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

在阿尔伯塔东北部，在从露天开采的油砂矿中提取沥青的过程中产生了大量的流体细粒尾矿（FFT）。FFT由水、细粘土、环烷酸（NAs）、残余沥青和其它未回收的烃组成。FFT需要几十年的时间来处理尾矿池。因此，不断增长的库存迫使运营商寻求替代尾矿管理策略。采出矿井中的底坑湖（EPL）是潜在的选择之一，其FFT低于水帽。预期EPLs将缓慢发展成为自我维持的水生生态系统。与EPLs的潜在问题可能包括潜在关注的成分（COPCs）从FFT到上覆盖水的移动，导致可能的毒性的持续来源。因此，已经进行了研究，以解决这些问题，并确定可行性的EPLs作为一个填海战略。Graymont进行的初步试验表明：1）向FFT中添加750至1500 mg-CaO/kg-FFT范围内的石灰可改善FFT脱水并促进残余沥青的释放; 2）向油砂工艺影响水（OSPW）中添加石灰可在pH 12时诱导环烷酸钙沉淀形成。这些初步的研究结果可以通过进一步研究石灰处理如何减轻COPC通量在EPLs的FFT水帽界面。这两个问题都是相关的及时发展ofEPLs在油砂industry.In这项研究中，石灰将测试其能力，以提高FFT脱水和NA去除在实验室规模的批量实验代表的EPL。本研究的目的是评估在EPLs中使用石灰作为预处理步骤的可行性，以实现高效和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.