For a producer of proprietary granular chemical product, long production times and inconsistent drying times were the problems. A circular fluid-bed dryer/screener system from Kason Corp., Milburn, N.J., provided the solutions.
With a circular fluid bed dryer/screener, converted material from storage containers is fed into the top inlet of the dryer by a bucket elevator. In the fluid-bed chamber, the material vibrates on a circular screen within a rising column of 120oF (49oC) air created by an upstream heater/blower ducted into the bottom of the chamber. The continuous airflow and vibration, which is induced by two vibratory motors and spring suspension, separate and fluidize individual particles, maximizing surface area and drying efficiency. The vibratory action also causes material to travel from the center of the screen to a discharge spout at the screen's periphery in controlled spiral pathways on a first-in-first-out basis, ultimately discharging dried material into the top-center inlet of the circular vibratory screener.
An imbalanced-weight gyratory motor positioned beneath the screener chamber vibrates two screening decks. Oversize particles travel in controlled spiral pathways from the center of the screen to a spout at the screen's periphery, where they are discharged for reprocessing.
On-size and undersized particles pass rapidly through the top screen to a bowl-shaped feed tray that directs them to the center of the second screen. On-size particles travel in controlled spiral pathways to a spout at the screen's periphery, where they are discharged, while undersize material passes through the screen onto an integral metal chute that discharges it through a third spout for reprocessing.
Putting It to WorkFor the producer of proprietary granular chemical product, the circular fluid-bed dryer suited the product. The product is composed of a granular carrier material, filler material and an active ingredient. In the new production process, the granular carrier is screened into a narrow size range using Kason's 48" (1,220 mm) dia., two-deck Vibroscreen circular vibratory screener. After the carrier material is sorted, the filler material and active ingredient are added, and the batch undergoes a proprietary conversion process.
From there, it transfers to a 48" dia. circular fluid bed dryer, which reduces the moisture content of the converted material to less than 1 percent at 120oF. After the batch is dried, it is discharged into the integral 48" two-deck Vibroscreen separator that removes agglomerates and fines. The separator discharges the product into bulk bags at a rate of 2,000 lb/hr (907 kg/hr).
Any increase in the ratio of active ingredient to carrier and filler increases the occurrence of agglomeration, so the company monitors the ratio of agglomerates to on-size material to detect whether any process variation has affected distribution of the active ingredient.
Because the drying-screening portion of the overall process operates offline, it also can be utilized to dry raw materials containing excess moisture or to dry other bulk products manufactured by the company. In anticipation of wide-ranging drying applications, the system was engineered to operate at temperatures higher than that required to dry the proprietary chemical.
Satisfactory ResultsThe company's engineering manager says he considered a rectangular fluidized bed dryer but selected Kason's circular unit. “We were impressed with the circulating unit's small footprint, fluidizing action, speed of drying and modularity. You can move it without difficulty. We also had operating experience and a comfort level with circular vibratory screeners that look and function similar to a circular fluidized bed dryer,” he says.
According to the engineering manager, operators previously moved back and forth between tasks while waiting for product to dry. They were unable to focus adequate attention to either task, raising the chance for error. “Operators now are fully utilized in producing and drying the product, with significantly less error,” he says. He reports that that the drying-screening system paid for itself in less than six months from combined productivity gains and labor savings. PH
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