Andy Hong, PhD , University of Utah
1. Reactor modification
Baffle rings were constructed from PVC material and set up in a Parr 5100 low-pressure stainless steel reactor to promote particle collision and release of bitumen from sands. Stainless steel mesh plates were placed horizontally just below the water surface to promote particle retention by flotation lifting during decompression. The extent of bitumen release and the bitumen compositions in the floated materials were studied as a function of operation parameters and decompression rate.
2. Water-to-solid ratio
The effect of water-to-solid ratio on extraction rate and froth quality was studied. That the ratio has a significant effect on the extraction extent and the bitumen quality showing more desirable outcomes with less water was counterintuitive. Lower water-to-solid ratios (1-2) resulted in much higher extraction rate than did higher water-to-solid ratio (~10). Collisions of oil sands particles among themselves and with baffle structure are an important factor for bitumen release from sands.
3. Gas decompression speed
The effects of gas decompression speed on bitumen release and froth quality were studied. Low decompression speed increased bitumen content in the froth, while fast decompression speed increased bitumen recovery rate. The dynamics of decompression speed and the optimal combination is being further investigated.
4. Process water quality
Process water quality from the bitumen-hot water process was analyzed. The process water contained less solids, alkalinity, and COD than typical oil sand tailing pond water reported in the literature. The process water appears to be amenable to conventional treatment as by sand filtration before extraction and poised for process reuse or discharge. Preliminary results showed reductions of COD in the process water from 242 mg/L to 78 mg/L and of turbidity down to 0.45 NTU.
5. Spent sands
The oil sand-hot water contact process created spent sands that readily separated from the water column via gravity settling. Removal by 99.98% of the suspend solids was completed in less than 30 minutes by gravitational settling, with a concomitant reduction of turbidity by 90% within 2 hours. The settled sands contained 1-3% of residual organics and its potential beneficial uses are being explored.