What are the problems and hazards of the condenser fouling of the condensing turbine unit in the thermal power plant?

Condensing steam turbine of the thermoelectric power plant often encounters the problem of gradual vacuum drop during operation. Especially in summer, the condenser vacuum has a greater impact on the economy of steam turbine operation. For example, the other conditions are unchanged, the degree of vacuum changes by 1% Steam turbine steam consumption rate of an average change of 1% to 2%. Not only increase the unit energy consumption, affecting unit economy, but also threaten the safety of units, but also reduce the power load in severe cases. Therefore, the general provisions: When the exhaust pressure is increased to 0.015MPa, the load should be reduced. When the exhaust pressure is increased to about 0.03MPa, the load should be completely discharged until the shutdown according to the specified conditions, which directly affects the Economic benefits. One of the main causes of the vacuum drop is the formation of dirt on the inner wall of the condenser copper tube. And gradually thickened over time, blocking the heat exchange.

In general, power plants use well water and river water as circulating water. These natural water originally contain impurities and salts that can be dissolved in water, such as calcium bicarbonate and magnesium bicarbonate salts. When such natural water is used as circulating water, the water is concentrated over a long period of time due to evaporation loss. When it is concentrated to a certain extent beyond its solubility, carbonate is a water-insoluble precipitate and water exceeds this limit Part of the salt will be deposited in the condenser copper tube wall to form hard salt scale. According to the principle of fluid mechanics, circulation of water in copper pipe flow is divided into two basic forms of laminar flow and turbulence. Under the action of external force, the circulating cooling water flowing in the copper pipe flows through the same section in the copper pipe at different flow velocities, closely adheres to the first layer of the pipe wall and has a slow flow rate (called the boundary retention layer). CaCO3 and water in the sticky dirt most likely to remain in the copper wall, the formation of boundary layer retention.

According to the relevant information, when the scale thickness of the water-cooling equipment heat exchanger is> 2.16mm, the heat transfer coefficient will be reduced by an average of 51% and the operating efficiency of the equipment will be reduced by 50% while the limescale time will only be 25 days. Such a serious hazard caused by a short period of time, resulting in long-term operation of the condenser in low efficiency.

In order to solve the scale problem, some enterprises adopt the parking cleaning, and arrange the cleaning times according to the severity of scaling on the inner wall of the condenser copper tube. To stop four days: 50,000 KW unit, for example, the loss of 1 million, but also to pay labor costs. Hard scale pickling is handled properly, but also seriously affect the service life of brass, not counting the pickling pollution problems. After cleaning is completed? Only to maintain a month, but also the summer can not be missed; the other part of enterprises in the water plus scale inhibitor, but also delay the scaling, but the scale inhibitor expensive cost is too high; there are some companies invented in the 1950s rubber ball cleaning , Glue ball cleaning system needs running costs in operation, the glue ball recovery rate is low, can not remove hard scale, and there is a long-term glue ball is blocked by scale in the copper tube phenomenon, affecting unit efficiency.