Characterization of the products obtained by pyrolysis of oil sludge with steel slag in a continuous pyrolysis-magnetic separation reactor

Abstract

In this study, a strategy of combining oil sludge with steel slag to improve the quality of tar resulting from oil sludge pyrolysis and steel slag recycling is proposed. Oil sludge pyrolysis with the addition of different amounts of steel slag at different temperatures was conducted by employing a continuous pyrolysis-magnetic separation (CPM) process. The characteristics of oil pyrolysis were characterized by thermogravimetric analysis (TG), the compositions of the non-condensable gas and tar were characterized by gas chromatography (GC) and gas chromatography-mass spectrometry (GC–MS). The effect of steel slag on the tar composition and char surface morphology was analysed. The recovered steel slag concentrate was measured by a magnetic separation method. The results indicated that steel slag addition caused the weight loss rate of oil sludge to increase. The yield of tar reached a maximum of 10.63% at 550 °C, and the increase in temperature intensified the secondary thermal cracking of the volatile fraction and decreased the tar yield. The gas composition analysis indicated that steel slag could act as a catalyst in improving the H2 content during the pyrolysis process of oil sludge. The addition of steel slag significantly increased the content of short alkanes and increased the C5 ∼ C10 fraction by improving the decomposition of the C15 ∼ C20 fraction. The recovery of steel slag from the solid pyrolysis products of oil sludge containing steel slag was conducted in a magnetic separator, and the maximum recovery rate could reach 55.03%. It was concluded that the integration of oil sludge pyrolysis with steel slag and the recovery of steel slag from the solid pyrolysis products of oil sludge containing steel slag could be feasible.