Factory liquid ring vacuum pump principle and structure characteristics
The liquid ring vacuum pump belongs to the mechanical centrifugal pump, and the impeller rotor is eccentrically installed in the cylindrical pump shell. When the impeller rotates under the drive of the motor, the working fluid obtains the circumferential speed under the drive of the blade. Due to the centrifugal force, the working fluid is thrown to the outer diameter to form a water ring swirling along the pump housing. Due to the eccentric arrangement of the impeller, the water ring moves relative to the blade, so that the space volume between the adjacent two blades changes periodically, just like the liquid piston does the radial reciprocating motion between the cascades, When the “water piston” between the two blades is centrifugally pushed outward, the space volume gradually increases from small to large, so the gas is sucked out from the axial suction port.
When the “water piston” between the blades moves towards the axis, the space gradually becomes smaller and larger, and the gas inhaled is gradually compressed and discharged through the exhaust port. As the impeller rotates stably, the volume of each impeller changes, so that the suction and exhaust processes continue, as shown in.
Liquid ring vacuum pump of structure
1. S body 2. Rubber ball 3. Exhaust port 4. Suction port 5. Impeller 6. Equipment used for vacuum pump of water ring power plant. The model of vacuum pump set is 150evma (original import, stainless steel impeller), the stage is 2, and the compression ratio is 1:5, 1:6
Liquid ring vacuum pump unit is as follows performance:
Suction pressure of liquid ring vacuum pump: minimum suction pressure (limit shaft power: the maximum shaft power is 49KW, the minimum shaft power is 45KW. 315m8 when the shaft power is 11.8kpa, the rated power is 75kW, the rotating speed is 740r / min, the voltage is 380V, the motor protection grade is IP44, and the motor insulation grade is f.
Pump heat exchanger: the cooling water volume is 25m3 / h, the water quality is circulating water, and the water temperature is 2033 ℃ (two pumps operate at the same time).
Heat exchanger: (Alfa Laval imported product is selected for plate type) heat exchange area is 7m2, cooling water pressure is less than 0.2MPa, design rated temperature of cooling water inlet is 20 ℃, maximum temperature is 33 ℃, cooling water volume is 25m3 / h, working water volume is 12.5m3/h, working water inlet temperature is 28 ℃, outlet temperature is 22 ℃, end difference is 2 ℃, cooling water side pressure drop is less than 0.05Mpa (Note: working water adopts demineralized water).
Transformation: increase the necessity of transformation of k-piece water inlet vacuum system figure 3. In the operation of the power plant, the deterioration of the working state of the condenser will directly cause the consumption of the steam turbine and the output of the unit. When the steam consumption of the unit is constant, the deterioration of the vacuum will cause the power of the steam turbine to be reduced by about 0.7% 1% of the rated capacity. When the load of the unit is constant, it is equivalent to that of the power plant The consumption of coal increases about 1% 2%. In general, the cooling water system of vacuum pump plate heat exchanger in power plant uses industrial water. In summer, the temperature of industrial water cooling water is as high as about 33 ℃, which reduces the cooling effect of plate heat exchanger and results in the working water temperature of steam water separator as high as about 42 ℃. According to the working principle of vacuum pump and the corresponding pressure of certain saturation temperature, when the working water temperature When the temperature reaches 42 ℃, the ideal vacuumizing capacity of vacuum pump is 93.1kpa, and the vacuum is reduced, which seriously affects the efficiency of the unit.
The size of the liquid ring vacuum pump of the steam turbine condenser in the power plant is determined according to the design and operation conditions of the power plant generator set. When the operation is within the design range, the vacuum pump can operate normally
However, in summer, due to the high temperature of cooling water or dirty plate heat exchanger, the cooling effect of the vacuum pump heat exchanger is poor, and the vacuum pump will operate under high vacuum, which is equivalent to operating near or in a suffocating state. Due to the inherent physical phenomenon, under certain water temperature, the higher the true air is, the higher the water temperature is, the water in the pump will be close to boiling and generate a large number of bubbles, and the production of bubbles The process of generation and rupture will cause cavitation damage to the impeller, damage the dynamic balance of the impeller, cause strong vibration of the pump body, damage the auxiliary equipment of the vacuum pump (pressure vacuum gauge, pressure switch, feedback device of the inlet pneumatic valve, etc.), and produce very large cavitation noise, which seriously affects the safe operation of the vacuum pump unit and the safe operation of the steam turbine generator unit.
Based on the above analysis, in order to reduce the vacuum of the unit and prevent the cavitation damage of the vacuum pump, the best solution is to reduce the working water. Fourth, according to the actual situation of the plant, considering the minimum investment, Yangcheng Power Plant adopts deep well water to cool the working water, and achieves good results. It is the situation after the vacuum system transformation.
In summer, the average horizontal temperature of the deep well is 18 ℃, the water temperature of the working water after cooling by the deep well water is 21 ℃, the temperature of the working water inside the steam water separator is 27 ℃, and the ideal vacuum pumping capacity of the vacuum pump is 97.8kpa. According to the ideal state, the vacuum of the condenser can be increased by 4.7kpa. Because in actual operation, the vacuum of the condenser is increased on average due to the influence of the unit load, scaling and fouling of the plate heat exchanger The pressure of deep well water in the plant is 0.4MPa, and the pipe diameter is 50mm. The effect and benefit of cooling water flow after transformation adopt deep well water cooling. First of all, the problem that the operating vacuum in summer is reduced and the unit economy is affected is solved.
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