CLosed-Cycle Drying of Solids

ABSTRACT

The influence of the recovery system and other system parameters upon drying selectivity was studied in a closed-cycle dryer. A continuously-worked unit consisting of a single stage dryer and a ondenser was simulated. In the dryer, a thin solid wetted with a liquid mixture was dryed in contact with an inert gas flowing either parallelly or as an impinging jet Partial recycle of the exhaust gas was allowed. Two recovery systems were studied, a scrubber condenser and an indirect condenser. Both drying and condensation were described by a mathematical model considering a s-phase-controlled process. The inlet liquid composition in the scrubber condenser has the greatest influence on drying selectivity. Degree of vapour recovery, recycle ratio and other operational parameters ffect selectivity and equipment dimensions in a variable extent. The combined use of these variables constitutes a powerful method to control selectivity. The present models may be useful to aid the optimization of the system with regard to product quality in gas-phase-conirolled processes.

Keywords and Phrases:

• closed-systems
• condensation
• multicomponent drying
• selectivity