In the silica sand production, in addition to the normal product quality control measures, the control measures in the design of the production line should also be considered. This article mainly shares the control of needle flake finished materials, the control of stone powder content, and the control of moisture content of fine aggregate.
According to the standard of coarse aggregate for concrete, the needle-flaky shape of coarse aggregate should be less than 15%. The main control measures are the use of advanced crushing equipment and reasonable technological processes.
In silica sand production, the coarse crushing equipment generally chooses the jaw crusher, and some users choose the gyratory crusher as the coarse crushing equipment. Medium and fine crushing equipment is generally impacting crusher or cone crusher. The choice of equipment varies with material hardness. In comparison, the final aggregate of the impact crusher has less needle flake content, and the product has a better grain shape.
Studies have proved that in silica sand production, appropriately increasing the content of powdered stone is beneficial to improve the mixing performance of concrete and improve the comprehensive mechanical properties of concrete. For this reason, the following measures can be taken in the process design of the sand and gravel production line.
1. The sieved sand-water mixture passes through the grit chamber and then enters the spiral sand washer. The spiral sand washer selects a wide weir-type long spiral classifier to increase the length of the settlement area to reduce the loss of stone powder. At the same time improve the effect of dehydration.
2. The ultra-fine crushing workshop is for dry sand making. Check the screening workshop for dry screening to ensure the powder content of the sand.
3. Regularly check the content of stone powder in the sand, and make timely adjustments to the process and the mixing amount of stone powder.
According to relevant regulations, the moisture content of artificial sand should be less than 6%, and the fluctuation range of the moisture content should be less than 2%. Therefore, in the process design, when increasing the sand-making capacity and extending the sand-making table, partition storage and partition access are adopted, and the methods of pre-dewatering and natural dewatering are adopted.
1. Increase sand production capacity to ensure sand storage capacity and sufficient dehydration time.
2. Pre-dewatering, that is, a pre-dewatering screen is set at the tail of the belt conveyor that is transported to the finished sand storage yard, and the qualified sand after the screening is checked, discharged into the belt conveyor by the spiral sand washing machine, and then sent to the pre-dewatering screen by the belt conveyor.
3. The designed sand storage area has a large enough stock to extend the time for storage and dehydration. According to the test, when the stone powder content is 14.8% and the initial moisture content is 17.96%, the moisture content of the sand drops to 5.8% after 153 hours of storage. When the stone powder content is 17.95% and the initial moisture content is 16.59%, the moisture content drops to 5.93% after 186 hours of storage. The blind ditch is set at the bottom of the storage area, and a drainage ditch is provided outside the field to facilitate drainage.
4. Set a rainproof shed on the top of the sand pile area, and set a rainproof cover on the sand conveyor belt conveyor.
5. A water receiving pan and water receiving groove are set under the discharge port of the gallery in the sandpile area to intercept the seepage water outside the belt conveyor.
Taking the above measures can ensure that the moisture content of the finished sand is controlled below 6%.
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