Oxidative thermal treatment of oil sludge at low heating rates

Oil sludge is one of the major industrial wastes that needs to be treated for the refinery or petrochemical industry. Efforts have been made to convert the oil sludge into available resources such as lower molecular weight organic compounds and carbonaceous residues. In this study, the oil sludge from the oil storage tank of a typical petroleum refinery plant located in northern Taiwan is used as the raw material of thermal treatment using oxygen-containing gas. The treatment of oil sludge is conducted by the use of carrier gas with different concentrations of oxygen (4.83, 8.62, 12.35, and 20.95 vol % O₂) in the temperature range of 380-1123 K and at various constant heating rates of 5.2, 12.8, and 21.8 K/min. The significant reactions occur in the range 415-931 K. Below a temperature of 613 K, pyrolysis reactions are predominant. Including the pyrolysis reactions, the overall oxidative thermal decomposition of oil sludge can be adequately described by a five-parallel-reaction model. The activation energies (E), reaction orders (n for residual solid and m for oxygen) and frequency factors (A) of corresponding five-parallel-reaction model for oil sludge are 69.93, 93.79, 123.22, 208.67, and 120.87 kJ/mol of E, 2.94, 2.42, 1.24, 2.91, and 1.36 of n, 0, 0, 0, 2, and 0.32 of m, and 7.69 × 10₅, 9.09 × 10₆, 2.95 × 10⁸, 1.66 × 10¹⁷, and 9.45 × 10⁷ 1/min of A, respectively. The proposed reaction kinetic equations can provide useful information for the proper design of an oxidative thermal processing system for the treatment of oil sludge. © 2004 American Chemical Society.