Refrigeration – Vortex tube – e.g. – ranque
Patent
1994-11-21
1996-01-16
Capossela, Ronald C.
Refrigeration
Vortex tube, e.g., ranque
62 11, F25B 902
Patent
active
054838010
DESCRIPTION:
BRIEF SUMMARY
FILED OF THE INVENTION
The present invention relates to a process for extracting vapor components from a multi-component gas stream using a vortex tube.
BACKGROUND OF THE INVENTION
Although vortex tubes are well known in the art, such devices have not gained wide acceptance due to a limited understanding of the thermodynamic principles involved. As a result few practitioners have studied the features of gas behavior in a vortex tube or adapted use of the vortex tube into gas separation technology.
First observed in the 1930's, the vortex tube is responsible for the so-called Ranque effect wherein a gas at higher pressure which is throttled in a centrifugal field set up in a tube will separate into two outlet streams: one which is cooler and one which is hotter than the temperature of the gas feed. In a vortex tube, the gas stream is fed tangentially to the tube wall and expanded in the tube. The vortex thus formed creates an intense centrifugal field within which gas dynamic transport processes and to a lesser extent Joule-Thomson (JT) cooling establish temperature, pressure and compositional gradients in the tube both axially and radially. The net result is that the vortex core which becomes cooled flows in the opposite direction to the vortex periphery which becomes heated. The coolest gas occurs at the end of the tube in the cool flow direction and the hottest gas occurs at the end of the tube in the hot flow direction. Vapor components of the feed gas, if close to their dew point, initially condense in the core and are flung to the periphery by centrifugal action. However, condensate thus formed becomes heated and re-vaporized. The fraction of the peripheral stream which does not exit the hot end migrates back to the core and gets re-condensed as it flows in the cool direction. This condensate is then generally flung back to the peripheral stream before it can exit the cold end. As a result, condensate vapors entering the vortex tube with the feed are concentrated in and mostly discharged with the hot stream, and the cold stream exhausts as an essentially dry, saturated stream.
Fulton U.S. Pat. Nos. 3,173,273 and 3,208,229, the disclosures of which are hereby incorporated herein by reference, describes basic designs for most efficient vortex tube operation. The characteristic performance curve for a typical vortex tube as described by Fulton having the hot side insulated and operating under ideal gas conditions, where the Joule-Thomson cooling effect is negligible, is shown in FIG. 1, which is a graph of the hot side and cold side outlet stream temperature change (.DELTA.T.sub.h -.DELTA.T.sub.c) with respect to the feed temperature (T.sub.f) versus the fraction of the feed stream (.chi..sub.c) which exits the tube through the cold end. Typically, the maximum temperature drop in the cold stream is about 50 percent of an adiabatic temperature drop occurring for the same pressure drop at the cold outlet. This generally occurs at a cold fraction of 0.4 or less. In terms of temperature differential alone between the hot and cold streams (.DELTA.T.sub.h -.DELTA.T.sub.c), however, this differential is about 83 percent of the adiabatic temperature drop. As a greater fraction is withdrawn from the cold end up to about 75 percent optimally, the temperature drop in the cold stream alone becomes lower (about 30% at .chi..sub.c =0.75) but the temperature spread (.DELTA.T.sub.h -.DELTA.T.sub.c) increases to about 120 percent of the adiabatic temperature drop for the corresponding pressure drop at the cold outlet. Under real gas conditions, for example at high pressures or low temperatures, the overall cooling experienced in a vortex tube is even larger because the Joule-Thomson cooling effect is superimposed over the Ranque effect.
Advantageous features of a vortex tube are an absence of moving parts and reduced utility requirements in comparison with an expansion turbine, for example.
The cooling effect of a vortex tube has been used in the past to recover liquids from gas streams. Fekete U.S. Pat. No. 3,775,98
REFERENCES:
patent: 3775988 (1973-12-01), Fekete
patent: 4093427 (1978-06-01), Schlenker
patent: 4247794 (1981-03-01), Shirokow et al.
patent: 4531371 (1985-07-01), Voronin et al.
patent: 4584838 (1986-04-01), Ajujudom, III
patent: 5246575 (1993-09-01), Alexander
patent: 5305610 (1994-04-01), Bennett et al.
Capossela Ronald C.
Ezarc Pty., Ltd.
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