Deoxygenization methods to feed water include thermal deoxygenization and chemical deoxygenization. By thermal deoxygenation, most of the dissolved oxygen in water can be resolved and removed, by chemical deoxygenation,  the residual dissolved oxygen that is hard to remove by thermal deoxygenation can be removed. 

Principle of thermal deoxygenization According to the law (Henrry Lay) of gas dissolving, the solubility of any gas in water shall be direct ratio with partial pressure of the gas on interface of gas and water. When water is heated, with the increase of water temperature，the partial pressure of water vapor on the gas-water interface increases, the partial pressure of the gas decreases, so the solubility of various kinds of gas in water is reduced. When the water is boiling, the water saturated vapor pressure is equal to the atmospheric pressure, the partial pressure of the other gas is zero. Therefore all the gas can't dissolve in water, various kinds of gas care separated in water, this is the principle of thermal deaeration.