Tray Dryers

A tray dryers is an industrial system that removes moisture from materials using controlled heat and airflow.

It operates by circulating hot air or transferring heat to evaporate moisture from products efficiently.

It ensures faster drying, energy efficiency, and product uniformity.

Industries like food, agriculture, pharmaceutical, and chemical commonly use these dryers.

Yes, Kerone designs every system according to specific industry and process needs.

Yes, precise temperature control ensures safe drying for sensitive materials.

Kerone’s designs optimize heat recovery and minimize energy consumption.

Regular inspection, cleaning, and calibration ensure optimal performance and longer lifespan.

The terms tray dryer and box dryer are sometimes used interchangeably, but in precise industrial usage a tray dryer refers specifically to a walk-in or cabinet dryer where product is loaded on individual removable trays placed on fixed shelves inside the chamber. A box dryer typically uses trolley-mounted tray frames that are wheeled in as a unit. Tray dryers are suited for smaller batch sizes, laboratory-scale operations, and applications where individual tray access is needed during the drying cycle. Box (trolley) dryers are more appropriate for heavy loads, large batch volumes, or operations where minimising door-open time (and heat loss) is important. Both share the same airflow principles but differ in loading mechanism and operational workflow.

Recommended bed depth varies with material particle size, density, and porosity. As a general guideline, free-flowing granular materials like pharmaceutical granules should not exceed 20–30 mm depth per tray. Dense materials like seeds or chemical cake can tolerate up to 50 mm in a well-designed high-velocity tray dryer. Exceeding the recommended depth creates a moisture gradient from the tray surface (dry) to the tray base (wet), resulting in a non-uniform batch. For regulated products, moisture mapping across tray positions and at different tray depths is part of the qualification process. Kerone specifies maximum product depth for each tray dryer configuration based on the specific material and required uniformity standard.

Kerone's industrial tray dryers are available across a wide operating temperature range, from ambient + 10°C up to approximately 300°C for high-temperature industrial applications such as ceramic curing or rubber vulcanisation. Heating sources include electric resistance elements, steam coil heat exchangers, hot water coils, gas-fired direct or indirect heaters, and thermal oil circuits. The choice of heating source is driven by the available utility at the plant, the required temperature, and the regulatory environment. Pharmaceutical applications almost always use steam or electric heating for clean, controllable heat. Chemical and industrial applications more commonly use gas-fired or thermal oil heating where high temperatures are required at lower utility cost.

In pharmaceutical manufacturing, tray dryers are used primarily for drying wet granules after granulation and for pre-drying API intermediates. GMP-compliant tray dryers must be constructed from pharmaceutical-grade stainless steel (SS 316L for product contact surfaces), have no dead legs or trapped sections where product residues can accumulate, be equipped with validated temperature sensors with calibration records, and have full surface finish documentation (Ra values for all contact surfaces). The drying chamber must be pressure-tight to support HVAC-controlled environments. Data acquisition systems must generate 21 CFR Part 11-compliant electronic records of time-temperature profiles for every batch. Kerone supplies tray dryers with full documentation packages (DQ/IQ/OQ) to support pharmaceutical qualification requirements.

Tray dryers operate with a recirculating air system that continuously circulates heated air across product trays. A portion of this air is exhausted and replaced with fresh make-up air to prevent the moisture content of the circulating air from reaching saturation at which point drying would stop. The ratio of exhaust air to recirculated air is controlled by adjustable dampers. Opening the exhaust damper too wide wastes energy by exhausting hot air before it has picked up its maximum moisture load. Closing it too much allows humidity to build up, slowing the drying rate. Automatic humidity control, using a humidity sensor in the recirculation duct connected to the exhaust damper actuator, maintains the optimal balance throughout the drying cycle.

Cycle time in a tray dryer is governed by the initial moisture content, the target outlet moisture, the product thickness and thermal conductivity, the tray bed depth, the air temperature, the airflow velocity, and the relative humidity of the circulating air. The most effective way to reduce cycle time without compromising quality is to increase airflow velocity, which reduces the mass transfer resistance at the product surface. Reducing tray bed depth also helps by shortening the moisture diffusion path. Increasing temperature can reduce cycle time but risks product quality in heat-sensitive materials. Pre-conditioning the product, for example, using centrifugal dewatering to reduce initial moisture load before tray drying significantly reduces the total drying duty and cycle time.

Kerone's tray dryers can be specified with PLC-based control systems ranging from simple single-loop temperature controllers to full SCADA-integrated systems. For Industry 4.0 readiness, the PLC communicates via Ethernet/IP, Modbus TCP, or OPC-UA to plant-level MES or ERP systems. Batch records including time-temperature profiles, alarms, operator interventions, and sensor readings are automatically logged to a centralised data historian. Remote access via secure VPN allows Kerone's service engineers to diagnose issues and update control parameters without on-site visits. Predictive maintenance modules monitor heater element resistance and fan bearing vibration, generating maintenance alerts before failures occur. For pharmaceutical applications, the system can be configured to meet 21 CFR Part 11 electronic records requirements.