Nitrogen+Syngas 386 Nov-Dec 2023
30 November 2023
Problem No. 70: Corrosion at unexpected locations like in dry CO₂ pipelines
It is common knowledge that wet CO₂ is corrosive to carbon steel and “dry” CO₂ is not corrosive to carbon steel. So typically engineers and contractors choose carbon steel for dry CO₂ conditions and stainless steels for wet CO₂ conditions. This can be seen in the CO₂ feed section of almost every older urea plant. But is it true that carbon steel is always the right choice for dry CO₂ and is dry CO₂ really dry under all circumstances?
Le Hoang Viet of PetroVietnam Ca Mau Fertilizer in Vietnam kicks off this round table discussion: CO2 and NH3 are raw chemicals that react to produce urea. CO2 is compressed using a CO2 compressor. As per the design, carbon steel is used as the material of construction for pipelines that contain hot CO2 in the discharge of each stage of the compressor. Conversely, stainless steel, usually 304L, is employed for pipelines containing cooled CO2 downstream of the interstage coolers.
