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Deaerator or degasser is used to preheat the water entering the boiler and remove insoluble oxygen and carbon dioxide gases. In boilers, it is recommended to avoid the phenomenon of thermal shock in boilers, to always avoid introducing low temperature water into the boiler, because this action, in addition to reducing the efficiency and steaming capacity of the boiler due to the intermittent contact of cold water with hot surfaces of heat transfer, reduces the life of pipes and furnace. Also, since oxygen dissolved in water is always one of the corrosive factors of heat transfer surfaces in boilers, it is recommended to reduce this oxygen by increasing the temperature of the water entering the boiler. The more crane dioxide gas in the water, the pH of the boiler water decreases and the environment becomes acidic, which will be one of the factors that increase the rate of corrosion in boilers.
In order to reduce the insoluble gases in water, the solubility can be reduced to an acceptable level by increasing the water temperature. The solubility of gases in water has an inverse relationship with temperature. The closer the deaerator water temperature is to 100 degrees Celsius, the closer the amount of dissolved gases in the water is to 0 PPm.
In order to increase the temperature of the deaerator water, they use the steam produced by the boiler. This means that a part of the steam of the boiler according to the capacity of the deaerator, the amount of return condensate and the replaced feed water, after reducing the pressure, is introduced to the lower part of the deaerator tower. Also, the incoming water from the condensate tank is poured from the nozzle on the top of the tower onto the heat transfer and mass transfer trays inside the tower. Water is poured on the trays from the top and steam moves from the bottom to the top (reverse flow) and the process of mass transfer and heat transfer takes place on the trays. In simpler terms, after the water passes over the trays, its temperature rises and its insoluble gases decrease.
On the body of the deaerator tank, a number of preheater steam nozzles are considered, so that in emergency situations and when the water temperature of the deaerator suddenly decreases due to the increase of steam consumed from the boiler, the water temperature can be increased to an acceptable level by directly injecting steam into the tank.
It is necessary to install the deaerator at a suitable height and at a calculated distance from the boiler pump in order to prevent possible cavitation in the boiler feed pumps. The working pressure of the deaerator is normally considered to be around 0.5 to 1 bar in order to have the ability to produce water at around 100 degrees Celsius.
It is suggested to consult the experts of Pak Fan Bohar Industries Company regarding the selection of the right size and model for the deaerators. In order to choose the right deaerator (the size of the steam line entering the tower), it will be necessary to declare the amount of return condensate in order to determine the steam required for the deaerator.
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