Drying of water-wet solid materials

Abstract

Process of drying water-wet solid materials, which process comprises, in a system, A. forcibly contacting the water-wet solid material with circulating vapor of a fluorocarbon having a fluorine to carbon atom ratio of at least 1.0 and a boiling temperature of less than about 80.degree. C at atmospheric pressure, said fluorocarbon vapor being at a temperture above about 100.degree. C and said contacting being carried out in the absence of a substantial amount of a noncondensable gas, such as air or nitrogen, B. passing the resulting mixture of fluorocarbon vapor and water vapor from step (a) through a zone maintained at a temperature less than 100.degree. and at least 1.degree. C above the atmospheric pressure boiling temperature of the fluorocarbon to condense a substantial portion of the water vapor but not a substantial portion of the fluorocarbon vapor and, preferably, so that the partial pressure of the water in the remaining vapor mixture is less than about 25 cm of mercury, C. heating the vapor mixture from step (b) to a temperature above about 100.degree. C and recycling the mixture to step (a), D. repeating steps (a), (b) and (c), while maintaining substantially constant in the system the amount of fluorocarbon vapor, until the solid material is substantially free of water and contains only fluorocarbon vapor on its surfaces and/or occluded in its interstices, and thereafter E. removing and recovering from the solid material the fluorocarbon vapor values and F. recovering solid material which is substantially free of water and fluorocarbon.