(53ac) Understanding the Corrosion Problems in Petrochemical Industries: An Approach

Yogesh Kumar¹, B.K.Muduli¹, Gopalani.L¹

1Indian Oil Corporation Limited, Panipat Naphtha Cracker Panipat-132140, India

kumary3@indianoil.in, mudulibk@indianoil.in,gopalanil@indianoil.in

ABSTRACT

Petrochemical industries units such as naphtha cracker unit (NCU), high-density polyethylene unit (HDPE), linear low density polyethylene unit (LLDPE) operates on elevated temperature, super high pressure, extreme low pressure, highly flammable media and handle catalyst processing, sub-zero cryogenic streams. These plants deal with cracking of higher molecules hydrocarbon like naphtha in mother unit (NCU) and polymerization of ethylene monomers in the presence of organo-metallic catalysts in downstream units (HDPE&LLDPE).

This paper discusses critical corrosion mechanisms in petrochemical industries critical units. The main unit comprises NCU, which is also the mother unit producing ethylene and propylene to downstream units i.e. HDPE & LLDPE. In NCU unit, carburization and creep are the major corrosion mechanism in naphtha cracker furnace which demands judicious maintenance and monitoring management of furnace tubes. Erosion due to coke, caustic embritlement, corrosion due to process water and dilution steam, low temperature brittle failure are some of the other damage mechanism in NCU Unit. Corrosion due to chloride-based catalyst is the main corrosion mechanism in downstream polyethylene units (HDPE&LLDPE) and demands systematic management of material selection. Cooling water under deposit corrosion followed by pitting corrosion of heat exchanger tubes with cooling water on the shell side, are additional corrosion hazards. Corrosion under insulation, for small bore connections and piping in cold service is another important damage mechanism, which needs to be addressed intelligently as a part of mitigating safety hazards. Proper reliability management and developing inspection plan to mitigate it is a challenging task.

Keywords- Creep, Carburization, Pitting, pH, Austenitic stainless steel, naphtha cracker unit (NCU), linear low density polyethylene unit (LLDPE), high-density polyethylene unit (HDPE), CUI, Flow assisted corrosion, HCL corrosion