2018 Conference Abstracts
Lime (CaO) as Additives for Bitumen Extraction, Tailings Disposal
and FFT Dewatering Processes
Author: B. Ozum, S. Arnipally and J.D. Scott
Organization: Apex Engineering Inc
Oil sands plants use some versions of Clark’s Hot Water Extraction (CHWE) process of 1930s, which uses caustic NaOH additive to achieve acceptable bitumen extraction efficiency. CHWE process provides acceptable bitumen recovery efficiency; however, it causes sincere challenges for bitumen extraction, fluid fine tailings (FFT) disposal, process water chemistry and long-term sustainability of the oil sands plants. Oil sands industry has developed bitumen extraction, tailings disposal and FFT dewatering processes with some commercial success; however, novel processes are needed for further improvements to deal with these challenges, in simple and cost effected manners.
Our research is devoted to developing novel bitumen extraction, tailings disposal and FFT dewatering processes, simultaneously improving process water chemistry and long terms sustainability of oil sands plants. All these processes are based on the use of lime (CaO) as additives at different dosages, by utilizing the unique advantages of CaO chemistry in oil sands ore-water slurry systems. CaO additive provides hydroxyl ions (OH-), like NaOH of CHWE process, which increases pH and reacts with bicarbonates (HCO3-). Advantage of using CaO is that, it provides Ca2+ too, which simultaneously reacts with clay species and water soluble naphthenic acids salts. These properties of CaO could be utilized to improve efficiency of bitumen extraction, tailings disposal practices, dewatering of existing FFT and improve long term sustainability of oil sands plants in simple and cost-effective manners. Experimental data on the use of CaO as additives for a wide range of unit operations of the oil sands plants, such as bitumen extraction, whole tailings, production of nonsegregating tailings, dewatering of exiting FFT process will be presented. It will be presented oil sands industry that sufficiently large data pools are available for successful design, commission and execution of field trials of these processes before their commercial implementations.
Canadian Mining Innovation: Advancing through Collaboration and Sustainability
Author: Janice Zinck
With is vast and rich mineral resources, skilled workforce and strong investment and regulatory frameworks Canada is recognized as a leader in mineral resource development. Although Canada remains a global leader, when compared to other resource sectors, the mining sector has begun to lag behind in the uptake of advanced technologies. As a result of this gap, the sector is currently at risk of falling behind other nations that have embraced the necessity to support innovation as a means to create a more sustainable resource model both environmentally and economically. To succeed, the sector must become adept at overcoming existing silos and embrace collaboration to better implement new technologies, practices and processes. Mining innovation cannot take place in isolation and all stakeholders in the ecosystem most pull together to work in coordination for success. There is also an opportunity to build on the Canada brand through leading practices of collaboration, green and sustainable practices, technological excellence and inclusive engagement.
A Comparison of Trommel Screens versus Vibrating Screens in the Oil Sands Industry
Author: Anthony Yell
Organization: Tema Isenmann
This Paper will discuss the features & benefits of using Trommel Screens versus Vibrating Screens in the Oil Sands Industry. Both Screening units are suitable for scalping off oversize in the Tailings circuit. We will also discuss the differences between Rotary Breakers and Trommel Screens.
The objective of this paper, is to give the delegate, an in-site into the different types Screening technologies available to enable them to choose the most appropriate technology for their application.
We will discuss the critical aspects of the feed arrangement to these different units, the feed rates, feed size and operational requirements.
Screen design considerations are another important factor and we will review the different aspects of design for these type of applications.
For these duties the design of the Screen Panels has proven to be a challenge over the years & we will discuss the evolution of these screen panels to what is used at present to achieve longer life and a reduction in maintenance downtime.
The differences in Screen action between Trommel Screens & Vibrating Screens will be explained showing the features & benefits of each action.
Finally we will review maintenance requirements of these units.
On-stream particle size analysis for oil sands tailings treatment
Author: Erfan Sharifi
The oil sands resources in Canada are one of the world’s largest hydrocarbon deposits. Processing of oil sands uses hot water to extract bitumen. The process generates tailings slurry that must be settled for final deposition. The tailings contain fine material, with poor water release characteristics which makes water recovery challenging. Polymer flocculants are added to assist in settling and dewatering the fine tailings. The amount of polymer addition is dependent on tailings characteristics, including the particle size distribution (PSD). If the PSD of the tailings is unknown, an excess amount of polymer needs to be added in the dewatering stage to flocculate the particles. Over flocculation also has a detrimental effect on the water release characteristics. Measuring the particle size distribution using an on-line analyzer could have major benefits over common laboratory methods as it provides online and fast insight into the process enabling the operators to implement required changes to minimize the reagent consumption, while achieving optimal flocculation. Online measurement of PSD using laser diffraction has long been used in base metals beneficiation processes. A series of test work using Outotec PSI500® particle size analyzer on oil sands samples from different operations have been conducted. Tests were performed by recirculating the slurry in closed circuit to simulate real plant conditions.
Impact of Calcium Hydroxide Coagulation of Fluid Fine Tailings
during Centrifuge Dewatering
Author: M. Tate, N. Romaniuk, J. Leikam, J. Fox, A. Nguyen, N. Hariharan
Fluid fine tailings (FFT) from oil sands mining operations have proven difficult to dewater and reclaim. Complex water chemistry, presence of clay particles and small amounts of residual bitumen in tailings slurry are obstacles to achieving the geotechnical characteristics required for landform reclamation.
The addition of calcium hydroxide (lime) as both a coagulant and flocculant for centrifuge dewatering of tailings is explored in this work. Previous work demonstrated that tailings treated with calcium hydroxide can dewater to higher percent solids (greater than 65%) at a fast rate in a pressure filtration process. Though some improvement in particle size is observed, surface modification of clays in the tailings appears to be the primary mechanism for dewatering. The dose of calcium hydroxide required for this dewatering achieves a pH of at least 12.0. At this pH level and above, pozzolanic reactions occur between calcium hydroxide and silica and alumina compounds in the clay, modifying its structure in a way similar to cement. The purpose of this work was to examine if similar dewatering could be achieved in the shorter residence time of a centrifuge.
Achieving a balance between cake solids content and centrate quality was challenging in this initial work. While solids content in the cake varied with feed rate, lime was demonstrated to enhance fines capture in the cakes. At high feed rates, centrifuge cakes exceeded 50% solids for all lime dosage levels; however, centrate solids levels were above 3% solids. Decreasing the feed rate resulted in lower cake solids levels but improved centrate clarity at high lime dose levels (4.0 kg/wet tonne FFT). Measurements of cake undrained shear strength and Atterberg limits demonstrate that lime provides time dependent strength development and liquidity index reduction. At high lime dose levels, liquid limit drops below 50% and undrained shear strength values increased within 90 days. Further, residual centrate solids settled quickly at high lime dose levels. Options for beneficially utilizing the centrate are discussed.
Dewatering levels seen during pressure filtration testing were not achieved in these initial tests. Despite lower solids levels than expected, good strength development and a significant reduction in the liquid limit was seen with the treated cake over time. This holds promise for the development of a treated tailings material that is easily capped. More work is needed to optimize the performance of lime in this system.
Froth Flotation in Oil Sands:
Outside Perspective from the Minerals Industry
Author: Tim Sheehan
Froth flotation technology adapted from the minerals flotation industry is commonly applied in various ways within the oil sands flowsheet for separation of residual oil remaining after the primary separation process. However, the transfer of “The Art of Flotation”, i.e., the expertise and know-how of operating a flotation plant, may not have been transferred as successfully. In a minerals concentrator, the froth flotation circuit is subject of perpetual study and endless optimization, but in an oil sands plant the flotation process often becomes a “black box”. What opportunity does this present to improve performance and reduce the loss of oil to tailings? This presentation will discuss some of the differences between flotation in the minerals industry and flotation in oil sands, with particular focus on technology developments, multi-stage flotation circuits, and operating philosophies.
Oil Sands Greenhouse Gas Emissions:
Facts, Challenges, Path Forward
Facilitator: Dragan Pejic
Organization: Government Of Alberta