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Source of Supply of Stripping Gaseous Nitrogen Used in the O2/N2 Substitution Column of Plants Purifying Kr/Xe by Distillation

IP.com Disclosure Number: IPCOM000019387D
Publication Date: 2003-Sep-12
Document File: 2 page(s) / 25K

Publishing Venue

The IP.com Prior Art Database

Abstract

In the purification of Kr/Xe (Krypton / Xenon) solely by distillation it is necessary, on safety grounds, to use nitrogen to strip oxygen from the raw Kr/Xe/hydrocarbon stream. The idea is to obtain this nitrogen by flashing the LP column LIN reflux stream to an intermediate pressure and using the intermediate pressure flash gas as the stripping gas.

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Source of Supply of Stripping Gaseous Nitrogen Used in the O2/N2 Substitution Column of Plants Purifying Kr/Xe by Distillation

In the purification of Kr/Xe (Krypton / Xenon) solely by distillation it is necessary, on safety grounds, to use nitrogen to strip oxygen from the raw Kr/Xe/hydrocarbon stream. The idea is to obtain this nitrogen by flashing the LP column LIN reflux stream to an intermediate pressure and using the intermediate pressure flash gas as the stripping gas.

One source of Kr/Xe is the liquid oxygen purge stream of an ASU (air separation unit). The purge stream is very lean in Kr/Xe and also contains hydrocarbon impurities. The first step in recovering Kr/Xe from this stream is to concentrate it in a reboiled side column, to give a bottoms liquid stream termed raw Kr/Xe. The extent of the concentration is limited by the fact that hydrocarbons in the lean stream also concentrate. Thus the raw Kr/Xe stream will typically contain approximately 5000 ppm hydrocarbons in oxygen (along with several thousand ppm of Kr/Xe). Higher hydrocarbon concentrations are not allowed in order to avoid a flammable mixture. The next step has to be the removal of either the hydrocarbons or the oxygen in order to avoid a safety problem.

Conventional plants would vaporize and warm the raw stream and pass it to a catalytic reactor vessel. There, all the hydrocarbons would react with oxygen to form CO2 & H2O, which would be removed in downstream absorbers. The hydrocarbon-free stream would then be recooled to enable final purification by distillation.

An alternative scheme is to remove the oxygen rather than the hydrocarbons. This would avoid the complex and expensive hot catalytic reaction steps. The oxygen would be removed in an N2/O2 substitution column by stripping the raw s...