Method for operating an agitator bead mill and agitator bead mill therefor
A method for dry operation of an agitator bead mill, with a mill housing that includes a grinding chamber, in which a rotatable agitator shaft extends horizontally between an input side and an output side and in which grinding media are situated. An output gas is fed into the grinding chamber on the output side, goes together with ground grist through the separation system radially with respect to the transport direction, and thus leaves the grinding chamber together with ground grist through the separation system and onward through the product output. Also disclosed is an agitator bead mill for executing the method, such that the separation system has a static sieve with a free perforated surface that is chosen in such a way that the pass-through speed of the gas leaving the agitator mill through the separation system and the product outlet amounts approximately to 10 m/s to 30 m/s.
1. A method for dry operation of an agitator bead mill, with a mill housing that encloses a grinding chamber, in which a rotatable agitator shaft extends horizontally between an input side and an output side and in which grinding media are situated, said method including the steps of:
on the input side, feeding grist that is to be ground into the grinding chamber through a product inlet,
transporting the grist that is to be ground from the input side along the agitator shaft in a transport direction parallel to the axial direction of the agitator shaft to the output side and thereby grinding it by the grinding media,
the ground grist exiting from the grinding chamber on the output side, by going radially with respect to the transport direction through a separation system that detains the grinding media,
the ground grist then leaving the agitator bead mill through a product outlet situated downstream from the separation system, and
feeding an output gas into the grinding chamber on the output side in the area of the separation system and at least partly against the transport direction, said output gas going, together with ground grist, through the separation system radially with respect to the transport direction, and thus said output gas leaving the grinding chamber together with ground grist through the separation system and onward through the product output.
2. The method according to claim 1 , wherein the output gas is directed into the grinding chamber on the output side in the area of the separation system in a direction diverging from the transport direction.
3. The method according to claim 2 , wherein, in addition to the grist that is to be ground, a gas volume stream is introduced into the grinding chamber on the input side of the agitator mill, and said gas volume stream contributes toward transporting the grist that is to be ground, wherein the gas volume stream constitutes only 5% to 20% of the total gas quantity that leaves the agitator mill through the separation system and the product outlet, and wherein the feeding of output gas is chosen in such a way that the load of the entire gas leaving the agitator mill through the separation system and the product outlet with removed grist amounts to approximately 0.3 kg/m 3 to 0.7 kg/m 3 .
4. The method according to claim 1 , wherein, in addition to the grist that is to be ground, a gas volume stream is introduced into the grinding chamber on the input side of the agitator mill, and said gas volume stream contributes toward transporting the grist that is to be ground, wherein the gas volume stream constitutes only 5% to 20%, of the total gas quantity that leaves the agitator mill through the separation system and the product outlet, and wherein the feeding of output gas is chosen in such a way that the load of the entire gas leaving the agitator mill through the separation system and the product outlet with removed grist amounts to approximately 0.3 kg/m 3 to 0.7 kg/m 3 .
5. The method according to claim 4 , wherein the load of the entire gas leaving the agitator mill through the separation system and the product outlet with removed grist amounts to approximately 0.4 kg/m 3 to 0.6 kg/m 3 .
6. The method according to claim 1 , wherein an air classifier is activated in line with the gas-grist mixture leaving the agitator mill through the separation system and the product outlet.
7. The method according to claim 1 , wherein output gas inlet boreholes are disposed and/or aligned in such a way that output gas is directed at an angle between 90° and 180° with respect to the transport direction.
8. An agitator bead mill for executing a method for dry operation of an agitator bead mill, with a mill housing that encloses a grinding chamber, in which a rotatable agitator shaft ex-tends horizontally between an input side and an output side and in which grinding media are situated, such that
on the input side, grist that is to be ground is fed into the grinding chamber through a product inlet,
the grist that is to be ground is transported from the input side along the agitator shaft in a transport direction parallel to the axial direction of the agitator shaft to the output side and thereby is ground by the grinding media,
ground grist exits from the grinding chamber on the output side, by going radially with respect to the transport direction through a separation system that detains the grinding media, and
the ground grist then leaves the agitator bead mill through a product outlet situated downstream from the separation system,
wherein an output gas is fed into the grinding chamber on the output side in the area of the separation system, goes, together with ground grist, through the separation system radially with respect to the transport direction, and thus leaves the grinding chamber together with ground grist through the separation system and onward through the product output,
wherein the separation system has a static sieve with a free perforated surface, which is chosen in such a way that the pass-through speed of the gas leaving the agitator mill through the separation system and the product outlet amounts to 10 m/s to 30 m/s.
9. The agitator bead mill according to claim 8 , wherein on the output side a mill base is present that comprises output gas input boreholes to admit the output gas into the grinding chamber and wherein said output gas input boreholes are covered by a sieve.
10. The agitator bead mill according to claim 9 , wherein the output gas inlet boreholes to admit the output gas into the grinding chamber are disposed and/or aligned in such a way that output gas is directed into the grinding chamber at least partly against the transport direction.
11. The agitator bead mill according to claim 10 , wherein the output gas inlet boreholes are equipped with a common output gas intake pipe through a spiral-shaped output gas distributor housing.
12. The agitator bead mill according to claim 10 , wherein the output gas inlet boreholes are disposed and/or aligned in such a way that output gas is directed at an angle between 90° and 180° with respect to the transport direction.
13. The agitator bead mill according to claim 9 , wherein the output gas inlet boreholes are equipped with a common output gas intake pipe through a spiral-shaped output gas distributor housing.