Study on pyrolysis characteristics of tank oil sludge and pyrolysis char combustion

Abstract

Integrated thermal treatment of OS is a promising method for massive and effective treatment of the waste. The present work investigated the tank OS pyrolysis by a thermogravimetric analyzer and a tube furnace reactor. Pyrolysis char combustion performance was studied with the thermogravimetric analyzer. Results showed that OS pyrolysis mainly occurred between 200°C and 700°C. With the increase of pyrolysis temperature, char yield decreased while gas yield increased. When pyrolysis temperature exceeded 600°C, the oil yield decreased. Simulated distillation showed that oil products properties barely changed when pyrolysis temperature exceeded 600°C. Light fractions (gasoline and diesel) from OS pyrolysis were more than 28% higher than those of oil from OS extraction. Major components of pyrolysis gas include H2, CO, CO2, and hydrocarbons (CHS). CHS content was more than 40% in the pyrolysis gas in all cases. The molar H/C ratio and O/C ratio were lower for OS chars from higher temperature pyrolysis. The surface of OS char was rough with a well-developed pore structure formed during pyrolysis, which was conducive to the combustion reaction. The combustion characteristic of OS char from higher temperature pyrolysis was poorer than that of OS char from lower pyrolysis temperature, resulting from the less volatile content and more carbon crystal degree for OS char from higher temperature pyrolysis. With well-developed pore structure, relative simple composition, good ignition and burnout characteristics, OS char could perform well in actual combustion in CFB boilers.