Study: A Fire Tornado Could be Used to Clean Up Oil Spills

When the worst large-scale oil spills happen, responders turn to methods that have tradeoffs. Dispersants make the visual problem go away, causing the slick to break up and disappear into the water column before reaching shore, but have environmental effects. Burn-offs - intentional or accidental - reduce the volume of concentrated oil pools on water, but they also generate toxic smoke. A new study by a team at Texas A&M suggests that oil burn-offs can be carried out far more efficiently if the burning pool is subjected to a vortex of swirling air, known to wildland firefighters as a "fire whirl" or "fire tornado."

For first responders in wildland firefighting, the fire whirl evokes risk: the burning tornadoes can increase spread rate in a forest fire or move erratically, potentially overrunning fire teams. But that extra intensity might also be an asset, if it could be harnessed. A team led by by Dr. Elaine Oran and Dr. Qingsheng Wang of Texas A&M and Dr. Michael Gollner of UC Berkeley set out to determine whether a fire whirl could do a better job at burning off crude oil, and they found success.

The team set up a test apparatus at a firefighting experiment lab to see how a fire whirl would work over water. They arranged a set of three walls in a triangular formation around their test-scale oil fire, thereby inducing circular air movement - a vortex - as air flowed through the gaps between the walls and into the interior chamber. It worked, and they got a clean-burning pillar of flame.

According to their results, the whirl burned off 95 percent of the oil in the trial pool, and it produced 40 percent less soot in the process. In a cleanup scenario, this would mean far less toxic mess left behind. Best of all, it does its work in half the time of a normal burn-off fire. In spill-response, speed is everything, as the goal is to slow the spread of the slick.

“This the first time anyone has conceived using fire whirls for oil spill remediation, and it’s really just the beginning,” said Dr. Oran, who is an aerospace engineer. “Our goal is to harness the chaotic nature of fire whirls as a powerful, precise restoration tool."

There are limits, though. In deeper pools of fuel, the fire caused the underlying water to boil, resulting in water vapor that extinguished the fire early, the team found. The impact of high or gusty wind conditions was not assessed, so for now, the findings have more relevance for calm conditions. And as a practical matter, the mechanics of inducing a vortex and creating a fire whirl on the water are not yet clear.

"The experimental setup, involving three walls to generate fire whirls, is not directly applicable to open ocean environments where large oil spills typically occur. Future research should explore applicable methods for inducing fire whirls in open water conditions, possibly through the use of mobile or deployable structures, or by leveraging natural atmospheric conditions fitting for fire whirl formation," the team concluded.