The corrosivity of weak and intermediate strength sulfuric acid is strongly affected by concentration, temperature, presence of impurities, and even fluid velocities. 14% sulfuric acid is a reducing acid (in the absence of oxidizing impurities) and attacks metals with the evolution of hydrogen as the cathodic reaction. Conflicting corrosion data for sulfuric acid at this concentration and temperature (probably due to impurities) complicates alloy selection. The workhorse austenitic alloy for this sulfuric acid concentration is Alloy 20Cb-3 (N08020). Other possibilities might include nickel rich alloys like Alloy C-276 (N10276) or Alloy 31 (N08031). For additional information I suggest you obtain one of the many excellent references devoted to sulfuric acid materials of construction such as "Materials Selector for Hazardous Chemicals, Vol. 1: Sulfuric Acid, 2nd Edition" published by MTI.

I confess I don't know what you mean by "burner tube." This sounds like it could be hotter than 140 deg F! There really isn't an austenitic stainless steel to recommend for this acid concentration and temperature...