Co-pyrolysis of soybean soapstock with iron slag/aluminum scrap, and characterization and analysis of their products

[Display omitted] Soybean soapstock (SS) is one of the main solid wastes produced in the refinery of edible oil processing. In this study, the co-pyrolysis of SS with iron slag (IS) and aluminum scrap (AS) was carried out in a tubular furnace. The gas, liquid and solid products were characterized and the char yield decreased with increasing IS/AS ratio. IS and AS can improve the gas yield, and when the ratio of SS/IS was 1:0.25, the total pyrolysis gas and hydrogen contents were significantly increased. The content of oxygen compounds in pyrolysis oil decreased during co-pyrolysis, while AS promoted the content of polycyclic aromatic hydrocarbons in pyrolysis oil. The co-pyrolysis reaction can be divided into four stages, the mass loss rate reaches the maximum at the third stage (390–575 °C). The molar ratio of H/C was lower for pyrolysis, indicating good stability of pyrolysis char owing to the high degree of carbonization and aromaticity. The possible co-pyrolysis reaction mechanism was explored.