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Skimmer holds promise for oil collection

A device that can “harvest” an oil spill in open seas or in a marsh — much like a combine harvests wheat and eliminates the chaff — sits as a working concept model at the LSU AgCenter in Baton Rouge, La.

The brainchild of Chandra Theegala, a civil and environmental engineer who has taught fluid mechanics for years, now waits for sufficient resources to bring the concept model to a full-blown working prototype.

Theegala, an associate professor in the LSU AgCenter Department of Biological and Agricultural Engineering, developed the idea in response to the Deepwater Horizon oil spill in the Gulf of Mexico in April.

Theegala’s invention uses a boom to skim surface oil and water through a positive displacement pump and into a container where the oil and water separate naturally. The oil floats up through a pipe into a collection vessel while the water goes another direction and is discharged back to where it came from.

“It relies on the principles of density difference between the two liquids in a u-tube and has no moving parts other than the pump,” Theegala said.

“It works with a commercially available, engine-powered diaphragm pump,” Theegala said. “Unlike other types of pumps that emulsify the oil, the diaphragm pump keeps the oil floating on the water. It works in an up-and-down motion — like chest compression in CPR.”

Theegala’s initial concept model can pump about 4,000 gallons of an oil-water-air mixture per hour. “A fully working model could handle 10 times that volume,” he said. “The material cost on this concept unit is around $7,000 and includes the pontoon unit and the pump.”

Theegala’s concept includes a V-shaped boom that would direct floating oil into the end of the V, where suction from the pump would draw the mixture into the device. “It’s like harvesting oil,” he said. “The oil would be collected in a sack that would float and be collected by a mother ship when it’s full.”

The device would be portable enough to be mounted on a small boat, carried to floating oil on a larger boat, and then lowered into the water where it would begin to do its work.

“It’s just like vacuuming your carpet,” Theegala said. “You follow the oil and suck it up. And you can go back and get what you missed.

“I am confident it will work,” Theegala said of the concept model. “We need to get the word out that we have a low-cost technology that can help in marshes and near an oil rig.”

The inventor sees the technology having applications for shallow marshes and near rigs.

For the marsh locations, the unit would sit up higher, be lighter and even be mounted on a motor boat. It would have a 1- to 2-inch-diameter vacuum hose, almost like a residential home vacuum cleaner, Theegala said.

“These units can be handed to hundreds of fishermen, who can mount them on their boats and clean up the marshes,” he said. “Like bees, each may not bring in a lot, but collectively it can be huge.”

For “near rig” applications, the skimmer would be mounted on an engine-powered pontoon boat that would have a front-end, fixed-V boom that would channel all the oil to the bottom tip of the V while being driven through an oil plume.

“There will be no need for adding any chemical dispersants, and the collected oil would be pure enough for processing,” Theegala said. “Once the floating bags are full, they can be emptied or switched out. A large mother ship can collect all the oil from several skimmers.”

A small prototype made in Theegala’s lab works as planned with 2 to 3 gallons of oil. “But as far as the real thing, we can only say it’s still to be tested in the open ocean. If you have pure crude oil, I am almost 100 percent certain it will work. But if chemicals are added, that changes the flow and density. That’s a different story.”

Theegala said he learned two things from a recent trip to Grand Isle, where the concept model was tested.

“One, the pontoon unit is more than sea-ready and rides like a pro,” he said. “The 3- to 4-foot waves did not bother it, and it was stable. Two, for an open ocean unit, I definitely need a V boom in place of the straight boom on the test model.

“I clearly see a need for steering the running/sucking skimmer unit through a streak of oil,” Theegala said. “Basically, you drive it like a whale with its mouth open and collect oil at the tip of the V. The best part is it can take in any combination of water, oil and air and deliver them from three different ports.”

The final hurdle, Theegala said, is finding the resources to develop a full prototype on a fast track to get skimmers into the Gulf and marshes. His model is currently positioned in the Gulf awaiting help from an agency or company that has the capabilities to test it in floating oil, he said.

“Dr. Theegala has worked very hard in a short period of time to get this designed, built and tested,” said David Boethel, vice chancellor and director of research for the LSU AgCenter. “I hope he is successful.”


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