A system and method for recovering exhaust steam condensate and waste heat from a thermal power plant

Abstract

The invention discloses a system and method for recovering exhaust steam condensate and waste heat of a thermal power plant, comprising a low-temperature condensate pipe, a hybrid exhaust steam recovery device, a water tank, a non-condensable gas exhaust pipe, an exhaust steam exhaust pipe, a periodic blowdown expansion tank, a water seal valve and an exhaust steam recovery pipe; the outlet of the low-temperature condensate pipe is connected to a cooling water inlet of the hybrid exhaust steam recovery device, the bottom outlet of the hybrid exhaust steam recovery device is connected to a top inlet of the water tank, the top outlet of the hybrid exhaust steam recovery device is connected to the exhaust steam exhaust pipe via a non-condensable gas exhaust pipe, the inlet of the exhaust steam exhaust pipe is connected to the periodic blowdown expansion tank via a water seal valve, a pipeline between the water seal valve and the periodic blowdown expansion tank is connected to the exhaust steam inlet of the hybrid exhaust steam recovery device via the exhaust steam recovery pipe, and an exhaust steam recovery shut-off valve is provided on the exhaust steam recovery pipe. The system and method can safely and efficiently recover flash exhaust steam.

Description

Technical Field

[0001] The invention belongs to the field of exhaust steam condensate and waste heat recovery in thermal power plants, and relates to an exhaust steam condensate and waste heat recovery system and method in thermal power plants. Background Art

[0002] The regular blowdown expansion tank of a thermal power plant is mainly used to receive emergency water discharge from the steam drum, emergency water discharge from the deaerator, drainage from the continuous blowdown expansion tank, drainage from the sootblower and other boiler sewage. After the drainage enters the tank, it is immediately expanded and flash evaporated. The sewage is discharged through the lower drain port, and the flash steam is discharged from the exhaust steam exhaust pipe above the regular blowdown expansion tank.

[0003] Since the flash exhaust steam pressure in the periodic blowdown expansion tank is low, generally around 0.02MPa, and the enthalpy value is around 2600kJ / kg. The flash exhaust steam emission from the periodic blowdown expansion tank of a thermal power plant can reach 2 to 6 tons / hour. The traditional treatment method is to discharge the flash exhaust steam disorderly into the air through the drain pipe above the periodic blowdown expansion tank. The disorderly discharge of flash steam causes an increase in the water replenishment of the power plant, increases the cost of desalted water, and also causes a great waste of low-grade steam thermal energy, causing thermal pollution and visual pollution to the surrounding environment. In winter, the exhaust steam will condense on the nearby ground after being discharged to form an ice layer, which seriously affects the personal safety of production personnel. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a system and method for recovering exhaust steam condensate and waste heat from a thermal power plant, which can safely and efficiently recover flash exhaust steam.

[0005] To achieve the above-mentioned purpose, the exhaust steam condensate and waste heat recovery system of a thermal power plant described in the present invention comprises a low-temperature condensate pipe, a hybrid exhaust steam recovery device, a water tank, a non-condensable gas exhaust pipe, an exhaust steam exhaust pipe, a periodic sewage expansion tank, a water seal valve and an exhaust steam recovery pipe;

[0006] The outlet of the low-temperature condensate water pipe is connected with the cooling water inlet of the hybrid exhaust steam recovery device, the bottom outlet of the hybrid exhaust steam recovery device is connected with the top inlet of the water tank, the top outlet of the hybrid exhaust steam recovery device is connected with the exhaust steam exhaust pipe through the non-condensable gas exhaust pipe, the inlet of the exhaust steam exhaust pipe is connected with the periodic sewage expansion tank through the water seal valve, the pipeline between the water seal valve and the periodic sewage expansion tank is connected with the exhaust steam inlet of the hybrid exhaust steam recovery device through the exhaust steam recovery pipe, and a exhaust steam recovery shut-off valve is arranged on the exhaust steam recovery pipe.

[0007] A condensate regulating valve is provided on the low-temperature condensate pipe.

[0008] The outlet of the low-temperature condensate water pipe is connected with the water supply port of the water seal valve through a water seal water supply pipe, and a water supply valve is arranged on the water seal water supply pipe.

[0009] The sewage outlet of the water seal valve is connected with the water seal sewage pipe, and the sewage outlet of the water seal sewage pipe is provided with a sewage valve.

[0010] It also includes online water quality testing equipment, recycled water supply pipes, recycled water pumps and valve groups, water supply valves, boiler water supply systems, drainage valves and drainage systems;

[0011] The outlet of the water tank is connected to the inlet of the recovery water pump and valve group through the online water quality detection device and the recovery water supply pipe. The outlet of the recovery water pump and valve group is divided into two paths, one of which is connected to the boiler feed water system through the feed water valve, and the other is connected to the drainage system through the drain valve.

[0012] Pressure sensors, temperature sensors, flow sensors and water level sensors are installed on the low-temperature condensate water pipe and the water tank.

[0013] It also includes a controller; an online water quality detection device, a pressure sensor, a temperature sensor, a flow sensor and a water level sensor are connected to the input end of the controller, and the output end of the controller is connected to the condensate water volume regulating valve, a recovery water pump and valve group, a water supply valve and a drainage valve.

[0014] The method for recovering exhaust steam condensate and waste heat from a thermal power plant of the present invention comprises the following steps:

[0015] When the flash exhaust steam in the pipeline between the periodic blowdown expansion tank and the water seal valve is blocked by the water seal valve, the exhaustion stops, and the exhaust steam recovery shut-off valve is opened at this time, and the exhaust steam enters the hybrid exhaust steam recovery device through the exhaust steam recovery pipe;

[0016] The condensate output from the low-temperature condensate pipe enters the hybrid exhaust steam recovery device as cooling water, and then mixes with the exhaust steam in the hybrid exhaust steam recovery device in a spraying manner, so that the exhaust steam condenses into condensate, and then flows into the water tank by gravity.

[0017] When the system fails and cannot absorb flash exhaust steam, the pressure in the periodic blowdown expansion tank rises, and the flash exhaust steam will break through the water seal in the water seal valve and continue to be discharged from the exhaust steam exhaust pipe.

[0018] The present invention has the following beneficial effects:

[0019] The exhaust steam condensate and waste heat recovery system and method of the thermal power plant described in the present invention, when the flash exhaust steam in the pipeline between the periodic sewage expansion tank and the water seal valve is blocked by the water seal valve, the exhaust steam is stopped. At this time, the exhaust steam recovery shut-off valve is opened, and the exhaust steam enters the hybrid exhaust steam recovery device through the exhaust steam recovery pipe. Then, in the hybrid exhaust steam recovery device, low-temperature condensate water is used for spraying and cooling, so that the exhaust steam is condensed into condensate, thereby safely and efficiently recovering the flash exhaust steam, with a simple structure, convenient operation, and strong practicality. In addition, the exhaust steam recovery shut-off valve is provided on the exhaust steam recovery pipe of the present invention, which can ensure that it is isolated from the exhaust steam emptying pipe during system maintenance, and maintenance can be carried out without affecting the operation of the main engine.

[0020] Furthermore, when the system fails and cannot absorb flash exhaust steam, the pressure in the periodic blowdown expansion tank rises, and the flash exhaust steam breaks through the water seal in the water seal valve and continues to be discharged from the exhaust steam exhaust pipe, thereby ensuring the safety of the system and avoiding explosion accidents of the periodic blowdown expansion tank caused by the jamming of traditional manual electric valves and untimely action. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a system schematic diagram of the present invention.

[0022] Among them, 1 is a water seal valve, 2 is a hybrid exhaust steam recovery device, 3 is a water tank, 4 is a recovery water pump and valve group, 5 is a controller, 6 is a water seal water supply pipe, 7 is a water seal sewage pipe, 8 is a low-temperature condensate water pipe, 9 is a condensate water volume regulating valve, 10 is an exhaust steam recovery pipe, 11 is an exhaust steam recovery shut-off valve, 12 is a non-condensable gas exhaust pipe, 13 is a recovery water supply pipe, 14 is an online water quality detection device, 15 is a water supply valve, and 16 is a drainage valve. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments, and is not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0024] The accompanying drawings show schematic diagrams of structures according to embodiments disclosed in the present invention. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0025] refer to Figure 1 The exhaust steam condensate and waste heat recovery system of a thermal power plant of the present invention comprises a water seal valve 1, a hybrid exhaust steam recovery device 2, a water tank 3, a recovery water pump and a valve group 4, a controller 5, a water seal water supply pipe 6, a water seal sewage pipe 7, a low-temperature condensate water pipe 8, a condensate water amount regulating valve 9, an exhaust steam recovery pipe 10, an exhaust steam recovery shut-off valve 11, a non-condensable gas exhaust pipe 12, a recovery water supply pipe 13, an online water quality detection device 14, a water supply valve 15 and a drainage valve 16;

[0026] A condensate regulating valve 9 is provided on the low-temperature condensate water pipe 8. The outlet of the low-temperature condensate water pipe 8 is divided into two paths, one of which is connected to the water supply port of the water seal valve 1 through the water seal water supply pipe 6, and a water supply valve is provided on the water seal water supply pipe 6. The other is connected to the cooling water inlet of the hybrid exhaust steam recovery device 2. The bottom outlet of the hybrid exhaust steam recovery device 2 is connected to the top inlet of the water tank 3. The top outlet of the hybrid exhaust steam recovery device 2 is connected to the exhaust steam exhaust pipe through the non-condensable gas exhaust pipe 12. The inlet of the exhaust steam exhaust pipe is connected to the periodic sewage expansion tank through the water seal valve 1. The water seal valve 1 is connected to the periodic sewage expansion tank. The pipeline between the waste expansion tanks is connected to the exhaust steam inlet of the hybrid exhaust steam recovery device 2 through the exhaust steam recovery pipe 10, and the exhaust steam recovery pipe 10 is provided with an exhaust steam recovery shut-off valve 11. The sewage outlet of the water seal valve 1 is connected to the water seal sewage discharge pipe 7, and the water seal sewage discharge pipe 7 is provided with a sewage discharge valve. The outlet of the water tank 3 is connected to the inlet of the recovery water pump and the valve group 4 through the online water quality detection device 14 and the recovery water supply pipe 13. The outlet of the recovery water pump and the valve group 4 is divided into two routes, one of which is connected to the boiler feed water system through the water supply valve 15, and the other is connected to the drainage system through the drainage valve 16;

[0027] Pressure sensors, temperature sensors, flow sensors and water level sensors are installed on the low-temperature condensate water pipe 8 and the water tank 3. Among them, the online water quality detection device 14, the pressure sensor, the temperature sensor, the flow sensor and the water level sensor are connected to the input end of the controller 5, and the output end of the controller 5 is connected to the condensate water volume regulating valve 9, the recovery water pump and valve group 4, the water supply valve 15 and the drainage valve 16.

[0028] The method for recovering exhaust steam condensate and waste heat from a thermal power plant of the present invention comprises the following steps:

[0029] When the flash exhaust steam in the pipeline between the periodic blowdown expansion container and the water seal valve 1 is blocked by the water seal valve 1, the exhaustion stops, and the exhaust steam recovery shut-off valve 11 is opened at this time, and the exhaust steam enters the hybrid exhaust steam recovery device 2 through the exhaust steam recovery pipe 10;

[0030] The condensate outputted from the low-temperature condensate water pipe 8 is divided into two paths, one of which is used as make-up water to enter the water seal valve 1 to ensure that there is a water column of a certain height in the water seal valve 1, and the drain valve on the water seal drain pipe 7 is opened regularly to drain and clean the water seal valve 1, and the other is used as cooling water to enter the hybrid exhaust steam recovery device 2, and then mixed with the exhaust steam in the hybrid exhaust steam recovery device 2 in a spraying manner, so that the exhaust steam condenses into condensate, and then flows into the water tank 3 by gravity, wherein the non-condensable gas in the hybrid exhaust steam recovery device 2 enters the exhaust steam exhaust pipe through the non-condensable gas exhaust pipe 12;

[0031] The water output from the water tank 3 is tested by an online water quality testing device 14, and then passes through the recycled water supply pipe 13 and the recycled water pump and valve group 4. When the water quality is qualified, it enters the boiler feed water system, and when the water quality is unqualified, it is sent to the drainage system.

[0032] When the system fails and cannot absorb flash exhaust steam, the pressure in the periodic blowdown expansion tank rises slightly, and the flash exhaust steam will break through the water seal in the water seal valve 1 and continue to be discharged from the exhaust steam exhaust pipe to ensure the inherent safety of the system.

[0033] It should be noted that the present invention recovers exhaust steam through the hybrid exhaust steam recovery device 2, thereby eliminating the short difference in heat exchange, improving the efficiency of absorption and heat exchange, and also achieving a certain deoxidation effect. At the same time, the hybrid exhaust steam recovery device 2 is used to quickly absorb the exhaust steam entering the recovery device cavity, so that the resistance of exhaust steam circulation is further reduced, so that the flash exhaust steam with very low pressure can continuously enter the hybrid exhaust steam recovery device 2.

[0034] The hybrid exhaust steam recovery device 2 is arranged on the water tank 3, has a compact structure and is easy to arrange. The online water quality detection device 14 can analyze the water quality at the initial stage of system operation, and send the water into the boiler feed water system after determining that the water quality meets the boiler feed water quality requirements.

[0035] According to the average flash exhaust steam volume of the regular blowdown expansion tank of 2.5 tons / hour, the annual operation hours of the boiler of 4,000 hours, and the calorific value of standard coal of 29037 kJ / kg, the present invention is used to recover the condensed water and waste heat of the flash exhaust steam, and one unit can save about 790 tons of standard coal and recover about 10,000 tons of desalted water each year. According to the factory electricity price of 0.30 yuan / kW.h, the standard coal price of 800 yuan / ton, and the unit price of desalted water of 15 yuan / ton, the energy-saving benefit of recovery is about 690,000 yuan / year.

Claims

1. A system for recovering exhaust steam condensate and waste heat from a thermal power plant, characterized in that: It comprises a low-temperature condensate water pipe (8), a hybrid exhaust steam recovery device (2), a water tank (3), a non-condensable gas exhaust pipe (12), an exhaust steam exhaust pipe, a periodic sewage expansion container, a water seal valve (1) and an exhaust steam recovery pipe (10); The outlet of the low-temperature condensate water pipe (8) is connected to the cooling water inlet of the hybrid exhaust steam recovery device (2), the bottom outlet of the hybrid exhaust steam recovery device (2) is connected to the top inlet of the water tank (3), the top outlet of the hybrid exhaust steam recovery device (2) is connected to the exhaust steam exhaust pipe via the non-condensable gas exhaust pipe (12), the inlet of the exhaust steam exhaust pipe is connected to the periodic blowdown expansion tank via the water seal valve (1), the pipeline between the water seal valve (1) and the periodic blowdown expansion tank is connected to the exhaust steam inlet of the hybrid exhaust steam recovery device (2) via the exhaust steam recovery pipe (10), and the exhaust steam recovery pipe (10) is provided with an exhaust steam recovery shut-off valve (11); A condensate water quantity regulating valve (9) is provided on the low-temperature condensate water pipe (8); The outlet of the low-temperature condensate water pipe (8) is connected to the water supply port of the water seal valve (1) via the water seal water supply pipe (6), and the water seal water supply pipe (6) is provided with a water supply valve.

2. The exhaust steam condensate and waste heat recovery system of a thermal power plant according to claim 1, characterized in that: The sewage outlet of the water seal valve (1) is connected to the water seal sewage discharge pipe (7), and the sewage discharge valve is arranged on the water seal sewage discharge pipe (7).

3. The exhaust steam condensate and waste heat recovery system of a thermal power plant according to claim 1, characterized in that: It also includes an online water quality detection device (14), a recycled water supply pipe (13), a recycled water pump and valve group (4), a water supply valve (15), a boiler water supply system, a drainage valve (16) and a drainage system; The outlet of the water tank (3) is connected to the inlet of the recovery water pump and valve group (4) via the online water quality detection device (14) and the recovery water supply pipe (13). The outlet of the recovery water pump and valve group (4) is divided into two paths, one of which is connected to the boiler water supply system via the water supply valve (15), and the other is connected to the drainage system via the drainage valve (16).

4. The exhaust steam condensate and waste heat recovery system of a thermal power plant according to claim 3, characterized in that: A pressure sensor, a temperature sensor, a flow sensor and a water level sensor are arranged on the low-temperature condensation water pipe (8) and the water tank (3).

5. The exhaust steam condensate and waste heat recovery system of a thermal power plant according to claim 4, characterized in that: It also includes a controller (5); an online water quality detection device (14), a pressure sensor, a temperature sensor, a flow sensor and a water level sensor are connected to the input end of the controller (5); the output end of the controller (5) is connected to the condensate water volume regulating valve (9), the recovery water pump and valve group (4), the water supply valve (15) and the drainage valve (16).

6. A method for recovering exhaust steam condensate and waste heat from a thermal power plant, characterized in that: The exhaust steam condensate and waste heat recovery system of a thermal power plant according to claim 1 comprises the following steps: When the flash exhaust steam in the pipeline between the periodic blowdown expansion container and the water seal valve (1) is blocked by the water seal valve (1), the exhaustion stops, and the exhaust steam recovery shut-off valve (11) is opened at this time, and the exhaust steam enters the hybrid exhaust steam recovery device (2) through the exhaust steam recovery pipe (10); The condensed water outputted from the low-temperature condensed water pipe (8) enters the hybrid exhaust steam recovery device (2) as cooling water, and is then mixed with the exhaust steam in the hybrid exhaust steam recovery device (2) in a spraying manner, so that the exhaust steam condenses into condensed water, and then flows by gravity into the water tank (3).

7. The method for recovering exhaust steam condensate and waste heat from a thermal power plant according to claim 6, characterized in that: When the system fails and cannot absorb the flash exhaust steam, the pressure in the periodic blowdown expansion tank rises, and the flash exhaust steam will break through the water seal in the water seal valve (1) and continue to be discharged from the exhaust steam exhaust pipe.

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