Effect of the Pressure and Feedstock State on the Yield and Properties of Waste Tire Thermolysis Products

Scrap tires of passenger cars have been depolymerized by applying a thermal destruction method, thermolysis. The process was conducted in a semi-continuous distillation reactor. The investigation was made on the effect of the pressure and feedstock chopping degree variation on the yield of thermolysis products, oil, char, and gas, as well as their properties and composition. The maximum yield of the liquid product was obtained under 40 bar thermolysis pressure when the feedstock was prepared as a type 2 fraction. Liquid products were analyzed by gas chromatography/mass spectrometry (GC/MS) and standard fuel analysis methods. The chromatographic results show a complex mixture of organic compounds with a considerable amount of arenes (34–41%, w/w). A high calorific value (41.5–42.6 MJ/kg) of the thermolysis liquid is consistent with its chemical composition, which is close to the petroleum-derived products. Sulfur and ash contents in the liquid product are 0.50–0.74 and 0.02–0.07% (w/w), respectively. The tire thermolysis gaseous product is composed of the lightest alkanes (over 55%, v/v), hydrogen (8.60–15.82%, v/v), carbon oxides (over 5.5%, v/v), and butenes (about 4%, v/v) as the main alkenes. The elemental analysis of residual char shows carbon as the main element; however, a significant share (about 11%, w/w) is taken by inorganic impurities. The thermolysis char average calorific value is −31 MJ/kg.