A Rosenmund agitated Nutsche filter dryer separates a solid from its slurry, washes it and dries it inside one closed vessel. That saves a transfer step, limits operator contact with the product and keeps a batch together. It also means the machine does several jobs at once, so there is more to check on a used unit than on a simple filter.
This guide covers how these units work, what their main design features mean, how the Rosenmund, Guedu and De Dietrich names fit together, and what to confirm before you send a purchase request. For a general overview of the brand, see our Rosenmund page. If you are comparing other filter types, such as filter presses or rotary drum filters, start with our filters page.
How an Agitated Nutsche Filter Dryer Works
A typical cycle follows seven steps inside the same vessel:
- Filling: the slurry is charged into the vessel above the filter plate.
- Filtering: gas pressure from above or vacuum from below drives the liquid through the filter media, and the solids build up as a cake.
- Displacement washing: wash liquid is pushed through the cake to carry impurities away.
- Reslurry washing: the agitator mixes the cake back into wash liquid for a more thorough rinse.
- Smoothing: the agitator levels the cake surface.
- Drying and cooling: heat and vacuum or gas flow remove the remaining liquid, and the vessel then cools the product.
- Discharging: the finished product leaves through a side discharge valve or is blown out with a gas knife.
Because the cycle is closed, these machines are common in pharmaceutical and fine chemical plants where containment and clean handling matter.
Filter or Filter Dryer?
Rosenmund offers both a filter version and a filter dryer version of the same basic design. The filter separates and washes. The filter dryer adds the heating features needed to dry the product in the vessel as well. Rosenmund says its filters can be converted to filter dryers by adding upgraded features, though whether a particular used unit can be converted depends on its design and condition, so ask us before you plan on it.
Rosenmund has also built combined reactor, filter and dryer systems under the Nutrex name. If you see that name on a nameplate or a drawing, you are looking at a more specialized unit.
Rosenmund, Guedu and De Dietrich: What the Nameplate May Say
The brand names overlap. Guedu was integrated into Rosenmund, and Rosenmund has been part of De Dietrich Process Systems since 1999. As a result, a used unit may be marked Rosenmund, Rosenmund-Guedu or De Dietrich, depending on when it was built.
Search for all three names when you look for drawings and documents. We list Guedu equipment and De Dietrich equipment separately, so it is worth checking each page when you browse inventory.
Design Features and What to Check on a Used Unit
| Feature | What it does | What to check used |
|---|---|---|
| Agitator | Two- or three-blade agitator that mixes during washing, smooths the cake and helps discharge. | Blade wear, shaft seal condition and the lift and drive mechanism. |
| Side discharge valve | Metal-to-metal sealing valve that closes pressure-tight after each discharge. An Easiclean version suits manual cleaning with difficult products. | Seat and seal condition. Worn O-rings here can trap product. |
| Gas knife | Blows the product out for near-total discharge without manual intervention. | Whether the system is installed, and the nitrogen or air supply it needs. |
| Filter plate and media | Holds the filter media. Rosenmund’s universal design accepts cloth, a single-layer metal screen or multi-layer sintered metal. | Media type and condition, mesh clogging and plate flatness. Some designs avoid screws on the plate for easier cleaning. |
| Heated plate and jacket | Supplies the heat for drying. | Heating system type, leaks and the services you will need to connect. |
| Main closure | Quick-lock bayonet or C-clamp that splits the vessel for access to the internals. | Clamp wear, seal condition and alignment. |
| Materials | Stainless steel, Hastelloy, other alloys or glass lining, depending on the service. | Corrosion, pitting and, on glass-lined units, chips or cracks. |
| Cleaning systems | Clean-in-place and steam-in-place systems for cGMP use. | Spray device condition and the steam and drain connections. |
Sizes and Operating Ranges
Rosenmund sizes these units by nominal filter area, which runs from about 0.03 up to 16 square meters in its standard series, with smaller lab units below that. Vessel volume grows with filter area. In the manufacturer’s examples, a 1 square meter unit has a vessel of about 1 cubic meter, and a 16 square meter unit about 17 cubic meters. The cake the unit can hold is a fraction of that volume, roughly 40 percent in those examples.
Rosenmund’s published capabilities for the line include operating pressures up to 90 psig and full vacuum, and temperatures from -30 to 220 degrees Celsius. Treat those as the range for the product line. The nameplate on the unit you are considering is what counts.
Is an Agitated Filter Dryer the Right Fit?
These units work best for crystalline or granular solids that filter and dry at reasonable rates, especially where containment and a single vessel for the whole batch are priorities. A few limits are worth keeping in mind:
- Hard-to-filter products: amorphous or very fine solids can blind the filter media and slow the cycle.
- Throughput: combining two operations in one vessel can turn the unit into a bottleneck if filtering or drying runs slowly.
- Cleaning time: in multi-product plants, cleaning between products can take as long as processing.
Some plants compare a filter dryer with a centrifuge for the same job. You can browse those on our centrifuges page.
What to Confirm Before You Buy
We sell equipment as inspected and as-is, so the more detail you share, the better we can match you. These are the points that most often decide whether a used unit fits.
- Nameplate: manufacturer name, serial number, year, code stamp, and design pressure and temperature.
- Filter area and cake capacity: compare both with your batch size and expected cake volume.
- Wetted materials: check the vessel, agitator and plate materials against your solvents and chemicals.
- Agitator and seals: confirm the shaft seal type, the drive and the lift mechanism.
- Discharge: check the type of valve, its seals and whether a gas knife is fitted.
- Filter media: confirm the type and condition, and whether spare media is available.
- Heating and cooling: confirm what services the plate and jacket need.
- Controls: note whether the unit is manual, semi-automatic or PLC-controlled, and whether the interlocks are intact. Check the electrical rating against your area classification.
- Condition: look for corrosion, scratches, glass lining damage and product buildup in the O-ring grooves.
- Paperwork: ask for drawings, material certificates and any cleaning or validation records on file.
Rosenmund Filter Dryer FAQs
What is the difference between a Nutsche filter and a Nutsche filter dryer?
A Nutsche filter separates and washes solids. A filter dryer does the same and also dries the product in the same vessel, which needs a heated filter plate or jacket and a way to pull vapor off. Both can have an agitator.
Is Rosenmund the same as Guedu or De Dietrich?
They are connected. Guedu was folded into Rosenmund, and Rosenmund has been part of De Dietrich Process Systems since 1999. Older units may carry any of the three names.
How do I size a filter dryer for my batch?
Start with the cake volume you expect from one batch, then compare it with the unit’s cake capacity rather than its total vessel volume. Add headroom for the agitator and for any reslurry washing.
Can I convert a used Rosenmund filter into a filter dryer?
Rosenmund designs its filters so they can be upgraded, but each used unit is different. Send us the nameplate and we can tell you what we know about the one you are considering.
What should I send to get a quote?
Send the model and serial number if you have them, along with your product, solvents, batch size, required materials and whether you need a filter or a filter dryer. A nameplate photo helps a lot.
Send Us Your Filter Dryer Requirements
Our team can help you find a used filter dryer that fits your process, your materials and your schedule. Browse the Rosenmund units currently listed, search our full filter inventory, or submit a purchase request with your nameplate details. You can also use our contact form or call +1-866-289-5232.
