Enhanced accumulation of bitumen residue in a highly concentrated tailings flow by microbubbles from in-situ catalytic decomposition of hydrogen peroxide

TL;DR

The study addresses the environmental challenge of residual bitumen in oil sands tailings by leveraging in-situ microbubble generation from catalytic decomposition of $H_{2}O_{2}$ in a lab-scale hydrotransport pipeline. It systematically analyzes how $H_{2}O_{2}$ dosage and injection duration, along with magnetic mineral content, influence microbubble formation and bitumen recovery, comparing artificial and real tailings. The key finding is that total $H_{2}O_{2}$ dosage dominates bubble production and recovery, enabling rapid aggregation of bitumen at the top of the flow and achieving >70% recovery within 30 minutes under low initial bitumen content; real tailings show even more pronounced bubble formation due to catalytically active minerals. Importantly, this method eliminates the need for additional microbubble-generation hardware, offering a potentially economical and environmentally favorable route for concentrating and removing oily residues from tailings.

Abstract

The massive volume of oil sands tailings has been one of the most challenging environmental issues. In this work, we experimentally explore a simple and effective approach to bitumen residue separation from a highly concentrated slurry flow of the artificial oil sands tailings. By utilizing microbubbles from in-situ catalytic decomposition of H2O2 at low concentrations, bitumen aggregation is enhanced on the top part of the hydrotransport pipeline. The microscopic image analysis revealed the in-situ formation of microbubbles and confirmed that magnetic particles present in the slurries contributed to the fast release of the gas products and bubble formation from hydrogen peroxide decomposition. A high-speed camera was applied to capture images of the tailings flow in the pipeline through a transparent view window. A large number of tiny bubbles were identified post to the injection of H2O2 to the slurry flow. More than 70 % bitumen could be recovered from a lab-scale pipeline loop within 30 mins after injection. The bitumen recovery efficiency from the collected froth was quantitatively compared under seven conditions with varied dosages, the concentration of H2O2, and the amount of magnetic solids in the slurries. Our results confirmed that the total dosage of H2O2 is the dominant factor in in-situ microbubble formation for enhanced bitumen aggregation in the flow. Importantly, microbubbles were generated rapidly in the real mature fine tailings. The results from our study provide insights into the preferential distribution of oil residue in the flow during hydrotransport without the requirement for an additional device. Removal of oily residues from concentrated slurries may bring economical and environmental advantages.

Figures (12)

• Figure 1: Schematic of lab-scale pipeline loop with $H_{2}O_{2}$ injection from the trough; $V_m$: slurry velocity in the main loop motamed2020microbubblewallwork2004processibility.
• Figure 2: (A) bottom view of bubble generation by $H_{2}O_{2}$ decomposition on the glass substrate. High-speed camera setup: (B) Top positioned lens with a light source, (C) bottom positioned lens with the light source and mirror, and (D) Cross-section sketch of the setup.
• Figure 3: Observation of recovered froth in the trough: (A) Case 6, (B) Case 7, (C) Case 2, and (D) Case 5. Bitumen recovery with injection time: (E) 5 $min$: case 2, 6, and (F) 25 $min$: case 5, 7.
• Figure 4: Observation of recovered froth in the trough: (A) 25 $min$, and (B) 12 $min$. Bitumen recovery with the same concentration increase rate: (C) 6 $mL$$H_{2}O_{2}$ injected for 12 minutes and 12 $mL$$H_{2}O_{2}$ injected for 25 minutes.
• Figure 5: Bitumen recovery with 12 $mL$$H_{2}O_{2}$: (A) Injection time: 5 $min$ and 25 $min$. Composition in the recovered froth: (B) bitumen, (C) solid, and (D) water. Weight of recovered impurities: (E) bitumen, (F) solid, and (G) water.