As the construction and mining industries change quickly, the need for accuracy in sand and gravel is growing. The raw ore crushing process is complex.
It includes several stages of crushing, sand production, and shaping. It's important to choose the right type of crusher at different stages. This helps reduce the raw ore to the needed particle size. This article aims to collectively discuss the three general stages of stone crushing.
Initially, a brief introduction to the stone crusher is necessary. The stone crusher is a strong machine. Common types include the jaw crusher, cone crusher, and impact crusher. There are also sand-making machines, like the impact sand-making machine and the vertical shaft impact sand-making machine. During mineral crushing, the requirements for each crushing stage vary, so how does one select the appropriate crusher?
Primary Crushing: Coarse Crushing
Primary crushing, also known as the first or rough crushing phase, usually involves stones that are about 100 to 300 mm in size. Jaw crushers are often used in this stage because they can handle high compression forces and large feed sizes. They efficiently manage substantial material chunks, rendering them apt for additional processing in the following stages.
How does a jaw crusher work?
In the primary crushing process, operators feed large raw materials into the jaw crusher's crushing chamber. There, the fixed jaws and movable jaws crush the materials. This happens through repeated squeezing until the materials reach the required size.
Secondary Crushing: Refining the Size
After secondary crushing, the stone size is usually about 20 to 100 mm. They then feed the stone into the secondary crusher for more size reduction. Operators usually choose cone crushers and impact crushers for this stage.
Applicable Machines-Cone Crusher
A cone crusher is a machine that crushes rocks. Companies use it in mining and aggregate industries. This machine can handle medium-hard to hard materials. It crushes these materials to the desired size.
Working Process and Chamber types
In secondary crushing, the material enters the cone crusher's crushing chamber. Inside, there is a moving cone and a fixed cone. The moving cone squeezes and collides with the fixed cone and the material. This process shapes the products and achieves the goal of crushing.
A cone crusher has different types of chambers: standard, medium, and short head. The standard chamber is good for medium crushing. It works well with materials that have slightly smaller particle sizes. Its crushing ratio is usually between 4 and 6 mm.
The medium and short head types are best for fine crushing. They have a long parallel section in the crushing chamber. This design enables the crushing and grinding of the material more completely. The crushing ratio for these types can reach 5 to 8 mm or even higher.
Applicable Machines-Impact Crusher
In the secondary crushing process, you can use an impact crusher. People recognize it for its high crushing ratio, cubic yield, and efficient energy use.
Working Principle and Models
The impact crusher has a plate hammer that spins fast. It hits and crushes the material. Then, it sends the material to the impact plate for more crushing. This process continues until the material is smaller than the gap between the impact plate and the plate hammer. At that point, it will be expelled.
The impact crusher comes in two main types: the PF impact crusher and the large mouth impact crusher. The large mouth type has a big feed opening that can handle sizes up to 1000mm. By changing the position of the impact frame, it can perform both medium and fine crushing. This means one machine can do two jobs. The PF impact crusher has a smaller feed opening. It is best for fine crushing of small to medium materials. This type is often used in stone processing lines that need precise product sizes.
Differences of Impact Crusher and Cone Crusher
The result of secondary crushing is a finer and more uniform aggregate. The impact crusher and cone crusher are both used in this process, but they have important differences.
The impact crusher has a simple design that is easy to maintain. It looks like a square block with a hammer shape. This machine mainly crushes coarse and medium-hard materials. These materials should be less than 500 mm in size and have a strength of no more than 350 MPa.
It can crush most ores that have low iron content. The sand and gravel produced are uniform and cubic. They contain few needle-like or flake-like pieces. The crusher offers high production capacity and low initial costs. However, it has high maintenance and replacement costs later.
The cone crusher has a more complex design and is harder to maintain than the impact crusher. It looks like an upside-down water bottle. This machine is mainly used for crushing medium to hard ores and rocks. It can handle materials with a feed size of 65-300mm, such as calcite, limestone, and granite, as well as construction waste. Its crushing efficiency is good, but it is not as effective as the impact crusher for shaping the crushed particles. The production capacity ranges from 12 to 1000 tons per hour. The initial purchase cost is high, but the parts last a long time. This results in lower maintenance costs later on.
Conclusion
Therefore, how to choose the machine in secondary crushing? In summary, if customers use hard raw materials and can pay more, they should choose a cone crusher. If customers need shaping, they should select an impact crusher.
Tertiary Crushing: Achieving Precision
Tertiary crushing is the last step in the crushing process. In this stage, the material is sized between 0.1 and 20 mm. Stone products in this range can have many uses. These include construction sand and refined chemical materials. This phase often requires special machines, such as the VSI (Vertical Shaft Impact Sand-making Machine) crusher.
Introduction of the VSI sand making machine
The VSI (Vertical Shaft Impact) sand-making machine is made for crushing and shaping materials. It is often used in the last stage of sand production. The final product has well-shaped particles and a steady output. This makes it an efficient crusher for factory construction. This machine is commonly used in mining, metallurgy, and building materials.
How does a VSI sand making machine work?
The VSI apparatus is crucial during the tertiary crushing stage. It fine-tunes materials that have undergone two rounds of crushing. The VSI employs a technique known as stone hitting stone. It propels stones towards an anvil or against each other within a high-speed rotor. This collision fractures the stones into smaller fragments.
The pieces are then screened and sorted for the right sand size and quality. The process runs continuously. The crusher receives rocks while it discharges crushed sand. This ensures that only the right-sized material leaves the machine.
In conclusion, crushing stones in three stages is common in mining and aggregate work. You need to choose the primary, secondary, and tertiary crushers carefully. This choice makes sure the stone particles are the right size and shape. They must meet the users' needs.
Every stage in the procedure is crucial. The initial step, primary crushing, downsizes large stones for simpler manipulation. Subsequently, secondary crushing diminishes the output from primary crushing to an even tinier size. Lastly, tertiary crushing fine-tunes the stone fragments to the precise size desired by the customer. Now that you're aware of these three phases, you can select a crusher that aligns with your requirements.
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