The general principle of operation in a fluid energy mill is that the mineral to be ground is fed into a grinding chamber in a high speed, high pressure and, often, high temperature jet of air (or other gas). The particles collide violently and this causes comminution to take place. Various designs of fluid energy mill exist, the most common being the microniser. This mill has a shallow circular grinding chamber and a series of peripheral jets set tangentially to a common circle. The turbulence causes bombardment which effects a rapid reduction in particle size. A centrifugal classification system keeps larger particles within the chamber while allowing fine particles to leave. In a well designed fluid energy mill there will be almost no contact between the charge and the mill lining.
Fluid energy millsCharacteristics
Suitable for hard or soft materials to be reduces to 0.02mm or less. This method of milling tends to be energy intensive and slow but is suitable where the product is highly sensitive to heat or contamination from grinding media.
Typical jet mill performance
Mineral
Product size
Production
(Kg / hr)
Fluid use
Alumina
100% – 0.0075mm
50% – 0.003mm
5500
2850 kg/hr steam at 7000 kPa and 400oC
Feldspar
90% – 0.0075mm
3600
85 m3 /min air at 7000 kPa and 20oC
Graphite
90% – 0.01mm
25
2m3 / min air at 7000kPa and 20oC
Mica
95% – 0.075mm
725
20m3 / min air at 7000kPa and 425oC
Stirred media millsDescription
Stirred media mills are usually constructed in the form of a cylindrical drum inside which there are a series of rods, arms or perforated discs which are rotated on a central shaft. The drum is loaded with grinding media, such as metal balls or glass sand. The media and the charge is ‘stirred’ together and thus the grinding takes place.
Stirred media millsCharacteristics
Suited primarily to the very fine grinding of soft materials. Usually used with wet grinding but can be used for dry grinding also. Product size is as small as 0.005mm.
Archives
Recent Posts
Categories
Calendar
Meta
Fluid energy mills, Stirred media mills
Fluid energy mills Description
The general principle of operation in a fluid energy mill is that the mineral to be ground is fed into a grinding chamber in a high speed, high pressure and, often, high temperature jet of air (or other gas). The particles collide violently and this causes comminution to take place. Various designs of fluid energy mill exist, the most common being the microniser. This mill has a shallow circular grinding chamber and a series of peripheral jets set tangentially to a common circle. The turbulence causes bombardment which effects a rapid reduction in particle size. A centrifugal classification system keeps larger particles within the chamber while allowing fine particles to leave. In a well designed fluid energy mill there will be almost no contact between the charge and the mill lining.
Fluid energy mills Characteristics
Suitable for hard or soft materials to be reduces to 0.02mm or less. This method of milling tends to be energy intensive and slow but is suitable where the product is highly sensitive to heat or contamination from grinding media.
Typical jet mill performance
(Kg / hr)
50% – 0.003mm
Stirred media mills Description
Stirred media mills are usually constructed in the form of a cylindrical drum inside which there are a series of rods, arms or perforated discs which are rotated on a central shaft. The drum is loaded with grinding media, such as metal balls or glass sand. The media and the charge is ‘stirred’ together and thus the grinding takes place.
Stirred media mills Characteristics
Suited primarily to the very fine grinding of soft materials. Usually used with wet grinding but can be used for dry grinding also. Product size is as small as 0.005mm.