Heap Leaching Kinetics of Uranium Ore with Single Particle Fraction and Varied Particle Size Distribution
|Keywords||heap leaching kinetic model uranium ore particle size distribution fractaldimension|
Heap leaching technology is development with the exploitation and recovery of thelow-grade ores economic and efficient. Nowadays, it has been widely used in many kindsof low-grade metals and some non-metallic mineral leaching. In present of China, due tothe characteristics of the uranium resources and mining technology, heap leachingtechnology is the subject uranium leaching technology. There is a characteristic of heapleaching technology, that the particle size of heap leaching is bigger than the particle ofconventional hydrometallurgy. So the leaching rate is not only related to the rate ofchemical reaction, but also related to the ore particle size and particle size distribution.Therefore, it is necessary to consider the ore particle size and particle size distribution inthe kinetics research of uranium leaching.This paper mainly studies the impact of uranium ore particle size and its particle sizedistribution in heap leaching process by uranium ore column leaching test in the laboratory.The mainly results of this paper are as follows:In order to consider the different leaching in the different height of the column, thetest column is divided into several small enough and equal columns along the height, andensure that the leaching of single ore particle corresponds shrinking core model anddiffusion control system, and the reaction of all uranium ore particles is uniform in a smallcolumn. Then, one small column is researched as the typical case, to build a mathematicalmodel for the single particle size of ore reaction in ideal state, based on the massconservation principle of leaching agent, and consideration the changing of initial leachingagent concentration.As the requirement of the test, a series column of leaching test apparatus is designedand produced. And the single size fraction uranium ore is leaching in the apparatus, tosimulation of the single size fraction uranium ore heap leaching. Then, compare the valuebetween the results of model calculation and the results of uranium column leaching test,shows that the reliability of the mathematical model. At the same time, it shows that the mathematical model of single size fraction uranium ore can predict the uranium leachingrate in different heights of the column.Screening analysis for the heap leaching uranium ore of a uranium mine, the resultsshow that the ore particle size distribution conforms to the fractal distribution.Five uranium ore samples with the different fractal dimensions (D) of particle sizedistribution are prepared, and the five samples are leached in columns to investigate theinfluences of the fractal dimensions of particle size distribution on their leachingperformances. The leaching data are analyzed using the shrinking core model, and thewhole process of the column leaching is divided into two phases based on the pH and thepotential vs. saturated calomel electrode (SCE) of the pregnant leach solution (PLS) fromthe columns. The kinetic models for the different phases have different form, and theparameters all have functional relationship with fractal dimension.