What is the influence of powder separator on cement qualityDate: 2019-06-25 Views:
Ball mill is equipped with powder separator production, called closed circuit circulation system. The function of the separator is to separate the qualified products from the fine powder with a certain particle size, and the coarse powder can be returned to the mill for re-grinding, and it can prevent the buffer effect caused by the fine powder in the grinding body, improve the grinding efficiency of the mill, adjust the particle composition and prevent the uneven phenomenon of the fine powder, so the powder selection function ensures the quality of the grinding. The comprehensive performance of the powder separator depends not only on its powder separation efficiency, but also on the percentage of 3 ~ 30 μ m particles in the finished product separated by it. Because the particles in this section are the best cement strength. Part of the The efficiency of powder selection not only affects the output of mill, but also has a great relationship with the quality of products.
Too low powder separation efficiency will not only restrain the improvement of mill output, but also directly affect the quality of the product. The φ 2.4x7m cement mill in a cement plant in Guangxi is equipped with 4.0m centrifugal ordinary powder separator. The output is only 17 tons per hour, and its specific surface area is high, but the cement strength is low. The reasons are as follows: one is that the medium φ 2.4x7m mill is equipped with 4.0m powder separator, the other is that the powder separation efficiency of this centrifugal separator is low, only a little more than 30%. This situation not only stifles the output of the mill, but also seriously overgrinds the mill. According to the test, the particles below 3 cm account for 5%. About 0%, because the particles in this section have little effect on the formation and growth of cement strength. Therefore, the specific surface area is higher and the strength of cement is lower. The general requirement of particles below 3 μ m is less than 10%.
The high powder selection efficiency can increase the output of the mill, but the quality of the cement has a great effect. The 1 # cement mill of a cement plant in Sichuan province, using the cyclone type rotor type powder separator, the fineness of the cement is controlled between 1.5% and 1.8%, the specific surface area is only 240-250 kg/ kg, and the strength of the 3d and 28d of the cement can not reach the control requirement at any rate. The main reason for forming such a low specific surface area and low strength is that because the powder selection efficiency of the powder separator is too high, the proportion of the separated finished product 3 to 30. m u.m is too small, and the particles of 30 to 80. m Because of the large proportion. In order to meet the requirements of the new national cement standard, the two sets of 2.2×6.5m cement mills in a cement mill in Hebei Province are equipped with 3.5m centrifugal separator and 500 rotor-type separator respectively. In order to meet the requirements of national cement standard, they set the fineness control index of 3.5m centrifugal separator as 4%~5%, and the fineness control index of 500-type rotor-type separator is set as 2%. The output at the two mills is basically the same as the specific surface area of cement produced by the two mills, which also shows that the powder separator is too high and the specific surface area is reduced.
What is the most favorable requirement for the specific surface area and strength of cement when the powder selection efficiency reaches? After many experiments and comparisons, we think that the powder separation efficiency of the closed circuit mill system for cement production should be controlled at about 60%-65%, and the maximum should not exceed 70%. The proportion of 3 ~ 3 μ m particles in the finished product can be larger, which can exceed 65%. The overgrinding phenomenon will not be formed because of the low powder selection efficiency, and the strength of cement will not be reduced because of the high powder separation efficiency.
Product fineness index and specific surface area index are control means, through these means, to achieve the purpose of 3D and 28d strength index, and finally meet the requirements of the new national cement standard.
Through the above analysis and demonstration, we want to meet the requirements of the new national cement standards, too high powder selection efficiency will force you to reduce the fineness control index of the product. Of course, the production of the mill will also decline at the same time. If the powder separation efficiency is too low, the output of the mill will not be very high, and the phenomenon of overgrinding will be formed, which is likely to have a higher specific surface area. At this time, we can not just look at the specific surface area, if the proportion of particles below 3um is large, the cement strength decreases.