on stable heat users, which has poor adaptability in the current electricity market environment and high investment risk.

[0012] In summary, the existing technology is in a dilemma of "high efficiency but low flexibility, and high flexibility but low efficiency". The pure condensation extraction scheme is relatively flexible but has low energy utilization efficiency and low steam quality; the back pressure machine scheme has high efficiency and high steam quality but is not flexible in operation. In addition, although steam ejectors are mature fluid machines and are commonly used in power plants for auxiliary purposes such as deaerator steam sources and vacuum extraction, they have never been systematically and large-scale applied to solve the above-mentioned core "heat and electricity contradiction" and energy grade improvement problem. SUMMARY

[0013] The purpose of the present application is to overcome the above-mentioned defects of the prior art, and to provide a back pressure machine heating and steam supply system capable of implementing isolated grid operation, which can improve the peak shaving capability of the unit and the flexibility of steam and heat supply.

[0014] To achieve the above-mentioned purpose, the present application discloses a back pressure machine heating and steam supply system capable of implementing isolated grid operation, which comprises a main steam pipeline, a back pressure machine, a high pressure cylinder, a reheater and an industrial steam supply pipeline. The outlet of the main steam pipeline is connected to the inlet of the back pressure machine through a back pressure machine main valve and a back pressure machine regulating valve, the outlet of the main steam pipeline is connected to the inlet of the high pressure cylinder through a high pressure main valve and a high pressure regulating valve, the outlet of the main steam pipeline is connected to the inlet of the reheater through a high bypass regulating valve and a high pressure bypass, and the outlet of the main steam pipeline is divided into two paths after passing through a newly added bypass and a newly added bypass regulating valve, one of the two paths is connected to the industrial steam supply pipeline through a steam supply pressure regulating valve and a second desuperheater, and the other path is connected to the inlet of the reheater through a steam inlet shut-off valve, a steam ejector and a first desuperheater.

[0015] Further, the exhaust port of the back pressure machine is connected with the inlet of the low pressure cylinder through a first exhaust check valve.

[0016] Further, the exhaust port of the back pressure machine is connected with the inlet of the second desuperheater through a second exhaust check valve.

[0017] Further, the exhaust port of the high pressure cylinder is connected with the inlet of the reheater through a high exhaust check valve.

[0018] Further, the outlet of the reheater is divided into three paths, wherein the first path is connected with the inlet of the steam ejector through a steam extraction shutoff valve and a steam extraction regulating valve, the second path is connected with the inlet of the medium pressure cylinder through a medium pressure main steam valve and a medium pressure regulating valve, and the third path is connected with the inlet of the condenser through a low bypass regulating valve.

[0019] Further, the exhaust port of the medium pressure cylinder is connected with the inlet of the low pressure cylinder through an exhaust pipeline.

[0020] Further, the steam extraction port of the medium pressure cylinder is connected with the inlet of the condenser through a steam extraction check valve, a steam extraction electric valve and a heat releasing side of a heat network heat exchanger, and the exhaust port of the low pressure cylinder is connected with the inlet of the condenser.

[0021] Further, an electric heater is further included, and the heat absorbing side outlet of the heat network heat exchanger is connected with the electric heater.

[0022] Further, a first generator is further included, and the back pressure machine is connected with the first generator.

[0023] Further, a second generator is further included, and the high pressure cylinder, the medium pressure cylinder and the low pressure cylinder are connected with the second generator.

[0024] The present application has the following beneficial effects: The back pressure machine heat supply and steam supply system capable of realizing isolated network operation directly extracts main steam from a boiler to drive a back pressure machine in specific operation, so as to avoid the problem that the steam flow rate in the reheater tube bundle is too low and the cooling capacity is insufficient at low load, which easily causes the safety accidents of reheater over-temperature and pipe burst. Therefore, the present application adds a steam ejector to recycle the reheated steam at the outlet of the reheater, introduces a high pressure main steam through a newly added bypass to participate in the pressure increase of the recycled steam, and the mixed steam after pressure increase is cooled by a first desuperheater and then reenters the reheater, so as to ensure that the reheater tube bundle is fully cooled and the over-temperature risk is fundamentally avoided. In addition, the application range of the "back pressure machine + steam ejector + newly added bypass" high-efficiency steam supply mode is expanded from high load to full load range, including deep peak regulation conditions, which greatly improves the flexibility and feasibility of the system and the peak regulation capacity. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description only some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0026] Figure 1 The structural diagram of the present application.

[0027] Wherein, 1 is a back pressure machine, 2 is a high pressure cylinder, 3 is a medium pressure cylinder, 4 is a low pressure cylinder, 5 is a reheater, 6 is a condenser, 7 is a heat network heat exchanger, 8 is an electric heater, 9 is a second desuperheater, 10 is a first generator, 11 is a second generator, 12 is a newly added bypass regulating valve, 13 is a steam supply pressure regulating valve, 14 is an inlet steam shutoff door, 15 is a second exhaust back pressure valve, 16 is a first exhaust back pressure valve, 17 is a back pressure machine main steam valve, 18 is a back pressure machine regulating valve, 19 is a extraction regulating valve, 20 is a extraction shutoff door, 21 is a high pressure main steam valve, 22 is a high pressure regulating valve, 23 is a high bypass regulating valve, 24 is a high exhaust back pressure valve, 25 is a extraction back pressure valve, 26 is a extraction electric door, 27 is a medium pressure regulating valve, 28 is a medium pressure main steam valve, 29 is a low bypass regulating valve, 30 is a steam ejector, and 31 is a first desuperheater. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0029] In the description of the present application, it should be understood that the terms “include” and “contain” indicate the existence of described features, whole, steps, operations, elements and / or components, but do not exclude the existence or addition of one or more other features, whole, steps, operations, elements, components and / or sets thereof.

[0030] It should also be understood that the terms used in the present application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, unless otherwise clearly indicated by the context, the singular forms “a”, “an” and “the” are intended to include the plural forms.

[0031] It should be further understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items, and that the term "at least one of A and / or B" means A or B or both A and B. In addition, the character " / " as used herein generally indicates an "or" relationship between the associated objects.

[0032] It should be understood that, even though the terms first, second, third, etc. can be used herein to describe various ranges or elements, these ranges or elements should not be limited by these terms. These terms are only used to distinguish one range or element from another. For example, a first range could be termed a second range without departing from the scope of the embodiments.

[0033] The word "if" as used herein means "when" or "upon" or "in response to a determination" or "in response to a detection," depending on the context. Similarly, the phrase "if it is determined" or "if [a stated condition or event] is detected" can mean "when it is determined" or "in response to a determination" or "when [a stated condition or event] is detected" or "in response to a detection [of a stated condition or event]," depending on the context.

[0034] In order to make the purposes, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Generally, the components of the embodiments of the present application described here and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0035] Various structural schematic diagrams according to the disclosed embodiments of the present application are shown in the accompanying drawings. These diagrams are not drawn to scale, in which some details are exaggerated for the purpose of clarity, and some details can be omitted. The shapes of various regions, layers, and their relative sizes and positional relationships shown in the diagrams are only exemplary, and in actuality, there can be deviations due to manufacturing tolerances or technical limitations, and a person skilled in the art can additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0036] Embodiment One REFERENCE Figure 1 The back pressure machine heat supply and steam supply system capable of realizing isolated network operation comprises a main steam pipeline, a back pressure machine 1, a high pressure cylinder 2, a reheater 5 and an industrial steam supply pipeline; The outlet of the main steam pipeline is connected with the inlet of the back pressure machine 1 through a back pressure machine main steam valve 17 and a back pressure machine regulating valve 18, is connected with the inlet of the high pressure cylinder 2 through a high pressure main steam valve 21 and a high pressure regulating valve 22, is connected with the inlet of the reheater 5 through a high pressure bypass regulating valve 23 and a high pressure bypass, and is divided into two routes after passing through a newly added bypass and a newly added bypass regulating valve 12, wherein one route is connected with the industrial steam supply pipeline through a steam supply regulating valve 13 and a second desuperheater 9, and the other route is connected with the inlet of the reheater 5 through a steam inlet shutoff valve 14, a steam ejector 30 and a first desuperheater 31.

[0037] It should be noted that in the working process, the main steam enters the back pressure machine 1 and the high pressure cylinder 2, that is, the main steam is directly extracted from the boiler to drive the back pressure machine 1, which will cause a large reduction in the steam flow rate flowing into the reheater 5, and at low load, this will cause the steam flow rate in the reheater 5 tube bundle to be too low, and the cooling capacity is insufficient, which is extremely prone to cause safety accidents such as overheating and pipe explosion of the reheater 5. Therefore, the steam ejector 30 is added to recycle the hot reheated steam at the outlet of the reheater 5, a high pressure main steam is introduced through the newly added bypass to participate in the pressure increase of the recycled steam, and the mixed steam is appropriately cooled by the first desuperheater 31 and then reenters the reheater 5, so that even in the case that the main steam is largely extracted, the tube bundle of the reheater 5 can be fully cooled, and the risk of overheating is fundamentally avoided. Therefore, the application range of the “back pressure machine + steam ejector + newly added bypass” high efficiency steam supply mode is expanded from high load to full load range, including deep peak shaving conditions, which greatly improves the flexibility and feasibility of the technology.

[0038] In addition, the dynamic adjustable heat load system is introduced as a “virtual power grid” to balance the power generated by the back pressure machine 1, so as to maintain the frequency stability of the isolated network system. The back pressure machine 1 has the ability to safely and stably operate in the isolated network mode, and after the main power grid is disconnected, an independent micro power grid can be automatically formed to continuously supply power and steam to the plant equipment and key heat users.

[0039] The back pressure turbine 1 in the application plays a new role in the unit peak regulation, and exhibits unique and system-level advantages. The back pressure turbine 1 is a stable and efficient independent unit, so that the main steam turbine unit can effectively carry out deep peak regulation. The back pressure turbine 1 independently bears the basic and stable industrial heat load. The electric energy required by the heat load is generated by itself to meet the needs, which is a high-efficiency but fixed “heat and power unit”. At this time, the power generation of the main steam turbine unit can be freely and flexibly adjusted in a wide range from rated output to minimum technical output according to the peak regulation instruction of the power grid. In addition, when the output needs to be quickly increased, the inlet valve opening of the back pressure turbine 1 can be slightly opened, and the power generation of several megawatts can be quickly increased in a few seconds to tens of seconds, and the influence on the exhaust parameters is small. This rapid power support is very valuable for stabilizing the frequency of isolated network or responding to the AGC (automatic generation control) instruction of the power grid.

[0040] The application couples the back pressure turbine 1 and the steam ejector 30 to reconstruct the energy flow of the power plant, and solves the contradiction between “efficiency” and “flexibility” in the prior art. By introducing the main steam into the back pressure turbine 1 for expansion and power generation, industrial steam supply can be realized in a wide load range.

[0041] Embodiment two In order to further improve the present application, reference is made to Figure 1 The back pressure turbine heat and steam supply system capable of realizing isolated network operation comprises a back pressure turbine 1, a high-pressure cylinder 2, a medium-pressure cylinder 3, a low-pressure cylinder 4, a reheater 5, a condenser 6, a heat network heat exchanger 7, an electric heater 8, a second desuperheater 9, a first generator 10, a second generator 11, a newly added bypass valve 12, a steam supply pressure regulating valve 13, an inlet valve 14, a second exhaust check valve 15, a first exhaust check valve 16, a back pressure turbine main valve 17, a back pressure turbine regulating valve 18, a steam extraction regulating valve 19, a steam extraction valve 20, a high-pressure main valve 21, a high-pressure regulating valve 22, a high-pressure bypass valve 23, a high-pressure exhaust check valve 24, a steam extraction check valve 25, a steam extraction electric valve 26, a medium-pressure regulating valve 27, a medium-pressure main valve 28, a low-pressure bypass valve 29, a steam ejector 30 and a first desuperheater 31. The outlet of the main steam pipeline is connected with the inlet of the back pressure turbine 1 through the back pressure turbine main valve 17 and the back pressure turbine regulating valve 18, the outlet of the main steam pipeline is connected with the inlet of the high-pressure cylinder 2 through the high-pressure main valve 21 and the high-pressure regulating valve 22, the outlet of the main steam pipeline is connected with the inlet of the reheater 5 through the high-pressure bypass valve 23 and the high-pressure bypass, and the outlet of the main steam pipeline is divided into two routes after the newly added bypass and the newly added bypass valve 12, one of which is connected with the industrial steam pipeline through the steam supply pressure regulating valve 13 and the second desuperheater 9, and the other of which is connected with the inlet of the reheater 5 through the inlet valve 14, the steam ejector 30 and the first desuperheater 31.

[0042] The exhaust port of the back pressure turbine 1 is connected to the inlet of the low pressure cylinder 4 through the first exhaust check valve 16, and is connected to the inlet of the second desuperheater 9 through the second exhaust check valve 15. The exhaust port of the high pressure cylinder 2 is connected to the inlet of the reheater 5 through the high pressure exhaust check valve 24. The outlet of the reheater 5 is divided into three paths, wherein the first path is connected to the inlet of the steam ejector 30 through the extraction shutoff valve 20 and the extraction control valve 19, the second path is connected to the inlet of the medium pressure cylinder 3 through the medium pressure main valve 28 and the medium pressure control valve 27, and the third path is connected to the inlet of the condenser 6 through the low bypass control valve 29.

[0043] The exhaust port of the medium pressure cylinder 3 is connected to the inlet of the low pressure cylinder 4 through the exhaust pipe, the extraction port of the medium pressure cylinder 3 is connected to the inlet of the condenser 6 through the extraction check valve 25, the extraction motor valve 26 and the heat releasing side of the heat network heat exchanger 7, the exhaust port of the low pressure cylinder 4 is connected to the inlet of the condenser 6, and the heat absorbing side outlet of the heat network heat exchanger 7 is connected to the electric heater 8.

[0044] The back pressure turbine 1 is connected to the first generator 10, and the high pressure cylinder 2, the medium pressure cylinder 3 and the low pressure cylinder 4 are connected to the second generator 11.

[0045] In this embodiment, the pressure of the industrial steam supply is 1.5-4 MPa, a part of the exhaust steam of the back pressure turbine 1 enters the steam inlet pipe of the low pressure cylinder 4 through the first exhaust check valve 16, and the other part of the steam provides industrial steam after passing through the second exhaust check valve 15. When the load of the steam turbine unit is low, the exhaust pressure and flow of the back pressure turbine 1 cannot meet the demand of the industrial steam, so a bypass is added to introduce appropriate main steam to supplement the industrial steam supply of the back pressure turbine 1, and the steam supply pressure stabilizing valve 13 is used to ensure the stability of the industrial steam supply pressure, and the second desuperheater 9 is used to control the temperature of the industrial steam supply. Due to the addition of the back pressure turbine 1, the whole system is divided into two relatively independent power generation units, and the back pressure turbine 1 bears a part of the heat and power, which is specially responsible for supplying high-grade and stable industrial steam. The power generated by the back pressure turbine 1 is used for internal use of the power plant, which can be used as an auxiliary system power source, and can guarantee the steam turbine unit to continue generating power when the power grid fails, and can continue to provide stable power in a small range, realizing isolated grid operation. Therefore, "power generation" is no longer the behavior of a single main body of the steam turbine unit, but is completed by two generators. The generator of the steam turbine unit can be greatly adjusted to respond to the peak demand of the power grid, while the power generated by the back pressure turbine 1 and the core industrial heat supply remain stable and are not affected.

[0046] The power generated by the back pressure turbine 1 is consumed by the power plant load system, including the power consumption of the pumps, fans, lighting, control system and other electrical equipment necessary for the operation of the power plant. In terms of heating, the back pressure turbine 1 can also play a strong auxiliary role. Under normal circumstances, the hot water for residential users of the heat network is provided by the fourth stage extraction steam or the fifth stage extraction steam of the steam turbine. When the unit is deeply peaking, the heat carried by this part of the extraction steam is insufficient. At this time, the power output by the back pressure turbine 1 will be used to heat the heat network outlet water, and the heat network outlet water will be controlled to be within 70-80°C through the electric heater 8 to meet the heat load demand of civil heating. In addition, the condensate water of the power plant can also be heated to produce auxiliary low-pressure steam, etc., forming a dynamic adjustable heat load system.

[0047] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the application being indicated by the following claims.

[0048] It is to be understood that the application is not limited to the specific structures described herein and illustrated in the accompanying drawings, and that since modifications and changes varied to fit particular conditions of use can be made by those skilled in the art without departing from the scope of the application. The scope of the application is limited only by the claims that follow.

[0049] The above description is only the preferred embodiment of the present application, not any limitation to the present application, any simple modification, change and equivalent structure change according to the technical essence of the present application to the above embodiment, still belongs to the protection scope of the technical scheme of the present application.

Claims

1. A back pressure turbine heat and steam supply system capable of operating in an isolated grid, characterized in that, The main steam pipeline, the back pressure machine (1), the high pressure cylinder (2), the reheater (5) and the industrial steam supply pipeline are included. The outlet of the main steam pipeline is connected with the inlet of the back pressure machine (1) through the back pressure machine main steam valve (17) and the back pressure machine regulating valve (18), the outlet of the main steam pipeline is connected with the inlet of the high pressure cylinder (2) through the high pressure main steam valve (21) and the high pressure regulating valve (22), the outlet of the main steam pipeline is connected with the inlet of the reheater (5) through the high pressure bypass valve (23) and the high pressure bypass, the outlet of the main steam pipeline is divided into two routes after the newly added bypass and the newly added bypass regulating valve (12), one of the two routes is connected with the industrial steam supply pipeline through the steam supply regulating valve (13) and the second desuperheater (9), the other route is connected with the inlet of the reheater (5) through the steam inlet shutoff valve (14), the steam ejector (30) and the first desuperheater (31).

2. The back pressure turbine heating and steam supply system capable of islanded operation according to claim 1, characterized in that, The low pressure cylinder (4) is further included, the steam outlet of the back pressure machine (1) is connected with the inlet of the low pressure cylinder (4) through the first steam outlet check valve (16).

3. The back pressure turbine heating and steam supply system capable of islanded operation according to claim 1, characterized in that, The steam outlet of the back pressure machine (1) is connected with the inlet of the second desuperheater (9) through the second steam outlet check valve (15).

4. The back pressure turbine heating and steam supply system capable of islanded operation according to claim 1, characterized in that, The steam outlet of the high pressure cylinder (2) is connected with the inlet of the reheater (5) through the high pressure outlet check valve (24).

5. The back pressure turbine heating and steam supply system capable of islanded operation according to claim 2, characterized in that, The condenser (6) is further included, the outlet of the reheater (5) is divided into three routes, the first route is connected with the inlet of the steam ejector (30) through the steam extraction shutoff valve (20) and the steam extraction regulating valve (19), the second route is connected with the inlet of the medium pressure cylinder (3) through the medium pressure main steam valve (28) and the medium pressure regulating valve (27), the third route is connected with the inlet of the condenser (6) through the low pressure bypass regulating valve (29).

6. The back pressure turbine heating and steam supply system capable of islanded operation according to claim 2, characterized in that, The steam outlet of the medium pressure cylinder (3) is connected with the inlet of the low pressure cylinder (4) through the steam outlet pipeline.

7. The back pressure turbine heating and steam supply system capable of islanded operation according to claim 5, characterized in that, The steam extraction outlet of the medium pressure cylinder (3) is connected with the inlet of the condenser (6) through the steam extraction check valve (25), the steam extraction electric valve (26) and the heat releasing side of the heat network heat exchanger (7), the steam outlet of the low pressure cylinder (4) is connected with the inlet of the condenser (6).

8. The back pressure turbine heating and steam supply system capable of islanded operation according to claim 7, characterized in that, The electric heater (8) is further included, the heat absorbing side outlet of the heat network heat exchanger (7) is connected with the electric heater (8). 9.The back pressure turbine heating and steam supply system capable of realizing islanded operation according to claim 1, characterized in that, The first generator (10) is further included, the back pressure machine (1) is connected with the first generator (10).

10. The back pressure turbine heating and steam supply system capable of islanded operation according to claim 2, characterized in that, The second generator (11) is further included, the high pressure cylinder (2), the medium pressure cylinder (3) and the low pressure cylinder (4) are connected with the second generator (11).

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