After pyrolysis, an intermediate process step is required. The carbon black granules are pre-crushed and prepared for the fine grinding stage using a magnet/metal separator. For fine grinding, Hosokawa Alpine primarily uses the TDG fluidised bed opposed jet mill with integrated dynamic high-performance classifier. Everything is possible here, from the very highest fineness to coarser levels. The TDG optimises the conversion of compressed grinding air into jet energy via nozzles positioned opposite each other. The proven hot gas process with low pressure is used here, which results in efficient grinding. The NG classifier wheel with bearings on both sides ensures excellent selectivity and upper particle size limitation. The uniform product flow minimises the wear load on the classifier wheel. The large free surface of the classifier enables high throughput rates even with the highest fineness levels.
The advantages at a glance:
- Covers the fineness range between d97 = 4 – 40 μm through a simple change of the classifier wheel speed (flexibility)*
- Steep particle size distribution with exact upper particle size limitation due to excellent selectivity (quality)
- High throughput rates with very fine end products (OPEX)
- Minimised wear load (OPEX)
- Selective grinding combined with automated discharge of foreign particles from the grinding chamber (OPEX/quality)
- Reduced investment and operating costs due to low-pressure grinding with hot gas, energy-saving NG classifier wheel and compact design (CAPEX/OPEX)
- Reduced personnel costs due to high degree of automation and remote control (OPEX)
- System concepts according to CE and ATEX directives (safety)
* Direct customer benefit in brackets, e. g. more flexbility, positive influence on costs
The TDG grinding system is continuously supplied with feed material via a dosing unit. Low compressed hot gas is supplied at the same time. The end product is discharged from the system in a controlled manner for further processing. This is ensured by a specially designed bag filter and a regulated extraction fan. One special feature is the time-controlled discharge of foreign particles directly from the grinding chamber. The safety concept of the grinding system is adapted to fit each different grinding material. The valid ATEX directives are always applied.
1 Feeding system 2 TDG Fluidised bed opposed jet mill 3 Discharge unit for foreign particles 4 Bag filter
5 Explosion protection valve (only for pressure-shock- resistant version) 6 Exhaust fan 7 System control 8 Impurities (e.g. metal particles)
Hosokawa Alpine has worked out a comparison of classical particle analysis methods based on laser diffraction. This study was carried out in close cooperation with the ASTM committee. The objective was to contribute to the standardisation of the fineness determination for the various end product qualities of recovered carbon black. Using the correct measuring method can have a decisive influence on the correct system design. Therefore, a clear definition of the analytics is important here.
The mechanical classifier mill ACM is the right choice for medium product finenesses or if the ash content in the raw carbon black feed material is only present in moderate quantities.The coaxial drive system and optimum coordination between the rotor/stator grinding sector and the classifier wheel located in the centre ensure a continuous production process. The modular design of the grinding elements and classifier wheel facilitates access for replacing wear parts.
The advantages at a glance:
- Covers the industrially required fineness range of d97 = 15 – 40 μm
- Simple adjustment of the end product fineness via the classifier wheel speed
- Easy Clean design in modular construction for quick replacement of wear parts in the grinding area (for certain sizes)
- Robust drive system via the proven coaxial bearing
- Space-saving due to compact design
- System concepts based on the applicable CE and ATEX directives
Together with our partners from the Hosokawa Micron Group, we can cover additional process components in the finishing of Recovered Carbon Black - from mixing to storage:
- Pelletising & drying: The pelletising systems from Hosokawa Micron B.V. first of all consist of a mixer to mix the finely ground carbon black together with the binding solution. After mixing, the wet carbon black pellets need to be dried in order to produce easy-to-handle, dry and stable pellets. Mixing can be done with either the Flexomix high-impact mixer or the Mars Mineral Pin Mixer. After the mixing is complete, the drying process takes place in a specially designed fluidised bed dryer directly under the mixer. The mixing and drying processes are continuous and can be tested at the test centre of Hosokawa Micron B.V. in Doetinchem, the Netherlands.
- Conveying, storage, dosing and weighing: During the entire production process, the Carbon Black has to be conveyed, stored, dosed and weighed, often more than once. You will find the appropriate technologies for these process steps at our partner Hosokawa Solids.
