Quarry crushing is the most important procedure in aggregate production. The basic idea is a multistage crushing and sieving process in a closed cycle, when with the help of special equipment, the quarry stone is processed into different specifications of construction aggregates and manufactured sand, which are used in construction of roads, infrastructures, concrete production and other industries. In contrast to the usual rock breaking procedures, the quarry crushing process is standard, automated and safe. Starting with the preparation of the raw stone and ending with storing the ready product, all the stages of the process are closely interconnected in order to achieve high efficiency of the crushing process and uniform particle size and high quality of the ready aggregates. Below you will find the detailed description of the stone crushing process in a quarry.
Pre-Crushing Preparation: Control of the Raw Quarry Stone Quality
The quarry stone crushing process does not start from the starting of the crushers. The pre-processing of the stone before crushing is very important in order to ensure high efficiency of the process, low wear of the equipment and quality of the products, and that is why it is the basis of the whole production process.
At first, the blast operations are performed. Usually, the raw stone of the quarry is big and cannot be used in the crushing equipment directly. In order to separate and loosen the rock from the mountain the precise blasting is needed. In the course of the blast operations the size of the blasted rocks is strictly controlled – the size of the raw stone should be within 800mm not to create oversized blocks, which could clog the equipment, increase the load and lead to the creation of too many fines. If oversized rocks are left after blasting, then additional breaking should be performed beforehand in order to avoid the entry of oversized materials in the production chain.
Then the transportation and pre-screening of the raw material is performed. After the blasting, the raw stone is loaded by dump trucks in the feeder hopper of the crusher, where it is supplied evenly and continuously to the crushing equipment by the vibrating feeder. The vibrating feeder with the use of grizzly bars can perform the preliminary screening while supplying the material, automatically sorting out the soil, the fine sand and other impurities, which can be found in the raw stone. Thus, the material buildup, which affects the crushing accuracy and can block the feeding unit, is prevented.
Three-Stage Crushing for the Precise Processing of the Stone
The quarry stone crushing is performed according to the principle of "coarse crushing first, then fine crushing, and gradually size reduction". The three-stage crushing process is applied. At each stage special equipment for the handling of stones of different size and hardness is used, that is why this process is suitable for the processing of different kinds of raw materials – granite, limestone, river rock, etc.
Primary Crushing: Initial Reduction of the Raw Stone
The primary crushing is the first stage of the stone processing. It processes the big rocks produced after blasting and reduces them to the medium-sized material. At this stage the jaw crushers are applied. With a robust design and compression crushing principle, the jaw crushers provide high crushing capacity and high resistance to impact, that is why it is suitable for processing big and hard stones.
In the process of work the jaw crusher constantly squeezes the stone between the fixed and the moving jaw plates in the V-shaped crushing chamber. As a result of the repeated crushing, the big rocks, whose diameter amounts to hundreds of millimeters are reduced to the semi-ready products of a size less than 250mm. The primary crushing process is open circuit one – the strict control of the particle shape and the size uniformity is not required. The main task is to reduce the stone size and create the material with the uniform specification, which will be ready for the next crushing stages.
Secondary Crushing: Precise Size Reduction and Shape Improving
After the primary crushing the materials are transported with the belt conveyor to the secondary crushing equipment. At this stage the particle shape and size of the final aggregates are formed, and the choice of the equipment depends on the rock hardness and characteristics.For hard and abrasive rocks, like granite and basalt, the cone crushers are used. Applying the principle of lamination, the cone crushers perform the refinement of the stone by means of the constant pressure, providing aggregates with high strength, good compressive resistance and low wear rate. They are especially suitable for the processing of the big volumes of hard rocks.
For soft materials, like limestone and shale, the impact crushers are applied. Using the impact crushing principle, the machine performs the high-speed impact on the stone, and the materials collide with each other and break down. The aggregates with better shape, less sharp edges and good appearance are obtained, that is why this machine is suitable for the processing of high-quality construction aggregates.As a result of the secondary crushing the stone size can be reduced to 20–50mm, and the material is brought to the final specifications. This is how the transformation of the big quarry rocks into the refined aggregates is completed.
Tertiary Crushing: Further Processing for the Manufactured Sand Production
If the production of the manufactured sand or ultrafine aggregates is expected, then the third crushing stage is performed. For this purpose the sand-making machine is used. Using the high-speed impact, grinding and shaping process, the equipment produces the manufactured sand of 0–5mm.Also the shape of the aggregates is improved, and their particle gradation is optimized. The manufactured sand with balanced grading and good quality is produced.
Screening and Closed-Loop Processing: Grading Separation and Re-Crushing
Crushed stone cannot be used directly as a finished product and requires further screening and classification through vibrating screens for the formation of a closed production chain to exclude unqualified material from the product flow. Vibrating screens are equipped with several layers of mesh of different openings that make it possible to classify several types of aggregate simultaneously.
Qualified materials are transported by conveyors to corresponding stockpiles. Oversize materials that do not fit the required specifications are returned to the secondary crushing machine through the return conveyor to crush again. This process goes on until required particle size is achieved.Closed loop production chain of "crushing – screening – return crushing" excludes uneven particle sizes and helps to guarantee consistency in the size of aggregates and their quality stability. High-standard production lines include also the system of water washing and equipment of fine sand separation to clean the stone surface from dust and other impurities and improve its purity, maximize the amount of recovered waste and implement environmentally friendly production.
Safety and Maintenance: Stable Operations of Quarry Crushers
Crushing of quarry stone is a dangerous industrial process and requires the standard safety management and maintenance of all the equipment involved in the process from the very beginning to the end of production. At the beginning of the work, workers have to inspect the condition of crushers, conveyors, vibrating screens and other machines, check for any problems with electrical system, bearing, screens and other wear parts and make sure that equipment works properly, without any obstructions and loose parts.During the work personnel should strictly avoid approach to operating machinery zones. Any improper feeding and introduction of foreign material such as iron blocks and metal debris is strictly forbidden to avoid blockage, destruction and malfunction of the equipment.In the course of the crushing process the operator has to monitor equipment temperature, operating noise and feeding speed constantly. In case of appearance of any abnormalities, including material blockage, abnormal noise and overload, equipment has to be stopped at once for inspection. Working with the faulty equipment is strictly prohibited.Also the quarry plant has to be equipped with the dust suppression and noise reduction system to avoid dust and noise pollution caused by crushing operations. After the end of the production process residual materials should be cleared out from the equipment and the lubrication and maintenance should be done to increase the service life of the equipment.
MP Mining Equipment Conclusion
Key elements of quarry stone crushing include scientific processing stages, proper equipment selection, closed loop screening and strict safety management. Starting from the blasting control and preliminary screening, up to jaw crusher primary crushing, cone or impact crusher secondary crushing, sand-making and screening-classification with re-crushing stages, the whole production line gradually turns huge raw quarry stone into different types of qualified aggregates.Standardized crushing process increases production efficiency and decreases production cost significantly. Besides, it allows to provide qualified finished aggregates. The process of quarry stone crushing provides reliable material supply for construction projects implementation and allows to achieve safe, environmentally friendly and highly efficient large-scale quarry production.Quarry crushing line configurations vary by rock hardness, site conditions and production requirements. Improper equipment selection may cause low output and poor aggregate quality. If you need professional crushing plantn, crushing equipment selection and customized quotation,please contact MP。
