A system and operation method for utilizing waste heat from circulating water of an indirect air-cooling unit

Abstract

A circulating water waste heat utilization system for an indirect air-cooling unit includes a steam turbine, a condenser, an ejector, a heat exchanger, and an air heater. The steam turbine exhaust port is connected to the hot-side inlet of the condenser, the steam extraction port of the steam turbine is connected to the steam-side inlet of the ejector, the circulating water branch at the cold-side outlet of the condenser is connected to the water-side inlet of the ejector, the ejector outlet is connected to the hot-side inlet of the heat exchanger, the hot-side outlet of the heat exchanger is connected to the hot-side inlet of the air heater, and the hot-side outlet of the air heater is connected to the circulating water branch at the cold-side inlet of the condenser. This indirect air-cooling unit circulating water waste heat utilization system uses high-temperature extraction steam to inject circulating water, heating it for external heating or cooling, and the waste heat is also recovered and utilized by the air heater. The system can effectively realize the recycling of circulating water heat, greatly improve the economic efficiency of the unit, achieve significant energy-saving benefits, and effectively avoid corrosion and blockage of the air preheater.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive energy utilization, and in particular relates to a circulating water waste heat utilization system for an indirect air-cooling unit. Background Art

[0002] Among all the losses in current generator sets, cooling loss accounts for the largest proportion. This heat is typically carried away by circulating water and released into the atmosphere. Recycling it would significantly improve the unit's economic efficiency. While this waste heat is substantial, it is difficult to recycle due to the low quality of the circulating water.

[0003] Due to the low design back pressure of water-cooled units, the low-pressure cylinder exhaust steam cannot be directly utilized. Currently, the main methods for waste heat utilization are absorption heat pump heating and high back pressure heating. However, high back pressure heating requires replacement of the turbine low-pressure cylinder rotor. Air-cooled units, on the other hand, have high design back pressure, and waste heat utilization is continuously increasing. However, existing waste heat utilization solutions for air-cooled units mainly use absorption heat pump heating for direct air-cooled units, resulting in complex systems and high modification costs. Waste heat utilization in indirect air-cooled units is less common, but there is significant potential for further utilization. Therefore, waste heat utilization solutions for indirect air-cooled units are still under development. Summary of the Invention

[0004] In response to the problems existing in the prior art, the purpose of the present invention is to provide a circulating water waste heat utilization system for an indirect air-cooling unit, in which the circulating water is heated by high-temperature steam extraction and then used for external heating or cooling, and the waste heat is also recovered and utilized by the heater.

[0005] The present invention is achieved through the following technical solutions:

[0006] A circulating water waste heat utilization system for an indirect air-cooling unit, comprising a steam turbine, a condenser, an ejector, a heat exchanger and an air heater;

[0007] The exhaust port of the steam turbine is connected to the hot side inlet of the condenser, the extraction port of the steam turbine is connected to the steam side inlet of the ejector, the circulating water branch of the cold side outlet of the condenser is connected to the water side inlet of the ejector, the outlet of the ejector is connected to the hot side inlet of the heat exchanger, the hot side outlet of the heat exchanger is connected to the hot side inlet of the heater, and the hot side outlet of the heater is connected to the circulating water branch of the cold side inlet of the condenser.

[0008] Preferably, a first control valve is provided between the steam extraction port of the steam turbine and the steam side inlet of the ejector.

[0009] Preferably, a second control valve is provided between the circulating water branch of the cold side outlet of the condenser and the water side inlet of the ejector.

[0010] Preferably, a cooling tower is further included, and the cold side of the condenser is connected to the cooling tower.

[0011] Preferably, an air preheater is further included, and the cold side outlet of the heater is connected to the cold side inlet of the air preheater.

[0012] Preferably, a low-temperature economizer is provided at the hot side outlet of the air preheater.

[0013] Preferably, the hot air side outlet of the air preheater is connected to the air side inlet of the boiler; the flue gas side inlet of the air preheater is connected to the flue gas outlet of the boiler.

[0014] Preferably, the high-temperature water of the heat exchanger is connected to a heat user.

[0015] Preferably, the cold side inlet of the heater is connected to a cold air source.

[0016] An operating method of an indirect air-cooling unit circulating water waste heat utilization system, comprising:

[0017] A stream of high-temperature steam is drawn from the steam turbine into the ejector, where it is mixed with the hot water from the circulating cooling water branch at the cold side outlet of the condenser and heated. The heated high-temperature water releases heat to the outside in the heat exchanger. The hot water that releases heat to the outside in the heat exchanger heats the cold air in the air heater. The air that absorbs heat is heated by the air preheater and then enters the boiler, while the cold water that releases heat is mixed with the circulating cooling water and then enters the condenser.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] The purpose of the present invention is to provide a system and operation method for utilizing the waste heat of circulating water in an indirect air-cooling unit. The system for utilizing the waste heat of circulating water in an indirect air-cooling unit uses high-temperature steam extraction to inject circulating water for heating and then uses it for external heating or cooling, and the waste heat is also recovered and utilized by a heater. The system can effectively realize the recovery and utilization of the heat of circulating water, greatly improve the economy of the unit, have greater energy-saving benefits, and effectively avoid corrosion and blockage of the air preheater.

[0020] Furthermore, the system of the present invention uses a heater and a low-temperature economizer in combination, which can, on the one hand, increase the inlet temperature of the air preheater and effectively avoid corrosion and blockage of the air preheater; on the other hand, it can improve the boiler combustion conditions, increase boiler efficiency and reduce turbine heat consumption, thereby achieving greater energy-saving benefits.

[0021] Furthermore, the system of the present invention uses an ejector to realize high-temperature steam extraction to heat circulating water. Compared with the method of utilizing the waste heat of circulating water through an absorption heat pump, the advantages of the system are simple structure, no moving parts, reliable operation and low modification cost.

[0022] Furthermore, the system described in the present invention is equipped with a first control valve in the steam extraction pipeline for adjusting the amount of steam extraction; a second control valve is installed in the circulating water branch for adjusting the flow rate of the induced circulating water; when the system is operated in winter, the circulating water temperature is low, and the first control valve can be adjusted up and the second control valve can be adjusted down to ensure that the hot water after the injection can meet the demand for external heating load when releasing heat in the heat exchanger; when the system is operated in summer, the high circulating water temperature will cause high back pressure of the turbine, thereby reducing the circulation efficiency, and the first control valve and the second control valve can be adjusted up to increase the circulating water flow rate of the condenser to reduce the circulation back pressure, while the hot water after the injection drives the absorption refrigeration in the heat exchanger to meet the summer cooling capacity demand. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a structural diagram of a circulating water waste heat utilization system for an indirect air-cooling unit.

[0024] In the figure: steam turbine 1, condenser 2, cooling tower 3, ejector 4, heat exchanger 5, air heater 6, air preheater 7, low-temperature economizer 8, first control valve 9, second control valve 10. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] The present invention will be described in further detail below with reference to the accompanying drawings.

[0028] like Figure 1The figure shows a schematic diagram of the structure of a circulating water waste heat utilization system for an indirect air-cooled unit. The system includes: a steam turbine 1, which expands and produces extraction steam; a condenser 2, which cools the turbine exhaust into condensate; a cooling tower 3, which dissipates the heat of the circulating water to the environment; an ejector 4, which heats the circulating water with high-temperature extraction steam; a heat exchanger 5, which transfers heat to heat users or serves as a heat source to drive absorption refrigeration; a heater 6, which heats the cold air entering the air preheater; an air preheater 7, which uses flue gas to heat the air entering the boiler; a low-temperature economizer 8, which uses flue gas to heat the feedwater; a first control valve 9, which regulates the extraction steam flow; and a second control valve 10, which regulates the flow rate of the ejected circulating water. The system uses an ejector to heat the circulating water with high-temperature extraction steam. Compared to methods that utilize circulating water waste heat through absorption heat pumps, the system has the advantages of a simple structure, no moving parts, reliable operation, and low modification costs.

[0029] like Figure 1 The figure shows a schematic diagram of the structure of a circulating water waste heat utilization system for an indirect air-cooling unit. The connection relationship of each device is as follows: including a steam turbine 1, a condenser 2, an ejector 4, a heat exchanger 5 and a heater 6;

[0030] The exhaust port of the steam turbine 1 is connected to the hot side inlet of the condenser 2, the extraction port of the steam turbine 1 is connected to the steam side inlet of the ejector 4, the circulating water branch of the cold side outlet of the condenser 2 is connected to the water side inlet of the ejector 4, the outlet of the ejector 4 is connected to the hot side inlet of the heat exchanger 5, the hot side outlet of the heat exchanger 5 is connected to the hot side inlet of the heater 6, and the hot side outlet of the heater 6 is connected to the circulating water branch of the cold side inlet of the condenser 2. The purpose of the present invention is to provide a system and operation method for utilizing the waste heat of circulating water of an indirect air-cooling unit, wherein the system heats the circulating water by high-temperature extraction steam injection and uses it for external heating or cooling, and the waste heat is also recovered and utilized by the heater. The system can effectively realize the recycling of the heat of the circulating water, greatly improve the economy of the unit, have a large energy-saving benefit, and effectively avoid corrosion and clogging of the air preheater.

[0031] Preferably, a first control valve 9 is provided between the steam extraction port of the steam turbine 1 and the steam side inlet of the ejector 4 .

[0032] Preferably, a second control valve 10 is provided between the circulating water branch at the cold side outlet of the condenser 2 and the water side inlet of the ejector 4 .

[0033] Preferably, a cooling tower 3 is further included, and the cold side of the condenser 2 is connected to the cooling tower 3.

[0034] Preferably, an air preheater 7 is further included, and the cold side outlet of the heater 6 is connected to the cold side inlet of the air preheater 7.

[0035] Preferably, a low-temperature economizer 8 is provided at the hot side outlet of the air preheater 7 .

[0036] Preferably, the hot air side outlet of the air preheater 7 is connected to the air side inlet of the boiler; the flue gas side inlet of the air preheater 7 is connected to the flue gas outlet of the boiler.

[0037] Preferably, the high-temperature water of the heat exchanger 5 is connected to a heat user.

[0038] Preferably, the cold side inlet of the heater 6 is connected to a cold air source.

[0039] An operating method of an indirect air-cooling unit circulating water waste heat utilization system, comprising:

[0040] A stream of high-temperature steam is drawn from the steam turbine 1 into the ejector 4, where it is mixed with the hot water from the circulating cooling water branch at the cold side outlet of the condenser 2 and heated. The heated high-temperature water releases heat to the outside in the heat exchanger 5. The hot water that releases heat to the outside in the heat exchanger 5 heats the cold air in the air heater 6. The air that absorbs heat is heated by the air preheater 7 and then enters the boiler, while the cold water that releases heat is mixed with the circulating cooling water and then enters the condenser 2.

[0041] This indirect air-cooled unit circulating water waste heat utilization system heats the circulating water through high-temperature extraction steam injection, which is then used for external heating or cooling. The waste heat is also recovered and utilized by the air heater. This system effectively recycles the circulating water's heat, significantly improving the unit's economic efficiency, achieving significant energy savings, and effectively preventing corrosion and clogging of the air preheater. The system, described herein, employs an air heater in conjunction with a low-temperature economizer. This system, while increasing the inlet temperature of the air preheater and effectively preventing corrosion and clogging, also improves boiler combustion conditions, increasing boiler efficiency while reducing turbine heat consumption, resulting in significant energy savings.

[0042] The specific implementation methods are as follows:

[0043] like Figure 1 The figure shows a schematic diagram of the structure of a circulating water waste heat utilization system for an indirect air-cooled unit. The main working principle is as follows: the system draws a stream of high-temperature steam from the steam turbine 1 into the ejector 4, where it is mixed with hot water from the circulating cooling water branch at the cold side outlet of the condenser 2 and heated. The heated high-temperature water releases heat to the outside in the heat exchanger 5, serving as a heat source for external heating in winter or driving absorption refrigeration in summer. The hot water that has released heat to the outside in the heat exchanger 5 heats the cold air in the heater 6. The air that has absorbed heat is heated by the air preheater 7 and then enters the boiler. The cold water that has released heat is mixed with the circulating cooling water and then enters the condenser 2. The flue gas is heat recovered through the air preheater 7 and the low-temperature economizer 8.

[0044] The system of the present invention is equipped with a first control valve 9 on the steam extraction pipeline for adjusting the amount of steam extraction; a second control valve 10 is installed on the circulating water branch for adjusting the flow rate of the injected circulating water; when the system is operated in winter, the circulating water temperature is low, and the first control valve 9 can be adjusted to a larger value and the second control valve 10 can be adjusted to a smaller value to ensure that the injected hot water can meet the external heating load when releasing heat in the heat exchanger 5; when the system is operated in summer, the high circulating water temperature will cause high back pressure in the steam turbine, thereby reducing the circulation efficiency, and the first control valve 9 and the second control valve 10 can be adjusted to increase the circulating water flow rate of the condenser 2 to reduce the circulation back pressure, while the injected hot water drives the absorption refrigeration in the heat exchanger 5 to meet the summer cooling capacity demand;

[0045] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in this industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A system for utilizing waste heat from circulating water of an indirect air-cooling unit, characterized in that: It includes a steam turbine (1), a condenser (2), an ejector (4), a heat exchanger (5) and an air heater (6); The exhaust port of the steam turbine (1) is connected to the hot side inlet of the condenser (2), the extraction port of the steam turbine (1) is connected to the steam side inlet of the ejector (4), the circulating water branch of the cold side outlet of the condenser (2) is connected to the water side inlet of the ejector (4), the outlet of the ejector (4) is connected to the hot side inlet of the heat exchanger (5), the hot side outlet of the heat exchanger (5) is connected to the hot side inlet of the heater (6), and the hot side outlet of the heater (6) is connected to the circulating water branch of the cold side inlet of the condenser (2); A first control valve (9) is provided between the steam extraction port of the steam turbine (1) and the steam side inlet of the ejector (4); A second control valve (10) is provided between the circulating water branch of the cold side outlet of the condenser (2) and the water side inlet of the ejector (4); It also includes an air preheater (7), wherein the cold side outlet of the heater (6) is connected to the cold side inlet of the air preheater (7); and a low-temperature economizer (8) is provided at the hot side outlet of the air preheater (7).

2. The indirect air cooling unit circulating water waste heat utilization system according to claim 1, characterized in that: It also includes a cooling tower (3), and the cold side of the condenser (2) is connected to the cooling tower (3).

3. The indirect air cooling unit circulating water waste heat utilization system according to claim 1, characterized in that: The hot air side outlet of the air preheater (7) is connected to the air side inlet of the boiler; and the flue gas side inlet of the air preheater (7) is connected to the flue gas outlet of the boiler.

4. The indirect air cooling unit circulating water waste heat utilization system according to claim 1, characterized in that: The high-temperature water of the heat exchanger (5) is connected to the heat user.

5. The indirect air cooling unit circulating water waste heat utilization system according to claim 1, characterized in that: The cold side inlet of the heater (6) is connected to a cold air source.

6. An operating method of an indirect air-cooling unit circulating water waste heat utilization system, based on the indirect air-cooling unit circulating water waste heat utilization system according to any one of claims 1 to 5, characterized in that: include, A stream of high-temperature steam is drawn from the steam turbine (1) into the ejector (4), and is mixed with the hot water of the circulating cooling water branch at the cold side outlet of the condenser (2) in the ejector (4) and heated. The heated high-temperature water releases heat to the outside in the heat exchanger (5). The hot water that releases heat to the outside in the heat exchanger (5) heats the cold air in the air heater (6). The air that absorbs heat is heated by the air preheater (7) and then enters the boiler. The cold water that releases heat is mixed with the circulating cooling water and then enters the condenser (2).

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