- 11/04/2026
- Article
- Preparation & dosing
Processing mineral raw materials: Material properties determine the process
Understanding materials, optimising processes: Numerous technical presentations at the EXPERT FORUM at POWTECH TECHNOPHARM 2026 highlighted the key considerations in processing mineral raw materials.
Written by Marius Schaub
Demanding product specifications, wear, variable material quality and complex process chains – processing mineral raw materials involves a range of interrelated challenges. The EXPERT FORUM at POWTECH TECHNOPHARM 2026 brought these into focus through concrete examples, such as the task of drying bleaching earth from a moisture content of 25 to 10 per cent while reducing its particle size so that 97 per cent of the final product is smaller than 63 micrometres.
Lucas Nievelstein of NEUMAN & ESSER presented this challenge in his talk, using a plant project in Indonesia as an example. He explained that success had depended not only on selecting a suitable mill, but also on the overall interaction between drying, size reduction, air classification and hot gas management.
The application illustrates a broader question in mineral processing: How can processes be matched to the feed material and the required product quality? The technical presentations at the EXPERT FORUM offered different perspectives, ranging from powder characterisation and simulation to combined grinding and drying, classification, compaction and filling.
Material characterisation as the basis for process design
Before a plant can be optimised, the behaviour of its feed material must be understood. Claas Bierwisch of the Fraunhofer Institute for Mechanics of Materials explained that bulk solids were defined by numerous properties, including particle size distribution, particle shape and surface characteristics. A single measured value was therefore insufficient to distinguish between these properties. According to Bierwisch, different test methods also tended to capture either static or dynamic aspects of material behaviour.
With the Flowboard, he presented an approach that made material flows visible in a transparent container with adjustable obstacles. The observed flow patterns provided information on factors such as wall friction and behaviour during particle collisions, while also serving to calibrate models for the discrete element method.
Bierwisch explained that this provided a basis for investigating process variants virtually before undertaking costly modifications. The examples ranged from screw conveyors and silo discharge systems to stirred media mills, where forces, stresses and residence times could be analysed.
Grinding and drying: Balancing moisture and fineness
Lucas Nievelstein’s bleaching earth project demonstrated how strongly a single material property can influence the design of an entire plant. The project used a hammer mill followed by a drying section and an air classifier. The plant achieved a throughput of 6 tonnes per hour and reduced the moisture content from 25 to 10 per cent.
The central challenge was to supply sufficient heat for drying without thermally overloading the mill. Nievelstein explained that the hot gas flow was split for this purpose. One stream enters the hammer mill, while another feeds directly into the downstream drying section. This allows heat to be supplied where it is needed for drying while limiting the thermal load on mill components. To achieve more uniform drying within a compact section, Nievelstein described a component known as the D-module. Its internal elements induce swirl in the flow. The flow simulation presented illustrated more uniform drying than in a simple pipe section.
Nievelstein emphasised that a realistic assumption about feed moisture was particularly important. Higher moisture levels not only changed the heat demand, but could also require larger air volumes and modifications to fans, mills or classifiers. Measurements of temperature, pressure and volumetric flow rate subsequently supported operational monitoring and component protection; pressure drops, for example, could indicate build-up and constrictions.
Screen classification: The separation task determines the technology
Alongside moisture content, the right particle size is essential to the required product quality. Stefan Bormann, Product Manager for Screening Machines at Siebtechnik, presented a screen classification concept in the form of the Multiple Deck Sizer. He explained that the machine operated with screen decks set at different inclinations. This allows larger mesh openings to be used for the same cut size, reducing pegging. At the same time, the material’s short residence time enables a compact design.
Maintenance and wear protection must be matched to the application: Bormann described accessible screen panels, different wear-resistant linings and the option of rotating panels through 180 degrees following inspection to extend their service life. The energy-efficiency approach includes short screen panels, a compact design and smaller motors.
Compaction: Targeted powder densification
Not every processing task aims at further size reduction. At the EXPERT FORUM, Patrick Schönfeld of Hosokawa Alpine explained how compaction could increase bulk density, influence flowability and reduce dust generation. In pressure agglomeration, two counter-rotating rolls compress the powder; to produce granules of the required particle size, the compacted material is then crushed and classified.
The fines generated can be returned to the compactor, while oversized material undergoes further size reduction. Schönfeld’s colleague Sonja Seiler added that the feed material, product requirements and site conditions were decisive factors in the plant concept. She used a highly abrasive material to illustrate the importance of wear protection. In the solution presented, the powder is mixed with a binder before compaction. Segmented roll rings facilitate on-site replacement and reduce downtime. A reduced roll speed and protective materials such as tungsten carbide and aluminium oxide also reduce wear.
Bagging technology matched to the material flow
Matching equipment to the material does not stop at the processing plant’s discharge point. Lars Wagner, Managing Director of Wagner Maschinen, explained that the selection of dosing and filling equipment depended on factors including the bulk material’s flow behaviour, abrasiveness, moisture content and stickiness. Other considerations include packaging formats, the required throughput, cleaning requirements and the frequency of product changeovers.
Wagner emphasised that the level of automation needed to suit the production profile. Large volumes of a consistent product in uniform packaging favoured a fully automated solution. By contrast, frequent changes in materials and packaging increase the importance of flexibility, accessibility and quick cleaning. Trials using the actual products can help assess not only filling performance, but also the time and effort required for changeovers and cleaning.
Conclusion: Practical expertise for mineral processing
The EXPERT FORUM examples show how closely material properties, product requirements and plant design are linked: Reliable characterisation supports design, while moisture control, classification, compaction and material handling each require application-specific decisions. Neither a universal process nor an isolated focus on energy consumption can replace this tailored approach.
This is where the highly application-specific value of the presentation programmes at POWTECH TECHNOPHARM lies: The technical insights not only offer solutions, but also make their prerequisites and limitations clear. Numerous presentations demonstrated this for the handling of mineral raw materials, providing practical starting points for planning and optimising participants’ own processing operations.
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