Plasma Progress Presents Possibilities for Pummeling Pollution
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Imagine a small magic box which, attached to the bottom of every bus, truck and automobile, could take in toxic gas and convert all that blue and brown smoke to clean air.
Scientists and engineers are advancing toward this goal with studies of how to use plasma physics to eliminate some of the worst sources of sickening smog and corrosive acid rain. Years of basic research have provided progressively more understanding of the physics and chemistry of plasmas, a kind of free-for-all cloud of electrons, ions, neutral atoms and molecules all slamming into each other and interacting with other atomic particles in the environment. Glowing neon lights, bursts of lightning, crackling static electricity and the flash from an engine's spark plugs are all plasmas in action.
Plasma remediation was identified as a promising technology for treating contaminated gas streams and air at the First International Symposium on Advanced Oxidation Techniques in 1993, sponsored by the National Science Foundation (NSF) and the Electric Power Research Institute. This is because plasmas do more than sparkle; they cause a blizzard of chemical reactions. Many university researchers are now investigating whether plasma-powered chemical reactions can help cut belching diesel fumes.
"The challenge is to develop plasma generators that will convert toxic emissions into benign or more treatable products quickly, safely and economically," says NSF-funded engineering professor Mark J. Kushner of the University of Illinois UrbanaChampaign, who is developing computer models to determine how well plasma generators can do the job. He is collaborating with researchers at Los Alamos National Laboratory and the University of Southern California to validate the models which industry could adopt to design practical manufacturing systems.
"Advances in computer modeling of plasmas have saved some industries such as lighting and microelectronics months and possibly years of trial-and-error manufacturing design," Kushner says. "We hope to transfer that technology to using plasmas for solving environmental problems."
Catalytic converters for automobile gasoline engines process toxic compounds such as nitrous oxides into harmless gases. In diesel engines the conversion isn't complete because particles and unburned hydrocarbons in diesel engine exhaust can dirty the surfaces of conventional catalytic converters. Kushner's work aims to finish the task by processing the toxic gases using a plasma directly in the exhaust.
In a plasma generator, high voltage from a vehicle's generator passes into a metal cylinder by way of an electrode. Kushner is using his computer models to find the right combination of factors - variables such as voltage, electron acceleration and electrode dimensions -- to create a burst of free electrons that can lock and unlock chemical bonds and disarm emissions.
Plasmas for truck exhaust must be economical, Kushner says, because calculations indicate that if more than 10 percent of a truck's engine power is needed to run a plasma generator, engineers are better off redesigning the engine.
Other industries are already generating plasmas to reduce toxic emissions and recycle captured compounds. In coal burning power plants, for example, nitrogen oxides can be split up and reformed as nitrogen, oxygen and nitric acid. The nitrogen and oxygen can be released safely into the atmosphere while the nitric acid can be combined with ammonia to make fertilizer. A more difficult challenge is how to safely convert large volumes of fumes emitted by chemicals used by, for example, dry cleaners and auto body shops. Here the chemical conversions within the plasma are more complex and volatile. Improvements in plasma research also are important to the semiconductor chip industry, which uses plasma generators in manufacturing. Better computer simulations of plasma technology could lower the cost of producing computers, microwave ovens, cellular phones, fax machines and hundreds of other products that depend on computer chips to operate.
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2017, its budget is $7.5 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives more than 48,000 competitive proposals for funding and makes about 12,000 new funding awards.
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