Product Details
I. Features
During the boiler startup process, when the steam turbine is warmed up by the steam, more steam will enter the condenser. If a certain vacuum is not established within the condenser, the entry of steam and water will cause the condenser to develop positive pressure, damaging the equipment. Establishing a vacuum in the condenser is an essential condition for the steam turbine to start up. The condenser and some low-pressure equipment (like condensate pumps, drainage pumps, and some low-pressure heaters, etc.) are in a vacuum state internally during normal operation. Due to the loose piping and casing, air leaks in, thereby destroying the vacuum of the condenser and threatening the safe and economic operation of the steam turbine. At the same time, the partial pressure of air in the condenser increases, causing the dissolved oxygen content in the condensate water to rise, which intensifies corrosion of the thermal equipment and piping. The presence of air also increases the heat transfer resistance in the steam absorber, affecting the cooling of the steam turbine exhaust by the circulating cooling water, increasing the power consumption of the plant. Therefore, air must be continuously extracted from the condenser during operation.
In summary, the vacuum system's purpose is:①Establish condenser vacuum during the initial startup of the unit②Maintain the condenser vacuum during normal unit operation to ensure safe and economic operation of the unit. The main equipment for condenser vacuum extraction includes vacuum pumps and vacuum ejectors. The water-jet vacuum ejector system is widely used on domestic large and medium-sized units due to its simple design and reliable operation.
Section II: Structure and Working Principle of Water Jet Vacuum Pump
In modern power plants, the widely used vacuum pump is the jet vacuum pump, which boasts compact layout, simple structure, easy maintenance, reliable operation, and the ability to establish the required vacuum in a short time. Jet vacuum pumps can be divided into steam jet vacuum pumps and water jet vacuum pumps based on different working mediums. The principles of these two types of vacuum pumps are essentially the same; the only difference is the working medium. The working medium for steam jet vacuum pumps is pressurized steam, while for water jet vacuum pumps, it is pressurized water. Small capacity units often use steam jet vacuum pumps. For high-parameter, large capacity units, due to the use of slide parameter start-up methods, there is no possibility of having sufficient steam supply for the steam jet vacuum pump before the unit starts up. Moreover, it is necessary to throttle high-pressure steam to1.2-1.6MPaPressure steam injection vacuum pump is clearly uneconomical, and it also requires the installation of a steam injection cooler for the recovery of working fluid, which complicates the thermal system. Therefore, Currently, our country's large capacity units all utilize steam ejectors, which are mainly composed of working water inlet, working nozzle, mixing chamber, diffuser, and check valve, etc.
Water Jet Vacuum Pump Vacuum System. It consists of a water jet vacuum pump, water jet pump, water jet tank, and connecting pipes. The exhaust from each low-pressure heater, the condensate pump, and the drain pump are collected into a condenser via exhaust pipes, which is connected to the working chamber of the water jet vacuum pump. Water from the water jet tank, sourced from circulating water or a deep well, is pressurized by the water jet pump (one in operation and one as a spare), and then injected into the vacuum pump. The high-speed water jet emitted by the nozzle in the pump generates a high vacuum in the working chamber, thereby extracting the gas-vapor mixture from the condenser. After expansion, this mixture returns to the water jet tank.
III.Model Description
4. Product and Component Matching Table
