If they are brazed on.

Propane isn't hot enough, by the time you have melted the braze you will have distempered a section of the tube.

Use Map gas and a small nozzle. Wrap a wet rag around the tube and direct just beyond the very tip of the flame at the part you want to remove at a spot farthest from the frame. Do not grab the part with pliers, they will act as a heat sink, rather tap at it with a screwdriver to break it free.