Onsite PSA Oxygen Generation Plant for Gold Leaching

Oxygen Is a Process Input in Gold Leaching

In conventional aerated leaching tanks, oxygen is introduced into the slurry through air injection or mechanical aeration. However, atmospheric air contains only approximately 21% oxygen. When oxygen demand increases, simply increasing the volume of air does not always provide the desired dissolved oxygen concentration because the actual oxygen transfer depends on: gas-liquid contact, bubble size, mixing intensity, slurry density, temperature, pressure, and oxygen concentration in the injected gas.

An oxygen generation plant increases the oxygen concentration available to the leaching system, providing a more concentrated gas source for oxygen injection. This allows the process engineer to control oxygen supply independently from the total air volume.

Where Oxygen Fits Into the Gold Recovery Process

A simplified process arrangement can be represented as:

Crushing → Grinding → Slurry Preparation → Leaching → Solid-Liquid Separation → Gold Recovery

The oxygen generation system is connected to the leaching section rather than being treated as a general-purpose plant utility. Depending on the process design, oxygen may be introduced through: Tank spargers, Oxygen diffusers, Injection lances, Venturi systems, Oxygenation columns, or Specialized gas-liquid contacting equipment. The oxygen plant therefore needs to be matched with the characteristics of the existing leaching circuit.

Why On-Site Oxygen Generation Can Be Used for Gold Leaching

1. Eliminate Dependence on Delivered Oxygen

Remote gold processing facilities may be far from industrial gas suppliers. Purchased oxygen may require cylinder transportation, liquid oxygen delivery, storage facilities, and complex delivery scheduling. An on-site oxygen plant produces oxygen directly at the processing facility. The raw material-ambient air-is continuously available at the site.

2. Provide a More Concentrated Oxygen Source

The oxygen concentration produced by a PSA system is substantially higher than atmospheric air. This gives the process plant a concentrated oxygen source that can be injected into the leaching circuit according to process requirements. The objective is not simply to maximize oxygen purity; the more important engineering consideration is whether the selected oxygen concentration and flow rate can maintain the required dissolved oxygen conditions in the leaching tanks.

Oxygen Demand Depends on the Leaching Circuit

There is no universal oxygen generator size for gold processing. Required oxygen capacity depends on several process variables. For this reason, equipment selection should begin with the process data rather than selecting an oxygen generator based only on plant size.

PSA Oxygen Generation for Gold Processing

The plant uses Pressure Swing Adsorption (PSA) technology to separate oxygen from compressed atmospheric air through standard cycle stages:

Oxygen Supply Is Only One Part of the System

For gold leaching applications, simply installing an oxygen generator does not guarantee effective oxygen utilization. The complete system should consider:

Oxygen Generator → Oxygen Buffer → Pressure Regulation → Distribution Pipeline → Injection System → Leaching Tank

Each section affects final oxygen delivery. For example, insufficient pipeline diameter can create excessive pressure loss, while an unsuitable diffuser can reduce oxygen transfer efficiency. Therefore, the oxygen plant should be engineered together with the oxygen injection system whenever project conditions allow.

Oxygen Transfer Is More Important Than Oxygen Production Alone

The amount of oxygen produced by the plant is not necessarily the same as the amount of oxygen dissolved into the slurry. The actual process performance depends on oxygen transfer efficiency. Important factors include:

• Bubble Size: Smaller bubbles provide a larger gas-liquid contact area and may improve oxygen transfer.
• Mixing: Adequate slurry circulation distributes dissolved oxygen throughout the tank.
• Injection Depth: Greater injection depth increases hydrostatic pressure and can influence gas dissolution.
• Slurry Properties: High solids concentration and viscosity can affect gas dispersion and transfer.
• Oxygen Flow: Excessive gas flow may not proportionally increase dissolved oxygen if the injection system is already operating near its transfer limit.

This is why oxygen generation and oxygen injection should be evaluated as one process system.

Suitable for Different Gold Leaching Configurations

Agitated Tank Leaching

Oxygen can be supplied to mechanically agitated leaching tanks through spargers or other gas injection systems. This configuration is commonly considered where controlled oxygen availability is required throughout the reaction tanks.

Intensive Leaching Circuits

For high-throughput or high-intensity leaching systems, the oxygen plant can provide a dedicated oxygen source for the reaction circuit. The system can be engineered according to slurry flow, tank volume, oxygen consumption, and required dissolved oxygen conditions.

Pilot and Demonstration Plants

A smaller oxygen generation system can be integrated into pilot-scale gold processing facilities for process development and evaluation.

Engineering Configuration & System Modules

The exact configuration should be determined according to the customer's process flow and oxygen injection method.

Technical Specifications

Final oxygen capacity and pressure should be determined from process throughput, leaching conditions, dissolved oxygen requirements, and injection system characteristics.

How to Select the Correct Oxygen Plant

A gold processing plant should provide several key parameters before equipment selection:

1. Ore Throughput

For example: tonnes of ore per day or tonnes of slurry per hour. This provides the basic reference for estimating oxygen demand.

2. Slurry Characteristics

Important data include: Solids concentration, Slurry density, Temperature, pH, and Viscosity. These conditions directly affect oxygen mass transfer.

3. Existing Aeration System

Understand whether oxygen will be introduced through existing spargers, diffusers, lances, Venturi injectors, or oxygenation columns. Oxygen supply pressure must be compatible with existing equipment.

4. Dissolved Oxygen Requirement

The required dissolved oxygen concentration should be defined by the process engineer according to leaching chemistry. The oxygen generator is then sized to provide sufficient oxygen flow under those conditions.

Operating and Monitoring Parameters

For process-oriented oxygen supply, operators can monitor: Oxygen purity, Oxygen flow, Oxygen pressure, PSA operating status, Compressor condition, Oxygen consumption, and Alarm status. Where the plant is integrated with the main process control system, oxygen supply data can also be incorporated into centralized plant monitoring.

Benefits & Mine Site Engineering

Benefits for Gold Processing Operators

• More Direct Control of Oxygen Supply: The plant directly controls gas generation rather than relying on external supply chains.
• Reduced Oxygen Logistics: On-site production eliminates cylinder handling, liquid oxygen delivery, storage logistics, and scheduling risks-especially valuable for remote mines.
• Consistent Oxygen Availability: Continuous PSA production operates alongside the leaching circuit without shutdown interruptions.
• Easier Integration: Configured around existing pipeline dimensions, pressure levels, and injection hardware.

Site Conditions for Gold Processing Plants

Gold processing facilities often operate in demanding environments. The oxygen plant can be specifically configured for: Ambient temperature extremes, High altitude, Heavy dust concentration, Elevated humidity, and Custom electrical power supplies.

For remote mine sites, containerized installation is available to house oxygen generation equipment, air treatment, controls, and auxiliaries within a weather-protected, insulated enclosure.

FAQ

Q: Why is oxygen used in gold leaching?

Oxygen participates in the oxidation reactions associated with gold dissolution in cyanide-based leaching systems. Maintaining suitable oxygen availability can therefore be an important process consideration.

Q: Is 90–95% oxygen suitable for gold leaching?

PSA oxygen in this range can be used as an oxygen source for many industrial applications. The appropriate oxygen concentration should ultimately be determined by the leaching process, injection system, and required dissolved oxygen conditions.

Q: Can the oxygen plant connect to an existing leaching circuit?

Yes. The system can be designed around the existing oxygen injection equipment, pipeline pressure, and process oxygen demand.

Q: How is oxygen generator capacity calculated?

Capacity should be determined using process throughput, slurry conditions, oxygen demand, dissolved oxygen requirements, and oxygen transfer efficiency rather than using tank volume alone.

Q: Can the system be installed at a remote gold mine?

Yes. Skid-mounted and containerized configurations can be designed for remote mining environments where conventional oxygen infrastructure is difficult to construct.