Empirical models for the density and the viscosity of squalane (C30H62; 2,6,10,15,19,23-hexamethyltetracosane) have been developed based on an exhaustive review of the data available in the literature and new experimental density and viscosity measurements carried out as a part of this work. The literature review showed there was a substantial lack of density and viscosity data at high temperature (373 to 473) K and high pressure conditions (pressures up to 200 MPa). These gaps were addressed with new experimental measurements carried out at temperatures of (338 to 473) K and at pressures of (1 to 202.1) MPa. The new data were utilized in the model development to improve the density and viscosity calculation of squalane at all conditions including high temperatures and high pressures.The model presented in this work reproduces the best squalane density and viscosity data available based on a new combined outlier and regression algorithm. The combination of the empirical models and the regression approach resulted in models which could reproduce the experimental density data with average absolute percent deviation of 0.04%, bias of 0.000%, standard deviation of 0.05%, and maximum absolute percent deviation of 0.14% and reproduce the experimental viscosity data with average absolute percent deviation of 1.4%, bias of 0.02%, standard deviation of 1.8% and maximum absolute percent deviation of 4.9% over a wide range of temperatures and pressures. Based on the data set used in the model regression (without outliers), the density model is limited to the pressure and temperature ranges of (0.1 to 202.1) MPa and (273 to 525) K, while the viscosity model is limited to the pressure and temperature ranges of (0.1 to 467.0) MPa and (273 to 473) K. These models can be used to calibrate laboratory densitometers and viscometers at relevant hightemperature, high-pressure conditions.

Coating of bitumen by clays, known as slime coating is detrimental to bitumen recovery from oil sands using the warm slurry extraction process. Sodium hydroxide (caustic) is added to the extraction process to balance many competing processing challenges which include undesirable slime coating. The current research aims at understanding the role of caustic addition in controlling interactions of bitumen with various types of model clays. The interaction potential was studied by quartz crystal microbalance with dissipation monitoring (QCM-D). After confirming the slime coating potential of montmorillonite clays on bitumen in the presence of calcium ions, interaction of kaolinite and illite with bitumen was studied. To make our study more closely related to industrial applications, tailings water from bitumen extraction tests using Denver flotation cell at different caustic additions was used. At caustic dosage up to 0.5 wt.% of oil sands ore, a negligible coating of kaolinite on the bitumen was determined. However, at lower level of caustic addition illite was shown to attach to the bitumen, with the interaction potential decreasing with increasing caustic dosage. Increasing concentration of humic acids as a result of increasing caustic dosage was identified to limit the interaction potential of illite with bitumen.2 This fundamental study clearly shows that the critical role of caustics in modulating interactions of clays with bitumen depends on the type of clays, guiding the multi-billion dollar oil sands industry to identify clay type as a key operational variable.

No abstract

Coastal ecosystems are impacted by excessive nutrient inputs that cause degradation of water quality and impairments of ecosystem functioning. Regulatory and management efforts to enhance nutrient export from coastal ecosystems include sustainable oyster aquaculture that removes nitrogen in the form of oyster biomass and increases particulate export to underlying sediments where increased organic material may enhance microbial denitrification. To better understand the impacts of oyster aquaculture on nitrogen removal, we examined bacterial processes in sediments underlying three of the most common aquaculture methods that vary in the proximity of oysters to the sediments. Sediment samples underlying sites managed with these different aquaculture methods were examined using the 16S rRNA gene to assess microbial community structure, gene expression analyses to examine nitrogen and sulfur cycling genes, and nitrogen gas flux measurements. All sites were located in the same hydrodynamic setting within Waquoit Bay, MA during 2018 and 2019. Although sediments under the different oyster farming practices showed similar communities, ordination analysis revealed discrete community groups formed along the sampling season. Measured N2 fluxes and expression of key genes involved in denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) increased during mid-summer and into fall in both years primarily under bottom cages. While all three oyster growing methods enhanced nitrogen removal relative to the control site, gene expression data indicate that the nitrogen retaining process of DNRA is particularly enhanced after end of July under bottom cages, and to a lesser extent, under suspended and floating bags. The choice of gear can also potentially increase processes that induce nitrogen retention in the form of ammonia in the underlying sediments over time, thus causing deviations from predicted nitrogen removal. If nitrogen removal is a primary objective, monitoring for these shifts is essential for making decisions about siting and size of aquaculture sites from year to year.

No abstract

This paper describes co-processing of fresh tailings (i.e. whole tailings), such as coarse tailings and flotation tailings from the oil sand extraction plant, and legacy fluid fine tailings (FFT) in line with a polymeric flocculant to produce paste tailings without the use of thickeners and cyclones. The objective of the project is to develop an efficient and low-cost tailings management technology to accelerate the creation of trafficable landforms that are ready for terrestrial reclamation. The idea for co-processing is that increasing the sand-to-fines ratio (SFR) will increase the hydraulic conductivity of the co-processed deposit, thus accelerating its consolidation rate. Compared to composite tailings (CT) with SFR of 3-5 and FFT centrifuge cake or flocculated FFT (fFFT) with SFR of 0-0.1, the target SFR of co-processing is 1-3 with an optimal SFR of 2. In a broader definition, the co-processing could become the treatment of whole tailings when the FFT supply is shut down or switch to the flocculated FFT process if the fresh tailings are diverted for conventional beaching operation. This paper highlights the advancements in co-processing technology development from laboratory-scale to small pilot-scale. It discusses learnings from large strain consolidation (LSC) and beam centrifuge testing of the coprocessed deposits to assess its long-term consolidation within the context of final reclamation and closure. Results to date show that co-processing of fresh tailings and FFT is a promising technology for achieving terrestrial closure of oil sand tailings.

No abstract

No abstract