This is the exact control of a typical waste fuel boiler, nothing other than conveyor control is necessary. Steam pressure is controlled by the conveyor speed. Unless someone is standing on the conveyor with a fire hose, the moisture content should vary day to day, but not minute-to-minute.
What you may find is that is is difficult to control the flame at ...
IMHO, you don't really need AI. PID (or even PI) would be sufficient in this problem. Arguably, you might need to add a cascade controllers (or two), but it should be sufficient.
Although AI is powerful, it still needs a lot of tailoring (probably training of the model), and at the end of the day you end up with a black box that could be difficult to debug.