The Boc Group, Inc.

Airco, Inc.

Ratan Banerjee

A vapor component of a gas mixture is separated by condensation and is recovered for further use. A solvent vapor mixed with inert gas is condensed in a multistage heat exchange system in a manner which utilizes a first refrigerant to condense a portion of the vapor in a first heat exchange device, a second refrigerant, typically cold inert gas, for condensing a further portion of the vapor in a second heat exchanger and a third heat exchange device wherein the liquid phase of the inert gas (i.e. cryogenic liquid) is supplied to provide a source of refrigeration. In this latter heat exchange device, the cryogenic liquid is introduced into a body of condensed vapor thereby chilling such condensed vapor and stirring the same to avoid freezing. Chilled, condensed vapor is removed from the latter heat exchange device and is returned as a reflux thereto to condense the vapor component of the gaseous mixture supplied thereto. A further portion of the chilled, condensed vapor is recirculated to the body of condensed vapor to assist the stirring of this body to avoid freezing of condensed vapor which is collected from the above heat exchange devices and is passed to a suitable storage facility.

Heat exchange methods and apparatus

A chamber such as a curing oven or drier is inerted during the curing of solvent borne resin coatings with the solvent vapor formed therein being withdrawn together with inert gas at a substantially constant flow rate. The withdrawn gas stream is supplied to a condensation unit to enable recovery of solvent and the noncondensed gas discharged from the condensation unit is returned to the oven at a flow rate which may be varied so as to maintain a material balance with respect to the oven atmosphere. Appropriate adjustments are made in response to changes occurring in the oven solvent vapor and/or oxygen concentration without disturbing the material balance mentioned above while the oven atmosphere is withdrawn at a substantially constant flow rate. A plurality of ovens may be connected to a single condensation unit and upon detecting undesired conditions such as excessive oxygen levels in one oven, the same may be separately isolated from the condensation unit.

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New Brunswick, NJ, United States of America

Ratan Banerjee