Argon purification

摘要

Crude argon containing small amounts, e.g. 3-10 per cent, of oxygen and nitrogen is purified by adding hydrogen in stoichiometric excess over the oxygen, catalytically reacting the hydrogen and oxygen, removing water formed to obtain a gas mixture containing oxygen-free argon, residual hydrogen and nitrogen, and subjecting this gas mixture to a single stage rectification process wherein high purity liquid argon and a gaseous effluent containing the hydrogen and nitrogen are obtained. Crude argon from feed compressor 9, and hydrogen added from source 23, in 0.5 per cent stoichiometric excess controlled by H2 analyser 56 in the exit line from the catalytic reactor, are passed to compressor 17 to mix the H2 with the crude argon, and compress the gases to 55 p.s.i.g., which is sufficient to force the gases through the O2-removal steps and to give the necessary 35 p.s.i.g. for the rectification. The compressed gases pass through water cooler 19, water separator 20, reactor 22 containing 0.5 per cent palladium or alumina catalyst, and water cooler 33, to separator 37, where a portion of the gases are removed and recycled through 54 to dilute the crude argon feed to maintain the O2-content therein at below 3 per cent, preferably about 1 per cent. The amount recycled may be fixed for a fixed 02-content crude argon source, or for a maximum O2-content, or may be adjusted in accordance with an O2 analysis in gas analyser 55. Water contained in the recycle is mainly removed in cooler 19. The remainder of the gases from separator 37 pass through dehydrator 43, having refrigeration system 45, alumina driers 53, and heat-exchanger 63, cooled to -280 DEG F. by vaporizing the final liquid argon product, to rectification column 76, having bubble cap-trays 77. Argon separates as a liquid at the bottom of column 76 and H2 and N2 with some argon pass out through condenser 81 at 89. The argon is vaporized by boiler 79, is withdrawn at 111 through liquefier 93, is pumped by liquid pump 117 at 2,500 p.s.i.g., throug heat-exchanger 63, and the resulting argon gas, without any real need for further compression, is passed to cylinders 125. The rectifier column is supplied, from refrigeration system 83, with O2-enriched liquid air through 97 and expansion valve 99 to condenser 81 and with saturated air through 85 to boiler 79, whence it passes through expansion valve 89, liquefier 93, concurrent with argon, to condenser 81. Specification 632,182 is referred to.