【作者】 杨保华；

【导师】 吴爱祥；

【作者基本信息】 中南大学 ， 安全技术及工程， 2010， 博士

【摘要】 微生物堆浸体系是一个复杂的动态体系,在浸出过程中散体介质的孔隙结构不断发生演化,而孔隙结构的演化又会影响到介质的渗透性能,进一步对溶质运移、热量传递、动量传递等过程产生影响,最终影响到浸出速率和浸出率。由此可见,散体孔隙结构在整个浸出体系中处于核心地位,研究其结构特征、演化规律以及对堆体渗透性能的影响具有重要意义。论文通过现场调查、室内试验、理论分析、数值模拟相结合的方法,以细观孔隙结构参数与宏观渗透性能的相关性为突破口,引进先进的X光CT技术及数字图像处理技术,进行单级散体和级配散体孔隙结构参数量化分析,展开微生物浸出过程中孔隙结构演化规律和机理研究,并在此基础上实现散体介质细观渗流的数值模拟,在很大程度上丰富了溶浸采矿基础理论体系。论文完成的主要工作如下：(1)以堆浸散体介质多尺度孔隙结构理论研究为出发点,系统分析了堆浸散体孔隙结构的多尺度特性,细观孔隙结构表征参数及其与宏观渗透性能的关联。(2)发展了基于X光CT技术研究堆浸散体孔隙结构特征的新方法,提出了堆浸散体孔隙结构三维重构技术路线,基于体绘制算法,利用MATLAB编程实现了矿岩散体孔隙结构的三维重构。(3)率先完成了多组单级散体试样和级配散体试样的CT扫描试验,结合图像处理技术实现了孔隙结构参数的定量化分析,探明了散体介质孔隙率、孔隙尺寸分布与粒径的关系,并应用分形理论分析了散体介质颗粒分维数、孔隙分维数以及颗粒—孔隙界面分维数与颗粒尺寸、孔隙率及渗透系数的相关性。(4)首次结合CT技术完成了微生物堆浸矿岩散体孔隙演化试验,提出了孔隙拓扑率概念,并建立了考虑孔隙连通性变化的渗透率修正公式,在此基础上详细分析了堆浸过程中散体的孔隙率、孔隙尺寸、孔隙连通性以及渗透率的时间和空间变异性,探明了微生物堆浸过程中孔隙演化规律及其对渗透性能的影响。(5)利用散体结构力学、渗流力学、物理化学以及微生物学等理论,首次从多尺度(微观、细观、宏观)和多过程(物理过程、化学过程、生物过程)分析了影响孔隙结构参数变化的主要因素及其影响机制,探明了微生物堆浸过程中矿岩散体孔隙演化机理。(6)将数字图像处理技术(DIP)和有限元(FEM)技术进行耦合,基于散体孔隙CT图像直接构建孔隙有限元模型,把渗流数值模拟的物理模型从理想模型提升至真实模型,并率先利用COMSOL Multiphysics数值模拟软件进行了堆浸散体中细观渗流的数值模拟,探明了孔隙细观渗流特性。更多还原

【Abstract】 Bioleaching system is a complex dynamic sytem. During leaching process, the pore strucuture of granular media evolves continuously, which influences the permeability of the media and then affects the processes of mass transport, heat transmission and momentum transfer. As a result, the heap leaching rate and recovery ratio are affected. Since the pore structure of granular media is very crucial for the whole heap leaching system, so it is very important to study the characteristics of pore structure, evolvement rules and its effects on the permeability of the heap.With the methods of field investigation, indoor test, theoretical analysis, and numerical simulation, begining with the relationship between mesoscale pore structure parameters and macro permeability, by introducing advanced X-ray computerized tomography (CT) and digital image process technology, the quantification of pore structures of single grade granular ore samples and graded granular ore samples were conducted. Furthermore, the evolvement rules and mechanisms of pore structure of granular ore media during heap leaching were studied. At last, the simulation of meso seepage flow of granular media was realized. The research achievements enriched the basic theoretical system of solution mining.The main works completed are as follows:(1) Starting from the theoretical research of multi-scales pore structure of granular ore media, the characteristics of granular ore media, the representative parameters of mesoscale pore structure and its relationship with macro permeabiltiy were systematically analyzed.(2) The new method based on X-ray CT technology was developed for studying the characteristics of granular ore media. A technical route for the three dimensional reconstruction of granular ore media’s pore structure was put forward. Using volume ploting algorithm, the reconstruction of pore structure was realized with MATLAB programming.(3) For the first time, several groups of single grade granular ore samples and graded granular ore samples were scanned by X-ray CT. By using image process technologies, the pore structure parameters of all samples were quantified. The relationships between porosity, pore size distribution and particle size were explored. Moreover, based on fractal theory, the fractal dimensions of solid matrix, pore space and matrix-pore interface of each sample were measured and the correlations of the three fractal dimensions with particle size, porosity, and seepage coefficient were analyzed.(4) The pore evolvement experiment of granular ore media during bacteria column leaching was carried out by intergrating CT technology firstly. The concept of pore topological ratio was put forward and the permeability formula was improved by considering the change of pore connectivity. Based on this, the temporal and spatial variabilities of porosity, pore size distribution, pore connectivity and permeability along the height of column were analyzed in details. Thus the pore evolvement rules and its influence on permeability were disclosed.(5) Based on granular structural mechanics, seepage dynamics, physical chemistry, and microbiology, the evolvement mechanisms of pore structure of granular ore media under the action of solution were analyzed from multi-scale (micro-, meso-and macro-) and multi-process (physical, chemical and bacterial process) firstly.(6) Coupled with digital image processing technoloty (DIP) and finite element method (FEM), the finite element model of pore network was build directly based on CT image, realized the transformation of physical model for seepage simulation from ideal model to realistic model. For the first time, the mesoscale fluid flow in pore network of granular ore media was simulated with COMSOL Multiphysics and the characteristics of pore scale fluid flow was disclosed.更多还原