Classified Sand Heap Leaching for Permeability and Metal Extraction
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Solution Overview
Problem
Conventional heap leaching methods suffer from low metal extractions due to micro- and macro-permeability issues within rock heaps, leading to inefficient processing of ores, especially for high-grade ores, and are limited by high operational costs in alternative methods like agitation leaching.
Innovation Solution
A method involving crushing ores to expose at least 85% of valuable mineral grains with a P80 of less than 5 mm, classifying to remove fines, and forming a sand heap with specific permeability characteristics to enhance macro- and micro-permeability, allowing efficient distribution of leachant and air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ores are crushed finer to increase micro-permeability and expose valuable mineral grains, then metal extraction efficiency improves, but macro-permeability of the heap decreases due to excessive fines impeding fluid flow
Solution Approach 1:
The patent segments the particle size distribution into specific ranges (P80 < 5mm for micro-permeability while maintaining P10 > 0.15mm for macro-permeability). This segmentation allows simultaneous optimization of both fine particle exposure for leaching and coarse particle framework for fluid flow, resolving the contradiction between extraction efficiency and heap permeability.
Solution Approach 2:
The patent applies local quality by creating different particle size zones within the heap structure. The classified sand with controlled P10 and P90/P10 ratio ensures that fine particles are distributed uniformly without creating localized clogging zones, while maintaining overall heap permeability. This local optimization allows both fine particle leaching and bulk fluid flow to occur effectively.
2Ease of manufacture
If conventional heap leaching is used to maintain low processing costs, then operational expense is reduced, but metal extraction remains low due to permeability constraints
Solution Approach 1:
The patent changes the critical parameters of particle size distribution (P80 < 5mm, P10 > 0.15mm, P90/P10 < 25) to transform conventional heap leaching into a high-extraction process. These parameter changes enable the use of simple heap leaching infrastructure while achieving extraction levels previously only attainable through complex agitation leaching, thus maintaining low costs while improving productivity.
Solution Approach 2:
The patent makes heap leaching multi-functional by enabling it to process both low-grade and high-grade ores effectively through the classified sand method. The same heap leaching infrastructure can now achieve high extractions across different ore grades, eliminating the need for separate processing routes and reducing overall processing costs while maintaining high productivity.
3Reliability
If particle size is reduced to improve micro-permeability, then leachant access to valuable minerals improves, but fines accumulate and block leachant flow in heap zones
Solution Approach 1:
The patent extracts the harmful fine fraction from the ore through classification before heap formation. By removing excessive fines that would cause blocking while retaining sufficient fine particles for mineral exposure, the process eliminates the harmful effect of fines accumulation while preserving the beneficial micro-permeability characteristics needed for effective leaching.
Solution Approach 2:
The patent performs preliminary classification of the ore into the specified particle size range before heap leaching. This preliminary action of classifying to achieve P10 > 0.15mm and P90/P10 < 25 prevents fines accumulation problems from occurring during the leaching process, ensuring both reliable leachant access and sustained heap permeability throughout operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Achieves higher and faster metal extractions, enabling the use of diverse leachants, reducing reagent losses, and allowing flexible heap operations, including dynamic leaching and sequential leaching, thus overcoming limitations of conventional heap leaching.
Implementation Method 1
a sand heap with high macro-and micro-permeability... distributing leachant and air through the heap
Implementation Method 2
leaching is a widely used method of metal extraction... distributing leachant and air through the heap to leach the values from the sand in a pregnant leachate
Data Source
AI summary
THIS invention relates to a method of recovering metal values such as gold, copper, nickel, zinc and uranium from ores containing said metal values. The method includes the steps of crushing an ore (10) to provide a sand containing metal values with a P80 of less than 5 mm but greater than 1 mm; classifying the sand (12) to remove a finer fraction to provide classified sand with a P10 of greater than 0.15 mm, and a P90/P10 ratio of less than 25 and greater than 3, forming a heap (18) from the classified sand, and distributing leachant and air through the heap to leach the values from the sand in a pregnant leachate, from which the leached values may be recovered. The invention also relates to a heap formed from ore processed by this method.