Maintaining Permeability for Continuous Mature Fine Tailings Dewatering

油砂尾矿一旦形成所谓的“成熟细粒尾矿”（MFT），其沉降速度就非常缓慢。累计MFT量超过8亿立方米，并在不断增加。在过去的几十年里，工业界已经开发了许多脱水技术，（复合尾矿、浓缩尾矿、在线浓缩/薄提升、离心、过滤）来加速油砂尾矿的固液分离。然而，处理的性能通常不令人满意，并且通过机械手段不能使尾矿脱水超过~ 55wt%固体，使得固体含量>= 75wt%（回收所需）的目标似乎无法实现。我们最近的结果表明，油砂尾矿脱水的困难可归因于MFT中残留的沥青，而不是尾矿中细小固体的小尺寸。我们的研究结果表明，在6 bar压力下，使用50 g/t聚丙烯酰胺（PAM），35 wt%细高岭石（d50 = 4 µm）的水性浆料可以很容易地过滤到约70 wt%的固体。然而，当PAM用量大于1,500 g/t时，高岭土浆体在掺加3%（质量分数）的残余沥青后，只能过滤到约60%（质量分数）的固体，表现出类似于MFT的性能。在建议的项目中，我们将回答这个问题，并确定适当的粘合剂，以减轻残余沥青的不利影响。研究方法包括：1）罐式试验，评价沥青胶结料与从MFT中分离出的残余沥青的相互作用; 2）等温滴定量热法（ITC）研究残余沥青与沥青胶结料之间以及细粒固体与沥青胶结料之间的粘结强度; 3）对用沥青粘合剂处理后的MFT进行压滤试验，以观察脱水效果和所获得的滤饼%固体含量;（4）利用微型计算机断层扫描仪和低温扫描电子显微镜对处理后滤饼的孔结构进行了研究，探讨了脱水性能变差和提高的原因。

Oil sands tailings dewater extremely slowly once they form the so-called "mature fine tailings" (MFT). Theaccumulated MFT volume is over 800 million cubic meters and counting. Over the last few decades theindustry has developed a number of dewatering techniques (composite tailings, thickened tailings, in-linethickening/thin lift, centrifugation, filtration) to speed up the solid-liquid separation of the oil sands tailings.However, the performance of treatment is generally unsatisfactory, and the tailings could not be dewateredbeyond ~55 wt% solids by mechanical means, making the target of >=75 wt% solids (required for reclamation)seem un-achievable.Our recent results show that the difficulty of dewatering the oil sands tailings could be attributed to theresidual bitumen in MFT rather than the small size of the fine solids in the tailings. Our results show that anaqueous slurry of 35 wt% fine kaolinite (d50 = 4 µm) could easily filter to ~70 wt% solids using 50 g/tpolyacrylamide (PAM) under 6 bar pressure. However, after blending in 3 wt% of the residual bitumen, thekaolinite slurry could only be filtered to ~60 wt% solids at >1,500 g/t PAM, behaving like MFT.Based on these results, we ask the question: are the typically used PAM flocculants the best in dealing withthe residual bitumen? In the proposed project, we will answer this question and identify appropriate binders toalleviate the detrimental effect of the residual bitumen. The research techniques will include: 1) jar tests toevaluate the interaction of potential bitumen binders with residual bitumen isolated from MFT; 2) isothermaltitration calorimetric (ITC) study to investigate the binding strength between residual bitumen and bitumenbinders, and between fine solids and bitumen binders; 3) filter press tests of the MFT after treatment by thebitumen binders to observe the dewatering effect and the achieved cake % solids content; 4) micro computedtomography and cryogenic scanning electron microscopy to study the pore structures of the filter cake after thetreatment, and to investigate the reasons for the poor and improved dewatering performances.