Como Academy

July 10, 2019

Air Stripping Versus Vacuum Pumping

Air stripping technology is what allows COMO’s Oil Recycling Systems to remove water and achieve dryness levels with lower costs, complexity and energy use. 

The addition of air stripping technology to our recycling systems makes it possible to economically dry oils that tend to retain emulsified water. With air stripping, you can easily achieve water removal rates of greater than one gallon per hour and final dryness levels of less than 40 parts per million. 

What Is Air Stripping?

Air stripping is a “mass transfer” operation using dry air as a conveyor belt to remove water from oil. The oil is heated to 150 °F or more, and finely dispersed air is injected. The air is immediately heated to the temperature of the oil, which lowers its relative humidity and allows it to absorb up to its own weight in water—or more.

The higher the temperature of the oil, the greater the amount of water the air can remove. The rate of water removal with air stripping is determined by the temperature of the oil and the amount of airflow. Five cubic feet per minute of air with an oil temperature of 160 °F will remove one gallon of water per hour. This process also removes other volatile contaminants.

How Does Air Stripping Compare to Vacuum Purifying?

COMO’s air stripping systems are built on the foundation of our Oil Recycling Systems, which all feature an integral oil reservoir. The energy savings associated with using this oil reservoir, instead of drying the oil in place, allows COMO Oil Recycling Systems to operate at volumes unmatched by vacuum systems. Oil temperatures are about the same in both processes, and oil oxidation is generally not a factor at these temperatures—given the short exposure times involved.

Vacuum purifiers draw the oil from the sump through a heater, pass it through the vacuum chamber, and discharge it back to the sump while still hot. If the sump is large, most of the heat added to the oil is lost in the reservoir. Most vacuum systems are not equipped with heaters capable of raising the oil temperature more than 50°F per pass. If the heat loss in the sump is excessive, the oil temperature will never reach the required 150 °F.

The energy required to raise a 5 gallons per minute flow of oil from an ambient temperature of 70 °F to the minimum required temperature of 150 °F in one pass is in excess of 21 kilowatts (72,000 Btu). At many locations, this amount of electrical power is not available.

In contrast, COMO’s Model 2000 Air Strip Recycling System can handle 100-gallon batches of oil with only 6-kilowatt heaters, which require only 25 amps at 240 volts single phase or 14.5 amps at 240 volts 3 phase. The amperage requirements at 480 volts will be half these numbers. Compare energy requirements, initial cost, simplicity, or quality of final product. COMO Air Strip Recycling Systems come out on top.