Deaeration of two types namely Mechanical Deaeration and Chemical Deaeration. Mechanical deaeration works on the principle of Henry’s law of physics. Removal of oxygen, carbon dioxide and other non-condensable gases from boiler feed water is vital to boiler equipment longevity as well as safety of operation.
Deaeration is the removal of dissolved or entrained gases from water to be used as boiler feed or for other processes. The gases of concern to steam plant operators are usually oxygen and carbon dioxide which are present in water due to natural cases.
Oxygen and carbon dioxide present in untreated water cause corrosion of the usual boiler and steam plant materials. The rate of the corrosive action is proportional to the amount of the gas present in the feed water and is accelerated by high temperature.
Working principle of Deaerator
Oxygen and carbon dioxide present in untreated water cause corrosion of the usual boiler and steam plant materials. The rate of the corrosive action is proportional to the amount of the gas present in the feed water and is accelerated by high temperature.
Working principle of Deaerator
The primary purpose of deaeration is to remove the dissolved oxygen and carbon dioxide from water to such low levels that their corrosive potential with regard to carbon and low alloy steel is eliminated under the temperature and pressure conditions prevailing in steam generation and transport equipment. The economic value of being able to use steel, rather than higher alloy, materials for construction of steam plant equipment is easily recognized.
A deaerator is a device that is widely used for the removal of oxygen and other dissolved / non condensable gases from the feed water to steam-generating boilers. Inparticular, dissolved oxygen in boiler feed waters will cause serious corrosion damage in steam systems by attaching to the walls of metal piping and other metallic equipment and forming oxides (rust). Water also combines with any dissolved carbon dioxide to form carbonic acid that causes further corrosion. Most deaerators are designed to remove oxygen down to levels of 7 ppb by weight (0.005 cm³/L) or less.
Methods of Deaeration
Deaeration of water can be achieved by chemical and/or mechanical means.Various chemicals are available which react with the oxygen in water to produce chemical formsthat are not harmful to the steam system. Likewise, there are chemicals that can be added to thewater to react with carbon dioxide and transform it into neutral forms of the substance.Non-chemical (mechanical) methods of deaeration remove, rather than transform, the oxygen and carbon dioxide present in the water supply. Mechanical deaeration devices function by reversing the mechanism by which the gases initially go into solution with water.
A deaerator is a device that is widely used for the removal of oxygen and other dissolved / non condensable gases from the feed water to steam-generating boilers. Inparticular, dissolved oxygen in boiler feed waters will cause serious corrosion damage in steam systems by attaching to the walls of metal piping and other metallic equipment and forming oxides (rust). Water also combines with any dissolved carbon dioxide to form carbonic acid that causes further corrosion. Most deaerators are designed to remove oxygen down to levels of 7 ppb by weight (0.005 cm³/L) or less.
Methods of Deaeration
Deaeration of water can be achieved by chemical and/or mechanical means.Various chemicals are available which react with the oxygen in water to produce chemical formsthat are not harmful to the steam system. Likewise, there are chemicals that can be added to thewater to react with carbon dioxide and transform it into neutral forms of the substance.Non-chemical (mechanical) methods of deaeration remove, rather than transform, the oxygen and carbon dioxide present in the water supply. Mechanical deaeration devices function by reversing the mechanism by which the gases initially go into solution with water.
Mechanical O2 removal:
Removal of dissolved oxygen to very low limits, not exceeding 7 ppb, is possible by mechanical deaeration only. According to common boiler standards, lower concentrations than 7 ppb are usually not relevant for operation.
Removal of dissolved oxygen to very low limits, not exceeding 7 ppb, is possible by mechanical deaeration only. According to common boiler standards, lower concentrations than 7 ppb are usually not relevant for operation.
Mechanical CO2 removal:
In general, mechanical deaeration can remove all free CO2 to a non-detectable level. Dependent on actual pH value of the condensate, chemically bound CO2, which cannot be completely removed by mechanical deaeration, may be present in the water. However, since the level of CO2 present in treated water seldom exceeds 5 ppm, no further discussion of CO2 removal will be addressed in this bulletin and the remainder of this paper will address only oxygen removal via the deaerator technology.
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