Process for continuously transferring heat to a moving band

Process for rapidly and efficiently transferring heat to a moving band of solid material with minimum energy expenditure and freedom from environmental pollution, which process comprises:

• a. passing the band through a substantially enclosed purging-drying region through which the superheated condensable vapor of a water-immiscible liquid having an atmospheric pressure boiling point of greater than 20.degree. C. but less than about 120.degree. C. is substantially concurrently passed to dry the band and/or purge noncondensable gas from the band;
• b. immediately passing the band from (a) through a substantially enclosed heat transfer region containing circulating superheated condensable vapor of a fluorocarbon having a fluorine to carbon atom ratio of at least 1.5, a solubility parameter of not more than 6.5, a molecular weight of at least 300 and a circulation driving force of greater than 5.1 cm. of water, to effect the desired heat transfer, the heat transfer region being substantially free of noncondensable gas and at a pressure no greater than that in the purging-drying region;
• c. immediately passing the band from (b) through a substantially enclosed purging region through which dry steam is substantially concurrently passed to purge fluorocarbon vapor from the band, the purging region being substantially free of noncondensable gas and at a pressure which is no less than that in the heat transfer region;
• d. passing the band, substantially free of fluorocarbon, out of the purging region and recovering the band;
• and
• e. recovering and recycling fluorocarbon from the heat transfer and purging regions.