New process KOs all NOx.

New Process KOs All NO.sub.x

Pollution control engineers have had adifficult time and only limited success in battling nitrogen oxides, or NO.sub.x.. Produced by combustion, these gases play a major role in the formation of both smog ozone and acid rain. But a scientist has invented a chemical process that is "capable of completely removing NO.sub.x from the products of combustion," according to a newly published paper by researchers at Sandia National Laboratories in Livermore, Calif.

The anti-NO.sub.x discovery, by Sandia'sRobert A. Perry, is an offshoot of his research into the fundamental chemistry of hydrocarbon combustion. The new finding involves mixing combustion gases with isocyanic acid (HNCO), a gas formed when the nontoxic cyanuric acid, or (HNCO).sub.3., is heated. In a series of rapid chemical reactions that have not yet been fully characterized, the HNCO will mix with nitric oxide (NO), for example, forming elemental nitrogen gas, carbon monoxide, carbon dioxide and water vapor. In a laboratory test with the exhaust from a small diesel engine, the HNCO treatment was capable of removing more than 99 percent of the nitrogen oxides present in the untreated exhaust, according to a report by Perry and Dennis L. Siebers in the Dec. 18 NATURE.

This process "will work, as far as weknow, for any process that uses hydrocarbons for combustion," Perry says. And unlike the limited (and far less efficient) anti-NO.sub.x systems now available, he says, this one can work in the presence or absence of oxygen. It also does not appear to be affected by the presence of sulfur contaminants in the fuel that is burned, whereas anti-NO.sub.x systems employing catalysts frequently are.

Still, there are several important engineeringquestions to be answered, Perry says, such as whether the process will operate fast enough to fully eliminate the NO.sub.x produced in a large exhaust stream, whether devices that employ it can be made small enough to fit on a car and whether systems incorporating these devices can be produced inexpensively enough to encourage widespread use.

Perry expects to resolve many of thesequestions within a year. He says a commercial prototype device -- probably initially designed for diesel engines -- might be available within five years.

Ordinarily, the Department of Energy(DOE) would own patent rights to any technology invented at one of its labs. But hoping to speed the commercial development of this process, DOE officials have formally announced an unusual decision in which Perry will be allowed to keep the rights to his invention. As soon as he can obtain the money to start his own firm, Perry says, he will leave Sandia to develop devices that employ this process, which he calls RAPRENO.sub.x., for Rapid Reduction of NO.sub.x..

Harry H. Hovey Jr., director of NewYork State's division of air resources, characterizes the process as "exciting." "If such a device is workable and economically feasible -- two big ifs -- it would help in the acid deposition problem in the East," he says, "because NO.sub.x is inherent to that process." Probably just as important, he says, is NO.sub.x.s' role in smog formation and the ozone problem plaguing all major U.S. metropolitan areas (SN: 6/28/86,p.405). "Without the NO.sub.x.," Hovey told SCIENCE NEWS, "there's a very good likelihood we could meet the ozone standrd."

Linas P. Gobis, an environmental engineerwith the Motor Vehicle Manufacturers Association in Detroit, says that because "NO.sub.x is one of the hardest emissions to lower," this process could also prove very important to the diesel industry.