Quantifying the impact of mineralogical heterogeneity on reactive transport modeling of CO_(2)+O_(2) in-situ leaching of uranium

CO_(2)+O_(2) in-situ leaching(ISL)of sandstonetype uranium ore represents the third generation of solution mining in China.In this study,reactive transport modeling of the interaction between hydrodynamic and geochemical reactions is performed to enable better prediction and regulation of the CO_(2)+O_(2) in-situ leaching process of uranium.Geochemical reactions between mining solutions and rock,and the kinetic uranium dissolution controlled by O_(2)(aq)and bicarbonate(HCO_(3)-)are considered in the CO_(2)+O_(2) ISL reactive transport model of a typical sandstone-hosted uranium ore deposit in northern China.The reactive leaching of uranium is most sensitive to the spatial distribution of the mineralogical properties of the uranium deposit.Stochastic geostatistical models are used to represent the uncertainty on the spatial distribution of mineral grades.A Monte Carlo analysis was also performed to simulate the uranium production variability over an entire set of geostatistical realizations.The ISL stochastic simulation performed with the selected geostatistical realizations approximates the uranium production variability well.The simulation results of the ISL reactive transport model show that the extent of the uranium plume is highly dependent on mineralogical heterogeneity.The uncertainty analysis suggests the effect of uranium grade heterogeneity was found to be important to improve the accurate capture of the uncertainty.This study provides guidance for the accurate simulation and dynamic regulation of the CO_(2)+O_(2) leaching process of uranium at the scale of large mining areas.

Factors influencing in-situ leaching of uranium mining in a sandstone deposit in Shihongtan, Northwest China

The Shihongtan uranium deposit in northwest China is a sandstone-type deposit suitable for alkaline in-situ leaching exploitation of uranium. Alkaline leaching tends to result in CaCO3 precipitation there by affecting the porosity of the ore-bearing aquifer. CaCO3 deposits can also block pumping and injection holes if the formulation parameters of the leaching solution are not well controlled. However, controlling these parameters to operate the in-situ leaching process is challenging. Our study demonstrates that the dissolved uranium concentration in the leaching solution increases as HCO3-concentration increases. Therefore, the most suitable HCO3-concentration to use as leaching solution is defined by the boundary value of the HCO3-concentration that controls CaCO3 dissolution-precipitation. That is, the dissolution and precipitation of calcite is closely related to pH, Ca2+ and HCO3-concentration. The pH and Ca2+ concentration are the main factors limiting HCO3-concentration in the leaching solution. The higher the pH and Ca2+ concentration, the lower the boundary value of HCO3-concentration, and therefore the more unfavorable to in-situ leaching of uranium.

Improved uranium leaching efficiency from low-permeability sandstone using low-frequency vibration in the CO_(2)+O_(2) leaching process

Extraction of uranium from low-permeability sandstone is a long-standing challenge in mining.The improvement of sandstone permeability has therefore become a key research focus to improve the uranium leaching effect.To address the low-permeability problem and corresponding leaching limits,leaching experiments are performed using newly developed equipment that could apply low-frequency vibration to the sandstone samples.The test results indicate that low-frequency vibration significantly improves the uranium leaching performance and permeability of the sandstone samples.The leaching effect of low-frequency vibration treatment is approximately nine times more effective than ultrasonic vibration treatment,whereas the concentration of uranium ions generated without vibration treatment is not detectable.Mathematical model that considers the combined action of physico-mechanical vibration and chemical erosion is established to describe the effect of low-frequency vibration on the permeability.The calculated results are in good agreement with the tested permeability values.This study thus offers a new method to effectively leach more uranium from low-permeability sandstone using CO_(2)+O_(2)and provides an insight into the impact of low-frequency vibration on the uranium leaching process.

Assessment of the Greenhouse Gas Footprint and Environmental Impact of CO_(2)and O_(2)in situ Uranium Leaching

Under the new development philosophy of carbon peaking and carbon neutrality,CO_(2)and O_(2)in situ leaching(ISL)has been identified as a promising technique for uranium mining in China,not only because it solves carbon dioxide utilization and sequestration,but it also alleviates the environmental burden.However,significant challenges exist in assessment of CO_(2)footprint and water-rock interactions,due to complex geochemical processes.Herein this study conducts a three-dimensional,multicomponent reactive transport model(RTM)of a field-scale CO_(2)and O_(2)ISL process at a typical sandstone-hosted uranium deposit in Songliao Basin,China.Numerical simulations are performed to provide new insight into quantitative interpretation of the greenhouse gas(CO_(2))footprint and environmental impact(SO_(4)^(2–))of the CO_(2)and O_(2)ISL,considering the potential chemical reaction network for uranium recovery at the field scale.RTM results demonstrate that the fate of the CO_(2)could be summarized as injected CO_(2)dissolution,dissolved CO_(2)mineralization and storage of CO_(2)as a gas phase during the CO_(2)and O_(2)ISL process.Furthermore,compared to acid ISL,CO_(2)and O_(2)ISL has a potentially smaller environmental footprint,with 20%of SO_(4)^(2–)concentration in the aquifer.The findings improve our fundamental understanding of carbon utilization in a long-term CO_(2)and O_(2)ISL system and provide important environmental implications when considering complex geochemical processes.

Development and Prospect of China Uranium Mining and Metallurgy

The development of industry of uranium mining and metallurgy in China has been reviewed generally,emphasizing on investigation approaches and application levels of uranium mining technologies such as in-situ leaching,heap leaching,stope leaching:on the basis of analysis on status of uranium mining and metallurgy and problems existed,also considering the specific features of deposit resources,the development orientation of uranium mining and metallurgy in China is pointed out.The industry of China uranium mining and metallurgy is faced to new opportunity of development and challenge in 21st century,the only way to realize sustainable development of uranium mining and metallurgy and harmonious development between economy and environment is to develop new technology on mining,ore beneficiation and metallurgy,increase the utilization level of uranium resources,low down impact on environment caused by mining and metallurgy.

基于机器学习方法预测地浸过程中铀浸出金属量的变化

在地浸采铀过程中,准确预测铀浸出金属量具有重要意义。使用多元线性回归、多层感知机(MLP)和随机森林(RF)多种机器学习方法分别建立预测模型。结果表明:1)相比于传统的多元线性回归算法,MLP和RF两种方法能够得到预测性能更好的模型。2)多层感知机(MLP)模型在预测铀浸出金属量变化的上性能表现最佳(R 2=0.91)。3)在相同的预测精度下,RF模型比MLP模型耗时更短,超参数设置更加简单。4)在以总流量和每平米铀量为铀浸出金属量的关键因素进行分析时,总流量对铀浸出金属量的权重占比为81.6%。

内蒙古某地浸铀矿山地质-开采模型对比研究与剩余资源量评价

为了促进地浸铀资源的充分利用,统计分析了内蒙古某地浸铀矿山研究区内的矿段厚度、过滤器长度和矿层有效厚度,采用三维矿业软件构建矿体地质模型与开采模型,通过三维实体的可视化对比,精准掌握了浸采范围外“残难矿体”的位置,并对其进行了剩余资源量估算,结果表明剩余资源量可观,有待进一步研究。应用价格法测算矿床的经济指标,对矿床进行技术经济评价,将经济平米铀量作为阈值约束浸采范围外的“残难矿体”资源模型并生成经济块段模型;采用距离幂次反比法对经济块段模型进行资源量估算,得到平米铀量在经济指标之上的资源量。通过研究,掌握了研究区内纵向浸采范围外“残难矿体”的精确位置、剩余资源量和经济性,实现了对地浸开采矿山剩余资源量的经济评价。

铀矿浸出试验柱不同高度上铀金属浸出的规律

针对铀矿堆浸生产中矿堆不同高度上的铀金属浸出存在的延迟现象,采用理论分析和室内柱浸试验研究铀矿浸出试验柱不同高度上铀金属浸出的规律。理论分析将铀矿浸出试验柱沿柱高划分为若干个高度足够小且相等的单元体,使其中单个铀矿石颗粒的浸出符合收缩未反应核扩散控制系统模型,且任意1个单元体内所有铀矿石颗粒反应均匀,不存在延迟现象,进而以1个单元体为目标,根据溶浸剂质量守恒原理,并考虑初始溶浸剂浓度的变化,建立铀矿浸出试验柱不同高度上铀金属浸出的数学模型。采用颗粒半径为2.5 mm的铀矿石进行串联柱浸试验。然后,采用数学模型对柱浸试验结果进行计算,并将模型计算结果与柱浸试验结果进行比较。研究结果表明:试验柱不同高度上铀金属浸出率存在较大差别,且模型计算值与柱浸试验值具有相同的变化趋势,表明该数学模型能较好地反映铀矿浸出试验柱不同高度上铀金属浸出的延迟规律,可为预测铀矿堆浸不同高度上的浸出率提供重要参考。

我国中、新生代盆地砂岩型铀矿沉积环境研究概述

分析我国砂岩型铀矿沉积环境研究领域现状及研究意义、含铀碎屑沉积建造类型及其沉积特征、砂岩型铀矿成矿有利相位,并提出砂岩型铀矿沉积环境研究应该注意的几个问题。

原地溶浸开采中的多过程耦合作用与反应前锋运动:2.数值模拟

基于流体流动、溶解反应、孔隙度变化、质量守恒等机理建立了原地溶浸开采的多过程耦合与反馈的动力学模型,并编制了模拟程序。应用该模型和程序可以对原地溶浸开采过程中反应前锋的运动进行数值模拟。以用硫酸和氧化剂配制的溶液作溶浸剂的原地溶浸采铀为例,数值模拟结果表明,无论是在均匀孔隙岩石中还是在非均匀孔隙岩石中都可产生复杂形态的反应前锋运动,反应前锋的运动特征和形态稳定性与流体流速和模拟区域大小有关。反应前锋的动力学模拟与研究在原地溶浸采铀的生产和技术研究中有重要意义和应用前景。

某铀矿地浸采区的水动力场三维模拟

原地浸出采铀生产期间的地下水动力场直接控制着污染物的迁移,以我国某地浸矿山为例,通过建立三维数学模型,采用Visual MODFLOW软件,对其采区内的水动力场进行计算,模拟生产期间含矿含水层的水流动态。

某高矿化度砂岩型铀矿地浸开采堵塞机理的研究

新疆某高矿化度地下水分布区砂岩型铀矿采用酸法和碱法地浸时易出现堵塞,采用地球化学模式PHREEQCI模拟和实验研究的方法对堵塞进行了探讨。结果表明,堵塞主要是因为地下水的矿化度(TDS)、Ca2+、Mg2+、SO42-、HCO3-浓度过高,分别为8～12g/L、386.17～775.95 mg/L、250.83～377.21mg/L、2 036.47～2 436.08mg/L、108.66～527.55mg/L,方解石和石膏临近饱和状态;采用酸法和碱法地浸工艺分别会产生石膏和方解石沉淀而引起化学堵塞。该砂岩型铀矿适合采用稀释或水处理—弱碱性地浸工艺。

铀矿堆浸对流−弥散−反应耦合动力学模型

铀矿堆浸过程中铀的浸出是溶浸液在多孔介质中对流、弥散以及反应耦合作用的结果。首先采用理论分析和数学建模的方法建立了铀矿堆浸对流−弥散−反应耦合动力学模型,然后采用有限元法对该动力学模型进行解算,最后采用铀矿柱浸试验对解算结果进行了验证。结果表明:所建立的铀矿堆浸对流−弥散−反应耦合动力学模型能反映浸出柱中主要特征变量的变化,同时可以表征浸出柱不同深度处溶浸液和铀的浓度、各粒级铀矿石的浸出率、各粒级铀矿石缩核随时间的分布,因而能准确预测浸出柱铀矿石的浸出率。因此,该对流−弥散−反应耦合动力学模型可用于铀矿堆浸铀浸出率的预测及工艺参数的调控。

强风化强氧化型砂岩铀矿组合浸出工艺及浸出动力学模型

首先,从我国某急倾斜疏干型铀矿床采取铀矿石样,分析其岩石组成、矿物组成和化学组成;其次,将每一类含铀的岩石分别破碎成小于10 mm的颗粒,将其筛分成[0,1),[1,3),[3,5)和[5,10) mm这4个粒级,并将各类岩石按其所占比例进行混合组成综合铀矿样,再将其分别破碎成粒径小于20,15,10和5 mm的颗粒,将它们筛分成[0,1),[1,3),[3,5),[5,10),[10,15)和[15,20) mm这6个粒级,分析各粒级铀矿石的质量分数和品位;第三,将综合铀矿样破碎成粒径小于10 mm的颗粒,将其筛分成[0,0.5)和[0.5,10)这2个粒级,对前者进行搅拌浸出试验,对后者进行柱浸试验;最后,采用ORIGIN软件拟合柱浸试验结果,建立柱浸动力学模型并进行验证。研究结果表明:铀矿石主要由砂岩、砾岩和泥岩组成,其质量分数分别为57%,25%和18%,铀矿物主要为含铀黏土矿物、沥青铀矿物、硅铝铀矿物和水硅铀矿物,且U(VI)质量分数达96.8%,属于强风化强氧化型铀矿石;铀矿石经破碎后,[3,5) mm粒级铀矿石的质量分数最小,而品位最高;铀矿石柱浸动力学模型为y=1-e^(-kx),模型参数k与铀矿石粒径呈线性负相关,与硫酸和氯酸钠质量浓度呈线性正相关;对强风化强氧化型铀矿石宜采用搅拌浸出-堆浸组合工艺进行处理,堆浸后期适当增加溶浸液和氧化剂质量浓度可以改善浸出效果,所建立的柱浸动力学模型可以用于预测和控制堆浸过程。

地浸采铀浸出液铀质量浓度预测研究

详细介绍地浸采铀浸出液铀质量浓度预测模型的建立过程。提出了基于灰色系统理论的铀质量浓度预测数学模型,并开发了相应的计算机应用系统。

基于Origin的溶浸浸出率预测模型研究

溶浸浸出率预测的准确程度对于应用溶浸采矿技术的矿山设计、生产和研究具有重要的指导意义。采用Origin软件对铜尾矿摇瓶浸出和铀矿石堆浸的浸出率进行模拟和预测。先根据矿石浸出率的变化规律,选取不同的数学模型,再采用该模型对浸出率原始数据进行模拟,对未来数据进行预测。预测结果表明,不同数学模型对溶浸浸出率的预测效果不同,模型(2)更适合溶浸浸出率的长期预测。

铀矿堆浸分形动力学模型

本文采用堆浸铀矿石粒径分布分维数代替其平均粒径,对Mellado等提出的矿石堆浸动力学模型进行了改进。同时采用铀矿柱浸试验确定了铀矿堆浸分形动力学模型参数与堆浸铀矿石粒径分布分维数的关系,建立了铀矿堆浸分形动力学模型,并进一步采用柱浸试验对模型进行了验证。结果表明,所建立的铀矿堆浸分形动力学模型能很好地反映铀矿堆浸铀金属浸出的规律。

基于Lotka-Volterra的生物浸铀微生物生长动力学模型研究

前人研究表明,生物浸铀过程中浸矿和辅助浸矿微生物两者间存在协同作用,两者相互促进提高生物浸铀效率。浸矿和辅助浸矿微生物是如何相互促进,使彼此更好地得到生长,两者相互促进生长动力学模型是什么?Lotka-Volterra模型被广泛应用在两种间相互作用下生物数量增长模型研究中,对于生物浸铀中浸矿和辅助浸矿微生物生长动力学模型研究具有借鉴意义。由Lotka-Volterra模型得出了浸矿和辅助浸矿微生物独立共生和竞争共生方程,根据浸矿和辅助浸矿微生物协同特性建立了其生长动力学模型,由模型再推导出浸矿和辅助浸矿微生物协同作用稳定态点,该稳定态点与试验结果相差较小,说明生物浸铀浸矿和辅助浸矿微生物生长动力学模型拟合效果较好。将Lotka-Volterra模型应用到生物浸铀中,具有新颖性,提供了新的研究视角,对完善生物浸铀中微生物协同问题、提高生物浸铀效率具有重要的理论与实际意义。

砂岩型铀矿床地浸地质工艺性能综合定量评价指标——地浸指数的设计与应用

从砂岩型铀矿床地浸开发工艺着手 ,通过对其地质影响因素分析 ,结合各因素对地浸开发的影响程度 ,提出了砂岩型铀矿床地浸的地质工艺性能综合评价指标———地浸指数 (LI) ,并建立了其计算模型。通过计算地浸指数可定量地了解待开发矿床或块段的地浸开发适宜程度。地浸指数LI值越大 ,说明该矿床地浸的地质工艺性能越佳、越有利于地浸开发。通过对伊犁盆地 5 1 2模型铀矿床、 5 1 1铀矿床及吐哈盆地十红滩铀矿床的LI值试算 ,得到的LI值分别为 1 1 9 95、 1 0 2 5 6和 47 81。试算结果表明 ,5 1 1矿床很有利于地浸开发 ,5 1 1矿床地浸开发的有利性逊于 5 1 2矿床 ,十红滩矿床属于不利于地浸的范畴 ,建议放弃酸法地浸方案 ,寻求低酸法地浸、清水地浸或碱法地浸等方案。结合 3个矿床的工业开发实际和前期试验成果 ,初步确定砂岩型铀矿床地浸地质工艺性能的LI值区间 :LI≥ 1 0 0 ,很有利于地浸 ;80≤LI<1 0 0 ,有利于地浸 ;LI<80 ,不利于地浸。

铀矿堆浸酸性尾渣中和的动力学特征及模型

采用氧化钙、氢氧化钠和氨水作为中和剂,对铀矿堆浸酸性尾渣进行中和试验,试验过程中检测了中和体系的pH随时间的变化,并根据检测结果建立了尾渣中和的动力学模型。结果表明,铀矿堆浸酸性尾渣的中和过程,包括尾渣颗粒表面余酸与中和剂的快速反应,及尾渣颗粒内部余酸与中和剂的缓慢扩散-反应两个阶段;中和过程中,中和剂扩散-反应的非线性耦合和反馈作用模型,可很好地反映尾渣中和反应的过程和方式,中和体系的pH呈现出明显的非线性振荡现象;尾渣中和的动力学模型,能很好地拟和中和体系的pH随时间的变化。