My first question is can your mineral be wet ground?

Is it sulphur?, can you provide adequate grounding for the amount of static electricity being generated? if not why not.

Can an electricity collector ring be mounted on your grinders rotor shaft to bleed away the static electricity to an adequate grounding source?

A collector ring is used to deliver electricity to a piece of underground mobile mining machinery utilizing carbon brushes to deliver the electricity and it could be used in reverse to carry away static electricity.

If not consider Using Carbon Dioxide instead as it is readily available and less costly than dry nitrogen.

contact Irish Carbonic in Buffalo NY as they are a bulk supplier of CO2. ■

Ask your grinder supplier about installing a collector ring to the rotor of the grinder as this should solve the problem as it will follw th epath of least resistance-remember static electricity is lazy just like water- when I worked as a mechanic in a salt mine I had to deal with static electric charges a lot due to the mobile machineries running on rubber tires and not having a continuos ground from a chain being dragged on the ground by the machinery. ■

The material needs a bit more definition. Dry bone ground?

Bone is not mineral.

CO2 would be an acceptable inerting medium.

You other problem is the associated health risk.

Purge gas pressure needs to be just above the chamber operating pressure, any higher & you will have flowrate to consider. Flowrate target is ideally zero after balancing the influences of exigent material & rotating elements against the gas buoyancy. If your dust goes up, like a cement mill, then the gas is heavier than air etc etc.

The net size of the comminuting cavity will also determine the set point of the pressure regulating valve. BOC, Linde or Air Products all publish comprehensive literature. ■

As john stated previously CO2 is acceptable as a suppression gas

CO@ is heavier than air and will flood and saturate the grinding chamber. As John has said the flooding pressure has to be greater than the chamber pressure, the one thing you have not mentione is whether this is batch grinding as is done with cement ores in a ball or rod mill or continous grinding with compression/shearing

you can contact Linde gasses in Canada or like I said before Irish Carbonic in Buffalo or Linde or air products or BOC gasses as john Gately has so kindly suggested in his posting reply to you.

Be sure to ask the grinder manufacturer about attaching a collector ring to the rotor of the grinder to carry away static electricity as the rotor will generate a considerable static charge. ■