Sand Ore Research Articles

A modified model considering the influence of porosity on thermal conductivity of iron sand cement mortar based on cubic three-phase model

To improve calculation accuracy of cubic three-phase (CTP) model and figure out the influence of porosity on thermal conductivity, a thermal conductivity modified model for iron sand cement mortar (ICM) was proposed. Under the different water-cement (W/C) ratio, river sand-iron ore sand (R/I) ratio and sand-cement (S/C) ratio conditions, the experimental thermal conductivities of cement paste and ICM were measured by the laser flash method, and their theoretical thermal conductivities were calculated by CTP model. Moreover, the first functional relationship between ICM’s porosity and its experimental values of thermal conductivity, and the second functional relationship between ICM’s porosity and its theoretical values were both established using regression analysis. Afterwards, the difference between the first functional relationship and the second functional relationship was defined as the modified function in different conditions. Finally, the thermal conductivity modified model considering the porosity was proposed based on CTP model and modified function. The thermal conductivity modified model was compared with other theoretical models, and the results show that the modified values have a good agreement with experimental values, and it can enhance the calculation accuracy greatly. In this paper, a modified method between the experimental value and the theoretical value was proposed, which provides a practical basis and theoretical method for optimizing experimental value.

Determination and Understanding of Solvent Losses to Tailings from a Laboratory Hybrid Bitumen Extraction Process

Hybrid bitumen extraction (HBE) at ambient conditions has potential, as an alternative to the currently used modified Clark hot water extraction (CHWE), to reduce thermal energy intensity and greenhouse gas emissions for bitumen extraction from mined ore. Importantly, this extraction method could be retrofitted to the current commercial process. This research focuses on the extent of solvent loss in the sand tailings, which is the most important issue associated with the success and commercialization of HBE. In this work, a series of bench-scale HBE tests were conducted under various conditions, and the solvent content in the tailings was determined. Results suggest that the amount of solvent in the tailings depends largely on the processability of oil sand ore and the type and dosage of solvent used to soak the ore in the HBE. With a good processing ore, for which over 90% bitumen recovery was obtained, solvent losses to tailings were below the regulated volatile organic compound loss limit, without the ...

A Comparative Study of Fungal Community Structure, Diversity and Richness between the Soil and the Phyllosphere of Native Grass Species in a Copper Tailings Dam in Shanxi Province, China

In the study area, mining processes have led to the accumulation of a large amount of ore sand and a tailings dam was established above this artificial overburden. After a long period of restoration, the area was reclaimed by a variety of native vegetation. This study investigated four of these native grass species, namely, Bothriochloa ischaemum, Imperata cylindrica, Elymus dahuricus and Calamagrostis epigejos, having reestablished themselves after the restoration of a copper tailings dam built in 1969 in Shanxi Province, China. We analyzed the fungal community structure in the soil and the phyllosphere of the four native grass species using high-throughput sequencing. Results showed that the soil of the tailings dam was weakly alkaline and copper (Cu) was the most pervasive element present. Ascomycota were the dominant fungal taxa in the soil and the phyllosphere of all four native grass species, for which total soil nitrogen (N) content was an influencing factor. Basidiomycota was positively correlated to cadmium (Cd), which can additionally be used as an indicator of Cd pollution in copper tailings dams. Among the four native grass species, Nectriaceae was the dominant fungal family found exclusively in B. ischaemum; Meruliaceae and Phaeosphaeriaceae were the dominant fungal families of E. dahuricus; Cordycipitaceae and Sporormiaceae were only found in C. epigejos. However, we found no evidence of a dominant fungal family in I. cylindrica. Furthermore, Erythrobasidiales sp., which had the highest betweenness centrality after network analysis, was identified as the key fungal species in all four native grass species.

Probing Bitumen Liberation by a Quartz Crystal Microbalance with Dissipation

The detachment of bitumen from sand grains in oil sands processing is known as bitumen liberation. In this study, a quartz crystal microbalance with dissipation (QCM-D) was applied to study the bitumen liberation process under various process conditions. Bitumen was coated on the surface of silica sensors to simulate the oil sands ore. By recording the change of frequency and dissipation of the coated sensor, QCM-D allows for a real-time quantitative analysis of the bitumen detachment process. The effects of solid wettability, solution pH, and operation temperature on bitumen liberation were investigated using QCM-D. The effects of different solution pH values and temperatures on bitumen liberation were conducted with untreated hydrophilic silica sensors. It was found that the degree of bitumen liberation (DBL) was improved from 32 to 98% when the solution pH was increased from 7.8 to 11, indicating the importance of solution pH in the water-based bitumen extraction process. An increasing temperature enha...

Rapid Determination of Bitumen Content in Athabasca Oil Sands by Laser-Induced Breakdown Spectroscopy

Evaluation of bitumen content in oil sands feedstock is important to control the extraction process and improve the recovery efficiency. Current standard techniques for bitumen determination in oil sands ore suffer whether from their time-consuming labor intensive method of sample preparations or from requiring a high number of samples for calibration purposes. The analysis of bitumen ore samples is very challenging for the analytical chemist due to its nature of several phases of wet and dry particles and heterogeneous mixture of clay, bitumen, water, and solid contents. In this paper, we present a new enabling method using LIBS to determine rapidly and without sample preparation the bitumen content in oil sands ores. A qualitative study by principal component analysis was first done, and then a partial least-squares method was performed to assess the feasibility of determining bitumen by LIBS. The results show a good correlation between LIBS spectra and bitumen content and a prediction averaged absolute...

Asphaltene Precipitation in Paraffinic Froth Treatment: Effects of Solvent and Temperature

In surface-mined oil sands operations, bitumen is extracted from oil sand ore using a warm-water extraction process that produces bitumen froth typically containing 60 wt % bitumen, 30 wt % water, and 10 wt % mineral solids. The bitumen froth is then cleaned in a froth treatment process, in which the froth is diluted with solvent to enhance the separation of bitumen from water and solids. In paraffinic solvent froth treatment, light alkanes, such as pentane or hexane, are used as solvent, leading to precipitation of some of the asphaltenes in the bitumen. The precipitated asphaltenes form agglomerates with the solids and water, and these agglomerates quickly settle, producing very clean diluted bitumen. To precipitate the required amount of asphaltenes, the solvent/bitumen ratio used in commercial operations is typically high. In the present work, we investigated asphaltene precipitation using other solvents, such as butane, neopentane, and carbon dioxide, at different temperatures. It was found that the ...

Validation of the Theoretical Model of Determining the Strength of Cores Made by the Blowing Method

AbstractCore sands for blowing processes, belong to these sands in which small amount of the applied binding material has the ability of covering the sand matrix surface in a way which - at relatively small coating thickness - allows to achieve the high strength. Although the deciding factor constitute, in this aspect, strength properties of a binder, its viscosity and ability to moisten the matrix surface, the essential meaning for the strength properties of the prepared moulding sand and the mould has the packing method of differing in sizes sand grains with the coating of the binding material deposited on their surfaces.The knowledge of the influence of the compaction degree of grains forming the core on the total contact surface area can be the essential information concerning the core strength.Forecasting the strength properties of core sands, at known properties of the applied chemically hardened binder and the quartz matrix, requires certain modifications of the existing theoretical models. They should be made more realistic with regard to assumptions concerning grain sizes composition of quartz sands and the packing structure deciding on the active surface area of the contacts between grains of various sizes and - in consequence - on the final strength of cores.

Efficiency of Mn Removal of Different Filtration Materials for Groundwater Treatment Linking Chemical and Physical Properties

This paper presents research on Fe and Mn removal from groundwater. In treatment systems of aeration followed by rapid filtration (no chemical dosage), manganese removal is possible due to the manganese dioxide catalyst present on the grains of filtration material. The goal of the presented research was to find a correlation between the catalyst layer’s composition as well as its internal porosity and the effectiveness and stability of manganese removal in the filtration process. In order to establish the influence of catalyst characteristics on manganese removal effectiveness, the filtration experiment was conducted using filtration materials with catalytic contact layers of different origin. Oxide coated auto-activated silica sand and Gabon manganese ore were tested. Inactive silica sand was used as reference. The results of filtration experiments were combined with analyses of chemical composition, internal porosity, and crystalline parameters of catalyst contact layers of grains. For the determination catalyst contact layer parameters, the following methods were used: Raman spectroscopy, X-ray powder diffractometry (XRD), Scanning Electron Microscope – Energy dispersive spectroscopy (SEM-EDAX), nitrogen adsorption. Pilot scale research on the filtration process demonstrated that auto-activated filtration material was characterized by the highest efficiency of manganese removal and stability of effects during the whole research. The effectiveness of Gabon manganese ore dropped from 90% and stabilized on the level of ca. 60% within 15 days of the experiment.

Predicting the abundance of clays and quartz in oil sands using hyperspectral measurements

Clay minerals play a crucial role in the processability of oil sands ores and in the management of tailings. An increase in fine content generally leads to a decrease in both bitumen recovery performance and tailings settling rate. It is thus important to identify clay types and their abundance in oil sands ores and tailings. This study made use of oil sands samples characterized for quantitative mineralogy by x-ray diffraction, to gain an understanding of changes in the reflectance spectra of oil sands. The sample suite included bitumen-removed oil sands ore samples and their different fine size fractions. Spectral metrics applicable to the prediction of quartz and clay contents in oil sands were then derived with a focus on metrics correlating with sample content in total 2:1 clays (total of illite and illite-smectite) and kaolinite. Metrics in the shortwave infrared (SWIR) and longwave infrared (LWIR) were found to correlate with mineral contents. The best predictions of clays and quartz were achieved using LWIR metrics (R2>0.89). Results also demonstrated the applicability of LWIR metrics in the prediction of kaolinite and total 2:1 clays.

Methanogenic biodegradation of paraffinic solvent hydrocarbons in two different oil sands tailings.

Microbial communities drive many biogeochemical processes in oil sands tailings and cause greenhouse gas emissions from tailings ponds. Paraffinic solvent (primarily C5-C6; n- and iso-alkanes) is used by some oil sands companies to aid bitumen extraction from oil sands ores. Residues of unrecovered solvent escape to tailings ponds during tailings deposition and sustain microbial metabolism. To investigate biodegradation of hydrocarbons in paraffinic solvent, mature fine tailings (MFT) collected from Albian and CNRL ponds were amended with paraffinic solvent at ~0.1wt% (final concentration: ~1000mgL-1) and incubated under methanogenic conditions for ~1600d. Albian and CNRL MFTs exhibited ~400 and ~800d lag phases, respectively after which n-alkanes (n-pentane and n-hexane) in the solvent were preferentially metabolized to methane over iso-alkanes in both MFTs. Among iso-alkanes, only 2-methylpentane was completely biodegraded whereas 2-methylbutane and 3-methylpentane were partially biodegraded probably through cometabolism. 16S rRNA gene pyrosequencing showed dominance of Anaerolineaceae and Methanosaetaceae in Albian MFT and Peptococcaceae and co-domination of "Candidatus Methanoregula" and Methanosaetaceae in CNRL MFT bacterial and archaeal communities, respectively, during active biodegradation of paraffinic solvent. The results are important for developing future strategies for tailings reclamation and management of greenhouse gas emissions.

Aggregate Effects on γ-ray Shielding Characteristic and Compressive Strength of Concrete

We observed the γ-ray shielding characteristics and compressive strength of five types of concrete using general aggregates and high-weight aggregates. The aggregates were classified into fine aggregate and coarse aggregate according to the average size. The experimental results obtained an attenuation coefficient of 0.371 cm-1 from a concrete with the oxidizing slag sand (OSS) and oxidizing slag gravel (OSG) for a γ-ray of 137Cs, which is improved by 2% compared with a concrete with typical aggregates of sand and gravel. In the unit weight measurement, a concrete prepared by iron ore sand (IOS) and OSG had the highest value of 3,175 kg·m-3. Although the unit weight of the concrete with OSS and OSG was 3,052 kg·m-3, which was lower than the maximum unit weight condition by 123 kg·m-3, its attenuation coefficient was improved by 0.012 cm-1. The results of chemical analysis of aggregates revealed that the magnesium content in oxidizing slag was lower than that in iron ore, while the calcium content was higher. The concrete with oxidizing slag aggregates demonstrated enhanced γ-ray shielding performance due to a relatively high calcium content compared with the concrete with OSS and OSG in spite of a low unit weight. All sample concretes mixed with high-weight aggregates had higher compressive strength than the concrete with typical sand and gravel. When OSS and IOS were used, the highest compressive strength was 50.2 MPa, which was an improvement by 45% over general concrete, which was achieved after four weeks of curing.

Impact of salinity on warm water‐based mineable oil sands processing

AbstractContinuous use of caustics and increased level of water recycling inevitably increase the salinity of process water, which is a growing challenge in the current warm water‐based bitumen extraction process. The current study aims at understanding how salinity of process water affects bitumen recovery from mineable oil sands ores. Laboratory flotation results showed an ore‐dependent effect of salinity on bitumen recovery and froth quality. Processing of low‐grade ores suffered a dramatic loss in bitumen recovery with increasing NaCl up to 4000 ppm (i.e. 1574 ppm Na+) at pH 8.5, while only a marginal effect of salinity was found on the processability of a high‐grade ore. The use of caustics as a conventional approach to increase bitumen recovery and froth quality of poor processing ores showed a more severe negative impact of salinity on the processability of low‐grade ores. Salt addition was found to be detrimental to bitumen liberation and bitumen‐bubble attachment in the presence of fines, more so at higher pH of processing water. Increasing salt concentration in solution led to a significant decrease in the magnitude of negative zeta potentials for both bitumen and fine solids. These findings provide scientific guidance to searching for remediation strategies other than using caustics. Such an approach studied was the blending of low‐grade ores with high‐grade ores to minimize the negative impact of increased salinity in recycle water on bitumen extraction.

Review of biological processes in oil sands: a feasible solution for tailings water treatment

The bitumen extraction process from Athabasca oil sands ore produces large quantities of toxic processed water as tailings. The oil industry has reduced the demand for fresh water in the extraction process by recycling this tailings water. Continual recycling increases the toxicity of tailings water many times over, and poses a serious threat to surface and groundwater quality. For a sustainable expansion of Canada’s oil sands industry, it is essential to develop a technically practicable and economically feasible tailings water treatment technology. A review was carried out to describe the integral role of biological processes in oil sands history for identifying a successor tailings water treatment technology. This study proposes the application of an entrapped cells system as a feasible solution for tailings water treatment. Bio-augmentation followed by entrapment of the microbial community indigenous to tailings ponds can be a promising tailings water treatment technology.

Trace metal mobilization from oil sands froth treatment thickened tailings exhibiting acid rock drainage

Froth treatment thickened tailings (TT) are a waste product of bitumen extraction from surface-mined oil sands ores. When incubated in a laboratory under simulated moist oxic environmental conditions for ~450d, two different types of TT (TT1 and TT2) exhibited the potential to generate acid rock drainage (ARD) by producing acid leachate after 250 and 50d, respectively. We report here the release of toxic metals from TT via ARD, which could pose an environmental threat if oil sands TT deposits are not properly managed. Trace metal concentrations in leachate samples collected periodically revealed that Mn and Sr were released immediately even before the onset of ARD. Spikes in Co and Ni concentrations were observed both pre-ARD and during active ARD, particularly in TT1. For most elements measured (Fe, Cr, V, As, Cu, Pb, Zn, Cd, and Se), leaching was associated with ARD production. Though equivalent acidification (pH2) was achieved in leachate from both TT types, greater metal release was observed from TT2 where concentrations reached 10,000ppb for Ni, 5000ppb for Co, 3000ppb for As, 2000ppb for V, and 1000ppb for Cr. Generally, metal concentrations decreased in leachate with time during ARD and became negligible by the end of incubation (~450d) despite appreciable metals remaining in the leached TT. These results suggest that using TT for land reclamation purposes or surface deposition for volume reduction may unfavorably impact the environment, and warrants application of appropriate strategies for management of pyrite-enriched oil sands tailings streams.

Oil sands tailings ponds harbour a small core prokaryotic microbiome and diverse accessory communities

Oil sands tailings ponds store the waste slurry generated by extracting bitumen from surface-mined oil (tar) sands ores. The ponds support diverse microbial communities involved in element cycling, greenhouse gas production, and hydrocarbon biodegradation that influence pond management and their environmental footprint. Since previous reports indicate that there are similar microbial metabolic functions amongst ponds, analogous microbiomes may be expected but ponds actually harbour distinct communities. Partial 16S rRNA gene pyrotag sequences from 95 samples were obtained from six ponds managed by three operators. From these we discerned a core prokaryotic microbiome, a subset of microbes shared amongst different samples, defined as operational taxonomic units (OTUs) at the lowest taxonomic level identifiable in individual ponds and pooled pond datatsets. Of the ∼1500–2700 OTUs detected per pond, 4–10 OTUs were shared among ≥75% of the samples per pond, but these few OTUs represented 39–54% of the ponds’ sequence reads. Only 2–5 OTUs were shared by the majority of samples from all ponds. Thus the prokaryotic communities within these ponds consist of a few core taxa and numerous accessory members that likely afford resiliency and functional redundancy including roles in iron-, nitrogen- and sulfur-cycling, syntrophy, fermentation, and methanogenesis.

Next-Generation Sequencing Assessment of Eukaryotic Diversity in Oil Sands Tailings Ponds Sediments and SurfaceWater.

Tailings ponds in the Athabasca oil sands (Canada) contain fluid wastes, generated by the extraction of bitumen from oil sands ores. Although the autochthonous prokaryotic communities have been relatively well characterized, almost nothing is known about microbial eukaryotes living in the anoxic soft sediments of tailings ponds or in the thin oxic layer of water that covers them. We carried out the first next-generation sequencing study of microbial eukaryotic diversity in oil sands tailings ponds. In metagenomes prepared from tailings sediment and surface water, we detected very low numbers of sequences encoding eukaryotic small subunit ribosomal RNA representing seven major taxonomic groups of protists. We also produced and analysed three amplicon-based 18S rRNA libraries prepared from sediment samples. These revealed a more diverse set of taxa, 169 different OTUs encompassing up to eleven higher order groups of eukaryotes, according to detailed classification using homology searching and phylogenetic methods. The 10 most abundant OTUs accounted for >90% of the total of reads, vs. large numbers of rare OTUs (<1% abundance). Despite the anoxic and hydrocarbon-enriched nature of the environment, the tailings ponds harbour complex communities of microbial eukaryotes indicating that these organisms should be taken into account when studying the microbiology of the oil sands.

Characterization of physical mass transport through oil sands fluid fine tailings in an end pit lake: a multi-tracer study

Soft tailings pose substantial challenges for mine reclamation due to their high void ratios and low shear strengths, particularly for conventional terrestrial reclamation practices. Oil sands mine operators have proposed the development of end pit lakes to contain the soft tailings, called fluid fine tailings (FFT), generated when bitumen is removed from oil sands ore. End pit lakes would be constructed within mined-out pits with FFT placed below the lake water. However, the feasibility of isolating the underlying FFT has yet to be fully evaluated. Chemical constituents of interest may move from the FFT into the lake water via two key processes: (1) advective-diffusive mass transport with upward pore water flow caused by settling of the FFT; and (2) mixing created by wind events or unstable density profiles through the lake water and upper portion of the FFT. In 2013 and 2014, temperature and stable isotopes of water profiles were measured through the FFT and lake water in the first end pit lake developed by Syncrude Canada Ltd. Numerical modelling was undertaken to simulate these profiles to identify the key mechanisms controlling conservative mass transport in the FFT. Shallow mixing of the upper 1.1 m of FFT with lake water was required to explain the observed temperature and isotopic profiles. Following mixing, the re-establishment of both the temperature and isotope profiles required an upward advective flux of approximately 1.5 m/year, consistent with average FFT settling rates measured at the study site. These findings provide important insight on the ability to sequester soft tailings in an end pit lake, and offer a foundation for future research on the development of end pit lakes as an oil sands reclamation strategy.

사일로의 경제적인 설계 기준 제시

Previous domestic studies on silos have been carried out in many ways in various fields. On the other hand, research on the design and construction of the silo itself have not be conducted actively and an economical approach is rare. The present study provides basic information to determine the scale of the most economical silo, while satisfying the necessary conditions required by construction companies or design firms. The analysis was carried out with various parameters for reinforced concrete structures, including four kinds of storage material (flour, granulated quicklime, sand, and iron ore), five capacity sizes (10,000, 30,000, 50,000, 70,000, 90,000 ton), eight variants of H/D (0.5~4), and three types of concrete compressive strengths (30, 35, 40 MPa). The findings established a general rule in that a silo designed between 1 and 3 H/D with a greater concrete strength (40MPa and over) depending on the type of storage material would be the most cost-effective (more than 50% of quantity and labor savings).

Understanding the roles of switchable-hydrophilicity tertiary amines in recovering heavy hydrocarbons from oil sands

A kind of novel process aids, switchable-hydrophilicity tertiary amines (SHTAs, such as triethylamine, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine) in their hydrophilic forms, have been synthesized and applied to enhancing heavy hydrocarbons recovery from oil sands ores in the solvent extraction. It is observed that the addition of SHTA solution increases the recovery of heavy hydrocarbons and improves the quality of bitumen product (less solids entrained) and residual solids (less solvents and chemicals attached). According to the surface characterizations by FT-IR, SEM–EDS, wettability test, zeta potential measurements and QCM-D (a surface material adsorption detection), it is found that the external addition of SHTAs solution plays an important role in modifying the bitumen and solids surfaces. The improved processability was mainly attributed to the absorption of cation ions (e.g., [Et3NH]+) of SHTAs on bitumen surface, forming ions pairs. The formation of ions pairs reduces the interactions between bitumen components (e.g., asphaltenes or other polar materials) and the solid surface, which significantly increases the wettability of solid surfaces. Consequently, the detachment of bitumen materials from the solid surfaces becomes much easier and more complete. In addition, the efficiency of the recycled SHTAs is found to be not influenced much even the SHTAs are recycled for 5 times, indicating a promising application of this kind of ‘green chemicals’ in unconventional petroleum production or soil remediation.

Airborne Petcoke Dust is a Major Source of Polycyclic Aromatic Hydrocarbons in the Athabasca Oil Sands Region.

Oil sands mining has been linked to increasing atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) in the Athabasca oil sands region (AOSR), but known sources cannot explain the quantity of PAHs in environmental samples. PAHs were measured in living Sphagnum moss (24 sites, n = 68), in sectioned peat cores (4 sites, n = 161), and snow (7 sites, n = 19) from ombrotrophic bogs in the AOSR. Prospective source samples were also analyzed, including petroleum coke (petcoke, from both delayed and fluid coking), fine tailings, oil sands ore, and naturally exposed bitumen. Average PAH concentrations in near-field moss (199 ng/g, n = 11) were significantly higher (p = 0.035) than in far-field moss (118 ng/g, n = 13), and increasing temporal trends were detected in three peat cores collected closest to industrial activity. A chemical mass-balance model estimated that delayed petcoke was the major source of PAHs to living moss, and among three peat core the contribution to PAHs from delayed petcoke increased over time, accounting for 45-95% of PAHs in contemporary layers. Petcoke was also estimated to be a major source of vanadium, nickel, and molybdenum. Scanning electron microscopy with energy-dispersive X-ray spectroscopy confirmed large petcoke particles (>10 μm) in snow at near-field sites. Petcoke dust has not previously been considered in environmental impact assessments of oil sands upgrading, and improved dust control from growing stockpiles may mitigate future risks.