Efficient oil recovery from highly stable toxic oily sludge using supercritical water. (1st January 2019)

• Record Type: Journal Article
• Authors: Khan, Muhammad Kashif; Cahyadi, Handi Setiadi; Kim, Sung-Min; Kim, Jaehoon
• Is Part Of: Fuel. Volume 235(2019)
• Page Start: 460
• Page End: 472
• Publication Date: 2019-01-01
• Subjects: Oily sludge -- Supercritical water -- Rag layer -- Petroleum emulsion -- Naphthenic acids; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2018.08.003
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: Complete demulsification of toxic oily sludge by non-catalytic supercritical water. Efficient oil recovery of 75–80 wt% with negligible coke and gas formation. Asphaltenes, nitrogen and residue reduction were 90, 82 and 68% respectively at 400 °C. Acidity and heavy metals were sufficiently reduced. Alkyl-CO2 and Aryl-CO2 bond scissions are major pathways for deacidification. Abstract: One of the main challenges in crude oil extraction and refining is the formation of highly toxic intractable petroleum emulsions (oily sludge). Herein, the simultaneous demulsification and recovery of oil with low impurity content, trapped in petroleum emulsions, was investigated using supercritical water (scH2 O). Various parameters, including temperature (350–400 °C), pressure (25–35 MPa), emulsion concentration (10–100 wt%), and reaction time (30–120 min) were explored to establish the optimized conditions. At 400 °C, the asphaltene content (23.7–3.4 wt%) and total acid number (15.4–2.8 mg-KOH/g-oil) decreased significantly, while the naphtha-to-diesel fraction increased from 9 to 21 wt%. These results indicated effective cracking of the toxic interfacially active species to form their non-toxic, non-interfacially active counterparts. By removing the interfacially active compounds that stabilize the petroleum emulsion, clear oil-water separation was achieved after conversion in scH2 O, thereby facilitating the recovery of the upgraded oil. Additionally, heteroatoms and metallic impurities in the upgraded oil were significantly reduced [reduction efficiencies: 79% (V), 69% (Ni), 99% (Ca), 23% (S), 82% (N)]. Finally, plausible reaction mechanisms for the removal of interfacially active compounds were discussed using model compound reactions.