Dryer/separator resolves sticky situation at refractory manufacturer

A manufacturer of refractories for the iron, steel and glass industries, needed to dry a difficult-to-handle, non-flowing, sticky mixture of ceramic particles, and process it into a compressible powder for a new ceramic refractory product. The company found that the best way to do the job was to de-agglomerate the material using a centrifugal separator, and dry it using a self-contained circular vibratory fluid bed dryer.

How an integrated fluid bed dryer and de-agglomerating device transformed a sticky mixture into fine, free-flowing, dust-free granules

The process was scaled up easily and inexpensively from a 24-inch diameter laboratory prototype fluid bed drying/de-agglomerating system from Kason to a 48-inch diameter full-scale, circular vibratory production unit.

Scale-up went smoothly since Kason provides a pre-engineered standard selection of screen sizes and fluid bed diameters ready for installation and startup. "You can go from small capacity to higher capacity at relatively low cost," says the plant manager.

The non-flowing, sticky mixture exits a mixer at 7 percent moisture, and enters a Kason Centri-Sifter^® centrifugal screener that de-agglomerates the material into 10-mesh particle sizes before it is reduced to 2 percent moisture in the fluid bed processor at a temperature below 100°C. The dried granules are then fed into a press, which compresses them into various shaped pieces.

Better than Alternatives
The plant manager says the combination centrifugal separator and circular fluid bed processor de-agglomerates and dries this material more efficiently than other methods considered. He says the several ceramic techniques available would require a costly custom-made prototype fluid bed dryer that would become even costlier to scale up to production level.

Rectangular fluid bed processors often selected for this duty did not offer the advantages of the circular vibrating fluid bed. The circular unit is inherently stronger, yet lighter, of simpler design, and less costly to build than a rectangular unit of equivalent surface area. The plant manager says it's a relatively small unit for the amount of throughput. A rectangular fluid bed would also occupy more valuable floor space. The circular unit's self-centered configuration results in fast, easy setup.

Easy to Operate
According to the plant manager, the laboratory fluid bed system prototype proved simple to operate, clean and maintain. The circular design has no corners or crevices for material to lodge in and hamper cleaning. He praises the unit's process control and temperature control via thermocouples. "It's easy to change temperature input and receive accurate, reliable temperature output," he says.

Productivity and performance results for the 1000 lbs/h (455 kg/h) production at the plant are too early to be tallied. But the plant manager is confident the processor will prove the most productive, economical, effective selection to deliver the performance the company needs.

This article first appeared in Ceramics Industry, October 2000.