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Application of electrostatic oil purifier in turbine oil system

Abstract: the quality of turbine lubricating oil and fire-resistant hydraulic oil directly affects the safe and reliable operation of the turbine unit. With a trend towards large-capacity and high parameter turbines, the requirements for cleanliness of turbine lubricating oil and fire-resistant hydraulic oil are becoming higher and higher. This paper introduces the principle and performance of the electrostatic oil purifier and presents its application in turbine lubricating oil and fire-resistant hydraulic oil.

Key words:electrostatic oil purifier, film, lubricating oil, fire-resistant hydraulic oil, turbine.

Introduction
Steam turbine lubrication system used steam turbine lubricating oil and hydraulic control system resistant hydraulic oil, has strict requirements in unit operation, such as viscosity, particle pollution, moisture, acid value, oxidation resistance, emulsification resistance [1-2], the particle pollution is particularly important, related to the turbine rotor shaft and bearing wear, control system, the flexibility of valve and servo valve, directly affect the operation safety of steam turbine equipment.

With the development of steam turbine equipment in the direction of large capacity and high parameters, in order to reduce the structural size of the oil motor, the anti-combustible hydraulic oil develops in the direction of high pressure [3-4]. With the improvement of the reliability requirements of unit operation, the cleanliness requirements of steam turbine lubricating oil and anti-combustible hydraulic oil are becoming higher and higher. In order to ensure that the oil quality index in the unit operation is always controlled within the standard range, the lubricating oil and anti-combustible hydraulic oil online oil purifier treatment is needed, so the selection of the oil purifier and its treatment effect will directly affect the safety and reliability of the steam turbine operation.

Type of purifier
The type of oil purifier is different according to the filtration principle. The oil purifier can be divided into mechanical filtration, centrifugal filtration and electrostatic adsorption filtration (as shown in Table 1). In practical engineering, several different treatment methods are often applied in combination.

1.1 Mechanical oil purifier
The mechanical oil purifier is to intercept the granular impurities in the oil through the mechanical filter element, its purifier effect is directly related to the accuracy of the mechanical filter the filter accuracy is up to 1 um, this type of oil purifier is widely used in the power system. Generally, the double oil purifier, return oil purifier screen and online purifier screen configured in the lubricating oil system all belong to the mechanical oil purifier machine. Large particle impurities in the lubricating oil system can be removed by mechanical oil purifier, and small particle impurities can be removed by precision mechanical purifier element.
The disadvantage of mechanical oil purifier: the higher the filtration accuracy, the greater corresponding resistance force, the oil supply pressure loss is greater; the service life ratio of the filter element shorter, the work needs to replace the filter element frequently in the work, the operation is not possible causes artificial pollution; unable to effectively purifier the water and glue in the oil The substance and debris smaller than the size of the purifier. To overcome the Upper disadvantages, in engineering applications, mechanical oil purifier often with other net Chemical method (such as vacuum dehydration, etc.), used together to achieve the best place rational effect.

1.2 Centrifugal oil purifier

The centrifugal filtration technology of oil purifier is to use the centrifuge to purify the oil in the tank. By rotating the oil containing particles and other pollutants at high speed, the density is greater than the oil impurities centrifugal out, to achieve the purpose of separating the clean oil. Its advantages are that the removal of free water and large particles of impurities has a good effect, large treatment capacity, the disadvantage is that the removal of small particles is poor, and can not remove non-free water. Centrifugal oil purifier is widely used in fuel treatment in gas turbine plant, and is often used in combination with mechanical filtration treatment in steam turbine lubricating oil system. Because the high-speed rotation of the centrifuge is also large, the equipment is noisy, poor working environment, volume and heavy.

1.3 Electrostatic oil purifier

The electrostatic oil purifier mainly uses the high voltage electrostatic field generated by the electrostatic generator to make the pollutant particles in the oil loaded with electrostatic ions and are attached to the fiber under the action of the electric field. The principle is shown in Figure 1. Due to the adsorption principle rather than through filtration, electrostatic oil purifier can capture all kinds of impurities of 0. 02 μ m, including hard metal materials, soft particles can be removed.

Features of electrostatic oil purifier:

(1)High purification accuracy, filter accuracy is up to 0. 1 μ m, Can remove sub-micron pollutants;
(2)can effectively combine the vacuum system and the coalescent system, Can quickly remove water and gas;
(3)fast purification speed, Can quickly process particles, fast clean; Large flow rate, Can meet the needs of washing and cleaning;
(4)cleaning system, through electrostatic polymerization purification technology will not only remove the impurities and particles in the oil, but also can remove the acid products, live colloid, oil mud, varnish and other harmful substances clean, prevent regeneration, improve the oil product index;
(5)a wide range of application, even if the moisture in the oil exceeds the standard, but also can work normally.

2 Varnish
2.1 Hazard of varnish
"varnish" is also known as the carbon accumulation, glue, lacquer material, elastic oxygen Chemical, patent leather, etc., is a possible orange, brown or black non-soluble Solution of the membrane sediment, is the product of oil deterioration. After the varnish appears in the steam turbine lubricating oil system, slide inside the bearing The varnish formed is easily attached to the metal surface, especially in the most bearings The small gap results in the minimum oil film thickness and the maximum oil film pressure Large, bearing capacity decreases, lubricating oil temperature increases, the safety of bearing bush will adversely affect [4,10-11].
varnish phenomenon and its harm in Europe and America, Japan has been valued, the United States The country has formulated the varnish detection standard (ASTM D7843-18), and The varnish tendency index is included in the assessment index of oil change. Our country has also listed varnish as a test item in GB / T 34580-2017.

The hazards of the varnish are as follows

(1) due to the high working temperature of the bearing surface, the varnish is easy to attach to the working surface of the shuttle, over time, the surface will be molten state (see figure 2);

Application of electrostatic o2

:(2) block clearance and increase friction;
(3) block purifier and cause equipment damage;
(4) varnish deposited on cooler leads to poor heat dissipation, oil temperature rise and oil oxidation;
(5) varnish is polar, easy to attach to metal or solid particles, causing equipment wear.

2.2 varnish removal

Lubricating oil "soft particles" of varnish and sludge accounted for more than 80% of the total pollutants [12-13], because of the "soft particles" size is small, if the use of micro mechanical filtration method is easy to cause purifier, core purifier blockage and filtration effect is not ideal, and electrostatic purifier particles field adsorption on the collector, therefore, can effectively remove small particles in the oil pollutants, and scale capacity is large, so is widely used abroad to remove the varnish and sludge in the oil. The electrostatic oil purifier can not only effectively remove the varnish in the lubricating oil, but also wash the varnish that has been deposited on the metal surface to ensure the safe operation of the equipment and prolong the service life of the oil.

1.Application of electrostatic oil purifier in lubricating oil system

When a power plant in Fangchenggang overhauled the 3 # machine in June 2019, Very obvious varnish phenomenon was found on the axial tile (as shown in Figure 3), and obvious scratch marks. Varnish is found after oil sampling test The membrane propensity index exceeded the standard, reaching 18.2. Lube-oil system of the unit Equipped with double oil purifier, return oil purifier, online purifier, but all belong to In mechanical purifiers, it is difficult to remove the varnish. In addition, the power plant was purchased An imported brand centrifugal oil purifier purifier, also can not dislodge varnish.
The lubricating oil tank of this 3 # machine is 43 m³, using the Great Wall TSA 46 Steam turbine oil (Class A). In order to fasten this lubricating oil In the varnish completely removed, and prevent the varnish again, design VOC-E-5000 with a flow rate of 3000 L / h, type electrostatic purifier was produced Oil machine (as shown in Figure 4), and applied to the lubricating oil of Fangchenggang power plant Purification regeneration. The purified oil is sampled at 1000 mL regularly, respectively In the third-party testing institutions Shanghai Runkai and Guangzhou Research Institute laboratory analyse.

Application of electrostatic o4
Application of electrostatic o3

4. Application of electrostatic oil purifier in anti-combustion hydraulic oil system

In March 2019, a power plant in Hebei found the hydraulic oil of 1 # black (as shown in FIG. 6). After sampling, Shanghai Runkai tested the result of varnish tendency index was 70.2, which seriously exceeded the standard, and the acid value was 0. 23. In May 2019, our JD-KR 4 electrostatic oil purifier was used to purify the anticombustion hydraulic oil. After one month of use, the oil varnish index decreased to 55.2. In the second month of purification process, found that the varnish index not down but a little increase, found in the replacement of purifier purification equipment purifier are covered with mud / film impurities (as shown in figure 7), the whole electrode is covered by mud / film, lead to purification regeneration device loss of electrostatic purifier adsorption function. After replacing the purifier element, the index of anti-combustible hydraulic oil varnish decreased to 8. 9 (as shown in Figure 8).

Application of electrostatic o5
Application of electrostatic o7
Application of electrostatic o6

5 Conclusion

 

The oil purifier required by the lubricating oil and anti-combustion hydraulic oil system in the power plant can be configured according to the actual demand. If the oil is in good condition, the ordinary mechanical oil purifier or centrifugal oil purifier can be configured. If the oil condition is poor, the particulate matter is more, and the varnish phenomenon is serious, the electrostatic oil purifier combined resin technology with high filtration accuracy should be configured. In contrast, the electrostatic oil purifier has the best filtration effect, the removal rate of small particles, oxides, sludge and other impurities is high, and can completely and effectively remove the varnish, can effectively improve the qualified rate of oil particle size index, and correspondingly improve the safety and reliability of steam turbine operation.


Post time: Mar-24-2023
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