Static classifier

Types of static classifiers

A static classifier is a device used to separate fine particles from coarse ones based on size and density. Static classifiers work solely by gravity, positioning themselves above the burners. The static classifiers burrs or ledges inertially separate the particles; the finer particles enter the airstream and combust the furnace, while the coarser ones remain inside the mill for further grinding.

• Static Classifier with Knee Elbow

  Based on the cylindrical vessel's knee elbow design, the uneven distribution of gas flow and classifier internal surface friction promote the white ash separation process. Having just an elbow allows for quick installations and less equipment management. However, regular classifier cleaning is necessary. Despite this, classifier effectiveness will not be reduced.

• Static Classifier with Round Elbow

  The round elbow-based classifier allows a high classifier separation yield, partly at high gas velocities. The perpendicular curvature promotes smoother circular flow. Furthermore, the round elbow weighs and occupies less space than a knee elbow classifier, resulting in lower field logistics costs. However, the classifier may require more management to maintain its efficacy.

• Mamey or Guava-shaped classifier

  This static classifier has a mamey-shaped body and an adjustable blade, which allows for changing the size of the particles that will return for a new grinding process. Its main benefit is that it gives the mill operator the possibility of adjusting it to suit the needs of the work at that moment. On the other hand, the complexity of its adjustment and the need for an expert to do it are not to be overlooked.

• Static Classifier with Conical Cyclone

  In essence, the conical cyclone classifier creates a centrifugal force that separates the particles based on size and density. Here, the smaller ones pass through the upper outlet, and the larger ones fall back to the grinding mill. This type of classifier works at relatively high power and classifier separation yields. Besides, the classifiers consume little energy; they occupy less space and are easier to install.

Specifications and maintenance of static classifiers

Specifications

• Mesh Size

  The mesh size of static classifiers usually ranges from 50 to 2000 microns. Classifiers with small mesh sizes can separate fine particles, while those with larger mesh sizes can separate coarse particles.

• Processing Capacity

  The processing capacity of static classifiers is the volume of raw materials they can handle within a fixed time unit, typically represented in tons per hour (t/h). Processing capacities that suit different classifier designs and sizes range from small to large.

• Particle Distribution

  Static classifiers can separate particles into different proportions, such as the proportion of fine, medium, and coarse particles. This is determined by the classifier's structure, mesh size, and operating parameters.

• Power Consumption

  Static classifiers' power consumption is related to their processing capacity, separation efficiency, and the raw materials they handle. Power consumption is typically expressed in kilowatts (kW) or kilowatt-hours (kWh).

Maintenance

• Regular Inspection

  Regularly inspect the static classifier's appearance and components to check for signs of damage, wear, or looseness. If any issues arise, they should immediately be repaired or adjusted to ensure the normal operations of the classifier.

• Cleaning

  Periodic cleaning of static classifiers can remove dirt, dust, and particle residues that affect separation efficiency and classifier performance. Choose appropriate cleaning tools and methods to avoid damaging the classifier.

• Lubrication

  If static classifiers have lubricating components, such as bearings, regularly lubricate them according to the maintenance schedule or guidance. This ensures smooth operation and reduces wear and tear.

Scenarios of using static classifiers

A static classifier can be used in various industries. Some of them are listed below.

• Cement

  Cement plants depend on dynamic air classifiers for raw material grinding and optimal particle size distribution. Such classifiers assist in separating fines that fulfill cement quality requirements while returning coarse material to the mills for further grinding. This process not only ensures the quality of the final product but also enhances the overall efficiency of the milling operation.

• Steel

  Steel mills utilize dynamic classifiers to process iron ore pellets and other materials. These classifiers play a crucial role in achieving the desired particle size and boosting the yield of the final product. By employing dynamic classifiers, steel mills can improve the quality of their materials and increase the efficiency of their production processes.

• Food

  Dynamic classifiers find applications in the food industry for processing various food items such as sugar, flour, and salt, among others. The classifiers are employed to achieve specific particle sizes and improve the flow characteristics of the final products. By utilizing dynamic classifiers, food manufacturers can ensure that their products have the desired texture and are easy to handle and process.

• Powder Coatings

  In the powder coatings industry, air classifiers play a vital role in achieving the ideal particle size distribution of resin and pigment materials. These classifiers are instrumental in ensuring the consistency and quality of powder coating products. By utilizing air classifiers, manufacturers can produce powder coatings that meet stringent performance and aesthetic standards.

• Paints and Coatings

  Air classifiers are utilized in the paints and coatings industry to separate undesirable coarse particles from the final product. By employing classifiers, manufacturers can enhance the quality and clarity of their paints and coatings, resulting in superior end products that fulfill customer expectations.

• Plastics

  A plastic classifier plays a significant role in recycling plastics and processing virgin materials. It assists in achieving the desired particle size and removing contaminants from the plastic mixture. By using plastic classifiers, manufacturers can improve the purity and quality of their recycled materials, contributing to sustainable production practices.

How to choose static classifiers

When choosing static classifiers for an air separation system, it is essential to consider different factors such as the material being processed, the desired particle size distribution, and the classifier's efficiency.

• Material Compatibility:

  When choosing a static particle classifier, it is essential to consider material compatibility. The structure and design of the classifier must work well with the properties of the material being classified. Different materials have distinct features, such as moisture content, abrasiveness, and chemical reactivity. For example, if the material is prone to sticking or aggregating, one might need to choose a classifier with a different design to prevent clogs.

• Separation Needs:

  Separation requirements also play a role in determining material compatibility with the classifier. The classifier must be able to achieve the desired level of separation and yield. For instance, some classifiers are better suited for handling fine particles, while others are more effective with coarser ones. Classifiers that excel at separating fine particles may struggle with coarser material and vice versa. Additionally, the classifier must be able to handle the desired throughput or volume of material without becoming overwhelmed or ineffective.

• Classifier Efficiency:

  The efficiency of a static classifier, as well as the dynamic classifers, is typically evaluated using a variety of methods. The most common and straightforward classifier efficiency estimation method is to take the mass of the classifier feed and derive the aggregate classifier recovery for each size fraction in that mass.

Static Classifier Q and A

Q1: How does static classifier work?

A1: The static classifier works by allowing controlled airflow to pass through a fuel mixture in a conveying pipeline. The classifier's design enables the separation of fine particles from coarse ones by re-circulating larger particles back into the mill for further grinding.

Q2: What are the benefits of static classifiers?

A2: The benefits of static classifiers include reducing bandwidth, enhancing mill efficiency, allowing more grinding space, and lowering power consumption. Static classifiers also have lower operating costs because they do not require fans or other electrical equipment to operate.

Q3: What are the limitations of static classifiers?

A3: The limitation of static classifiers is that they can only separate particles based on their size. Therefore, they may not be able to separate particles of the same size but different densities or shapes.

Q4: Can static classifiers be used in all types of milling machines?

A4: No, static classifiers can only be used in mills designed to accept them. Therefore, before purchasing a static classifier for a milling machine, it is essential to examine whether it was designed to model to ensure static classifier effectiveness.