It seems this has come before. Search the archives. Just think about the limiting factors. Drying rate would be a function of what the material is, how it is exposed for drying, and the equipment used for drying. Obviously, there will be differences if the material is hygroscopic and doesn't really want to give up water, and if the material is presented in large lumps vs. a lot of very small ones (surface/volume). Then there is the rate of diffusion of water from the internal parts of the solid particles to the surface for evaporation, as a function of temperature. Finally there is the means of drying the stuff. Heat must be applied to vaporize the water. If the diffusion of water to the surface of the particles is limited, then the latent heat taken from the air or other gas used for removing the water vapor wouldn't drop its temperature too much (unless the air rate is low). If the diffusion is rapid, then drying may simply be a function of how fast you move air across it and to what extent you heat the air. Heating could be a problem, too, if the material being dried is heat-sensitive.
Hopefully someone with knowledge coming from experience in this area (I have none) will provide some references for you to study, so you can see what applies to your case. I suspect actual design of a drying unit ought to be left to an expert in the field.
HTH
