Vertical roller mill classifier improves the grinding materials fineness

The processing of most vertical roller mill production lines has four main steps: feeding, crushing, grading, and powder collection. To achieve the purpose of producing ultrafine powder, classification and powder collection are the core links, but the original vertical roller mill equipment generally has the following problems:

 

1) Powder classification is a bottleneck of the traditional vertical roller mill. It usually uses a fan-like classifier with fewer and narrow blades, a large impeller diameter and a wide blade gap, low speed, and low internal and external linear speeds. Uniform, poor seal design, large ash leakage, poor classification efficiency, large leakage of large particles, etc. In addition, the classification accuracy is also related to the air volume and air pressure matching of the air supply system. The blower of the traditional vertical roller mill is designed to produce powders below 325 mesh, large air volume and low wind pressure affect the effect of classification.

 

2) The powder collection system of the traditional vertical roller mill is realized by a cyclone dust collector. This single-cylinder cyclone dust collector is designed for powders below 325 mesh, and the efficiency of fine powder collection is very low. Although some small cyclones are added and the powder is collected twice, the amount of fine powder that runs away is still large, and the entire production line is running under positive pressure, and the dust overflows, causing environmental pollution and serious powder loss.

 

The results of vertical roller mill crushing studies show that the use of ultra-fine products mainly lies in the fineness of graded products. Crushing is a probabilistic process, and its products have a certain particle size distribution. Taking out products with acceptable fineness or removing unneeded large particles is an important step in obtaining a specified product. As the fineness of the required powder increases and the output increases, the difficulty of the classification technology becomes higher. The problem of powder classification has become the bottleneck restricting the development of traditional vertical roller mill production technology, and the dynamic seal between the classification rotor and the outlet is the key to ensuring the classification accuracy. Reasonable and accurate sealing can not only improve the quality of powder products, but also Greatly save the electric energy in the classification process.

 

The range of fine powder produced by the new vertical roller mill is determined at 3251-250 mesh, and the following measures have been taken to improve the traditional vertical roller mill:

 

1) Select a fine jaw crusher or adjust to reduce the jaw plate spacing of the original jaw crusher, reduce the particle diameter of the feed, and control the feed diameter of the material below 20 ~ 15mm;

 

2) Improved classification system is the core link of the new vertical roller mill. A large-scale vortex impeller classifier was used to replace the original recovered fan blade classifier, which was successful.

 

The main function of the classifier is to pass large particles with unqualified ratio, return to the mill and re-grind, and only pass qualified powder particles. The fewer large particles mixed into the finished product, the higher the classification accuracy. The size of the grading particles is related to the diameter and structural parameters of the grading wheel: the smaller the diameter of the impeller and the spacing of the blades, the smaller the diameter of the passing powder particles, and the output is also reduced. In order to meet the requirements of fineness and output of powder graded particles, the key technology is to select the appropriate impeller structure parameters, such as the width of the classification chamber, the diameter of the impeller, the thickness and spacing of the classification blades, the number of blades and the sealing treatment.

 

As a professional manufacturer of grinding mills, Shuguang Heavy Machinery sells a variety of different types of mill equipment, including ball mills, Raymond mills, vertical mills, etc.Welcome to contact us for more details.

 

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