Maintaining Permeability for Continuous Mature Fine Tailings Dewatering

油砂尾矿一旦形成所谓的“成熟细尾矿”（MFT），其脱水速度极其缓慢。累计MFT容量超过8亿立方米，并在不断增加。在过去的几十年里，该行业开发了许多脱水技术（复合尾矿、浓缩尾矿、在线增稠/薄举、离心、过滤）来加快油砂尾矿的固液分离。然而，处理效果普遍不理想，尾矿不能通过机械手段脱水超过~55 wt%的固体，使得>=75 wt%的固体（回收所需）的目标似乎无法实现。我们最近的研究结果表明，油砂尾矿的脱水困难可能是由于MFT中残留的沥青，而不是由于尾矿中的细固体体积小。我们的研究结果表明，在6 bar的压力下，使用50 g/t的聚丙烯酰胺（PAM）， 35 wt%的细高岭石（d50 = 4µm）的水泥浆可以很容易地过滤到~70 wt%的固体。然而，在掺入3 wt%的残余沥青后，高岭石浆料在1 ~ 1500 g/t PAM下只能过滤到~60 wt%的固体，表现得像MFT。基于这些结果，我们提出了一个问题：通常使用的PAM絮凝剂在处理残余沥青方面是否最好？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，以减轻残余沥青的有害影响。研究技术将包括：1)罐试验，以评估潜在的沥青粘合剂与从MFT分离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粘结剂、细固体与沥青粘结剂的结合强度；3)对经沥青粘结剂处理后的MFT进行压滤试验，观察脱水效果和获得的饼%固含量；4)利用显微计算机断层扫描和低温扫描电镜研究处理后滤饼的孔隙结构，探讨脱水性能变差和改善的原因。

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.