Mercury Control in Pressure Oxidation via Halogen Scavenging
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Solution Overview
Problem
The challenge in gold mining is the inefficient recovery of gold from refractory ores due to mercury oxidation during pressure oxidation processes, leading to significant mercury emissions and difficulties in waste treatment.
Innovation Solution
A method for conducting pressure oxidation under controlled conditions using a halogen-containing material to inhibit mercury dissolution, maintaining specific oxidation/reduction potential, ferrous iron concentration, and adjusting operating parameters to keep mercury primarily in the solid phase, thereby reducing emissions and improving gold recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pressure oxidation is conducted under strongly oxidizing conditions to oxidize sulfide minerals, then gold recovery is improved, but mercury dissolution increases leading to emissions and waste treatment difficulties
Solution Approach 1:
The patent applies parameter changes by controlling the oxidation-reduction potential (ORP) to remain below a threshold value during pressure oxidation. This parameter control prevents mercury oxidation while maintaining conditions favorable for sulfide mineral oxidation and gold recovery, thus resolving the contradiction between improving gold recovery and preventing mercury emissions
Solution Approach 2:
The patent implements preliminary anti-action by adding mercury scavenge material before or during the pressure oxidation process. This material preferentially binds with mercury to form stable complexes, preventing mercury from being oxidized and emitted, while not interfering with the gold recovery process
2Loss of substance
If oxidation conditions are intensified to dissolve more mercury, then mercury can be removed from the system, but gold recovery efficiency decreases and waste treatment becomes more difficult
Solution Approach 1:
The patent introduces a mercury scavenge material as an intermediary substance that selectively binds with mercury. This intermediary allows mercury to be captured and removed from the system without requiring intensive oxidation conditions that would harm gold recovery, thus resolving the contradiction between mercury removal and gold recovery efficiency
Solution Approach 2:
The patent extracts mercury from the system by using mercury scavenge material to bind and concentrate mercury in a separate phase or solid residue. This extraction approach removes mercury without needing to intensify oxidation conditions, maintaining gold recovery efficiency while achieving mercury removal
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 effectively minimizes mercury dissolution and emissions, simplifies waste treatment, and enhances gold recovery from refractory ores by maintaining mercury in the solid residue, while optimizing gold recovery without the need for controlling free acid concentration.
Implementation Method 1
A method for conducting pressure oxidation under controlled conditions using a halogen-containing material to inhibit mercury dissolution
Implementation Method 2
Pressure oxidation oxidizes sulfide minerals, rendering the residue non-refractory. The gold is then dissolved by cyanidation
Implementation Method 3
Because the conditions that promote the oxidation of gold bearing sulfides can also oxidize mercury associated with sulfides, it is possible to dissolve the majority of mercury in the autoclave slurry. For cinnabar, which contains most of the mercury in the ore, the reaction is: HgS+2O2→Hg2+SO42−
Data Source
AI summary
A method for suppressing mercury dissolution during pressure oxidation of precious metal-containing materials in the presence of halogens and halides is provided. Pressure oxidation is performed under controlled oxidative conditions to maintain the mercury predominantly in the solid residue.