Assessing the feasibility of using lime to mitigate chemical flux in oil sands end pit lakes

在阿尔伯塔省东北部，从地面开采的油砂矿石中提取沥青时产生了大量的流体细尾矿（FFT）。FFT由水、细粘土、环烷酸（NAs）、残余沥青和其他未回收的碳氢化合物组成。FFT需要几十年才能在尾矿池中脱水。因此，不断增长的库存迫使运营商寻求替代的尾矿管理策略。在采空区水帽下设置fft的端坑湖（epl）是一种潜在的选择。预计epl将慢慢发展成为自给自足的水生生态系统。epl的潜在问题可能包括潜在关注成分（COPCs）从FFT转移到上覆的封顶水中，从而形成可能的持续毒性来源。因此，已进行研究以解决这些问题，并确定将环境保护规划作为一项填海策略的可行性。加拿大西部格雷蒙特公司是石灰和石灰石产品供应的新兴全球领导者。Graymont进行的初步试验表明：1)在750 ~ 1500mg-CaO/kg-FFT范围内添加石灰可改善FFT脱水，促进残余沥青的释放；2)在pH为12的油砂工艺影响水（OSPW）中添加石灰可诱导形成环烷酸钙沉淀。这些初步发现可以通过进一步研究石灰处理如何减轻epl中fft -水帽界面上的COPC通量来利用。这两个问题都关系到油砂行业中fepl的及时发展。在这项研究中，石灰将在EPL的实验室规模批量实验中测试其增强FFT脱水和NA去除的能力。摘要本研究的目的是探讨石灰在油砂尾矿回收中作为预处理步骤的可行性，以实现高效经济的油砂尾矿回收。

In northeastern Alberta, large volumes of fluid fine tailings (FFT) are produced during bitumen extraction fromsurface-mined oil sands ore. FFT is comprised of water, fine clays, naphthenic acids (NAs), residual bitumenand other unrecovered hydrocarbons. FFT takes decades to dewater in tailings ponds. Hence, the growinginventory compels operators to seek alternative tailings management strategies. End pit lakes (EPLs) with FFTbelow a water cap in mined out pits are one of the potential options. The expectation is that EPLs will slowlydevelop into self-sustaining aquatic ecosystems. Potential issues with EPLs may include movement ofconstituents of potential concern (COPCs) from the FFT into the overlying cap water contributing to on-goingsources of possible toxicity. Thus, research has been undertaken to resolve these issues and determine thefeasibility of EPLs as a reclamation strategy.Graymont Western Canada Inc. is an emerging global leader in the supply of lime and limestone products.Graymont has conducted preliminary tests showing that 1) lime addition to FFT in the range of 750 to 1500mg-CaO/kg-FFT improves FFT dewatering and facilitates the release of residual bitumen, and 2) lime additionto oil sands process-affected water (OSPW) induces calcium naphthenate precipitate formation at pH 12. Thesepreliminary findings can be leveraged by further investigating how lime treatment can mitigate COPC fluxacross the FFT-water cap interface in EPLs. Both of these issues are of relevance for the timely development ofEPLs in the oil sands industry.In this study, lime will be tested for its ability to enhance FFT dewatering and NA removal in lab-scale batchexperiments representative of an EPL. The purpose of this study to assess the feasibility of using lime as apre-treatment step in EPLs for efficient and economical oil sands tailings reclamation.