A deaerator is a widely used device for removing oxygen and other dissolved gases from feedwater to steam-generating boilers. In particular, dissolved oxygen in the boiler feed water will cause serious corrosion damage in the vapor system by sticking to the walls of metal pipes and other metal equipment and forming oxides (rust). Dissolved carbon dioxide combines with water to form carbonic acid which causes further corrosion. Most deaerators are designed to remove oxygen to a level of 7 ppb by weight (0.005 cm/L) or less and essentially eliminate carbon dioxide.
There are two basic types of deaerator, Termochimica & amp; type-tray and spray type Stork:
- The Spray & ampo-type Termochimica tray (also called cascade-type ) includes a vertical or horizontal-shaped deaeration section mounted on top of the ship's horizontal cylinder serves as a deaerated boiler feedwater storage tank.
- Stork spray type consists only of horizontal (or vertical) cylindrical vessels that function both as deeration and storage tanks for boiler feed water.
Working Principle Deaerator [4]
Water is heated to near saturation temperature with minimum pressure drop and minimum ventilation. This ensures the best thermal operating efficiency. Deeration is done by spraying boiler feed water through several layers of trays designed to provide a large contact area between the liquid surface and deaerative vapor. This scouring vapor is fed from the bottom of the deaerator. When making contact with the boiler feed water, it heats to a saturation temperature and the dissolved gases are released from the feedwater through the vent valve. The treated water falls into the storage tank under the deaerator.
Video Deaerator
Jenis deaerator
There are many different horizontal and vertical deaerators available from a number of manufacturers, and the details of the actual construction will vary from one manufacturer to another. Figures 1 and 2 are representative schematic diagrams depicting each of the two main types of deaerators.
Termochimica Spray & amp; Type-Tray deaerator
The typical spray deer & amperator of Figure 1 has a vertically domeed deaeration section mounted on a horizontal boiler feedwater storage vessel. Boiler feed water enters the vertical deaeration section through the spray valve above the perforated tray and then flows downward through the perforation. Low pressure steam deaeration enters beneath the perforated tray and flows upward through the perforation. Combination of spray & amp; the trays guarantee very high performance (as confirmed by HEI std) due to longer contact time between steam and water. Some designs use different types of packed beds, not perforated trays, to provide good contact and mixing between steam and boiler feed water.
The gas vapor dissolves from the feedwater boiler and exits through the vent valve at the top of the dome. If the ventilation valve is not adequately opened, the deaerator will not function properly, causing a high oxygen content in the feed water to the boiler. If the boiler does not have an oxygen content analyzer, a high level in the chloride boiler may indicate that the vent valve is not open enough. Some designs may include a retaining condenser to trap and recover the gushed water in the released gas. The ventilation path usually includes a valve and only enough steam is allowed to escape with the released gas to provide a small visible steam mark.
The deaerated water flows downward into the horizontal storage vessel from which it is pumped to the steam generator boiler system. The low-pressure steam heater, which enters the horizontal vessel through the sparger pipe at the bottom of the vessel, is provided to keep the boiler feed water stored warm. External insulation from ships is usually provided to minimize heat loss.
Stran Spray-type deaerator
As shown in FIG. 2, a typical spray deaerator type is a horizontal vessel having a preheating portion E and a deaeration part F. The two parts are separated by a baffle (C). Low vapor pressure enters the vessel through the sparger at the bottom of the vessel.
Boiler feed water is sprayed onto the (E) section where it is heated by steam rising from the sparger. The purpose of the feedwater spray nozzle (A) and the preheating section is to heat the boiler feed to its saturation temperature to facilitate the release of the dissolved gas in the following deer sections.
The heated feed water then flows to the deaeration section (F), where it is deformed by steam rising from the sparger system. The gases are stripped out of the water out through the hole at the top of the vessel. Again, some designs may include a vent condenser to trap and recover the gushed water in the released gas. Also again, the ventilation duct usually includes a valve and only enough steam is allowed to escape with the released gases to give a small and visible steam mark.
The deaerated feedwater boiler is pumped from the bottom of the vessel to the steam generator boiler system.
Maps Deaerator
Deaeration steam
The deaerators in the steam generating systems of most thermal power plants use low pressure steam obtained from extraction points in their steam turbine systems. However, steam generators in many large industrial facilities such as oil refineries can use whatever low pressure steam is available.
Oxygen scavenger
Oxygen oxygen scavenging is very often added to deaerated feedwater boilers to remove oxygen remnants that are not removed by the deaerator. The type of chemicals added depends on whether the location uses a volatile or non volatile water treatment program. Most low-pressure systems (& lt; 650psi) use non-volatile programs. Most of the higher pressure systems (& gt; 650psi) and all the systems in which a certain mixed material is present, are now using turbulent programs because the old phosphate-based programs have been removed. The Volatile program is further broken down into oxidation or reduction programs [(AVT (O) or AVT (R)] depending on whether the aquatic environment requires oxidation or reduces the environment to reduce the highly controversial FAC accidents (FAC) in the current industry FAC -related failure has led to many accidents where significant loss of property and life has occurred.
The most commonly used oxygen rinse used for low-pressure systems is sodium sulfite (Na 2 SO 3 ). It is very effective and quickly reacts with traces of oxygen to form a non-scaling sodium sulphate (Na 2 SO 4 ). Other widely used oxygen scavengers diluted properly and for locations using volatile programs are hydrazine (N 2 H 4 ).
Other scavengers include 1,3-diaminourea (also known as carbohydrazide), diethylhydroxylamine (DEHA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), and hydroquinone.
In the stork spray deaerator, the chemical is not required .
See also
- Water preheater
- Economizer
- Feed water heater
- Fossil fuel power plants
- Thermal power plant
- Degasification
- Defoamer
References
[5]
The principle of spray operation is deaerator type
External links
- Water Technology Association
- Design deaerator
Source of the article : Wikipedia
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