A complete sand and gravel aggregate production line is compose of crushing system, screening system, sand production system (there is no this system if customers do not need artificial sand), storage and delivery system, dust removal system.
Many customers wonder how to configure and design complete sand and gravel aggregate production line. Here are the key points.
1.1 design points of discharge hopper
There are two main forms of the discharge hopper: The vibrating feeder is arranged at the bottom of the discharge hopper or the vibrating feeder is arranged outside the bottom of the discharge hopper.
The vibrating feeder is arranged at the bottom of the discharge hopper: The advantage of this form is that it has strong adaptability to materials under different conditions, and the discharging of crushed raw materials is relatively smooth.
The disadvantage is that raw materials in the hopper are directly pressed on the equipment, which requires high quality equipment and the manufacturing cost of the equipment is high.
The vibrating feeder is arranged outside the bottom of the discharge hopper: The advantage of this form is that raw materials in the hopper are not directly pressed on the equipment, the requirements for the equipment are lower, and the manufacturing cost of the equipment is correspondingly lower.
The disadvantage is that when the raw materials contain more soil or have poor fluidity, it is easy to block or discharge the material.
1.2 Selection principle of crusher
The crushing system is mainly composed of coarse crushing, medium crushing and fine crushing (shaping). The selection of equipment at each stage is mainly determined by the crushing work index, abrasion index, maximum feeding size and product quality requirements of the ore.
Wi: Crushing work index- the difficulty degree of material crushing;
Ai: Abrasion index-the wear degree of material to the machine parts.
The typical processes of the crushing system are: single-stage hammer crusher system; jaw crusher + impact crusher system; jaw crusher + cone crusher system; jaw crusher + impact crusher + vertical shaft impact crusher system and jaw crusher + cone crusher + cone crusher system.
The selection of the crushing system should be based on the material characteristics, product shape and market demand.
(1) single-stage hammer crusher system
Single-stage hammer crusher system is composed of hammer crusher and screening system.
The process is simple; easy to maintain and manage; less land occupation; low project investment; low energy consumption per unit product.
The product variety ratio is not easy to adjust, the adaptability to ore is poor, and the scope of use is narrow; the product has a poor grain shape, and contains large amount of fine powder, and has low product acquisition rate; the crusher requires a large amount of dust collection; the consumption of wear parts is high.
(2) Jaw crusher+ impact crusher system
This system is composed of jaw crusher, impact crusher and screening system. The advantages of this system are the system has many specifications in capacity and has wide applications; the product variety ratio is easy to adjust; it is suitable for materials with medium abrasion index.
Disadvantages: higher energy consumption per unit product; poor adaptability to raw materials with high abrasion index, medium product shape, medium acquisition rate of coarse-grained aggregates; large dust collection air volume required by the crusher; higher consumption of wear parts than cone crushers.
(3) Jaw crusher+ cone crusher system
This system is composed of jaw crusher, cone crusher and screening equipment.
The advantages of this system are:
Product variety ratio easy to adjust; Suitable for materials with high abrasion index; Good particle shape, small amount of fine powder, high production rate of coarse aggregate; The dust air volume required by crusher is small; Low energy consumption per unit product; Low consumption of worn parts.
Cone crushers have fewer specifications. When the system capacity requirements are large, three-stage crushing or more crushers are required. At this time, the process is complicated and the project investment is high; its application range is relatively narrower than impact crushers.
(4) Jaw crusher+ impact crusher+ vertical shaft impact crusher system
This system is composed of jaw crusher, impact crusher, vertical shaft impact crusher and screening equipment. The process of this system is basically the same as jaw crusher+ impact crusher system, except that a vertical shaft impact crusher is added in this system to meet the needs of high-quality aggregate products of customers.
In addition to the advantages and disadvantages of the jaw crusher + impact crusher system, this system also has some characteristics: it can provide multi-quality aggregates to meet different requirements of customers. Vertical shaft impact crusher can also produce artificial sand. But the process is complicated, the project investment is high, and the unit product energy consumption is high.
(5) Jaw crusher+ cone crusher+ cone crusher system
This system is composed of jaw crusher, cone crusher, cone crusher and screening equipment. The process of this system is basically the same as jaw crusher+ cone crusher system, except that a cone crusher is added in this system.
In addition to the advantages and disadvantages of the jaw crusher + cone crusher system, this system also has some characteristics: it can meet the requirements of large output capacity; but the process is complex and the project investment is high.
1.3 screening equipment
In sand and gravel aggregate production line, we can set pre-screening equipment before coarse crushing equipment to separate the fine particles that do not need to be crushed and soil out. This can not only prevent the crushing of fine materials to increase energy consumption and increase powder, but also can remove the soil to reduce the dust in the subsequent process, but also can improve the quality of aggregate.
1.4 buffer stockpile or buffer bin
Set semi-product pile between coarse crushing and medium& fine crushing equipment and the function of this semi-product pile is to balance the overall capacity of the aggregate production line and ensure the continuous production of the plant while coarse crushing equipment is overhauled.
In addition, the exploitation of most mines is in day shafts for safety. The downstream aggregate producing workshop can still produce in two shifts to flexibly meet the market demand, and the number of equipment can be reduced by half or the equipment with smaller production capacity can be selected to match the upstream equipment, which can also reduce the investment accordingly.
The design points of the screening system mainly include:
Reasonable selection of screen area;
The chute between the upstream belt conveyor and the vibrating screen must be designed correctly to ensure that the raw materials can be spread on the entire screen;
The specifications of dust collector should be reasonably configured to ensure to meet environmental protection requirements;
The chute between the vibrating screen and downstream belt conveyor should be considered abrasion and noise protection.
Sand production system
Sand production system is mainly composed of shaping sand making machine, vibrating grading screen, grading adjustment machine and air screen. The main design points of sand production system are:
The closer the particle size of raw material fed into sanding machine is to size of the product, the higher the efficiency of sand making. Therefore, try to use raw materials with a smaller particle size during production instead of over-spec raw materials.
The moisture content of the raw material fed into the air screen should not exceed 2%, otherwise it will affect the separation efficiency of the air screen. For rainy areas, while designing the sand production system, rain protection measures should be considered.
Storage and delivery system
The finished products are generally stored in sealed steel warehouses (or concrete warehouses) and steel structure sheds. The corresponding delivery system of the storage warehouse is an automatic car loader, and the corresponding delivery system of the steel structure greenhouse is forklift truck loading.
The per-unit storage investment of steel warehouse is higher than steel structure shed, but it has less dust emission and the automatic loading efficiency is high. Steel structure shed has lower per-unit storage investment, but its working environment is poor and the loading efficiency is low. In areas with strict environmental protection requirements, sealed steel warehouse (or a concrete warehouse) is preferred, which is more conducive to environmental protection acceptance.
Dust removal system
The dust removal system consists of two parts: water spray dust removal and bag dust collector. The function of the water spray is to produce less dust, and the function of the bag dust collector is to collect the dust.
In sand and gravel aggregate production line, water spray devices are generally installed in the head funnel of the belt conveyor in the discharge bin and each transfer station. If the finished products are stored in a steel structure shed, a water spray device is also needed.
The main design points of the water spray device are: the position and quantity of nozzle should be reasonable; the water volume can be adjusted and the water pressure can be guaranteed. Otherwise, the dust reduction effect is not obvious and the screen hole of the vibrating screen is easy to block, which will affect the production of the whole plant.
The main design points of the bag dust collector are: the specifications, quantity and dust collection ducts of the bag dust collector should be designed reasonably, and the dust collection must be stored in a separate storage and should not be returned to the production line to avoid secondary dust generation downstream.
The system process of the sand and gravel aggregate production line should be determined according to the working condition, raw material properties, product shape and market demand etc.
For crushers, cone crusher has better product shape than impact crusher and impact crusher has better product shape than hammer crusher.
The sealed steel warehouse (or concrete warehouse) for the storage of finished products is more environmentally friendly than the steel structure shed, which should be preferred in areas with strict environmental protection requirements.