Hazardous elements flow during pyrolysis of oily sludge.

Area of Science:

• Environmental Science
• Chemical Engineering
• Waste Management

Background:

• Oily sludge (OS) is a hazardous waste requiring effective disposal.
• Pyrolysis offers simultaneous energy recovery and waste reduction.
• Hazardous element distribution in pyrolytic products can cause secondary pollution.

Purpose of the Study:

• To systematically investigate the flow of hazardous elements (N/S/Cl, heavy metals) during OS pyrolysis.
• To analyze the impact of varying pyrolysis temperatures on element distribution.
• To identify specific hazardous compounds and pollutants formed.

Main Methods:

• Conducting pyrolysis experiments on oily sludge at different temperatures.
• Analyzing the elemental composition of solid residues, pyrolytic oil, and gas.
• Identifying and quantifying specific N/S/Cl-containing compounds and gaseous pollutants.

Main Results:

• Nitrogen, sulfur, and chlorine predominantly remained in solid residues (44.77-15.51 wt%, 83.29-80.22 wt%, 78.59-73.41 wt%, respectively).
• Increased pyrolysis temperature shifted more N/S/Cl into pyrolytic oil and gas.
• Micromolecular pollutants like HCN, NH3, H2S, and HCl were released between 200-400°C, with others like SO2 and NOx released at higher temperatures.
• Solid residues retained over 60.0 wt% of total heavy metals.

Conclusions:

• Pyrolysis temperature significantly influences the partitioning of hazardous elements from oily sludge.
• Understanding the fate of N/S/Cl and heavy metals is crucial for mitigating secondary pollution.
• Solid residues from OS pyrolysis require careful handling due to concentrated heavy metals.