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March 2021 / 41 CIRCULAR VERSUS RECTANGULAR VIBRATORY FLUID- BED DRYER-COOLERS This article discusses the differences between circular and rectangular vibratory fluid-bed dryer-coolers and the situations in which each would be a good fit. Sunny Nwadinma, Kason large continuous throughput applications. Materials processed within a circular vibratory fluid bed move in a spiral motion, providing even airflow and vibration throughout the bed to separate and fluidize individual particles. The spiral motion maximizes the surface area of material and the rate at which it dries, resulting in a highly consistent product. Since a circular vibratory fluid bed has no corners by virtue of its design, it offers the benefit of eliminating material clumping and buildup around the edges or corners of the unit. Furthermore, its circular config- uration allows for precise control of air temperature, airflow, bed depth, dwell time, and material flow paths on a first-in, first-out basis. The circular design also has the benefit of built-in internal back mixing that allows wetter, sloppier feed materials to be dried more consis- tently and with a low heat history. Not only does this render a more homogenous material, but it also keeps the machine clean and easy to maintain in the long run. Another benefit of the circular vibratory fluid-bed processor is its inherent strength, which eliminates the need for heavy-gauge walls and cross braces required to withstand continuous vibration in rectangular mod- els. This feature allows materials of construction to be down-gauged, vibratory motors to be downsized, and associated components to be eliminated. The circular unit also requires only one air inlet and outlet and has fewer weld seams compared to rectangular models, reducing overall size and construction costs — espe- cially when finished to 3-A, USDA, FDA, and BISCC sanitary standards. Cost savings with circular vibratory fluid-bed dryers come through a number of features, including zero- or low-installation costs and multipurpose processing. The average power consumption for circular versus rectangular fluid beds tends to be 40 to 50 percent lower for the circular configuration based on similar material throughput and moisture content. Circular V ibratory fluid-bed dryer-coolers are gaining popularity in a large number of applications thanks to their rapid drying times and suit- ability for heat-sensitive materials. Vibratory fluid-bed dryer-coolers offer batch and continuous processing capabilities, allowing high throughput for drying and heating applications in a one-step process. There are important differences between circular and rectan- gular fluid-bed dryer-coolers, as well as a number of considerations when choosing between circular or rect- angular designs. Circular vibratory fluid-bed drying and cooling systems In surveying the different types of vibratory fluid-bed dryer-coolers, the circular models have the following features: • Consistent heating throughout the fluid bed • Continuous internal back mixing for drying more sluggish or hard-to-fluidize materials • Small footprint per volume processed • Spiral motion with no corners eliminates clump- ing and accelerates material drying • Efficient cleaning and inspection with a sanitary design • Compliance with stringent standards including 3-A, USDA, FDA, and BISCC • Rapid installation and, in some cases, transportability • Low installation and operational costs • Low power consumption • Relatively low noise • Explosion protection Circular vibratory fluid-bed drying and cooling systems are available in a range of sizes, from 18 to 84 inches (450 to 2,125 millimeters) in diameter. For manufacturers, this translates to a great range of flexibility when it comes to both small batches and