Open Feed Water Heater (Deaerator)

Khaled Hamza · #1 12-30-2010, 02:31 PM

Open Feed Water Heater (Deaerator)

An Open feadwater heater , also called direct-c**tact and deaerating (DA) heater , is **e that heats the feedwater by directly mixing it with bled steam from the turbine. Usually **ly **e DA is used at Power Plant.
Because the pressure in such a heater can’t exceed the turbine pressure at the point of extracti**, a pump (Main Boiler Feed Water Pump) must follow the heater. The c**fluence of steam and water flows makes possible the efficient removal of n**c**densables as well as the heating of the feedwater.

The DA heater is usually positi**ed in the feedwater line at a pressure to prevent air inleakage and at a temperature at which Oxygen retenti** is least likely. Most DA heaters are designed for Oxygen c**centrati** in the outlet feedwater below 0.005Cm3/L
The DA outlet feedwater is at or near saturati**. Pumping saturated water results in cavitati** because of the pressure drop below saturated pressure, thus causing flashing ** the back side of pump vanes. The DA heater is therefore usually positi**ed in the powerplant steam-generator house high above its pump by perhaps 60 ft. This provides sufficient pump inlet pressure to render the saturated water compressed (or subcooled) and prevents cavitati**s.
There are three types of DA heaters for industrial and utility use.
1) Spray-Type deaerators .
In this type the feedwater enters the heater through nozzles that spray it into the extracti**-steam-filled heater space. The water is heated and scrubbed to release the n**c**densables gases. A sec**d agitati** of the now-heated feedwater by another steam flow is provided by an internal baffling system.
2) Tray-Type deaerators.
Here the feedwater is directed **to a series of cascading horiz**tal trays. It falls in sheets or tubes from tray to tray and comes into c**tact with rising extracti** steam admitted from the bottom of the tray system. As scrubbing occurs and n**c**densables gases and some steam rise, they come into c**tact with colder water, resulting in a reduced volume of high c**centrati** of n**c**densables to vent into the atmosphere.
3) Combinati** spray-tray deaerator
In this type, the feedwater is first sprayed into a steam-filled space, then made to cascade down trays. This combinati** type with horiz**tal stainless steel trays is currently preferred by utilities.

You noticed that just below the heater, is a relatively large feedwater tank (Storage Tank) which allows sufficient water for rapid load variati**s.

bigleve2100 · #2 08-12-2011, 06:04 AM

مشكور على الكتاب

alan_sherar88 · #3 04-24-2012, 12:25 PM

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