Patent GB-190019254-A (GB)
Title: Improvements in the Method of and Apparatus for the Separation of Gases from their Mixtures.
Inventor: PICTET RAOUL PIERRE
Filed: 1900-10-27
Granted: 1901-10-26
Abstract: 19,254. Pictet. R. P. Oct. 27. Nitrogen; oxygen.-Relates to a method of and apparatus for separating gases from their mixtures, especially applicable for obtaining oxygen and nitrogen from air. Taking air as the example, it is first filtered, then compressed, dehydrated, again filtered, liquefied, filtered free from solid carbonic acid, and finally fractionally distilled, whereby first pure nitrogen is obtained, afterwards a mixture is obtained resembling air, which may be allowed to escape or be returned to the process, and finally pure nitrogen is obtained. The air is passed into a chamber a through an inlet passage e. The chamber has two perforated wood or like partitions c between which cotton wool or other filtering-material d is packed uniformly. The purified air escapes through an outlet f, and is then compressed in any suitable apparatus. The compressed air is then led to a dehydrator or dehydrators of the kind shown in Fig. 2, in which the cylinder g has a cover h, a bottom i, an outlet k, and an inlet j. It is provided internally with a casing m having perforated partitions n. Around the casing is a coil o through which a cooling-liquid is passed, while above it are baffle-plates r. The cylinder is charged with liquid up to above the top of the casing m. If a single dehydrator be employed, a liquid is used in the vessel which can be cooled to 20‹ to 40‹ C., such as glycerine, calcium chloride solution, petroleum, or alcohol, and preferably one with which water readily combines. If two dehydrators be employed, the temperature of the air in the first is reduced to about 0 C., and in the second to about 20‹-40‹ C. The cooling- liquid passing through the coil in the coldest dehydrator may be cooled sulphurous acid, carbonic acid or ammonia, or a cooled saline solution. The dry, pure, compressed air is then liquefied in a heat-exchanger by means of the evaporation of liquid air. The air passes by a tube z and branch tubes x, controlled by cocks y, to spiral groups of pipes w, arranged in a vertical series of vessels u, discharging by tubes 2 into coils 3 arranged in a vertical series of trays v. Each group of pipes w is arranged in a channel 4 of corresponding form placed between walls formed of wood or the like. Liquefied air enters the column at the top 19, and overflows from one tray to the next below and so on to the bottom, by means of the overflow pipes 27 discharging into cups 28. In each section the liquid air surrounds the coils 3 and w, becoming gradually evaporated, while the incoming compressed air becomes gradually colder. Finally, the incoming air is liquefied, while the liquefied air passing down liberates first pure nitrogen from the upper sections, then a mixture of oxygen and nitrogen more or less resembling air, and, lastly, pure oxygen from the lowest sections. The gases are led away as required by a tube 9 having valves 10. An outlet pipe connected to the main gas pipe 9 has a triangular orifice and a square piston which can be raised or lowered so as to uncover more or less of the orifice. A weight is applied to the piston so as to regulate the pressure at which it works. The interior of the apparatus is rendered visible by windows which are arranged with a small escape of cold dry gas from the interior of the liquefier to prevent frost from forming thereon, and by means of internal illumination, such as by incandescent electric lamps and reflectors, or by means enabling the apparatus to be seen through from side to side. A float 35 is connected by an arm 38 to electric contact-plates 40, 41 to indicate the level of liquid oxygen in the lowest tray. The liquefied air passes from the coil 3 to a tube 24 having valves 23 regulated by external handles 51, and leading to one or more filters 20, into which the liquid enters at the centre and from which it flows away at the side. Each filter is formed of a cylindrical casing 42 with two cylindrical perforated partitions 43, 44 between which is a layer of cotton wool or filter paper 45. The end 47 is secured by a screw 49 and a bow 50. Solid carbonic acid is collected within the filter.