DNFD - Nutsche filter dryer


Drying, filtration, and washing are production steps that are normally handled by multiple machines. The DNFD Delta Nutsche Filter Dryer surpasses this traditional concept by combining operations and offering a more consolidated and flexible approach to the chemical process.


The DNFD Delta Nutsche Filter Dryer is a batch machine that can perform multiple operations:

  • The DNFD Delta Nutsche Filter Dryer can handle even the most difficult liquid separation. The particular shape of its impeller provides gentle cake squeezing, and the filtering sheet is designed for backpressure.


  • Removing impurities and washing the product are important process steps that, if not performed properly, can lead to product inconformity. The DNFD Delta Nutsche Filter Dryer is equipped with advanced devices able to treat and reslurry the same crystal multiple times.


  • Vacuum drying. Process efficiency is strictly correlated with drying time. The DNFD Delta Nutsche Filter Dryer maximizes contact areas and improves the vacuum level, in order to optimize the drying phase.


  • Automatic discharge of dried product. Once the product has reached the required dryness level, the discharge phase can start. The DNFD Delta Nutsche Filter Dryer offers a wide range of discharging systems, depending on product features and on customer needs.


The intrinsic flexibility and versatility of the DNFD Delta Nutsche Filter Dryer offers several advantages:

  • By having the integration of multiple production steps in one machine, installation and operating costs are lower than other process solutions.
  • The filtration and drying processes can be optimized together, leading to better results in terms of product quality.
  • High-potency products are more easily managed when using a single machine for several operations. Material transfers are reduced.


Because of its ability to combine multiple process steps, the DNFD Nutsche Filter Dryer can be applied in many industries, such as:

  • API production
  • Fine chemicals
  • Plastics
  • Dietary supplements/fragrances
  • Chemical Intermediates
  • Precious metals/Metals recycling
  • Catalysts


The DNDF Delta Nutsche Filter Dryer was developed as a result of Delta’s more than 50 years’ experience. Direct knowledge of the production process has allowed Delta to make constant progress in the component design:

  • The cylindrical body, equipped with a convex top head and a flat bottom head, constitutes the machine core, and is certified as a pressure vessel. Depending on batch size and on the available installation location, Delta offers a totally customized design.
  • The agitator is fundamental for each operation. Located on the top head, it can rotate in both directions and can be lifted or lowered, according to process needs.
    • During filtration, the agitator squeezes the cake.
    • During product washing, the agitator mixes and reslurries the product.
    • During discharge, the agitator pushes the crystals to the discharge nozzle.
  • The DNFD filtering sheet, installed on the flat bottom head, is designed for the hardest solid / liquid separation conditions. Depending on the process, it can be equipped with a multi-layer metal filtering media or a textile filtering sheet.
  • The Delta DNFD plug discharge valve, positioned on the body side at the filtering sheet level. The design features are derived from extensive experience and process knowledge. Manually or automatically driven, it can be adapted to both main packaging and high-containment devices.


Delta has developed standard DNFD machine configurations to adhere to the specific production needs for several applications and industries:

  • cGMP and EHEDG, for API production, but also for fine chemicals and fragrances
  • cGMP sterile for sterile API production
  • pilot plant, for small batches for research and development
  • industrial / heavy duty for plastics and precious metals

In addition, Delta offers a wide production range for the Delta Nutsche Filter Dryer:

  • Filtering surface: from 0.01 to 10 m2
  • Operating volume: from 30 liters to 15 m3
  • Contact material: AISI316L, AISI904L, C-22, C-276, coated with elastomers
  • Filtering sheet: metal grid as well as fabric filter
  • Surface finishing: from pickled and passivated to mirror polished
  • Sealing system: from stuffing box to lift off double mechanical seal
  • Certification: PED, ASME, HP0, Selo, ATEX

As per the Delta Costruzioni Meccaniche philosophy, each machine can be completely customized to the customer’s needs. The following list of DNFD Delta Nutsche Filter Dryer options is only a fraction of the solutions that Delta has developed over the years:

  1. CIP system – for washing between batches, which uses rotating spray balls and sprayers on critical areas of the discharge valve
  2. SIP system – steams inside the machine body and checks cold area temperatures for sterilizing grade control
  3. Sanitary insulation – which is mandatory for applications where cleanliness is important, like in white chambers(clean rooms)
  4. Sampling device – for retrieving a product sample and checking the production status
  5. Dust filter on the top head – for product capture while avoiding vacuum pump contamination
  6. High containment devices – for high-potency products, such as a glove box at the discharge nozzle or at the sampling port
  7. Flat bottom lowering and bayonet closure system – for easy maintenance management
  8. External vacuum system coupled with an integrated heating system – for global production line management.


Developments for the DNFD Delta Nutsche Filter Dryer are ongoing. Using its experience and taking into consideration main process needs, Delta designed solutions to improve known process performance issues:

Tilting system

The goal of this device, which further improves the flexible features of the DNFD, is to have the ability to use one machine for:

  • reaction
  • crystallization
  • washing
  • filtration
  • drying

The Tilting system is based on a mechanism that allows machine body rotation. In the case of partial rotation (15-30°), the system improves machine discharge performance, helping the product move to the discharge nozzle. In the case of total rotation, the machine also becomes (in a tilted position) a reactor, combining reaction, crystallization, filtration, and drying.

Delta Ultra Dry for DNFD

The Delta Ultra Dry is a custom filtering sheet design that allows the blowing of nitrogen from the lower side. The system can have different applications depending on what operation the DNFD Delta Nutsche Filter Dryer is performing:

  • During drying, it improves operation time by increasing transferred heat (especially when nitrogen is heated),generating a fluid bed drying effect (mass transfer), and sparging gases lower the partial pressure of moisture or vapor (stripping effect).
  • In the filtration phase, it can help to unclog the filtering sheet (back pulse cleaning).
  • During discharge, it helps to remove the heel cake for complete discharge from the main vessel.

Delta side withdrawal system (EU patent EP 3 322 498 B1)

The Delta side withdrawal system improves filtration performance, by incorporating the sedimentation behavior of some products (decanting). Some side nozzles allow liquid withdrawal, decreasing filtration time and improving product quality.



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