Heat network drainage recovery system of combined heat and power unit based on cascade heat exchange

Abstract

The application discloses a heat network drain recovery system of a combined heat and power unit based on cascade heat exchange, which comprises a primary heat exchange subsystem and a secondary heat exchange subsystem. In the primary heat exchange subsystem, the upstream side of a heat network drain main pipe is communicated with the second inlet of a primary heat exchanger through a first branch, and then communicated with the downstream side of the heat network drain main pipe through the second outlet of the primary heat exchanger, a second branch and the second outlet of the primary heat exchanger. In the secondary heat exchange subsystem, the third inlet of a secondary heat exchanger is communicated with the heat network drain main pipe through a flow orifice, and then sequentially communicated with a condenser, a condensate pump, a fine treatment system and a shaft seal cooler. One branch of the shaft seal cooler is communicated with a feedwater system, and the other branch is communicated with the fourth inlet of the secondary heat exchanger through a third branch, enters the secondary heat exchanger, and then enters the feedwater system through the fourth branch. The application can efficiently and cascade recover the waste heat of the heat network drain.

Description

Technical Field

[0001] This invention relates to the field of combined heat and power (CHP) cascade utilization technology, and in particular to a CHP unit heat network condensate recovery system based on cascade heat exchange. Background Technology

[0002] When thermal power units operate for heating in winter, the condensate drains from the heating network heaters carry a large amount of high-quality heat energy, which has recycling value. Traditional designs typically recover the condensate drains directly to the unit's deaerator, which is economical. However, the large amount of heat energy contained in the condensate drains is not effectively utilized, resulting in energy waste. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, one object of the present invention is to propose a cogeneration unit heat network condensate recovery system based on cascade heat exchange, which can efficiently and in cascade recover waste heat from the heat network condensate.

[0004] According to an embodiment of the present invention, a cogeneration unit heat network condensate recovery system based on cascade heat exchange includes: a primary heat exchange subsystem, comprising: a heat network circulating water recovery pipeline, a primary heat exchanger, a heat network circulating water supply pipeline, a heat network heater, a condensate pump, and a heat network condensate header. The heat network circulating water recovery pipeline is connected to the first inlet of the primary heat exchanger via a first electrically operated isolation valve and a first manually operated isolation valve, and then connected to the heat network circulating water supply pipeline via the first outlet of the primary heat exchanger. The heat network circulating water supply pipeline is equipped with a second electrically operated isolation valve and a third manually operated isolation valve. The heat network heater is connected to the heat network condensate header via the condensate pump. The upstream side of the heat network condensate header is connected to the second inlet of the primary heat exchanger via a first branch, and then connected to the downstream side of the heat network condensate header via the second outlet of the primary heat exchanger and a second branch. The first branch is equipped with a third electrically operated isolation valve and a fourth manually operated isolation valve, and the second branch is equipped with a fourth electrically operated isolation valve and a third manually operated isolation valve. A fifth manual isolation valve is provided between the upstream and downstream sides of the heat network drain header; a secondary heat exchange subsystem includes: a flow orifice plate, a secondary heat exchanger, a condenser, a condensate pump, a fine treatment system, and a shaft seal cooler. The third inlet of the secondary heat exchanger is connected to the heat network drain header through the flow orifice plate. A first valve group is provided between the secondary heat exchanger and the flow orifice plate. Heat network drain water entering the secondary heat exchanger from the third inlet is adapted to pass through the third outlet of the secondary heat exchanger sequentially through the condenser, the condensate pump, the fine treatment system, and the shaft seal cooler. One path of the shaft seal cooler is connected to the feedwater system, and the other path enters the secondary heat exchanger through a third branch and the fourth inlet of the secondary heat exchanger. Then, from the fourth outlet of the secondary heat exchanger, it enters the feedwater system through the fourth branch. A second valve group is provided on the third branch, and a third valve group is provided on the fourth branch.

[0005] According to an embodiment of the present invention, the cogeneration unit heat network condensate recovery system based on cascade heat exchange utilizes the heat network return water with direct temperature rise requirements as a cold source to recover the first-stage high-grade heat of the heat network condensate, thereby improving the internal circulation energy efficiency of the heating process. The system also utilizes the low-temperature condensate after the shaft seal cooler as a refrigerant to perform secondary deep cooling on the heat network condensate after the first-stage heat exchange, thus efficiently and in a cascade manner recovering the waste heat from the heat network condensate.

[0006] In addition, the cogeneration unit heat network condensate recovery system based on cascade heat exchange according to the present invention may also have the following additional technical features: In some embodiments of the present invention, a second manual isolation valve is provided between the first branch and the second branch.

[0007] In some embodiments of the present invention, the heating network heater includes a first heating network heater and a second heating network heater, and the drain pump includes a first drain pump and a second drain pump. The first heating network heater and the second heating network heater are connected in parallel upstream of the heating network drain header, and the first drain pump is provided at the outlet of the first heating network heater, and the second drain pump is provided at the outlet of the second heating network heater.

[0008] In some embodiments of the present invention, the secondary heat exchange subsystem further includes: an online water quality monitoring instrument, which is installed at the inlet of the condenser to obtain water quality information of the heat network condensate, and when the heat network condensate meets the reuse requirements, the heat network condensate is returned to the condenser; when the heat network condensate does not meet the reuse requirements, it is directly discharged.

[0009] In some embodiments of the present invention, the water supply system includes: a plurality of low-pressure heaters connected in series, wherein the low-pressure heater closest to the shaft seal cooler is a first low-pressure heater, the third branch is connected upstream of the first low-pressure heater, the fourth branch is connected downstream of the first low-pressure heater, and a fourth valve group is also provided at the inlet of the first low-pressure heater.

[0010] In some embodiments of the present invention, four low-pressure heaters are provided, namely a first low-pressure heater, a second low-pressure heater, a third low-pressure heater, and a fourth low-pressure heater. The secondary heat exchange subsystem further includes a fifth branch, one end of which is connected to the upstream of the secondary heat exchanger, and the other end is connected between the third low-pressure heater and the fourth low-pressure heater. A fifth valve group is provided on the fifth branch.

[0011] In some embodiments of the present invention, the secondary heat exchange subsystem further includes a sixth branch, which is connected in parallel with the secondary heat exchanger, with one end connected upstream of the third inlet of the secondary heat exchanger and the other end connected downstream of the third outlet of the secondary heat exchanger.

[0012] In some embodiments of the present invention, multiple secondary heat exchange subsystems are provided, and the multiple secondary heat exchange subsystems are connected in parallel downstream of the heat network drain header.

[0013] In some embodiments of the present invention, the cogeneration unit heat network condensate recovery system based on cascade heat exchange further includes a deaerator recovery system, wherein the deaerator recovery system is connected in parallel with the secondary heat exchange subsystem downstream of the heat network condensate header.

[0014] In some embodiments of the present invention, the primary heat exchange subsystem includes a plurality of primary heat exchangers, which are arranged in parallel.

[0015] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the primary heat exchange subsystem of the cogeneration unit heat network condensate recovery system based on cascade heat exchange, according to some embodiments of the present invention.

[0017] Figure 2 This is a schematic diagram of the secondary heat exchange subsystem of the cogeneration unit heat network condensate recovery system based on cascade heat exchange, according to some embodiments of the present invention.

[0018] Figure label: 1. Heating network circulating water recovery pipeline; 2. First electric isolation valve; 3. First manual isolation valve; 4. Primary heat exchanger; 5. Second manual isolation valve; 6. Second electric isolation valve; 7. Third manual isolation valve; 8. Heating network circulating water supply pipeline; 9. Third electric isolation valve; 10. Fourth manual isolation valve; 11. Fourth electric isolation valve; 12. Fifth manual isolation valve; 13. Fifth electric isolation valve; 14. Flow orifice plate; 15. Sixth electric isolation valve; 16. Sixth manual isolation valve; 17. Seventh electric regulating valve; 18. Seventh manual isolation valve; 19. Eighth electric isolation valve; 20. Eighth manual isolation valve; 21. Ninth manual isolation valve; 22. Secondary heat exchanger; 23. Ninth electric isolation valve; 24. Tenth manual isolation valve; 25. Isolation valve; 26. Tenth electric isolation valve; 27. Eleventh manual isolation valve; 28. Twelfth manual isolation valve; 29. ​​Thirteenth manual isolation valve; 30. Fourteenth manual isolation valve; 31. Twelfth electric regulating valve; 32. Fifteenth manual isolation valve; 33. Shaft seal cooler; 34. Fine treatment system; 35. Condensate pump; 36. Condenser; 37. Heat network drain header; 38. First heat network heater; 39. Second heat network heater; 40. First drain pump; 41. Second drain pump; 42. Fourth low-pressure heater; 43. Third low-pressure heater; 44. Second low-pressure heater; 45. First low-pressure heater; 46. Online water quality monitoring instrument; 47. Deaerator recovery system. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown 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 the present invention, and should not be construed as limiting the present invention.

[0020] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly 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; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] The following is for reference. Figure 1 and Figure 2 A cogeneration unit heat network condensate recovery system based on cascade heat exchange is described according to an embodiment of the present invention.

[0023] like Figure 1 and Figure 2As shown, the cogeneration unit heat network condensate recovery system based on cascade heat exchange according to an embodiment of the present invention includes a primary heat exchange subsystem and a secondary heat exchange subsystem. The primary heat exchange subsystem includes: a heat network circulating water recovery pipeline 1, a primary heat exchanger 4, a heat network circulating water supply pipeline 8, a heat network heater, a condensate pump, and a heat network condensate header 37. The heat network circulating water recovery pipeline 1 is connected to the first inlet of the primary heat exchanger 4 through a first electric isolation valve 2 and a first manual isolation valve 3, and then connected to the heat network circulating water supply pipeline 8 through the first outlet of the primary heat exchanger 4. The heat network circulating water supply pipeline 8 is equipped with a first electric isolation valve 2 and a first manual isolation valve 3. Two electric isolation valves 6 and a third manual isolation valve 7 are provided. The heating network heater is connected to the heating network drain header 37 via a drain pump. The upstream side of the heating network drain header 37 is connected to the second inlet of the first-stage heat exchanger 4 via a first branch, and then connected to the downstream side of the heating network drain header 37 via the second outlet and the second branch of the first-stage heat exchanger 4. The first branch is equipped with a third electric isolation valve 9 and a fourth manual isolation valve 10, and the second branch is equipped with a fourth electric isolation valve 11 and a fifth manual isolation valve 12. A fifth manual isolation valve 12 is provided between the upstream side and the downstream side of the heating network drain header 37.

[0024] The secondary heat exchange subsystem includes: a flow orifice plate 14, a secondary heat exchanger 22, a condenser 36, a condensate pump 35, a fine treatment system 34, and a shaft seal cooler 33. The third inlet of the secondary heat exchanger 22 is connected to the heat network drain header 37 through the flow orifice plate 14. A first valve group is installed between the secondary heat exchanger 22 and the flow orifice plate 14. The heat network drain entering the secondary heat exchanger 22 from the third inlet is suitable for passing through the third outlet of the secondary heat exchanger 22 sequentially through the condenser 36, the condensate pump 35, the fine treatment system 34, and the shaft seal cooler 33. One path of the shaft seal cooler 33 is connected to the feedwater system, and the other path enters the secondary heat exchanger 22 through the third branch and the fourth inlet of the secondary heat exchanger 22. Then, from the fourth outlet of the secondary heat exchanger 22, it enters the feedwater system through the fourth branch. The third branch is equipped with a second valve group, and the fourth branch is equipped with a third valve group.

[0025] In other words, the primary heat exchange subsystem can use the return water from the heating network as a cold source to cool the high-temperature condensate from the heating network for the first time. Specifically, the hot-side inlet (second inlet) of the primary heat exchanger 4 is connected to the condensate header 37 through the second branch, and the hot-side outlet (second outlet) is connected to the downstream pipeline of the condensate header 37 through the third branch. The cold-side inlet (first inlet) of the primary heat exchanger 4 is connected to the heating network circulating water recovery pipeline 1, and the cold-side outlet (first outlet) is connected to the heating network circulating water supply pipeline 8. Thus, the return water from the heating network, which has a direct temperature rise requirement, is used as a cold source to recover the high-grade heat of the condensate in the first stage, thereby improving the internal circulation energy efficiency of the heating process.

[0026] Furthermore, the high-temperature heat network condensate and the heat network return water exchange heat in the heat exchanger. For example, during the extremely cold period, the heat network return water temperature is 70℃, the heat network condensate temperature is 110℃, and the condensate pump 35 outlet temperature is 20℃-30℃. With the fifth electric isolation valve 13 closed, the high-temperature heat network condensate (60t / h, 110℃) from the heat network heater enters the primary heat exchanger 4 via the heat network condensate header 37, the third electric isolation valve 9, and the fourth manual isolation valve 10. After passing through the primary heat exchanger 4, the heat network condensate... The temperature drops to 80℃, while the 1000t / h of circulating water from the heating network circulating water recovery pipe 1 enters the first-stage heat exchanger 4 through the first electric isolation valve 2 and the first manual isolation valve 3 to perform primary cooling on the high-temperature heating network condensate. After heat exchange, the temperature of the circulating water rises to 88℃, and then it passes through the second electric isolation valve 6 and the third manual isolation valve 7 to the heating network circulating water supply pipe 8 for external heating. After primary cooling, the condensate returns to the heating network condensate header 37, and then enters the secondary heat exchange subsystem through the heating network condensate header 37.

[0027] The secondary heat exchange subsystem is located in the main plant building. It uses the low-temperature condensate after the shaft seal cooler 33 as the refrigerant to perform a second deep cooling of the heat network condensate after the primary heat exchange. Specifically, the heat network condensate header 37 delivers the heat network condensate to the secondary heat exchanger 22. The secondary heat exchanger 22 can be a plate and frame heat exchanger (because the maximum pressure of the condensate is 4.0 MPa), with a heat exchange area of ​​260 m2. After passing through the secondary heat exchanger 22, the temperature of the heat network condensate drops to 45°C. It is then delivered to the condenser 36 via the ninth electric isolation valve 23 and the tenth manual isolation valve 24. The internal pipes of the condenser 36 are equipped with atomizing nozzles to ensure heat exchange and deoxygenation effects.

[0028] In the above example, the third outlet of the secondary heat exchanger 22 is equipped with a ninth electrically operated isolation valve 23 and a tenth manually operated isolation valve 24. The first valve group includes a sixth electrically operated isolation valve 15, a sixth manually operated isolation valve 16, a seventh electrically operated regulating valve 17, and a seventh manually operated isolation valve 18. The second valve group includes a tenth electrically operated isolation valve 25 and an eleventh manually operated isolation valve 26. The third valve group includes an eleventh electrically operated isolation valve 27 and a twelfth manually operated isolation valve 28. The fourth valve group includes a thirteenth manually operated isolation valve 29, a fourteenth manually operated isolation valve 30, a twelfth electrically operated regulating valve 31, and a fifteenth manually operated isolation valve 32. The fifth valve group includes an eighth electrically operated isolation valve 19 and an eighth manually operated isolation valve 20. For the series and parallel arrangement of the valves, refer to... Figure 1 and Figure 2 This will not be elaborated upon here.

[0029] According to an embodiment of the present invention, the cogeneration unit heat network condensate recovery system based on cascade heat exchange utilizes the heat network return water with direct temperature rise requirements as a cold source to recover the first-stage high-grade heat of the heat network condensate, thereby improving the internal circulation energy efficiency of the heating process. The system uses the low-temperature condensate after the shaft seal cooler 33 as a refrigerant to perform secondary deep cooling on the heat network condensate after the first-stage heat exchange, thereby efficiently and cascade recovering the waste heat of the heat network condensate.

[0030] In some embodiments of the present invention, such as Figure 1 As shown, a second manual isolation valve 5 is installed between the first branch and the second branch.

[0031] In other words, when the primary heat exchanger 4 malfunctions or is under maintenance, the second manual isolation valve 5 can be opened, and the first electric isolation valve 2, the first manual isolation valve 3, the second electric isolation valve 6, and the third manual isolation valve 7 can be closed, so that the heat network drain does not pass through the primary heat exchanger 4.

[0032] In some embodiments of the present invention, such as Figure 1 As shown, the heating network heater includes a first heating network heater 38 and a second heating network heater 39, and the drain pump includes a first drain pump 40 and a second drain pump 41. The first heating network heater 38 and the second heating network heater 39 are connected in parallel upstream of the heating network drain header 37, and the first drain pump 40 is installed at the outlet of the first heating network heater 38, and the second drain pump 41 is installed at the outlet of the second heating network heater 39.

[0033] In other words, there can be multiple heating network heaters. When multiple heating network heaters are installed, they can be connected in parallel. Two of the multiple heating network heaters are the first heating network heater 38 and the second heating network heater 39. Each heating network heater can be equipped with a condensate pump.

[0034] In some embodiments of the present invention, such as Figure 2 As shown, the secondary heat exchange subsystem also includes an online water quality monitoring instrument 46, which is installed at the inlet of the condenser 36 to obtain water quality information of the heating network condensate. When the heating network condensate meets the reuse requirements, it is returned to the condenser 36; when the heating network condensate does not meet the reuse requirements, it is discharged directly.

[0035] In other words, by setting up an online water quality monitoring instrument 46, the quality of the condensate before final recycling can be monitored in real time. The final low-temperature condensate is sprayed into the condenser 36 through a dedicated interface equipped with an atomizing nozzle, and after being purified by the fine treatment system 34, it is reintegrated into the water supply system, which effectively reduces the possibility of deterioration of the water supply quality.

[0036] This invention recovers heat through a two-stage process of heat network return water and condensate. While ensuring system safety and avoiding feedwater pollution, it maximizes the recovery of waste heat from the heat network drainage, improves the unit's economy, and enables online water quality monitoring and fault bypass isolation, thereby enhancing operational flexibility.

[0037] In some embodiments of the present invention, such as Figure 2 As shown, the water supply system includes multiple low-pressure heaters connected in series. Among the multiple low-pressure heaters, the one closest to the shaft seal cooler 33 is the first low-pressure heater 45. The third branch is connected to the upstream of the first low-pressure heater 45, and the fourth branch is connected to the downstream of the first low-pressure heater 45. A fourth valve group is also provided at the inlet of the first low-pressure heater 45.

[0038] In other words, the condensate from the heating network can enter the secondary heat exchanger 22 through the third branch and then be heated without going through the first low-pressure heater 45. After passing through the fourth branch and merging with the outlet water of the first low-pressure heater 45, it is transported downstream. The fourth valve group adjusts the flow rate of condensate entering the secondary heat exchanger 22 according to the unit's operating conditions.

[0039] In some embodiments of the present invention, such as Figure 2 As shown, there are four low-pressure heaters: a first low-pressure heater 45, a second low-pressure heater 44, a third low-pressure heater 43, and a fourth low-pressure heater 42. The secondary heat exchange subsystem also includes a fifth branch, one end of which is connected to the upstream of the secondary heat exchanger 22, and the other end is connected between the third low-pressure heater 43 and the fourth low-pressure heater 42. A fifth valve group is provided on the fifth branch.

[0040] In other words, the cogeneration unit heat network condensate recovery system based on cascade heat exchange also includes a backup condensate path (i.e., the fifth branch). The backup condensate path is connected from the hot side inlet pipe of the secondary heat exchanger 22 to the inlet of the fourth low-pressure heater 42. The backup condensate path is equipped with an eighth electric isolation valve 19 and an eighth manual isolation valve 20 to switch the condensate recovery path when the secondary heat exchange subsystem is shut down.

[0041] Furthermore, when the secondary heat exchanger 22 malfunctions or is under maintenance, the eighth electric isolation valve 19 and the eighth manual isolation valve 20 are opened, and the heat network drain enters the inlet of the fourth low-pressure heater 42 through the eighth electric isolation valve 19 and the eighth manual isolation valve 20.

[0042] In some embodiments of the present invention, such as Figure 2As shown, the secondary heat exchange subsystem also includes a sixth branch, which is connected in parallel with the secondary heat exchanger 22. One end of the sixth branch is connected upstream of the third inlet of the secondary heat exchanger 22, and the other end is connected downstream of the third outlet of the secondary heat exchanger 22. The sixth branch can be equipped with a ninth manual isolation valve 21, which can divert the flow to the secondary heat exchanger 22 to ensure the heat exchange efficiency of the secondary heat exchanger 22.

[0043] In some embodiments of the present invention, multiple secondary heat exchange subsystems are provided, and the multiple secondary heat exchange subsystems are connected in parallel downstream of the heat network drainage header 37.

[0044] In other words, the number of secondary heat exchange subsystems can be set according to actual needs, thereby efficiently and in stages recovering waste heat from the heating network condensate. For example, different numbers of secondary heat exchange subsystems can be matched according to the flow rate of the heating network condensate, and this application does not impose any restrictions on this.

[0045] In some embodiments of the present invention, such as Figure 2 As shown, the cogeneration unit heat network condensate recovery system based on cascade heat exchange also includes a deaerator recovery system 47, which is connected in parallel with the secondary heat exchange subsystem downstream of the heat network condensate header 37.

[0046] In other words, when both the primary heat exchanger 4 and the secondary heat exchanger 22 are malfunctioning or under maintenance, the original method of recovering the condensate from the heating network can still be used to directly recover the condensate from the heating network to the deaerator of the unit, thereby ensuring the stable operation of the condensate recovery system of the cogeneration unit based on cascade heat exchange.

[0047] In some embodiments of the present invention, the primary heat exchange subsystem includes a plurality of primary heat exchangers 4, which are connected in series and / or in parallel.

[0048] In some embodiments of the present invention, the secondary heat exchange subsystem includes a plurality of secondary heat exchangers 22, which are connected in series and / or in parallel.

[0049] In some embodiments of the present invention, the online water quality monitoring instrument 46 is a conductivity meter, used to monitor the quality of hydrophobic water in real time to ensure that it meets the reuse standards.

[0050] In some embodiments of the present invention, the atomizing nozzle is disposed inside the condenser 36 to spray in the low-temperature hydrophobic atomized solution after two-stage heat exchange and monitoring, so as to ensure heat exchange and deoxygenation effects.

[0051] In some embodiments of the present invention, a hydrophobic pump may be provided as needed before the low-temperature hydrophobic recovery to the fine treatment system 34.

[0052] In some embodiments of the present invention, the primary heat exchanger 4 may be a plate type, welded plate type, or shell-and-tube type heat exchanger, and the secondary heat exchanger 22 may be a plate type, welded plate type, or shell-and-tube type heat exchanger.

[0053] The present invention relates to a combined heat and power (CHP) unit condensate recovery system based on cascade heat exchange. The primary heat exchange subsystem directly increases the return water temperature of the heat network, reducing the steam extraction consumption of the heat network heaters themselves. The secondary heat exchange subsystem heats the unit's condensate, reducing the steam extraction volume of the low-pressure regenerative system. This solution maximizes the recovery of high-grade heat energy while ensuring safety, comprehensively improving the unit's economic efficiency during the heating season.

[0054] Other components and operations of the cogeneration unit heat network condensate recovery system based on cascade heat exchange according to embodiments of the present invention are known to those skilled in the art and will not be described in detail here.

[0055] In the description of this specification, references to terms such as "some embodiments," "optionally," "furthermore," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0056] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A cogeneration unit heat network condensate recovery system based on cascade heat exchange, characterized in that, include: The primary heat exchange subsystem includes: a heating network circulating water recovery pipeline (1), a primary heat exchanger (4), a heating network circulating water supply pipeline (8), a heating network heater, a drain pump, and a heating network drain header (37). The heating network circulating water recovery pipeline (1) is connected to the first inlet of the first-stage heat exchanger (4) through the first electric isolation valve (2) and the first manual isolation valve (3), and then connected to the heating network circulating water supply pipeline (8) through the first outlet of the first-stage heat exchanger (4). The heating network circulating water supply pipeline (8) is equipped with a second electric isolation valve (6) and a third manual isolation valve (7). The heat network heater is connected to the heat network drain header (37) via the drain pump. The upstream side of the heat network drain header (37) is connected to the second inlet of the first-stage heat exchanger (4) via the first branch, and then connected to the downstream side of the heat network drain header (37) via the second outlet and the second branch of the first-stage heat exchanger (4). The first branch is equipped with a third electric isolation valve (9) and a fourth manual isolation valve (10), and the second branch is equipped with a fourth electric isolation valve (11) and a fifth manual isolation valve (12). The fifth manual isolation valve (12) is provided between the upstream side and the downstream side of the heat network drain header (37). A secondary heat exchange subsystem includes: a flow orifice plate (14), a secondary heat exchanger (22), a condenser (36), a condensate pump (35), a fine treatment system (34), and a shaft seal cooler (33). The third inlet of the secondary heat exchanger (22) is connected to the heat network drain header (37) through the flow orifice plate (14). A first valve group is provided between the secondary heat exchanger (22) and the flow orifice plate (14). The heat network drain entering the secondary heat exchanger (22) from the third inlet is adapted to pass through the second... The third outlet of the primary heat exchanger (22) passes sequentially through the condenser (36), the condensate pump (35), the fine treatment system (34), and the shaft seal cooler (33). One path of the shaft seal cooler (33) is connected to the feedwater system, and the other path enters the secondary heat exchanger (22) through the fourth inlet of the secondary heat exchanger (22) via the third branch. Then, from the fourth outlet of the secondary heat exchanger (22), it enters the feedwater system through the fourth branch. The third branch is equipped with a second valve group, and the fourth branch is equipped with a third valve group.

2. The cogeneration unit heat network condensate recovery system based on cascade heat exchange according to claim 1, characterized in that, A second manual isolation valve (5) is installed between the first branch and the second branch.

3. The cogeneration unit heat network condensate recovery system based on cascade heat exchange according to claim 1, characterized in that, The heating network heater includes a first heating network heater (38) and a second heating network heater (39), and the drain pump includes a first drain pump (40) and a second drain pump (41). The first heating network heater (38) and the second heating network heater (39) are connected in parallel upstream of the heating network drain header (37), and the first drain pump (40) is installed at the outlet of the first heating network heater (38), and the second drain pump (41) is installed at the outlet of the second heating network heater (39).

4. The cogeneration unit heat network condensate recovery system based on cascade heat exchange according to claim 1, characterized in that, The secondary heat exchange subsystem further includes an online water quality monitoring instrument (46), which is installed at the inlet of the condenser (36) to obtain water quality information of the heat network condensate. When the heat network condensate meets the reuse requirements, the heat network condensate is returned to the condenser (36); When the drainage of the heating network does not meet the reuse requirements, it is discharged directly.

5. The cogeneration unit heat network condensate recovery system based on cascade heat exchange according to claim 1, characterized in that, The water supply system includes: multiple low-pressure heaters connected in series, the low-pressure heater closest to the shaft seal cooler (33) being the first low-pressure heater (45), the third branch being connected upstream of the first low-pressure heater (45), the fourth branch being connected downstream of the first low-pressure heater (45), and the inlet of the first low-pressure heater (45) being provided with a fourth valve group.

6. The cogeneration unit heat network condensate recovery system based on cascade heat exchange according to claim 5, characterized in that, The low-pressure heaters are provided in four parts, namely the first low-pressure heater (45), the second low-pressure heater (44), the third low-pressure heater (43), and the fourth low-pressure heater (42). The secondary heat exchange subsystem also includes a fifth branch, one end of which is connected to the upstream of the secondary heat exchanger (22), and the other end is connected between the third low-pressure heater (43) and the fourth low-pressure heater (42). A fifth valve group is provided on the fifth branch.

7. The cogeneration unit heat network condensate recovery system based on cascade heat exchange according to claim 1, characterized in that, The secondary heat exchange subsystem further includes a sixth branch, which is connected in parallel with the secondary heat exchanger (22), with one end connected to the upstream of the third inlet of the secondary heat exchanger (22) and the other end connected to the downstream of the third outlet of the secondary heat exchanger (22).

8. The cogeneration unit heat network condensate recovery system based on cascade heat exchange according to any one of claims 1-7, characterized in that, Multiple secondary heat exchange subsystems are provided, and multiple secondary heat exchange subsystems are connected in parallel downstream of the heat network drainage header (37).

9. The cogeneration unit heat network condensate recovery system based on cascade heat exchange according to claim 1, characterized in that, It also includes a deaerator recovery system (47), which is connected in parallel with the secondary heat exchange subsystem downstream of the heat network drain header (37).

10. The cogeneration unit heat network condensate recovery system based on cascade heat exchange according to claim 1, characterized in that, The primary heat exchange subsystem includes multiple primary heat exchangers (4), which are connected in parallel.

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