Conversion of waste ship-oil sludge into renewable fuel: Assessment of fuel properties and techno-economic viability of supplementing and substituting commercial fuels

Abstract

Waste ship-oil sludge (WSOS) is considered as a hazardous waste as it affects the aquatic and dependent ecosystems. However, energy-rich fuels can be obtained upon treating this waste instead of discharging into the sea. Pyrolysis of oily wastes yields a higher proportion of energy-rich fuel when compared to solid wastes. This study provides an insight into the production of different products at various stages of thermal decomposition of completely mixed WSOS and compares its fuel properties such as calorific value, acid content, flash point, distillation, etc. with commercial diesel and aviation fuels. Non-combustible phenol-rich liquids were obtained at a temperature of 220 °C–300 °C (stage – 1) and 300 °C–400 °C (stage – 2). The stage – 2 product contained octa atomic sulphur and the concentration of sulphur in the subsequent stages increased consequently. Stage 3 (475 °C–550 °C) and stage 4 (550 °C–650 °C) products were analysed for commercial fuel properties and compared to conventional diesel and aviation fuels as they contained 45.79% and 56.29% of diesel-equivalent (C13 – C18) hydrocarbons respectively. Stage 3 corresponded well with Grade No.1 diesel fuel according to the ASTM D-975-19 standards and exhibited better properties in comparison with the stage 4 product. An inductive method of techno-economic analysis was carried out. The analysis returned a positive net present value (69,142.49), a high internal return rate (53.78%), and a payback period of 13.52 months, indicating that the sale of pyrolyzed WSOS as commercial fuel will be profitable.