Co-pyrolysis of oil-based drill cuttings and pinewood sawdust: Thermal behavior, synergistic effect, artificial neural network and empirical reaction model

Evaluation of pyrolysis characteristics is essential to convert the waste into various high-value products. In this study, the co-pyrolysis of oil-based drill cuttings (OBDC) and pinewood sawdust (PS) was conducted to analyze the thermal behavior, synergistic effect, and reaction mechanism. Results showed that co-pyrolysis of OBDC and PS had a positive synergistic effect, and the more the percentage of PS in the blend, the stronger the synergistic effect. The pyrolysis characteristic index D increased from 6.50 × 10-05 to 47.38 × 10-05. The apparent activation energy during the co-pyrolysis of OBDC and PS (mass ratio in 1:1) was evaluated using two model-free methods (FWO and KAS) which were 101.38 kJ/mol and 97.51 kJ/mol, respectively. The pre-exponential factors analysis found that the solid phase surface reaction occurred in the co-pyrolysis at the conversion rate of 0.05–0.35; and the co-pyrolysis underwent a complex reaction at the conversion rate above 0.35. The artificial neural network (ANN) with Logsig-Tansig transfer function and neurons number 11 × 12 × 1 had the best prediction effect on co-pyrolysis. The reaction mechanism function (f(α)) of the co-pyrolysis of OBDC and PS was (1 − α)6.2778α2.3848[−ln(1 − α)]0.3570, indicating that co-pyrolysis was the combined effects of reaction order, accelerating, and nuclei growth and diffusion mechanism.