Summary: A complete sand and gravel aggregate production line is composed of crushing systems, screening systems, sand making systems, storage and conveying systems, and dust removal systems...
A complete sand and gravel aggregate production line is composed of the crushing system, screening system, sand making system (omitted if artificial sand is not required), storage and conveying system, and dust removal system.
Many customers wonder how to configure and design complete sand and gravel aggregate production line. Here are the key points.
Crushing system
1.1 Design points for the 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 installed at the bottom of the discharge hopper. This layout features good adaptability to materials under various conditions and ensures smooth discharge of crushed raw materials.
The disadvantage is that raw materials in the hopper press directly on the equipment, which imposes high requirements on equipment quality and increases manufacturing costs.
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 material contains excessive soil or has poor fluidity, material blockage is prone to occur and discharging becomes unsmooth.
1.2 Selection principle of crushers
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 of material crushing.
Ai: Abrasion index —— the wear extent of machine components induced by raw materials.
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.
Advantages:
The process features simple operation, easy maintenance and management, small land occupation, low project investment, and low unit product energy consumption.
Disadvantages:
The product gradation ratio is difficult to adjust, with poor ore adaptability and a narrow application range. The finished product has inferior particle shape, contains a large amount of fine powder, and yields a low product recovery rate. In addition, the crusher requires a large dust collection capacity and suffers high wear part consumption.
(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:
The product gradation ratio is easy to adjust; it is suitable for materials with a high abrasion index; it features good particle shape, low fine powder content, and a high coarse aggregate yield; the crusher requires a small dust removal air volume; it has low unit product energy consumption; and it has low wear part consumption.
Disadvantages:
Cone crushers have fewer specifications. When the system throughput requirement is high, three-stage or multi-stage crushing is adopted. At this time, the process is complicated with high project investment, and its application range is narrower than that of 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 that of the jaw crusher + impact crusher system, except that a vertical shaft impact crusher is added to meet customers’ demand for high-quality aggregate products.
Besides inheriting the advantages and disadvantages of the jaw crusher + impact crusher system, this system has additional features: it can produce aggregates of multiple quality grades to meet diverse customer requirements. 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 a sand and gravel aggregate production line, pre-screening equipment can be installed ahead of coarse crushing to separate out fine particles and soil that do not require crushing. 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
A semi-product pile is arranged between coarse crushing and medium and fine crushing equipment. It is used to balance the overall capacity of the aggregate production line and ensure continuous production during the overhaul of the coarse crushing equipment.
In addition, the exploitation of most mines is in day shafts for safety. The downstream aggregate production workshop can still operate on a two-shift basis to flexibly meet market demand. Meanwhile, the number of equipment units can be halved, or equipment with smaller capacity can be selected to match the upstream throughput, thereby reducing the corresponding investment.
Screening system
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 collectors shall be properly configured to ensure compliance with 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 the sand making machine is to the size of the product, the higher the sand making efficiency. 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 delivery system of the storage warehouse is an automatic car loader, and the delivery system of the steel-structured shed is forklift loading.
The per-unit storage investment of steel warehouses is higher than that of steel structure sheds, but they produce less dust emission and feature higher automatic loading efficiency. Steel structure sheds have lower per-unit storage investment, but their working environment is poor and the loading efficiency is low. In areas with strict environmental protection requirements, sealed steel warehouses (or concrete warehouses) are preferred, which facilitates environmental approval.
Dust removal system
The dust removal system is composed of two types of facilities: water spray dusters and baghouse dust collectors. 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 baghouse dust collector are as follows: the model specification, quantity and dust collection pipelines shall be reasonably configured; collected dust shall be stored separately and prohibited from returning to the production line to prevent downstream secondary dust emission.
Summary
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.
Cone crushers have better particle shape of finished products than impact crushers, and impact crushers are superior to hammer crushers in this regard.
The sealed steel warehouse (or concrete warehouse) for finished product storage is more environmentally friendly than steel-structured sheds, and thus should be prioritized in areas with strict environmental protection requirements.
Consultation
Get Solution