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

Combined leaching process for strongly weathered and oxidized sandstone uranium ore and its kinetic model

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。

Firstly, uranium ore sample was taken from the steeply inclined and drained sandstone uranium deposit in China, and the rock, mineral and chemical compositions were analyzed. Secondly, each kind of rock was crushed to particles with smaller than 10 mm, which were screened to [0, 1), [1, 3), [3, 5) and [5, 10) mm fractions for the analysis of their mass fraction and grade, and all kinds of rocks were mixed on the basis of their mass fraction to form comprehensive uranium ore samples, which were crushed to particles with smaller than 20, 15, 10,and 5 mm, respectively, and were screened to [0, 1), [1, 3), [3, 5), [5, 10), [10, 15),and [15, 20) mm fractions for the analysis of their mass fraction and grade. Thirdly, comprehensive uranium ore sample was crushed to particles with smaller than 10 mm, which were screened to [0, 0.5) and [0.5, 10) mm fractions, and [0, 0.5) mm fraction uranium ore particles were treated with agitated leaching, and the [0.5, 10) mm fraction uranium ore particles were treated with column leaching. Finally, the column leaching data were fitted by ORIGIN to establish kinetic model,and the model was verified by column leaching test. The results show that the uranium ore was mainly composed of sandstone, conglomerate and mudstone, with mass fraction being 57%, 25%, and 18%, respectively. The uranium minerals mainly include uranium bearing clay mineral, asphaltic uranium mineral, silicon aluminum uranium mineral, and water silicon uranium mineral. The mass fraction of U(VI) is 96.8% and the uranium ore is the strongly weathered and oxidized one. After the uranium ore was crushed to particles, ore particles of [3, 5) mm fraction have the highest grade but the smallest mass fraction. The column leaching kinetic model is y =(1-e^(-kx))and the parameter k in the model has a linear negative correlation with ore particle size and a linear positive correlation with leaching solution concentration and oxidant mass concentration. The combined leaching process including agitated leaching and heap leaching is adequate for treating the strongly weathered and oxidized uranium ore. The leaching efficiency could be improved by increasing mass concentrations of the leaching solution and oxidant in the latter stage of the heap leaching process. The established column leaching kinetic model could be used to predict and control heap leaching process.