Devolatilization of oil sludge in a lab-scale bubbling fluidized bed

Area of Science:

• Chemical Engineering
• Combustion Science
• Fluidized Bed Technology

Background:

• Oil sludge presents a disposal challenge, requiring efficient treatment methods.
• Fluidized bed combustion offers a promising route for energy recovery and waste reduction.

Purpose of the Study:

• To investigate the devolatilization kinetics of oil sludge pellets in a lab-scale bubbling fluidized bed (BFB).
• To evaluate the effects of pellet size, bed temperature, and fluidization velocity on devolatilization.
• To analyze the combustion behavior and ash characteristics of oil sludge pellets.

Main Methods:

• Lab-scale BFB experiments were conducted under nitrogen and air atmospheres.
• Devolatilization times were measured for oil sludge pellets (5-15 mm diameter).
• Combustion experiments focused on pellet behavior, including primary fragmentation.

Main Results:

• Devolatilization time increased linearly with pellet diameter in nitrogen and exponentially in air.
• Primary fragmentation of larger pellets (>10mm) at high temperatures (>700°C) in air significantly reduced devolatilization time.
• Superficial fluidization velocity had no noticeable effect on devolatilization in air.
• Oil sludge ash particles were fragile and easily elutriated from the BFB.

Conclusions:

• Devolatilization of oil sludge pellets is strongly dependent on atmosphere, pellet size, and temperature.
• Primary fragmentation is a key phenomenon in air combustion, accelerating devolatilization.
• The fragile nature of the ash impacts particle entrainment and requires consideration in BFB design for oil sludge treatment.