Lime Suspension Dosing for Heap Leaching pH Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In gold and platinum group metals heap leaching, suboptimal pH control leads to inefficient cyanide utilization and gold recovery due to pH gradients and mismatched lime addition, resulting in increased operational costs and environmental impact.
Innovation Solution
A process that involves forming a dispersed fine particle lime suspension with Ca(OH)2 particles added upstream and downstream of the irrigation system, allowing for continuous pH regulation and synchronized lime demand satisfaction, reducing the need for initial dry quicklime addition and minimizing cyanide consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If dry quicklime is added to ore during stacking, then initial pH buffer is provided, but pH gradients develop during leaching and lime addition becomes mismatched with demand
Solution Approach 1:
The invention transitions from static lime addition at stacking to dynamic lime addition during leaching. A lime dosing system continuously monitors pH and adjusts lime addition rates to match actual consumption, making the pH control system adaptive to changing conditions throughout the leaching process.
Solution Approach 2:
The invention implements pH monitoring with feedback control. pH meters continuously measure the leachate pH, and this information feeds back to control the lime dosing system, ensuring lime addition matches actual consumption and maintaining optimal pH levels throughout the heap.
2Ease of operation
If lime is added upstream of irrigation system, then pH control is simplified, but synchronization with lime demand throughout the heap is poor
Solution Approach 1:
The invention applies lime at multiple locations within the irrigation system rather than a single upstream point. Lime dosing points are distributed throughout the heap structure, ensuring local pH control where it is most needed and improving uniformity of pH distribution across different zones of the heap.
Solution Approach 2:
The invention adds the dimension of spatial distribution to lime addition. Instead of adding lime only at the entry point of the irrigation system, multiple dosing points are positioned at different depths and locations within the heap, creating a three-dimensional distribution pattern that better matches lime consumption patterns.
3Device complexity
If suboptimal pH control is maintained, then operational simplicity is preserved, but cyanide utilization efficiency decreases and costs increase
Solution Approach 1:
The invention uses pH monitoring with feedback control to optimize cyanide utilization. By continuously measuring pH and adjusting lime addition accordingly, the system maintains optimal pH conditions for cyanide leaching, preventing cyanide degradation and improving metal recovery efficiency.
Solution Approach 2:
The invention dynamically adjusts the pH parameter throughout the leaching process based on actual consumption. By maintaining pH within the optimal range (10.5-11.5), the system maximizes cyanide effectiveness for gold dissolution while minimizing unnecessary cyanide consumption and associated costs.
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
This approach maintains optimal pH levels throughout the heap, enhancing cyanide efficiency, reducing lime and cyanide consumption, and improving gold and platinum group metals recovery while minimizing environmental impact and operational costs.
Implementation Method 1
Oxygen is important to facilitate cyanide dissolution of gold according to the reaction (I) [and (I′) in its ionic form] below. Dissolved gold-cyanide complex reports to the pregnant leach solution from which it can be recovered by carbon adsorption. 4 Au+8 NaCN+O2+2H2O→4 Na[Au(CN)2]+4 NaOH (I)
Implementation Method 2
Oxygen is important to facilitate cyanide dissolution of gold according to the reaction (I) [and (I′) in its ionic form] below. 4 Au+8 NaCN+O2+2H2O→4 Na[Au(CN)2]+4 NaOH (I)
Implementation Method 3
Cyanide solution flow occurs as unsaturated percolation, meaning that flow channels and pores are not saturated with solution, thereby allowing air ingress carrying oxygen.
Implementation Method 4
Cyanide solution flow occurs as unsaturated percolation, meaning that flow channels and pores are not saturated with solution, thereby allowing air ingress carrying oxygen.
Data Source
AI summary
Process for gold and/or platinum group metals heap leaching comprising irrigating a heap (1) with an irrigation solution (9, 10, 11&12) containing sodium cyanide for leaching gold and/or platinum group metals from said gold and/or platinum group metals containing ore where a lime reagent addition (B) by feeding a fine particle lime suspension containing lime particles in an aqueous phase is done in the irrigation solution.