Heap Bioleaching Temperature Control via Carbon Addition
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Solution Overview
Problem
In heap bioleaching processes for recovering copper from low-grade ores, particularly those containing refractory primary sulphide minerals like chalcopyrite, the temperature is often insufficient due to limited microbial activity, as ambient temperature microorganisms cannot grow at elevated temperatures, and carbon dioxide becomes a limiting factor for microbial growth and heat generation.
Innovation Solution
The method involves adjusting operating parameters by adding carbon, such as increasing carbon dioxide in the air or providing organic carbon sources like yeast extract, and/or applying heat to the heap to enhance microbial activity and heat generation, particularly in the 45° C. to 60° C. range, to overcome temperature limitations and sustain microbial growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ambient temperature microorganisms are used for bioleaching, then the process can start at low temperatures, but the microorganisms cannot grow and contribute to bioleaching at elevated temperatures above 45°C
Solution Approach 1:
The patent applies dynamics by transitioning from static ambient temperature microorganisms to a dynamic sequential population approach. The system evolves through distinct phases: Phase 1 uses mesophilic microorganisms at ambient temperatures (20-45°C) for initial bioleaching, then Phase 2 introduces thermophilic microorganisms at elevated temperatures (45-70°C) to maintain activity as temperature increases, allowing continuous adaptation throughout the heating process
Solution Approach 2:
The patent applies parameter changes by systematically altering temperature parameters through controlled heating rates (0.5-5°C per day) and adjusting microbial population parameters by introducing sequential cultures with different temperature optima. This allows the system to transition from mesophilic to thermophilic conditions while maintaining bioleaching efficiency
2Temperature
If sequential populations of bioleaching microorganisms are used to raise heap temperature, then chalcopyrite leaching can occur at elevated temperatures, but carbon dioxide becomes limiting to microbial growth and heat generation
Solution Approach 1:
The patent applies intermediary by introducing organic carbon sources (molasses, yeast extract, or other carbon-containing compounds) as a mediator between the limiting carbon dioxide and the thermophilic microorganisms. This intermediary organic carbon supplements the carbon supply, enabling continued microbial growth and heat generation when CO2 becomes limiting at elevated temperatures
Solution Approach 2:
The patent applies parameter changes by monitoring and adjusting carbon availability parameters through measurements of microbial activity indicators (heat generation rate, gas production) and responding by adding appropriate carbon sources when deficiency is detected, thereby maintaining optimal carbon levels for thermophilic bioleaching
3Productivity
If thermophilic microorganisms are introduced to maintain activity at elevated temperatures, then chalcopyrite leaching rate increases, but heat losses increase and require additional heat input
Solution Approach 1:
The patent applies preliminary action by implementing insulation measures and heat retention strategies before significant heat losses occur. The heap is insulated with appropriate materials and designed with heat retention features from the outset, and controlled heating rates are established in advance to minimize thermal gradients and energy waste while maintaining optimal temperatures for thermophilic activity
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 raises heap temperatures, enabling continued microbial activity and heat generation beyond the typical 50° C. plateau, facilitating copper recovery from chalcopyrite and other copper-bearing ores by supporting thermophilic microorganisms and optimizing microbial growth rates.
Implementation Method 1
the microorganisms oxidise ferrous iron to ferric iron
Implementation Method 2
the ferric iron facilitates an initial attack on the sulphide while sulphur oxidising microorganisms further oxidise the reduced sulphur species to sulphate
Implementation Method 3
the microbial oxidation of such sulphur species results in the release of heat
Implementation Method 4
by applying thermal insulation to the heap to reduce heat losses
Data Source
AI summary
A heap bioleaching process wherein carbon, in the form of a carbonate, carbon dioxide or organic carbon, is added to the heap when the temperature in the heap is in the range of 45° C. to 60° C. to increase microbial activity and thereby raise the heap temperature to about 60° C.