Innovative and eco-friendly techniques of waste rocks management

在过去几十年中，世界各地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金属和贵金属的高价格。这导致对许多高吨位/低品位类型矿藏的兴趣增加，特别是在加拿大。这种采矿作业产生了很大的占地面积和大量的废石，通常要储存在矿场的表面。一些地下矿山也面临着类似的问题。由于这些材料通常含有硫化物，具有粗而宽的粒度分布(微米到米级)以及对水和氧气的高渗透性，它们很可能是或多或少受到污染的矿山废水的来源，有时产生高度的酸。这种现象在世界范围内被称为酸性岩石排水(ARD)。硫化物反应导致废水中酸溶金属/类金属、硫酸盐和酸度的释放。材料性质有利于氧在废石堆中的扩散。现有的控制ARD的技术都是在废物处理(屋顶密封、与尾矿共处理、引水等)过程中实施的，和/或在矿场关闭和复垦后处置，因此需要安装复杂但昂贵的覆盖技术，然后进行适当的植被重建。本项目旨在通过调查一种新的、创新的和环保的方法的不同步骤来应对围绕废石管理的挑战。这种方法必须在废石开采后立即应用于上游，它集成了优化的废物爆破、后处理和/或有价化。该项目的主要假设是：(I)废岩中的硫化物主要与粗颗粒有关，并不显著地暴露于风化条件下，以及(Ii)矿物风化主要发生在细粒(粒度有待进一步定义)中，这是由于这些颗粒的可用裸露表面积很高。了解到研究对更具创新性和可持续的废石管理技术的重要需求，为研究方案确定的主要目标如下：1-评价爆破方式和废物提取和管理的适应性；2-建议最适合废石的严格取样技术；3-精细表征(物理、化学和矿物学特性)和采用基于自动矿物学、显微层析成像等的新预测工具；4-通过重力分离和/或粗/细黄铁矿浮选优化有效的除砂过程和砂组分的脱硫；5-集体方法的技术/经济可行性，包括重新估价粗组分(用于混凝土、路面等)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.)