Water contains significant quantities of gases in balanced conditions with the atmosphere, mainly carbon dioxide and oxygen.
Some industrial plants are required to reduce the concentration of oxygen and carbon dioxide to negligible figures.
Thermophysical deaeration process is normally used for the feed water degassing boiler systems which require decrease of oxygen levels up to a few parts per billion. The dissolved gases are removed in the desorption process, and steam is used as heating environment due to the limited solubility of gases at high temperatures.
On the basis of application of ZEROGAS® technology developed by ARTES, dissolved gases are removed by partial reduction of oxygen and carbon dioxide pressure into a liquid surface with the replacement of steam with air. The contact area increases by spraying liquids falling on metallic trays or structured packing to create a balance between the oxygen and carbon dioxide for liquid and vapor phase. Steam is used as the heater and the separator due to the limited solubility of the gases at a higher temperature.
Therefore while operating with superatmospheric pressure, it is possible to create more favorable conditions for achieving the equilibrium.
Patented ZEROGAS® degassing process is carried out in the deaeration tower where make-up water is sprayed by special structured packings to increase contact surface between water and steam.
Oxygen and carbon dioxide are separated by a steam flow and are removed through the metered orifice or via a throttle valve. The deaerated water enters the storage tank. Operating pressure in the deaerator is maintained by regulation of a steam flow.
In accordance with the designed parameters and steam consumption, deaeration tower can be vertical or horizontal in order to increase the surface of the heat and mass transfer.
Vacuum degassing set
Vacuum degassing is used in cases when it is impossible to warm water or in the absence of steam for degassing. Oxygen and carbon dioxide are removed from the liquid phase by vacuum. In practice reduction of the partial pressure in the gaseous phase is a driving force that takes the dissolved oxygen in the gas phase. The vacuum deaerator ARTES ZEROGAS® is installed at the degassing tower and the storage tank.
Vacuum is created using a liquid ring pump with or without the use of additional pneumatic ejectors in the degassing tower. Water is supplied to the top of degassing tower, then it passes down through metal or plastic rings and accumulates in the storage tank, structure of which is designed to reduce the "residence time" in accordance with the needs of consumers.
In the presence of severe restrictions regarding to the content of residual oxygen in deaerated water, a two-stage tower that operate with two vacuum levels may be used for degassing. ARTES has an extensive experience in the delivery and commissioning of vacuum deaerators in the most challenging conditions.