Integrated Thermochemical Conversion of Plastics to Circular Refinery Feedstocks: A System-Level Analysis

Plastics pyrolysis is increasingly pursued as a pathway for producing circular hydrocarbon feedstocks for petrochemical integration. However, non-integrated reactor configurations often exhibit limited heat-transfer control, significant char-handling requirements, and variable product distributions. This work presents a system-level interpretation of the MLM-R™ process, an integrated pyrolysis–combustion loop in which a circulating solid heat carrier enables continuous thermal supply through internal oxidation of carbonaceous residues. Material Flow Analysis (MFA) was applied to reconcile mass, elemental carbon, and chemical energy distributions across the defined process boundary. For the representative case study (1000 kg polyolefin basis), ~81% of feed carbon and ~83% of feed chemical energy (HHV basis) were recovered in the condensed liquid product, while ~7% of feed carbon was internally combusted to sustain autothermal operation. Simulated distillation analysis indicates that removal—aimed at further reprocessing—of a ~15 wt% C34+ heavy fraction from the pyrolysis vapor stream enables compliance with refinery-relevant boiling range targets (≥95% below 480 °C). The MFA results, supported by the physicochemical interpretation, suggest that integrated control of solids circulation and heat transfer contributes to product selectivity and process scalability in circular feedstock production.