The pulley usually have a setscrew through the side of the pulley. This is a Allen setscrew which tightens against the key & shaft.
I have seen some they use 2 set screws, one on top of the other. One set screw would have to come out & the one under it-loosen to remove the pulley.
Use a soft block or wood, soft face hammer or something that won't damage the pulley to bump it off.
They usually will come right off, if they are not damaged or rusted up, if the screw or screws are out or loosen.