Gas separation – Means within gas stream for conducting concentrate to collector
Patent
1986-12-22
1988-04-19
Spitzer, Robert
Gas separation
Means within gas stream for conducting concentrate to collector
55 74, 55179, 55208, 55387, 62 12, 62 18, B01D 5304
Patent
active
047386940
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for purifying a gas by adsorption on activated carbon. It is more particularly applicable in the purification of air or nitrogen containing a solvent and coming for example from a grease removing machine.
Purification by adsorption on activated carbon is in wide use and the activated carbon is usually regenerated by steam. However, this technique has major drawbacks in respect of the desorption of solvents which are mixable with water since a rectification is thereafter necessary for recovering the solvent and for the desorption of chlorinated solvents, since the steam reacts on the solvents and produces hydrochloric acid which renders them unusable. Further, irrespective of the solvent, the regeneration by steam is very costly in consumption of energy.
It is moreover known to purify gases by passing them through a refrigerating trap which separates the impurity, in particular the solvent, by condensation. However, when the content of the impurity in the gas is low this results in high investment and operating costs, since the whole of the stream of gas to be treated must be circulated and cooled.
An object of the invention is to permit the recovery of the impurity under industrial economically acceptable conditions.
The invention therefore provides a process for purifying a gas by adsorption on activated carbon, characterized in that it comprises desorbing the activated carbon by passing a current of inert gas through the activated carbon and then in a refrigerating trap maintained at a temperature of condensation of the impurity of the gas treated and cooled by the vaporization of said inert gas stored in the liquid form, at least a part of the inert gas thus vaporized being used for effecting the desorption of the activated carbon.
According to an advantageous manner of carrying out the process, the desorption comprises a preheating stage in which a charge of inert gas is circulated in a closed loop through the activated carbon until its content of impurity reaches a predetermined threshold, and an eluting stage in which the inert gas is circulated through the activated carbon and sent to the refrigerating trap.
The invention also provides a plant for carrying out such a process. This plant, of the type comprising an adsorber vessel filled with activated carbon, is characterized in that it comprises means for vaporizing a liquified inert gas, means for feeding the adsorber vessel with at least a part of the inert gas which is thus vaporized, and means for cooling the gas issuing from said vessel by heat exchange with the inert gas in the course of vaporization.
The invention further comprises an adsorber vessel employing activated carbon which is particularly suitable for such a plant. This adsorber vessel is characterized in that it comprises heat exchange tubes disposed longitudinally in the vessel and provided with longitudinal fins, said tubes being connected in series with fluid circulating means disposed in the lateral wall of the adsorber vessel.
One embodiment of the invention will now be described with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic view of a purifying plant according to the invention;
FIG. 2 is a diagrammatic view of a variant of the adsorber vessel of said plant, and
FIG. 3 is a sectional view taken on line III--III of FIG. 2.
The plant represented in FIG. 1 is adapted to effect the purification of a gaseous stream, in practice a stream of air or nitrogen containing a solvent in the gaseous form, for example a chlorinated solvent. This stream comes from a machine (not shown) using this solvent, which is for example a grease-removing machine. The plant mainly comprises an adsorber vessel 1 and a refrigerating trap 2.
The vessel 1 is cylindrical and has a vertical axis and is filled with activated carbon; connected to its two ends are respectively an upper conduit 3 and a lower conduit 4 which are interconnected by a conduit 5 provided with a fan 6 so as to form a closed loop.
The conduit 3 is connected to a
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Duval Philippe
Ghnassia-Daudin Benoit
Godino Claude
L'Air Liquide Societe Anonyme pour L'Etude et L'Exploitation des
Spitzer Robert
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