Sunny Nwadinma | Kason
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.
Vibratory fluid-bed dryer-coolers are gaining popularity in a large number of applications thanks to their rapid drying times and suitability 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 rectangular fluid-bed dryer-coolers, as well as a number of considerations when choosing between circular or rectangular 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 clumping 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 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 configuration 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 consistently 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 models. 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 — especially 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 fluid-bed dryers have a deeper bed; therefore, they can have greater throughput per square foot of space they occupy on a factory floor.
Fast and easy sanitation in a circular vibratory fluid-bed dryer also reduces costs and downtime. Rectangular dryer-coolers can take several hours to clean, while most circular fluid-bed dryer-coolers can be cleaned in less than an hour. For food and pharmaceutical applications, this kind of fast sanitation can make a huge difference both in terms of costs and in terms of consumer safety and quality assurance.
Another important safety feature for some production lines is the explosion-proof design of the circular fluid-bed dryer-coolers. This isn’t available for every fluid-bed unit, so if you’re working with volatile or dangerous materials of any kind, make sure to check with the dryer manufacturer regarding the level of explosion-proofing for its units.
Finally, circular vibratory fluid-bed dryer-coolers are quiet, courtesy of vibration reduction mechanisms. While the blowers make some noise, it’s typically only up to 85 decibels. If required noise levels are lower, then a blower can be fitted with a noise-reducing silencer.
Rectangular vibratory fluid-bed dryers enable high throughput
In general, rectangular vibratory fluid-bed dryer-coolers are suitable for high throughput applications and where sanitary and quick-clean features aren’t a concern. Most rectangular fluid-bed dryer-cooler units can be configured to any size, and large conveyors can provide very high throughput for fluid beds. If you have a very high-throughput application and have a lot of floor space for a fluid-bed dryer-cooler, then a rectangular model might be a good fit. Depending on the material being dried, its bulk density, temperature limits, particle size distribution, and moisture content, high throughput would normally be considered 25 tons per hour or higher.
This option is only practical for larger-scale industrial applications and if you have shifts that provide ample downtime for sanitization (if required). Cleaning rectangular units also requires a certain degree of expertise as maintenance staff must open and dismantle covers and get into the dryer-cooler to clean it. If your production line has shifts that can accommodate a more extensive sanitization routine, or if there are no major sanitary requirements to take into consideration for your specific application, then a rectangular unit may be appropriate. However, if you can accomplish the same throughput needed with an easier-to-clean circular dryer-cooler, then you should adopt a circular configuration to save on long-term overhead expenses related to routine maintenance.
Rectangular fluid-bed dryer-coolers also require extensive rigging to stabilize the machine because of the high-intensity vibrations. In contrast, most circular vibratory fluid-bed dryer-coolers are equipped with internal vibration cancellation technologies and don’t need to be mounted to walls and floors to remain stable in place.
Furthermore, circular units don’t require as complex an installation process as their rectangular counterparts. Because of the configuration, circular units and the entire fluid-bed system can be self-contained and skid-mounted on common frames with casters, ready to plug in and run (plug-and-go). Fluid-bed systems can include heaters, coolers, moisturizers, blowers, and dust collectors. This offers pilot plants fast setup, compactness, mobility, and flexibility — features that can’t be included with rectangular units that are two to three times larger and heavier at equivalent capacities.
When sourcing a vibratory fluid-bed dryer-cooler, a circular model should be considered for its consistent and efficient drying results, quick-clean sanitary design, small footprint, low initial and operational costs, and minimal downtime. Rectangular options are appropriate in high-volume continuous applications where there’s plenty of floor space and the need for pristine sanitation isn’t highly prioritized. Today’s circular vibratory fluid-bed dryer-coolers are available in small-batch, pilot plant, and lab sizes along with larger models suitable for continuous processing applications, offering a wide range of options suitable for most applications.
For further reading
Sunny Nwadinma is the senior applications engineer at Kason Corp. He handles product lines including circular fluid-bed dryers, coolers and moisturizers, circular vibratory and centrifugal sifters, and static sieve screeners. He studied engineering technology at Essex Community College and studied mechanical engineering and science at the New Jersey Institute of Technology.
Kason • Millburn, NJ
973-467-8140 • www.kason.com
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