Sulfuric acid plant materials of construction

This section provides an overview of typical acid plant materials of construction for key equipment items (after Louie, 2008 and DuPont, 2012). 

Acid plant process gas ducting is often constructed of metallized carbon steel where temperatures exceed 400 °C. Metallizing refers to the thermal spray application of a thin (0.25-0.31 mm) layer of aluminum to the inside surface of the carbon steel duct. The aluminum prevents the oxidation of the carbon steel which would cause it to corrode at an accelerated rate if it were not protected. 

Modern catalytic converters are constructed of 304H stainless steel where the H designation indicates high carbon concentration. Table 30.1 shows the differences in carbon concentration for three common 304 stainless steel grades. 

Acid plant catalytic converters, gas heat exchangers, and ductwork should never be constructed of 304L grade stainless steel due to its comparatively low allowable stress at elevated temperature. 

Scale formation and release from the surface of 304H stainless steel can plug catalyst beds. This is common where the converter is exposed to high temperatures and the acid plant has frequent shutdowns or temperature swings (Friedman and Friedman, 2007). 

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