Innovative and eco-friendly techniques of waste rocks management

在过去几十年中，全球露天采矿的发展相应地应对了困难的经济环境以及一些战略和贵金属的高价格。这导致人们对许多高吨位/低品位类型矿床的兴趣增加，特别是在加拿大。该等采矿作业产生大量占地面积及大量废石，一般储存于矿场表面。一些地下矿山也面临着类似的问题。由于这些材料往往含有硫化物，粒度分布粗而宽（微米至米制尺寸），而且对水和氧气的渗透性很高，它们可能成为或多或少受污染的矿井排水的来源，有时还产生很高的酸。这种现象在世界范围内被称为酸性岩石排水（ARD）。硫化物反应导致排放沃茨中酸溶性金属/类金属、硫酸盐和酸性的释放。氧在废石堆中的扩散受材料性质的影响。控制ARD的现有技术都在废物处置过程中实施（屋顶密封、与尾矿共处置、引水等），和/或在矿山关闭和复垦后进行处置，因此需要安装复杂但昂贵的覆盖技术，然后进行适当的重新植被。本项目旨在通过调查新的创新和生态友好方法的不同步骤来应对废石管理方面的挑战。这种方法必须在废石开采后立即应用于上游，它集成了优化的废石爆破、再处理和/或价值评估。该项目的主要假设是：（一）废石中的硫化物主要与粗颗粒有关，没有明显暴露于风化条件，（二）矿物风化主要发生在细颗粒（尺寸有待进一步确定）中，因为这些颗粒的暴露表面积很大。了解到研究更创新和可持续的废石管理技术的重要需求，研究计划的主要目标如下：1-评估爆破模式和适应废物提取和管理;2-建议一种严格的取样技术，这是最佳的废石; 3-精细表征（物理、化学和矿物学性质）和实施基于自动矿物学、显微层析成像等的新的预测工具; 4-通过重力分离和/或粗/细黄铁矿浮选，优化有效的除砂工艺和桑迪部分的脱硫;5-集体方法的技术/经济可行性，包括粗粒部分（用于混凝土、路面等）的重新估价的可行性

During the last decades, the development of open pit mining worldwide has responded accordingly to a difficult economic context as well as high prices for some strategic and precious metals. This has led to increased interest in many high tonnage/low-grade type deposits, particularly in Canada. Such mining operations generate large footprint and significant amount of waste rocks to be stored generally at the surface of mine site. Some underground mine are also facing similar problems. Since these materials are often sulphide bearing and have coarse and wide particle-size distributions (micrometric to metric sizes) as well as high permeability to water and oxygen, they are likely to be a source of more or less contaminated mine drainages, sometimes highly acid generating. The phenomenon is worldwide known as acid rock drainage (ARD). Sulfide reaction lead to the releases of acid-soluble metals/metalloids, sulfates, and acidity within the drainage waters. The oxygen diffusion within waste rock piles is favoured by the material properties. The available techniques to control ARD are all implemented during waste disposal (roof sealing, co-disposal with tailings, water diversion, etc.), and/or after disposal upon mine site closure and reclamation, thus necessitating the installation of complex but costly cover techniques followed by appropriate revegetalisation.The present project aims to tackle challenges surrounding waste rocks management through the investigation of different steps of a new, innovative, and eco-friendly approach. This approach, which has to be applied upstream immediately after waste rock extraction, integrates optimized waste blasting, reprocessing, and/or valorisation. The main hypotheses of the project are that: (i) sulphides within waste rocks are mainly associated with coarse particles and are not significantly exposed to weathering conditions, and (ii) mineral weathering occurs primarily in the fine fraction (size to be further defined), due to the high available exposed surface area of these particles. Knowing the important needs of research for more innovative and sustainable waste rock management techniques, the main objectives defined for the research program are the following:1- Evaluation of blasting pattern and adaptation for waste extraction and management;2- Suggestion of a rigorous sampling technique which is optimal for waste rocks;3- Fine characterization (physical, chemical and mineralogical properties) and implementation of new predictive tools based on automated mineralogy, microtomography, etc;4- Optimization of an efficient desanding process and desulphurization of the sandy fraction through gravity separation and/or coarse/fine pyrite flotation;5- Technical/economical feasibility of the collective approach, including feasibility of revalorization of the coarse fraction (for use in concrete, road pavement, etc.)