GB826962A - Process for recovering deuterium - Google Patents

Abstract

<PICT:0826962/III/1> Technical hydrogen, which has its content of contaminating gases reduced to a proportion such that these contaminants are entirely precipitated in the solid state on cooling to distillation temperature, is cooled in a reversible heat regenerator to deposit the solidified contaminants, and distilled to recover deuterium. The distilled deuterium-poor hydrogen is passed back through the heat regenerator to take up the solidified contaminants, and is contacted with water to effect catalytic exchange of deuterium therewith. The resulting deuteriumenriched hydrogen is separated from the water, cooled in a reversible heat regenerator to deposit solidified contaminants, distilled to recover deuterium, and the deuterium-poor hydrogen is passed back through the heat regenerator to take up the solidified contaminants. Technical hydrogen may be fed into hydrogen passing in a closed cycle catalytic exchange process just before it enters a reversible heat regenerator, when the distillation of the technical hydrogen and of the hydrogen enriched with deuterium from water, and the solidification of contaminants from both, are effected simultaneously in the same distillation column and heat regenerator, respectively, and excess hydrogen is withdrawn from the circuit after the heat regenerator. Alternatively, technical hydrogen may be distilled in a separate distillation column, and passed wholly or in part into a catalyst exchange process either to be withdrawn from the heat regenerator, or retained as make-up in a closed cycle. The gas from a plant 1, which may be an ammonia synthesis gas plant, or a plant producing hydrogen from coal, oxygen and steam, after being freed from water and CO2 is cooled in heat exchanger 13, when the proportion of contaminants above that desired collects as liquid in tank 14. The cooled gas is passed back through heat exchanger 13 and fed at 18 into a closed circuit catalytic exchange system, where it joins circulating hydrogen, which has been saturated with water vapour in washer column 2, passed through catalyst bed 4, and has had water vapour separated in washer column 5 and absorber 6. The mixture of hydrogen is passed through heat exchanger 7, which cools the gas to just above the solidification point of the contaminants, and heat exchanger 8, where contaminants solidify, to distillation column 9, whence a deuterium concentrate is withdrawn at 10. The distilled hydrogen leaving at 11 passed back through exchangers 8, 7 taking up contaminants. The hydrogen is recycled through 3, while excess is withdrawn at 19 and returned to the synthesis plant after reintroduction through pump 22 of the liquid contaminants in tank 14, which are evaporated to recover cold. Exchangers 13 and 7 may be combined, when liquid is removed at 23. In alternative apparatus (Fig. 2, not shown) a separate distillation column is provided and the distilled hydrogen is fed into a catalytic exchange process which may be operated as a closed cycle or a once-through system. Specifications 799,351, 801,691, [both in Group XXVIII], and 815,098 are referred to.