The place I get my propane tanks filled had old tanks setting around. I asked about getting one to cut up. They said sure and even pulled the valve for me. Didn't even charge me for it.
Once home I flushed it with the water hose a couple times then set it up side down to drain. Propane is heavier than air so it drains out.
After a few days I cut it off with the cutoff wheels I use on my 4.5 inch angle grinder. One of the best tools I ever bought.
I had the propane burner I got years ago for family cook outs to fry fish, cook corn on the cob and such stuff.
Part of what I cut of the top I plan on getting welded around the bottom so it has a larger foot print to be more stable on the burner.
Need to finish that up I guess.
Leo