Particle Size Reduction of SLS Needles in the Hanningfield Uni-Mill?

Objective

The objective of the trial was to reduce the particle size of the given SLS needles using a grater screen and square arm impeller to achieve granules of SLS. As per the client, with the current set of milling parameters, there is a complete choking of the grater screen because of material accumulation which doesn’t provide any milling action

Materials: SLS needles

Infeed particle size: Max 20mm length (As provided by the client) The following figure shows the material as received.

Equipment

Procedure

• The material was dispensed in plastic bag.
• Machine was turned ON and RPM was set.
• Material was manually feed through hopper.
• The milled product was collected in plastic bag from outlet.
• The discharged material was sieved through 40# and weighed to check the % of particles retaining on 40#.

• Milling was carried out smoothly under choked feeding conditions and the milled sample was collected in a drum.
• There was no choking or accumulation of material found on the rasp of the grater screen, indicating its suitability for the application. (fig. 3)
• A minimal amount of dead volume which was found to be constant for any amount of feed material added to the chamber, was noted. This quantity does not indicate retention; however, it indicates dead volume and contributes to minimal losses when large amounts of material is milled.

Equipment

• The material was dispensed in plastic bag.
• Machine was turned ON and RPM was set.
• Material was manually feed through hopper.
• The milled product was collected in plastic bag from outlet.
• The discharged material was sieved through 40# and weighed to check the % of particles retaining on 40#

• Milling was carried out smoothly under choked feeding conditions and the milled sample was collected in a drum.
• There was no choking or accumulation of material found on the rasp of the grater screen, indicating its suitability for the application.
• A minimal amount of dead volume which was found to be constant for any amount of feed material added to the chamber, was noted. This quantity does not indicate retention; however, it indicates dead volume and contributes to minimal losses when large amounts of material is milled.

Conclusion

From the trials taken on the two equipment, it can be concluded that the screen 62G can be used to mill the SLS needles without any choking to obtain granules.