On the operation of catalytic condensing steam turbines, particularly the extraction systems

2. Vacuum pumps: The vacuum pumps used in turbine condensers are typically steam ejector types. There are single-stage start-up pumps as well as two-stage main pumps (also known as dual-stage pumps). The starting exhaust pump is used to quickly establish a vacuum in the condenser sufficient to start the turbine before it begins to operate, while the main exhaust pump operates alongside the condenser during normal turbine operation. 2.1 Main pump The main pump consists of two single-stage jet ejectors (Stage I and Stage II) in series, along with two surface coolers (an intermediate cooler and a rear cooler). A stage 1 steam ejector consists of a stage 1 nozzle and a stage 1 diffuser; a stage 2 steam ejector consists of a stage 2 nozzle and a stage 2 diffuser. The intermediate cooler and the aftercooler are located in the same container, separated from each other by a partition. The cooling tubes are straight tubes, which are press-fitted onto the fixed tube plates at both ends of the cooler. The water chamber is located at both ends of the cooler, and is equipped with a cooling water inlet and a cooling water outlet. The intermediate cooler shell is equipped with a condensate outlet that can be connected to the condenser water seal tube. The lower part of the after-cooler shell contains an automatic drain that can be connected to the condenser, and it is also fitted with a water level indicator. To ensure redundancy in the turbine installation, the main exhaust pump is designed as a two-stage exhaust system, comprising two primary jet exhaust pumps and two secondary jet exhaust pumps connected in parallel. The entire main extractor is supported on the foundation by two rigid supports. The air-steam mixture is drawn from the condenser into the mixing chamber of the stage I jet ejector, where it mixes with the high-speed steam ejected from the nozzles and enters the diffuser; after compression, it is discharged into the intermediate cooler. After being cooled in the intermediate cooler, the steam-air mixture has the air and some of the uncondensed steam drawn in by the secondary ejector; there they mix with the high-speed steam ejected from the nozzles and enter the diffuser, where they are compressed before being discharged to the after-cooler. After being cooled in the cooler, the steam-air mixture has its steam converted into condensed water, while the air is released into the atmosphere. The condensed water cooled in the intercooler is returned to the condenser through a water seal tube. It relies on gravity to carry out the hydrophobic function. The condensed water cooled in the aftercooler is returned to the condenser through a float drain valve. 2.2 Starting pump: To reduce the time required to establish a vacuum in the system, a separate starting pump is usually provided. The starting pump is a single-stage steam ejector without a cooler. During operation, the entire steam-air mixture is directly released into the atmosphere. Due to the high steam consumption of the starting pump, it is not suitable to be used as a pump for normal operation.