Can a hopper take away the fuel from furnaces?
I am working on an item sorter that sorts tools and bows and I realized that the only difference between them is that bows can be used as furnace fuel (yes I know wooden tools can be used as a fuel too). Can I take the fuel away from the furnace automatically?
No. It's one of these things you can only sort "destructively". Only smelted items can be pulled out of furnaces.
They have 2 inputs (fuel and item(s) to be smelted) and one output (the item that has been smelted).