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)，脱水速度极慢。MFT的累积体积超过了8亿立方米，而且还在不断增加。在过去的几十年里，油砂行业开发了许多脱水技术(复合尾矿、浓缩尾矿、在线滴滤/稀提法、离心法、过滤)来加速油砂尾矿的固液分离。然而，处理性能通常不能令人满意，尾矿的机械脱水不能超过55wt%的固体，这使得回收所需的固体=75wt%的目标似乎无法实现。我们最近的研究结果表明，油砂尾矿脱水的困难可能是由于MFT中含有少量的双沥青，而不是尾矿中细小的固体颗粒。结果表明，在6bar压力下，加入50g/t的聚丙烯酰胺(PAM)，35wt%的细粒高岭土(D50=4µm)的水泥浆可以很容易地过滤到~70wt%的固体。然而，加入3wt%的残留沥青后，高岭土浆液在1500g/t PAM时只能过滤到~60wt%的固体含量，表现出MFT的表现。基于这些结果，我们提出了一个问题：在处理残留沥青方面，典型的PAM絮凝剂是不是最好的？在拟议的项目中，我们将回答这个问题，并寻找合适的粘结剂，以减轻残留沥青的不利影响。研究方法包括：1)用烧杯试验评价潜在的沥青结合料与从MFT分离出来的残余沥青的相互作用；2)用等温滴定法(ITC)研究残余沥青与沥青结合料、细颗粒与沥青结合料之间的结合强度；3)对MFT经沥青结合料处理后的滤饼进行压滤机试验，观察脱水效果以及所获得的滤饼%固形物含量；4)用显微计算机断层扫描和低温扫描电子显微镜研究处理后滤饼的孔结构，并探讨脱水性能差和改善的原因。

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.