Oxygen generators for gold mining: a key to sustainable cyanidation and autonomy

Oxygen generators for gold mining

Oxygen generators for gold mining are making an important impact on the industry, specifically helping in creating a more sustainable cyanidation process. On-site oxygen generators, such as PSA and VPSA, are improving the effectiveness of gold leaching while also addressing environmental issues. This blogpost discusses the broader implications of using oxygen generators in the industry, highlighting their contribution to a cost-effective approach to gold extraction. It additionally points to advantages using these generators in remote gold mining operations.

Gold mining, an industry as old as civilization itself, has continually evolved and the introduction of cyanidation, also known as gold leaching, in the late 19th century marked a significant leap forward in gold extraction technology. However, although a leap the process itself has been a continuous challenge for the industry. Cyanide a highly toxic chemical element is not only harmful for the environment but also for the personnel working with it. In gold extraction, the sources of gold are natural and depending on the yield, they are categorized into high-grade ores, low-grade ores, nuggets, and placer deposits. The cyanidation process is particularly crucial for processing both low-grade and high-grade ores, and the efficacy of this process is heavily dependent on the availability of oxygen.

Thus, oxygen supply for the industry is of utmost importance. Traditionally, gold mining operations have relied on various methods to supply the necessary oxygen for cyanidation, including cylinder-based oxygen, and bulk oxygen delivery, known also as industrial oxygen. However, these methods often fall short in terms of sustainability, cost, and logistical efficiency. The use of on-site oxygen generators in this context has marked a significant advancement, as it goes beyond just improving efficiency. In a time when protecting the environment is crucial, using oxygen generators shows a responsible effort towards adopting eco-friendly measures in the gold mining sector.  

What makes on-site oxygen generators a more viable choice is their independence from external supply chains. This is particularly beneficial, because supply chains can be unreliable and costly, especially in remote mining locations. On-site oxygen generators ensure a consistent oxygen supply, crucial for maintaining the efficiency of the cyanidation process.

Cyanidation, also known as the leaching process, is a widely used method in the mining industry for extracting gold and silver from ores.  The oxygenation process enhances the efficiency of cyanidation and ensures maximum gold extraction and yield. Without the presence of oxygen, the leaching process would be significantly slower and less effective.

Gold/silver ore from the mine is crushed and then sent to the mill, where the ore is ground down to a fine particle size. As part of the milling process, water is added to the mill with the ore so that a slurry is formed. This slurry is mixed with a sodium cyanide solution and aerated and agitated in tanks. The cyanide causes the normally unreactive elemental gold to be oxidized

by the oxygen. This Au+ then forms a complex with the cyanide. The overall reaction occurring is as follows:

4Au(s) + 8CN- (aq) + 2H2O (l) + O2 (g) → 4[Au(CN)2]- (aq) + 4OH- (aq)

The oxygenation process enhances the efficiency of cyanidation and ensures maximum gold extraction and yield. Without the presence of oxygen, the leaching process would be significantly slower and less effective.

Oxygen and cyanaditon

Cyanidation intsallation in a gold mine

Cyanide is a highly toxic chemical element which is composed of carbon and nitrogen. It is known for its deadly effects on living organisms, including humans. All waste after leaching process as water, slurry must be treated and monitored for residual free cyanide before depositing.

Cyanide is found in various forms, such as sodium hydrogen cyanide gas or potassium cyanide powder. Due to its potency, cyanide is typically used in industrial processes, such as metal plating and gold mining.

As mentioned before, the process of leaching or cyanidation, is a chemical technique used for gold extraction. The specific application of this technique varies depending on the form and location of the gold. In the gold mining, the extraction methods can generally be divided into three categories, characterized by the yield and type of gold deposit being mined: 

  • High-grade ores: This category of ores refers to those with a higher concentration of gold, which allows for a simpler and less cyanide-intensive process of separating the gold from the surrounding rock through cyanidation.

  • Low-grade ores: consist of very small amounts of gold, which calls for a more rigorous cyanidation procedure accompanied by flotation and roasting, resulting in a greater need for cyanide.

  • Nuggets and placer deposits: typically, do not necessitate cyanidation due to the effectiveness of mechanical techniques such as panning.

Oxygen supply for gold leaching is a critical component of the process, impacting the efficiency and environmental impact of gold extraction. Various methods of oxygen supply are available, each offering to different operational needs and scales:

  • Oxygen Generators: These systems generate oxygen directly at the mining site, which is particularly beneficial for remote locations where transporting oxygen can be challenging. They offer a continuous supply, crucial for large-scale operations, and reduce dependency on external sources.

  • Oxygen Cylinders: Portable and easy to use, these are ideal for smaller mining operations or areas where on-site oxygen generation isn’t feasible. They provide flexibility but require regular replacement or refilling.

  • Bulk Oxygen Delivery: Suitable for large-scale mining activities, this method involves the delivery of oxygen in large tanks. It’s efficient for operations that need large volumes of oxygen and have the infrastructure to transport, store and handle bulk oxygen.

  • Compressed Air Systems: A traditional method where compressed air is used for aeration. While less efficient in oxygen transfer compared to pure oxygen systems, it remains a common method due to its availability and lower technological requirements.

As indicated above, the problem of supply becomes more prevalent when it comes to mining in remote areas, as ensuring a steady supply of oxygen is a complex task. This is true for both large-scale and small-scale operations. Remote locations often lack infrastructure, making transport of supplies like bulk oxygen delivery or refilling the cylinders difficult. Oxygen generators are particularly useful in such settings due to their on-site generation capability.

In remote gold mining operations, where traditional oxygen supply methods can be challenging, the use of oxygen generators has become increasingly important. These generators provide a reliable source of oxygen, crucial for the cyanidation process. There are usually two types of oxygen generators in use:

  • PSA (Pressure Swing Adsorption) Oxygen Generators:
    • Efficient oxygen production from air.
    • Suitable for various operational scales.
    • Low maintenance and operational costs.

  • VPSA (Vacuum Pressure Swing Adsorption) Oxygen Generators:
    • Enhanced energy efficiency due to lower operating pressures.
    • Higher capital expenditure.
    • Ideal for high-volume oxygen needs in larger operations.

These systems provide an efficient oxygen supply on-site, overcoming logistical challenges and reducing supply transport costs. Furthermore, apart from autonomy in oxygen supply, onsite oxygen generation offer the ability to become unaffected by oxygen price fluctuations, as was the case during the pandemic of COVID 19, between 2020 and 2022. According to Future Market Insights the overall oxygen market is expected to increase from US$ 71,211.7 million in 2023 to US$ 152,323.1 million by 2033, mostly due to medical and other industrial use. A clear indication for the mining management to become independent of external oxygen supply. Additionally, the use of on-site oxygen generators supports not only gold extraction techniques, i.e. cyanidation, but also advances sustainable mining practices, such as reduction of CO2 emissions from transport. Oxygen can play also important role by destruction of residual free cyanide in slurry to the less toxic substances before safe deposition.

Gold mining operations in remote areas are characterized by their inadequate settings for access to infrastructure, which makes it challenging to meet the demand for essential resources like oxygen. Whether it is delivering large quantities such as bulk oxygen or using cylinders, there is a need for reliable transportation connections to industrial zones or oxygen production facilities, which often are located far away from the mines.

OXYMAT being one of the largest manufacturers, with more than 6000 worldwide installations of oxygen generators and systems, have tackled this by providing gold mines with solutions that suit their settings. Gold mines can be provided with either standalone oxygen generators or tailored made systems, such as frame-based solutions or containerized solutions.

Some of the key features of the standalone oxygen generators, known as the Twin-Tower include low energy consumption, power consumption in range 0.8 – 1.2 kW/m3 oxygen (depend on site conditions), low CO2 emission, heavy duty construction designed for rough conditions and industrial use. It is mounted on a skid or container and has a full compressed air system. The model comes in various oxygen production capacities in range 2 – 473 Nm3/h @ 92%.  

If oxygen lower output pressure is enough in range 2.5 – 3.5 bar physical, one can also choose the Nordic model which is manufactured in different variations. This model is highly regarded in the marine industry for its retrofitting capabilities, but for producing nitrogen. Some of its features include low energy consumption from 0.6 kW/Nm3, all pipes and valves are made of stainless steel (SS 316L), the model is sandblasted, and is powder coated.          

Learn more about OXYMAT generator here.

OXYMAT´s oxygen generators are tailored specifically for gold mining operations. Their design is sturdy and durable, perfect for withstanding the challenging conditions found in gold mining environments. Both models of generators offer plug and play installation.

Apart from offering standalone generators, OXYMAT offers a built-in-frame oxygen generation solutions for gold mines in capacities 1 – 30 tons oxygen per da. A type of installation that is in service across the globe, such as in Asia, Africa, Americas etc. Som of its key features include:

With complete PSA wiring inside of the skid is designed for fast and easy installation on site. System is prepared for a remote control and monitoring of process parameters via ethernet, or other interface connection requested by the customer.

Allows customer to choose the por­tion of oxygen for each of the leach­ing tanks silos to fine tune the process of the gold extraction from the ore.

Is designed for rough conditions – high temperatures, dusty, rainy environment of the mining environment. Minimum maintenance of the PSA generator gives easy and long-lasting operation for the personnel on site.

Process monitoring of feed air quality and produced oxygen serves as a protection of the PSA against breakdown as well as assurance that customer receives oxygen specified quality and quantity necessary for smooth and safe operation.

PSA build in standard container frames in different configurations custom made for the mining industrial needs.

OXYMAT intsallation model for gold mining. Learn more here about special installations.

In summary, oxygen is very important in gold mining, especially in the cyanidation process. The traditional methods of oxygen supply, like cylinders and bulk delivery, are not always feasible or sustainable, especially in remote areas.

On-site oxygen generators offer a solution that ensures steady and consistent oxygen supply, which is a key element for the effective cyanidation process.  

By using on-site oxygen generators, gold mines also promote eco-friendly practices, such as reduction of cyanide and CO2 emissions. A leading manufacturer, OXYMAT, offers tailored oxygen generator solutions specifically designed for gold mining. Their models, like the Twin-Tower and Nordic, prioritize low energy consumption, eco-friendliness, and durability in harsh conditions.

The systems come with advanced control systems, sturdy construction, and can be adjusted to various capacities and mining conditions. Frame-built design of these systems offers easy installation and operation, making them particularly suitable for remote mining operations.

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