Maximum air flow of an ACM mill means the upper volumetric limit of the induced draft fan (m³/h) for that specific ACM model, when the fan runs at full VFD speed with clean filter bags and minimal system pressure drop. This maximum airflow is the upper operating boundary; production usually runs below this value and adjusts airflow downwards for finer grades.
Typical Maximum Air Flow Range (JACAN / standard industrial ACM)
- Lab / small pilot ACM: max airflow 250–800 m³/h
- Medium industrial ACM (for diatomaceous earth, mineral fillers): max airflow 1200–5500 m³/h
- Large industrial mining/mineral ACM: max airflow 7500–18000 m³/h
Custom oversized ACM systems can reach up to ~22,000 m³/h max airflow for high-volume mineral processing, but these are non-standard specials.
Operational meaning of “maximum airflow”
- Maximum airflow = coarse-grade operating point (e.g., 120 mesh)
At full fan speed, residence time inside grinding chamber is shortest. Less re-circulation, fewer fines, highest throughput. This matches the coarse end of your 120–800 mesh operating window. - When switching to fine grades (800 mesh), airflow must be reduced
To extend particle residence time and create more fines, operators lower fan speed below the maximum airflow setting. Running at full maximum airflow cannot produce the finest product. - System pressure drop reduces actual airflow
The rated max airflow is tested with clean filter media. During continuous operation, dust cake builds on filter bags, raising pressure resistance. The real available airflow will drop, so fan sizing includes a 10–15% margin above the required working air volume.
Material-specific considerations at max airflow
- Low-density porous minerals (diatomaceous earth): can safely run near max airflow, helps preserve frustule structure.
- High-density powders (ruthenium, heavy metals): even at max airflow, duct velocity must stay above 15–25 m/s to prevent powder settling. Sometimes standard ACM max airflow is insufficient for high specific-gravity materials and requires custom fan upgrade.
- Closed inert nitrogen loop (LFP, ruthenium): the volumetric maximum circulation flow follows the same model rating, but gas density and pressure loss are recalculated for nitrogen instead of air.
Relationship with hammer count and fines generation
Running near maximum airflow limits the effect of high hammer count. Even with more hammers installed, particles exit quickly, suppressing excess ultrafine tail. If you want to increase fines production, reduce airflow below the maximum fan capacity.
Important limitation
Do not continuously operate at absolute maximum airflow for long periods. It increases fan power consumption, system abrasion, and can overload the classifier’s coarse particle handling capacity. Maximum airflow is reserved for grade changeover, startup, and coarse-product production.
ACM mill maximum airflow ranges 250 m³/h for small pilot units up to 18000 m³/h for standard large industrial mineral ACM models. Maximum airflow is the fan’s upper limit and is used mainly for coarser powder grades. Finer products require airflow turndown. Actual onsite airflow will be lower than the rated maximum due to filter cake pressure loss. Max airflow works together with hammer configuration and classifier speed to control PSD and fines yield.
