Double-Impeller Leaching Tank: Essential Equipment for Efficient Gold Extraction

A double-impeller leaching agitator tank is an efficient mixing device designed for cyanide leaching in the extraction of precious metals like gold and silver. It features upper and lower impellers and is typically equipped with an axial flow guide, which enhances slurry mixing, improves oxygen utilization, and accelerates gold leaching—making it essential in modern CIP and CIL processes.

Compared with traditional agitators, Xinhai’s self-developed double-impeller leaching tank handles slurries up to -200 mesh and under 45% concentration. It combines leaching and carbon adsorption and is also suitable for stirring and leaching in metallurgy, chemicals, and light industries.

In this article, we will explore the core structure and working principle of Xinhai’s double-impeller agitator tank, analyze its technical advantages in gold cyanidation, and summarize the types of ores and process conditions it is best suited for. Read on to gain a comprehensive understanding of this equipment and discover how it can serve as a professional reference for your project planning and equipment selection.

01The Core Structure and Working Principle of the Double-Impeller Leaching Agitation Tank

The double-impeller leaching tank typically consists of the following components: tank body, agitation device, baffle plate, transmission device, shaft sealing system, and other supporting parts.

Tank Body: Made of stainless steel or lined with corrosion-resistant materials, the tank is cylindrical in shape with either a conical or flat bottom. Baffles are installed along the inner wall to enhance the mixing effect.

Agitation Device: It features a dual-impeller system, with impellers—typically of paddle or turbine design—working in tandem to achieve efficient material mixing. The impellers are centrally mounted within the tank and driven by a transmission system.

Baffle Plate: Typically made from stainless steel (e.g., 304, 316L) or non-metallic materials (e.g., PVC, PTFE), the baffle disrupts the vortex generated by the impellers. This improves mixing uniformity, reduces energy loss caused by vortex formation, and helps prevent solid particle sedimentation.

Transmission Device: Comprising a motor, reducer, and coupling, this system transmits power and regulates the rotation speed of the impellers.

Shaft Sealing Device: Uses either packing seals or mechanical seals to prevent material leakage during operation.

02Technical Advantages of the Double-Impeller Leaching Agitation Tank

– Using Gold Ore Cyanide Leaching as an Example

The cyanide leaching tank plays a crucial role in the gold extraction process. It provides a stable and controllable reaction environment that facilitates full contact and reaction between the leaching agent and the ore. This significantly improves both the leaching efficiency and gold recovery rate, while also ensuring the economic viability and sustainability of the overall beneficiation operation.

Below are 4 key technical advantages of the double-impeller agitating leaching tank in the cyanide leaching process of gold ore:

1. Enhanced Cyanide Leaching And Carbon Adsorption Rates

The dual-impeller design increases slurry circulation paths and ensures uniform distribution of slurry concentration and fineness. This enables greater exposure of gold particles to the reaction medium, thereby improving the cyanide leaching rate and carbon adsorption efficiency.

2. High Oxygen Utilization

Oxygen is introduced into the gold leaching tanks through a hollow shaft at the bottom. This design extends oxygen residence time in the slurry, ensures even distribution, and creates fine bubbles, all of which enhance oxygen utilization during the leaching process.

3. Energy Efficiency And Reduced Wear

The high efficiency agitation tank features a compact structure for easy maintenance.

The impellers are lined with wear-resistant rubber, extending service life.

Large-diameter impellers operate at low speeds, reducing power consumption and minimizing carbon wear—making the system more energy-efficient than traditional single-impeller designs.

4. Prevention Of Ore Settling And Dead Zones

The wide agitation range ensures more uniform slurry distribution, effectively preventing ore particles from settling at the bottom or accumulating in dead zones.

This design is especially well-suited for handling difficult-to-leach ores such as clay-rich ores and those with high mud content.

03Applicable Ore Types and Processes for the Leaching Agitation Tank

The Xinhai double-impeller leaching agitation tank is widely used across various gold ore types due to its excellent mixing performance, high leaching efficiency, and operational sustainability. It is particularly effective in handling the following 5 types of complex ores:

1. Oxidized gold ores with high clay content

2. Fine-grained disseminated gold ores

3. Sulfide-encapsulated or arsenic-bearing gold ores

4. Complex ores with heavy metal impurities

5. Ultra-low-grade gold ores

In addition to its broad ore adaptability, the double-impeller leaching agitation tank is also applicable in a variety of process flows, including:

1. CIL (Carbon-in-Leach) process

2. CIP (Carbon-in-Pulp) process

3. Combined processes involving oxidation pretreatment followed by cyanidation

4. Pre-treatment leaching stages prior to heap leaching

04Specific Case Studies

1. Sudan 300t/d Gold Ore Beneficiation Project

Project Background:

This project processes gold tailings with fine particle size and a gold grade of 4.7 g/t. Since the raw ore is already finely ground, no crushing is required.

Process Flow:

The adopted process includes pre-screening, one-stage closed-circuit grinding and classification, thickening, cyanide leaching, desorption electrolysis, smelting, and tailings pressure filtration and dewatering.

Equipment Application:

During the cyanide leaching stage, Xinhai's double-impeller high-efficiency leaching agitation tank is employed for both leaching and carbon adsorption. The system also includes Roots blower aeration and sodium cyanide (NaCN) dosing to ensure thorough mixing and reaction between the slurry, reagents, and air.

Project Results:

The gold leaching rate reached 95.7%, the carbon adsorption rate was 99%, and the overall gold recovery rate was as high as 91.93%.

2. Iran 300t/d Gold Ore Beneficiation Project

Project Background:

The ores treated in this project include both oxidized and sulfide gold ores, with average gold grades of 2.5 g/t and 3.39 g/t, respectively.

Equipment Application:

Xinhai designed a combined process of alkali pretreatment and cyanide leaching. The double-impeller leaching agitation tank is used for both the pretreatment and leaching stages, ensuring uniform mixing and improved reaction efficiency.

Project Achievements:

With the optimized agitation system, the leaching time for oxidized ore was 32 hours and for sulfide ore 24 hours. The final gold ingot purity exceeded 99.5%.

Summary

In conclusion, the double-impeller leaching agitation tank offers outstanding process efficiency and economic benefits in the gold cyanidation process. By enhancing gold recovery, lowering cyanide consumption, and promoting sustainable production, it has become a preferred choice in modern gold beneficiation plants.

If you would like to learn more about this equipment or receive a customized solution tailored to your specific mineral processing needs, please feel free to contact XinHai group. Our team is ready to provide you with professional technical support and dedicated service.