Major Products Obtained from the Pyrolysis of Oil Sludge

Oil sludge, if unused, is one of the major industrial wastes that needs to be treated for the refinery or petrochemical industry. It contains a large portion of combustible components with high heating values. Obviously, the conversion of oil sludge to various useful materials such as lower molecular weight organic compounds and carbonaceous residue via pyrolysis not only solves the disposal problem but also matches the appeal of resource utilization. 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 pyrolysis. Its heating value of dry basis and low heating value of wet basis are about 10681 and 5870 kcal/kg, respectively. The pyrolysis of oil sludge is conducted by using nitrogen as carrier gas in the temperature range 378−873 K. The pyrolytic reaction is complex and significant in the range 450−800 K. The residues of pyrolysis of oil sludge exhibit very high viscous form below 623 K (pyrolysis temperature), while low viscous or solid form above 713 K. The major gaseous products (noncondensable gases at 298 K) excluding N2 are CO2 (50.88 wt %), HCs (hydrocarbons, 25.23 wt %), H2O (17.78 wt %), and CO (6.11 wt %). The HCs mainly consist of low molecular weight paraffins and olefins (C1−C2, 51.61 wt % of HCs). The temperature corresponding to the maximum production rate of HCs is 713 K. The distillation characteristics of liquid product (condensate of gas at 298 K) from the pyrolysis of oil sludge is close to diesel oil. However, it contains a significant amount of vacuum residue of about 9.57 wt %. The heating value of liquid product is about 10840 kcal/kg. All this information is useful not only to the proper design of a pyrolysis system but also to the better utilization of liquid oil product and understanding of gaseous emission.