During this process, the steam condensate collected from different heaters/coolers in the cycle joins the main condensate flow, is heated in the low-pressure heaters, and is finally stored in the feedwater storage tank of the deaerating heater or deaerator ( Figure 9.22). The main condensate is collected in the hotwell, which is then pumped by condensate extraction pumps (CEP) to the deaerator through steam jet- air ejectors (not required if the vacuum pump is used), gland steam condenser, and LP feedwater heaters, where condensate is successively heated by extraction steam. Steam after expansion in the LP turbine is condensed in the condenser. Ĭoupon testing with all types of metallurgy present in the circulating water system is important to monitor the cumulative effects of fluctuation in the circulating water chemistry.Ĭopper-containing alloys should not be used because they are incompatible with amines, especially the high concentrations of amines and dissociated ammonia that are encountered during startups and shutdowns.It reduces consumption of chlorine and other internal treatment chemicals and will remove suspended solids that may be introduced from condensate dumps or HRSG blowdown. Using cooling tower sidestream filtration makes circulating water quality easier to stabilize on startup and shutdown. Using a cooling tower to receive HRSG blowdown is another method to be considered. Providing vacuum pumps should be evaluated. This is not necessarily effective over a wide range of part-load operations. High power fluid usage is associated with efficiencies as high as 70%.Įstablishing and maintaining vacuum in the condenser is usually done with staged SJAEs (one set for hogging one set for steady state operation). Low power-fluid usage is associated with efficiencies as low as 30%. Oddly, the more power fluid you use, the higher the overall efficiency of the unit will be. Except in very specific cases, greater than three compression ratios require uneconomic quantities of power fluid. The exhaust pressure for an ejector can be as much as 10 times suction pressure, but there is a strong relationship between compression ratios and mass-flow rate of power fluid-more ratios requires significantly more power fluid. The exhaust pressure for an eductor is limited to about 1.5–3 times the suction pressure (in absolute units). The combined stream is left at an intermediate pressure. In both cases the high pressure/high velocity power fluid entrains the suction fluid at the no-flow boundary between the two fluids, which causes energy to transfer from the power fluid to the suction fluid. Simpson P.E., in Practical Onshore Gas Field Engineering, 2017 8.4.1 Eductor vs ejectorīoth eductors and ejectors are in the family of equipment that includes air ejectors, evacuators, sand blasters, certain kinds of paint sprayers, hose-end sprayers, and jet pumps. The nozzle is usually made of stainless steel while the extraction chamber and diffuser are of steel castings or steel plates however, the material may differ according to the condition of the steam handled.ĭavid A. The diffuser raises the entrained air pressure. High-velocity steam jets from the nozzle entrain the air. The second-stage ejector extracts air with a small amount of saturated steam and discharges it into the atmosphere. The cooler is divided into the intercooler and the aftercooler, which are mounted on the outlets of two stages of the ejector, respectively. This air ejector is designed to extract saturated steam and air from the condenser about 2.3 times the volume of air.
The two-stage, twin-element air ejector can extract a specified amount of dry air with its single element and maintain a very high vacuum on the order of 735 mmHg. The hot liquid -such as sea water to be desalinated-to be evaporated is passed into a bottom chamber of each stage vessel, with vapor flowing upwardly through demistors and channels, into contact with the dimpled plates, and the condensate falling as a thin film down the plates and collecting in the condensate trough.Swapan Basu, Ajay Kumar Debnath, in Power Plant Instrumentation and Control Handbook (Second Edition), 2019 3.5.6.4 Performance A condensate collection trough is mounted below the dimpled plates and at the I-beams, the I-beams having openings in them through which condensate collected by the trough passes from one end of the vessel to the other. Each stage may be formed by a circular cross-section vessel, with I-beams-or like supports-extending horizontally at about the horizontal diameter of the vessel, and supporting the dimpled plates on them. One, two, or more sets of plates may be mounted in each evaporator stage, the sets stacked upon one another in a tier arrangement. Abstract: A multi-stage flash evaporator is constructed so that the evaporator elements are dimpled plates mounted so that they extend horizontally.