Co-pyrolysis Of Heavy Oil And Polyethylene In Supercritical Water

At the temperature of693K and water densities from0.10to0.30g/cm3, the phase structure of the mixture of heavy oil and supercritical water (SCW) as well as the co-pyrolysis of heavy oil and low density polyethylene (LDPE) in the presence of dense SCW was experimentally investigated. With the aid of vigorous stirring, the phase structure of heavy oil/SCW may evolve between an oil/water two-phase structure and an oil-in-water emulsion structure, resulting in drastic differences in fraction distribution and mass transfer environment. In the oil/water two-phase structure, an increase in water density promotes the aggregation and condensation of asphaltenes in the oil phase due to the extraction of light fractions into the water phase. In the oil-in-water emulsion structure, the heavy aromatic radicals resulted from the decomposition of asphaltenes can be transferred rapidly from oil droplets into the continuous water phase. By introducing LDPE into the pyrolysis of heavy in dense SCW, effective coupling between the pyrolysis networks of heavy oil and LDPE can be obtained. The co-pyrolysis of heavy oil and LDPE, which is closely related to the loading of LDPE and the reaction progress, is run with the combination of the solid/liquid two-phase structure and emulsion structure. At the early and middle co-pyrolysis stages, heavy aromatic radicals released from oil droplets into the water phase can be saturated by the H-abstraction with the homolysis product of LDPE, by which the production of coke-inducing components through dealkylation is avoided. At the later co-pyrolysis stage, the radicals species involved in condensation to coke can also be promptly capped in the same way. In the presence of dense SCW and under vigorous stirring, a significantly reduced coke production together with an increased yield of aromatics therefore can be observed in the co-pyrolysis of heavy oil and LDPE.