RESEARCH c h a n g e in t h e volume in t h e reaction:
Fix Nitrogen with Heat Canadians form N O by burning propane in pre heated air and quenching . A T M O S P H E R I C NITBOGEN can
F o r t h e first t i m e , kilocurie quantities of long-lived r a d i o a c t i v e fission products are available for y o u r development work. T h e new Fission P r o d u c t s Pilot P l a n t a t Oak R i d g e N a t i o n a l Labora tory makes it possible to d i s t r i b u t e these isotopes a t greatly-reduced prices: • • • • •
Cerium-144 Cesiurn-137 Promethium-147 Strontium-90 Technetium-99
As t h e n a t i o n ' s principal supplier of isotopes, the L a b o r a t o r y offers more t h a n 300 radioactive a n d stable isotope products. R e q u e s t s a r e invited for i n formation concerning compounds for source fabrication. Oxides, fluorides, chlorides, and p l a t e sources are avail able. W h a t e v e r y o u r needs, w e are ready to help y o u . W r i t e to : Isotopes Division, Oak R i d g e N a t i o n a l Labora tory, P . O . B o x X , O a k Ridge,Tennessee.
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1959
be
fixed
tliermally b y burning propane in p r e h e a t e d air. Yields a s high as 3 . 7 % nitric oxide, hy volume, have heen o b tained in a prepilot plant test a p p a ratus at McGill University's gas dy namics laboratory in Montreal, D r . A. L. T h o m p s o n told a chemical engineer ing conference sponsored by t h e C h e m ical Institute of Canada in H a m i l t o n , Ontario. This type of thermal fixation of nitro gen would b e most efficient a t p r e h e a t t e m p e r a t u r e s of 1500° C , available with c e r a m i c heat exchangers. How ever, t h e test equipment used at McGill had a stainless steel exchanger w h i c h allows preheat levels of only 700° C. Propane b u r n s in the Hot air; flame t e m peratures reach about 2700° C . Nitric oxide forms by direct thermal reaction of nitrogen with oxygen inside a zirconia-brick furnace insulated with m a g nesium oxide bricks a n d mineral wool, report Dr. Thompson a n d coworkers D. L. Mordell and George Yano. Reac tion t i m e is 0.1 second o r less, at fur nace pressures ranging from 50 to 7 5 p.s.i.a. T h e hot combustion gases pass out through a water-jacketed "quick cooler." This chills t h e m rapidly to fix the nitric oxide at close to its equilib rium concentration. Leaving the as sembly at about 1000° C , the hot gases then h e a t incoming air in t h e air p r e heater. From here, t h e y enter the gas cooler, w h e r e their t e m p e r a t u r e drops to ambient. A trap t h e n removes water formed by combustion. T h e quick cooler itself can't h a n d l e normal gas flows above 2 0 5 0 ° C—thin layers of soot (about O.008 in.) de posit on t h e cooler tube and slow d o w n heat transfer. Also, cooling area for the volume of gas flowing through t h e | unit seems to b e inadequate. Conse! quently, quenching r a t e reaches only as high as 150,000° C./sec. H o w e v e r , a water-cooled probe ( 0 . 5 in. o.d.) in serted into the quick cooler gives enough additional effect to permit gas t e m p e r a t u r e s greater than 2750° C. to b e run. Theoretically, pressure should not control yield of NO, since t h e r e is no
N 2 -f 0 2 - > 2 N O D r . T h o m p s o n finds, though, t h a t higher pressures help because dissocia tion of COo a n d H 2 0 decreases in p r o portion to the square root of t h e p r e s sure. This m e a n s , h e says, t h a t fur n a c e t e m p e r a t u r e s can b e increased, for t h e s a m e air-to-fuel ratio, by raising furnace pressure. Available laboratory pressures for air, water, a n d p r o p a n e h a v e limited oper ating pressures t o 90 p.s.i.a. B u t D r . T h o m p s o n feels sure that the furnace would r u n all right a t maximum design pressure of 120 p.s.i.a. This w o u l d give h i g h e r gas temperatures which, h e thinks, should give over 4 % N O .
More Smog Secrets Found The West Coast s m o g problem con tinues to yield g r o u n d slowly. Scien tists h a v e d r a w n t h e noose of u n d e r standing even t i g h t e r around it with t w o m o r e findings: • Nitrogen oxides—one of t h e t w o types of components n e e d e d to give t h e smog reaction (hydrocarbons, p a r t i c u larly C 4 and C-, olefins, are the o t h e r ) — can b e removed from auto exhausts b y reduction over chromite catalysts. Most work along catalytic lines has b e e n di rected t o w a r d oxidation. But F r a n k l i n Institute scientists, in a s t u d y sponsored b y t h e Air Pollution Foundation, find that t h e y can remove up to 909r of t h e nitric oxide u s i n g zinc-copper chromite, iron c h r o m i t e , b a r i u m - p r o m o t e d copper chromite, and chromium-promoted iron oxide as catalysts. T h e same catalysts also oxidize hydrocarbons and C O , t h e institute group finds. More study is n e e d e d , h o w e v e r , t h e institute warns, to d e t e r m i n e w h e t h e r t h e catalysts will b e poisoned by lead in t h e exhausts. • F o r m a l d e h y d e a n d acrolein h a v e been t a p p e d as the most probable eye irritants in W e s t Coast smog. These two a l d e h y d e s have been suspected as t h e culprits, b u t solid proof wras lack ing. Stanford Research Institute, in a report to the Air Pollution F o u n d a t i o n , Los Angeles, shows t h a t these t w o com p o u n d s are formed in photochemical oxidation of olefins, that t h e d e g r e e of eye irritation can b e p r e d i c t e d accu rately from t h e i r concentrations in reac tion p r o d u c t s , and that they are t h e only c o m p o u n d s formed i n t h e photo c h e m i c a l reaction t h a t can produce eye irritation in the concentrations found.Β
