An air-cooled unit cogeneration system and operation method for matching ambient temperature

Abstract

The present invention discloses an air-cooled unit cogeneration system and an operation method that match the ambient temperature. The system combines a medium-pressure steam turbine, a low-pressure steam turbine, a peak heat exchanger, an exhaust steam heat exchanger, and a forced-draft peak cooling tower. Through the connection setting of pipelines and the adjustment of control valves, the multi-purpose utilization of heat exchangers is realized. When the ambient temperature is relatively high in summer, a part of the exhaust steam of the steam turbine is diverted into the heat exchanger to be cooled by circulating water, reducing the heat transfer load of the air-cooled island, lowering the operating back pressure of the unit, and improving the unit efficiency. When there is a heating demand in winter, the exhaust steam and extraction steam of the steam turbine are used for external heating, reducing and utilizing part of the cold source loss, and improving the energy utilization rate and unit efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of cogeneration of heat and power, and relates to a cogeneration system of an air-cooling unit matching ambient temperature and an operation method thereof. Background Art

[0002] Due to the characteristics of the terrain, many resources are unevenly distributed. For example, the Northwest region is rich in coal resources but short of water resources. Therefore, many air-cooled coal-fired power generation units are built in the Northwest. With the changes in the global climate environment, the summer temperature in the Northwest has also increased year by year, making the ambient temperature higher than the design temperature of the unit. The high ambient temperature leads to poor heat exchange effect of the air-cooling island, increased operating back pressure, and poor economic efficiency of the unit. The demand for heating for power generation units in the northern region gradually increases in winter, making the heat exchangers required for heating idle in summer.

[0003] The above-mentioned environmental impacts and the fact that a large number of heat exchangers are idle in summer result in poor economic efficiency of the unit. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide an air-cooled unit cogeneration system and operation method that matches the ambient temperature, so as to solve the problem in the prior art that the economic efficiency of the unit deteriorates due to different ambient temperatures in different regions.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] An air-cooled unit cogeneration system matching ambient temperature includes a medium-pressure steam turbine, a peak heat exchanger, an exhaust steam heat exchanger, and a forced-draft peak cooling tower;

[0007] The exhaust steam of the medium-pressure steam turbine is divided into a first branch and a second branch, the second branch is connected to the steam input end of the low-pressure steam turbine, and the exhaust steam output end of the low-pressure steam turbine is divided into a third branch, a fourth branch and a fifth branch; the third branch and the first branch are connected to the hot side working medium inlet of the peak heat exchanger after merging; the fourth branch is connected to the hot side working medium inlet of the exhaust steam heat exchanger, and the fifth branch is connected to the flue gas cooler of the air-cooling island;

[0008] The cold side working medium inlet of the exhaust steam heat exchanger is connected to the return water of the heat network, the cold side working medium outlet of the exhaust steam heat exchanger is connected to the cold side working medium inlet of the peak heat exchanger, and the cold side working medium outlet of the peak heat exchanger is connected to the water supply of the heat network;

[0009] The cold side working medium inlet of the exhaust steam heat exchanger is simultaneously connected to the outlet of the forced ventilation peak cooling tower, and the cold side working medium outlet of the peak heat exchanger is simultaneously connected to the inlet of the ventilation peak cooling tower.

[0010] A further improvement of the present invention is:

[0011] Preferably, a first control valve is provided on the first branch, a second control valve is provided on the third branch, and a third control valve is provided on the fourth branch.

[0012] Preferably, a heat network circulation pump and a fourth control valve are provided on the cold-side working medium inlet pipeline of the exhaust steam heat exchanger.

[0013] Preferably, a seventh control valve is provided on the connecting pipeline between the outlet of the forced-draft peak cooling tower and the cold-side working medium inlet of the exhaust steam heat exchanger.

[0014] Preferably, a fifth control valve is provided on the connecting pipeline between the cold-side working medium outlet of the peak heat exchanger and the heat network water supply, and a sixth control valve is provided on the connecting pipeline between the cold-side working medium outlet of the peak heat exchanger and the inlet of the forced-draft peak cooling tower.

[0015] Preferably, a peak cooling circulation water pump is provided on the connecting pipeline between the cold-side working medium outlet of the peak heat exchanger and the inlet of the forced-draft peak cooling tower.

[0016] Preferably, the hot-side outlet pipeline of the peak heat exchanger is divided into two branches. One branch is connected to the inlet of the deaerator, and the other branch converges with the outlet of the air-cooled island flue gas cooler and then is jointly connected to the hot well.

[0017] Preferably, an eighth control valve is provided on the connecting pipeline between the peak heat exchanger and the hot well.

[0018] Preferably, the hot-side working medium outlet of the exhaust steam heat exchanger is merged into the connecting pipeline between the peak heat exchanger and the hot well.

[0019] An operation method of an air-cooled unit cogeneration system matching the ambient temperature. In summer, the exhaust steam of the low-pressure steam turbine is cooled in the air-cooled island flue gas cooler, and at the same time, it is cooled by the peak cooling circulating water in the peak heat exchanger and the exhaust steam heat exchanger. The peak cooling circulating water is cooled in the forced-draft peak cooling tower.

[0020] In winter, the return water of the heat network is heated by the exhaust steam of the low-pressure steam turbine in the exhaust steam heat exchanger, and then enters the peak heat exchanger to be heated by the exhaust steam of the medium-pressure steam turbine.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention discloses an air-cooled unit cogeneration system that matches the ambient temperature. This system combines a medium-pressure steam turbine, a low-pressure steam turbine, a peak heat exchanger, an exhaust steam heat exchanger, and a forced-draft peak cooling tower. Through pipeline connections and the adjustment of control valves, multi-purpose utilization of the heat exchangers is achieved. When the ambient temperature is high in summer, a part of the turbine exhaust steam is diverted into the heat exchanger for cooling with circulating water, reducing the heat transfer load of the air-cooled island, lowering the operating back pressure of the unit, and improving the unit efficiency. When there is a heating demand in winter, the turbine exhaust steam and extraction steam are used for external heating, reducing and utilizing part of the cold source loss, and improving the energy utilization rate and unit efficiency. This system can stably and efficiently output both electric and heat loads, and through the adjustment of control valves, the switching of the uses of the heat exchangers in winter and summer is realized, improving the utilization rate of power plant equipment, solving the problems of the summer operating back pressure being higher than the design value and winter heating with a relatively optimal investment, and while meeting the heat and electricity demands of users, improving the efficiency of coal-fired generating units and the energy utilization rate.

[0023] The present invention also discloses an operation method for an air-cooled unit cogeneration system that matches the ambient temperature. This method uses the heat exchanger to cool the turbine exhaust steam in summer to reduce the back pressure of the unit. The system realizes the switching of the uses of the heat exchanger in winter and summer through the adjustment of control valves, improving the utilization rate of power plant equipment, solving the problems of the summer operating back pressure being higher than the design value and winter heating with a relatively optimal investment, and while meeting the heat and electricity demands of users, improving the efficiency of coal-fired generating units and the energy utilization rate. Through the configuration optimization of the heat network return water heating process, the waste heat of the low-pressure steam turbine and the heat of the turbine extraction steam are reasonably utilized, meeting the temperature matching and energy level matching, using lower-temperature heat to meet the heating demand, and improving the energy utilization rate of the unit;

[0024] Furthermore, the peak cooling tower is used to reduce the operating back pressure of the unit in summer, improving the efficiency and energy utilization rate of the unit; Brief Description of the Drawings

[0025] Figure 1 It is the system structure diagram of the present invention;

[0026] Among them: In the figure: 1 is the low-pressure steam turbine, 2 is the air-cooled island flue gas cooler, 3 is the peak heat exchanger, 4 is the exhaust steam heat exchanger, 5 is the forced-draft peak cooling tower, 6 is the heat network circulating water pump, 7 is the peak cooling circulating water pump, 8 is the first control valve, 9 is the second control valve, 10 is the third control valve, 11 is the fourth control valve, 12 is the fifth control valve, 13 is the sixth control valve, 14 is the seventh control valve, 15 is the eighth control valve, 16 is the ninth control valve, 17 is the first branch, 18 is the second branch, 19 is the third branch, 20 is the fourth branch, 21 is the fifth branch. Detailed Embodiments

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

[0028] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It 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 thus should not be construed as a limitation to the present invention; the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. 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.

[0029] The present invention discloses a cogeneration system of an air-cooled unit matching the ambient temperature, which system includes a low-pressure steam turbine 1, an air-cooled island 2, a peak heat exchanger 3, an exhaust steam heat exchanger 4, a peak cooler 5, a heat network circulating pump 6, and a peak cooling circulating pump 7;

[0030] It further includes a first control valve 8, a second control valve 9, a third control valve 10, a fourth control valve 11, a fifth control valve 12, a sixth control valve 13, a seventh control valve 14, an eighth control valve 15, and a ninth control valve 16.

[0031] The outlet of the exhaust steam of the medium-pressure steam turbine is divided into two branches, namely a first branch 17 and a second branch 18. The second branch 18 is connected to the steam inlet of the low-pressure steam turbine 1, and the first branch 17 is communicated with the inlet of the first control valve 8. The steam outlet of the low-pressure steam turbine 1 is divided into three parallel branches, namely a third branch 19, a fourth branch 20, and a fifth branch 21. The outlet of the third branch 19 is communicated with the inlet of the second control valve 9, the outlet of the fourth branch 20 is communicated with the inlet of the third control valve 10, and the fifth branch 21 is connected to the water side inlet of the air-cooled island 2. The outlets of the first control valve 8 and the second control valve 9 converge and are connected to the hot-side working medium inlet of the peak heat exchanger 3.

[0032] The inlet of the working medium on the hot side of the exhaust steam heat exchanger 4 is connected to the outlet of the third control valve 10. The outlet of the working medium on the hot side is connected to the outlet of the water side of the air-cooled island 2, and they jointly flow into the hot well. The connecting pipeline between the outlet of the working medium on the hot side and the water side of the air-cooled island 2 is also connected to the outlet of the eighth control valve 15, so that the outlet of the working medium on the hot side of the peak heat exchanger 3 can flow into the hot well. The inlet of the working medium on the cold side of the exhaust steam heat exchanger 4 is connected to the outlet of the fourth control valve 11 and the outlet of the seventh control valve 14, so that the cold source of the exhaust steam heat exchanger 4 can be the return water of the heat network or the circulating water of the forced draft peak cooling tower 5. The outlet of the working medium on the cold side of the exhaust steam heat exchanger 4 is connected to the inlet of the working medium on the cold side of the peak heat exchanger 3. The inlet of the fourth control valve 11 is connected to the outlet of the heat network circulating pump 6, and the inlet of the heat network circulating pump 6 is connected to the inlet of the heat network return water. The inlet of the seventh control valve 14 is connected to the outlet of the water side of the forced draft peak cooling tower 5.

[0033] The inlet of the working medium on the hot side of the peak heat exchanger 3 is connected to the outlet of the second control valve 9 and the outlet of the first control valve 8. The outlet of the working medium on the hot side of the peak heat exchanger 3 is simultaneously connected to the inlet of the eighth control valve 15 and the inlet of the ninth control valve 16. The outlet of the working medium on the cold side of the peak heat exchanger 3 is divided into two branches. One branch is connected to the inlet of the fifth control valve 12, and one branch is connected to the inlet of the sixth control valve 13. The outlet of the fifth control valve 12 is connected to the heat network water supply, and the outlet of the sixth control valve 13 is connected to the inlet of the peak cooling circulating pump 7; the outlet of the ninth control valve 16 flows into the inlet of the deaerator, and the outlet of the eighth control valve 15 is connected to the inlet of the hot well.

[0034] The inlet of the water side of the forced draft peak cooling tower 5 is connected to the outlet of the peak cooling circulating pump 7, the inlet of the peak cooling circulating pump 7 is connected to the outlet of the sixth control valve 13, and the outlet of the water side of the forced draft peak cooling tower 5 is connected to the inlet of the seventh control valve 14.

[0035] The inlet of the heat network circulating pump 6 is connected to the heat network return water, the outlet of the heat network circulating pump 6 is connected to the inlet of the fourth control valve 11, and the working medium at the outlet of the fifth control valve 12 is used as the heat network water supply.

[0036] Through the design of the above valves and pipelines, it realizes two-way circulation of relying on the forced draft peak cooling tower 5 for cooling in summer, cooling through the heat network return water in winter, and heating the heat network return water at the same time.

[0037] Specifically, the operation method of the present invention is as follows:

[0038] When the ambient temperature is relatively high in summer, the second control valve 9, the third control valve 10, the sixth control valve 13, the seventh control valve 14 and the eighth control valve 15 are opened, and the first control valve 8, the fourth control valve 11, the fifth control valve 12 and the ninth control valve 16 are closed. At this time, the exhaust steam of the medium-pressure steam turbine all enters the low-pressure steam turbine 1. The exhaust steam of the low-pressure steam turbine 1 is divided into two parts. One part enters the air-cooled island flue gas cooler 2 to be cooled, and the other part enters the peak heat exchanger 3 and the exhaust steam heat exchanger 4 through the second control valve 9 and the third control valve 10 respectively. The peak cooling circulating water passes through the cold side of the exhaust steam heat exchanger 4 and the cold side of the peak heater 3 in sequence to cool the exhaust steam of the low-pressure steam turbine 1 entering the hot side of the exhaust steam heat exchanger 4 and the hot side of the peak heat exchanger 3. The peak cooling circulating water is cooled by the forced-draft peak cooling tower 5; after the hot-side working medium outlet of the peak heat exchanger 3 and the hot-side working medium outlet of the exhaust steam heat exchanger 4 converge, they converge with the water-side outlet of the air-cooled island flue gas cooler 2 and jointly flow into the hot well; after the peak cooling circulating water comes out of the forced-draft peak cooling tower 5, it passes through the seventh control valve 14, then passes through the exhaust steam heat exchanger 4 and the peak heat exchanger 3 in sequence, and enters the forced-draft peak cooling tower 5 through the sixth control valve 13 and the peak cooling circulating water pump 7 to be cooled. At this time, the entire heat network circulation pipeline is closed.

[0039] When there is a heating demand in winter, the first control valve 8, the fourth control valve 11, the fifth control valve 12 and the ninth control valve 16 are opened, and the second control valve 9, the third control valve 10, the sixth control valve 13, the seventh control valve 14 and the eighth control valve 15 are closed. The return water of the heat network first passes through the exhaust steam heat exchanger 4 to be heated by using part of the exhaust steam discharged from the low-pressure steam turbine 1, and then enters the peak heat exchanger 3 to be heated by using the extraction steam of the exhaust steam of the medium-pressure steam turbine. Part of the exhaust steam of the medium-pressure steam turbine enters the peak heat exchanger 3 through the first control valve 8 to heat the return water of the heat network, and then enters the deaerator through the ninth control valve 16. Part of the exhaust steam of the low-pressure steam turbine 1 enters the exhaust steam heat exchanger 4 through the third control valve 10 to heat the heat network water and then converges into the hot well. The remaining part of the exhaust steam of the low-pressure steam turbine 1 enters the air-cooled island flue gas cooler 2 to be cooled; to meet the external heat load demand; at this time, the cooling circuit of the forced-draft peak cooling tower 5 is in a shutdown state.

[0040] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An air-cooled unit cogeneration system that matches the ambient temperature, characterized in that, It includes a medium-pressure steam turbine, a peak heat exchanger (3), an exhaust steam heat exchanger (4), and a forced-draft peak cooling tower (5); The exhaust steam of the medium-pressure steam turbine is divided into a first branch (17) and a second branch (18). The second branch (18) is connected to the steam input end of the low-pressure steam turbine (1). The exhaust steam output end of the low-pressure steam turbine (1) is divided into a third branch (19), a fourth branch (20), and a fifth branch (21). After the third branch (19) and the first branch (17) converge, they are connected to the hot-side working fluid inlet of the peak heat exchanger (3). The fourth branch (20) is connected to the hot-side working fluid inlet of the exhaust steam heat exchanger (4), and the fifth branch (21) is connected to the air-cooled island flue gas cooler (2); The cold-side working fluid inlet of the exhaust steam heat exchanger (4) is connected to the return water of the heat network. The cold-side working fluid outlet of the exhaust steam heat exchanger (4) is connected to the cold-side working fluid inlet of the peak heat exchanger (3). The cold-side working fluid outlet of the peak heat exchanger (3) is connected to the heat supply of the heat network; The cold-side working fluid inlet of the exhaust steam heat exchanger (4) is simultaneously connected to the outlet of the forced-draft peak cooling tower (5). The cold-side working fluid outlet of the peak heat exchanger (3) is simultaneously connected to the inlet of the forced-draft peak cooling tower (5); In summer, the exhaust steam of the low-pressure steam turbine (1) is cooled in the air-cooled island flue gas cooler (2) and is simultaneously cooled by the peak cooling circulating water in the peak heat exchanger (3) and the exhaust steam heat exchanger (4). The peak cooling circulating water is cooled in the forced-draft peak cooling tower (5); In winter, the return water of the heat network is heated by the exhaust steam of the low-pressure steam turbine (1) in the exhaust steam heat exchanger (4), and then enters the peak heat exchanger (3) to be heated by the exhaust steam of the medium-pressure steam turbine.

2. The air-cooled unit cogeneration system for matching the ambient temperature according to claim 1, wherein A first control valve (8) is provided on the first branch (17), a second control valve (9) is provided on the third branch (19), and a third control valve (10) is provided on the fourth branch (20).

3. A cogeneration system of an air-cooled unit that matches the ambient temperature according to claim 1, wherein A heat network circulating pump (6) and a fourth control valve (11) are provided on the pipeline of the cold-side working fluid inlet of the exhaust steam heat exchanger (4).

4. A cogeneration system of an air-cooled unit for matching the ambient temperature according to claim 1, characterized in that, A seventh control valve (14) is provided on the pipeline connecting the outlet of the forced-draft peak cooling tower (5) and the cold-side working fluid inlet of the exhaust steam heat exchanger (4).

5. A cogeneration system for an air-cooled unit that matches the ambient temperature according to claim 1, characterized in that, A fifth control valve (12) is provided on the pipeline connecting the cold-side working fluid outlet of the peak heat exchanger (3) and the heat supply of the heat network. A sixth control valve (13) is provided on the pipeline connecting the cold-side working fluid outlet of the peak heat exchanger (3) and the inlet of the forced-draft peak cooling tower (5).

6. A cogeneration system for an air-cooled unit that matches the ambient temperature according to claim 1, characterized in that, A peak cooling circulating water pump (7) is provided on the pipeline connecting the cold-side working fluid outlet of the peak heat exchanger (3) and the inlet of the forced-draft peak cooling tower (5).

7. A cogeneration system of an air-cooled unit that matches the ambient temperature according to claim 1, wherein, The hot-side outlet pipeline of the peak heat exchanger (3) is divided into two branches. One branch is connected to the inlet of the deaerator, and one branch converges with the outlet of the air-cooled island flue gas cooler (2) and is jointly connected to the hot well.

8. A cogeneration system of an air-cooled unit matching the ambient temperature according to claim 7, characterized in that, An eighth control valve (15) is provided on the pipeline connecting the peak heat exchanger (3) and the hot well.

9. A cogeneration system of an air-cooled unit matching the ambient temperature according to claim 8, characterized in that The hot-side working fluid outlet of the exhaust steam heat exchanger (4) is merged into the pipeline connecting the peak heat exchanger (3) and the hot well.

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