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What Are Rock Crushers and How Do They Work?
Crushers are key equipment in mining, construction and aggregate industries. They break large rocks, ore, or other materials into smaller, more usable pieces. This equipment reduces the material by means of compressive force, impact, attrition or shear that are specific for the type of crusher being used. The main function of a rock crusher is to generate particles of similar sizes. These particles can be further purified for use in other applications, including road construction, building materials, and raw materials for other industries.
The crushing process is commonly conducted in several stages. Each stage of the crushing process implements a different type of crusher to gradually reduce the size of the material. The first step is crushing the material by using larger crushers that can reduce the material into smaller sizes that will be used in the next stage. Following this, the secondary and tertiary stages are employed to further reduce the particle size using smaller crushers until the desired output is achieved. During the process, screens are utilized in order to segregate the crushed material into various size fractions. This guarantees that the end result has the needed specifications.
The crushing process is commonly conducted in several stages. Each stage of the crushing process implements a different type of crusher to gradually reduce the size of the material. The first step is crushing the material by using larger crushers that can reduce the material into smaller sizes that will be used in the next stage. Following this, the secondary and tertiary stages are employed to further reduce the particle size using smaller crushers until the desired output is achieved. During the process, screens are utilized in order to segregate the crushed material into various size fractions. This guarantees that the end result has the needed specifications.
Crushing Methods: Compression, Impact, Attrition, and Shear
● Compression Crushing: Compression crushing, also known as compressive force, applies a compressive force to the material between two surfaces until it breaks. This way is frequently applied in jaw crushers and cone crushers. In jaw crushers, the material is squeezed between the fixed jaw and the moving jaw. The material is crushed between a mantle and a concave bowl, both of which are rotating and stationary respectively. Compression crushing is well suited for hard and abrasive materials because the compressive strength of the material is what causes fractures.
● Impact Crushing: The process called impact crushing involves the repeated striking of the material with a very fast rotating element, for instance, a rotor with the attached hammers or blow bars. Impact crushers and hammer mills work with it. In impact crushers, the material is hit by rotating hammers or blow bars, as a result it breaks up into smaller pieces. This method is preferable in the case of less abrasive materials, such as limestone, dolomite, and soft to medium hard rocks. The high-speed impact forces can wear down the crushing elements rapidly when processing very abrasive materials.
● Attrition Crushing: Abrasion crushing is the consequence of material being subjected to the grinding action, often between two rotating surfaces or media. This is the reason why there is a decrease in particle size due to abrasion and friction. This method is popularly employed in fine grinding processes such as ball mills or rod mills. In these mills, the material is blended with grinding media, for instance, balls or rods made of steel. The rotation of the mill makes the media grind and wear out the material, thus lowering its size in stages. Atrition crushing is great for the production of very fine particle sizes and it is commonly used in mineral processing and mining for grinding ore.
● Shear Crushing: Shear crushing takes a shearing force and applies it to the material, which results in the formation of cracks on the weak planes. This method is not frequently used in rock crushing applications but can be found in some specialized equipment, like roll crushers, for example, for softer materials like coal or clay. In roll crushers, the material is pulled between two counter-rotating rolls which exert a shear force on it. The material breaks and reduces in size due to this force. This kind of crushing works better for materials that have a layered or flat structure because the shear forces can easily split the material along the weak planes.
● Impact Crushing: The process called impact crushing involves the repeated striking of the material with a very fast rotating element, for instance, a rotor with the attached hammers or blow bars. Impact crushers and hammer mills work with it. In impact crushers, the material is hit by rotating hammers or blow bars, as a result it breaks up into smaller pieces. This method is preferable in the case of less abrasive materials, such as limestone, dolomite, and soft to medium hard rocks. The high-speed impact forces can wear down the crushing elements rapidly when processing very abrasive materials.
● Attrition Crushing: Abrasion crushing is the consequence of material being subjected to the grinding action, often between two rotating surfaces or media. This is the reason why there is a decrease in particle size due to abrasion and friction. This method is popularly employed in fine grinding processes such as ball mills or rod mills. In these mills, the material is blended with grinding media, for instance, balls or rods made of steel. The rotation of the mill makes the media grind and wear out the material, thus lowering its size in stages. Atrition crushing is great for the production of very fine particle sizes and it is commonly used in mineral processing and mining for grinding ore.
● Shear Crushing: Shear crushing takes a shearing force and applies it to the material, which results in the formation of cracks on the weak planes. This method is not frequently used in rock crushing applications but can be found in some specialized equipment, like roll crushers, for example, for softer materials like coal or clay. In roll crushers, the material is pulled between two counter-rotating rolls which exert a shear force on it. The material breaks and reduces in size due to this force. This kind of crushing works better for materials that have a layered or flat structure because the shear forces can easily split the material along the weak planes.
What are the Different Types of Crushers?
| Type of Rock Crusher | Description | Application | Feed Size | Output Size | Capacity | Advantages | Limitations |
|---|---|---|---|---|---|---|---|
| Jaw Crusher | Uses a reciprocating jaw to compress and crush material against a stationary plate | Primary crushing stage, handles large, abrasive materials | Up to 1,500 mm | 50-300 mm | Moderate to high | Simple design, reliable, handles abrasive materials | Limited reduction ratio, lower capacity compared to gyratory crushers |
| Cone Crusher | Uses a rotating mantle within a concave bowl to compress and crush material | Secondary and tertiary crushing stages, offers better shape and size control | 50-300 mm | 6-100 mm | Moderate to high | Better shape and size control, higher reduction ratio | Higher capital and operating costs, more complex design |
| Impact Crusher | Uses high-speed rotors with attached hammers or blow bars to strike and break material | Suitable for less abrasive materials, produces a more cubical product shape | 50-500 mm | 5-100 mm | Moderate to high | Produces cubical shape, handles softer materials well | Higher wear on crushing elements, not suitable for highly abrasive materials |
| Gyratory Crusher | Uses a rotating mantle within a concave surface to compress and crush material | Large-scale primary crushing applications, high capacity | Up to 1,500 mm | 100-300 mm | High | High capacity, continuous operation, higher reduction ratio | Higher capital and operating costs, more complex design and maintenance |
| Hammer Mill | Consists of a series of hammers mounted on a rotating shaft that strike and break material against a screen or plate | Suitable for softer materials, produces finer particle sizes | 50-500 mm | 0.1-20 mm | Low to moderate | Produces finer particle sizes, handles softer materials well | Higher wear on hammers, not suitable for highly abrasive materials |
| Roll Crusher | Uses two or more rotating cylinders to compress and break material | Typically used for softer materials, such as coal or clay, produces a finer product | 50-500 mm | 2-50 mm | Low to moderate | Lower energy consumption, handles softer materials well | Limited reduction ratio, not suitable for highly abrasive materials |
Primary Crushers
The primary crushing stage is the first stage of the crushing process. This is where the bulk of the rocks or ore are crushed to make them manageable in the next crushing stages. The primary aim of the primary crushing is to produce a product that can be moved easily by conveyors or feeders to the next step of the crushing. Primary crushers are built to process large and abrasive feed materials. They can handle feed sizes of up to 1500 mm, but it depends on the type and size of the crusher.
Jaw crushers and gyratory crushers are the two most common kinds of primary crushers. These crushers apply compressive forces to the material, but they can be different in their design and the way they operate.
Jaw crushers and gyratory crushers are the two most common kinds of primary crushers. These crushers apply compressive forces to the material, but they can be different in their design and the way they operate.
Jaw Crushers
Jaw crushers are the most common primary crushers used in the mining and construction industry. They are represented by a fixed jaw and a moving jaw that form a V-shaped crushing chamber. The moving jaw moves back and forth and presses the material against the fixed jaw, that in turn causes it to break down into smaller pieces. Jaw crushers are known for their simplicity, reliability, and the ability to manage large and abrasive materials. They take in feed sizes as large as 1,500 mm and the finished product size ranges from 50 mm to 300 mm depending on the settings of the crusher and the material properties.
There are two main types of jaw crushers: simple-toggle and double-toggle. A single-toggle jaw crusher is simpler in design and is widely used because of its low cost and ease of maintenance. On the one hand, the double-toggle jaw crushers have a more complicated mechanism that creates a more uniform product size and a more efficient crushing. On the other hand, they are often more expensive and require higher maintenance than single-toggle ones.
Gyratory Crushers
Gyratory crushers are also another primary crusher type which is usually used in large scale mining operations. They are equipped with a vertical conical crushing chamber with a rotating mantle that moves inside a stationary concave surface. The mantle is rotating and the material is getting compressed against the concave surface thereby it breaks and becomes smaller. Gyratory crushers are valued for their high capacity, continuous operation, and ability to process feeds up to 1500 mm in diameter.
Unlike jaw crushers, gyratory crushers generally have higher reduction ratios. Consequently, they can produce smaller output sizes in a single pass. Moreover, they have a higher production capacity and can do more material per hour. Nevertheless, gyratory crushers are usually more expensive, need more intricate foundation and have higher operating and maintenance costs as compared to jaw crushers. The decision of a jaw crusher or a gyratory crusher is based on, for instance, the required output size, production capacity, and the available budget.
Unlike jaw crushers, gyratory crushers generally have higher reduction ratios. Consequently, they can produce smaller output sizes in a single pass. Moreover, they have a higher production capacity and can do more material per hour. Nevertheless, gyratory crushers are usually more expensive, need more intricate foundation and have higher operating and maintenance costs as compared to jaw crushers. The decision of a jaw crusher or a gyratory crusher is based on, for instance, the required output size, production capacity, and the available budget.
Secondary Crushers
The secondary crushing step follows the primary crushing step. The purpose of this machine is to decrease the size of the material coming from the primary crusher. The objective of the secondary crushing is to get a product of a more homogenous size and shape. This is the reason why it is especially suitable for further processing or use in different fields. Secondary crushers crush materials in the size range of 50 mm to 300 mm, which is determined by the type and size of the crusher. They produce output sizes from 6mm to 100mm.
Secondary crushers can be divided into three main types: cone crushers, roller crushers, and impact crushers. All types of crushers have their own distinctive design, working principles, and applications.
Secondary crushers can be divided into three main types: cone crushers, roller crushers, and impact crushers. All types of crushers have their own distinctive design, working principles, and applications.
Cone Crushers
Cone crushers are usually applied in the secondary and tertiary crushing. They also play a role in reducing the size of the material coming from the primary crusher. They include a rotating mantle which moves within a stationary concave bowl. It does this by squeezing and squeezing the material as it goes through the device. Cone crushers are often used because they are capable of producing a product with a more uniform and cubical shape as opposed to jaw crushers. This is what makes them suitable for the industry where particle shape is of utmost importance, such as in the production of concrete aggregates.
There are various cone crushers, such as standard cone crushers, short head cone crushers and fine cone crushers. A standard cone crusher has a taller crushing chamber and is used for providing larger output sizes, usually ranging between 25 mm and 100 mm. A short-head cone crusher has a short crushing chamber and it is designed for the production of finer output sizes, generally between 6 mm and 25 mm. A fine cone crusher, also known as a tertiary cone crusher, is used for the production of They are manufactured to produce very fine output sizes, mostly below 6 mm.
To understand cone crushers in detail, check out What is a Cone Crusher & How Does a Cone Crusher Work?
Roller Crushers
Roll crushers are another type of secondary stage crushers. They use two or more rotating cylinders for compressing and breaking down the material. The cylinders can be smooth or toothed, based on the different application and type of material. Roller crushers are usually applied for soft materials, for example, coal, clay or soft rocks. They can give a finer end product as compared to other types of crushers. They are also recognized for their low energy usage and fairly low wear on the crushing surfaces.
There are two main types of roller crushers: single-roll crushers and double-roll crushers. Single-roll crushers are equipped with a rotating cylinder which squeezes the material against a fixed plate or screen. The double-roll crushers, in contrast, are equipped with two rotating cylinders that compress the material between them. The double-roll crushers can be further divided into the smooth-roll crushers that have the smooth cylinder surfaces and toothed-roll crushers that have toothed or corrugated surfaces to provide the better grip and crushing action.
There are two main types of roller crushers: single-roll crushers and double-roll crushers. Single-roll crushers are equipped with a rotating cylinder which squeezes the material against a fixed plate or screen. The double-roll crushers, in contrast, are equipped with two rotating cylinders that compress the material between them. The double-roll crushers can be further divided into the smooth-roll crushers that have the smooth cylinder surfaces and toothed-roll crushers that have toothed or corrugated surfaces to provide the better grip and crushing action.
Impact Crushers
Impact crushers are the secondary crushers or the tertiary crushers that use high speed impact forces to break the materials. They are a set of rotors with hammers or blow bars mounted on them that crush the material as it enters the crushing chamber. This phenomenon results in the material to be cracked and fragmented into smaller pieces. The impact crushers are applicable for less abrasive materials such as limestone, dolomite, and soft to medium – hard rocks. They can generate a more cubical and uniform product shape which compression crushers do not have.
There are two main types of impact crushers: horizontal shaft impactors (HSI) and vertical shaft impactors (VSI). HSI crushers utilize a horizontal rotor that throws the material on stationary anvils or curtains, which results in the material breaking upon impact. VSI crushers, unlike the traditional crushers, have a vertical rotor which accelerates the material and throws it against a stationary anvil ring or a cloud of material itself. Hence, the shape of the product is more cubical and uniform. VSI crushers are commonly used in the last stage of the crushing process in order to enhance the particle shape and eliminate deformed or elongated particles.
There are two main types of impact crushers: horizontal shaft impactors (HSI) and vertical shaft impactors (VSI). HSI crushers utilize a horizontal rotor that throws the material on stationary anvils or curtains, which results in the material breaking upon impact. VSI crushers, unlike the traditional crushers, have a vertical rotor which accelerates the material and throws it against a stationary anvil ring or a cloud of material itself. Hence, the shape of the product is more cubical and uniform. VSI crushers are commonly used in the last stage of the crushing process in order to enhance the particle shape and eliminate deformed or elongated particles.
Tertiary and Quaternary Crushers
Tertiary and quaternary crushers are employed in the last stages of the crushing process. They produce very fine products, often below 6 mm. These crushers are normally used in applications where the size reduction and shape of the particles are of high concern. There are some examples, like the production of manufactured sand, industrial minerals, or fine aggregates for specific concrete mixes.
There are several common types of tertiary and quaternary crushers:
● Fine Cone Crushers: These are cone crushers with a very short crushing chamber and a specific design. They are manufactured to produce fine output sizes in the range of 0.078 inch to 0.236 inch.
● Vertical Shaft Impactors (VSI): VSI crushers are employed in tertiary and quaternary stages. They contribute to particle shape and yield uniform, cubical products.
● High-Pressure Grinding Rolls (HPGR): In the HPGR crushers two counter-rotating rollers with a small gap between them are used. They squeeze and crush the stuff. They are very good at fine grinding and are often used in the mining industry for the grinding of ore.
● Autogenous and Semi-Autogenous Mills (AG/SAG): AG and SAG mills are large, rotary drums that use the material itself as the grinding medium. They can be used in the final stages of the crushing operation to produce fine uniform particles.
The selection of tertiary and quaternary crushers depends on various parameters. These are the specialized application, material properties, and the output size and shape which are required. In other cases, a mixture of different crushers types may be used to produce the best results.
Factors to Consider When Choosing the Right Crusher for Your Application
The right choice of crusher type is a critical element in your application to achieve high efficiency and low cost of operation.
Material Properties:
1. Hardness: The hardness of a material determines the crushing force needed and the type of crusher that is suitable. Crushing of the harder materials may require the use of the compression crushers, while the softer materials can be processed by the impact or roller crushers.
2. Abrasiveness: Hardly abrasive elements might lead to excessive wear on crushing surfaces, which will impact the choice of crusher and the use of wear-resistant parts.
3. Moisture Content: The moisture content of the material can influence the crushing process and determine the type of crusher. Some crushers, such as jaw crushers, can handle higher moisture content as well as impact crushers.
4. Stickiness: Sticky material can have a negative impact on the crusher by causing blockages and build-up, which will directly influence the selection of the crusher and the need for special features or accessories.
Feed Size and Output Size:
1. Maximum Feed Size: The size of the largest particles in the feed materials determines the necessary inlet opening and the appropriate crusher type. Primarily, the primary crushers are made to crush bigger feed sizes compared to the secondary and tertiary crushers.
2. Desired Output Size: The crushing equipment and the number of crushing stages are determined by the output size range. Some crushers, for instance, cone crushers, can produce finer product sizes than others, such as jaw crushers.
3. Size Reduction Ratio: The relationship between the feed size and the desired output size determines the type of crusher and the number of crushing stages needed to fulfill the required size.
Production Capacity:
1. Throughput: The necessary production capacity, measured in tons per hour, defines the size and type of crusher. If the output is higher, then the crusher may need to be bigger or there may be a need for a couple of crushing units.
2. Crushing Circuit Configuration: The design of the overall crushing circuit layout, the number of crushing stages, the arrangement of crushers, screens and conveyors, influences the choice of crushers and the production capacity.
Product Shape and Gradation:
1. Particle Shape: The type of shape that the particles should manifest, e.g. cubical or angular, is one of the factors that are taken into account when the crusher is selected. Cubical particles are the primary products of cone and compression crushers, while impact crushers usually generate the angular particles.
2. Gradation Requirements: The type of crusher required for the final product and the possibility of other screening or classification equipment are largely dependent on the particle size distribution that is required.
Operational Considerations:
1. Maintenance and Wear Parts: The issues of maintenance, wear parts availability, and the wear life of the main components are the main things that should be considered in the choice of a crusher.
2. Energy Consumption: The calculation of the energy efficiency of the crusher and its associated operational costs such as electricity and fuel consumption shall be carried out.
3. Noise and Dust Emissions: The level of noise and dust produced by the crusher is something that should be considered, and this is really important in ecologically sensitive locations or urban settings.
Capital and Operating Costs:
1. Initial Investment: The capital cost of crusher is the most important factor to consider before the project budget is prepared. It includes the purchase cost, installation cost, and commissioning expenses.
2. Operating Costs: The recurrent costs such as electricity consumption, replacing parts and maintenance are important during the crusher’s life cycle.
Footprint and Layout:
1. Available Space: A feasibility study should be conducted to check the crusher’s dimensions, working area requirements and compare them to the available space at the installation site.
2. Integration with Existing Equipment: The crusher’s integration with the feeders, screens, and the conveyors, within the plant layout considered, is also another factor which need to be considered to ensure a smooth operation.
Once you understand these factors, visit the 10 Best Crusher Manufacturers for Your Mining Project to find the best manufacturer.
Conclusion
It is essential that you understand these crushers and their respective uses as this knowledge will help you to identify the appropriate equipment for your crushing needs. Becoming aware of the factors as the physical characteristics of the material, feed size, output size, production capacity, product shape and gradation, capital and operating costs, and plant layout will help you in the choice of a crusher which is suitable for your specific purpose.
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