A method for recovering lubricating oil of a turbine exhaust fume fan on line

Abstract

The application discloses a kind of online recovery method of steam turbine oil exhaust fan lubricating oil, including oil discharge pipeline (1) one end is connected with oil discharge port (2), the other end is communicated with negative pressure area in lubricating oil smoke exhaust system (3);Manual isolation valve (4) is located on oil discharge pipeline (1);U type liquid seal elbow pipe (12) is located on oil discharge pipeline (1) and is located downstream of manual isolation valve (4), bottom forms liquid seal area;The separated lubricating oil flows out from the oil discharge port (2) of oil fume purification device (5) under the action of gravity, in turn flows through first pipeline (11), open state manual ball valve (4), and U type liquid seal elbow pipe (12), finally, under the auxiliary of negative pressure suction of lubricating oil smoke exhaust system (3), drop or flow into the oil space of smoke main pipe or main oil tank.The application has the advantages of effectively preventing negative pressure gas backflow, ensuring oil fume separation effect and system stability, improving recovery efficiency, realizing online, automatic, closed recovery of lubricating oil.

Description

Technical Field

[0001] This invention belongs to the technical field of steam turbine auxiliary equipment, and particularly relates to an online method for recovering lubricating oil from a steam turbine exhaust fan. Background Technology

[0002] During operation, steam turbines generate a mixture of oil fumes containing lubricating oil mist, water vapor, and air due to high temperatures and mechanical movement in components such as the bearing housing. To maintain a slight negative pressure inside the bearing housing and purify the exhaust gases, exhaust fans and associated oil fume purification devices are typically installed. These devices effectively separate liquid lubricating oil droplets from the oil fume mixture.

[0003] Currently, the main methods for treating lubricating oil separated from fume purification devices are as follows: One method is external collection, which involves manually collecting oil periodically using a hose or container through the drain port at the bottom of the purification device. This method not only requires manpower for regular operation, increasing maintenance workload, but also is prone to leakage during collection and transportation, resulting in waste of lubricating oil and pollution of the site environment.

[0004] Another approach is simple reflux, which attempts to directly pipe the separated lubricating oil back into the lubrication system. However, this simple method has several insurmountable drawbacks: First, there is a large negative pressure near the intake of the exhaust fan. If the recovery pipe is directly connected, the gas will be drawn back into the fume purification device from the recovery pipe. This will seriously interfere with the flow field inside the purification device, damage its fume separation effect, and even affect the stability of the negative pressure in the bearing box. Secondly, the amount of oil separated is usually small and intermittent. If the pipeline design is not reasonable, it is easy for the oil flow to stagnate when relying solely on gravity backflow, which will eventually form sludge that clogs the pipeline. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of oil waste, environmental pollution, gas backflow, and blocked oil recovery circuits in existing lubricating oil recovery methods. It provides an online lubricating oil recovery method for turbine exhaust fans, which can effectively prevent negative pressure gas backflow, ensure oil fume separation effect and system stability, improve recovery efficiency, facilitate later maintenance, reduce safety hazards, and realize online, automatic, and closed-loop recovery of lubricating oil.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for online recovery of lubricating oil in a steam turbine exhaust fan includes: An oil drain pipe, one end of which is connected to an oil drain port, and the other end of which is connected to the negative pressure area in the lubricating oil exhaust system of the steam turbine; A manual isolation valve is installed on the oil drain line; And a U-shaped liquid seal bend is provided on the oil drain pipe and located downstream of the manual isolation valve. Its bottom forms a liquid seal area, which effectively prevents the gas in the exhaust system from flowing back into the oil drain pipe. The separated lubricating oil flows out from the oil outlet of the fume purification device under the action of gravity, and flows through the first section of pipe, the open manual ball valve, and the U-shaped bend in sequence. Finally, with the assistance of negative pressure suction of the lubricating oil exhaust system, it drips or flows into the oil space of the exhaust header or the main oil tank, realizing the online recovery of lubricating oil.

[0007] Furthermore, the liquid seal height formed by the U-shaped liquid seal bend is greater than the sum of the maximum design negative pressure value and the safety margin at the air intake of the lubricating oil exhaust system. In this design, the liquid seal formed by the lubricating oil accumulated in the U-shaped bend can reliably resist and balance the negative pressure suction effect from the lubricating oil exhaust system, thereby effectively preventing gas from being drawn back into the oil drain pipe and the oil fume purification device, ensuring that the separation efficiency of the oil fume purification device is not disturbed.

[0008] Furthermore, the maximum design negative pressure value at the air intake of the lubricating oil exhaust system is converted into the liquid column height for calculation, with a safety margin of 50~150mm water column.

[0009] Furthermore, the oil drain line maintains a continuous downward slope along the flow direction of the lubricating oil. This design utilizes gravity as the primary driving force, ensuring that even trace amounts of lubricating oil separated from the fume purification device can flow smoothly within the pipe, avoiding the risk of oil accumulation and blockage caused by excessively low flow rates or localized high points in the pipe.

[0010] Furthermore, the slope ranges from 1% to 5%, meaning a drop of 10mm to 50mm per meter of pipe. This slope range is optimized to ensure sufficient flow dynamics and prevent oil stagnation, while avoiding installation difficulties or excessive vertical space occupation due to an excessively large slope, thus achieving a balance between reliability and engineering feasibility.

[0011] Furthermore, the oil discharge pipeline includes a first pipe, a U-shaped liquid seal bend, and a second pipe connected in sequence, all of which are made of oil-resistant and temperature-resistant metal pipes or high-performance plastic pipes. These materials ensure stable operation of the recovery pipeline in environments containing lubricating oil and at certain temperatures, exhibiting good corrosion resistance and mechanical strength, thus ensuring the reliability and service life of the entire recovery system.

[0012] Furthermore, the U-shaped liquid seal bend is located in a position with a higher ambient temperature, or insulation measures are taken for the U-shaped liquid seal bend, or a heat tracing device is installed at the U-shaped liquid seal bend. These measures aim to prevent the lubricating oil from becoming clogged at the accumulation point of the U-shaped liquid seal bend due to increased viscosity or solidification when the ambient temperature is low, ensuring that the recovery passage is unobstructed in all seasons, and is particularly suitable for units operating in cold regions or during winter.

[0013] Furthermore, the manual isolation valve is either a manual ball valve or a manual gate valve. These two types of valves are characterized by simple structure, convenient operation, and reliable sealing, enabling them to quickly and effectively cut off the oil circuit during maintenance of fume purification devices or oil drain pipelines, thus providing safety assurance for maintenance work.

[0014] Furthermore, the connection point between the oil drain pipe and the lubricating oil exhaust system is located on the exhaust header between the exhaust port of the main lubricating oil tank and the exhaust fan inlet. This location has a stable negative pressure, and the connection point is situated at the top or upper side of the exhaust header. By connecting the recovered lubricating oil from the top of the exhaust header, it can smoothly enter the header by dripping or flowing down the pipe wall, ultimately converging into the main oil tank. This avoids liquid accumulation at the connection point and ensures a clear recovery path.

[0015] Compared with the prior art, the advantages of the technical solution of the present invention are as follows: (1) The present invention uses a U-shaped liquid seal bend with sufficient liquid seal height to form a fluid isolation by the accumulated lubricating oil itself, which effectively prevents the negative pressure gas in the lubricating oil exhaust system from flowing back into the oil fume purification device, thereby ensuring the oil fume separation effect and the stability of the micro negative pressure in the turbine bearing box, and avoiding the situation where the separation effect is poor due to gas backflow. (2) The present invention realizes the online, automatic and closed-loop recovery of lubricating oil separated from the fume purification device without any manual intervention, thereby reducing the operation and maintenance costs and the labor intensity of maintenance personnel; (3) By setting the entire oil drain line to a continuous downward slope and supplementing it with anti-clogging measures, this invention ensures that even a small amount of intermittently generated lubricating oil can flow smoothly by gravity, thus avoiding pipe blockage. The system has no rotating parts and is highly reliable. (4) The lubricating oil recovered by this invention is directly returned to the lubricating oil system for recycling, avoiding the waste of oil and eliminating the leakage and waste oil disposal problems that may be caused by manual external collection. It realizes the closed-loop recycling of lubricating oil and has economic and environmental benefits. (5) The present invention has a simple structure and is easy to maintain. The overall layout consists of only conventional components such as pipes, valves and U-bends, and the modification cost is low. The manual isolation valve can easily cut off the oil circuit when needed, providing safety and convenience for inspection and maintenance. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the online lubricating oil recovery structure for the turbine exhaust fan of the present invention. Detailed Implementation Example

[0017] To make the present invention clearer, the following description, in conjunction with the accompanying drawings, further illustrates a method for online recovery of lubricating oil in a steam turbine exhaust fan. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] See Figure 1 A method for online recovery of lubricating oil in a steam turbine exhaust fan, comprising: At the oil outlet 2 at the bottom of the fume purification device 5, where the lubricating oil is separated, a section of stainless steel first pipe 11, DN15 or DN20, is welded or flanged to be connected. Install a DN15 or DN20 manual ball isolation valve 4 on the first pipe 11, which is 200-300mm away from the oil drain port; Downstream of the manual isolation valve 4 is a U-shaped stainless steel bend, namely the U-shaped liquid seal bend 12. The depth of the U-shaped bend, i.e., the center distance between the two vertical sections, is calculated based on the maximum design negative pressure of the lubricating oil exhaust system 3, for example, -500Pa: a negative pressure of 500Pa is equivalent to 51mm of water column. Considering a safety margin, the liquid seal height L is set to 100mm. Therefore, the lowest point of the bottom of the U-shaped bend should be at least 100mm below the inlet / outlet centerline.

[0019] The outlet end of the U-shaped liquid seal bend 12 is connected to a second stainless steel pipe 13, DN15 or DN20.

[0020] The pipeline is laid with a downward slope of no less than 2%, i.e., a drop of 20mm per meter. Finally, an opening is made at the top or side of the lubricating oil exhaust header, and the pipeline is inserted and welded or flanged to the header to form a connection point. Ensure that the insertion port is smooth and located in the negative pressure area of ​​the header.

[0021] During installation, ensure that the slope of the entire pipeline from drain port 2 to the connection point is continuous and without upward bends. The handle of the manual isolation valve 4 should be located in an easily accessible position on the operating platform.

[0022] During system operation, the lubricating oil separated from the fume purification device 5 flows into the drain pipe 1 through the drain port 2 under gravity. The lubricating oil first flows through the first pipe 11, then through the normally open manual isolation valve 4. Next, the lubricating oil enters the U-shaped liquid seal bend 12. Due to the special shape of the U-shaped liquid seal bend 12, the lubricating oil first fills its bottom until the liquid level exceeds the height of its outlet end, forming a liquid seal with a specific height. Afterward, newly flowing lubricating oil displaces an equal amount of lubricating oil from the U-shaped liquid seal bend 12, causing it to overflow from the outlet end.

[0023] The overflowing lubricating oil continues to flow under gravity through the subsequent second pipe 13, eventually reaching the connection point with the lubricating oil exhaust system 3. At the connection point, the lubricating oil drips or flows into the exhaust header, thus being reintegrated into the entire lubricating oil circulation system 3 of the turbine, achieving online recovery.

[0024] The arrangement in this embodiment combines hydrostatics and gravity flow. On one hand, the hydrostatic pressure generated by the weight of the liquid seal formed in the U-shaped liquid seal bend 12 effectively counteracts and isolates the negative pressure from inside the lubricating oil exhaust system 3. Although this negative pressure helps to "suck" away the oil droplets at the outlet of the U-shaped liquid seal bend 12, its suction force is insufficient to completely dry all the oil stored in the U-shaped liquid seal bend 12, i.e., it cannot break the liquid seal. This fundamentally prevents gas from flowing back from the lubricating oil exhaust system 3 into the oil fume purification device, ensuring the stability of the internal pressure of the oil fume purification device 5 and its separation efficiency.

[0025] The method of this invention requires no machine shutdown and automatically separates and recovers lubricating oil from exhaust fumes, with a recovery rate of >90%. It is simple to design, compatible with existing exhaust systems, and easy to modify.

[0026] Direct economic benefits: Steel plants' self-owned generator sets consume an average of about 30 tons of oil per year. The market price of 46# turbine oil is 12,000 yuan per ton. Calculated based on a lubricating oil slippage loss of 1.5%, 12,000 * 30 * 1.5% = 5,400 yuan. Coal-fired power plant units consume an average of about 90 tons of oil per year per 300,000 kW unit. Calculated based on a lubricating oil slippage loss of 1.5%, and with over 1,200 units of 300,000 kW and above nationwide, 12,000 * 90 * 1.5% * 1,200 = 1,944,000 yuan.

[0027] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for online recovery of lubricating oil in a steam turbine exhaust fan, characterized in that: Oil drain pipe (1), one end of which is connected to oil drain port (2), and the other end is connected to the negative pressure area in the lubricating oil exhaust system (3) of the steam turbine; A manual isolation valve (4) is installed on the oil drain line (1); And a U-shaped liquid seal bend (12), which is located on the oil drain line (1) and downstream of the manual isolation valve (4), with a liquid seal area formed at its bottom; The separated lubricating oil flows out from the oil outlet (2) of the oil fume purification device (5) under the action of gravity, and flows through the first pipe (11) of the oil drain pipe (1), the open manual ball valve (4), and the U-shaped liquid seal bend (12) in sequence. Finally, with the assistance of the negative pressure suction of the lubricating oil exhaust system (3), it drips or flows into the oil space of the exhaust header or the main oil tank.

2. The method for online recovery of lubricating oil in a steam turbine exhaust fan according to claim 1, characterized in that: The liquid seal height formed by the U-shaped liquid seal bend (12) is greater than the sum of the maximum design negative pressure value and the safety margin at the air intake of the lubricating oil exhaust system (3).

3. The method for online recovery of lubricating oil in a steam turbine exhaust fan according to claim 2, characterized in that: The maximum design negative pressure value at the air intake of the lubricating oil exhaust system (3) is converted into the liquid column height for calculation, with a safety margin of 50~150mm water column.

4. The method for online recovery of lubricating oil in a steam turbine exhaust fan according to any one of claims 1 to 3, characterized in that: The oil drain line (1) maintains a continuous downward slope along the flow direction of the lubricating oil.

5. The method for online recovery of lubricating oil in a steam turbine exhaust fan according to claim 4, characterized in that: The slope ranges from 1% to 5%, meaning a drop of 10mm to 50mm per meter of pipe.

6. The method for online recovery of lubricating oil in a steam turbine exhaust fan according to any one of claims 1 to 3, characterized in that: The oil drain line (1) includes a first pipe (11), a U-shaped liquid seal bend (12), and a second pipe (13) connected in sequence, all of which are made of oil-resistant and temperature-resistant metal pipes or high-performance plastic pipes.

7. The method for online recovery of lubricating oil in a steam turbine exhaust fan according to any one of claims 1 to 3, characterized in that: The manual isolation valve (4) is a manual ball valve or a manual gate valve.

8. The method for online recovery of lubricating oil in a steam turbine exhaust fan according to any one of claims 1 to 3, characterized in that: The connection point between the oil drain pipe (1) and the lubricating oil exhaust system (3) is located on the exhaust header between the exhaust port of the main lubricating oil tank and the exhaust fan inlet. This location has a stable negative pressure, and the connection point is located at the top or side of the exhaust header.

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