Waste heat recovery system based on double-cooling medium layered condenser and working method

Abstract

The application provides a waste heat recovery system based on a double-cooling medium layered condenser and a working method, which are reasonable in structure design, remarkable in waste heat recovery effect, reliable in operation and capable of reducing comprehensive energy consumption. The condensing steam turbine exhaust outlet is connected with the condenser; the whole plant cold circulating water main pipe is connected with the ventilation cooling tower outlet, and the whole plant hot circulating water main pipe is connected with the ventilation cooling tower inlet; the desalted water heat exchange pipe bundle is arranged in the upper layer space of the shell, and the circulating water heat exchange pipe bundle is arranged in the lower layer space of the shell; the desalted water heat exchange pipe bundle inlet is connected with the whole plant cold desalted water main pipe, and the desalted water heat exchange pipe bundle outlet is connected with the deaerator; the circulating water heat exchange pipe bundle inlet is connected with the whole plant cold circulating water main pipe, and the circulating water heat exchange pipe bundle outlet is connected with the whole plant hot circulating water main pipe; a standby cooling water inlet branch is connected between the desalted water inlet pipeline and the whole plant cold circulating water main pipe; and a standby cooling water outlet branch is connected between the desalted water outlet pipeline and the whole plant hot circulating water main pipe.

Description

Technical Field

[0001] This invention relates to the fields of waste heat recovery, energy cascade, energy conservation and emission reduction, and more specifically, to a waste heat recovery system and its working method based on a dual-cooling-medium stratified condenser. Background Technology

[0002] During the operation of thermal power units, a large amount of exhaust steam discharged from the low-pressure cylinder of the condensing steam turbine needs to be cooled into saturated water at the same pressure level in the condenser. Currently, conventional condensers all use a single cooling medium (circulating water) for cooling. The cold circulating water plays a role in maintaining the vacuum of the condenser on the one hand, and absorbs a large amount of heat released by the exhaust steam on the other hand. After the cold circulating water is heated to hot circulating water, it enters the ventilation cooling tower and finally releases the heat to the atmosphere. After the hot circulating water releases heat, it is pressurized by the circulating water pump and sent back to the condenser. This is an open heat circulation system. The heat absorbed by the cold circulating water cannot be reused, resulting in cold end loss and a large waste of waste heat.

[0003] In combined heat and power (CHP) projects, because the steam turbine supplies industrial steam, an equal amount of demineralized water needs to be added to the deaerator to ensure that the boiler has sufficient feedwater to produce main steam to return to the turbine for power generation. The demineralized water from the water treatment plant is generally at ambient temperature, approximately 20-30°C. To ensure effective deaeration, the ambient temperature demineralized water needs to be preheated to above 40°C before entering the deaerator. The conventional practice is to use high-grade steam with superheated temperatures, such as steam extracted from the turbine's final stage or steam from back pressure exhaust, for heating.

[0004] In addition, in petrochemical bases and cold regions, hot demineralized water is also used for process water replenishment, equipment flushing, heat pump heat source, heating and heat tracing, etc., and the temperature generally needs to be above 40℃.

[0005] Existing technologies have significant limitations in the design of waste heat recovery systems to address the cold-end losses caused by the heat release of exhaust steam in the condenser of condensing steam turbines. (See attached...) Figure 1 As shown, in the traditional operation of a condenser system, fresh steam from the outside enters the condensing turbine 2 through the main steam pipe 3, expands, and performs work. The pressure and temperature of the fresh steam drop significantly, becoming exhaust steam, which enters the condenser 1 through the exhaust steam pipe 4. The exhaust steam enters the condenser shell-side space 6 through the condenser throat 5, is cooled by the heat exchange tube bundle 7, and becomes saturated water that enters the condenser hot well 8.

[0006] The circulating water inlet pipe 9 connects to the plant's cold circulating water header 12 and the inlet of the heat exchange tube bundle 7, respectively. The circulating water outlet pipe 10 connects to the plant's hot circulating water header 13 and the outlet of the heat exchange tube bundle 7, respectively. The cold circulating water from the ventilation cooling tower 11 enters the heat exchange tube bundle 7 of the condenser 1 through the plant's cold circulating water header 12 and the circulating water inlet pipe 9, absorbs the heat from the exhaust steam, and becomes hot circulating water. The hot circulating water returns to the ventilation cooling tower 11 through the circulating water outlet pipe 10 and the plant's hot circulating water header 13, and finally releases the absorbed heat from the exhaust steam into the atmosphere, forming an open heat circulation system.

[0007] A shut-off valve 18 is installed on the circulating water inlet pipe 9 and the circulating water outlet pipe 10 to isolate the condenser from the outside world.

[0008] A circulating water pump is installed on the cold circulating water header 12 of the whole plant to increase the pressure of the cold circulating water in order to compensate for the pressure loss of circulating water in various heat exchange equipment, pipelines and ventilation cooling towers.

[0009] After the exhaust steam is cooled into saturated water, it collects in the condenser hot well 8, enters the condensate pump 15 through the condensate pump inlet pipe 14 to increase the pressure, and then is transported to the deaerator 17 through the condensate pump outlet pipe 16 to rejoin the thermodynamic cycle.

[0010] When the condensing steam turbine 2 is in heating and power generation mode, the industrial extraction port of the turbine will supply heating steam to the outside through the extraction steam pipe 24. Since some steam is extracted from the middle section of the turbine, the steam flow rate in the exhaust steam pipe 4 will be less than the steam flow rate in the main steam pipe 3. This means that the condensate flow rate returning to the deaerator 17 will be less than the steam flow rate in the main steam pipe 3. To ensure that the new steam produced from the boiler in the next steam cycle reaches the steam flow rate of the main steam pipe 3, additional demineralized water needs to be supplied to the deaerator 17 through the deaerator makeup water pipe 26. The demineralized water is preheated with steam extracted and exhausted from the turbine to ensure efficient deoxygenation in the deaerator 17, and the oxygen content of the effluent meets the boiler's feedwater requirements. The demineralized water makeup water flow rate is approximately equal to the flow rate of heating steam supplied to the outside through the extraction steam pipe 24.

[0011] The aforementioned traditional systems suffer from significant cold-end losses and unrecovered waste heat.

[0012] For example, patent CN 221823891 U discloses a system for recovering the heat of exhaust steam from a condensing steam turbine. Although it recovers some of the heat from the exhaust steam, its technical solution has the following drawbacks: First, the system does not fully consider the pressure requirements of the low-pressure heater for heating steam. That is, the steam pressure determines the upper limit of the outlet water temperature of the surface heat exchanger, while the exhaust steam saturation pressure corresponds to the condensate saturation temperature, and its heating capacity is limited. Essentially, the system still heats the condensate through medium-pressure superheated steam, so the available exhaust steam flow is not large, and the amount of waste heat recovered is limited. Second, this solution requires the consumption of high-grade medium-pressure steam, which reduces the power generation of the steam turbine. Furthermore, the back pressure of a condensing steam turbine is determined by the cooling water temperature. Removing a small amount of exhaust steam cannot significantly reduce the back pressure, and has limited effect on improving the overall power capacity of the steam turbine.

[0013] On the other hand, patent CN 222257782 U discloses a combined condenser for recovering the heat of exhaust steam from a condensing steam turbine. While this uses a mixed condenser instead of a low-pressure heater to some extent, it still has the following shortcomings: First, in traditional systems with multiple low-pressure heaters connected in series, multi-stage steam with increasing pressure is used to heat the condensate. However, with a single mixed condenser, only the highest-level steam can be used to ensure the outlet water temperature, violating the concept of cascaded energy utilization. Second, using the condensate from the surface condenser outlet after pressurization as cooling water for the mixed condenser reduces the condensate pressure, requiring a new pump for pressurization, increasing both equipment investment and plant power consumption. Third, the outlet water temperature of the mixed heat exchanger is also limited by the steam pressure, resulting in a limited usable exhaust steam flow and a still limited amount of waste heat recovery.

[0014] In summary, existing technologies exhibit significant gaps in the recovery of waste heat from condensing steam turbines. Specifically, these gaps manifest in the inability to fully recover substantial volumes of waste heat, and the requirement for existing recovery technologies to consume additional high-grade steam or electricity. These technological bottlenecks limit the improvement of overall thermal efficiency.

[0015] Existing technologies have a need to improve the efficiency of waste heat recovery from condensing steam turbines, while power plant demineralized water requires preheating. Preheating demineralized water using waste steam, replacing traditional heating methods that consume high-grade steam, is a feasible energy cascade utilization solution. Therefore, designing a system for recovering waste heat from condensing steam turbines using demineralized water has significant innovative value, providing an upgrade direction for green development and improving overall thermal efficiency and economic viability. Summary of the Invention

[0016] The purpose of this invention is to overcome the above-mentioned shortcomings in the existing technology. Combining the energy structure of power plants and the multiple needs of condensing steam turbine vacuum maintenance, demineralized water preheating, and waste heat recovery, this invention utilizes the natural temperature gradient of the exhaust steam flowing through the condenser to provide a waste heat recovery system and operating method based on a dual-cooling-medium stratified condenser with reasonable structural design, significant waste heat recovery effect, and reliable operation, thereby achieving the goal of reducing overall energy consumption.

[0017] The technical solution adopted by this invention to solve the above problems is: a waste heat recovery system based on a dual-cooling-medium stratified condenser, including a condenser, a condensing steam turbine, a plant-wide cold demineralized water header, a plant-wide cold circulating water header, a plant-wide hot circulating water header, a deaerator, and a ventilation cooling tower; the exhaust steam outlet of the condensing steam turbine is connected to the condenser via an exhaust steam pipe; a cooling water heat exchange tube bundle is installed inside the condenser shell; the plant-wide cold circulating water header is connected to the outlet of the ventilation cooling tower, and the plant-wide hot circulating water header is connected to the inlet of the ventilation cooling tower; the space inside the condenser shell is divided into an upper shell space and a lower shell space; the cooling water heat exchange tube bundle includes a demineralized water heat exchange tube bundle and a circulating water heat exchange tube bundle, which are arranged in layers from top to bottom. In the upper space of the shell, the circulating water heat exchange tube bundle is arranged in the lower space of the shell; the inlet of the demineralized water heat exchange tube bundle is connected to the plant's cold demineralized water main pipe through the demineralized water inlet pipe, and a relevant shut-off valve is installed on the demineralized water inlet pipe; the outlet of the demineralized water heat exchange tube bundle is connected to the deaerator; the inlet of the circulating water heat exchange tube bundle is connected to the plant's cold circulating water main pipe through the circulating water inlet pipe, and a relevant shut-off valve is installed on the circulating water inlet pipe; the outlet of the circulating water heat exchange tube bundle is connected to the plant's hot circulating water main pipe; a backup cooling water inlet branch is connected between the demineralized water inlet pipe and the plant's cold circulating water main pipe, and a relevant shut-off valve is installed on the backup cooling water inlet branch; a backup cooling water outlet branch is connected between the demineralized water outlet pipe and the plant's hot circulating water main pipe, and a relevant shut-off valve is installed on the backup cooling water outlet branch.

[0018] The present invention provides a shell-side flow guiding device inside the condenser shell. After the exhaust steam enters the condenser through the throat, it is guided by the shell-side flow guiding device to flow evenly from top to bottom through the upper and lower shell spaces, thereby flowing sequentially over the outer surfaces of the demineralized water heat exchange tube bundle and the circulating water heat exchange tube bundle.

[0019] The outlet of the demineralized water heat exchange tube bundle described in this invention is connected to the deaerator makeup water pipe through the demineralized water outlet pipe, and the deaerator makeup water pipe is connected to the deaerator. Relevant shut-off valves, regulating valves and flow measurement devices are installed on the demineralized water outlet pipe.

[0020] The outlet of the circulating water heat exchange tube bundle described in this invention is connected to the main hot circulating water pipe of the entire plant through a circulating water outlet pipe. The circulating water outlet pipe is equipped with shut-off valves, regulating valves and flow measurement devices.

[0021] The condenser described in this invention has a condenser hot well at the bottom, which is connected to the inlet of the condensate pump through a condensate pump inlet pipe, and the outlet of the condensate pump is connected to the deaerator through a condensate pump outlet pipe.

[0022] The invention also includes a main steam pipeline, which is connected to the main steam inlet of the condensing steam turbine.

[0023] The invention also includes a steam extraction pipe, wherein the industrial steam extraction port of the condensing steam turbine is connected to the steam extraction pipe, and a flow measurement device is installed on the steam extraction pipe.

[0024] A method for operating a waste heat recovery system based on a dual-cooling-medium stratified condenser includes the following steps: (1) Fresh steam from the outside enters the condensing steam turbine and expands to do work. The pressure and temperature of the fresh steam drop significantly and become exhaust steam, which enters the condenser. At the same time, the industrial steam extraction port of the condensing steam turbine delivers heating steam to the outside, and the condensing steam turbine is in the heating and power generation mode. (2) The ambient temperature demineralized water from the cold demineralized water header of the whole plant passes through the demineralized water heat exchange tube bundle, contacts the high temperature exhaust steam in the upper space of the shell, absorbs the heat released by the high temperature exhaust steam, and the heated demineralized water enters the deaerator. (3) The ambient temperature circulating water from the cold circulating water header of the whole plant passes through the circulating water heat exchange tube bundle, contacts the low temperature exhaust steam in the lower space of the shell, absorbs the heat released by the low temperature exhaust steam, and the heated hot circulating water returns to the ventilation cooling tower through the hot circulating water header of the whole plant. (4) After the exhaust steam is cooled into saturated water, it is collected in the condenser hot well. The saturated water is then pumped to the deaerator to rejoin the thermodynamic cycle after the pressure is increased by the condensate pump. (5) When the condensing steam turbine is running in pure condensing condition, the industrial extraction port of the condensing steam turbine does not supply heating steam to the outside. When the industrial extraction steam flow of the condensing steam turbine is detected to be zero, the interlocking operation is performed: the shut-off valves of the standby cooling water inlet branch and the standby cooling water outlet branch are opened, the circulating water flows through the demineralized water heat exchange tube bundle, ensuring that the exhaust steam of the steam turbine can be fully cooled when it passes through the upper space of the shell, and the shut-off valves on the demineralized water inlet pipe and the demineralized water outlet pipe are closed simultaneously. (6) When the condensing steam turbine is in the heating and power generation mode, the condenser operates in the dual cooling medium mode. Demineralized water flows through the demineralized water heat exchange tube bundle, and circulating water flows through the circulating water heat exchange tube bundle. The demineralized water and circulating water jointly undertake the task of cooling the exhaust steam. (7) When the condensing steam turbine is in pure condensing power generation mode, the condenser operates in single cooling medium mode. Both the demineralized water heat exchange tube bundle and the circulating water heat exchange tube bundle are filled with circulating water, and only the circulating water undertakes the task of cooling the exhaust steam.

[0025] (8) During system operation, real-time monitoring of data such as cooling water flow rate, temperature and condenser back pressure is performed, and the opening of regulating valve is dynamically adjusted to control the cooling water flow rate, so as to achieve stable unit operation and waste heat recovery.

[0026] Compared with existing technologies, this patent demonstrates significant advantages in waste heat recovery, energy conservation and emission reduction, environmental protection, and structural design, as detailed below: (1) Significant waste heat recovery effect. This system utilizes the natural temperature gradient of the turbine exhaust steam from top to bottom, arranging the demineralized water heat exchange tube bundle in the upper high-temperature exhaust steam area and the circulating water heat exchange tube bundle in the lower low-temperature exhaust steam area. With the inlet temperature of the two cooling media being the same, by rationally allocating the number of the two heat exchange tube bundles, the exhaust steam can be cooled by the demineralized water heat exchange tube bundle as much as possible. The outlet water temperature of the demineralized water heat exchange tube bundle is higher than that of the circulating water outlet water temperature of conventional units, thus recovering as much and as effective waste heat as possible from the exhaust steam and reducing the cold end heat loss of the condenser. The outlet water temperature of the circulating water heat exchange tube bundle is lower than or close to that of the circulating water outlet water temperature of conventional units, thereby ensuring that the condenser vacuum degree is maintained within the normal range.

[0027] (2) Significant Energy Saving, Consumption Reduction, and Environmental Protection Effects. This system utilizes demineralized water to recover and reuse the waste heat from the turbine exhaust steam. On the one hand, this reduces the steam consumption for heating cold demineralized water in conventional power plants, thus lowering coal consumption. On the other hand, the demineralized water system is a closed system, allowing its heat to be rationally absorbed and preventing waste from being released into the atmosphere. By reducing the unit's coal consumption, emissions of pollutants such as carbon dioxide and sulfur dioxide are reduced. Simultaneously, the system avoids the direct release of heat carried by circulating water into the atmosphere, reducing thermal pollution. It aligns with national energy conservation, emission reduction, and "dual carbon" goals, demonstrating significant environmental benefits and promotional value.

[0028] (3) The system has a reasonable structural design and a wide range of applications. The system adopts a single-shell, dual-cooling-medium condenser. Two independent heat exchange tube bundles are arranged in layers within the single shell, which can realize the independent operation of the two cooling media without interference and avoid cross-contamination. It can be used for the design of new power plants as well as for the upgrading and renovation of old power plants. By calculating the cooling water balance and heat exchange balance and adjusting the heat exchange area ratio of the two heat exchange tube bundles, it can be adapted to different operating requirements. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of an existing condenser system; Figure 2 This is a system schematic diagram according to an embodiment of the present invention; Figure 3 This is a flowchart illustrating the working method of an embodiment of the present invention.

[0030] Figure 4 This is a flowchart of the condensing steam turbine entering the heating and power generation mode according to an embodiment of the present invention.

[0031] Figure 5 This is a flowchart of the condensing steam turbine entering the pure condensing power generation mode according to an embodiment of the present invention. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0033] As attached Figure 2 As shown, a waste heat recovery system based on a dual-cooling-medium stratified condenser includes the following structure: The main steam pipe 3 is connected to the main steam inlet of the condensing steam turbine 2. The exhaust steam outlet of the condensing steam turbine 2 is connected to the condenser 1A through the exhaust steam pipe 4. The industrial steam extraction port is connected to the extraction steam pipe 24. A flow measurement device 25 is installed on the extraction steam pipe 24.

[0034] The internal space of the condenser 1A shell is divided into an upper shell space 6A and a lower shell space 6B.

[0035] The condenser 1A shell is equipped with a cooling water heat exchange tube bundle, which includes a demineralized water heat exchange tube bundle 7A and a circulating water heat exchange tube bundle 7B. The demineralized water heat exchange tube bundle 7A and the circulating water heat exchange tube bundle 7B are arranged in layers from top to bottom. The demineralized water heat exchange tube bundle 7A is arranged in the upper space 6A of the shell (close to the condenser throat, i.e. the exhaust steam inlet diffuser section, mainly in contact with high-temperature exhaust steam), and the circulating water heat exchange tube bundle 7B is arranged in the lower space 6B of the shell (close to the condenser hot well, in contact with low-temperature exhaust steam).

[0036] A shell-side flow guide device 20 is installed inside the condenser shell. After the exhaust steam enters the condenser through the condenser throat 5, it is guided by the shell-side flow guide device 20 to flow evenly from top to bottom through the upper shell space 6A and the lower shell space 6B, thereby flowing sequentially over the outer surfaces of the demineralized water heat exchange tube bundle 7A and the circulating water heat exchange tube bundle 7B. During the flow process, the exhaust steam continuously releases heat and cools and condenses, forming a natural temperature field with a gradually decreasing temperature from top to bottom, that is, the exhaust steam temperature in the upper region is higher than that in the lower region.

[0037] The inlet of the demineralized water heat exchanger tube bundle 7A is connected to the plant's cold demineralized water main pipe 23 via the demineralized water inlet pipe 21. The outlet of the demineralized water heat exchanger tube bundle 7A is connected to the deaerator makeup water pipe 26 via the demineralized water outlet pipe 22. The deaerator makeup water pipe 26 is connected to the deaerator 17.

[0038] The inlet of the circulating water heat exchanger tube bundle 7B is connected to the cold circulating water header 12 of the whole plant through the circulating water inlet pipe 9, and the outlet of the circulating water heat exchanger tube bundle 7B is connected to the hot circulating water header 13 of the whole plant through the circulating water outlet pipe 10; the cold circulating water header 12 of the whole plant is connected to the outlet of the ventilation cooling tower 11, and the hot circulating water header 13 of the whole plant is connected to the inlet of the ventilation cooling tower 11.

[0039] A regulating valve 19 is installed on the demineralized water outlet pipe 22 and the circulating water outlet pipe 10, respectively. A flow measuring device 25 is installed on the demineralized water outlet pipe 22 and the circulating water outlet pipe 10, respectively, to determine the current flow rate of water passing through the condenser 1A, and to assist the regulating valve 19 in control. A shut-off valve 18 is installed on the demineralized water inlet pipe 21, the demineralized water outlet pipe 22, the circulating water inlet pipe 9, and the circulating water outlet pipe 10, as a barrier between the condenser and the outside environment.

[0040] A condenser hot well 8 is provided at the bottom of the condenser 1A. The condenser hot well 8 is connected to the inlet of the condensate pump 15 through the condensate pump inlet pipe 14. The outlet of the condensate pump 15 is connected to the deaerator 17 through the condensate pump outlet pipe 16.

[0041] A backup cooling water inlet branch line 27 is connected between the demineralized water inlet pipe 21 and the plant's cold circulating water main pipe 12 as a connecting pipe, and a backup cooling water outlet branch line 28 is connected between the demineralized water outlet pipe 22 and the plant's hot circulating water main pipe 13 as a connecting pipe. Both the backup cooling water inlet branch line 27 and the backup cooling water outlet branch line 28 are equipped with relevant shut-off valves 18.

[0042] A hot demineralized water branch line 29 is connected to the demineralized water outlet pipe 22, which can be used as a hot water source for specific projects (such as process water, heating and heat tracing). A shut-off valve 18 is installed on the hot demineralized water branch line 29. When the condensing steam turbine 2 is in heating and power generation mode, the shut-off valve 18 on the hot demineralized water branch line 29 can be opened as needed. After the demineralized water absorbs the heat of the exhaust steam, in addition to mainly entering the deaerator through the deaerator makeup water pipe 26, some of the hot demineralized water can be led to process water and other water use points to realize the multi-path utilization of waste heat.

[0043] In this embodiment, the shut-off valve 18 is a gate valve.

[0044] As attached Figure 3 As shown, a working method for a waste heat recovery system based on a dual-cooling-medium stratified condenser includes the following specific implementation steps: (1) Fresh steam from the outside enters the condensing steam turbine 2 through the main steam pipe 3 and expands to do work. The pressure and temperature of the fresh steam drop significantly and become exhaust steam. The exhaust steam enters the condenser 1A through the exhaust steam pipe 4. At the same time, the industrial steam extraction port of the condensing steam turbine 2 delivers heating steam to the outside through the extraction steam pipe 24. The condensing steam turbine 2 is in the heating and power generation mode.

[0045] (2) Ambient temperature demineralized water from the plant's cold demineralized water header 23 (inlet temperature t) in除盐水 The heat is transferred through the demineralized water heat exchange tube bundle 7A to the high-temperature exhaust steam in the upper space 6A of the shell. After absorbing the heat released by the high-temperature exhaust steam, the temperature rises to t. out除盐水 The heated demineralized water enters the deaerator 17 through the deaerator water supply pipe 26. The absorbed heat is not discharged into the atmosphere and is not wasted, thus realizing waste heat recovery and saving the steam extracted and discharged from the turbine that was originally used to preheat the cold demineralized water.

[0046] (3) Ambient temperature circulating water from the plant's cold circulating water header 12 (inlet temperature t) in循环水 The circulating water heat exchange tube bundle 7B contacts the low-temperature exhaust steam in the lower space 6B of the shell, absorbing the heat released by the low-temperature exhaust steam and raising the temperature to t. out循环水 The heated circulating water returns to the ventilation cooling tower 11 through the circulating water outlet pipe 10 and the whole plant's hot circulating water header 13, and finally releases the absorbed exhaust steam heat into the atmosphere.

[0047] Where t in除盐水 =t in循环水 , t out除盐水 >t out循环水 , t out除盐水 It meets the requirements for thermal deoxygenation.

[0048] Since the upper exhaust steam temperature is higher than the lower exhaust steam temperature, and the heat exchange areas and cooling medium flow rates of the two sets of tube bundles are matched, this provides a prerequisite for the demineralized water outlet temperature to be consistently higher than the circulating water outlet temperature. Secondly, regulating valves 19 are installed on the demineralized water outlet pipe 22 and the circulating water outlet pipe 10, respectively. During system operation, the inlet and outlet temperatures and flow rates of the demineralized water and circulating water, as well as the condenser back pressure, are monitored in real time. Based on the monitoring data, the opening of the regulating valves is dynamically adjusted to regulate the flow rates of the two cooling media. While ensuring that the condenser back pressure is maintained within the set range, the actual amount of water flowing through the demineralized water heat exchange tube bundle 7A and the circulating water heat exchange tube bundle 7B is controlled, ultimately achieving the desired temperature. out除盐水 Higher than t out循环水 This allows the heat from the exhaust steam to be released as much as possible into the recyclable demineralized water medium, achieving the dual goals of waste heat recovery and vacuum maintenance.

[0049] (4) After the exhaust steam is cooled into saturated water, it is collected in the condenser hot well 8, enters the condensate pump 15 through the condensate pump inlet pipe 14 to increase the pressure, and then is transported to the deaerator 17 through the condensate pump outlet pipe 16 to rejoin the thermodynamic cycle.

[0050] (5) When the condensing steam turbine 2 is operating under pure condensing conditions, the industrial extraction steam port of the steam turbine does not deliver heating steam to the outside through the extraction steam pipe 24. At this time, it is not necessary to add demineralized water to the deaerator 17 through the deaerator makeup water pipe 26, but there must be enough cooling water entering the condenser 1A to cool the exhaust steam of the steam turbine. When the system detects that the industrial extraction steam flow of the steam turbine is zero, the interlocking operation is performed: the shut-off valves 18 of the standby cooling water inlet branch 27 and the standby cooling water outlet branch 28 are opened, and the circulating water flows through the demineralized water heat exchange tube bundle 7A to ensure that the exhaust steam of the steam turbine can be fully cooled when it passes through the upper space 6A of the cooling shell; the shut-off valves 18 on the demineralized water inlet pipe 21 and the demineralized water outlet pipe 22 are closed simultaneously to cut off the demineralized water side passage and prevent the circulating water from entering the demineralized water system.

[0051] (6) When the condensing steam turbine 2 is in the heating and power generation mode, the condenser 1A operates in the dual cooling medium mode. Demineralized water flows through the demineralized water heat exchange tube bundle 7A and circulating water flows through the circulating water heat exchange tube bundle 7B. The demineralized water and circulating water jointly undertake the task of cooling the exhaust steam.

[0052] (7) When the condensing steam turbine 2 is in pure condensing power generation mode, the condenser 1A operates in single cooling medium mode. Both the demineralized water heat exchange tube bundle 7A and the circulating water heat exchange tube bundle 7B are filled with circulating water, and only the circulating water undertakes the task of cooling the exhaust steam.

[0053] When the condensing steam turbine 2 is in pure condensing power generation mode, the shut-off valve 18 on the hot demineralized water branch 29 should be in the closed state.

[0054] It should be noted that the specific embodiments described in this specification are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various modifications, additions, or equivalent substitutions to the above embodiments, but all such changes should fall within the scope derived from the inventive concept. The scope of protection of this invention is determined by the claims; any equivalent changes or modifications made based on the spirit and essence of this invention should be covered within the scope of protection of this invention.

Claims

1. A waste heat recovery system based on a dual-cooling-medium stratified condenser, comprising a condenser, a condensing steam turbine, a plant-wide cold demineralized water header, a plant-wide cold circulating water header, a plant-wide hot circulating water header, a deaerator, and a draft cooling tower; the exhaust steam outlet of the condensing steam turbine is connected to the condenser via an exhaust steam pipeline; a cooling water heat exchange tube bundle is installed inside the condenser shell; the plant-wide cold circulating water header is connected to the outlet of the draft cooling tower, and the plant-wide hot circulating water header is connected to the inlet of the draft cooling tower; characterized in that: The condenser shell is divided into an upper shell space and a lower shell space. The cooling water heat exchange tube bundle includes a demineralized water heat exchange tube bundle and a circulating water heat exchange tube bundle, which are arranged in layers from top to bottom. The demineralized water heat exchange tube bundle is located in the upper shell space, and the circulating water heat exchange tube bundle is located in the lower shell space. The inlet of the demineralized water heat exchange tube bundle is connected to the plant's main demineralized water supply pipe via a demineralized water inlet pipe. A shut-off valve is installed on the demineralized water inlet pipe. The outlet of the demineralized water heat exchange tube bundle is connected to... The system is connected to a deaerator; the inlet of the circulating water heat exchange tube bundle is connected to the plant's cold circulating water main pipe via a circulating water inlet pipe, and a shut-off valve is installed on the circulating water inlet pipe; the outlet of the circulating water heat exchange tube bundle is connected to the plant's hot circulating water main pipe; a backup cooling water inlet branch is connected between the demineralized water inlet pipe and the plant's cold circulating water main pipe, and a shut-off valve is installed on the backup cooling water inlet branch; a backup cooling water outlet branch is connected between the demineralized water outlet pipe and the plant's hot circulating water main pipe, and a shut-off valve is installed on the backup cooling water outlet branch.

2. The waste heat recovery system based on a dual-cooling-medium stratified condenser according to claim 1, characterized in that: Inside the condenser shell, there is a shell-side flow guiding device. After the exhaust steam enters the condenser through the throat, it is guided by the shell-side flow guiding device to flow evenly from top to bottom through the upper and lower shell spaces, and then flows sequentially over the outer surfaces of the demineralized water heat exchange tube bundle and the circulating water heat exchange tube bundle.

3. The waste heat recovery system based on a dual-cooling-medium stratified condenser according to claim 1, characterized in that: The outlet of the demineralized water heat exchange tube bundle is connected to the deaerator makeup water pipe through the demineralized water outlet pipe, and the deaerator makeup water pipe is connected to the deaerator. Relevant shut-off valves, regulating valves and flow measurement devices are installed on the demineralized water outlet pipe.

4. The waste heat recovery system based on a dual-cooling-medium stratified condenser according to claim 1, characterized in that: The outlet of the circulating water heat exchange tube bundle is connected to the main hot circulating water pipe of the whole plant through the circulating water outlet pipe. The circulating water outlet pipe is equipped with shut-off valves, regulating valves and flow measurement devices.

5. The waste heat recovery system based on a dual-cooling-medium stratified condenser according to claim 1, characterized in that: The bottom of the condenser is provided with a condenser hot well, which is connected to the inlet of the condensate pump through a condensate pump inlet pipe. The outlet of the condensate pump is connected to the deaerator through a condensate pump outlet pipe.

6. The waste heat recovery system based on a dual-cooling-medium stratified condenser according to claim 1, characterized in that: It also includes the main steam pipeline, which is connected to the main steam inlet of the condensing steam turbine.

7. The waste heat recovery system based on a dual-cooling-medium stratified condenser according to claim 1, characterized in that: It also includes extraction steam pipes, where the industrial extraction port of the condensing steam turbine is connected to the extraction steam pipes, and flow measurement devices are installed on the extraction steam pipes.

8. A method for operating a waste heat recovery system based on a dual-cooling-medium stratified condenser as described in any one of claims 1-7, characterized in that: Including the following steps: (1) Fresh steam from the outside enters the condensing steam turbine and expands to do work. The pressure and temperature of the fresh steam drop significantly and become exhaust steam, which enters the condenser. At the same time, the industrial steam extraction port of the condensing steam turbine delivers heating steam to the outside, and the condensing steam turbine is in the heating and power generation mode. (2) The ambient temperature demineralized water from the cold demineralized water header of the whole plant passes through the demineralized water heat exchange tube bundle, contacts the high temperature exhaust steam in the upper space of the shell, absorbs the heat released by the high temperature exhaust steam, and the heated demineralized water enters the deaerator. (3) The ambient temperature circulating water from the cold circulating water header of the whole plant passes through the circulating water heat exchange tube bundle, contacts the low temperature exhaust steam in the lower space of the shell, absorbs the heat released by the low temperature exhaust steam, and the heated hot circulating water returns to the ventilation cooling tower through the hot circulating water header of the whole plant. (4) After the exhaust steam is cooled into saturated water, it is collected in the condenser hot well. After the saturated water is pressurized, it is transported to the deaerator to re-participate in the thermodynamic cycle. (5) When the condensing steam turbine is running in pure condensing condition, the industrial extraction port of the condensing steam turbine does not supply heating steam to the outside. When the industrial extraction steam flow of the condensing steam turbine is detected to be zero, the interlocking operation is performed: the shut-off valves of the standby cooling water inlet branch and the standby cooling water outlet branch are opened, the circulating water flows through the demineralized water heat exchange tube bundle, ensuring that the exhaust steam of the steam turbine can be fully cooled when it passes through the upper space of the shell, and the shut-off valves on the demineralized water inlet pipe and the demineralized water outlet pipe are closed simultaneously. (6) When the condensing steam turbine is in the heating and power generation mode, the condenser operates in the dual cooling medium mode. Demineralized water flows through the demineralized water heat exchange tube bundle, and circulating water flows through the circulating water heat exchange tube bundle. The demineralized water and circulating water jointly undertake the task of cooling the exhaust steam. (7) When the condensing steam turbine is in pure condensing power generation mode, the condenser operates in single cooling medium mode. Both the demineralized water heat exchange tube bundle and the circulating water heat exchange tube bundle are filled with circulating water, and only the circulating water undertakes the task of cooling the exhaust steam.

Images