Challenge
Thin coated sheets with a large specific surface area, sensitive to mechanical abrasion — drum lifters curl and chip the edges.
Inlet moisture of 30% is too high for a single pass down to 2%, so internal circulation is required.
At 2% the paper is in the over-dried zone: brittle, prone to static, and likely to crack during die cutting.
Paper dust is combustible, and static build-up makes sheets cling to duct walls and disrupt discharge.
Solution
A Flash dryer Φ400 was selected instead of a drum: material travels on the hot air stream with a residence time of only seconds, so mechanical damage stays low.
An agitator at the tower bottom breaks up wet sheets; fines leave with the classifying ring while coarser particles stay inside for further drying, cycling several times before reaching outlet moisture.
Screening is placed after drying so wet material cannot blind the screens.
Anti-static measures and combustible dust extraction deal with clinging and discharge.
Result
500 kg/h dry basis; 30% in and 2% out, both on a wet basis, removing about 204 kg of water per hour.
Screening runs on the same line as drying; accepted in October 2026.
The 2% figure is outlet moisture — after packing the paper re-conditions naturally to 5–7%, or the target can be set at 5–7% to suit the downstream process.
Equipment in this case
Flash Airflow Dryer
Capacity varies with operating conditions and is confirmed by a trial run; parameters fixed by machine size, such as air volume, can be stated precisely.
Related questions
How is dryer capacity stated?
A few points need to be clear about capacity figures:
1. Capacity is not a fixed value. The same machine will produce different figures for a different material, a different initial moisture content or a different target final moisture.
2. Figures must state whether they are on a dry basis or a wet basis. Dry basis means the mass of bone-dry material; wet basis includes the moisture. The two differ substantially and the ambiguity causes problems if it is not stated.
3. Official data comes from a trial run. Until the operating parameters are fixed, any capacity figure is only an order of magnitude.
4. Air volume can be stated precisely. It is fixed by the machine size, does not change with the material and can be given at the selection stage.
Providing the material name, the initial moisture content and the target final moisture is what makes a recommendation usable.
Flash airflow dryer or rotary dryer: which one?
The two have different structures and suit different duties:
Flash airflow dryer
It dewaters through brief contact between high-temperature air and the material. Drying is fast, which suits inorganic salts and chemical powders that need rapid dewatering. Sizes are Φ220, Φ280, Φ325, Φ400, Φ500 and Φ600.
Rotary dryer
The rotating drum tumbles the material for more even heating. It suits sawdust, plastic pellets and flake materials that do not break up while tumbling.
How to decide
Look at the material form and whether it is sticky. Powders and fast-dewatering duties point to flash airflow; granular or flake materials needing even heating point to rotary. The moisture content and target final moisture still have to be considered.
Electric heating or steam heating?
The choice mainly follows the site energy supply:
Steam heating
Suits plants that already have a boiler or steam piping. Running cost is relatively lower and it fits long continuous production.
Electric / electromagnetic heating
Suits sites with no steam supply, requiring no piping, with flexible deployment and fast start-up. The electromagnetic series handles roughly 200–5000 kg/h, provided the electrical capacity matches.
How to decide
Check whether a boiler exists, whether electrical capacity is sufficient, and which running cost is lower over time. With adequate power and no steam, electric heating is the simpler choice.
Can the equipment be customised, and what is the lead time?
Equipment is built to suit the operating conditions. Lead time depends mainly on the machine size and how complex the configuration is, and scheduling is arranged once the requirement is clear.
The parameters to provide in advance are: material name and properties, initial moisture content, target final moisture, daily throughput, and the available space and energy supply (electrical capacity or steam parameters).
The clearer the parameters, the more accurate the selection and quotation, and the easier the schedule. If they are not yet clear, a small trial run is the usual way to establish them.
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