Waste heat utilization system and coal-fired unit

Abstract

The invention discloses a waste heat utilization system and a coal-fired unit, the waste heat utilization system is used for the coal-fired unit, the coal-fired unit comprises a boiler, a flue and a steam turbine, the flue and the steam turbine are both connected to the boiler, and the steam turbine comprises an intermediate-pressure cylinder and a low-pressure cylinder connected to the downstream of the intermediate-pressure cylinder; the waste heat utilization system comprises a heat supply flow path, a first heat exchanger and a second heat exchanger, the liquid inlet end of a first heat exchange pipe of the first heat exchanger is connected with a downstream pipeline of the medium-pressure cylinder, and the liquid outlet end of a first loop of the heat supply flow path is connected with the liquid inlet end of a second heat exchange pipe of the first heat exchanger; the liquid inlet end of a third heat exchange pipe of the second heat exchanger is connected with a downstream pipeline of the flue, and the liquid outlet end of a second loop of the heat supply flow path is connected with the liquid inlet end of a fourth heat exchange pipe of the second heat exchanger. According to the waste heat utilization system, the waste heat of the flue gas in the flue is used for heating the heat supply return water so as to reduce the content of medium-pressure medium-temperature steam extracted from the outlet of the medium-pressure cylinder, and therefore safe operation of the low-pressure cylinder can be guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat recovery of coal-fired units, and in particular to a waste heat utilization system and a coal-fired unit. Background Art

[0002] In the related art, a coal-fired unit extracts a part of medium-pressure and medium-temperature steam at the outlet of the intermediate-pressure cylinder to heat the heating return water to the heating temperature. However, the extraction amount of the medium-pressure and medium-temperature steam is large, resulting in a small amount of steam entering the low-pressure cylinder, which may affect the safe operation of the low-pressure cylinder. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, an object of the present invention is to provide a waste heat utilization system that uses the waste heat of the flue gas in the flue to heat the heating return water, thereby reducing the content of the medium-pressure and medium-temperature steam extracted from the outlet of the intermediate-pressure cylinder, and thus ensuring the safe operation of the low-pressure cylinder.

[0004] The present invention also provides a coal-fired unit having the above waste heat utilization system.

[0005] The waste heat utilization system according to the first aspect embodiment of the present invention is used for a coal-fired unit. The coal-fired unit includes a boiler, a flue, and a steam turbine. The flue and the steam turbine are both connected to the boiler. The steam turbine includes an intermediate-pressure cylinder and a low-pressure cylinder. The low-pressure cylinder is connected to a part of the downstream pipeline of the intermediate-pressure cylinder. The waste heat utilization system includes: a heating flow path, which includes a first circuit, a second circuit, and a first outlet; a first heat exchanger, which includes a first heat exchange tube and a second heat exchange tube that exchange heat with each other. The liquid inlet end of the first heat exchange tube is connected to the downstream pipeline of the intermediate-pressure cylinder, and the liquid outlet end of the first circuit is connected to the liquid inlet end of the second heat exchange tube; a second heat exchanger, which includes a third heat exchange tube and a fourth heat exchange tube that exchange heat with each other. The liquid inlet end of the third heat exchange tube is connected to the downstream pipeline of the flue, and the liquid outlet end of the second circuit is connected to the liquid inlet end of the fourth heat exchange tube; wherein, the liquid outlet ends of the second heat exchange tube and the fourth heat exchange tube are both connected to the liquid inlet end of the first outlet.

[0006] According to the waste heat utilization system of the embodiment of the present invention, a second heat exchanger is provided downstream of the flue to use the waste heat of the flue gas in the flue to heat the heating return water, so as to share part of the workload of the first heat exchanger, thereby reducing the content of the medium-pressure and medium-temperature steam extracted from the outlet of the intermediate-pressure cylinder, and thus ensuring the safe operation of the low-pressure cylinder.

[0007] According to some embodiments of the present invention, the waste heat utilization system further includes: a third heat exchanger and a heat pump. The third heat exchanger includes a fifth heat exchange tube and a sixth heat exchange tube that exchange heat with each other. The liquid inlet end of the fifth heat exchange tube is connected to a partial downstream pipeline of the low-pressure cylinder. The heat pump includes a seventh heat exchange tube and an eighth heat exchange tube that exchange heat with each other. The liquid outlet end of the sixth heat exchange tube is connected to the liquid inlet end of the seventh heat exchange tube through a pipeline. The liquid outlet end of the seventh heat exchange tube is connected to the liquid inlet end of the sixth heat exchange tube through a pipeline. The heat supply flow path further includes: a third circuit. The liquid inlet end of the third circuit is connected to the liquid inlet end of the eighth heat exchange tube. The liquid outlet end of the eighth heat exchange tube is connected to both the liquid inlet end of the first circuit and the liquid inlet end of the second circuit.

[0008] According to some embodiments of the present invention, the intermediate-pressure cylinder is communicated with the first heat exchange tube through a first connecting pipe, and the first connecting pipe is provided with a first regulating valve; and / or, the intermediate-pressure cylinder is communicated with the low-pressure cylinder through a second connecting pipe, and the second connecting pipe is provided with a second regulating valve.

[0009] According to some embodiments of the present invention, the waste heat utilization system further includes: an ejector. The ejector is arranged on the downstream pipeline of the low-pressure cylinder. The liquid outlet end of the third heat exchange tube is communicated with the ejector through a pipeline.

[0010] According to some embodiments of the present invention, the coal-fired unit further includes: an air preheater. The air preheater includes an air inlet pipe and a flue gas outlet pipe that exchange heat with each other. The air inlet pipe is connected to the upstream pipeline of the boiler. The flue gas outlet pipe is connected to the downstream pipeline of the flue. The waste heat utilization system further includes: a first-stage low-temperature heat exchanger. The first-stage low-temperature heat exchanger includes a ninth heat exchange tube and a tenth heat exchange tube that exchange heat with each other. The gas outlet end of the flue gas outlet pipe is connected to the liquid inlet end of the ninth heat exchange tube. The heat pump further includes an eleventh heat exchange tube that exchanges heat with the eighth heat exchange tube. The liquid inlet end of the eleventh heat exchange tube is connected to the liquid outlet end of the tenth heat exchange tube through a pipeline. The liquid outlet end of the eleventh heat exchange tube is connected to the liquid inlet end of the tenth heat exchange tube through a pipeline.

[0011] According to some embodiments of the present invention, the waste heat utilization system further includes: a second-stage low-temperature heat exchanger. The second-stage low-temperature heat exchanger includes a twelfth heat exchange tube and a thirteenth heat exchange tube that exchange heat with each other. The liquid outlet end of the ninth heat exchange tube is connected to the liquid inlet end of the thirteenth heat exchange tube through a pipeline. The liquid outlet end of the eleventh heat exchange tube is connected to the liquid inlet end of the twelfth heat exchange tube through a pipeline. The liquid outlet end of the twelfth heat exchange tube is connected to the liquid inlet end of the tenth heat exchange tube through a pipeline.

[0012] According to some embodiments of the present invention, the waste heat utilization system further includes: a warm air blower, the warm air blower includes a thirteenth heat exchange tube, the thirteenth heat exchange tube is connected to the upstream of the air inlet pipe through a pipeline, and the warm air blower is adapted to heat the air in the thirteenth heat exchange tube.

[0013] According to some embodiments of the present invention, the waste heat utilization system further includes: a first heat exchange circuit and a second heat exchange circuit, the warm air blower includes a fourteenth heat exchange tube that exchanges heat with the thirteenth heat exchange tube, the first heat exchange circuit is connected between the liquid outlet end of the eighth heat exchange tube and the liquid inlet end of the fourteenth heat exchange tube, the second heat exchange circuit is connected between the liquid outlet end of the fourteenth heat exchange tube and the liquid outlet end of the eighth heat exchange tube, and the first heat exchange circuit is located upstream of the second heat exchange circuit.

[0014] According to some embodiments of the present invention, the liquid outlet end of the third heat exchange tube is connected to the liquid inlet end of the ninth heat exchange tube through a pipeline.

[0015] A coal-fired power unit according to an embodiment of the second aspect of the present invention includes: the waste heat utilization system according to the above-mentioned first aspect embodiment of the present invention.

[0016] According to the embodiment of the present invention, by providing the above-mentioned waste heat utilization system, a second heat exchanger is provided downstream of the flue, and the waste heat of the flue gas in the flue is used to heat the heating return water. A second heat exchanger is provided downstream of the low-pressure cylinder, and the low-pressure low-temperature steam flowing out from the outlet of the low-pressure cylinder is used to preheat the heating return water, so as to fully utilize the waste heat of the coal-fired power unit and improve the waste heat utilization rate of the coal-fired power unit.

[0017] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, in which:

[0019] Figure 1 is a schematic diagram of a waste heat utilization system according to some embodiments of the present invention.

[0020] Reference numerals:

[0021] 100, waste heat utilization system;

[0022] 11, air preheater; 12, intermediate pressure cylinder; 13, low pressure cylinder; 14, ejector; 15, condenser;

[0023] 2. Heating flow path; 21. First circuit; 22. Second circuit; 23. Third circuit; 24. First outlet

[0024] 31. First heat exchanger; 32. Second heat exchanger; 321. Fourth heat exchange tube; 33. Third heat exchanger; 331. Sixth heat exchange tube

[0025] 41. Heat pump; 411. Seventh heat exchange tube; 412. Eighth heat exchange tube; 413. Eleventh heat exchange tube

[0026] 51. First connecting pipe; 511. First regulating valve; 52. Second connecting pipe; 521. Second regulating valve

[0027] 61. First-stage low-temperature heat exchanger; 611. Tenth heat exchange tube; 62. Second-stage low-temperature heat exchanger; 621. Twelfth heat exchange tube

[0028] 71. Warm air blower; 711. Fourteenth heat exchange tube; 72. First heat exchange circuit; 73. Second heat exchange circuit Detailed implementation manners

[0029] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0030] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "front", "rear", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0031] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal communication between two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] The following refers to Figure 1 Describe the waste heat utilization system 100 according to an embodiment of the present invention.

[0033] The waste heat utilization system 100 according to the first aspect embodiment of the present invention, the waste heat utilization system 100 is used for a coal-fired unit. The coal-fired unit includes a boiler, a flue, and a steam turbine. The flue and the steam turbine are both connected to the boiler. The steam turbine includes an intermediate pressure cylinder 12 and a low pressure cylinder 13. The low pressure cylinder 13 is connected to a partial downstream pipeline of the intermediate pressure cylinder 12. The boiler is used to burn coal to heat water. The steam generated during heating enters the intermediate pressure cylinder 12 of the steam turbine. The steam expands and does work in the intermediate pressure cylinder 12 and the intermediate pressure cylinder 12 to drive the generator to work. The flue gas generated during coal combustion is discharged through the flue.

[0034] The waste heat utilization system 100 includes a heat supply flow path 2, a first heat exchanger 31, and a second heat exchanger 32. The heat supply flow path 2 has heating return water and heating feed water flowing therein. The heating return water is low-temperature water returned from the user end to the coal-fired unit, and the coal-fired unit is used to reheat the heating return water. The heating feed water is the water after being heated and then enters the user end again.

[0035] In the related art, the coal-fired unit extracts a part of the intermediate pressure and medium-temperature steam at the outlet of the intermediate pressure cylinder 12 to heat the heating return water to reach the heating temperature. However, the extraction amount of the part of the intermediate pressure and medium-temperature steam is large, resulting in a small amount of steam entering the low pressure cylinder 13, which may affect the safe operation of the low pressure cylinder 13. In the present invention, a second heat exchanger 32 is provided downstream of the flue, and the waste heat of the flue gas in the flue is used to heat the heating return water, so as to share part of the workload of the first heat exchanger 31, and thus the content of the part of the intermediate pressure and medium-temperature steam extracted from the outlet of the intermediate pressure cylinder 12 can be reduced, thereby ensuring the safe operation of the low pressure cylinder 13.

[0036] Specifically refer to Figure 1 , Figure 1The direction of the arrow in the figure is the flow direction of the medium water, flue gas, heating return water, and heating feed water. The heating flow path 2 includes a first circuit 21, a second circuit 22, and a first outlet 24. The first heat exchanger 31 includes a first heat exchange tube and a second heat exchange tube that exchange heat with each other. The liquid inlet end of the first heat exchange tube is connected to the downstream pipeline of the intermediate pressure cylinder 12. The intermediate pressure and medium temperature steam extracted from the intermediate pressure cylinder 12 enters the first heat exchange tube through the downstream pipeline of the intermediate pressure cylinder 12. The liquid outlet end of the first circuit 21 is connected to the liquid inlet end of the first heat exchange tube. The heating return water in the first circuit 21 enters the second heat exchange tube. The intermediate pressure and medium temperature steam in the first heat exchange tube can heat the heating return water in the second heat exchange tube. The liquid outlet end of the second heat exchange tube is connected to the liquid inlet end of the first outlet 24. The heated heating return water reaches the temperature of the heating feed water and then enters the user end through the first outlet 24.

[0037] The second heat exchanger 32 includes a third heat exchange tube and a fourth heat exchange tube 321 that exchange heat with each other. The liquid inlet end of the third heat exchange tube is connected to the downstream pipeline of the flue. The flue gas flowing out of the downstream pipeline of the flue enters the third heat exchange tube. The liquid outlet end of the second circuit 22 is connected to the liquid inlet end of the fourth heat exchange tube 321. The heating return water in the second circuit 22 enters the fourth heat exchange tube 321. The flue gas in the third heat exchange tube can heat the heating return water in the fourth heat exchange tube 321. The liquid outlet end of the fourth heat exchange tube 321 is connected to the liquid inlet end of the first outlet 24. The heated heating return water reaches the temperature of the heating feed water and then enters the user end through the first outlet 24.

[0038] According to the waste heat utilization system 100 of the embodiment of the present invention, a second heat exchanger 32 is provided downstream of the flue, and the waste heat of the flue gas in the flue is used to heat the heating return water, so as to share part of the workload of the first heat exchanger 31, and thus the content of the intermediate pressure and medium temperature steam extracted from the outlet of the intermediate pressure cylinder 12 can be reduced, thereby ensuring the safe operation of the low pressure cylinder 13.

[0039] According to some embodiments of the present invention, referring to Figure 1 , the waste heat utilization system 100 further includes a third heat exchanger 33 and a heat pump 41. The third heat exchanger 33 includes a fifth heat exchange tube and a sixth heat exchange tube 331 that exchange heat with each other. The liquid inlet end of the fifth heat exchange tube is connected to a part of the downstream pipeline of the low pressure cylinder 13. The low pressure and low temperature steam extracted from the low pressure cylinder 13 enters the fifth heat exchange tube. The low pressure and low temperature steam heats the medium water in the sixth heat exchange tube 331 in the third heat exchanger 33.

[0040] The heat pump 41 includes a seventh heat exchange tube 411 and an eighth heat exchange tube 412 that exchange heat with each other. The liquid outlet end of the sixth heat exchange tube 331 is connected to the liquid inlet end of the seventh heat exchange tube 411 through a pipeline. The medium water flowing out of the sixth heat exchange tube 331 enters the seventh heat exchange tube 411 of the heat pump 41. The liquid inlet end of the eighth heat exchange tube 412 is connected to the liquid outlet end of the third circuit 23. The liquid in the eighth heat exchange tube 412 is the heating return water. In the heat pump 41, the medium water in the seventh heat exchange tube 411 initially heats the heating return water in the eighth heat exchange tube 412. The liquid outlet end of the eighth heat exchange tube 412 is connected to both the liquid inlet end of the first circuit 21 and the liquid inlet end of the second circuit 22. The heated heating return water in the eighth heat exchange tube 412 is divided into two streams. One stream enters the first circuit 21, and the other stream enters the second circuit 22. The liquid outlet end of the seventh heat exchange tube 411 is connected to the liquid inlet end of the sixth heat exchange tube 331 through a pipeline. The medium water in the seventh heat exchange tube 411 enters the sixth heat exchange tube 331 through the pipeline after initially heating the heating return water in the eighth heat exchange tube 412. In the third heat exchanger 33, the low-pressure and low-temperature steam in the fifth heat exchange tube continues to heat the medium water in the sixth heat exchange tube 331.

[0041] With the above arrangement, the low-pressure and low-temperature steam flowing out of the low-pressure cylinder 13 is fully utilized to initially heat the heating return water.

[0042] For example, a condenser 15 is further provided downstream of the third heat exchanger 33 for cooling the steam flowing out of the fifth heat exchange tube of the third heat exchanger 33.

[0043] According to some embodiments of the present invention, referring to Figure 1 , the intermediate-pressure cylinder 12 and the first heat exchange tube are connected through a first connecting pipe 51. The first connecting pipe 51 is provided with a first regulating valve 511. The opening size of the first connecting pipe 51 can be adjusted through the first regulating valve 511, and thus the flow rate of the medium-temperature and medium-pressure steam entering the first heat exchanger 31 through the first connecting pipe 51 can be adjusted. The intermediate-pressure cylinder 12 and the low-pressure cylinder 13 are connected through a second connecting pipe 52. The second connecting pipe 52 is provided with a second regulating valve 521. The opening size of the second connecting pipe 52 can be adjusted through the second regulating valve 521, and thus the flow rate of the medium-temperature and medium-pressure steam entering the low-pressure cylinder 13 through the second connecting pipe 52 can be adjusted, and the medium-temperature and medium-pressure steam flowing out of the intermediate-pressure cylinder 12 can be reasonably distributed.

[0044] According to some embodiments of the present invention, referring to Figure 1 , the waste heat utilization system 100 further includes: an ejector 14. The ejector 14 is arranged on the downstream pipeline of the low-pressure cylinder 13. The liquid outlet end of the first heat exchange tube is connected to the ejector 14 through a pipeline. The ejector 14 can collect the steam flowing out of the downstream pipeline of the low-pressure cylinder 13 and the liquid outlet end of the first heat exchange tube. By reusing the steam flowing out of the first heat exchange tube, the utilization rate of the waste heat utilization system 100 can be improved.

[0045] According to some embodiments of the present invention, with reference to Figure 1 , the coal-fired unit further includes an air preheater 11. The air preheater 11 is located upstream of the boiler. The air preheater 11 preheats the air entering the boiler to improve the combustion efficiency of the boiler.

[0046] The air preheater 11 includes an air inlet pipe and a flue gas outlet pipe that exchange heat with each other. The air inlet pipe is connected to the upstream pipeline of the boiler, and the flue gas outlet pipe is connected to the downstream pipeline of the flue. The waste heat of the flue gas in the flue gas outlet pipe is used to preheat the air in the air inlet pipe, and the heat of the flue gas can be fully utilized.

[0047] The waste heat utilization system 100 further includes a first-stage low-temperature heat exchanger 61. The first-stage low-temperature heat exchanger 61 includes a ninth heat exchange pipe and a tenth heat exchange pipe 611 that exchange heat with each other. The outlet end of the flue gas outlet pipe is connected to the inlet end of the ninth heat exchange pipe. The heat pump 41 further includes an eleventh heat exchange pipe 413. The inlet end of the eleventh heat exchange pipe 413 is connected to the outlet end of the tenth heat exchange pipe 611 through a pipeline, and the outlet end of the eleventh heat exchange pipe 413 is connected to the inlet end of the tenth heat exchange pipe 611 through a pipeline.

[0048] The flue gas flowing out of the flue gas outlet pipe heats the medium water in the tenth heat exchange pipe 611 in the first-stage low-temperature heat exchanger 61. The outlet end of the tenth heat exchange pipe 611 is connected to the inlet end of the eleventh heat exchange pipe 413 through a pipeline. In the heat pump 41, the medium water in the eleventh heat exchange pipe 413 heats the heating return water in the eighth heat exchange pipe 412. After heating, the medium water in the eleventh heat exchange pipe 413 enters the tenth heat exchange pipe 611 through a pipeline. In the first-stage low-temperature heat exchanger 61, the flue gas in the ninth heat exchange pipe heats the medium water in the tenth heat exchange pipe 611 again, fully utilizing the flue gas flowing out of the air preheater 11, using the waste heat of the flue gas to heat the tenth heat exchange pipe 611 in the first-stage low-temperature heat exchanger 61, and the heat in the tenth heat exchange pipe 611 flows to the heat pump 41 through a pipeline to preliminarily heat the heating return water in the heat pump 41.

[0049] According to some embodiments of the present invention, with reference to Figure 1 , the waste heat utilization system 100 further includes: a second-stage low-temperature heat exchanger 62. The second-stage low-temperature heat exchanger 62 includes a twelfth heat exchange pipe 621 and a thirteenth heat exchange pipe that exchange heat with each other. The outlet end of the ninth heat exchange pipe is connected to the inlet end of the thirteenth heat exchange pipe through a pipeline. The outlet end of the eleventh heat exchange pipe 413 is connected to the inlet end of the twelfth heat exchange pipe 621 through a pipeline. The outlet end of the twelfth heat exchange pipe 621 is connected to the inlet end of the tenth heat exchange pipe 611 through a pipeline.

[0050] In the heat pump 41, the heat of the eleventh heat exchange tube 413 is transferred to the heating return water in the eighth heat exchange tube 412 to preliminarily heat the heating return water. The medium water in the eleventh heat exchange tube 413 flows through a pipeline into the twelfth heat exchange tube 621 of the second-stage low-temperature heat exchanger 62. In the second-stage low-temperature heat exchanger 62, the waste heat of the flue gas in the thirteenth heat exchange tube heats the medium water in the twelfth heat exchange tube 621. Then, the medium water in the twelfth heat exchange tube 621 enters the tenth heat exchange tube 611 of the first-stage low-temperature heat exchanger 61 through a pipeline. In the first-stage low-temperature heat exchanger 61, the flue gas in the ninth heat exchange tube heats the medium water in the tenth heat exchange tube 611. Then, the medium water in the tenth heat exchange tube 611 enters the eleventh heat exchange tube 413 of the heat pump 41 again to heat the heating return water, completing a cycle.

[0051] By providing the second-stage low-temperature heat exchanger 62, the medium water flowing out of the heat pump 41 is preliminarily heated to reuse the waste heat of the flue gas flowing out of the first-stage low-temperature heat exchanger 61.

[0052] According to some embodiments of the present invention, referring to Figure 1 , the waste heat utilization system 100 further includes: a warm air blower 71. The warm air blower 71 includes a thirteenth heat exchange tube, and the thirteenth heat exchange tube is connected to the upstream of the air inlet pipe through a pipeline. The warm air blower 71 is adapted to heat the air in the thirteenth heat exchange tube.

[0053] Part of the flue gas is extracted at the inlet of the air preheater 11, which causes the air preheating capacity of the air preheater 11 to be insufficient, resulting in the air at the outlet of the air preheater 11 not reaching the target value. By providing the warm air blower 71 on the air inlet side of the air preheater 11, the warm air blower 71 preliminarily heats the air entering the air preheater 11 to increase the temperature of the air entering the air preheater 11.

[0054] According to some embodiments of the present invention, referring to Figure 1 , the waste heat utilization system 100 further includes: a first heat exchange circuit 72 and a second heat exchange circuit 73. The warm air blower 71 includes a fourteenth heat exchange tube 711 that exchanges heat with the thirteenth heat exchange tube. The first heat exchange circuit 72 is connected between the liquid outlet end of the eighth heat exchange tube 412 and the liquid inlet end of the fourteenth heat exchange tube 711. The second heat exchange circuit 73 is connected between the liquid outlet end of the fourteenth heat exchange tube 711 and the liquid outlet end of the eighth heat exchange tube 412. The first heat exchange circuit 72 is located upstream of the second heat exchange circuit 73.

[0055] The heating return water flowing out of the eighth heat exchange tube 412 can enter the fourteenth heat exchange tube 711 of the air heater 71 through the first heat exchange circuit 72, and is used to heat the air in the thirteenth heat exchange tube. The heating return water in the fourteenth heat exchange tube 711 after heating the air returns to the pipeline connected to the liquid outlet end of the eighth heat exchange tube 412 again through the second heat exchange circuit 73, and is connected downstream of the first heat exchange circuit 72. Part of the heating return water flowing out of the eighth heat exchange tube 412 is extracted to preheat the air in the air heater 71, so as to increase the temperature of the air entering the air preheater 11.

[0056] According to some embodiments of the present invention, referring to Figure 1 , the liquid outlet end of the third heat exchange tube is connected to the liquid inlet end of the ninth heat exchange tube through a pipeline, and the flue gas flowing out of the third heat exchange tube is introduced into the ninth heat exchange tube in the first-stage low-temperature heat exchanger 61, so as to make full use of the waste heat of the flue gas flowing out of the second heat exchanger 32, and the utilization rate of the waste heat of the flue gas can be improved.

[0057] The coal-fired power unit according to the second aspect embodiment of the present invention includes: the waste heat utilization system 100 according to the above first aspect embodiment of the present invention.

[0058] According to the coal-fired power unit of the embodiment of the present invention, by arranging the above waste heat utilization system 100, a second heat exchanger 32 is arranged downstream of the flue, and the waste heat of the flue gas in the flue is used to heat the heating return water. A second heat exchanger 32 is arranged downstream of the low-pressure cylinder 13, and the low-pressure low-temperature steam flowing out of the outlet of the low-pressure cylinder 13 is used to preheat the heating return water, so as to make full use of the waste heat of the coal-fired power unit and improve the waste heat utilization rate of the coal-fired power unit.

[0059] In the description of this specification, the description referring to terms such as "some embodiments", "optionally", "further" or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0060] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purposes of the present invention, and the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A waste heat utilization system, characterized in that: For a coal-fired unit, the coal-fired unit includes a boiler, a flue and a steam turbine, the flue and the steam turbine are both connected to the boiler, the steam turbine includes an intermediate pressure cylinder and a low pressure cylinder, the low pressure cylinder is connected to part of the downstream pipeline of the intermediate pressure cylinder, and the waste heat utilization system includes: A heat supply flow path, the heat supply flow path comprising a first loop, a second loop and a first outlet; A first heat exchanger, the first heat exchanger comprising a first heat exchange tube and a second heat exchange tube for exchanging heat with each other, a liquid inlet end of the first heat exchange tube being connected to a downstream pipeline of the intermediate pressure cylinder, and a liquid outlet end of the first circuit being connected to a liquid inlet end of the second heat exchange tube; A second heat exchanger, wherein the second heat exchanger comprises a third heat exchange tube and a fourth heat exchange tube for exchanging heat with each other, the liquid inlet end of the third heat exchange tube is connected to the downstream pipeline of the flue, and the liquid outlet end of the second circuit is connected to the liquid inlet end of the fourth heat exchange tube; Wherein, the liquid outlet end of the second heat exchange tube and the liquid outlet end of the fourth heat exchange tube are both connected to the liquid inlet end of the first outlet.

2. The waste heat utilization system according to claim 1, characterized in that: The waste heat utilization system also includes: a third heat exchanger and a heat pump, the third heat exchanger includes a fifth heat exchange tube and a sixth heat exchange tube for mutual heat exchange, the liquid inlet end of the fifth heat exchange tube is connected to a part of the downstream pipeline of the low-pressure cylinder, the heat pump includes a seventh heat exchange tube and an eighth heat exchange tube for mutual heat exchange, the liquid outlet end of the sixth heat exchange tube is connected to the liquid inlet end of the seventh heat exchange tube through a pipeline, the liquid outlet end of the seventh heat exchange tube is connected to the liquid inlet end of the sixth heat exchange tube through a pipeline, the heat supply flow path also includes: a third loop, the liquid inlet end of the third loop is connected to the liquid inlet end of the eighth heat exchange tube, the liquid outlet end of the eighth heat exchange tube is connected to both the liquid inlet end of the first loop and the liquid inlet end of the second loop.

3. The waste heat utilization system according to claim 2, characterized in that: The intermediate pressure cylinder is connected to the first heat exchange tube via a first connecting pipe, which has a first regulating valve; and / or the intermediate pressure cylinder is connected to the low pressure cylinder via a second connecting pipe, which has a second regulating valve.

4. The waste heat utilization system according to claim 2, characterized in that: The waste heat utilization system further includes: an ejector, which is arranged on a downstream pipeline of the low-pressure cylinder, and the liquid outlet end of the first heat exchange tube is connected to the ejector through a pipeline.

5. The waste heat utilization system according to claim 2, characterized in that: The coal-fired unit also includes: an air preheater, the air preheater includes an air inlet pipe and a flue gas outlet pipe for mutual heat exchange, the air inlet pipe is connected to the upstream pipeline of the boiler, and the flue gas outlet pipe is connected to the downstream pipeline of the flue, and the waste heat utilization system also includes: a first-stage low-temperature heat exchanger, the first-stage low-temperature heat exchanger includes a ninth heat exchange tube and a tenth heat exchange tube for mutual heat exchange, the air outlet end of the flue gas outlet pipe is connected to the liquid inlet end of the ninth heat exchange tube, the heat pump also includes an eleventh heat exchange tube for heat exchange with the eighth heat exchange tube, the liquid inlet end of the eleventh heat exchange tube is connected to the liquid outlet end of the tenth heat exchange tube through a pipeline, and the liquid outlet end of the eleventh heat exchange tube is connected to the liquid inlet end of the tenth heat exchange tube through a pipeline.

6. The waste heat utilization system according to claim 5, characterized in that: The waste heat utilization system also includes: a second-stage low-temperature heat exchanger, the second-stage low-temperature heat exchanger includes a twelfth heat exchange tube and a thirteenth heat exchange tube that exchange heat with each other, the liquid outlet end of the ninth heat exchange tube is connected to the liquid inlet end of the thirteenth heat exchange tube through a pipeline, the liquid outlet end of the eleventh heat exchange tube is connected to the liquid inlet end of the twelfth heat exchange tube through a pipeline, and the liquid outlet end of the twelfth heat exchange tube is connected to the liquid inlet end of the tenth heat exchange tube through a pipeline.

7. The waste heat utilization system according to claim 5, characterized in that: The waste heat utilization system also includes: a heater, the heater includes a thirteenth heat exchange tube, the thirteenth heat exchange tube is connected to the upstream of the air intake tube through a pipeline, and the heater is suitable for heating the air in the thirteenth heat exchange tube.

8. The waste heat utilization system according to claim 7, characterized in that: The waste heat utilization system also includes: a first heat exchange circuit and a second heat exchange circuit, the heater includes a fourteenth heat exchange tube that exchanges heat with the thirteenth heat exchange tube, the first heat exchange circuit is connected between the liquid outlet end of the eighth heat exchange tube and the liquid inlet end of the fourteenth heat exchange tube, the second heat exchange circuit is connected between the liquid outlet end of the fourteenth heat exchange tube and the liquid outlet end of the eighth heat exchange tube, and the first heat exchange circuit is located upstream of the second heat exchange circuit.

9. The waste heat utilization system according to claim 5, characterized in that: The liquid outlet end of the third heat exchange tube is connected to the liquid inlet end of the ninth heat exchange tube through a pipeline.

10. A coal-fired unit, characterized in that: include: The waste heat utilization system according to any one of claims 1 to 9.

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