A Turning Point in Oil Spill Recovery

By Linda Henning

Spill Response: Elastec’s Grooved Skimming Technology

Cleaning up marine oil spills can be a challenge as there are various types of oil spilled but only a few effective recovery methods. The three main technologies for oil spill recovery for inland and offshore waters are mechanical, insitu burning (ISB), and dispersant application. Absorbent booms and pads may also be used, but they are more effective for small fuel spills.

Mechanical recovery, usually an oil skimmer, is a device that skims contained floating oil and transfers the recovered oil to a storage container or vessel. Selecting the appropriate oil skimmer depends upon the oil’s viscosity, slick thickness, adhesive characteristics and weathering properties. Sea states and the ability to access and encounter the oil are also important factors, among others. It is possible that more than one type of skimmer may be needed on a single spill.

No “One-size-fits-all” Skimmer

Since there are various types of oils, from crude to refined, as well as various types of environmental conditions, there is no “one-size-fits-all” skimmer. Oil viscosity is one of the most critical parameters affecting a skimmer’s recovery performance. At opposite ends of the viscosity spectrum are light and heavy oils. Gasoline and diesel fuel as well as Bakken crude are light oils. They spread and evaporate quickly. Heavy oils, such as bunker and bitumen, are more viscous and can cause more environmental harm as they linger longer and may even sink. Medium viscosity oils are, well, in the middle and are somewhat easier to recover mechanically.

Oil skimmers come in all sizes, configurations, combinations and materials: drums, discs, ropes, brushes, belts, weirs, suction, aluminum, steel, polymer, pneumatic and hydraulic. Oleophilic polymer skimmers generally recover a higher ratio of oil relative to water and are also effective in recovering medium viscosity oils. In 1990, Elastec, an environmental equipment manufacturer in Carmi, Ill., perfected the oleophilic smooth drum skimmer which remains an industry standard today due to its high oil recovery rate and recovery efficiency (oil-to-water ratio).

Grooved Drum Skimmer

In 2005, at the University of California’s Bren School of Environmental Science and Management in Santa Barbara, a graduate student with an interest in oil spill recovery and Dr. Arturo Keller were theorizing that by adding grooves to the surface area of a drum skimmer, the volume of oil recovery could possibly be increased.

Working with Elastec, the team tested both smooth and grooved drum surfaces in oil at the National Oil Spill Response Test Facility (OHMSETT) in Leonardo, NJ. The results concluded: “The use of a proposed grooved pattern can increase the recovery efficiency up to 200%. The grooved pattern was proven to be efficient even on diesel, which is a challenging product to recover due to its low viscosity. The recovery efficiency of a grooved surface can be additionally improved by tailoring the groove dimensions to specific oil properties for a particular region and climate.”

Armed with research, testing and a patent, Elastec developed a commercial version of a grooved drum skimmer which proved to be effective with both light to medium oil types.

Award-Winning Grooved Disc Skimmer

On April 20, 2010, a violent explosion occurred in the Gulf of Mexico approximately 42 nautical miles offshore from Southeast Pass, Louisiana. The fiery blast was caused by an underwater blowout from the Deepwater Horizon drilling rig, gushing millions of gallons of Louisiana crude into the Gulf. Eleven lives were lost and numerous others were injured. It was the worst offshore oil spill in U.S. history.

Elastec’s Hydro-Fire Boom and American Fireboom systems were two of the most effective Insitu Burning (ISB) technologies in the Gulf Spill. However, it was noted that mechanical oil spill recovery techniques in the Gulf had not changed significantly since the 1989 Exxon Valdez spill in Alaska.

Elastec had been contemplating transferring its grooved skimming technology from a drum to a disc to recover even higher volumes of oil before 2010. However, the demand for such a high-volume skimmer was non-existent; therefore, the research and development investment did not have an attractive return potential – until the Deepwater Horizon incident.

Philanthropist Wendy Schmidt and the X Prize Foundation also saw the need for an improvement in mechanical oil spill recovery in the aftermath of the disaster and developed the Wendy Schmidt Oil Cleanup X CHALLENGE with a one million dollar first place prize. The Challenge was “designed to inspire a new generation of innovative solutions that will speed the pace of cleaning up seawater surface oil resulting from spillage from ocean platforms, tankers, and other sources.” Elastec saw the prize as an incentive to recoup R&D expense and developed a prototype skimmer with 64-grooved discs. The effort paid off as Elastec won first place by recovering 4,670 gallons of oil per minute with an 89.9% efficiency.

Scalable Grooved Disc Skimming Technology

Elastec’s award-winning and patented Grooved Disc Skimming technology was scaled to develop several commercial skimmer models to accommodate a range of realistic spill scenarios. Its workhorse, the X150 Grooved Disc Skimmer, has ten discs offering a high oil encounter and recovery rate in advancing or stationery modes. Tested at Ohmsett, the X150 has an oil recovery rate (ORR) of 660 gallons per minute (150 cu m per hour) and an oil recovery efficiency (ORE) of 87.6%.

For offshore and open water spills, the X150 Launching System is a turning point in mechanical oil spill recovery technology with its fully integrated remote controlled X150 skimmer launcher, complete with boom and reel, BoomVane (for one vessel towing), power unit and hydraulics – a turnkey operation to quickly load onto service vessels for rapid high volume spill response.

The X30 and X45 Grooved Disc Cassettes have two and three discs, respectively, for bow and side skimming operations. The X30 configuration was recently tested at Ohmsett in light oil in advancing mode, up to two knots with impressive results. The Grooved Disc Cassettes are more effective than brush skimmers in picking up light oils such as Bakken.

An evolution in skimmer technology, Elastec’s grooved discs complement its grooved drum skimmers as they both have their advantages. Additional performance tests were conducted at Ohmsett recently on Elastec’s Magnum 200 grooved drum skimmer. The 4-drum device can recover a wide range of oil types. Even with its larger design for inland, harbor, open water and offshore recovery, it is lightweight and easy to deploy, as are all Elastec skimmers.

Verification of Nameplate Claims & System Performance

Although simulated testing (such as at Ohmsett) to verify skimmer nameplate oil recovery rate is important, the overall skimmer “system” performance should be evaluated as well. Oil encounter rate, throughput efficiency, pump capacity, water volume collected, storage capability and even how much oil was not recovered are critical to the complete mechanical oil recovery process. The Bureau of Safety and Environmental Enforcement (BSEE) provides an Estimated Recovery System Potential (ESRP) calculator for evaluating mechanical skimming systems.

(as published in the October 2017 edition of Marine News)

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