The Boc Group, Inc.

David J Kamrath

John Douglas Oakey

Robert A Mostello

Graeme John Dunn

Robert Owen

Wei S Hwang

Vladimir Mishkovsky

In order to provide `ultra high purity` nitrogen having diminished concentrations of light and heavy impurities in comparison with nitrogen produced by conventional cryogenic air separation, the nitrogen product from a conventional cryogenic air separation column is introduced into the bottom of a liquid-vapor contract column 2 fitted with a condenser 8 to provide reflux. A liquid nitrogen stream having a reduced concentration of heavy impurities is withdrawn from the column 2 through an outlet 22 situated at a level a few trays below the top tray in the column 2. The liquid nitrogen is then subjected to two stages of flash separation. In the first stage the liquid is passed through valve 24 into a phase separator 26. In the second stage, the resulting liquid from the first stage, having a reduced concentration of light impurities, is passed through valve 32 into a phase separator 34. Liquid nitrogen product is withdrawn from the phase separator 34 through outlet 38.

Air separation

An improved nitrogen generator having a distillation column for separating oxygen and nitrogen, the column having a top and a bottom and a rising vapor stream and a descending liquid stream in countercurrent contact with each other, the improvement comprising means for introducing an amount of liquid nitrogen into the column at an intermediate point in the column wherein the liquid stream composition at said point is substantially equivalent to the liquid nitrogen composition and a means for withdrawing a substantially equivalent amount of purified liquid nitrogen from the top of the column.

Process to ultrapurify liquid nitrogen imported as back-up for nitrogen

There is disclosed an improved process for recovering argon from a tail gas stream, preferably a tail gas obtained from a hydrogen recovery unit processing a purge gas obtained in the synthesis of ammonia and comprised of argon, methane, nitrogen, and residual quantities of hydrogen, wherein the tail gas is partially liquefied prior to introduction into a first fractionation column to form a bottoms liquid stream comprised of argon and methane wherein such liquid stream is thereupon introduced into a second fractionation column to separate argon as an overhead gaseous stream which is condensed to form liquid argon or as product.

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Asbury, NJ, United States of America

David J Kamrath