The blending of materials prior to drying can change the dynamics of your drying task. Consider these elements:
Virgin material, blended with a high percentage of regrind (which is typically much lighter than virgin material) decreases the combined bulk density of the material to be dried. In some cases, this may require a larger drying hopper in order to provide enough residence time for the drying process.
Materials mixed by dry blending (not compounded) may separate during transfer from the blending device to the drying hopper, resulting in uneven drying and worse, uneven or error-filled processing, IE: off color parts or parts lacking the characteristics to be created by the additive.
You should not mix or blend materials with very different drying requirements. You should dry those materials separately before blending and processing.