Please clarify what you are trying to heat? Natural gas?
If so why and to what temp? There are heaters available (called vapourisers) to heat LPG liquid producing a warm vapour to prevent it reliquifying in the lines to say other gas burners. Rod Nissen.
Combustion & Engineering Diagnostics
nissenr@iprimus.com.au
sounds to me you could use a small radiant tube burner look at eclipse combustion or north americam manufacturing web page i am sure they would be happy to help