Reformation of Water Ring Vacuum Pump Cooling Water System in Power Plant

Analysis of Economic Benefit before and after the Transformation of the Cooling Water System of the Exchanger of the Exchanger of Shandong Jiyuan Luneng Coal & Electricity Co., Ltd. (Jining 272502).

The water ring type vacuum pump belongs to a mechanical centrifugal pump, and an impeller rotor is eccentrically mounted inside a cylindrical pump housing. When the impeller rotates under the drive of the motor, the working fluid is driven by the blades to obtain the circumferential speed, and the centrifugal force is thrown to the outer diameter to form a water ring that circulates along the pump casing. Because of the eccentric arrangement of the impeller, the water ring is relatively In the relative movement of the blades, the space volume between adjacent two blades is periodically changed, as if the liquid piston moves radially and reciprocally between the cascades, and when the “water piston” between the two blades is centrifugally pushed outward, the space As the volume gradually increases, it draws gas from the axial suction port. When the “water piston” between the blades makes a relative movement in the direction of the axis, the space gradually changes from large to small, and the suctioned gas is gradually compressed and discharged through the exhaust port. As the impeller rotates steadily, each volume changes in rotation and the suction and exhaust processes continue as shown.

Water ring vacuum pump body structure IS body 2. Rubber ball 3. Exhaust port 4. Suction port 5. Impeller 6. Water ring The vacuum pump of Yangcheng Power Plant adopts the equipment of Tsurumi Vacuum (Shanghai) Co., Ltd. The vacuum pump unit model is 150EVMA (originally imported, stainless steel impeller) with a stage number of 2, compression ratio of 1:5, 1:6. Water ring vacuum pump unit performance is as follows: Water ring vacuum pump suction pressure: minimum suction pressure (limit axis Power: The maximum shaft power is 49kW, the minimum shaft power is 11.5kPa when the shaft power is 45kW. 315M8, the rated power is 75kW, the speed is 740r/min, the voltage is 380V, the motor protection class is IP44, the motor insulation class is F class.

Pump heat exchanger: The cooling water volume is 25m3/h, the water quality is circulating water, and the water temperature is 2033C. (The two pumps are running at the same time).

Heat exchanger: (plate type used Alfa Laval imported products) heat transfer area of ​​7m2, cooling water pressure transformation 丨r; increase k water inlet vacuum system transformation Figure 3, the necessity of vacuum system transformation in the operation of the power plant, The deterioration of the condenser will directly cause the consumption of the turbine and the output of the unit. When the unit's steam consumption is not changed, the vacuum will deteriorate by 1%, which will cause the power of the turbine to decrease by approximately 0.7% of the rated capacity when the unit load. When the same, the equivalent of the power plant's coal consumption increased by about 1% 2%. General power plant vacuum pump plate heat exchanger cooling water system uses industrial water, to summer, industrial water cooling water temperature up to 33C, resulting in plate heat exchanger The cooling effect is reduced, resulting in the working water temperature in the steam separator up to about 42C. Knowing from the working principle of the vacuum pump and a certain saturation temperature corresponding to a certain pressure, when the working water temperature reaches 42C, the ideal vacuum pumping capacity of the vacuum pump is 93.1kPa, and the vacuum is reduced, seriously Affects the efficiency of the unit.

The size of the steam turbine condenser water ring vacuum pump in the power plant is determined based on the design and operating conditions of the Yangcheng Power Plant generator set. When running within the design range, the vacuum pump can operate normally, but the cooling water temperature is higher in summer. Or the dirty heat of the plate heat exchanger causes the vacuum pump heat exchanger to have poor cooling effect, and the vacuum pump will run under high vacuum, which is equivalent to running near or in a state of sudden death. Due to the inherent physical phenomenon, under the condition that the water temperature is certain, the vacuum The higher the water temperature is, the higher the water temperature is, the water in the pump is close to boiling and a large number of bubbles will be generated. The generation and collapse of bubbles will cause cavitation damage to the impeller, destroy the dynamic balance of the impeller, cause strong vibration of the pump body, and damage the vacuum pump. The ancillary equipment (pressure vacuum gauge, pressure switch, feedback device for the inlet pneumatic door, etc.), and it will issue a very large cavitation noise, these conditions seriously affect the safe operation of the vacuum pump set and the safe operation of the turbine generator set.

Based on the above analysis, to solve the unit vacuum reduction and prevent vacuum pump cavitation damage equipment, the best solution is to reduce the working water Fourth, the transformation process and the effect of transformation transformation process Yangcheng power plant according to the actual situation in the factory, in considering the minimum In the case of investment, the use of deep well water to cool working water has achieved good results. After the transformation of the vacuum system.

The deep well water pressure in the plant is 0.4 MPa, and the pipe diameter is 50mm. The effect and benefit of the cooling water flow reforming adopts deep well water cooling, which first solves the problem that the summer operating vacuum is reduced and the unit economy is affected.

In summer, the average temperature of deep wells is 18C. After the working water is cooled by deep well water, the water temperature is 21C. The internal working water temperature of the steam separator is 27C. The ideal vacuum pumping capacity of the vacuum pump is 97.8kPa. According to the ideal condition, the condenser vacuum can increase by 4.7. kPa, due to the impact of unit load, plate heat exchanger fouling, and dirt in the actual operation, the condenser vacuum is increased by an average of 3.5 kPa, and the rate of increase is 3.45 per cent. Analysis of Causes for Hydrostatic Elimination of Water Ring Vacuum Pump and Its Modification Schemes .

SME Management and Technology, 2009 (7). GM GM General Machinery

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