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Samah Ringa
BWT Permo
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Since about ten years, a new trend is observed for using membrane contactors for food industry. Such equipment are often used for adjusting the alcohol degree in Australia and the US, for adding gas in the soft drinks industry, or else in the treatment of beer or carbonated waters.
Nowadays, the membrane contactors are used to remove gas from liquids in microelectronics, food industries, photography and ink.
As they meet the FDA requirements, they are more integrated in pharmaceutical applications to eliminate the dissolved CO2 in the water treatment systems.
In order to achieve the pharmacopoeia quality criteria and guarantee a right conductivity at the points of use, the total dissolved CO2 content must be reduced to very low rates, down to a few ppm only.
Purified water production systems mostly integrate membrane techniques, especially reverse osmosis. But this solution does not remove gases that are naturally dissolved in water.
Today, the most implemented process to eliminate carbon dioxide is to inject soda upstream of a reverse osmosis unit. This technique is used to turn, by chemical way, dissolved CO2 into salts that could be retained by reverse osmosis membrane.
The use of such a chemical product requires strict procedures in terms of handling, preparation and storage.
In the production water systems for pharmaceutical or cosmetic use, membrane contactors bring an innovative solution instead of the chemical treatment by soda injection.
This process includes a technology based on the Henry law that governs the liquid-gas exchange.
Membrane contactors consist of hydrophobic and microporous membrane. The membrane enables exchanges between the water to be treated (which circulates tangentially) and filtered compressed air (introduced under pressure).
The contactors operate by lowering the pressure of gas in contact with water to create a conductive force to remove dissolved gases.
Indeed, acting on the partial pressure gas phase, it is possible to extract the gas dissolved in the liquid phase, regardless of the initial content and the result desired. To achieve this result, 2 configurations are possible :
This technique can be used as unique equipment to eliminate CO2.
The running of such a system is convenient since it requires no regulatory device.
Furthermore, it is totally flexible in regards to its implementation.
The size of such equipment is quite small. It is easily integrated thanks to its modular configuration.
It can also upgrade an existing installation to increase its performance or replace the soda injection system.
More, awareness of environmental protection industries allows them to reduce the use of chemical products in their processes.
In conclusion, industries now have a solution alternative and effective not only to technical requirements related to the production of purified water but also to their expectations in terms of respect for the environment.
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