For decades, air bubbles have been used to blend lubricants, additives and many other substances quickly and efficiently. Methods can range from a simple, handheld air sparge that blows compressed air or gas through a single drum of fluid, up to a 20-foot array that agitates the contents of an entire bulk storage tank. The Pulsair system of tank-bottom air release has legions of adherents worldwide, while the newest player on the field is an Eastern European start-up that calls its technology cavitation cold blending lubricants (CCBL).
One of the earliest examples of in-tank air blending LubesnGreases has seen is still operating at Tokyo-based Japan Sun Oil, which adopted a proprietary dry air method in the mid-1960s. According to Anna Hiramatsu, the companys executive director for international, the system blows dry air from the bottom of a blending tank. She called it particularly useful for specialty lubricants – like refrigeration oils – that have a very low tolerance for impurities that might be introduced through mechanical mixing.
Probably the most widely known and established air blending company is Bellevue, Washington-based Pulsair Systems. Incorporated in 1987, the custom engineering company has completed more than 160 installations for over 80 companies around the globe, in industries ranging from oil to pharmaceuticals to food processing.
Business is still in full swing, demonstrating that lube companies the world over recognize the value of bubbles in blending. Kleen Performance Products (the newly renamed finished lubricants business of Safety-Kleen) included a Pulsair system in the blending plant it built in East Chicago, Ind., in 2012. In an interview with LubesnGreases, Pulsair founder and president Dick Parks said the company has recently completed lube blending installations for Savita in India and Q8 in Belgium. More projects are underway for ExxonMobil and Infineum in Singapore, packaging company Schutz in Mexico, and Oscar Lubricants in the United Arab Emirates.
Pulsair blending systems involve a set of plates placed along the bottom of the bulk liquid tank or container. The number of plates ranges from just one (in a typical cone-shaped tank) to 100, as in a wastewater treatment facility in Fayetteville, North Carolina. The standard number is seven, which can blend products in tanks up to 30 feet in diameter. Each plate releases a timed pulse of compressed air that sweeps out between the plate and the floor of the tank and collects above the plate into a large, slow-moving bubble.
As the bubble rises to the surface, a vacuum is created that pulls the heavier bottom liquids and solids up with it, the companys website says. It also pushes the liquid above it up and out towards the tank perimeter. This action creates vertical circulation of the entire tank contents and the appearance of a bubbling cauldron. The company says this way of mixing is about 10 times faster than using mechanical mixing arms.
No additional pressure is applied to jet the liquids, and no additional heat is needed. According to Parks, a Pulsair system can start with the liquid at any temperature, and the heat transfer from the process can cut in half the time typically needed to drain a tank.
One potential concern for air blending systems is air entrainment. According to its website, Pulsairs large bubbles actually remove entrained air rather than adding it. Over all, the company says, Pulsairs blending method is more efficient, uses less energy and requires less maintenance than mechanical mixers.
Instead of releasing one single, large bubble at a time, Russian-Polish firm GQOil Innovation Europe favors a plethora of faster, smaller bubbles. Its cavitation cold blending lubricants project began as a prototype five years ago, and the concept dates to 2007, according to Sergey Medyansky, the inventor and patent-holder. The start-up has received a few innovation awards and development grants in Russia and abroad from such institutions as Skolkovo Technology Park near Moscow, and Russian bank VEB, Medyansky said.
CCBL technology uses high pressure to create thousands of microscopic bubbles. This technology can be simply described as imploding air bubbles in the cavitation zone that can mix the components on a molecular level, Andrzej Chodyniecki, chief operating officer of GQOil, told LubesnGreases in a series of interviews in September and October.
For this method, base oils and additives are blended in recirculation mode in a pre-mix tank. This premix then is fed into the CCBL units columns, for processing in cavitation blending mode. Here, the liquid is pumped at high velocity through a set of holes. As the liquid exits the holes under pressure, it releases air bubbles. The bubbles rapidly collapse due to the pressure of the surrounding oil, generating a burst of energy that disperses and homogenizes the ingredients.
Chodyniecki explained that collapsed bubbles generate a jet of surrounding liquid and produce intense local heating, high pressures, and intense heating and cooling rates. The effect lasts only a few microseconds, and because it is confined to a microscopic level, the temperature of the whole premix increases only by 2 or 3 degrees C. at output. The finished tank is then deaerated through mechanical mixing.
GQOil boasts that its technology produces on-spec finished product every time, unlike mechanical mixing. If dosages are made correctly, the finished lube results are perfect, Chodyniecki declared.
The main advantage of CCBL, he continued, is faster mixing at lower temperatures. Reduction of the time increases the throughput, and reduction of the temperature decreases the energy costs. Both performance indicators are key factors for any lube blending process, he explained.
GQOil is based in Warsaw, Poland, where temperatures hover below freezing in winter. CCBL technology allows blending to be performed at about 20 degrees C., versus the 40 to 60 degrees needed in conventional mixing processes, according to Chodyniecki.
To implement its technology, GQOil partnered with lubricant producer Prista Oil, which invested in construction of a test module at its 110,000 metric tons per year blending plant in Ruse, Bulgaria. The installation increased the plants capacity by 5,000 t/y, and Prista management expects to add more such capacity in the near future.
Our rationale was not so much to increase the plants capacity, but rather to test and implement the CCBL technology, said Milen Boychev, executive director of Prista Oil.
Air mixing systems also offer the advantage of being easily adapted, customized and installed in either stationary or mobile versions. In addition to large-scale installations, Pulsair has made a lightweight 55-gallon drum mixer, IBC tote mixers and rail tankcar mixers. We can custom engineer and build air mixing systems for any size mixing tank, vessel or tank farm, the company says.
The customization options have appeal beyond the lubricants field, too. Winemaker Robert Mondavi uses a specialized Pulsair bubble system to manage the pace of fermentation in its tanks, wet the grape skin cap to extract more color and flavor, and keep the yeast evenly distributed. Diving teams at Ohio State and Calvin College train in swimming pools that are upholstered with remote-controlled bubbles to soften the impact of their dives. People everywhere consume foods mixed on Pulsair equipment, including from Hersheys, Heinz and Tabasco.
CCBL technology also is scalable, and mixing capacities range from 6 to 30 metric tons per hour. The mobile version fits into a 20-foot shipping container (or a 40-foot container including control room and lab), so it can be transported to smaller or off-shore sites. GQOil and Prista are working to further develop the system as an integrated dosing and blending unit.