Material
Calcium Carbonate
Answer in brief
Calcium carbonate is sold from sand-like grades to submicron powders, and the handling system has to match the grade rather than the chemical name.
Coarse ground material flows and wears; ultrafine and coated grades aerate, bridge and coat every surface they touch.
- Design around the finest grade the plant will ever run.
- Expect flooding after pneumatic transfer of fine grades.
- Treat coated grades separately, since the surface treatment changes flow.
Reviewed October 21, 2026 · Updated October 21, 2026
Handling challenges
Filler lines usually run several calcium carbonate grades through the same equipment, and that is where the trouble starts.
Fineness changes everything
- Coarse ground grades behave like a fine sand: free flowing, abrasive, easy to meter.
- Fine grades hold air, flood valves and then consolidate into a bridging powder.
- Coated grades flow differently again, since the stearate surface reduces friction but increases buildup on walls.
A hopper sized for the coarse grade will arch with the fine one, and a feeder tuned for the fine grade will wear with the coarse one.
Feeding into compounding
Filler loading determines product cost and properties, so dosing accuracy matters commercially.
Loss-in-weight feeding with deaeration and side-feeding into the extruder gives stable addition, while gravity charging of a fine filler produces surging.
Dust
Ultrafine grades escape through small gaps and settle on everything in the building.
Enclosed transfer, contained big bag discharge and extraction at the charge point are more effective than cleaning after the fact.
Wear
Even though the mineral is relatively soft, high velocity conveying of coarse grades erodes bends and valve seats over time.
What to establish before buying equipment
- Full grade list the line must handle, including future products.
- Aerated and settled bulk density for each grade.
- Required feed accuracy at the compounding line.
- Changeover and cleaning requirement between coated and uncoated grades.
Material behavior
- Flowability
- Coarse grades free flowing, fine grades cohesive
- Abrasiveness
- Moderate
- Cohesiveness
- Rises sharply with fineness
- Moisture behavior
- Low moisture uptake; moisture still causes bridging
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