Sept/Oct 2010

Innovation

Innovations in tailings management

By Nicholas Beier and Dave Sego

OSTRF

Preparing an in-line dewatering experiment at the OSTRF  | Photo courtesy of Michael Holly


The vast amount of disturbed land and the quantity of oil sands tailings being stored presents a challenge for the industry and an opportunity for the University of Alberta’s Oil Sands Tailings Research Facility (OSTRF). Industry endeavours to study the fundamentals of particular issues associated with tailings management require coordinating the efforts of researchers from diverse backgrounds and graduate students from various disciplines. This impediment was recognized by the stakeholders who came together to support the OSTRF.

The OSTRF is a unique academic and industrial research facility dedicated to collaborative and multidisciplinary oil sands tailings research. The facility provides crucial infrastructure for research opportunities at the intermediate scale not previously available for university research in Canada. Between 2003 and 2010, the OSTRF has reported on 32 separate research projects. As a result of these projects, 16 students have graduated and are currently working for oil sands companies, regulators, oil sands industry consultants or have continued their graduate studies at the PhD level.

The need to enhance tailings management is now even more important than when OSTRF was established in 2003. Due to what it perceived to be limited progress in reclamation efforts, the Energy Resources Conservation Board (ERCB) — via Directive 74 — recently began requiring that the industry improve tailings (fines) management and its documentation of the progress of dealing with tailings on each mine site.

The initial OSTRF research program focused on improving the understanding and management of the massive inventories of mature fine tailings (MFT) or “legacy tailings.” The greatest research emphasis was on the geo­technical and chemical behaviour of engineered tailings and the management and treatment of process affected water (PAW).

The current research projects are topical given the media’s attention on the environment and the emphasis of the ERCB’s Directive 74. While research efforts on the quality and treatment of water have increased, an appreciation of the necessity to understand and deal with the legacy tailings remains. This focus on water relates to its characterization (naphthenic acids [NA]), its treatment with coke and rapid removal of water from the total tailings stream.

In 2009, a NA fluorescence sensor was developed by an OSTRF research team. The device is a bench scale instrument with a detection limit of less than 4 mg/L of NAs in PAW. The technology offers a cost-effective, compact, non-invasive and continuous water quality monitoring tool that can detect, characterize and track changes of NAs in PAW.

Reducing or eliminating the formation of new MFT during conventional tailings deposition poses a challenge due to the segregating nature of the total tailings stream. Additionally, the use of hydro-cyclones to generate dewatered tailings sand results in water and fines discharging as cyclone overflow into a tailings pond where additional MFT is formed.

Using the principles of cross-flow filtration, a novel, in-line tailings dewatering technology is currently under development by an OSTRF research team to address these issues. The in-line dewatering process aims to rapidly dewater the total tailings en route to the disposal area while ensuring the released water is low in fines (for immediate recycle to extraction) leading to deposition of a dewatered total tailings (containing sand and fines) as a non segregating mix. Benefits of achieving this include the prevention of new MFT inventory, the rapid release of heated water — thus reducing energy demand and greenhouse gas (GHG) release — and the potential to deposit total tailings without requiring water retention containment dykes.

The next phase of research to be undertaken by OSTRF researchers will continue efforts towards reducing the volume of tailings and their stabilization in a timely manner for reclamation. Research projects will include:

• Reduction or elimination of volatile organic carbons and GHG from tailings ponds.

• Further development and scaling of the novel in-line tailings

dewatering system and alternative methods to release water from the MFT inventory.

• Treatment technologies for re-use of PAW in utilities and for upgrading while also developing quality standards for eventual discharge of PAW off lease.

• Stabilization and capping of soft tailings deposits in preparation for reclamation, including methods of dewatering the upper surface of soft tailing to enhance its strength.

In an era of heightened environmental awareness and increasingly stringent regulations, the OSTRF is well poised to develop novel approaches for tailings management and to educate and train the future leaders of the industry.


Dave SegoNicholas Beier
Dave Sego (left) is the principal investigator of the Oil Sands Tailings Research Facility and a professor emeritus in the Department of Civil & Environmental Engineering at the University of Alberta. Nicholas Beier works with Dr. Sego at the OSTRF on developing novel approaches to tailings management.

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