Be careful with that oxygen idea. The flame will travel faster in an oxygen fuel mix than in an air fuel mix. If it burns into the interior of the burner pipe the volume of the pipe will allow a rather impressive pop. I doubt that the pipe would rupture although I cannot guarantee that it wouldn't. Still hoses blown off, flying parts, flying grit, subsequent fire, burns... all bad.
Relatively cheap medium and high pressure air/propane burners are available in a large range of btu outputs. Perhaps that is the way to go.
Bill