If you break the front derailleur, you can simply remove the broken pieces (or loosen the clamp and twist them round to the non-drive side of the seat tube) and then leave the chain on the chain ring of your choice. It may jump off over very rocky terrain, but should be fine in most situations, as the rear derailleur is designed to keep the chain under tension.
Before you can remove the pieces, you will either have to undo the front derailleur cage or break the chain. This is because the derailleur cage completely encircles the chain. Some derailleur cages have a screw which, once removed, separates the cage pieces. If yours does not, then you will need to follow the instructions on using a chain tool to break and refasten the chain.
You will also have to undo the front shifter cable where it attaches to the derailleur in order to slide the derailleur round, up or off the bike. Secure this cable so that it doesn’t get caught up in anything.
After removing the front derailleur, you can still shift your front gears by lifting the chain from one chain ring to another by hand. Of course, you have to be stationary to do this.