Standard Accounting Mechanics for Recycled Polymer Traceability
Recycled polymer traceability relies on strict mass balance boundaries, physical yield reconciliations, and verified custody transfers across conversion steps.
Pyrolysis Oil Yields
Meaning
Mass balance metrics measure the mass proportion of liquid hydrocarbon condensate recovered relative to total plastic waste feed during thermal cracking. In chemical recycling plants, pyrolysis oil yields reflect the conversion efficiency of mixed polyolefin waste into liquid feedstocks suitable for steam crackers. Thermal depolymerisation breaks long polymer chains at high temperatures in the absence of oxygen, generating condensable liquids and non-condensable gases.
Reactor design and temperature profiles directly dictate the split between condensed liquids and non-condensable synthetic gases. The yield figure applies strictly to liquid fractions condensed under standard recovery conditions and excludes solid char residue.
Reaction Yield
Operating temperatures between four hundred and five hundred degrees Celsius maximize liquid condensate recovery from polyolefin feedstocks. During mixed plastic processing, pyrolysis oil yields decrease when high proportions of polyethylene terephthalate or polyvinyl chloride generate solid carbonaceous char and halogen acid gases. Optimizing residence time in fluidised bed reactors maximizes liquid output while minimizing light gas formation.
Contaminant Influence
Inorganic fillers and heavy flame retardants in post-consumer plastic waste alter thermal decomposition pathways. Elevated filler levels reduce overall pyrolysis oil yields by increasing char formation and trapping liquid hydrocarbons within ash beds. Pre-treatment steps remove non-polymeric materials to maintain stable liquid conversion efficiency.
Product Boundary
Condensed liquid fractions undergo hydrotreating and fractionation to remove residual olefins and heteroatoms prior to steam cracking. Heavier wax cuts require secondary catalytic cracking to convert high molecular weight fractions into liquid naphtha substitutes. The economic viability of chemical recycling relies on maintaining liquid yield proportions above target operational thresholds.