Imperial and Band Dryers

A imperial and band dryers is a system that removes moisture using controlled heat and airflow for uniform drying results.

It operates through a process of heat transfer and air circulation to evaporate moisture from materials efficiently.

It provides high efficiency, uniform drying, and low energy consumption.

Industries such as food, chemical, pharmaceutical, and textile rely heavily on these dryers.

Yes, Kerone designs systems tailored to specific process and material needs.

The design ensures quick cleaning and minimal servicing requirements.

Kerone’s systems are optimized for reduced power consumption and higher heat utilization.

Yes, belt speed, airflow, and temperature can be tailored to product needs.

A multi-pass band dryer routes the product conveyor belt through multiple horizontal passes, stacked vertically within a single dryer housing before the product exits. This means the effective drying length is multiplied by the number of passes without extending the dryer footprint. A three-pass configuration provides three times the residence time of a single-pass unit of the same physical length. This is particularly valuable in retrofitting drying capacity into existing production buildings where floor space is limited. The product transfers between passes by gravity or guided chutes, which also provides gentle mixing that can improve drying uniformity on the lower passes.

Band dryer belts are specified based on the product characteristics, operating temperature, and hygiene requirements. Woven wire mesh belts in stainless steel are standard for food-grade and high-temperature applications, the open mesh structure allows airflow through the product bed, maximising drying efficiency. Plastic modular belts offer food-grade compliance at lower temperatures and are easier to clean. Rubber-coated or solid belts are used when fine particles cannot fall through the mesh. Belt pitch, wire diameter, and mesh aperture are selected to balance product support (preventing small particles from falling through) with adequate open area for airflow. The belt is a significant wear item and should be specified with the product contact and cleaning requirements clearly defined.

Band dryers excel in food and agricultural applications where the product is a discrete piece or granule that would be damaged by tumbling or agitation. Sliced vegetables, fruit pieces, pasta, biscuits, pet food kibble, extruded snacks, fish, meat strips, and herb leaves are processed on band dryers where the product travels through the drying zones undisturbed. The dryer's ability to control residence time precisely by adjusting belt speed, combined with independent temperature and airflow control in each zone, makes it possible to match the drying curve of almost any product. This combination of gentle handling and process flexibility is difficult to replicate in rotary or fluidised bed dryers for piece-form products.

The drying process has two distinct phases: a constant-rate period where surface moisture evaporates rapidly and temperature can be applied more aggressively, followed by a falling-rate period where bound internal moisture migrates slowly to the surface and overheating causes case-hardening or colour damage. Multi-zone band dryers are configured so that the first one or two zones operate at higher temperatures to drive off free moisture quickly, while the later zones reduce temperature and increase recirculation to gently draw out residual moisture without damaging the product structure. For thermally sensitive products like dried herbs or spices, a final cool-down zone before the product exits also prevents condensation during downstream packaging.

Even product distribution across the full width of the conveyor belt is critical for uniform drying. Irregular feed distribution leaves some areas of the belt thinly covered and others over-loaded, creating dry and wet zones within the same batch. Kerone addresses this with engineered product distributors at the feed inlet - vibratory spreaders, oscillating chutes, or levelling rolls that spread the product uniformly across the belt width. Photo-electric sensors can detect distribution anomalies and adjust the spreader in real time. For sticky or cohesive products prone to bridging, the feed hopper is fitted with agitators or vibrators to maintain consistent flow onto the belt without interruption.

A band dryer uses a continuously moving permeable conveyor belt that allows drying air to pass through the product layer, from above and below. A tunnel dryer typically moves product through the tunnel on trays, trolleys, or hangers without forced through-flow of air through the product bed itself. Band dryers achieve much better drying uniformity for granular or particulate products because the air contacts all surfaces more uniformly. Tunnel dryers are preferred for large, solid, or surface-coated articles - pottery, painted panels, printed boards where the product form does not allow through-airflow. If your product can be spread onto a permeable belt, a band dryer will generally out-perform a tunnel dryer on drying efficiency and batch-to-batch consistency.

Food-grade band dryers must be designed for cleanability from the outset, not retrofitted. This means stainless steel construction with sealed welds, rounded internal corners with generous radii, removable belt sections, hinged access panels on all sides, and spray-down nozzle ports for CIP (clean-in-place) or manual wash-down. The conveyor belt must be removable or at minimum accessible along its full length for manual cleaning. Drainage points should be positioned to prevent water pooling. HACCP compliance requires that all lubricants are food-grade (NSF H1 rated), and that no lubricant application points are positioned above the product contact zone. Cleaning validation requires documentation of the CIP or wash-down procedure, water temperature, and detergent concentration.