Oh it burns, burns, burns - The Ring of Fire, The Ring of Fire!
Setting fire to your workbench is a rite of passage. I remember grinding on something that I'd doused with plusgas to get it off the donor. Imagine my surprise when it suddenly caught fire on the workbench.
I'd use a cutting wheel first to get rid of as much of the back of the hub in one lump. Then use a corse flap wheel or something to get the back flat.