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Nauta® Conical Screw Dryer

Hosokawa Micron’s Nauta® Conical Screw Dryer is based on the cutting-edge design of the iconic Nauta® Conical Screw Mixer, one of the most recognised, effective and successful conical mixers in the world. Invented in 1939 by Johannes Ewardus Nauta, the patented mixer was originally designed to process pulverised material, but thanks to a series of technical developments and improvements it can now efficiently process everything from powders and granules to pastes and viscous slurries – including products that may be toxic, heat-sensitive, explosive, brittle or contain solvents.

Our Nauta® Conical Screw Dryer is engineered to work in a very similar way to the mixer – and handles the same kinds of materials – but the addition of a heated jacket, heated agitator and auxiliary components transforms the equipment into an energy-saving batch dryer, offering rapid mixing and drying – and a consistently excellent-quality end product – in one convenient process. The dryer is also useful for a number of other applications, such as sterilisation, crystallisation, alkalisation, cooling of solids and liquids, de-aeration of pastes and liquids, along with wet agglomeration and granulation of solids, making it an extremely economical, versatile and space-saving equipment choice suitable for many processing industries, including the stringently regulated food and pharmaceutical sectors.

Did you know?

The Nauta® conical screw vacuum dryer is a universal batch dryer suitable for drying powders, granules, pastes and viscous slurries, especially when products are heat sensitive, contain solvents and are toxic or explosive.

The Nauta® Conical Screw Dryer by Hosokawa Micron is tailor-made to customer specification and to suit the application/s it is required for, whether that’s drying, sterilisation, crystallisation, de-aeration, cooling or wet agglomeration. Each piece is built to the latest industry standards from materials including grades of stainless-steel, Monel, nickel, titanium, Hastelloy etc.

The Nauta® Conical Screw Dryer can be manufactured in many sizes and below, you’ll find details of a selection of seven of the most popular standard models available, including their typical characteristics.

Hosokawa Micron Group’s in-depth knowledge and first-hand experience encompass the design, manufacture, installation, maintenance and upgrading of vacuum drying equipment and process systems. This includes engineering and manufacturing an array of ancillary equipment, such as heated agitators – an excellent solution when handling sticky materials; a unique multi-purpose ISEM™ ball segment valve that is gas, dust and liquid tight, has no flow resistance when opened and is easy to clean and access, which is perfect for reliably handling toxic and solvent materials under challenging circumstances; specially designed Nauta® vacuum filters and tailor-made PLC or DCS control systems featuring the latest smart technology. We also supply high-performance heating/cooling skids, along with a range of condenser/vacuum skids.

Optional Features

  • Nauta® vacuum filter
  • Sampler
  • Heating/cooling skid
  • ISEM™ ball segment valve
  • Lump breaker
  • Air treatment system
  • Liquid injection system
  • Control and process automation system
  • CIP/SIP skid
  • End product recovery (ATEX standard)
  • Product feeding system


Laboratory-scale and Pilot-scale Vacuum Dryers

In addition to full-scale production models of the Nauta® Conical Screw Dryer, we can also supply smaller versions of the technology for use in laboratories. Like their full-scale counterparts, they have multi-purpose functionality and may be used by a wide variety of manufacturing sectors.

The complete drying systems are compact and integrate the main vacuum dryer, plus any additional equipment needed to perform the intended process. These systems are conveniently built on stainless-steel skids with wheels, allowing for effortless manoeuvrability within the laboratory environment.

Perfect for R&D projects, experiments and for fine tuning processing parameters, laboratory-scale dryers are available in sizes from 5 litres to 20 litres, while the capacity range of the larger, pilot-scale versions is between 40 litres and 120 litres.

cGMP Processing – Pharmaceuticals

Contamination is completely unacceptable when processing material for use in pharmaceuticals and Hosokawa Micron has a great deal of experience creating high-performance processing and containment equipment for the largest blue-chip companies in the pharma industry, a sector that operates under incredibly tight quality and safety restrictions.

Our Nauta® Conical Screw Dryers are renowned for their excellent cleaning in place (CIP) and sterilising in place (SIP) technology and designs, which boast a number of features to eliminate any risk of contamination.

A closed processing vessel with one-piece cover and filter, which eliminates dead spots and facilitates validated automatic CIP and SIP, is just one benefit. Another benefit is the absence of oil or other lubricants inside the orbital arm, eliminating the risk of possible leakage and contamination. We have also designed a sanitary mixing screw with open flights, plus positioned the discharge outlet at the bottom of the cone to allow gravity to effectively remove the material from the vessel. The discharge valve includes a smart system that hermetically seals off the drying vessel from the equipment below it.

Our special cGMP designs also incorporate mechanical seals and samplers, while fixed mounted spray balls and spray nozzles designed for CIP and SIP are integrated into the dryers and their filters. Plus, the gentle mixing action of the orbital arms and mixing screws makes Nauta® Conical Screw Dryers an ideal option when producing delicate crystals.

The Nauta® Conical Screw Dryer is used for batch drying granules, powders, pastes and viscous slurries. The dryer’s thoughtful, high-quality design means it can handle heat-sensitive, toxic, heavy, sticky, brittle and explosive products, as well as those containing solvents. The versatility of the engineering also makes the Nauta® Conical Screw Dryer perfect for cooling, crystallisation, alkalisation, sterilisation, de-aeration of pastes and liquids and the wet agglomeration and granulation of solids.

Typical applications include steam-sterilising food products, such as herbs, spices and tea leaves; small-volume batch drying of active battery materials, such as nickel, manganese and cobalt oxide, for making battery cathodes; drying toxic, thermo-sensitive chemicals for the production of pesticides; vacuum drying large batches of CPT (chemical toner) at low temperatures without melting or agglomerating the material; mixing and secondary drying antibiotics and sterile and non-sterile active pharmaceutical ingredients to cGMP, FDA and GAMP standards; drying contaminated nuclear material prior to immobilisation and long-term storage, plus gently mixing and drying challenging high density metal powders (including oxidisation-prone hydroscopic powders) for use in the additive manufacturing industry. The dryer can also be used for recycling 3D printing powder by mixing it with virgin material.

For laboratory-scale processing and R&D, our 5 litre Nauta® Conical Vacuum Dryer is ideal for reliable, scalable experimentation.

  • Robust universal batch dryer
  • Based on the legendary Nauta® Conical Screw Mixer
  • Processes everything from loose powder to heavy pastes and viscous liquids
  • Handles heat-sensitive, toxic, explosive and solvent-containing material
  • Effortlessly processes sticky, brittle and heavy materials
  • Available in grades of stainless-steel, Monel, nickel, titanium, Hastelloy etc
  • Standard and bespoke capacities (up to 22,000+ litres)
  • Laboratory-scale 5 litre version available
  • Excellent drying efficiency with no segregation or product degrading
  • Energy-efficient processing
  • Economic multi-purpose and multi-processing capabilities
  • Interchangeable screw agitator for 20,000+ litre models
  • Patented automated cleaning solutions (CIP/SIP) available
  • Simple design is easy to clean and maintain
  • Dust protection features
  • Sterile and aseptic designs available for food and pharmaceuticals
  • cGMP, GAMP, ISPE, FDA, EHEDG and ATEX-standard models and systems available
  • Custom-made powder drying systems and plants available
  • Laboratory-scale in-house feasibility tests
  • In-house pilot-scale tests (up to 6,000 litres)
  • Product trial documentation
  • Full testing and validation service, including FATs
  • Document packs for certification and materials traceability
  • Full operating manuals supplied
  • Site installation, commissioning and maintenance service

Hosokawa Micron’s reliable, high-performance Nauta® Conical Screw Dryer offers excellent batch drying capabilities using the vacuum method, effectively removing moisture from materials such as loose powders, granules and viscous slurries, including products that can be problematic to process – including thermo-sensitive, brittle, sticky, toxic and explosive materials.

Based on the ground-breaking innovations of Hosokawa Micron’s iconic Nauta® Conical Screw Mixer – an equipment staple for thousands of processing companies worldwide for more than 70 years – the Nauta® Conical Screw Dryer shares the same mixing technology and has been developed in tandem with the mixer version to include, for example, a re-designed and upgraded mixing screw, which is now cantilevered. The original design has also been adapted to meet the highly regulated food, chemical and pharmaceutical industries, which demand excellent standards in terms of mixing capability, cleanliness and hygiene.

Materials are introduced into the wider part of the conical-shaped drying vessel from the top. The vessel’s rotating, cantilevered mixing screw then conveys the material from the bottom of the narrower section of the cone up to the top of the product mixture and out along the heated vessel wall.

The mixing screw operates at a low intensity with an average speed of 70 rpm, helping to preserve the integrity of the product and guaranteeing the highest level of mixing accuracy. Suspended from an orbital arm that rotates at 1 to 2 rpm, the position of the mixing screw allows for its rotation against the inner wall of the conical vessel – which is a highly efficient way of enabling accurate convective mixing of particles and shear – with axial mixing provided by the screw, radial mixing provided by the shape of the vessel and tangential mixing provided by the orbital arm.

So, material travels upwards to the wider part of the cone-shaped vessel and is then forced downwards by gravity into the narrow section, gaining speed as it recirculates to provide energy-efficient, fast and intensive mixing.

The drying process is enabled by a heated jacket, which is integrated into the cone-shaped vessel and provides rapidly distributed thermal energy via steam, hot oil and water. Combining the advanced technology of the mixing and drying processes ensures the material is being efficiently mixed and dried simultaneously.

The action of the mixing screw helps the inevitable vapour to escape from the surface as the particles in contact with the side wall of the vessel dry and constantly replace. As it does so, a dust filter captures any dust particles contained in the vapour.

Vapour is extracted and removed from the drying material by vacuum at low temperatures, making the Nauta® Conical Screw Dryer ideal for processing challenging materials that are heat sensitive.

The dryer is also perfect for drying materials containing solvents, thanks to an optional condenser, which incorporates a solvent recovery tank. The drying and processing time is dependent on the heat conduction of the solid particles and solvent, the pressure and temperature conditions, as well as the speed of the mixing screw.

Measuring the moisture content of the material is easy and can be controlled by establishing the weight of the condensation by monitoring the system or by analysing the drying material using a sampler to extract a sample for testing.

In addition to vacuum drying, the multi-purpose Nauta® Conical Screw Dryer can perform many additional tasks which require thermal processing or vacuum treatment of materials, such as alkalisation, material cooling, crystallisation, de-aeration of pastes and liquids, product sterilisation and wet agglomeration and granulation of solids.

HSSP Sterile Processing – Food

For heat treatment of food products such as tea leaves, herbs and spices, a six-step flexible batch sterilisation process known as HSSP can be performed by the Nauta® Conical Screw Dryer, of which five processes are automated.

First, the raw material is manually loaded into the dryer. Then, the operator selects a ‘recipe’ from the control system, beginning the sterilisation process. The dryer is put under vacuum, heat is added via the vessel’s jacket and the mixture is homogenised. A quick injection of steam minimises any loss of product quality. The post-drying stage allows the condensed water to evaporate under vacuum conditions, while a cooling water condenser traps any evaporated water vapour and natural oils in the product. Next, the product is cooled under atmospheric conditions and at this stage, any oils that were extracted by the previous processes can be reintroduced, if required. When this process is complete, the sterilised product is ready to be discharged from the equipment and bagged or loaded into containers. Any lumps that have developed in the powder are removed as the powder is discharged.

Aseptic and Sterile Processing – Pharmaceutical APIs

Active pharmaceutical ingredients (APIs) need to be processed under strict sterile and aseptic conditions to ensure the safety of the operators, the environment and the integrity of the ingredients themselves. Many factors need to be considered and specialist components need to be chosen for the design, such as the correct flanges, static seals and mechanical seals, a suitable sampler system, the sterilisation philosophy and validation, the battery limit and separation of sterile/aseptic, how the condensates will be recovered and how the temperature will be controlled at critical points inside the process system. In addition to the Nauta® Conical Screw Dryer, Hosokawa Micron Ltd can also supply a wide range of sophisticated, bespoke containment equipment, including isolators, glove boxes and downflow booths.

Hosokawa Micron’s Nauta® Conical Screw Dryer can be supplied as an individual piece of equipment but is typically purchased by our customers as the centrepiece of a bespoke, Hosokawa Micron-designed, vacuum drying process system. Comprising a collection of necessary additional equipment that supports the vacuum drying and mixing functionality of the Nauta® Conical Screw Dryer, we also offer a range of optional features to further enhance your process system’s functions.

Typically, a custom-made process system for drying powders and bulk solids would comprise a reliable feeding system to provide a uniformly constant feed rate of material into the dryer, ensuring excellent process efficiency and a superior end product. The Nauta® Conical Screw Dryer itself would require additional apparatus to effectively complete its drying operation, such as skids for heating or cooling the dryer, an air heater (compatible with steam, electricity or gas), compact condenser/vacuum skid options and a receptacle, eliminating the need for large vacuum pump systems and reducing solvent emissions.

In addition, there is a range of equipment options for end product recovery, dependent upon factors such as product characteristics and process parameters. For peace of mind, all our process systems for mixing and drying powder are made to the latest ATEX standards to prevent dust explosions. We will happily advise you on the best option for recovering the dry material, whether that’s a cyclone, filter or something else.

Finally, our cutting-edge control and process automation technology is optimally integrated to provide a consistent-quality end product. The sophisticated, ergonomic and visual HMI-PLC panels offer essential information on your drying system’s performance, with features such as lot traceability, remote monitoring, smart alerts, operator identification, remote servicing information and customised reporting.


Here at Hosokawa Micron, we have a wealth of expertise to share regarding powder processing systems for both batch and continuous drying and mixing. The company has been pioneering specialist processing equipment and techniques for more than a century, designing and manufacturing industry-leading vacuum dryers and turnkey vacuum drying systems for customers worldwide. We also offer valuable expertise regarding process guarantees and validation, plus a wide range of after sale lifecycle services ­– including genuine spare parts, maintenance and training packages, upgrades and repairs and in-house contract manufacturing.

We are specialists when it comes to creating the optimal tailor-made process system for your specific requirements, with innovative solutions meeting the demands and challenges of the materials you wish to process, now and in the future. Before the initial design and engineering phases even begin, our highly respected technical processing specialists make it their priority to thoroughly understand your existing processes and the requirements for your new processing equipment or system to ensure we supply the high-performance equipment you will be able to rely on for decades to come.

Hosokawa Micron is also delighted to offer an in-house R&D service, testing your existing or in-development products at our state-of-the-art testing and process development centre using examples of the equipment you are interested in acquiring. We provide laboratory-scale, as well as production-scale trials, with accurate scale-up data, full documentation and sample materials supplied. Collaborating with your technical team, we will work together to ensure you are 100% happy with the final equipment design, functionality and performance capabilities before it reaches the manufacturing stage.

We spend an awful lot of time, money and resources continually developing our processing techniques and equipment to bring to our customers equipment and powder processing systems that are as energy efficient as possible. And, with material drying typically accounting for around 15% of energy consumption during the manufacturing process, we appreciate the increasing importance of supplying energy-saving solutions for economic, as well as environmental reasons.

Hosokawa Micron’s latest innovations for drying equipment and process systems include reducing their energy-loss and enabling any excess heat to be recovered and reused, plus integrating the latest energy-efficient IIoT technology and smart controls, plus remote monitoring and remote routine servicing, repairs and maintenance (where appropriate) with dynamic software tailor-made for your equipment.

Our intention is to deliver the highest quality, best performing processing equipment available anywhere on the market while striving to also find the most affordable solutions for you, as well as the most energy efficient.

The Nauta® Conical Screw Dryer is based on the Nauta® Conical Screw Mixer, which was originally designed to blend pulverised material, such as flour. Invented and patented in the Netherlands in 1939 by Johannes Ewardus Nauta (1890-1957), the engineering innovation completely transformed powder processing mixing technology and was instrumental to the success of the Nautamix company in the mid to late twentieth century – in no small part due to the mixer’s patented, cone-shaped, mixing vessel and, almost vertical, conveyor screw that rotated around the perimeter of the vessel, causing highly efficient three-dimensional mixing for the first time.

In fact, the iconic Nauta® Conical Screw Mixer continues to be the ‘gold standard’ for processing industries throughout the world and is one of the most popular products in the Hosokawa Micron product portfolio, since the Nautamix company was acquired by Hosokawa Micron Group back in 1982.

Following the acquisition, Hosokawa Micron has exploited and developed the technology of the original Nauta® Conical Screw Mixer and, using our pioneering expertise in mixing for powder processing, have improved both the mixer and the dryer by integrating more modernised components and the latest fabrication and engineering techniques – such as the introduction of a cantilevered mixing screw, for quick and full central discharge from the bottom of the vessel, and engineering hygienic designs that allow for high-end pharmaceutical and food processing. Both products are now more energy efficient, too.

From batch processing APIs, tea leaves, food colourants, cosmetic powders and baby formula, to battery materials, nuclear waste, biopesticides and household detergents, the multi-purpose Nauta® Conical Screw Mixer is world-famous for its versatility and efficient, low intensity, mixing action. The mixer is particularly suited to precisely processing delicate products in volumes of up to 100,000 litres.

Working on the same principles as the Nauta® Conical Screw Mixer, the addition of a heat jacket, vacuum capability and auxiliary components (used in combination for the extraction of the vapour produced by the drying particles) has adapted this ground-breaking mixing equipment into an efficient batch dryer, known as the Nauta® Conical Screw Dryer.

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Having chosen Hosokawa Micron Ltd to design, manufacture and install your powder and particle processing equipment, you can also trust us to ensure it continues to perform correctly and optimally, protecting your investment while giving you peace of mind.
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