Efficient combined heat and power generation heat supply system adopting low-pressure steam cascade heating

Abstract

The invention provides an efficient combined heat and power generation heat supply system adopting low-pressure steam cascade heating. The system comprises an intermediate-pressure cylinder, a low-pressure cylinder section 1, a low-pressure cylinder section 2, a first pipeline, a second pipeline, a condenser, an absorption heat pump and a heat exchanger. In the heating and heat supply stage, part of exhaust steam of the low-pressure cylinder section 1 enters the low-pressure cylinder section 2, so that heat supply network water is sequentially heated by the condenser, the absorption heat pump and the heat exchanger; in the deep peak regulation stage, steam admission of the second section of the low-pressure cylinder is reduced to the lowest steam flow for maintaining safe cooling, so that heat supply network water is sequentially heated by the absorption heat pump and the heat exchanger; and in the rotor replacement stage, steam admission of the second section of the low-pressure cylinder is stopped, so that heat supply network water is sequentially heated by the absorption heat pump and the heat exchanger. The system can solve the problems that in the prior art, combined heat and power generation efficiency and flexibility are difficult to consider, low-temperature waste heat utilization is insufficient, and system modification economy is poor.

Description

Technical Field

[0001] This application relates to the field of thermoelectric technology, and more specifically, to a high-efficiency cogeneration heating system using low-pressure steam cascade heating. Background Technology

[0002] In the field of heating in coal-fired power plants, typical technical solutions include: 1) Medium and low pressure connecting pipe steam extraction heating technology, which involves adding regulating valve groups to the medium and low pressure connecting pipes of the steam turbine to extract steam from the medium-pressure cylinder exhaust or the low-pressure cylinder intake for heating the heating network as needed. This technology is mature, but it suffers from the problem of high-pressure steam (around 0.4 MPa) directly heating the heating water, resulting in a waste of high-quality capacity; 2) Absorption heat pump coupling technology, which uses steam extracted from the steam turbine as a driving heat source and raises the temperature of the heating network return water through a heat pump device, realizing deep utilization of low-temperature waste heat. However, this method has limited deep adjustment capability of the unit; 3) Low-pressure cylinder zero-output modification technology, by cutting off the steam inlet of the low-pressure cylinder to achieve full steam exhaust from the intermediate-pressure cylinder for heating, significantly improves the unit's heating capacity and has a high deep adjustment capability, but there is a phenomenon of high-pressure steam (around 0.4MPa) directly heating the heating water, resulting in a waste of high-quality capacity; 4) High back-pressure circulating water heating technology, which uses the condensate heat of exhaust steam to heat the circulating water, to achieve energy cascade utilization, but the unit's operation and adjustment capability is very weak due to the matching limitation between the return water temperature of the heating network and the unit's back pressure. Although the above technologies have improved the level of waste heat utilization on the turbine side in different dimensions, they still face common technical bottlenecks such as the difficulty in balancing the efficiency of cogeneration and the flexibility of unit operation, insufficient improvement of low-temperature waste heat quality, and poor economic efficiency of system modification. Summary of the Invention

[0003] This application provides at least one high-efficiency cogeneration heating system with low-pressure steam cascade heating. This system can improve the problems in the prior art, such as the difficulty in balancing the efficiency and flexibility of cogeneration, insufficient utilization of low-temperature waste heat, and poor economic efficiency of system transformation.

[0004] This application provides a high-efficiency cogeneration heating system for low-pressure steam cascade heating, including an intermediate-pressure cylinder, a low-pressure cylinder section 1, a low-pressure cylinder section 2, a first pipe, a second pipe, a condenser, an absorption heat pump, and a heat exchanger. The outlet of the intermediate-pressure cylinder is connected to the inlet of the low-pressure cylinder section 1. The first pipe connects the outlet of the low-pressure cylinder section 1 to the inlet of the low-pressure cylinder section 2. The outlet of the low-pressure cylinder section 2 is connected to the shell-side inlet of the condenser. The tube-side inlet of the condenser is connected to the outlet of the heating network water pipeline. The tube-side outlet of the condenser is connected to the tube-side inlet of the heat exchanger via the absorption heat pump. The tube-side outlet of the heat exchanger is connected to the heating end. The extraction end of the second pipe is connected to the first pipe. The outlet of the second pipe... The gas end is connected to the generator inlet of the absorption heat pump and the shell-side inlet of the heat exchanger, respectively. The shell-side outlet of the heat exchanger is connected to the evaporator inlet of the absorption heat pump. The evaporator outlet pipe of the absorption heat pump and the shell-side outlet pipe of the condenser are connected in one line. During the heating supply phase, part of the exhaust steam from section 1 of the low-pressure cylinder enters section 2 of the low-pressure cylinder so that the heating network water is heated sequentially by the condenser, the absorption heat pump, and the heat exchanger. During the deep peak shaving phase, the steam intake of section 2 of the low-pressure cylinder is reduced to the minimum steam flow rate to maintain safe cooling so that the heating network water is heated sequentially by the absorption heat pump and the heat exchanger. During the rotor replacement phase, the steam intake of section 2 of the low-pressure cylinder is stopped so that the heating network water is heated sequentially by the absorption heat pump and the heat exchanger.

[0005] In one alternative embodiment, the first pipeline is provided with a first flow regulating valve, and the second pipeline is provided with a second flow regulating valve.

[0006] In one alternative implementation, during the heating supply phase, the condenser heats the heating network water to 80°C, the absorption heat pump heats the heating network water to 85°C, and the heat exchanger heats the heating network water to 90–110°C.

[0007] In one optional implementation, during the heating phase, the exhaust pressure of the low-pressure cylinder section 1 is between 0.1 and 0.2 MPa.

[0008] In one optional implementation, during the heating phase, the exhaust back pressure of the second stage of the low-pressure cylinder is 54 kPa.

[0009] In one optional embodiment, a deaerator is further included, the inlet of which is connected to the shell-side outlet of the condenser, and the deaerator is used to deoxygenate the condensate output from the condenser.

[0010] In one alternative embodiment, a condensate pump is further included, which is disposed between the condenser and the deaerator.

[0011] In one alternative embodiment, a feedwater pump is also included, which is located at the outlet of the deaerator.

[0012] In one optional embodiment, the system further includes a first heater, a second heater, a third heater, and a fourth heater. The shell-side outlet of the condenser is connected sequentially to the inlet of the deaerator via the tube side of the first heater, the tube side of the second heater, the tube side of the third heater, and the tube side of the fourth heater. The shell-side inlet of the first heater is connected to the first extraction port located in the low-pressure cylinder section 2. The shell-side inlet of the second heater is connected to the second extraction port located in the low-pressure cylinder section 1. The shell-side inlet of the third heater is connected to the third extraction port located in the low-pressure cylinder section 1. The shell-side inlet of the fourth heater is connected to the fourth extraction port located in the intermediate-pressure cylinder.

[0013] In one optional embodiment, the shell-side outlet of the first heater is connected to the shell side of the condenser, the shell-side outlet of the second heater is connected to the shell side of the first heater, the shell-side outlet of the third heater is connected to the shell side of the second heater, and the shell-side outlet of the fourth heater is connected to the shell side of the third heater.

[0014] The above-mentioned technical solution of this application has the following beneficial technical effects:

[0015] The high-efficiency cogeneration heating system with low-pressure steam cascade heating in this application embodiment can achieve cascaded energy utilization, reduce high-quality steam waste, significantly improve the heating load fluctuation range (±30%), enhance the thermoelectric decoupling capability, improve the system's operational heating flexibility, and realize the replacement of rotor blades in the second stage of the low-pressure cylinder without shutting down the system, thereby reducing downtime losses. This can improve the problems in the prior art, such as the difficulty in balancing cogeneration efficiency and flexibility, insufficient utilization of low-temperature waste heat, and poor economic efficiency of system modification.

[0016] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. These drawings are incorporated in and constitute a part of this specification. They illustrate embodiments conforming to this application and, together with the specification, serve to explain the technical solutions of this application. It should be understood that the following drawings only show some embodiments of this application and should not be considered as limiting the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This illustration shows a schematic diagram of a high-efficiency cogeneration heating system with low-pressure steam cascade heating provided in an embodiment of this application;

[0019] In the picture:

[0020] 1. Intermediate-pressure cylinder; 2. Low-pressure cylinder section 1; 3. Low-pressure cylinder section 2; 4. First pipeline; 5. Second pipeline; 6. Condenser; 7. Absorption heat pump; 8. Heat exchanger; 9. First flow regulating valve; 10. Second flow regulating valve; 11. Deaerator; 12. Condensate pump; 13. Feed water pump; 14. First heater; 15. Second heater; 16. Third heater; 17. Fourth heater. Detailed Implementation

[0021] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0022] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0023] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0024] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0025] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0026] refer to Figure 1 This application provides a high-efficiency cogeneration heating system with low-pressure steam cascade heating. The system includes a medium-pressure cylinder 1, a low-pressure cylinder section 1 2, a low-pressure cylinder section 2 3, a first pipe 4, a second pipe 5, a condenser 6, an absorption heat pump 7, and a heat exchanger 8.

[0027] The outlet of intermediate pressure cylinder 1 is connected to the inlet of low pressure cylinder 1 section 2, so that the exhaust steam from intermediate pressure cylinder 1 can enter low pressure cylinder 1 section 2 to do work.

[0028] The first pipe 4 connects the outlet of the low-pressure cylinder 1 section 2 to the inlet of the low-pressure cylinder 2 section 3, so that the exhaust steam from the intermediate-pressure cylinder 1 can enter the low-pressure cylinder 2 section 3 to do work after the exhaust steam from the low-pressure cylinder 1 section 2 has done work (exhaust steam from the low-pressure cylinder 1 section 2).

[0029] The outlet of the low-pressure cylinder 2 section 3 is connected to the shell-side inlet of the condenser 6, so that the exhaust steam of the low-pressure cylinder 1 section 2 can enter the condenser 6 after the low-pressure cylinder 2 section 3 does work (exhaust steam of the low-pressure cylinder 2 section 3), where it releases heat and condenses into water.

[0030] The tube-side inlet of condenser 6 is connected to the outlet of the heating network water pipeline. The tube-side outlet of condenser 6 is connected to the tube-side inlet of heat exchanger 8 via absorption heat pump 7. The tube-side outlet of heat exchanger 8 is connected to the heating end. In other words, the heating network water can enter the heating end after passing through condenser 6, absorption heat pump 7, and heat exchanger 8 in sequence. Furthermore, the heating network water can be heated by condenser 6 when passing through condenser 6.

[0031] The extraction end of the second pipe 5 is connected to the first pipe 4, the first outlet of the second pipe 5 is connected to the generator inlet of the absorption heat pump 7, and the second outlet of the second pipe 5 is connected to the shell-side inlet of the heat exchanger 8. In other words, the exhaust steam from the low-pressure cylinder section 1 is divided into two paths. One path serves as the driving heat source for the absorption heat pump 7, heating the dilute lithium bromide solution in the generator and releasing high-temperature water vapor. This high-temperature water vapor releases heat in the condenser of the absorption heat pump 7 to heat the hot water passing through the absorption heat pump 7. The other path enters the heat exchanger 8 to directly release heat, further heating the hot water passing through the heat exchanger 8.

[0032] The shell-side outlet of heat exchanger 8 is connected to the evaporator inlet of absorption heat pump 7, allowing the exhaust steam from section 1 of the low-pressure cylinder to enter the evaporator of absorption heat pump 7 after releasing heat in heat exchanger 8 (heat exchanger 8 has a condensate drain, which is approximately 90°C). The condensate drain acts as a low-temperature heat source to evaporate the refrigerant (water). The evaporated gas is absorbed by a concentrated lithium bromide solution in the absorber of absorption heat pump 7, releasing absorbed heat to heat the heat network water passing through absorption heat pump 7. In other words, absorption heat pump 7 uses two methods to heat the heat network water.

[0033] The evaporator outlet pipe of the absorption heat pump 7 and the shell-side outlet pipe of the condenser 6 are connected in one line, so that the condensate from the heat exchanger 8 is sent out together with the condensate from the condenser 6 after passing through the absorption heat pump 7 (the condensate from the secondary heat release is about 50°C).

[0034] During the heating season, a portion of the exhaust steam from section 2 of low-pressure cylinder 1 enters section 3 of low-pressure cylinder 2 to perform work, thereby heating the heating network water sequentially through condenser 6, absorption heat pump 7, and heat exchanger 8. Specifically, the exhaust steam from section 3 of low-pressure cylinder 2 releases heat when condensed into water in condenser 6, providing the first heating of the heating network water. Absorption heat pump 7 uses the exhaust steam from section 2 of low-pressure cylinder 1 as its driving heat source and simultaneously introduces condensate from heat exchanger 8 to provide the second heating of the heating network water. Finally, the exhaust steam from section 2 of low-pressure cylinder 1 exchanges heat with the heating network water in heat exchanger 8 for the third heating of the heating network water.

[0035] During the deep peak shaving phase, the steam flow rate at the low-pressure cylinder section 2 is reduced to the minimum required for safe cooling, allowing the heating network water to be heated sequentially by the absorption heat pump 7 and the heat exchanger 8. Specifically, during the heating supply phase, if only a small portion of the exhaust from the low-pressure cylinder section 1 (e.g., 20 t / h) enters the low-pressure cylinder section 2 to maintain safe cooling of the cylinder, and the majority of the exhaust from the low-pressure cylinder section 1 directly enters the absorption heat pump 7 and the heat exchanger 8, then the condenser 6 cannot provide heating. The heating network water is only heated by the absorption heat pump 7 and the heat exchanger 8, which is sufficient to meet the heating requirements of the heating network water.

[0036] During the rotor replacement phase, steam intake to section 3 of the low-pressure cylinder 2 is stopped, allowing the heating network water to be heated sequentially by the absorption heat pump 7 and the heat exchanger 8. Specifically, during the deep peak shaving phase, if the first pipe 4 is closed, all exhaust from section 2 of the low-pressure cylinder 1 enters the absorption heat pump 7 and the heat exchanger 8. At this time, the condenser 6 cannot perform a heating function, and the heating network water is heated solely by the absorption heat pump 7 and the heat exchanger 8. Simultaneously, since section 3 of the low-pressure cylinder 2 operates with zero output, the rotor and blades of section 3 can be replaced without shutting down the system. This solves the problem of traditional high back-pressure heating requiring system shutdown for rotor blade replacement, thus improving the system's operational flexibility.

[0037] In some embodiments, the first pipeline 4 is provided with a first flow regulating valve 9, and the second pipeline 5 is provided with a second flow regulating valve 10. During operation, the exhaust gas of the low-pressure cylinder 1 section 2 can be adjusted by controlling the opening degree of the first flow regulating valve 9 and the second flow regulating valve 10, thereby adapting the system to different operating stages.

[0038] In some embodiments, during the heating supply phase, the condenser 6 heats the heating network water to 80°C, the absorption heat pump 7 heats the heating network water to 85°C, and the heat exchanger 8 heats the heating network water to 90–110°C. Of course, the above temperature parameters can be selected according to actual conditions and are not limited to the methods discussed above.

[0039] In some embodiments, during the heating phase, the exhaust pressure of section 2 of the low-pressure cylinder is 0.1–0.2 MPa. Compared to traditional heating modes (such as zero output from the low-pressure cylinder and extraction of steam from the medium-low pressure connecting pipe), which directly use 0.4 MPa steam (corresponding to a saturation temperature of approximately 143°C) to heat heating water that only needs to be heated to 90–110°C, reducing the exhaust pressure of section 2 of the low-pressure cylinder to 0.1–0.2 MPa (corresponding to a saturation temperature of 100–120°C) allows for a reasonable match with the final temperature of the heating water (90–110°C), thereby avoiding the waste of high-quality energy and helping to reduce heating coal consumption.

[0040] In some embodiments, during the heating phase, the exhaust back pressure of section 3 of low-pressure cylinder 2 is 54 kPa. At a back pressure of 54 kPa, the steam saturation temperature is approximately 83°C, creating a reasonable heat transfer temperature difference (ΔT≈3°C) with the target temperature of the heating return water in condenser 6 (first-stage heater) (45°C→80°C). Specifically, if the back pressure is too low (e.g., 30 kPa), although power generation increases, the exhaust temperature is too low (approximately 69°C), making it difficult to heat the heating water to 80°C. If the back pressure is too high (e.g., 80 kPa), the exhaust temperature increases (approximately 93°C), but the power generation significantly decreases, and directly heating the heating water leads to a waste of high-quality steam. Therefore, setting the exhaust back pressure of section 3 of low-pressure cylinder 2 to 54 kPa ensures efficient heat exchange while avoiding excessively large temperature differences at the hot end. loss.

[0041] In some embodiments, the system further includes a deaerator 11, the inlet of which is connected to the shell-side outlet of the condenser 6. The deaerator 11 is used to deoxygenate the condensate output from the condenser 6. In practical use, the deaerator 11 is used to remove dissolved oxygen and other non-condensable gases from the condensate and to supply deoxygenated water to the boiler or heating network system.

[0042] In some embodiments, the system further includes a condensate pump 12 disposed between the condenser 6 and the deaerator 11. In practical use, the condensate pump 12 is used to deliver condensate to the deaerator 11.

[0043] In some embodiments, the system further includes a feedwater pump 13, which is located at the outlet of the deaerator 11. In practical use, the feedwater pump 13 is used to deliver deaerated water to the boiler or heating network.

[0044] In some embodiments, the system further includes a first heater 14, a second heater 15, a third heater 16, and a fourth heater 17. The shell-side outlet of the condenser 6 is connected to the inlet of the deaerator 11 via the tube side of the first heater 14, the tube side of the second heater 15, the tube side of the third heater 16, and the tube side of the fourth heater 17 in sequence. The shell-side inlet of the first heater 14 is connected to the first extraction port provided in the low-pressure cylinder 2 section 3. The shell-side inlet of the second heater 15 is connected to the second extraction port provided in the low-pressure cylinder 1 section 2. The shell-side inlet of the third heater 16 is connected to the third extraction port provided in the low-pressure cylinder 1 section 2. The shell-side inlet of the fourth heater 17 is connected to the fourth extraction port provided in the intermediate-pressure cylinder 1. In practical use, the steam temperature entering the fourth heater 17 is the highest, followed by the steam temperature entering the third heater 16, then the steam temperature entering the second heater 15, and the steam temperature entering the first heater 14 is the lowest. Thus, these heaters can use the waste heat from the extracted steam to heat the condensate step by step, which can improve the overall efficiency of the system and reduce boiler fuel consumption.

[0045] In some embodiments, the shell-side outlet of the first heater 14 is connected to the shell side of the condenser 6, the shell-side outlet of the second heater 15 is connected to the shell side of the first heater 14, the shell-side outlet of the third heater 16 is connected to the shell side of the second heater 15, and the shell-side outlet of the fourth heater 17 is connected to the shell side of the third heater 16. This arrangement allows the condensate from each heater to be discharged into the preceding heater (low-temperature side), thereby fully recovering the waste heat in the condensate, reducing the consumption of high-grade steam extraction, and preventing heat waste caused by directly discharging the condensate into the condenser 6.

[0046] The high-efficiency cogeneration heating system with low-pressure steam cascade heating in this application embodiment can achieve cascaded energy utilization, reduce high-quality steam waste, significantly improve the heating load fluctuation range (±30%), enhance the thermoelectric decoupling capability, improve the system's operational heating flexibility, and realize the replacement of rotor blades of section 3 of the low-pressure cylinder without shutting down, thereby reducing downtime losses. It can improve the problems of existing technologies, such as the difficulty in balancing cogeneration efficiency and flexibility, insufficient utilization of low-temperature waste heat, and poor economic efficiency of system modification.

[0047] One or more embodiments in this specification are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this specification should be included within the protection scope of this application.

[0048] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A high-efficiency cogeneration heating system using low-pressure steam cascade heating, characterized in that, The system includes an intermediate-pressure cylinder, a low-pressure cylinder section 1, a low-pressure cylinder section 2, a first pipe, a second pipe, a condenser, an absorption heat pump, and a heat exchanger. The outlet of the intermediate-pressure cylinder is connected to the inlet of the low-pressure cylinder section 1. The first pipe connects the outlet of the low-pressure cylinder section 1 to the inlet of the low-pressure cylinder section 2. The outlet of the low-pressure cylinder section 2 is connected to the shell-side inlet of the condenser. The tube-side inlet of the condenser is connected to the outlet of the heating network water pipe. The tube-side outlet of the condenser is connected to the tube-side inlet of the heat exchanger via the absorption heat pump. The tube-side outlet of the heat exchanger is connected to the heating end. The exhaust end of the second pipe is connected to the first pipe. The exhaust end of the second pipe is connected to the generator inlet of the absorption heat pump and the shell-side inlet of the heat exchanger. The shell-side outlet of the heat exchanger is connected to the evaporator inlet of the absorption heat pump. The evaporator outlet pipe of the absorption heat pump and the shell-side outlet pipe of the condenser are combined into one line. During the heating and heat supply phase, part of the exhaust steam from the first section of the low-pressure cylinder enters the second section of the low-pressure cylinder so that the heating network water is heated sequentially by the condenser, the absorption heat pump, and the heat exchanger. During the deep peak shaving phase, the steam inlet of the low-pressure cylinder 2 is reduced to the minimum steam flow rate to maintain safe cooling, so that the heating network water is heated by the absorption heat pump and the heat exchanger in sequence. During the rotor replacement phase, the steam intake of the second stage of the low-pressure cylinder is stopped, so that the heating network water is heated sequentially by the absorption heat pump and the heat exchanger.

2. The high-efficiency cogeneration heating system with low-pressure steam cascade heating according to claim 1, characterized in that, The first pipeline is equipped with a first flow regulating valve, and the second pipeline is equipped with a second flow regulating valve.

3. The high-efficiency cogeneration heating system with low-pressure steam cascade heating according to claim 1, characterized in that, During the heating supply phase, the condenser heats the heating network water to 80°C, the absorption heat pump heats the heating network water to 85°C, and the heat exchanger heats the heating network water to 90-110°C.

4. The high-efficiency cogeneration heating system with low-pressure steam cascade heating according to claim 1, characterized in that, During the heating season, the exhaust pressure of the first stage of the low-pressure cylinder is between 0.1 and 0.2 MPa.

5. The high-efficiency cogeneration heating system with low-pressure steam cascade heating according to claim 1, characterized in that, During the heating season, the exhaust back pressure of the second stage of the low-pressure cylinder is 54 kPa.

6. The high-efficiency cogeneration heating system with low-pressure steam cascade heating according to claim 1, characterized in that, It also includes a deaerator, the inlet of which is connected to the shell-side outlet of the condenser, and the deaerator is used to deoxygenate the condensate output from the condenser.

7. The high-efficiency cogeneration heating system with low-pressure steam cascade heating according to claim 6, characterized in that, It also includes a condensate pump, which is located between the condenser and the deaerator.

8. The high-efficiency cogeneration heating system with low-pressure steam cascade heating according to claim 6, characterized in that, It also includes a water supply pump, which is located at the outlet of the deaerator.

9. The high-efficiency cogeneration heating system with low-pressure steam cascade heating according to claim 6, characterized in that, It also includes a first heater, a second heater, a third heater, and a fourth heater. The shell-side outlet of the condenser is connected to the inlet of the deaerator in sequence through the tube side of the first heater, the tube side of the second heater, the tube side of the third heater, and the tube side of the fourth heater. The shell-side inlet of the first heater is connected to the first extraction port located in the second section of the low-pressure cylinder. The shell-side inlet of the second heater is connected to the second extraction port located in the first section of the low-pressure cylinder. The shell-side inlet of the third heater is connected to the third extraction port located in the first section of the low-pressure cylinder. The shell-side inlet of the fourth heater is connected to the fourth extraction port located in the intermediate-pressure cylinder.

10. The high-efficiency cogeneration heating system with low-pressure steam cascade heating according to claim 9, characterized in that, The shell-side outlet of the first heater is connected to the shell side of the condenser, the shell-side outlet of the second heater is connected to the shell side of the first heater, the shell-side outlet of the third heater is connected to the shell side of the second heater, and the shell-side outlet of the fourth heater is connected to the shell side of the third heater.

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