From a permitting standpoint, the material and air flow rate will be need to measured or calculated to determine the dust load ratio. To verify the original design data, measure the power consumption of the air mover, the total system pressure and the air and material flow rates. A time study may have to be performed on the inlet and or outlet discharge vessels to estimate the mass flow rate of the soybean protein.
To get the data in the right format, you may need to convert the actual mixture conditions to the equivalent weight per standard dry cubic foot of air. If you need more help with this conversation, see Industrial Ventilation Design - A Manual of Recommended Practice - 27th Edition Chapter 9.
A few of state environmental agencies provide spreadsheets to help calculate the breakdown for potential PM, PM2.5 and PM10 source emissions for different industrial processes. To provide the most accurate information on the air quality permit, a particle size analysis can be performed by a certified lab to determine this distribution.