Combustion of tyre pyrolysis oil

Scrap tyres were pyrolysed in a one tonne batch pyrolysis unit to produce an oil, char, gas and steel product. The derived oil was analysed for fuel properties, including calorific value, elemental analysis, sulphur; nitrogen, chloride and fluoride content. In addition, a single oil droplet combustion study was carried out and the oil was also analysed in detail for its content of polycyclic aromatic hydrocarbons (PAH). Comparison of the tyre oil fuel properties with those of petroleum-derived fuels was made. The oil was combusted in an 18.3 kW ceramic-lined, oil-fired, spray burner furnace, 1.6 m in length x 0.5 m internal diameter. The emissions of NOx, SO2, particulate and total unburned hydrocarbons were determined in relation to excess oxygen levels. In addition, the solvent organic fraction of the soot was extracted and analysed for PAH concentration and compared with the PAH content of the original fuel. Throughout the combustion tests, comparison of the emissions was made with the combustion of diesel fuel as a representative of a petroleum-derived fuel with similar properties. The oils were found to contain 1.4 wt% sulphur and 0.45 wt% nitrogen and have similar fuel properties to those of diesel fuel/light fuel oil. Total PAH in the tyre oil were 9.2 wt% compared to diesel fuel which contained 3.1 wt%. Combustion of the tyre pyrolysis oil in the furnace showed that emissions of NOx and SO2 were higher than when diesel fuel was used, which was attributed to the higher nitrogen and sulphur contents in the tyre oil. Particulate and total unburned hydrocarbon emissions were negligible and PAH were not detected in the normal operating mode of the furnace.