CIBA-GEIGY, Cranston , RI


The process required a continuous, closed-circuit drying operation to upgrade quality and lower costs for proprietary, heat-sensitive agricultural chemicals. The former drying method used vacuum tray units handling feed rates of 500 Ibs/hr of solvent/ water-wet, heat sensitive crystals. The TURBO-DRYER® that replaced them is 10 ft dia. x 15 ft high, stainless steel, 22 trays. The evaporated solvent/water vapors are exhausted from the top of the main drying chamber together with the inert drying gas to a secondary cyclone collector and to a scrubber-condenser. This dehumidified drying gas is then recirculated to a steam heating coil and then back to the TURBO-DRYER® through a manifold in one side panel. Gas tightness maintains the low oxygen level requirement of 1/2% by volume. Higher oxygen concentrations can result in product deterioration as well as hazardous explosive conditions. Nitrogen gas purge make-up requirements are well under 10 scfm (17 cubic meters/hour). Volatiles in feed are reduced consistently from around 10% to 0.5%. Uniformly dried material is continuously produced utilizing temperatures of 100-200°F. The savings from the continuous TURBO-DRYER® stem from lower fuel and power requirements, as a result of reducing heat loss and eliminating vacuum requirements, as well as reduction of labor due to automatic controls. The compactness of the unit also resulted in a reduction in space.


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