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A Comprehensive Guide to the Operation of Thickener

EssowEssow Oct 28, 2023Oct 28, 2023 719719
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Mining thickener plays a critical role in the efficient operation of mineral processing plants. It is a vital component of the process that separates and concentrates valuable minerals from the ore slurry. This article aims to provide a comprehensive understanding of the operation of mining thickener, highlighting its importance, key components, operational considerations, and maintenance requirements.

01 Thickener Components

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Mining thickener consists of several key components that work together to facilitate the separation and concentration of solid particles from the ore slurry. Here's a closer look at the main components of a mining thickener:

1. Tank or Basin

The tank or basin serves as the main vessel where the settling of solid particles takes place. It is a large, cylindrical or rectangular container that provides sufficient space for the slurry to settle and allows for the separation of clarified liquid.

2. Feedwell

The feedwell is located at the center of the thickener tank and serves as the entry point for the ore slurry. Its primary function is to evenly distribute the incoming slurry across the surface of the thickener, ensuring uniform settling and minimizing turbulence.

3. Rake Arms

Rake arms are mechanical devices equipped with rake blades that rotate slowly inside the thickener tank. The primary role of the rake arms is to move the settled solids, known as the underflow or thickened slurry, towards the center of the tank for discharge.

4. Discharge Cone

Positioned at the center of the thickener tank, the discharge cone collects the underflow from the rake arms and directs it towards the underflow outlet. It helps guide the thickened slurry to ensure a controlled and efficient discharge.

5. Underflow Outlet

The underflow outlet is located at the bottom of the thickener tank and serves as the point of withdrawal for the settled solids. It is designed to allow the controlled removal of the thickened slurry, which contains the concentrated mass of valuable minerals.

6. Overflow Launder

The overflow launder is responsible for collecting and directing the clarified liquid, also known as the supernatant or clarified solution, towards the overflow outlet. It ensures that the liquid phase is effectively separated from the settled solids and can be discharged or further processed.

7. Drive Mechanism

The drive mechanism provides the necessary rotational movement to the rake arms. It typically consists of a motor, gearbox, and associated mechanical components that enable the slow and continuous rotation of the rake arms, facilitating the movement of settled solids.

8. Control System

A control system is essential for monitoring and regulating the operation of the mining thickener. It allows operators to adjust parameters such as rake speed, underflow density, and overflow clarity, ensuring optimal thickener performance and efficient solid-liquid separation.

9. Support Structure

The thickener's support structure provides stability and structural integrity to the entire equipment. It is designed to withstand the weight of the thickener components, the slurry, and any additional loads imposed during operation.

Thickener components.jpg

(Thickener components)

02 Working Principles of Thickeners

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The operation of a mining thickener involves several fundamental principles:

1. Gravity Settling

Mining thickeners rely on the force of gravity to promote the settling of solid particles within the thickener tank. When the ore slurry enters the tank through the feedwell, the solid particles, heavier than the liquid phase, start to settle under the influence of gravity.

2. Hindered Settling

Hindered settling refers to the phenomenon where the settling of solid particles is impeded due to the presence of other particles or the interaction with the liquid phase. In mining thickeners, hindered settling occurs as particles encounter and interact with each other, creating resistance to settling.

3. Feed Distribution

The feedwell of the thickener is responsible for evenly distributing the incoming slurry across the surface of the thickener tank. This distribution helps prevent localized settling and ensures uniform particle settling throughout the tank.

4. Particle Aggregation

In order to enhance settling efficiency, mining thickeners often employ the use of flocculants or settling aids. These chemicals promote particle aggregation by causing the fine particles to clump together, forming larger and denser flocs. Aggregated particles settle more rapidly due to increased effective size and weight.

5. Rake Mechanism

The rake mechanism, typically equipped with rake arms and blades, is responsible for slowly rotating and moving the settled solids towards the center of the thickener tank. The rake arms continuously sweep the settled particles and direct them towards the discharge cone for removal.

6. Underflow Discharge

The settled solids, also known as the underflow or thickened slurry, collect in the center of the thickener tank and are discharged through the underflow outlet. The controlled withdrawal of the underflow ensures the removal of the concentrated mass of valuable minerals from the thickener.

7. Clarified Liquid Overflow

As the solid particles settle to the bottom, the clarified liquid rises to the top, forming an overflow layer. The clarified liquid, also called the supernatant or clarified solution, is directed towards the overflow launder and discharged from the thickener for further processing or recycling.

8. Control and Optimization

Efficient operation of mining thickeners requires careful control and optimization. Operators adjust parameters such as feed rate, rake speed, flocculant dosage, and underflow density to achieve the desired separation efficiency and maximize mineral recovery. Regular monitoring and adjustment of these parameters are essential for optimal thickener performance.

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(Thickeners in a gold plant)

03 Optimal Operation and Maintenance

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Optimal operation and maintenance of mining thickeners are essential to ensure their efficient performance, maximize mineral recovery, and extend equipment lifespan. Here are some key considerations for optimal operation and maintenance:

1. Monitoring and Control

Regular monitoring of key parameters such as slurry feed rate, underflow density, overflow clarity, and rake speed is crucial for optimal thickener operation. Automated control systems or manual adjustments can be employed to maintain desired operating conditions and achieve efficient solid-liquid separation.

2. Feedwell Optimization

The design and operation of the feedwell significantly impact the performance of a mining thickener. Optimizing the feedwell geometry, distribution baffles, and flow patterns can ensure even distribution of the slurry and minimize turbulence, promoting optimal settling conditions.

3. Flocculant Dosage and Mixing

Flocculants are often used to enhance particle aggregation and settling efficiency in thickeners. Proper dosing and mixing of flocculants are critical for achieving optimal performance. Regular monitoring and adjustment of flocculant dosage ensure effective particle flocculation without excessive use, which can lead to operational issues.

4. Rake and Blade Maintenance

The rake arms and blades in a thickener require regular inspection and maintenance. Worn-out or damaged blades can affect the movement of settled solids, leading to uneven distribution and reduced efficiency. Routine inspection, cleaning, and replacement of rake components are necessary to maintain optimal thickener operation.

5. Overflow and Underflow Management

Monitoring the clarity of the overflow and density of the underflow is important for assessing thickener performance. Adjustments in the overflow launder design, froth control devices, or underflow discharge mechanisms may be necessary to optimize the separation efficiency and prevent the loss of valuable minerals.

6. Regular Sludge Removal

Over time, accumulated sludge or sediment at the bottom of the thickener can affect its performance. Regular removal of sludge through manual or automated methods is crucial to prevent build-up, maintain proper tank capacity, and ensure efficient settling of solid particles.

7. Lubrication and Mechanical Maintenance

Proper lubrication of mechanical components, such as the drive mechanism and bearing assemblies, is essential for smooth operation and to prevent equipment failures. Regular inspection, cleaning, and maintenance of mechanical parts ensure optimal performance and extend the lifespan of the thickener.

8. Training and Operator Competence

Providing comprehensive training to operators and ensuring their competence in operating and maintaining thickeners is vital. Operators should understand the thickener's functionality, control systems, and troubleshooting techniques to promptly address any operational issues and optimize performance.

9. Documentation and Record-Keeping

Maintaining accurate documentation of maintenance activities, operational parameters, and performance data is valuable for analyzing trends, identifying potential improvements, and ensuring compliance with regulatory requirements. It also aids in troubleshooting and facilitates historical reference for future maintenance and operational decisions.

Thickeners in a gold plant.jpg

(Thickeners)

04Conclusion

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Mining thickeners play a critical role in the mineral processing industry by facilitating the separation and concentration of solids from liquids. Understanding the components and working principles of these thickeners is vital for their efficient operation. By considering factors such as feed distribution, rake design, flocculant addition, underflow discharge, and monitoring, mining companies can optimize the performance of their thickeners, ensuring higher productivity and cost-effectiveness in their operations.

 


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