Pump-free drain recovery system for power plants

Abstract

We provide a pump-free drain recovery system for power plants. [Solution] The system includes a drain recovery tank 1 with an air curtain 2 on top, a water collection pipe 3 connected to a water collection source and the drain recovery tank 1, respectively, and a condensation equipment and a suction pipe 4 connected to the drain recovery tank 1, wherein the air pressure within the condensation equipment is lower than atmospheric pressure, and the vertical height of the suction pipe 4 is higher than the height of the water column that can be pumped up at standard atmospheric pressure.

Description

[Technical field]

[0001] The present invention relates to the technical field of boiler equipment, and in particular to a pump-free drain recovery system for power plants. [Background technology]

[0002] In thermal power plants, some secondary reheat supercritical boilers are equipped with a collection tank. During the start-up phase of the boiler, the drain pump is started to discharge the drainage in the collection tank into the circulating water return pipe, and the drainage is collected after the water quality meets the requirements. During normal operation, if the water level of the drainage in the collection tank is too high, the drainage is collected into the condensation system through the drain pump.

[0003] However, this design has certain risks. After a period of operation, the piping from the drain pump outlet to the target position is long, so when the drain pump is started, the piping will shake violently, and the welds may break due to long-term start-up and stop. In addition, if the three outlet doors draining to the condensation system leak or open incorrectly, or if the drain pump is not stopped at the right time after starting, the vacuum level of the condenser may decrease, and in the worst case, it may cause abnormal conditions such as protection operation and unit tripping.

[0004] In view of the above, there is currently a need for a condensate recovery system that solves or partially solves the problems set forth above. Summary of the Invention [Means for solving the problem]

[0005] The object of the present invention is to provide a pump-free drain recovery system for power plants, which overcomes the drawbacks of the prior art and solves or partially solves the problem that pump-type drain recovery systems are prone to damage and malfunction.

[0006] The objective of the present invention may be achieved by the following technical solutions:

[0007] A pump-free drain recovery system for a power plant, comprising: A drain collection tank having an air curtain on the top; a water collection pipe connected to a water collection source and the drain recovery tank, respectively; a condensation device and a suction pipe connected to the drain recovery tank, The air pressure in the condensation facility is lower than atmospheric pressure, and the vertical height of the suction pipe is higher than the height of the water column that can be pumped up at standard atmospheric pressure.

[0008] As a preferred technical solution, the top of the drain recovery tank is further provided with an ultrasonic level sensor.

[0009] As a preferred technical solution, the end of the suction pipe close to the drain collection tank is 10 to 30 mm away from the bottom of the drain collection tank.

[0010] As a preferred technical solution, the rule for determining the vertical height of the suction pipe is as follows: The distance between the water level in the drain recovery tank and the end of the suction pipe close to the drain recovery tank is greater than a preset value.

[0011] As a preferred technical solution, the vertical height of the suction pipe is 10.5-13m.

[0012] As a preferred technical solution, the air pressure in the condensation equipment is 80-120 kPa.

[0013] As a preferred technical solution, said water collection source is an atmospheric expansion water collection tank.

[0014] As a preferred technical solution, the drain collection tank is connected to the ground via a bracket.

[0015] As a preferred technical solution, the suction pipe is connected to a spare opening of the condensation installation.

[0016] As a preferred technical solution, the condensation equipment includes a low back pressure condenser and a high back pressure condenser.

[0017] Compared with the prior art, the present invention has at least one of the following beneficial effects: (1) Achieve drain recovery without the need for a pump. In response to the problem that pump-type drain recovery systems are prone to damage and malfunction, this device provides a suction pipe connecting the condensation equipment and the drain recovery tank, and utilizes the pressure difference formed between atmospheric pressure and the air pressure inside the condensation equipment to achieve drain recovery from the power plant's reheat supercritical boiler without the need for a pump. (2) High safety. Based on the realization of drain recovery without pumps, in order to solve the problem that the water level in the drain recovery tank is too low and may affect the internal pressure of the condensation equipment, the present invention sets the vertical height of the suction pipe higher than the height of the water column that can be pumped up at standard atmospheric pressure, and sets the vertical height of the suction pipe based on the principle that the distance between the water level in the drain recovery tank and the end of the suction pipe close to the drain recovery tank is greater than a preset value, thereby maintaining a safe water level in the drain recovery tank, and based on this, an ultrasonic level sensor is added to monitor the liquid level. (3) Realize fully automatic drain return. Unlike the traditional solutions that have problems such as leakage or erroneous opening of the three outlet doors, and the inability to stop the drain pump in a timely manner after starting, this invention does not need to install valves or pumps, does not need to open the drain return valve to the condenser, does not affect the vacuum of the condenser, and can realize safe, reliable, and fully automatic drain return. (4) Easy to implement. The present invention does not require the installation of additional piping, and does not require the unit to be shut down during retrofitting work; the work can be carried out normally while the unit is in operation. (5) Energy saving and emission reduction effects are significant. On the one hand, the retrofit cost of this invention is low, and on the other hand, evaluations show that the recovered condensate can bring enormous economic and environmental benefits. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of a pump-free drain recovery system for a power plant according to an embodiment. [Explanation of symbols]

[0019] 1, drain recovery tank, 2, air curtain, 3, collection pipe, 4, suction pipe, 5, ultrasonic level sensor, 6, atmospheric expansion collection tank, 7, bracket, 8, spare opening, 9, low back pressure condenser, 10, high back pressure condenser, 11, spare pipe, 12, condensate pump pit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The technical solutions in the embodiments of the present invention are described below clearly and completely with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts are included in the scope of protection of the present invention.

[0021] In the description of the present invention, the orientations and positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside" and "outside" are based on the orientations and positional relationships shown in the drawings or the orientations and positional relationships in which the product of the present invention is usually placed when used. This is only for the purpose of explaining and simplifying the description of the present invention, and does not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. For example, "horizontal" only means that the direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, and it is acceptable to tilt slightly.

[0022] In consideration of the problems existing in the prior art described above, the present embodiment provides a pump-free drain recovery system for a power plant. Referring to FIG. 1, the system includes: The drain recovery tank 1 is provided in the condensate pump pit 12, and an air curtain 2, a reserve pipe 11, an ultrasonic level sensor 5, a water collection pipe 3, and a water suction pipe 4 are provided at the top of the drain recovery tank 1. The water collection pipe 3 is connected to the water collection source and the drain recovery tank 1, respectively, and the water suction pipe 4 is connected to the reserve opening 8 of the condensation equipment and the drain recovery tank 1, respectively. The air curtain 2 communicates the inside and outside of the drain recovery box 1, and ensures the balance of the air pressure inside and outside. The reserve pipe 11 is used for maintenance. The ultrasonic level sensor 5 is used to monitor whether the liquid level inside is within a safe range or not, and to issue an alarm when the liquid level is too low or too high.

[0023] In this embodiment, the water collection source is an atmospheric expansion water collection tank 6, and the condensation equipment includes a low back pressure condenser 9 and a high back pressure condenser 10. The water collection source and the condensation equipment may be replaced with other devices as long as they do not conflict with each other.

[0024] In the system, the air pressure in the condensation facility is lower than atmospheric pressure, and the vertical height of the suction pipe 4 is higher than the height of the water column that can be pumped up at standard atmospheric pressure. The distance between the water level in the drain recovery tank 1 and one end of the suction pipe 4 close to the drain recovery tank 1 is greater than a preset value. Preferably, the preset value is 1 meter, the one end of the suction pipe 4 close to the drain recovery tank 1 is 10-30 mm away from the bottom of the drain recovery tank 1, the vertical height of the suction pipe 4 is 10.5-13 m, and the air pressure in the condensation facility is 80-120 kPa.

[0025] In a specific embodiment, the reference height of the ground where the steam turbine is located is 0 meters, and a stainless steel pipe with a diameter of 200 mm is connected as a water collection pipe 3 to the opening of the drain pipe at an elevation of about 6.0 meters before the drainage water enters the condenser, and a condensate pump pit with a diameter of about 3 meters, a height of about 4 meters (0 meters to 4 meters below the steam turbine), and a total volume of about 28 m 3 The drain recovery tank 1 is installed, and a bracket 7 is attached to the bottom as a base to prevent rust and corrosion of the water tank. An ultrasonic radar level gauge is attached to the top of the water tank, and a stainless steel suction pipe with a diameter of 50 mm is connected as a suction pipe 4 to the spare opening of the condenser at an altitude of 7.8 meters and inserted so that it is 20 mm away from the bottom of the water tank. The cumulative height of the suction pipe is estimated to be about 11.8 meters, and the drainage water from the drain recovery tank is sucked in using the vacuum of the condenser.

[0026] If the drainage is ideally pure water, a water column of 10.32 meters can be pumped up at 1 standard atmospheric pressure. Based on this principle, if the vacuum of the generator set condenser is calculated as 92 kPa in summer and 99 kPa in winter, the water level in the water tank can be maintained at least 2.3 meters in summer and at least 1.5 meters in winter, with a safety distance of more than 1 meter being ensured from the bottom water intake.

[0027] The atmospheric expansion collecting tank 6 is located on the boiler platform at an elevation of 4.2 meters, has a diameter of 2.5 meters, a total length of approximately 6.9 meters, and a design volume of 31 m 3There is a 1000mm water level gauge on the center line of the cylinder. According to past trend analysis, at an average load of 520MW, the water level rises from 0 to about 1100mm every 5 hours. Based on this, about 17 tons of desalinated water is discharged into the drain of the unit every 5 hours. It is about 3.4 tons per hour. Calculated according to the designed water supply of 1293t / h at an average annual load of 520MW, the water supply rate of the unit can be reduced by about 0.26% by recovering this part of the drainage. These two units can save the water supply of 4,896 tons of desalinated water every month. Currently, the production cost of desalinated water includes the cost of medicines such as resin, acid-alkali solution, electricity consumption, steam consumption, equipment depreciation, etc., and is about 19 yuan per ton. Based on this, it can save 87,324 yuan per month and about 1.05 million yuan per year. At the same time, it can reduce a large amount of carbon emissions. Recovering this part of the drainage will bring great economic and environmental benefits.

[0028] This system has the following advantages: There is no need to lay piping from the collection tank to the drain tank, so the originally designed piping can be used, and steel consumption is low, with low modification costs. The vacuum in the condenser is used to suck the drainage water in the drain tank, making the operation secure, safe and reliable. There is no need to open the recovery valve from the drainage water to the condenser, so the vacuum in the condenser is not affected, resulting in a large economic return and saving approximately 1.05 million RMB per year. There is no need to shut down the unit during construction, so normal construction can be carried out while the unit is running.

[0029] The above description is merely a specific embodiment of the present invention, and the scope of protection of the present invention is not limited thereto, and those skilled in the art can easily think of various equivalent modifications and replacements within the technical scope disclosed in the present invention, and these modifications and replacements should also be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be subject to the scope of protection of the claims.

Claims

1. A pump-free drain recovery system for a power plant, comprising: A drain recovery tank (1) having an air curtain (2) on the top thereof; A water collection pipe (3) connected to a water collection source and the drain recovery tank (1), respectively; The system includes a condensation system and a suction pipe (4) connected to the drain recovery tank (1), A drain recovery system for a power plant that does not require a pump, characterized in that the air pressure in the condensation equipment is lower than atmospheric pressure, and the vertical height of the suction pipe (4) is higher than the height of a water column that can be pumped up at standard atmospheric pressure.

2. The pump-free drain recovery system for a power plant according to claim 1, characterized in that an ultrasonic level sensor (5) is further provided at the top of the drain recovery tank (1).

3. The drain recovery system for a power plant not requiring a pump according to claim 1, characterized in that an end of the suction pipe (4) close to the drain recovery tank (1) is 10 to 30 mm away from a bottom of the drain recovery tank (1).

4. The rules for determining the vertical height of the suction pipe (4) are as follows:

2. The drain recovery system for a power plant without a pump according to claim 1, characterized in that a distance between a water level in the drain recovery tank (1) and an end of the suction pipe (4) close to the drain recovery tank (1) is greater than a preset value.

5. The pump-free drain recovery system for power plants according to claim 1, characterized in that the vertical height of the suction pipe (4) is 10.5 to 13 m.

6. The pump-free drain recovery system for power plants according to claim 1, characterized in that the air pressure in the condensation facility is 80 to 120 kPa.

7. The pump-free drain recovery system for a power plant according to claim 1, characterized in that the water collection source is an atmospheric expansion water collection tank (6).

8. The pump-free drain recovery system for a power plant according to claim 1, characterized in that the drain recovery tank (1) is connected to the ground via a bracket (7).

9. 2. The pump-free drain recovery system for a power plant according to claim 1, characterized in that the suction pipe (4) is connected to a reserve opening (8) of the condensation installation.

10. The pump-free drain recovery system for a power plant according to claim 1, characterized in that the condensation installation comprises a low back pressure condenser (9) and a high back pressure condenser (10).

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