Failure Analysis of Ethanol Vaporizer Heat Exchanger Tubes

A series of tube failures due to corrosion occurred in shell-and-tube heat exchangers that utilized high-temperature steam within horizontal tubes to distill ethanol within the shell. On the basis of the investigation, it was determined that the tubes were made of 316L stainless steel, and the ethanol (and tube corrosion product) had elevated sulfur content. The corrosion of the tubes was predominantly located in the areas of high sulfur concentration along the surfaces with the highest temperature where sulfuric surface deposits were allowed to form. Alternative tube materials which may offer improved corrosion resistance were recommended.