Gold Ore Double-Impeller Leaching Agitation Tank: Working Principle, Core Advantages, and Selection Guide

In the cyanidation process for gold extraction, the leaching agitation tank is one of the core pieces of equipment that determines leaching efficiency and gold recovery. With the rapid development of China’s gold mining and beneficiation industry, the double-impeller leaching agitation tank has gradually replaced traditional single-impeller tanks, thanks to its excellent agitation performance, uniform aeration, and significant energy-saving advantages. It has become the mainstream choice for cyanidation leaching and carbon adsorption operations in gold mines. This article provides a comprehensive analysis of the working principle, structural features, core advantages, and selection considerations for the gold ore double-impeller leaching agitation tank.

1. What is a Double-Impeller Leaching Agitation Tank?

The double-impeller leaching agitation tank, also known as the SJ-type double-impeller leaching tank, is a piece of equipment specifically designed for the cyanidation gold extraction process, used for leaching and adsorption. The equipment features a double-layer impeller structure, with the motor, reducer, bearing housing, and agitation tank mounted concentrically on the same vertical axis, resulting in a compact design and small footprint. Compared with traditional single-impeller tanks, the double-layer impeller design provides more uniform pulp agitation, lower energy consumption, longer impeller service life due to rubber‑lined technology, and a multi‑direction aeration system that ensures uniform gas distribution.

This equipment is suitable for gold leaching, adsorption, and other mixing operations where the material has low specific gravity, low viscosity, slow settling speed, particle size of 90% passing 200 mesh, and pulp concentration below 45%.

2. Equipment Structure and Components

The double-impeller leaching agitation tank mainly consists of the following parts:

• Drive unit – includes motor, reducer, coupling, etc., to drive the impeller rotation.
• Agitation unit – includes the vertical shaft, upper impeller, and lower impeller, which are the core of the agitation operation.
• Tank body – the main container holding the pulp.
• Aeration system – delivers air to the bottom of the tank through a hollow shaft or bent pipes.

The two impellers are arranged vertically on the same main shaft, each consisting of four blades, with the upper blades offset by 45° from the lower ones. The impellers are rubber‑lined for excellent wear resistance and long service life. The main shaft is divided into upper and lower sections connected by positioning flanges, reducing the lifting height required and facilitating installation and maintenance.

3. Working Principle in Detail

The operation of the double-impeller leaching agitation tank proceeds as follows:

1. Top-to-bottom flow: Under the drag and agitation of the double impellers, the pulp flows from the centre of the tank from top to bottom.
2. Diffusion via baffles: After reaching the bottom, the pulp is diffused by peripheral damping plates to ensure uniform distribution.
3. Aeration and mixing: Compressed air is delivered through the hollow shaft or bent pipes to the bottom of the tank, where it mixes thoroughly with the pulp.
4. Upward circulation: The gas‑pulp mixture circulates upward under the action of the impellers, forming a uniform suspended slurry.
5. Bubble refinement: Large air bubbles are continuously broken down by the two impellers, dispersing into fine bubbles, which greatly increases the gas‑liquid contact area and enhances the cyanidation leaching reaction of gold.

This unique working flow ensures thorough mixing and reaction of pulp, reagents, and air within the tank, providing a strong guarantee for achieving high leaching rates.

4. Core Advantages and Features

Compared with traditional single-impeller leaching tanks, the double-impeller design offers the following significant advantages:

1. More uniform agitation and higher leaching recovery
The double-layer impeller creates stable pulp flow and homogeneous mixing, with consistent pulp density and particle size distribution throughout the tank, significantly improving cyanidation leaching efficiency and activated carbon adsorption rates.

2. Lower energy consumption and more economical operation
The large impeller diameter and low rotational speed reduce agitation power consumption. Compared with conventional tanks of the same size, power requirements are noticeably lower, enabling energy-saving operation.

3. More uniform aeration and better reaction
Air enters through the hollow transmission shaft and is evenly dispersed by the impeller blades, producing fine bubbles. The multi‑directional aeration scheme ensures uniform oxygen distribution in the pulp, providing an ample oxygen source for the cyanidation reaction.

4. Long service life and low maintenance costs
The impellers are lined with wear‑resistant rubber, and the low rotational speed results in minimal wear, extending service life. The compact structure also makes maintenance convenient.

5. Reduced carbon attrition and higher adsorption efficiency
The low shear speed of the impellers minimises the breakage and abrasion of activated carbon, improving carbon adsorption rates and gold recovery.

6. Compact structure and small footprint
The motor, reducer, bearing housing, and tank are mounted concentrically on the same vertical axis, saving plant floor space.

5. Wide Application Fields

The double-impeller leaching agitation tank is mainly used in the following areas:

• Gold mines – cyanidation leaching operations, and carbon‑in‑pulp (CIP) / carbon‑in‑leach (CIL) processes for carbon adsorption.
• Metallurgical industry – hydrometallurgical leaching of non‑ferrous metals.
• 化学産業 – mixing, stirring, and leaching of materials.
• Environmental protection – cyanide wastewater treatment.

In CIP/CIL circuits, the carbon adsorption tank is usually equipped with auxiliary equipment such as carbon retention screens and carbon lifting pumps.

6. Technical Parameters Reference

The following table shows typical technical parameters for some common models of the double-impeller leaching agitation tank:

Note: Effective volumes can range from 6 m³ up to 1740 m³; specific parameters vary by manufacturer and model.

7. Selection Guidelines

When selecting a double-impeller leaching agitation tank, users should consider the following factors:

1. Processing capacity – determine the required effective volume based on the daily throughput of the beneficiation plant.
2. 材料特性 – ore particle size, pulp density, specific gravity, viscosity, etc.
3. プロセスの要件 – whether for cyanidation leaching or carbon adsorption, and whether auxiliary equipment is needed.
4. 駆動方式 – generally a planetary cycloidal reducer drive, which is simple in structure and low in cost.
5. Aeration method – hollow shaft aeration or bent‑pipe aeration, chosen according to actual needs.

8. Maintenance and Care Recommendations

To ensure long‑term stable operation of the double-impeller leaching agitation tank, users are advised to follow these maintenance practices:

1. Pre‑start inspection: Run the tank empty before operation to check that all fasteners are secure, the main shaft rotates normally, seals are leak‑free, and there are no foreign objects obstructing the tank.
2. Temperature control: The tank can operate normally at temperatures up to 50°C; avoid exceeding this limit.
3. Regular servicing: Establish a regular maintenance schedule, including checking impeller wear, bearing lubrication, and drive unit condition.
4. Cleaning: After each shift, clean the tank and sleeves to remove residual material and keep the equipment clean.
5. Prompt troubleshooting: If problems such as uneven agitation or excessive vibration occur, investigate and address them immediately to prevent further damage.

The gold ore double-impeller leaching agitation tank, with its remarkable advantages of uniform agitation, low energy consumption, uniform aeration, and long service life, has become a key piece of equipment in the cyanidation leaching process for gold mines. Whether for new concentrator construction or retrofitting existing plants, proper selection, standardised operation, and regular maintenance will maximise the agitation and leaching efficiency of the equipment, helping mining enterprises improve gold recovery, reduce production costs, and achieve both economic and environmental benefits. As equipment continues to scale up and become more intelligent, the double-impeller leaching agitation tank will undoubtedly play an even more important role in China’s gold and non‑ferrous metals hydrometallurgical industry.