Exploring pyrolysis and reduction behaviour of high-sulphur petroleum coke for disposal of Zn-containing dust

Abstract

High-sulphur petroleum coke (HSPC), a significant byproduct of petroleum refining, has limited applications except as fuel for combustion. This study aims to expand its utility by investigating its efficacy as a reductant for disposing of Zn-containing dust, thereby substituting traditional coal-based reductants. The pyrolysis results showed that the gases generated from the pyrolysis of HSPC primarily comprised hydrogen gas (H₂), carbon monoxide (CO), methane and carbon dioxide. The reductant gases H₂ and CO accounted for above 90% of the total pyrolysis gas at 1200 °C. The reduction reaction mechanism was elucidated by thermodynamic calculations and carbothermal experiments. At 800 °C, ZnFe₂O₄ is gradually decomposed into Fe₃O₄, FeO and ZnO, and Fe₂O₃ is completely reduced to Fe₃O₄. At 900–1000 °C, iron oxides are basically reduced to Fe, and ZnO is also reduced to Zn. Above 1100 °C, CaMgSiO₄ as a slag phase is generated due to the combination of CaO, MgO and SiO₂. At 1200 °C, the roasting product with a metallic material is obtained, and the sulphur removal rate reaches 58%. This study provides valuable insights into the clean and efficient recovery and reuse of petroleum coke–coal, offering a promising avenue for sustainable resource management.