that fan when originally used had a filter on the door of the panel it was in
it used the white filter material rs sells on a roll
didnt seem to hold it back much at all till it was blocked
filter panrl was maybe 2ft square
Filter manufacturers will tell you the pressure required for a given air flow rate. Damp dust can quickly clog a filter. Modern filters will usually have a self-cleaning facility, very old systems may have nothing more than some hanging filter socks that have to be emptied manually (not a particularly pleasant task).
The fan in your photo has a large number of forward-curved blades, on which dust can build up. One with backward-inclined blades would be better for handling dust, and also able to generate much higher pressures (see comment from Parm, post #14). Paddle blade fans are even better at handling a lot of dust, but less efficient (take a lot of power for any given air flow rate).
General design procedure is:
A: Particle size and weight will govern the air speed necessary to capture and transport the dust.
B: Calculate the volume flow required. If possible, use a close-fitting hood around the source of dust, so that you can achieve the required capture speed without shifting vast volumes of air.
C: Select a filter, based on the particle size and the air flow volume. Manufacturer’s data will tell you the pressure drop through the filter for that air flow.
D: Add on the calculated pressure drop through the ductwork.
E: Knowing the the air flow and total pressure, you can select a fan.
