Electrokinetic sedimentation of mature oil sand mine tailings

Raquibul Alam, Julie Q. Shang, Shriful Islam

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Geoenvironmental Engineering

ABSTRACT: etic sedimentation of mature oil sand mine tailings Raquibul Alam, Julie Q. Shang and Shriful Islam Department of Civil and Environmental Engineering - Western University, London, ON, Canada ABSTRACT Oil sands mines generate tailings during the extraction process, which are a mixture of water, clay, sand and residual bitumen. When the tailings are released to tailings ponds, the coarse solids settle quickly, whereas fine solids containing clay minerals, namely Mature Fine Tailings (MFT), remain suspended for years, even decades. A study is carried out to assess the suitability of Electrokinetic (EK) sedimentation to accelerate sedimentation of MFT. A series of laboratory-scale column experiments are carried out to examine the effects of electrophoresis during settling processes. The investigation focuses on the effects of EK sedimentation as related to the initial solid concentration of the tailings suspension, applied electric field intensity, water pH, and the use of an optimized coagulant FeCl3. The research has shown that EK is a viable technology for accelerating sedimentation of suspended solids in fine oil sand tailings in terms of reducing the overall sedimentation time and increasing the final solid concentration. RÉSUMÉ Les mines de sables bitumineux génèrent des résidus au cours du processus d'extraction, qui sont un mélange d' eau, d'argile, de sable, et de bitume résiduel. Quand les résidus sont laissés dans les basin de decantation, les particules larges se déposent rapidement mais les particules fines contenant des minéraux argileux; appelé les résidus fins mûrs (RFM), restent suspendues pendant des années, mêmes des décennies. Une série d'expériences pour examiner les effets de l'électrophorèse pendant le processus de décan3. Les résultats de la recherche montré que la sedimentation électrocinétique réduit le temps global de sedimentation et augment la concentration de solides finale. Par consequent, la sedimentation électrocinétique est une technologie viable pour accélérer la sédimentation des particules fines dans les résidus de sables bitumineux. 1 INTRODUCTION Canadian oil sands cover an area of about 142,000 square kilometres (km2) (NEB, 2004).Oil sand tailings, the end products of the oil sand mining operation, are pumped into large tailings ponds. The coarse solids, mostly sands, settle down quickly. However, fine solids, remain suspended in tailings ponds, which take 2 to 3 years or longer to consolidate and are known as mature fine tailings (MFT) (Johnson et al., 1993). The MFT are a mixture of residual bitumen, sand, silt, and clay particles.Due to the poor water release ability, low permeability and low strength of the MFT, dewatering under natural conditions is not realistic (Mikula et al., 1996). Currently more than 170 km2 covered by tailings ponds, and expected to occupy an area of 250 km2 by 2020, (Government of Alberta, 2012), which causes serious environmental concerns, such as impacts on public health, land use, water supply and air quality (Farkish, 2013). Consequently, various regulations and requirements have been implemented for the tailings operations associated with oil sands mining in order to preserve the environment (ERCB, 2009).The main objective in oil sands tailings management is to thicken and consolidate the MFT to reduce the dedicated disposal areas (DDAS) (Farkish, 2013).Several studies have been done on these aspects (Sworska et al, 2000; Guo and Shang, 2014) The tailings thickening is a dewatering process for slurries with low solid content, in which the first phase is sedimentation of suspended fine solids. Flocculants are commonly used in thickening processes to increase the settling rate and reduce the thickener size (Jewell and Fourie, 1999). Flocculants are organic, high molecular weight synthetics or natural polymers that help to enhance the settling rates of suspended solids by adsorbing onto solid particles, forming flocs (Barbour and Wilson, 1993). The centrifuging technique is also an option of thickening to separate particles from liquid, which can produce cake with up to 60 wt% solids (OSRIN Report, 2010).Filtration is also one of the basic methods by using pressure or a vacuum to separate coarse and medium particles from water(OSRIN Report, 2010). Electrokinetic thickening is a potential option to enhance the thickening process of fine oil sand tailings. Electrokinetics has been studied extensively in geotechnical engineering applications (e.g. Fourie et al., 2007, Mohamedelhassan, 2008; Rittirong et al., 2008,

RÉSUMÉ: rokinetic sedimentation of mature oil sand mine tailings Raquibul Alam, Julie Q. Shang and Shriful Islam Department of Civil and Environmental Engineering - Western University, London, ON, Canada ABSTRACT Oil sands mines generate tailings during the extraction process, which are a mixture of water, clay, sand and residual bitumen. When the tailings are released to tailings ponds, the coarse solids settle quickly, whereas fine solids containing clay minerals, namely Mature Fine Tailings (MFT), remain suspended for years, even decades. A study is carried out to assess the suitability of Electrokinetic (EK) sedimentation to accelerate sedimentation of MFT. A series of laboratory-scale column experiments are carried out to examine the effects of electrophoresis during settling processes. The investigation focuses on the effects of EK sedimentation as related to the initial solid concentration of the tailings suspension, applied electric field intensity, water pH, and the use of an optimized coagulant FeCl3. The research has shown that EK is a viable technology for accelerating sedimentation of suspended solids in fine oil sand tailings in terms of reducing the overall sedimentation time and increasing the final solid concentration. RÉSUMÉ Les mines de sables bitumineux génèrent des résidus au cours du processus d'extraction, qui sont un mélange d' eau, d'argile, de sable, et de bitume résiduel. Quand les résidus sont laissés dans les basin de decantation, les particules larges se déposent rapidement mais les particules fines contenant des minéraux argileux; appelé les résidus fins mûrs (RFM), restent suspendues pendant des années, mêmes des décennies. Une série d'expériences pour examiner les effets de l'électrophorèse pendant le processus de décan

Access this article:
Canadian Geotechnical Society members can access to this article, along with all other Canadian Geotechnical Conference proceedings, in the Member Area. Conference proceedings are also available in many libraries.

Cite this article:
Raquibul Alam; Julie Q. Shang; Shriful Islam (2014) Electrokinetic sedimentation of mature oil sand mine tailings in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper213,author = Raquibul Alam; Julie Q. Shang; Shriful Islam,title = Electrokinetic sedimentation of mature oil sand mine tailings,year = 2014}