The Andritz GHD vacuum helix dryer series has been improved and optimised with a more effective mixing action and maximum product discharge.
Improved mixer for maximum product discharge
Batch dryer with optimum design
The Andritz GHD vacuum helix dryer series has been improved and optimised with a more effective mixing action and maximum product discharge.
The wet product is transported gently upwards by the helix spiral along the heated vessel wall, then flows downwards again on the inside of the machine along the centre shaft in the same way as with the predecessor models in the Krauss-Maffei product series (HD and BD). In addition to vertical mixing, the support bars between the agitator shaft and the helix also ensure good cross mixing, creating a homogeneous mixture. The evaporation temperature is reduced by applying a vacuum, so that temperature-sensitive products can likewise be dried efficiently.
As a rule, very expensive products such as pharmaceuticals, special chemicals or precious metals are dried in the new helix dryer series, which is why special emphasis was placed on optimal product discharge. Any build-up of product on the mixing element or in the vessel must be prevented, so that no residual matter is lost in the subsequent cleaning stage. With this in mind, the following design changes were implemented:
- Steeper upper helix, perpendicular to the vessel wall, allows the product to slide off easily (Figure 1).
- Patented double-cone vessel design with a steep side wall ensures good blending in the product discharge zone and guarantees full product discharge.
- Optional triangular support bars between the centre shaft and the helix reduce the probability of product deposits forming compared to the standard round profile design. In addition, the number of support bars required has been reduced, together with the number of surfaces on which deposits can form, because the optimised helix is set at a steeper angle.
- Heated agitator (= optional heating of the upper helix blade including the agitator shaft), which not only shortens the drying time due to the additional energy input but also prevents condensation or dust deposits on agitator parts that may protrude beyond the filling volume.
The operator can thus achieve the maximum yield in every batch, especially with bulk products exhibiting high internal friction and correspondingly poor flow properties and also in large industrial dryers, because very little product is deposited in the machine.
Following a comprehensive field study and intensive drying tests, the design of the GHD series was defined as a new standard with the support of the Andritz batch dryer competence centres in Germany, the USA and the Netherlands, enabling more efficient drying technology to be offered to users worldwide.
Cleaning without dead zones
Depending on the application and the specific requirements, various CIP cleaning concepts are now possible that are better suited to the high standards of pharmaceutical or dye manufacturers than the traditional, stationary CIP nozzles on the vessel cover. By using rotating cleaning lances, there are no dead zones in the cleaning process, and all fittings on the top cover can be cleaned individually and fully automatically. An additional, optional design feature also allows specific cleaning of the surfaces on the underside of the helix. Thus, the vessel does not need to be completely flooded, and this results in reduced utility consumption in the CIP stage, especially in large machines.
As with the previous series, the equipment is suitable for toxic applications because it complies with OEL (occupational exposure limit) requirements, guaranteeing protection of both personnel and the product. In addition, special concepts have been developed to guarantee that components like the filter elements can be disassembled free of contamination and dust after product changes.
From small scale to production scale
The helix dryer series is available in lab, pilot and production scale sizes from 8 l to 10 m3 useful volume (Figure 2). The pilot range is supplied with a hinged top cover up to a useful volume of 150 l, allowing easy inspection of all parts inside the vessel plus the agitator helix which come into contact with the product (Figure 3).
Small sizes are also available as a mobile unit. A transport frame and a version on wheels allow more flexible operations as the dryer can be docked to a pre-process step, for instance a centrifuge, for filling purposes. In addition, the machine serves as a container for transporting the pre-dewatered product to a central drying station, where it is dried thermally to the required final moisture content (Figure 4). The height of the transport frame can be adjusted in accordance with the user’s requirements, with the added benefit that the product can be discharged directly and free of contamination into suitable packaging.
Complete process lines available
Andritz Separation simultaneously offers entire process lines, including pre-dewatering by means of peeler centrifuges, decanters or filter presses, as well as product transfer systems to charge the batch dryer. All essential dryer peripherals such as vacuum skids, heating/cooling units or discharge solutions can likewise be supplied. The mixing device in the GHD helix dryer is suitable for all product consistencies, no matter whether the material is free-flowing, sticky, pasty or highly viscous. Owing to its great flexibility, this equipment is predestined for multi-purpose production plants. The complete line can be optionally equipped with a control system that controls and monitors all process steps and communicates with the main plant control system via a Profibus connection.
Due to the certified safety and inertisation measures, the machine can process products containing solvents and is suitable for installation in hazardous areas.
Testing and sizing
Tests can be carried out with customer products on test centre pilot plants in Germany, the Netherlands or the USA. Alternatively, the pilot plants can be rented out in order to perform tests on site.
Feasibility and sizing tests enable guarantees to be provided for process parameters, such as the drying time or the final moisture content for new equipment, and recommendations given regarding the most effective operating conditions or the most efficient equipment size. To assure maximum customer benefit, the ideal process parameters are set by the Andritz automation and commissioning experts when the equipment is first put into operation.
Hall 3A, Booth 246
www.cpp-net.com search: cpp0116andritz
Karolin Schröder
Karolin Schröder
Product & Sales Manager Dryers,
Andritz Gouda
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