Effects of reactor configuration on the yield of solid carbon from pyrolysis of low-density polyethylene

The formation of solid carbons by LDPE pyrolysis has been studied in three different reactors: a batch feed reactor with slow heating (BFRSH), a batch feed reactor with fast heating (BFRFH), and a semicontin-uous feed reactor with fast heating (SFRFH). The yield to solid carbons was low in the batch reactors with slow and fast heating (<3%) even when LDPE was copyrolyzed with polystyrene, lignin, and other additives. The yield increased to values between 15 and 52% when a semicontinuous feed reactor with fast heating was employed, which can be attributed to a longer residence time of primary pyrolysis products and higher extents of condensation reactions. Using a quartz reactor in the semicontinuous feed reaction system produced solid carbons with a homogeneous morphology of monodisperse spherules in high yields (15-43%) at temperatures of 750 and 850°C. A Hastelloy reactor used in the same configuration produced higher yields of solid carbons (33-52%) because of wall catalysis, but the solid carbons obtained included metal alloy particles.