Electrifying research destroys pollutants that cause smog

Laurent Belsie

Tuesday, June 18, 1996 | 11:59 a.m.

Cars aren't the only things that cause smog and urban pollution. So do industrial plants and hazardous-waste dumps.

For years, researchers have worked on ways to reduce the smog-inducing gases spewing from plants and dumps. They've burned them, filtered them, even used platinum and other expensive catalysts to turn them into more benign substances. Louis Rosocha of the Los Alamos National Laboratory thinks he has a better idea.

He electrifies them.

If he's right, engineers could soon have a new way to handle problematic gases that is cheaper than filtering or catalytic conversion and creates fewer environmental problems than incineration. The process is called plasma technology. This plasma is an electrically charged gas cloud, not the gooey stuff of science fiction movies.

Actually, its formal name is nonthermal plasma technology, because it uses electricity instead of heat to work its magic. Similar processes are being tested abroad to control sulfur- and nitrogen-oxide emissions from industrial plants, the gases that can lead to smog and acid rain. At Los Alamos, Dr. Rosocha is using it on volatile organic compounds or VOCs, which are hazardous air pollutants in their own right and can lead to smog and acid rain.

Last November, scientists at the lab and their industrial partner, High Mesa Technologies in Santa Fe, N.M., set up an instrument-filled trailer at a contaminated site at McClellan Air Force Base in California. The 40-year-old site had been a dumping ground for gasoline and various industrial solvents.

For two months, the Los Alamos scientists used their plasma technology to see how well it could clean up the fumes.

The results were impressive. Their system destroyed 95 percent of the average VOC gas. The level of destruction reached 99.9 percent for trichloroethelyne (or TCE, a dry-cleaning fluid).

In March, the researchers moved their system to another contaminated site at Tinker Air Force Base in Oklahoma. There the plasma technology proved itself capable of handling the site's low concentrations of contaminants as well as sites with high concentrations, such as McClellan, according to Rosocha.

It works like this: The contaminated gases are sucked up by an industrial vacuum that sends the polluted air to the plasma machine. The air flows through the machine in long "sheets" only one-eighth of an inch thick. This makes it easy for the machine's electrodes to charge the gases with electrical energy.

The new electrons in the gaseous cloud break apart oxygen molecules into two oxygen atoms, one of which reacts with the water vapor also present in the gas mix. This creates a powerful agent called a hydroxyl or free radical. In the case of the TCE gas, this agent breaks apart its tightly bound molecules.

This reaction sets off a chain of events that eventually turns an unfriendly gas into much more benign compounds, such as hydrochloric acid, carbon dioxide, and carbon monoxide. The acid can be easily neutralized with baking soda. And while carbon monoxide is toxic in large doses, the process creates such small amounts it can often be vented harmlessly into the atmosphere.

Rosocha says the process probably will never be cost-competitive with incinerators. And it handles only vapors, not the physical scrap that incinerators do. Its big advantages over incinerators are that it doesn't burn huge quantities of fuel and it doesn't create dioxins and other troublesome byproducts.

If the lab's industrial partner can commercialize the process, it could provide an important new way of dealing with environmentally harmful gases that choke our cities and forests with smog, acid rain, and other hazardous air pollutants.