Should be two set screws in each pulley. Two pulleys in the pic. Small double and large double. You’ll have to get the small one off first. Little plumbers torch heats too slow to help. Those are cast iron pulleys. Takes a lot of heat to get them hot, and it has to be heated quickly or the shaft heats up too and your still in the same place. Once heated, you have a very short window of time (couple minutes max) to try to get it to move. Then it all has to be allowed to cool before trying again. Cast heats slow and cools faster than hard steel. You will have to use an oxy-acetylene torch.
Is this a keyed shaft? Or a “D” shaft? Or just round with set screws?
Also note, that big cast pulley will break easier than you think, especially once it’s been heated. You don’t want to buy another one.