Used Lubricating Oil Processing for Energy Recovery. I. Applied pyrolysis

Applied pyrolysis is used in this work as a treatment technique for hydrocarbon fraction recovery of used lubricating oils (ULO) with the aim of its further energetic valorisation. Applied pyrolysis bring also the advantage of a better management of metallic compounds that will be concentrated in the solid residue. In this work, technical parameters have been evaluated to establish their influence on the process evolution with the aim of identifying the adequate parameters for obtaining the maximum liquid fraction. It was found that, for an equilibrated energy balance, the final pyrolysis temperature should not exceed 460 C and the main parameter that affect the pyrolysis oil yield and its physical-chemical properties is the heating rate in the thermal range of decomposition. Activated Zeolites (HZSM-5 type) and Na2CO3 were used as catalysts. The catalysed pyrolysis tests were performed using direct contact between ULO and catalyst, the materials being mixed before processing. Experimental results showed that in non-catalysed pyrolysis an increasing heating rate is slightly reducing the yield of liquid fraction. On the other hand, by using catalysts, the liquid fraction is decreasing. Thus, the highest liquid ratio (81 wt.%) was obtained when the Na2CO3 is used and the process is run under a heating rate of 3-5 C/min. But then, the zeolite HZSM-5 is leading to the highest overall conversion, 95 wt.% at 15-17 C/min, and is positively influence the formation of gas fractions.