HIGH ENERGY BALL MILL
HIGHLY EFFICIENT LIQUID COOLING
The grinding jars of the Emax are cooled by an integrated water cooling system. To further reduce the temperature, the mill can be connected to a heat exchanger or the tap.
Figure 6 shows the cooling circuit of the Emax. The grinding jars are cooled via the jar. The cooling system is very effective because heat is more easily discharged into
water than into air. The Emax software allows the user to carry out the grinding process within a defi ned tem- perature range, i. e. he can set a minimum and a maximum temperature. When the maximum temperature is exceed-
ed, the mill automatically stops and starts again upon reaching the minimum temperature.
Cooling can be an essential advantage, especially if heat-sen- sitive samples are processed or if isopropanol has been added to the sample (fi g. 7). Isopropanol evaporates at 82 °C which makes the pressure inside the jar rise considerably. If the temperature remains below this value, the pressure inside the jar and the stress on the sealing are reduced. Moreover, the grinding jar can be opened shortly after the grinding is fi nished.
Cooling circuit Emax
Wet grinding of graphite in the Emax [°C] grinding jar inlet cooling water
cooled area (heat transfer)
outlet warmed water
140 120 100 80 60 40 20 0
0 4 8 12 120 °C
78 °C
air and water cooling (1 mm balls) air cooling only (1 mm balls)
16 grinding time Fig. 6: The grinding jar is cooled via the jar brackets. 20 24 28 [min]
Fig. 7: When grinding graphite with isopropanol (50 ml jar, 1 mm balls, 5 g sample), the warming of the grinding jar could be limited to 78 °C thanks to the liquid cooling. Without water cooling the temperature was 120 °C.
MAXIMUM SAFETY
During product development of the Emax special attention was paid to operational safety. The position of the grinding
jar is automatically monitored, so that the mill cannot be started if the position is not correct. No counterweight is required to operate the Emax. Possible imbalances are
controlled at all times. If they become too strong the mill automatically stops. The remaining grinding time is displayed and the process can be re-started once balance has been restored.
Conclusion
The Emax opens up a new dimension in high energy milling. The unique combination of friction and impact as well as the revolutionary speed of 2,000 min-1
permit the production of ultrafi ne particles in the shortest amount of
time. Thanks to the unrivaled liquid cooling system the Emax generates substantially more grinding energy than con- ventional planetary ball mills – without overheating. Moreover, the water cooling allows for a signifi cant reduction of
the grinding time compared to ball mills without cooling that require grinding breaks. The examples shown in this
article impressively demonstrate that the Emax achieves the desired grind sizes in a fraction of the time required by comparative ball mills.
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