Supercritical water gasification mechanism of polymer-containing oily sludge

In the offshore petroleum industry, polymer-containing oily sludge (PCOS) hinders oil extraction and causes tremendous hazards to the marine ecological environment. In this paper, an effective pretreatment method is proposed to break the adhesive structure of PCOS, and the experiments of supercritical water gasification are carried out under the influencing factors including residence time (5-30 min) and temperature (400-750 degrees C) in batch reactors. The increase of time and temperature all show great promoting effects on gas production. Polycyclic aromatic hydrocarbons, including naphthalene and phenanthrene, are considered as the main obstacles for a complete gasification. Carbon gasification efficiency (CE) reaches maximum of 95.82% at 750 degrees C, 23 MPa for 30 min, while naphthalene makes up 70% of the organic compounds in residual liquid products. The highest hydrogen yield of 19.79 (mol H-2/kg of PCOS) is observed in 750 degrees C for 25 min. A simplified reaction pathway is presented to describe the gaseous products (H-2, CO, CO2, CH4). Two intermediates are defined for describing the reaction process bases on the exhaustive study on organic matters in residual liquid products. The results show that the calculated data and the experimental data have a high degree of fit and tar formation reaction is finished within 10 min. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study proposes an effective pretreatment method for PCOS and demonstrates that both time and temperature have promoting effects on gas production. Polycyclic aromatic hydrocarbons are considered as significant obstacles during gasification. The results show that high carbon gasification efficiency and maximum hydrogen yield can be achieved under specific conditions.