The ASTM A203 Grade D pressure vessel plates are widely used for the construction of methanol scrubber columns, which a key facility in many petrochemical and coal chemical projects. Grade D of ASTM A203/ ASME SA-203 has the nominal composition of 3.5% nickel hence is called “3.5% nickel steel” or “3.5Ni steel”. The UNS number is K31718 with P number of 9B.
In the scrubber column, methanol is designed to absorb sour gases (CO2 & H2S) at low temperature and high pressure. The lower the temperature, the higher efficiency the absorption. Usually the design working temperature is at around -70°C. The 3.5% nickel steel plates have satisfactory impact toughness at -101°C hence is an ideal material. Moreover, according to ASME B31.3, the ASTM A203 Gr.D plate with maximum thickness of 76 mm can be used at temperature -87°C. This provides more flexibility in heavy wall design.