Pump-free dewatering recovery system for power plant

Abstract

Pump-free dewatering recovery system for power plant, characterized in that the dewatering recovery system comprises: a drainage collection tank (1), wherein a weather door (2) is provided on the top of the drainage collection tank; a water collection pipe (3) connected to a water collection source and the drainage collection tank (1), respectively; and a water suction pipe (4) connected to the condensing device and the drainage collection tank (1), respectively, and wherein the gas pressure in the condensation device is lower than atmospheric pressure and the vertical height of the water suction pipe (4) is higher than the height of the water column pumped up by normal atmospheric pressure.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of boiler equipment and in particular to a pump-free dewatering recovery system for power plants. STATE OF THE ART

[0002] In thermal power plants, some supercritical boilers with dual reheating are equipped with water collection tanks. During boiler start-up, the drainage pump is started to drain the drainage in the water collection tank into the circulating water return line. Drainage is restored when the water quality has met requirements. If the drainage level in the water collection tank is too high during normal operation, the drainage is returned to the condensing system via the drain pump.

[0003] However, this design conceals certain risks. After a certain period of operation, it became apparent that the pipeline from the drainage pump outlet to the destination was long. Starting the drainage pump would cause severe vibrations to the pipeline, and prolonged starting and stopping could damage the weld. Furthermore, leaks or accidental opening of the three drainage outlet doors to the condensing system, or failure to stop the drainage pump in time after starting, could lead to a drop in the condenser vacuum. In severe cases, this could lead to abnormal conditions such as protective measures and the shutdown of the machine assembly.

[0004] In summary, there is currently a lack of a drainage recovery system to solve or partially solve the above-mentioned problems. CONTENT OF THE PRESENT UTILITY MODEL

[0005] The purpose of the present utility model is to overcome the deficiencies of the above-mentioned prior art and to provide a pump-free dewatering recovery system for power plant to solve or partially solve the problem of easy damage and malfunction of the dewatering recovery system with a pump.

[0006] The purpose of the present utility model can be achieved by the following technical solutions: The present utility model proposes a pump-free dewatering recovery system for power plant, comprising: a drainage collection tank, wherein a weather door is provided on the top of the drainage collection tank; a water collection pipe connected to a water collection source and the drainage collection tank, respectively; and a water suction pipe connected to the condensing device and the drainage collection tank, respectively, and wherein the gas pressure in the condensing device is lower than atmospheric pressure and the vertical height of the water suction pipe is higher than the height of the water column pumped up by normal atmospheric pressure.

[0007] In a preferred technical solution, the top of the dewatering recovery tank further comprises an ultrasonic liquid level sensor.

[0008] In a preferred technical solution, the end of the water suction pipe near the drainage collection tank is 10-30 mm from the bottom of the drainage collection tank.

[0009] In a preferred technical solution, the vertical height of the water suction pipe is determined as follows: The distance between the water level in the drainage collection tank and the end of the water suction pipe near the drainage collection tank is greater than a preset value.

[0010] In a preferred technical solution, the vertical height of the water suction pipe is 10.5-13 m.

[0011] In a preferred technical solution, the gas pressure in the condensation device is 80-120 kPa.

[0012] In a preferred technical solution, the water collection source is a water collection box of the atmospheric expansion vessel.

[0013] In a preferred technical solution, the dewatering recovery tank is connected to the ground via a bracket.

[0014] In a preferred technical solution, the water suction pipe is connected to the reserved opening of the condensing device.

[0015] In a preferred technical solution, the condensation device comprises a low-pressure condenser and a high-pressure condenser.

[0016] Compared to the prior art, the present utility model has at least one of the following advantageous effects: (1) Pump-free dehydration recovery is achieved: In order to solve the problem of easy damage and malfunction of dehydration recovery systems with pumps, the present utility model proposes a water suction pipe connecting the condensing device and the dehydration recovery tank, and enables the dehydration recovery of the supercritical reheat boiler in a power plant without a pump by utilizing the pressure difference formed by the atmospheric pressure and the gas pressure in the condensing device. (2) High safety: Based on the realization of pump-free dewatering recovery, the problem that the water level in the dewatering recovery tank may be too low, thereby affecting the internal pressure of the condensing device, is solved. Therefore, in the present utility model, the vertical height of the water suction pipe is set higher than the height of the water column that can be pumped up at normal atmospheric pressure. The vertical height of the water suction pipe is adjusted to maintain a safe water level in the dewatering recovery tank. On this basis, an ultrasonic level sensor is additionally provided to monitor the liquid level. (3) Fully automatic drainage recirculation is achieved: Unlike existing designs that involve leaks or accidental opening of the three outlet doors, or failure to stop the drainage pump in a timely manner after starting, the present utility model eliminates the need for valves or pump bodies, and eliminates the need to open the drainage-to-condenser recovery valve. This ensures that the condenser vacuum is not compromised, is safe, and enables fully automatic drainage recirculation. (4) Ease of implementation: The present utility model does not require the installation of additional piping, and the plant does not need to be shut down during the conversion. Normal construction work can be carried out while the unit is running. (5) Significant benefits in terms of energy savings and emission reduction: On the one hand, the modification costs of the present utility model are low, on the other hand, according to the evaluation, the recovered drainage can bring enormous economic and ecological benefits. SHORT DESCRIPTION OF THE DRAWING Fig. 1 is a schematic diagram of a pumpless dewatering recovery system for power plant in one embodiment.

[0017] Where: 1. Dewatering recovery tank, 2. Weather door, 3. Water collecting pipe, 4. Water suction pipe, 5. Ultrasonic liquid level sensor, 6. Atmospheric expansion vessel water collecting box, 7. Bracket, 8. Reserved port, 9. Low back pressure condenser, 10. High back pressure condenser, 11. Reserved pipe, 12. Condensate pump pit. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present utility model are described clearly and completely below in conjunction with the drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model and not all of them. Based on the embodiments of the present utility model, all other embodiments that can be achieved by a person of ordinary skill in the art without any creative effort should fall within the scope of the present utility model.

[0019] When describing the present utility model, it should be noted that the terms "center," "top," "bottom," "left," "right," "vertical," "horizontal," "inside," and "outside," etc., indicate directions or positional relationships based on the directions or positional relationships shown in the attached drawings, or the directions or positional relationships in which the utility model product is commonly placed during use. They are used only for the practical description of the present utility model and to simplify the description. They do not imply that the said device or element must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be construed as limiting the present utility model. For example, "horizontal" simply means that the direction is horizontal rather than "vertical."This does not mean that the structure has to be completely horizontal, but it can be slightly inclined.

[0020] In view of the problems existing in the above-mentioned prior art, the embodiment provides a pump-free dewatering recovery system for power plants. Referring to Fig. 1 the system includes: a dewatering recovery tank 1 provided in the condensate pump pit 12, wherein a weather door 2, a reserved pipe 11, an ultrasonic liquid level sensor 5, a water collection pipe 3, and a water suction pipe 4 are provided at the top of the dewatering recovery tank 1, and wherein the water collection pipe 3 is connected to the water collection source and the dewatering recovery tank 1, respectively, and wherein the water suction pipe 4 is connected to the reserved port 8 of the condensing device and the dewatering recovery tank 1, respectively. The weather door 2 connects the inside of the dewatering recovery tank 1 to the outside to ensure the balance of the internal and external gas pressures. The reserved pipe 11 is used for maintenance work.The ultrasonic liquid level sensor 5 is intended to monitor whether the internal liquid level is within a safe range and to trigger an alarm if the liquid level is too low or too high.

[0021] In this embodiment, the water collection source is the water collection box 6 of the atmospheric expansion vessel, and the condensing device includes a low back pressure condenser 9 and a high back pressure condenser 10. Note that the water collection source and the condensing device can be replaced by other devices without conflict.

[0022] In the system, the gas pressure in the condensing device is lower than atmospheric pressure, and the vertical height of the water suction pipe 4 is higher than the height of the water column that can be pumped up by normal atmospheric pressure. The distance between the water level in the dewatering collection tank 1 and the end of the water suction pipe 4 near the dewatering collection tank 1 is greater than a preset value. Preferably, the preset value is 1 meter, and the end of the water suction pipe 4 near the dewatering collection tank 1 is 10-30 mm away from the bottom of the dewatering collection tank 1. The vertical height of the water suction pipe 4 is 10.5-13 m, and the gas pressure in the condensing device is 80-120 kPa.

[0023] In a specific embodiment, the reference elevation 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 to the opening of the drain pipe at a height of about 6.0 meters before the drainage enters the condenser, and the stainless steel pipe serves as a water collection pipe 3. In the condensate pump pit, a drainage recovery tank 1 with a diameter of about 3 meters and a height of about 4 meters (4 meters from 0 meters below the steam turbine) and a total volume of about 28 m 3mounted, and a bracket 7 is mounted at the bottom as a base to protect the water tank from rust and corrosion. An ultrasonic radar level sensor is mounted at the top of the water tank, and a 50 mm diameter stainless steel water suction pipe is connected as the water suction pipe 4 to the designated opening at the condenser height of 7.8 meters, which is inserted into the water tank 20 mm away from the bottom. From this, it can be concluded that the total height of the water suction pipe is approximately 11.8 meters, so the condenser vacuum is used to suck the drainage into the drainage recovery tank.

[0024] If the drainage consists of ideally pure water, a standard atmospheric pressure can draw in a water column of 10.32 meters. Based on this principle, and corresponding to the generator set's condenser vacuum of 92 kPa in summer and 99 kPa in winter, the water level in the water tank can be maintained at a minimum of 2.3 meters in summer and 1.5 meters in winter, with a safety distance of more than 1 meter from the lower water inlet.

[0025] The atmospheric expansion water collection tank 6 is located on the boiler platform at a height of 4.2 meters, with a diameter of 2.5 meters, a total length of about 6.9 meters, a planned volume of 31 m 3and a 1000 mm water level gauge on the cylinder centerline. According to historical trend analysis, at an average load of 520 MW, the water level rises from 0 to about 1100 mm every 5 hours. Based on this calculation, about 17 tons of desalinated water are discharged into the unit's dewatering tank every 5 hours. Approximately 3.4 tons per hour is calculated based on the designed water supply flow of 1293 t / h for an average annual load of 520 MW. By recycling this amount from the dewatering, the water replenishment rate of the unit can be reduced by about 0.26%. Two units can save 4,896 tons of desalinated water per month. Currently, the cost of producing desalinated water, which includes the cost of resins, acid and alkali solutions, power consumption, steam consumption, device depreciation, etc., is about 19 CNY / ton. Based on this calculation, 87324 CNY per month and approximately 1.05 million CNY per year can be saved. At the same time, large amounts of carbon emissions can be avoided. Recycling this amount of desalinated water will bring enormous economic and environmental benefits.

[0026] This system has the following advantages: There is no need to lay pipelines from the water collection tank to the drainage tank. The originally designed pipelines can be used, and steel consumption is low and conversion costs are low. The condenser vacuum is used to suck the drainage into the drainage tank, and the operation is reliable. It is safe and reliable, and there is no need to open the recovery valve from the drainage to the condenser, which does not affect the condenser vacuum. The economic return is considerable, and approximately 1.05 million RMB can be saved annually. During construction, the plant does not need to be shut down, and normal construction work can be carried out while the plant is running.

[0027] The above description merely presents specific embodiments of the present utility model. However, the scope of the present utility model is not limited thereto. Anyone familiar with the technical field can easily imagine various equivalent modifications or replacements within the technical scope disclosed by the present utility model, and these modifications or replacements should fall within the scope of the present utility model. Therefore, the scope of the present utility model should be based on the scope of the claims.

Claims

[1] Pump-free dewatering recovery system for power plant, characterized by that the drainage recovery system includes: a drainage collection tank (1), wherein a weather door (2) is provided on the top of the drainage collection tank; a water collection pipe (3) connected to a water collection source and the drainage collection tank (1), respectively; and a water suction pipe (4) connected to the condensing device and the drainage collection tank (1), respectively, and wherein the gas pressure in the condensation device is lower than atmospheric pressure and the vertical height of the water suction pipe (4) is higher than the height of the water column pumped up by normal atmospheric pressure. [2] Pump-free dewatering recovery system for power plant according to claim 1, characterized bythat the top of the dewatering recovery tank (1) further comprises an ultrasonic liquid level sensor (5). [3] Pump-free dewatering recovery system for power plant according to claim 1, characterized by that the end of the water suction pipe (4) near the drainage collection tank (1) is 10-30 mm from the bottom of the drainage collection tank 1. [4] Pump-free dewatering recovery system for power plant according to claim 1, characterized by that the vertical height of the water suction pipe (4) is determined as follows: The distance between the water level in the drainage collection tank (1) and the end of the water suction pipe (4) near the drainage collection tank (1) is greater than a preset value. [5] Pump-free dewatering recovery system for power plant according to claim 1, characterized by that the vertical height of the water suction pipe (4) is 10.5-13 m. [6] Pump-free dewatering recovery system for power plant according to claim 1, characterized by that the gas pressure in the condensation device is 80-120 kPa. [7] Pump-free dewatering recovery system for power plant according to claim 1, characterized by that the water collection source is a water collection box (6) of the atmospheric expansion vessel. [8] Pump-free dewatering recovery system for power plant according to claim 1, characterized by that the drainage recovery tank (1) is connected to the ground via a bracket (7). [9] Pump-free dewatering recovery system for power plant according to claim 1, characterized by that the water suction pipe (4) is connected to the reserved opening (8) of the condensation device. [10] Pump-free dewatering recovery system for power plant according to claim 1, characterized bythat the condensation device comprises a low back pressure condenser (9) and a high back pressure condenser (10).

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