Method for drying by vapor recompression

A drying process for drying a damp material in a closed vertical dryer having upper and lower ends and having a plurality of horizontally and vertically spaced heating plates positioned therein comprising the steps of feeding a damp material into the upper end of said closed vertical dryer, causing said damp material to pass continuously over and in contact with one surface of said heating plates in order that said damp material proceeds through said dryer to an exit point at the lower end of said vertical dryer, simultaneously feeding into the said lower end of said vertical dryer a mixture of dry air and water vapor under conditions which will provide saturated feed air at a temperature between 60.degree. C. and 100.degree. C.;

• removing from the upper end of said vertical dryer a mixture of dry air and water vapor at a temperature above the temperature of said saturated feed air;
• cooling said removed mixture to the temperature of said saturated feed air to provide saturated air and water vapor separately, compressing said vapor to raise the temperature thereof to be above the temperature of said saturated air, and refeeding said saturated air to the bottom of said vertical dryer and said heated vapor to said heating plates to heat said plates.