Patent GB-191007858-A (GB)
Title: Improved Process and Apparatus for Splitting up Atmospheric Air into Oxygen and Nitrogen.
Inventor: ROETTGER GEORG
IPC: F25J3/04
Filed: 1910-03-31
Granted: 1910-11-24
Abstract: 7858. R÷ttger, G. April 7, 1909, [Convention date]. Separating gaseous mixtures by liquefaction. -A process for splitting up atmospheric air into oxygen and nitrogen consists in passing the air through a stratified 'column of liquid gases in which the percentage of oxygen increases in the downward direction and the percentage of nitrogen increases in the upward direction, in both cases until complete purity is reached. A diagrammatic form of apparatus for carrying out the invention is shown, comprising essentially a separating-chamber f, an oxygen vaporizer o, and counter-current interchangers b, k. Funnels e are built into the separating-chamber, and are formed near their lower edges with fine perforations. They give a constrained movement to the upwardly-moving gaseous mixture, and to the downwardly - moving liquid, without the individual liquids of the column being able to mingle. The funnels also introduce the gaseous mixture in a finely divided state into the overlying liquid. The stratified column may be prepared by partly filling the column with pure liquid oxygen and then with pure liquid nitrogen up to the mouth of the pipe g; or it may be obtained by filling the chamber f and oxygenvaporizer o to the extent shown with liquid air, and rectifying this liquid as follows. Valves v, c are closed, and a three-way cock p turned to enable vapours from the separating-chamber to be drawn through pipes b<1>, s, x by a compressor (not shown) which returns the compressed vapours through the pipe i and interchanger k into a coil m in the vaporizer, where it is liquefied by causing the evaporation of the surrounding liquid air. The liquid is transferred from the worm to the top of the column through a valve n and pipe g, and the vapours from the chamber o pass through a pipe q, valve r, -and pipe d to the bottom of the column. This cycle of working is continued until pure liquefied nitrogen is supplied to the top of the column, and pure gaseous oxygen to the bottom, when the stratification is complete. Cooled compressed air to be liquefied is passed into the column through the pipe a, interchanger b, and pipe d. The temperature of the liquids in the column varies from -195‹ C., the boiling-point of nitrogen, at the top, to-190‹ C., the point of condensation of liquid air, at the bottom. The boiling-point of pure oxygen is -182‹ C. Consequently the temperature of the lowermost liquid is 8‹ C. below its boiling point, and that of intermediate layers a gradually decreasing amount, so that, apart from the top layer, the mixtures are non- boiling liquids. The result of this is that, at any part of the column, nitrogen only can be vaporized, and thus a complete rectification is effected. On the admission of 100 parts by weight of air of the usual composition, 23 parts of oxygen vaporize 77+x parts of nitrogen, which pass off through the interchanger b. If it is desired to keep the composition and action of the separating-liquid constant, the x parts of nitrogen are drawn off through the valve d, compressed, and returned to the column via the coil m in the oxygen-vaporizer. The 77 parts of nitrogen are then drawn off for use as desired. 23 parts of oxygen overflow into the vaporizer, and pass off for use as desired through the exchanger k.