Drainage separator, compressed air dehumidification system and powder transfer method

Provided is a drainage separator that can perform the dehumidification necessary to transport a powder without using an air drier. In an outer container provided with an air inlet at a lower-side wall, a drainage discharge port at a bottom part and an air outlet at a top part, two sheets of a metal porous body are disposed parallel to one another with a predetermined distance therebetween so as to provide a barrier between the air inlet and the drainage discharge port, the space between the two sheets of the metal porous body is filled with a non-water-absorptive spherical material, compressed air introduced from the air inlet is caused to pass through the gaps between the spherical material, and as a result, the drainage contained in the compressed air is discharged.