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Boiler technology / Why should the boiler feed water be deoxygenated?What methods are there?
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Boiler technology / Why should the boiler feed water be deoxygenated?What methods are there?

Views: 0     Author: Sifang Boiler     Publish Time: 2018-03-27      Origin: Site

 Why should boiler feed water be deoxygenated?What methods are there?

Oxygen corrosion is the most common and serious corrosion in boiler systems.Since the water supply is generally in contact with the atmosphere, the dissolved oxygen in the water is basically saturated, so the pipelines and equipment that the water supply flows through may have the possibility of oxygen corrosion.

The forms of oxygen corrosion are generally ulcer-type corrosion and pinhole-type localized corrosion, so this kind of corrosion damages the strength of metal components very seriously.From the analysis of the causes of industrial boiler damage and scrapping accidents in the country, due to the poor deoxidation of boiler feed water, causing corrosion and damage, scrapping or tube bursting is proposed, accounting for a considerable proportion.Therefore, in order to eliminate the corrosion and harm of dissolved oxygen to the boiler water vapor system, the national standard stipulates that for boilers with an evaporation greater than 2t / h , the feed water should take deoxidation measures, and according to the different working pressure of the boiler, the dissolved oxygen in the feed water should be controlled within within the qualified range.

At present, the deoxidation methods of boiler feed water mainly include thermal deoxidation and chemical deoxidation.

 

 

What are the characteristics of thermal deoxygenation?

Thermal deaeration has the following characteristics:

①The thermal deoxygenation method can not only remove oxygen, but also remove gases such as CO2 NH3 H2S , etc., and reduce the corrosive effect of these gases on the boiler water vapor system.

②The deoxidizing effect is stable, and the oxygen content in the feed water after deoxidizing can be reduced to O .01mg / L or less, and promote the decomposition of bicarbonate in water and reduce the total amount of carbonate compounds in water.

③Do not pollute the water quality.

④It needs to be heated by steam and consumes a lot.

How does thermal deaeration work?

The atmosphere is mainly composed of nitrogen, oxygen, carbon dioxide, water vapor and a small amount of other gases, and the atmospheric pressure is the sum of the partial pressures of the various gases that make up the atmosphere.

According to the law of gas dissolution ( Henry's law ) : the solubility of any gas in water is proportional to the partial pressure of the gas at the gas-water interface, regardless of atmospheric pressure.That is to say, the dissolved oxygen content in water is only related to the partial pressure of oxygen in the atmosphere.

When water is heated to boiling in the atmosphere, the saturated vapor pressure of water is equal to the atmospheric pressure at the air-water interface, and the partial pressure of oxygen is equal to zero.At this time, the solubility of oxygen in water drops sharply and is removed from the water, which is the principle of thermal deoxygenation. 

Source: Polaris Fire Electric Man

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