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With the popularity of artificial sand, more and more customers are consulting artificial sand and sand making equipment. Here are 30 common questions about artificial sand and sand making process.
The main advantages of dry sand production line are:
1) The produced sand has a low moisture content, generally less than 2%, and can be directly used in commercial concrete and dry-mix mortar;
2) The content of stone powder in the finished sand is adjustable and controllable, centralized recycling can be used comprehensively, and dust emission can be reduced;
3) Little or no water is used in the production process to save water resources and protect the environment;
4) Easy to centralize operation control and realize automatic management;
5) It is not affected by drought and cold seasons, and can be produced continuously throughout the year.
The main reasons are:
1) Consume a lot of water, it needs 2~3.5m³ of water to produce 1t artificial sand;
2) The produced sand has high water content, which must be dehydrated, and need to be re-dried when used in dry-mixed mortar;
3) The fineness modulus of product sand is relatively coarse, and the sand output is low;
4) Produce a lot of mud powder sewage, pollute the environment, and the stone powder is not easy to recycle;
5) There are many types of infrastructure investment and equipment, and the production cost is high;
6) It cannot produce normally in arid and drier areas or in freezing seasons.
Compared with wet sand making process, the most important feature of semi-dry sand making process is that mud and stone powder on the surface of the sand-making raw materials is washed off with water. Part or all of the finished sand is no longer washed with water, so the water consumption is relatively small, and the loss of stone powder in the finished sand is less, making the moisture content is low.
The methylene blue (MB) value is used to determine whether the content of particles with a particle size of less than 0.075mm in the artificial sand is mainly mud or stone powder with the same chemical composition as the processed parent rock. The methylene blue value of machine-made sand requires MB≤1.4, and it should be controlled below 1.0.
In the artificial sand dry production process, the humidify and mix of the finished sand can make the moisture content reach the saturated surface dry state, which is beneficial to the control the water consumption of subsequent concrete mixing, and can reduce segregation and dust during transportation.
In the production process, the lithology, moisture content and gradation of the feed material are easy to change, and the screening process will also cause problems such as blockage and damage and the efficiency and parameters of the crushing and dust removal equipment are also unstable, which may easily lead to the unstable of the fineness modulus of the artificial sand.
Waste concrete, masonry and industrial waste are sorted, washed, crushed, and screened through special equipment to produce artificial sand. However, they are mainly used to produce recycled coarse aggregate currently.
1) First of all, it depends on the area where the production line is located, the water resources, the cleanliness of the raw materials, and the specific requirements for aggregate, machine-made sand and gravel powder content, and fineness modulus. If the original conditions permit, dry production process is preferred, and then semi-dry production process, wet production process is the last.
2) Considering the equipment investment, the size of the floor area, the difficulty of production management, and the cost of artificial sand and gravel processing, dry production process is also preferred, and then semi-dry production process, wet production process is the last.
The general method for testing and sampling of artificial sand is:
1) When sampling on the pile, the sampling sites should be evenly distributed. Before sampling, remove the surface of the sampling site, and then extract 8 pieces of roughly equal amount of sand from different parts to form a group of samples.
2) When sampling from the belt conveyor, a catcher is used to regularly sample 4 equal parts of sand at the outlet of the end side of the belt conveyor to form a set of samples.
3) When sampling from trains, cars, and cargo ships, 8 parts of roughly equal amounts of sand are taken from different parts and depths to form a set of samples.
There are two methods to test the powder content in artificial sand: washing method and dry sieving method. The representative is ASTMC136 or AASHTOT27, which is suitable for dry sieve and ASTMC117 or AASHTOT11, which is suitable for water sieve.
The current methods for removing excess stone powder in undisturbed sand mainly include water washing hydraulic classification, high-frequency sieve mechanical sieving method, and powder-selecting dust-removing wind classification method.
The gradation of artificial sand particles can be achieved by adjusting the feed gradation, feed volume, crusher speed, screen size and other aspects.
The factors that affect the artificial sand grain shape are:
1) The lithology of the source rock, such as the development of joints is not conducive to obtaining a better grain shape;
2) Type of crushing equipment, impact crusher has better final products shape;
3) Screen type, such as square holes, has better control of the grain shape.
Because the energy utilization rate of crushing is higher than that of grinding, more crushing and less grinding are beneficial to save energy, but it cannot be completely replaced by crushing.
The “rock on rock” crushing method is suitable for crushing abrasive materials with medium hardness and above, such as basalt etc. The shape of the finished products is good under the crushing method of "rock on rock".
The “rock on iron” crushing method is suitable for crushing abrasive materials with medium hardness and below, such as limestone etc. Under the “rock on iron” crushing method, sand making machine has high efficiency.
Besides, “rock on rock” crushing method is used for shaping and “rock on iron” crushing method is used for sand making.
The dual motors in sand making machine has two main functions:
1) The dual motors ensure the balanced force of the spindle.
2) Ensure the speed. Energy will be lost during the transmission process; the dual motors ensure high power and ensure the speed.
In dual-drive equipment, the phenomenon that the current of one motor is lower than the other is called inert response, and the deviation requirement should not be greater than 10%; and we can solve this problem by adjusting and equalizing the tension of the transmission belt, checking the cleanliness of the terminal and checking the soft start.
If the impeller rotor does not perform proper static balance correction, the rotor has large imbalance, and the centrifugal force generated during operation will cause abnormal vibration and failure of the equipment, abnormal wear of the rotor, and excessive noise. According to industry standards, the impeller rotor balance level of the vertical shaft impact crusher is G16.
After replacing the wear parts of the impeller rotor of the vertical shaft impact crusher, the basic steps to correct the static balance are:
1) Clean the sand and gravel, old worn parts, debris, etc. on the rotor and accessories, and confirm that they can continue to be used;
2) Reinstall the wear parts and install the rotor on the balance tooling;
3) Confirm the unbalanced weight and position;
4) Recheck the balance of the rotor.
1) The properties of raw materials. If the raw material has low hardness and strength, good crushability, the efficiency of sand making is high;
2) The moisture content of raw material. If the moisture content of raw material is high, it will reduce the sand production capacity;
3) The feeding volume. Generally speaking, the larger the feeding volume, the better the crushing effect. But, there is an extreme point;
4) The speed of the impeller. The higher the speed, the better the crushing efficiency.
It is because the rotor does not form a uniform lining at the beginning of the operation and leads to the vibration. It is generally necessary to feed in a few squares of fine material at the beginning. If the coarse material is fed in to the machine at the beginning, it will continue to vibrate for several hours until a uniform material lining is formed in the rotor.
The screening equipment mainly used for sand and gravel production is: bar screen, cylindrical screen, circular vibrating screen, linear vibrating screen, high frequency screens and probability screen. Among them, bar screens are mainly used for soil removal process. Circular vibrating screen and linear vibrating screen are more commonly used.
1) The sand and gravel contains a large number of particles with critical separation points;
2) The sand and gravel contains more flake materials and cannot be screened smoothly;
3) The sand and gravel has high mud content;
4) The sand and gravel has high moisture content.
1) The quality or material of the screen mesh is unqualified;
2) The tension of the screen mesh is not enough, which causes the screen to vibrate, and the broken or damage is generally along the edge of the screen mesh or at the edge layer;
3) The vibration amplitude of the vibrating screen is too small, making the sand particles accumulated on the screen mesh and quickly damages the screen mesh.
At present, the general requirement for the fineness modulus of artificial sand is 2.6-3.0, and it is generally recommended to use a screen size of 3.0mm or 3.5mm.
Standard wear-resistant parts include: cylindrical roller bearings, deep groove ball bearings, thrust ball bearings, expansion sleeves, conveyor belts, oil seals, and O-rings.
Non-standard wear-resistant parts include: upper bushing, lower bushing (lifting part of the feeding hopper), shock-absorbing rubber, flap guard ring, upper/lower runner plate, impact block, split cone, wear plate, throwing material head, blanking lining ring, feed pipe, upper/lower striking guard plate, hopper lining ring, distribution tray, bulk tray (bulk cone), peripheral guard plate.
Wheel sand washing machine has simple structure, and its failure rate is much lower than that of spiral sand washing machine. And in the washing process, the loss of fine sand and stone powder is less, the gradation of final produced sand is well and the fineness modulus is easy to control and the quality of finished sand is stable.
The apparent density of artificial sand is not less than 2500kg/m³; the loose bulk density is not less than 1400kg/m³; the porosity is not more than 44%.
Natural rocks are divided into three types:
The first type is magmatic rock (igneous rock), which is formed by magma eruption, and is generally hard and uniform;
The second type is sedimentary rock (sedimentary rock), which is weathered, transported, deposited and formed by a series of geological processes such as diagenesis. Generally, it has layered distribution structure with similar properties in the same period;
The third type is metamorphic rocks, which are formed after metamorphic mixing on the basis of existing rocks. It has both the above-mentioned rocks’ features and its own features.
The characteristics have both the above-mentioned rock and its own characteristics.
Granite, basalt, pebble, andesite, rhyolite, diabase, diorite, sandstone, limestone and other varieties are usually used for artificial sand production. According to the different types of the rocks, the strengths and applications of the artificial sand are also different.
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