Paddle dryers/ vacuum paddle dryers

Paddle dryers/ vacuum paddle dryers

Our MertoDry vacuum bucket dryers are have proven their worth many times and are universally useful. They serve primarily the drying in batches of moist-crumbly and/or powdery crystalline products. Also, doughy wet products that disintegrate during advanced drying and become granular or powdery in their dry state can also be processed. For products that tend to agglomerate on drying, our bucket dryers can be equipped with high-speed knife mills known as macerators.

Vacuum bucket dryers are also characterised by minimal space requirements for the largest possible thermal transfer surface and by the thermally gentle treatment of the products. Compared to the well-known vacuum drying closets, they have the advantage of generally automated product entry and exit and they induce high drying speeds through the continuous repositioning of the product on the heating surface. The entire drying process takes place within a hermetic seal. The following advantages arise from this:

  • Oxidation of the product is prevented as far as possible.
  • Toxic substances can be processed.
  • Safety is assured with explosive, solvent-based products.
  • Dust-free entry and exit prevents contamination of the dryer surroundings with product deposits.

Usually, steam or thermal oil are used as a heating medium. Hot water or hot/cold brine can also be used. The bucket mechanism loosens the dry product, mixes it radially and axially and thus ensures an even thermal treatment and a homogenous structure of the dried product.
Bucket mechanism / Positioning and sealing

Paddles / Positioning and sealing

Propulsion is usually effected by a converter controlled transmission motor. Versions with a hydraulic drive can also be provided. The central component of our bucket dryer is the cylindrical housing with inbuilt bucket mechanism. The housing is heated and if desired the bucket well and the bucket arm can also be heated.

Sealing of the bucket mechanism to the dryer housing is done in the simplest case using double-acting stuffing box packing. With more complex requirements, in particular where there is risk of explosion and/or with toxic or pharmaceutical products, double-acting mechanical gas or liquid seals are used.

Exhaust air purification/Filter
For the separation of arising dusts, the dryers are usually equipped with self-cleaning exhaust vapour filters so that no product gets into the subsequent units, e.g. condensate traps or vacuum pumps. Via pulse-jet cleaning, the filter tubes and/or filter plugs are cleaned on a cycle using nitrogen or air pulses and the adhered dust falls back into the dryer tank.

Depending on requirements, materials in contact with the product are simple boiler plate, wear-resistant steels, stainless steels of various qualities or nickel-based alloys such as Hastelloy. The dimensions of our Merto-Dry bucket dryer range from laboratory size of 50 litres to plant with capacities of 30 m³.

We offer plant for the widest variety of requirements.


  • ATEX
  • FDA
  • GMP

The peripherals of the bucket dryer, such as vacuum pump stands, condensers, plant controls or heating/cooling units are also supplied on request.

Technical Centre
Laboratory trials are usually essential for the procedural design of dryers and filters. Our Technical Centre is equipped with a wide variety of technology for this purpose. Our equipment is also portable to enable our customers to carry out substance-based investigations in their factory.