Tunnel Dryer

A tunnel dryer is a high-performance system designed for uniform drying of materials through controlled heat and airflow.

It operates by circulating heated air or energy through the material, ensuring even moisture evaporation and high throughput.

They provide faster drying, energy savings, and consistent product quality.

Industries such as food, chemical, and pharmaceutical widely use these dryers.

Yes, Kerone’s designs are fully customizable based on process requirements.

Yes, these dryers offer precise temperature control to protect sensitive products.

The system is designed to minimize energy waste and optimize heat utilization.

Tunnel dryers range from as short as 5 m for pilot-scale systems to over 150 m for large ceramic or brick production dryers; the required length depends on product moisture reduction, allowable product temperature, and desired throughput.

Counter-current drying means the drying air flows in the opposite direction to the product movement, so the hottest, driest air meets the driest product at the exit and the coolest, most humid air meets the wettest product at the inlet — this is thermally efficient and gentle for heat-sensitive products.

Yes, Kerone designs food-grade tunnel dryers with stainless steel interiors, hygienic belt systems, and clean-in-place capability; sanitary design principles are applied to all product-contact surfaces and air distribution systems.

In counter-flow operation, drying air moves in the opposite direction to product travel, so the hottest, driest air meets the nearly finished product near the exit while the coolest, most humid air meets the wettest product at the inlet — this arrangement is thermally efficient and gentle on heat-sensitive products since they're never exposed to the harshest drying conditions. Parallel-flow runs air and product in the same direction, exposing wet product to the hottest air immediately, which speeds initial moisture removal but risks surface hardening or case-hardening on some products. Combined-flow uses different airflow directions in different zones along the tunnel to balance these effects. The right arrangement depends on the product's specific moisture release behavior and heat tolerance.

The number of zones depends on how the specific product's moisture-release rate changes as drying progresses, since most materials dry faster at the start when surface moisture is abundant and slower later as internal moisture must migrate to the surface. A simple, robust product might need only two or three zones, while delicate food items or pharmaceutical granules with complex drying curves may benefit from five or more zones, each with independently tuned temperature and humidity. More zones allow more precise tailoring of the drying profile to the product's actual behavior, but each additional zone adds capital cost and control complexity, so Kerone balances zone count against the product's actual sensitivity to over- or under-drying at each stage.

Yes, tunnel dryers can be configured with hot air circulation, infrared, microwave, or radio frequency heating, and selecting the right technology depends on the product's drying mechanism and how it absorbs energy. Hot air remains the most common and economical choice for general-purpose drying. Infrared works well for surface drying and rapid moisture removal from thin products. Microwave and radio frequency heating penetrate the product volume rather than relying solely on surface heat transfer, which can dry thicker or denser materials more evenly and faster, though at higher equipment and operating cost. Kerone selects or combines these technologies based on the product's thermal absorption characteristics and drying speed requirements.

Product can move through a tunnel dryer on carts, conveyor belts, or hanging frames, and the right choice depends on the product's shape, fragility, and how it needs to be loaded and unloaded. Conveyor belts suit free-flowing or robust items that can sit directly on a moving surface without damage. Carts allow batch-style loading flexibility within an otherwise continuous tunnel, useful when products need to be prepared on trays before entering. Hanging frames suit products like certain meat or textile items where airflow needs to reach all sides without a supporting surface blocking part of the product. Each carrier system also affects how easily the tunnel interior can be cleaned between production runs.

Tunnel length directly determines the total drying time available at a given conveyor speed, since a longer tunnel gives product more time in the controlled drying environment before reaching the outlet. This means buyers needing high throughput with longer drying times must either accept a longer physical tunnel or compensate with more intensive heating in a shorter length, which carries its own tradeoffs in energy use and product quality. Tunnel lengths can range from compact pilot-scale units of a few meters up to very long industrial systems exceeding 100 meters for high-volume ceramic, brick, or food production. Plant layout constraints often shape this decision as much as the drying requirement itself, so Kerone considers available floor space alongside throughput targets.