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Wet, Dry and Semi-Dry Sand Making Analysis of Sand Making Processes

Thomas Huang posted this article in July 07, 2020

Wet, dry and semi-dry sand making methods are currently widely used artificial sandstone production processes. Xiaobian has simply compared the advantages and disadvantages of the first two processes. Today we will talk about their respective advantages around these three processes. Features and selection basis.
Production process of wet artificial sand
The production process of wet artificial sand and gravel materials is generally adopted in areas with abundant water resources.
advantage:
1) The surface of the produced aggregate and sand is clean, with good perception and good quality;
2) A large amount of water is used for washing, and the production environment is free of dust pollution.
Disadvantages:
1) A large amount of precious water resources need to be consumed in the production process. Generally, it takes 2-3.5m³ of water to produce 1t of gravel;
2) The produced artificial sand has a high moisture content, and the particles with a particle size of less than 0.16mm are relatively small (generally 10%), the fineness modulus is relatively coarse, and the sand output is low;
3) A large amount of mud powder sewage is discharged during the production process, which pollutes the environment, the recycling cost is high, and the effect is poor;
4) Many types of equipment, high investment, large area, high operating costs, difficult operation and management, and high production cost of artificial sand;
5) It requires sufficient water resources and cannot be produced normally in arid areas with little rain or in cold icy seasons. Dry artificial sand production process
In areas where the weather is cold, drought, little rain, and there is a serious lack of water resources, dry artificial sand and gravel production techniques are mostly used.
Similarities and differences between dry and wet methods
The production process of dry artificial sand and gravel is almost the same as that of wet process, except that after checking and screening, the spiral separator or bucket wheel sand washing machine is replaced with a powder separator, and the aggregate is not washed. Use a dust collector to replace the fine sand recovery device and wastewater recycling device. Depending on the water source, a very small amount of water is used for spraying to remove dust, and almost no water is used. The use of high-efficiency dust collectors for multi-point dust removal not only has good dust removal effect and low cost, but also the recovered stone powder can be made into bricks and used as road cushions for comprehensive and efficient use.
advantage:
1) The aggregate produced has a low moisture content of artificial sand (generally less than 2%). It does not need to be equipped with a dehydration device like the wet production process. The finished sand can only be used after 48 hours of natural stacking, which can reduce the storage capacity of the finished sand. It will not freeze in the cold season and can be produced continuously throughout the year;
2) The content of stone powder in the finished artificial sand can be steplessly adjusted by a special powder separator, the sand production rate is high, the fineness modulus meets the standard of medium sand, and the content of stone powder can meet the requirements of hydropower engineering standards and urban construction standards. The strength of the concrete made Higher. Fine powder can be recovered by dust removal and powder separator, and can be used as subgrade cushion or as slag brick raw material;
3) Little or no water is used in the production process, which reduces the settings for water extraction and sewage treatment in the wet production process. The production site is small, the investment is small, the operation management personnel are few, the centralized operation control is easy, the automatic management is realized, and the operation cost is low. The low moisture content in the raw materials is conducive to sieving and high sand formation rate (generally around 50%);
4) Because it does not use or use a small amount of water resources, it is not affected by the dry and cold seasons, and can be continuously produced throughout the year;
5) Save a lot of precious water resources;
6) According to actual experience, as long as the content of the source soil and organic matter is controlled in a specific area, even if no powder selection equipment is used, the artificial sand produced can meet the requirements of hydraulic and urban construction standards.
Production process of semi-dry artificial sand
The semi-dry artificial sand production process is a new process that has only been applied in recent years.
This method is widely used in the production of artificial sand and gravel in hydropower projects using limestone as raw material in Guizhou, Hunan and other regions. It is between the dry and wet production processes, and its process flow is roughly the same as the wet production process. The coarse crushing and medium crushing adopts the impact crusher, and a large amount of washing water is added to the pre-screening to rinse the aggregate. Generally, the aggregates with a certain moisture content less than 5-40mm will enter the vertical sand making machine, and no water will be added to the screening site. The aggregate also needs to enter the stone washing machine for washing, some or all of the artificial sand does not go through the sand washing machine for washing.
Features:
Compared with the wet production process, the most important feature of the semi-dry production process is that the mud and stone powder on the surface of the sand-making raw material are washed away with water. Some or all of the finished sand is no longer washed, so the water consumption is relatively less, and the loss of stone powder in the finished sand Less, the moisture content is lower. However, this sand and gravel production process requires more water resources, and the sewage treatment device still needs to be equipped, but the specifications are much smaller. The investment cost is less than the wet method and more than the dry method, the content of the finished sand and stone powder is between the two, and the operating cost is also between the two.
The biggest shortcoming of the semi-dry production process is that it is washed at the pre-screening place and enters the sand making raw material of the vertical sand making machine. The moisture content is 6-10%, the sand making rate of the sand making machine is low, and the screening is difficult. . After testing in multiple experimental sites, the true sand formation rate is 20-35% (the value of the artificial sand content in the sand machine's discharge minus the sand content in the feed), and the sand production cost is higher than the dry method.
Selection basis
The basis of selecting dry, wet and semi-dry artificial sand production process:
1) First of all, it depends on the area where the artificial sand and gravel system is located, the water resources, the cleanliness of the raw materials, and the specific requirements on the content and fineness modulus of the aggregate and artificial sand and gravel powder.
A country with severe water scarcity is also a country with severe water pollution. If the original conditions allow, the dry production process is preferred, followed by the semi-dry production process, and finally the wet production process.
2) In consideration of equipment investment, floor space size, ease of production management, and processing cost of artificial sand and gravel materials, dry method is also the first priority, followed by semi-dry method, and finally wet method.
Regardless of the dry, wet or semi-dry artificial sand production technology, most of the soil and weathered gravel in the raw materials should be removed. Generally, the particle size of the soil and weathered crushed stone is relatively small. Before entering the coarse crushing equipment, the vibrating feed sieve is equipped with a screen. Most of the soil and weathered crushed stone are discarded through the screen hole. The system can reduce the cleaning cost of aggregate and artificial sand.

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