Effect of Pyrolysis Temperature and Atmosphere on the Pyrolysis Characteristics of Cold-Rolled Oily Sludge with a High Oil Content

An innovative pyrolysis strategy has been proposed for oil sludge in which the flue gas with a low oxygen content from the cement kiln tail is used as the protective atmosphere. However, the impact of cement kiln flue gas on the pyrolysis of oil sludge remains unclear and needs intensive study. Taking the cold-rolled oily sludge with a high oil content as the object, the effects of pyrolysis temperature (400-600 °C) and atmospheres (N₂, CO₂, 64% N₂/36%CO₂, and 64%N₂/30%CO₂/6%O₂) on the pyrolysis behaviors were investigated. GC, GC-MS, and SARA analyses were adopted to evaluate gas composition and oil properties besides the pyrolysis product yields. Under N₂ atmosphere, as the pyrolysis temperature increases within the scope involved, the yield of pyrolysis gas gradually increases, while the yield of pyrolysis oil increases first and then decreases. When the pyrolysis temperature ranges from 500 to 550 °C, the pyrolysis oil yield exceeds 60% and the oil recovery rate reaches over 85%. The yield and quality of pyrolysis products achieve the optimal balance at 550 °C. Among the four atmospheres, the CO₂ atmosphere results in the lowest yield of pyrolysis oil and the highest yield of pyrolysis gas. The simulated atmosphere of 64% N₂/30% CO₂/6% O₂ witnesses the maximum release amounts of H₂ and CO during the pyrolysis process. Preliminary results indicate that it is feasible to utilize the flue gas from the cement kiln tail for the direct pyrolysis of oily sludge.