Oxygen is an oxidizer. It will react with anything organic, or combine with metals and salts in water, which in the case of food or beverages will affect the taste, odor, and shelf life of a packaged product. In regards to hot water or steam production systems, the oxygen will aggressively react with metals in the heated environment to cause corrosion to heat exchangers and piping. Many hot water system owners must add expensive oxygen scavengers to displace the dissolved gas and prevent harmful corrosion.
Using a mechanical deaerator for oxygen removal can be both more practical and economical in hot water and steam systems in lieu of using oxygen scavengers and other chemicals. Breweries use de-aerated water to ensure shelf life and taste in their canned and bottled products. Food plants that package fresh vegetables may use de-aerated water to improve taste, color, and extend shelf life.
One method currently used to produce de-aerated water uses membrane filter systems. Systems are sized and priced at various capacities in terms of gallons per minute. These systems require a 7.5 HP or larger vacuum pump. The membrane filters require regular maintenance and or replacement depending on the purity of the water source. Membrane filter systems are labor intensive to clean and sanitize in food or beverage plants.
Other more mechanized systems use boiling water and vacuum pumps to remove the oxygen from the water. These types of system have high energy consumption and are priced per GPM of de-aerated water required. These types of systems are common in coal and gas power plants where heat transfer efficiencies need to be optimized.
Fortrans Inc. has developed a new way to produce low cost de-aerated water by integrating our patented Dif-Jet gas injector into batch production of de-aerated water in storage tanks.
The Dif-jet device is used to efficiently inject and mix nitrogen gas into a pressurized water pipe and then discharged into and circulated in a tank of water. The nitrogen, being highly soluble in water, will force the oxygen out of the water without requiring a vacuum pump, heat or other device. The oxygen is vented out of the top of the tank automatically.
Fortrans conducted testing using a 500 gallon closed head polyethylene tank with a single Dif-jet gas injector. A ¾ HP circulation pump is connected to the injector piping that is connected to the intake and discharge fittings on the tank. The injector is connected to a regulator installed on a standard 300 cubic foot cylinder of nitrogen gas. Paired with a nitrogen generator, this system can provide a continuous stream of de-aerated water at nearly half the cost of membrane filter or vacuum pump systems.
The nitrogen gas injector was fed 5 CFM of nitrogen @25 psi to produce 500 gallons of de-aerated water in 25 minutes. The treated water had a dissolved oxygen content of less than .1 mg/L.
Faster de-aeration times can be achieved by using a manifold of 2 to 4 Dif-Jet gas injectors to de-aerate larger treatment tanks and maintain a constant supply of de-aerated water. A dissolved oxygen controller may be used to produce a constant supply of water at low DO levels.