Screening Small Particles by Fluid Bed Air Classification
Why Do We Screen Material for Particle Size? - Particle Size Separation
Particle size and size distribution are important in industrial processes since particle size distribution can impact product quality, product properties, material handling, and safety. For example, many fine powders are added to materials as fillers in paper, paint, rubber, plastics, and more. These fine materials do not just act as fillers, they also affect the properties of the final product. The particle size of the fillers can influence color, smoothness, stiffness, and strength of the product. For processes involving coating of granules, wide particle size distribution may lead to undesired agglomeration and result in uneven coating as well as wasted coating material. Difficulty in producing uniform liquid suspensions can result from wide particle size distributions. Also, solid materials with excessive fines may not flow well or may cause bridging. Finally, dustiness in material may pose safety hazards such as explosion risk and inhalation exposure. Because of these risks, additional environmental controls may be required which can result in additional costs.
Mechanical Sieving - Vibratory Screening vs. Fluid Bed Separation
The above discussion illustrates some of the reasons that sizing of solids during processing is so important. One of the simplest and most widely used methods of particle size separation in industry is mechanical sieving. With this method, the material being size separated is run though a series of vibrating screens with increasingly smaller openings. There are several downsides to this technique. For example, the sieving of very fine materials can be time consuming since the finer the material, the longer it takes to make its way through the vibrating screens. Another disadvantage of sieving is that the particles undergo many impacts with each other and with the screen material resulting in high attrition and additional dust. Also, the vibration of the sieves causes the dust to become airborne leading to possible environmental concerns.
A cost effective and efficient alternative to vibratory sieving of material is the use of a fluidized bed as an air classifier (separator). Fluid beds not only are efficient at separation, they often require lower capital costs and less maintenance, handle the material gently, and by design contain dust that is present. Presented here is a white paper on the use of fluid beds for air classification.White Paper on Product Quality with Air Separation
At Applied Chemical Technology, we have bench scale fluid bed systems for the testing of your material. Based on the results, our engineers, designers, and fabricators can build the fluid bed system suited for your materials and process. Contact us today for your personal consultation.