Milling and dust

Dust generated by a mill

For smaller mills, and especially mills like hammer mills that runs at high RPM, dust is one of the biggest problems for a milling enterprise.

It’s not only a health hazard to those working with the machine and in its surrounds, but it wastes a great deal of product and it may be the cause for really serious accidents such as dust explosions.

Dust simply extracted from the premises creates other problems when it gathers on roofs, causing rust and rotting on roofs and  gutters, down pipes and generally soiling the environment. It is also unsustainable when having neighbours in an industrial area.

Dust is generated in many areas of a processing unit, especially with dry products such as at cleaning / separation, conveyance, unloading from trucks, intake dump pits into silos or bins, at intake into a mill, at milling output, at loading pellet mills, at various screening centres, at aspiration centres, at packing areas.

Dust generated by a mill 2

The best way is to start correctly, at design. If already with the problem, it’s best to start where most dust is generated and work you way back to the smaller problem areas.

Much innovative design turned Hippo hammer mills from a massive dust generator since 1928 right through to the past few years when this issue was prioritised by ABC Hansen , into a dustless hammermill through the following measures:

  1. Input control mechanism whereby intake is regulated as airflow is restricted when the screen is filled, thereby not overloading the cyclone and ducting creating more back pressure. This mechanism also serves to limit back-splash to an almost unperceivable level.
  2. Re-design of cyclones for higher efficiency. Custom designed cyclones can be produced for specific products if the standard cyclone is not efficient enough. The correct cyclone design creates no dust at bag-off and actually creates an inverted air flow back into the cyclone from the bag.
  3. Simple mechanical airlock valves without any electric drive at bag-off point – especially suitable where the product flows directly into a conveyor or air pick-up for further processing.
  4. Dust manifolds with sufficient filter bags to avoid back pressure that can be easily cleaned and all dust recovered.

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