The Beginner's Guide to Gravity Separation in 2024

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(shaking table for gravity separation processing)

There are extremely rich mineral resources in nature. Mineral processing is the process of separating useful minerals and gangue minerals through various separation methods and equipment according to the difference in physical or chemical properties of ore.

Depending on the type of ore and the requirements for the final product, different separation methods can be adopted in practice. Commonly used separation methods include gravity separation, magnetic separation and flotation separation. 

This article focuses on the gravity separation method, including the definition, basic principles, classification, advantages and application of the gravity separation method, and the commonly used equipment.

01

What Is the Gravity Separation?

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Different minerals have different densities and properties. When mineral particles of different sizes and densities move in a flowing medium, their state of motion is different.

Gravity separation is due to the difference in density between mineral particles, and they are subjected to different gravity, fluid power and other mechanical forces in the moving medium and present different motion states, so as to realize the process of separating mineral particles.

Basic Principle of Gravity Separation

The essence of gravity separation is the three basic processes of loosening, layering and separation.

1. Loosening

The materials in the separating process are pushed and dispersed in the moving medium due to the action of gravity, fluid power and other mechanical forces.

2. Layering

After the mineral particles are dispersed, due to the difference in their density and particle size, there will be different movement trajectories in the sorting equipment, and at this time the mineral particles will be layered and transferred.

3. Separation

The delamination of the mineral particles are transported by the moving medium to achieve the result of separation.

In practice, the three processes of loosening, layering and separation occur almost simultaneously. But loosening is the premise, which is the condition for the layering and separation of mineral particles, layering is the intermediate process, and separation is the purpose and result of loosening and layering.

02

Classification of the Gravity Separation

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According to its basic principle, gravity separation can be divided into two types: separating process by particle size and separating process by density.

1.Separating process by particle size. 

It can be divided into two types: classification and mineral washing.

 

(hydrocyclone for mineral classification)

(1) Classification

Classification can be divided into hydraulic classification and wind classification according to the different media. But in the separation process, the most commonly used is hydraulic classification. Here mainly introduces hydraulic classification.

Hydraulic classification refers to the process by which mineral particles in different moving media, according to their different sedimentation speeds, can divide mineral particles of wide particle size into narrow particle size.

The process of hydraulic classification and screening are somewhat similar. But there are fundamental differences.

Hydraulic classification is according to the sedimentation rate of mineral particles to classify it. The density and even shape of mineral particles will have an impact on the classification. It is generally used to process ore particles less than 2-3 mm, and the processing efficiency is high; Screening is strictly according to the particle size of mineral particles grading, generally used to process materials larger than 2-3 mm, and its processing efficiency is also lower than hydraulic classification.

(2) Mineral washing

Mineral washing is generally suitable for ore that is bound by clay. It refers to the method of separating and removing clay wrapped in a mixture of useful minerals. In essence, it is also a re-separation process that separates the mineral particle size.

Mineral washing mainly includes two processes: the crushing and dispersion of clay' and the separation of useful minerals and clay.

Crushing and dispersing of clay refers to the process of dispersing clay that is mixed with useful minerals by soaking and rinsing with water, or mechanical stirring.

The separation of useful minerals and clay refers to the separation of mineral sludge from clay by means such as hydraulic classification.

2. Separating the process by density. 

It can be divided into jigging separation, shaking table separation, chute separation and heavy media separation.

(1) Jigging separation

Jigging separation refers to the process of using a flow of vertical alternating media (usually water or air) caused by strong vibrations to stratify mineral particles' according to relative density, and collect light and heavy minerals separately through appropriate methods to achieve the purpose of separation. This method is usually used to process coarse-grained ore with large density differences..

Jiggering separation can be divided into hydraulic jigging, wind jigging and heavy media jigging according to the different media used. At present, hydraulic jigging is commonly used in mineral processing plants.

(2) Shaking table separation

The process of separation on a shaking table takes place on a wide inclined bed. And the water fed by the sink flows to the inclined bed surface and is covered to form a thin layer of uniform beveled water.

At this time, the slurry is fed into the bed surface of reciprocating rocking, and the mineral particles will be layered according to density under the action of gravity, water flow force and mechanical force of bed shaking.

At the same time, mineral particles of different particle sizes move laterally and longitudinally along the inclined bed surface under the action of various forces.

Due to the different particle density, its movement trajectory is also different. Finally, the ore grains of different densities are distributed in a fan shape on the bed surface and thus separated.

(3) Chute separation

 

(spiral-chute-for-gravity-separation-processing)

Chute separation refers to the method of separating mineral particles in different states of motion in the water flow flowing along the inclined plane. 

In the chute, mineral particles of different densities are layered by a combination of gravity, water flow and friction with the bottom of the chute.

The result of stratification is that dense mineral particles are concentrated in the lower layer, moving forward along the trough at a lower speed, sending out the trough at the same time as feeding the ore, or remaining at the bottom of the trough; Mineral particles with low density are distributed in the upper layers and carried away by the current at a large speed.

In this way, mineral particles of different densities are separated in the chute.

(4) Heavy media separation

Heavy media separation refers to the mineral processing method in which mineral particles are separated according to density in a medium with a density greater than water.

The principle of heavy media separation is Archimedes' law. That is, the object will be cared for in the medium, and the magnitude of the buoyancy force is equal to the weight of the same volume medium discharged by the object.

Suppose there are two kinds of minerals, light and heavy, the density of light minerals is ρ1, the density of heavy minerals ρ2, and the density ρ of heavy media should be between light and heavy minerals, that is, ρ1<ρ<ρ2. In such a medium, separating can be carried out efficiently.

03

The Advantages and Application of the Gravity Separation

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1. Advantages

Compared with other separation methods, gravity separation has the following advantages:

(1) The gravity separation method has a wide range of applications, and the particle size range of the material that can be processed is wide, up to several hundred millimeters in thickness and up to 0.01 mm in fine;

(2) The structure of the resorting equipment is simple, and the operation is convenient and reliable; Low production cost and cost-effective;

(3) The products treated by the gravity separation method are easy to dehydrate and have less pollution to the environment.

2. Application

The gravity separation method is widely used in the separating of precious metal ores (gold, platinum, etc.), rare metal ores (tungsten, tin, titanium, zirconium, niobium, tantalum, etc.), ferrous metal ores (iron, manganese, etc.) and coal. In addition to this, it can also be used for pre-separation of non-ferrous metal ores (lead, zinc, etc.) and processing of scrap metal ores (diamond, asbestos, etc.).

In terms of processing material size, the gravity separation method can process materials as small as 0.01 mm, such as tungsten ore, tin ore sludge, and can also process materials as large as 200 mm, such as coal.

04

6 Commonly Used Gravity Separation Equipment

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Because of the many advantages of the gravity separation method, and its wide applicability, it has been paid more and more attention at home and abroad in recent years. And a series of efficient and economical equipment have been produced in the field . Here are some of the most widely used gravity separation devices:

1.Diaphragm jig

(1) Working principle

The diaphragm jig is divided into two types: left and right jig, and its sieve is fixed.

Diaphragm jigs can be used to separate both fine-grained and coarse materials. The maximum feed grain size is 6-8mm. However, in some special cases of mineral sand, the maximum feed ore particle size can reach 12mm.

(2) Scope of application

It is suitable for separating gold, iron, tin, tungsten, titanium, coal and other minerals, especially in the field of manganese ore separation has been widely used.

2. Centrifugal separator

 

(centrifugal separator for gravity separation)

(1) Working principle

The centrifugal separator is also a gravity separation equipment. It generates a large centrifugal force through high-speed rotation, intensifies the reseparation process, and enables the efficient recovery of fine ore grains.

(2) Scope of application

Centrifugal separators are suitable for the recovery of monomer gold in vein gold ore, and can also be widely used to recover monomer gold in other metal minerals.

3. Sawtooth wave jig

 

(sawtooth wave jig for gravity separation)

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The Sawtooth wave jig is one of the modern separating equipment, which has been improved on the basis of the traditional jig.

(1) Working principle

Traditional jigs are mostly eccentric driven by circumferential eccentricities, and their jig pulsation curves are sinusoidal waveforms. Since the rising and falling water flow speed and time generated by the diaphragm movement are basically the same, it is not conducive to the stratification of ore particles according to the proportion gravity, which affects the selection efficiency of the equipment.

The pulsation curve of the sagging wave jig is zigzag, which makes the upward flow faster than the downward flow. It overcomes the shortcomings of traditional jigs, allowing heavy proportions of ore grains to settle adequately. This greatly improves the sorting capacity of the equipment and the recovery rate of minerals.

(2) Scope of application

Sawtooth wave jig are widely used in the selection of minerals such as placer gold, iron, tin, titanium, coal and so on, especially in the field of mineral processing of barite.

4. XS shaking table

 

(shaking table for gravity separation)

(1) Working principle

XS shaker is mainly composed of bedhead, motor, sloper, bed surface, mining tank, sink, back strip and lubrication system handle.

The reciprocating movement of this shaking table is achieved by means of a crank linkage drive. The motor drives the crankshaft to rotate through the belt, and the joystick moves up and down.

When the joystick moves downward, the toggle plate pushes the rear axle and the reciprocating rod to move back, the spring is compressed, and the bed surface will also do backward movement because the bed surface is connected to the linkage seat and the reciprocating bar; Prevent the bed surface from moving forward when the stick moves upwards.

(2) Scope of application

XS shaking table is officially used in the separation of tungsten, tin, gold, tantalum, niobium and other rare and precious metal ores, and can also be used for iron, manganese and coal ore processing.

5.XY shaking table

(1) Device characteristics

The XY shaking table works similarly to the XS shaking table. It has some other features:

(1) The shaking bed surface is flat, strong and durable, not easy to deform'Easy for local repair; Good corrosion resistance;

(2) The bedside device has fewer vulnerable parts and is not easy to leak oil;

(3) The bedside movement is asymmetrical, has a wide adjustment range, and can be applied to different feed particle sizes.

(2) Scope of application

XY shaker is suitable for the separating of non-ferrous metals such as tungsten, lead, tin, gold, ferrous metals and rare earths.

6. BLL FRP spiral chute

(spiral chute for gravity separation)

(1) Working principle

In the spiral chute, the mineral sand is transported by a sand pump to the two feed ports at the top of the spiral, and water is added to adjust the slurry concentration. In the process of swirling down from a high place, the slurry will produce a centrifugal force, so that the mineral particles with different densities and forces will produce different states of motion, and the minerals will be separated.

The concentrate flows into the concentrate hopper, and the tailings flow into the tailings hopper to separate the minerals.

(2) Scope of application

FRP spiral chute is suitable for sorting tungsten, lead, tin, gold, tantalum, niobium, coal, rutile, zircon and other fine-grained minerals and minerals with small specific gravity.

05

Summary

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This article briefly understands the gravity separation method by introducing the concept, basic principles, classification, advantages and applications of the gravity separation method, as well as several main gravity separation equipment. Up to now, new technologies and new equipment for gravity separation continue to appear, and the gravity separation process has taken on a new look. Welcome to click the chat button to learn more about gravity separation.

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The gravity separation method has the advantages of low cost, environmental friendliness, and simple operation, making it an important method for the processing and production of various minerals. Gravity separation, also known as gravity concentration or gravity separation for short, mainly uses gravity to separate minerals with different densities. This method relies on the principle that minerals with a higher density will settle under the force of gravity faster than less dense minerals. The following will introduce four common mineral gravity separation methods for you, namely: jigging gravity separation, shaking table gravity separation, spiral chute gravity separation and dense medium separation.

Use the table of contents below to navigate through the guide:

• 01

  Jigging gravity separation method

• 02

  Shaker gravity separation method

• 03

  Spiral chute gravity separation method

• 04

  Dense medium separation method

01

Jigging gravity separation method

Jig gravity separation of particles by density by pulsating water flow. Heavier particles sink to the bottom more quickly, while lighter particles rise to the top. A jig is a gravity separation device consisting of a container or trough filled with a layer of granules. The oscillating action creates a pulsating water flow that stratifies the particles according to their density.

The process of jigging reselection includes the following steps:

1. Pretreatment: first crush and grind the ore or material into proper size.

2. Gravity separation: The crushed material is introduced into the gravity separation tank to generate pulsating water flow. Gravity separators are usually equipped with screens or grids at the bottom to prevent the bed of particles from being washed away during pulsation.

3. Stratification: As the pulsating water flows through the particle layer, heavier and denser particles sink to the bottom more quickly, while lighter particles are carried upward.

4. Collection: According to the density of the particles and their position in the stratified bed, the separated particles are collected from different positions of the jig.

Jig gravity separation method is effective at handling particles of various sizes and can be used to concentrate valuable minerals of various densities. It is especially suitable for processing coarse-grained ores or ores with high density contrast, such as gold, tin, tungsten and iron ore.

02

Shaker gravity separation method

A shaker consists of a flat, inclined surface, usually rectangular, mounted on a support structure. The table generates reciprocating motion through horizontal shaking or vibration. This shaking action stratifies the particles according to density and size, separating heavier mineral particles from lighter host rock material.

The process of gravity separation using a shaker is as follows:

1. Pretreatment: first crush and grind the ore into proper size.

2. Adjust the shaker: Place the prepared materials on the shaker. The surface of the shaking table is covered with transverse grooves or ridge-like structures to fix and trap heavier mineral particles.

3. Shaking: The table starts to move, usually through mechanical devices or vibration. Shaking moves the pellet laterally across the table.

4. Stratification: As the particles move across the table, they are stratified according to density and size. Heavier particles sink to the bottom and are trapped by the grooves, while lighter particles are carried away by the flowing water.

5. Collection: The separated minerals are collected from different positions on the table, depending on their density and position in the stratified bed.

The shaking table is used in the separation of ores with a wide range of particle sizes, and it is usually used to process precious metals such as gold, silver and platinum group metals. Because it does not require the use of chemical reagents or high energy inputs, the simplicity of design and ease of operation make it the main choice for medium to large scale processing plants.

03

Spiral chute gravity separation method

Spiral chute gravity separation is a gravity concentration method that uses a spiral chute for separation. Spiral chute is a equipment commonly used to separate particles according to their density differences. This method is usually used to process fine-grained ores, especially for ores containing fine minerals, and has a better separation effect.

The process of spiral chute gravity separation is as follows:

1. Pretreatment: First crush and grind the ore into proper size.

2. Feeding: Put the prepared ore evenly into the feeding port of the spiral chute.

3. Movement: In the spiral chute, the ore slides down along the spiral chute wall. Due to the helical design of the trough, the particles are separated under the action of centrifugal force and gravity.

4. Stratification: The heavier ore will move outward and settle to the bottom of the tank to form a rich ore layer, while the lighter gangue will move closer to the tank wall to form a tailings layer.

5. Collection: The separated rich ore and tailings are collected from different positions of the spiral chute.

Spiral chute gravity separation can be used to process ore containing fine-grained minerals, especially for the separation of fine-grained minerals in ore. It is commonly used to process ores such as gold, tin, iron, chromium, lead, zirconium and tungsten.

04

Dense medium separation method

In dense media separation, a dense medium (usually a fine-grained ferrosilicate or magnetite suspension) is used to form an intermediate density fluid. Minerals with a higher density will sink in this heavy medium, while minerals with a lower density will float. This technology is widely used in the methods of pre-selection, upgrading of ore grade and recovery of valuable minerals from different ore deposits.

The dense medium separation process is as follows:

1. Feed material preparation: ore or mineral-containing materials are crushed and ground.

2. Dense medium preparation: prepare dense medium by suspending fine particles of ferrosilicate or magnetite in water.

3. Immersion: Immerse the ore in a dense medium. Minerals with a higher density will sink and become trapped in the heavy medium, while minerals with a lower density will float and remain in the lighter part.

4. Separation: The dense medium is then subjected to various technical treatments to separate the two fractions according to density. In a heavy medium cyclone, heavy medium is pumped through the cyclone and the denser and lighter fractions are separated by centrifugal force.

The density media separation process is especially suitable for separating minerals with large differences in density. It is commonly used to process diamonds, coal, iron ore and certain base metal ores.

The above content is about four commonly used gravity separation methods: jigging gravity separation, shaker gravity separation, spiral chute gravity separation and dense medium separation. The selection of gravity separation technology should be based on the type and characteristics of the ore. When separating ore with complex components, it is necessary to combine other beneficiation methods other than gravity separation, such as magnetic separation and flotation. Xinhai Mining suggested to conduct mineral processing test in order to determine the appropriate gravity separation process and equipment to improve the mineral processing efficiency and concentrate recovery rate.

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