Importance

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Abstract

Material is cooled by direct contact with CO.sub.2, and the CO.sub.2 vapor is recovered. A coolant reservoir is created in a holding tank wherein CO.sub.2 vapor, CO.sub.2 liquid and solid CO.sub.2 exist in equilibrium in the form of slush plus vapor. Liquid CO.sub.2 is supplied to a cooling chamber to cool the material by direct contact, creating contaminated CO.sub.2 vapor. The contaminated CO.sub.2 vapor is removed and directed to the coolant reservoir to condense the CO.sub.2 vapor and any contaminants which liquefy at temperatures above -69.degree. F. by melting solid CO.sub.2. Clean CO.sub.2 vapor and any noncondensables are withdrawn from the holding tank and the withdrawn CO.sub.2 vapor is reliquefied and returned to the CO.sub.2 storage vesssel. Condensable contaminants are periodically removed from the holding tank by heating to a temperature where they can be blown out the bottom.

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First Claim