Lime Consumption Reduction in Refractory Gold Ore Pressure Oxidation
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Solution Overview
Problem
The formation of basic iron sulphate and jarosite during pressure oxidation of precious metal-containing sulphide materials leads to increased operating costs due to the need for expensive neutralization agents, as these compounds are chemically unstable and difficult to separate from precious metals, whereas hematite formation is more desirable due to its stability and inertness.
Innovation Solution
A process involving the oxidation of an aqueous feed slurry in an autoclave, followed by acid consumption and separation of iron-containing precipitates to form dissolved iron compounds, allowing time for basic iron sulphate to convert to solubilized ferric sulphate, which can be recycled and used to reduce oxygen requirements and lime consumption, and using a multi-compartment autoclave to control sulphuric acid levels and favor hematite formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pressure oxidation is used to destroy the sulphide matrix, then gold recovery is improved, but basic iron sulphate and jarosite form which increase operating costs
Solution Approach 1:
The patent changes the chemical parameters of the oxidation environment by controlling pH, temperature, and oxygen concentration to favor the formation of hematite over basic iron sulphate and jarosite. By maintaining specific pH ranges and optimizing oxidation conditions, the process directs iron precipitation toward the desired hematite form which does not consume neutralization agents.
Solution Approach 2:
The patent converts the potentially harmful formation of basic iron sulphate and jarosite into beneficial hematite formation by manipulating oxidation conditions. The iron that would otherwise form unstable, neutralization-consuming compounds is redirected to form stable hematite, turning a harmful side reaction into a beneficial outcome that reduces operating costs.
2Quantity of substance
If basic iron sulphate and jarosite are formed during oxidation, then iron compounds are produced, but they are chemically unstable and require expensive neutralization
Solution Approach 1:
The patent modifies the chemical environment parameters (pH, temperature, oxidation potential) to stabilize iron compounds as hematite rather than allowing formation of unstable basic iron sulphate and jarosite. By controlling these parameters, the process ensures iron precipitates as the chemically stable hematite form that remains inert during subsequent neutralization.
3Stability of the object's composition
If hematite is formed instead of basic iron sulphate, then chemical stability is improved, but the process requires controlled oxidation conditions
Solution Approach 1:
The patent implements feedback control mechanisms to monitor and adjust oxidation conditions in real-time. By measuring pH, oxygen concentration, and oxidation state, the system automatically adjusts process parameters to maintain conditions favorable for hematite formation, reducing the need for complex manual intervention while ensuring stable iron compound formation.
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 reduces the consumption of expensive neutralization agents, lowers operating costs, and promotes the formation of hematite over basic iron sulphate and jarosite, enhancing the efficiency of precious metal recovery by allowing sufficient time for conversion of basic iron sulphate to solubilized ferric sulphate and optimizing acid levels in the autoclave compartments.
Implementation Method 1
oxidizing an aqueous feed slurry in an autoclave
Implementation Method 2
allowing most, if not all, of iron-containing precipitates in the aqueous discharge solids to react with acid in the aqueous discharge liquid to form dissolved iron compounds
Data Source
AI summary
The present invention is directed to a precious metal recovery process in which basic ferric sulphates and/or jarosites are controlled by a number of mechanisms, including control of the oxidation reaction conditions in the first autoclave compartment, hot curing of the autoclave discharge slurry, and/or contacting of the autoclave feed slurry with the hot cured discharge liquid.