Hydrochloric Acid in Gold Mining: Applications, Storage & Dosing, and Best Practices

February 5, 2025

Gold mining operations rely on various chemicals to extract and process gold efficiently. Among these, hydrochloric acid (HCl) plays a critical role due to its chemical properties and versatility. In this article, we explore the uses of hydrochloric acid in gold mining, the considerations for its safe storage and dosing, and solutions to meet these requirements.

What Is Hydrochloric Acid Used for in Gold Mining?

Hydrochloric acid is a highly effective chemical used in several stages of gold mining and refining processes:

  1. Leaching and Dissolution:
    • Hydrochloric acid is often used in combination with other chemicals, such as chlorine, in leaching processes to dissolve gold from ore. This is particularly common in chloride leaching systems, which are an alternative to traditional cyanide-based methods.
  2. pH Control:
    • HCl is employed to adjust the pH levels in various chemical reactions involved in gold extraction and processing. Maintaining optimal pH levels ensures efficient chemical reactions and enhances gold recovery. It is also used in water treatment to balance the pH of the water on site.
  3. Cleaning and Descaling Equipment:
    • Hydrochloric acid is widely used to remove mineral scale and deposits from mining equipment and pipelines, ensuring operational efficiency and preventing blockages or equipment damage.
  4. Refining and Purification:
    • In gold refining, hydrochloric acid is used to dissolve impurities and separate pure gold from other metals.

How Is Hydrochloric Acid Stored on Mine Sites?

Proper storage of hydrochloric acid is essential to ensure safety, maintain chemical integrity, and comply with environmental regulations. Key considerations include:

  1. Material Compatibility:
    • HCl is highly corrosive and must be stored in tanks and containers made from materials resistant to acid corrosion.
  2. Secondary Containment:
    • Hydrochloric Acid must have secondary containment, so in the event there is a leak from the primary tank the secondary containment contains the chemical so there is no contamination of the environment or exposed hazard to operators.
  3. Ventilation:
    • Tanks storing HCl must have a means of scrubbing the HCl fumes before being released to atmosphere, as HCl fumes are highly corrosive and will corrode infrastructure and are harmful to people.
  4. Proximity to Operations:
    • Storage tanks should be strategically located near dosing and application areas to minimize the need for long-distance chemical transfer, which reduces risks and improves operational efficiency.

How Polymaster Tanks Store Hydrochloric Acid

Polymaster tanks are specifically designed to meet the demanding requirements of storing hydrochloric acid safely and effectively. Here are some features and benefits:

  1. High Chemical Resistance Material:
    • Polymaster processes its own raw material, with unique blends for compatibility with specific chemicals. Polymaster’s 7060 High-Density Polyethylene blend is fully compatible with Hydrochloric Acid and is validated by internal laboratory testing. This material is also UV Stabilised so the tanks are suitable to be located outside in full sun exposure.  Polymaster’s Tanks have a design life of 25 years. (put a link here to our design life statement).
  2. Customizable Designs:
    • These tanks are tailored for each specific site and application, such as fittings, venting systems, level instruments and controls. Dosing Systems and Unloading Control Panels can be easily integrated with the storage vessel.
  3. Secondary Containment Options:
    • Polymaster provides integrated secondary containment solutions, ensuring compliance with environmental regulations and enhancing safety. The Polymaster Self-Bunded Tank provides a minimum 110% integral bund capacity to comply with AS3780. (Put the link here to our Self-Bunded Tanks and Enclosed IBC Bund.).
  4. Durability and Longevity:
    • Designed to withstand the harsh conditions of mine sites, Polymaster tanks offer a long service life, reducing maintenance costs and downtime. With the Self-Bunded Tank, the bund tank completely encloses the internal tank so no rainwater can get in the bunded area, meaning you don’t have the hassle of having to treat contaminated rainwater. The UV Stabilised material makes it suitable for the harsh UV conditions of mine sites and eliminating the need of UV coating the tank.
  5. Safety Features (HCl Fumes):
    • Polymaster’s storage solution for HCl includes a wet scrubber assembly for the corrosive fumes. The tank is completely sealed (sealed manway and level indicator) and fumes in the tank vent to a separate 200L scrubber tank where the fumes are scrubbed. There is also a one-way vent fitted to the tank to allow air into the tank, so a suction is not created in the tank.
Chemical Tank with wet scrubber
Example of a Chemical Tank with a wet scrubber attached.

Polymaster Dosing Systems for Hydrochloric Acid

Polymaster dosing systems are designed to deliver precise and safe dosing of hydrochloric acid in gold mining operations. These systems ensure accurate chemical application while minimizing risks to personnel and equipment. Key features of Polymaster dosing systems include:

  1. Precision Dosing:
    • Polymaster dosing systems provide highly accurate chemical dosing, ensuring optimal reaction conditions and reducing waste.
  2. Automated Controls:
    • Advanced control systems allow for automated dosing, reducing the need for manual handling and enhancing operational efficiency.
  3. Corrosion-Resistant Components:
    • All components of the dosing system, including pumps, valves, and fittings, are made from materials designed to withstand the corrosive nature of hydrochloric acid. Typical pipe material is Sch80 U-PVC and seal material is Viton/FKM.
  4. Easy Integration:
    • Polymaster dosing systems can be seamlessly integrated with existing mining operations, offering flexible installation options. Typically all power and signal cables are pre-wired to a junction box. Polymaster can also the mine sites specifications.
An example of a chemical tank with the power and signal cables pre-wired into a junction box.

 

  1. Safety Enhancements:
    • Built-in safety features, such as leak detection sensors and emergency shut-off mechanisms (e.g. actuated valves or power cut-off), provide additional protection for personnel and equipment.
  2. Customisable Solutions:
    • Polymaster offers tailored dosing systems to meet the specific requirements of gold mining sites, ensuring compatibility with unique operational needs.

 

Sulphuric Acid Dosing System
pH Adjustment – Chemical Dosing

Things to Consider for Storing and Dosing Hydrochloric Acid – I’m not sure if we should have this section, think it maybe should be removed?

When storing and dosing hydrochloric acid on gold mine sites, the following considerations are crucial:

  1. Personnel Training:
    • Staff should be trained on the safe handling, storage, and dosing of HCl, including emergency response procedures.
  2. Proper Labeling and Signage:
    • Tanks and storage areas must be clearly labeled with hazard signs and information to warn personnel of the chemical’s corrosive properties.
  3. Regular Maintenance and Inspections:
    • Tanks and associated equipment should be regularly inspected for leaks, corrosion, or structural issues to prevent accidents.
  4. Dosing Systems:
    • Automated dosing systems can improve precision and safety by reducing manual handling of hydrochloric acid.
  5. Emergency Preparedness:
    • Sites should have spill kits, eyewash stations, and neutralizing agents readily available to manage potential accidents.

Conclusion

Hydrochloric acid plays a vital role in gold mining operations, from ore processing to equipment maintenance. However, its highly corrosive nature demands stringent storage and handling protocols to ensure safety and efficiency. Polymaster’s solutions provide a reliable solution for storing and dosing hydrochloric acid, offering durability, chemical resistance, and customizable features tailored to the unique needs of mining sites. By adhering to best practices for storage and dosing, mining operations can maximize the benefits of hydrochloric acid while minimising risks to personnel and the environment.

Mining Companies that have trusted Polymaster for Hydrochloric Acid Solutions.