Meaning
Chemical degradation of the metallic surfaces within the cooling systems of steam cracking or pyrolysis units. In the production of circular monomers from plastic waste, quench tower corrosion occurs when acidic compounds from chlorinated or fluorinated polymer contaminants dissolve in the wash water. This chemical attack shortens the operational lifespan of the processing equipment and increases maintenance costs.
Corrosion Mechanism
High temperatures during pyrolysis break down residual polymers, releasing volatile acids that travel with the product stream into the cooling section. As these gases cool and condense, the acids concentrate in the aqueous phase and corrode the carbon steel or alloy piping. Monitoring the pH of the quench water provides early warning of acid accumulation, allowing operators to introduce neutralizing agents before significant damage occurs.
Operational Mitigation
Operators utilize chemical inhibitors, alloy upgrades, and intensive water treatment protocols to manage this degradation. These interventions are critical when processing pyrolysis oil derived from mixed post-consumer plastic waste, which typically has higher contaminant levels than fossil feedstocks. Proper mitigation strategies prevent unscheduled shutdowns and maintain the continuous operation of the monomer recovery process.
Financial Impact
Neglecting water chemistry in the cooling loop leads to rapid metal loss, structural failures, and leaks. Replacing damaged vessel sections or heat exchangers requires long plant shutdowns, resulting in substantial production losses and high repair bills. Managing this risk is essential for the economic viability of chemical recycling plants processing mixed plastic waste.
