GB903367A - Production of hydrogen enriched with deuterium and of heavy water - Google Patents

Abstract

In the production of heavy water, NH3 is enriched in deuterium by exchange with H2, the NH3 is decomposed, N2 is liquefied and separated from the resulting gas and evaporated, the remaining D-enriched H2 is cooled and rectified, <PICT:0903367/III/1> and heavy water is produced from the enriched H2 by oxidation and rectification. N2+H2 synthesis gas enters, and is withdrawn from exchange column 3 at 1, 2 and H2 flows in a closed cycle 9 through cold and hot exchange columns 7, 8, in countercurrent to liquid ammonia containing catalyst flowing from 5 to pipe 4. Enriched NH3 is withdrawn at 14 from evaporator 13 to cracking plant 15, where NH3 is decomposed at 900 to 1,000 DEG C. in the presence of a nickel and iron oxide catalyst to produce a mixture of N2, H2, and HD. The gas mixture passes through heat-exchangers 17, 18 where N2 is liquefied and allowed to separate, and, after evaporation, by return countercurrent to the entering gas, is passed to NH3 synthesis plant 6. Remaining gas passes through heat-exchanger 19 to rectifying column 20, whence the D-impoverished fraction of H2 is withdrawn at the head and is circulated, from 21, countercurrent to the gas in heat-exchangers 17, 18, 19, and to a portion of the circulating gas, withdrawn through compressor 24, in heat-exchangers 25, 27. The withdrawn compressed portion passes through 25, 27, and expansion turbines 26, 28 to condenser-evaporator 29 of column 20, and condensed liquid is sprayed into the head of the column. Circulating H2 is also withdrawn through 22 to the NH3 synthesis 6, or to the feed to the exchange column 3. The enirched H2 passes through 33 to combustion chamber 34, whence the vapour mixture passes to rectification column 36 for recovery of heavy water at 40. The D-impoverished fraction is electrolysed at 11 and H2 is returned at 10 to the cycle through columns 7, 8. Alternatively, the H2 from the NH3 decomposition may be heated to split H-D bonds and recombine D by the equation <FORM:0903367/III/1> by passage over a nickelchromium catalyst. The D2 is separated by rectification and oxidized.