Catalyst – solid sorbent – or support therefor: product or process – Regenerating or rehabilitating catalyst or sorbent – By heat
Patent
1993-02-01
1995-07-25
McFarlane, Anthony
Catalyst, solid sorbent, or support therefor: product or process
Regenerating or rehabilitating catalyst or sorbent
By heat
502 20, 502 34, 203 58, 203 67, 570262, B01J 2034, B01J 3804
Patent
active
054362113
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a process for the recovery of polluting substances adsorbed in an adsorber such as, for example, solvents.
BACKGROUND OF THE INVENTION
DE PS 30 48 649 describes a process for the recovery of halogenated hydrocarbons adsorbed in activated carbon. In this process, hot air flows through the activated carbon, whereby the adsorbed hydrocarbons are desorbed and pass over into the air flowing through. The air flowing off is then cool ed, which results in a condensation of the hydrocarbons dissolved therein. By again heating and returning the air to the activated carbon, this procedure can be repeated several times. However, strict attention must always be paid to the fact that the temperature of the air remain below the decomposition temperature of the halogenated hydrocarbons. The upper limit for the temperature of the hot air flowing through is, for example, 120.degree. C. with trichloroethylene and 150.degree. C. with perchloroethylene. These values apply to normal atmospheric surroundings. Atmospheric pressure of about 1000 mbar can thereby be considered to be normal atmospheric pressure.
The disadvantage of this process is that, in spite of repeating the procedure several times, there is no complete desorption of the hydrocarbons from the activated carbon filter. In addition, the air has a residue of hydrocarbons after the process has been completed.
Other embodiments of this process are published in the Patent Abstracts of Japan, Unexamined Applications, Section C, Volume 2, No. 59, 27. April 1978, page 458 C 78, No. 53-18504 and in EP 0 381 942. In these publications, the desorption of the adsorbed hydrocarbons is promoted by applying a negative pressure to the adsorber chamber. In EP 0 381 942, the adsorber is first heated to a temperature which is below the decomposition temperature of the adsorbed substance, the adsorber chamber is then sealed off from the surroundings and a high negative pressure is applied. Finally, the desorbed substance is drawn off from the adsorber chamber and the temperature and pressure ratios set in such a way that it condenses.
This process, which is promoted by negative pressure, is in fact superior to the first process mentioned. However, it also does not enable a complete desorption since the maximum working temperature is again limited by the decomposition temperature of the adsorbed substance. Using higher temperatures, at which a substantially improved desorption would take place, is thus not possible.
SUMMARY OF THE INVENTION
Thus, it is the object of the invention to develop the process in such a way that an almost complete desorption of the adsorbed substance is made possible.
In accordance with an embodiment of the invention, a process for the recovery of solvents adsorbed in an adsorber, is comprised of procedural steps of heating the adsorber to a temperature which is below the decomposition temperature of the solvent, sealing the adsorber chamber off from the surroundings, applying a high negative pressure to the adsorber chamber, drawing the desorbed solvent off from the adsorber chamber, and condensing the desorbed solvent by cooling at a suitable pressure characterized therein that the temperature of the adsorber is increased to above the decomposition temperature of the solvent (at normal atmospheric pressure) during at least a portion of the time when the high negative pressure is applied to the adsorber chamber.
In accordance with an embodiment, more particularly, a process for the recovery of solvents adsorbed in an adsorber is comprised of the steps of heating the adsorber in an adsorber chamber to a temperature which is below the decomposition temperature of the solvent, coating the adsorber chamber off from the surroundings, applying a high negative pressure below the value of 10 m bar to the adsorber chamber, drawing the desorbed solvent off from the adsorber chamber, condensing the desorbed solvent by cooling at a suitable pressure, and increasing the temperature of the adsorber to above the decompos
REFERENCES:
patent: 3396473 (1968-08-01), Turner
patent: 4621437 (1986-11-01), Grande et al.
patent: 5187131 (1993-02-01), Tigglebeck et al.
McFarlane Anthony
Pero KG
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