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During the preparation period of a hydropower station, the aggregate processing capacity of the sand and aggregate processing system is about 1.2 million m³, and the raw material is basalt. Here we will share the difficulties and solutions of basalt crushing processing in this sand and gravel system.
1. Difficulties in basalt stone crushing processing
(1) Basalt has high compressive strength, good toughness, high hardness and strong abrasion resistance, so it is difficult to crush and process, which makes it difficult for the actual processing capacity of stone crusher to reach the output of the name plate.
(2) It is difficult to control the needle and flake content of the finished coarse aggregate within the specification requirements due to the poor particle shape of the aggregate after the basalt crushed by stone crushers, and there are many flakes.
(3) After processed by vertical shaft impact crusher, the content of stone chips and coarse particles in the aggregate of basalt with particle size less than 5mm is higher, the fine particles are less, the fineness modulus of sand is relatively large, and the content of stone powder is low; if the rod mill is used, the unit output is low, and the water consumption, steel consumption and power consumption are high, so it is difficult to make sand.
The stone crusher system is not only used for normal concrete, but also for roller compacted concrete. Due to the high content of stone powder (12% - 18%), it is difficult to select proper the sand making process.
2. Solutions for basalt stone crushing
In view of the difficulties of poor grain shape and high content of small and medium-sized aggregate after basalt processing, the quality of coarse aggregate is mainly controlled by the following measures:
① Measures such as medium fine crushing control crushing ratio, continuous feed gradation, full feeding and laminated crushing are adopted to control the particle shape quality.
② According to the characteristics of the highest content of needle and flake in the small stone after the basalt is crushed by stone crushers, the shaping measures are adopted for the small stone. After medium fine crushing, the first screening workshop produces not only small stone products, but also large and medium stone products.
The aggregate enters the ultra-fine stone crushing workshop, and after shaping, the finished materials of small stone and rice stone are produced in the second screening workshop.
Rod mill and vertical shaft impact crusher are adopted in the system. According to the characteristics of low sand forming rate, high fineness modulus of finished sand and low content of stone powder, following measures should be done.
(1) Increase the rotor speed of the vertical shaft impact crusher and the linear velocity of aggregate in the crushing chamber (65m / s for the system), so as to improve the sand forming rate and the stone powder content of the crushed sand, and reduce the fineness modulus of the sand;
(2) Adjusting the feed grading of vertical impact crusher can improve the sand production effect;
(3) The system has a high content particle size less than 5mm produced after coarse and medium stone crushers. These materials will enter into the vertical shaft impact crusher for shaping, so as to improve the quality of finished sand;
(4) The coarse particles (mainly 3-5mm) after vertical shaft crusher will further enter into rod mill to adjust the fineness modulus and stone powder content of the finished materials;
(5) The lower the moisture content of aggregate is, the better the sand making effect is. According to the characteristics, the whole dry process is adopted to improve the sand making effect of vertical shaft sand making machine. The system not only produces sand for normal concrete, but also sand for roller compacted concrete.
The biggest difference between sand for normal concrete and sand for roller compacted concrete lies in the content of stone powder. The stone powder content of normal concrete sand is 6% - 18%, and that of roller compacted concrete is 12% - 18%.