Gas flow velocity inside the dry ball mill cylinder

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Recently, I worked on a small project to grind quicklime into powder using a φ1.8×7 ball mill in a dry process, for use in brick manufacturing. In dry ball mills encountered in the past, either there was no outlet at the exit end, or an exhaust port was provided for dust removal ； Inside the cylinder, factors such as the scraper plate and the accumulation of material cause the material to move toward the discharge end. Therefore, in the design, a smaller exhaust duct is used at the outlet of the ball mill to create a slight negative pressure and reduce dust. However, during the trial operation, the discharge from the ball mill was poor and it tended to get clogged; increasing the exhaust volume caused more fine powder to be carried into the dust removal system. I think there is a problem with the manufacturer’s equipment, but some people believe it’s an issue with the ventilation speed; they insist that there is nothing wrong with the ball mill and demand that the dust removal system be redesigned to accommodate the increased air volume. In this ball mill, I am obtaining slaked lime powder with a final particle size of 180 mesh. Is a certain directed air flow rate required in a dry ball mill? What is the speed? How is the flow cross-sectional area determined? I’m really confused; I hope someone with more knowledge can give me some advice!