Disposal, regeneration and pyrolysis products characterization of spent bleaching clay from vegetable oil refinery in a fluidized bed pyrolyser

Spent bleaching clay (SBC) is a by-product of edible oils refinery and inappropriate treatment has caused serious environmental pollution in the past decades. In this study, fluidized bed pyrolyser (FBP) was employed for oil recovery and regeneration of SBC. The oil recovery ratio (ORR) ranged from 24.8 to 60.2% at pyrolysis temperature of 400-700 degrees C, and reached the maximum at 600 degrees C. Pyrolysis oils (POs) were composed of carboxylic acids, alkanes, esters, aromatics, alkenes, alkynes and other oxygenated hydrocarbons, and the content of hydrocarbon compounds reached 73.9% in pyrolysis oil obtained at the pyrolysis temperature of 600 degrees C (PO600), which exhibited the potential for upgradation into green fuels and chemicals. The methylene blue (MB) adsorption value of pyrolysis char produced at pyrolysis temperature of 600 degrees C (PC600) reached maximum of 213.6 mg/g. While the decolorization ability of pyrolysis chars (PCs) increased with pyrolysis temperature, and pyrolysis char obtained at the pyrolysis temperature of 700 C (PC700) reached maximum (i.e. 96.3%), close to that of virgin bleaching clay (VBC). FBP technology effectively improved the decolorization ability of SBC and achieved lower contents of heavy metals (Pb, Cd, Cr, Ni, Hg, and As) in PCs than national standards of VBC (GB 25571-2011), revealing the value of SBC regeneration through FBP technology. This study provided insights for utilization of SBC and the recovery of residual oil.

Automated summary

This study utilized fluidized bed pyrolyser (FBP) to recover and regenerate spent bleaching clay (SBC), and found the potential for upgrading it into green fuels and chemicals. The decolorization ability of pyrolysis chars (PCs) increased with pyrolysis temperature, and the heavy metal content in PCs was lower than the national standards, highlighting the significance of this technology.