Air-Jet Sieve for Particle Size Analysis

Particle Size Analysis Using an Air-Jet Sieve

Air-Jet sieving is a technique to determine particle size distribution of fine, dry powders. The Air-Jet sieve principle involves creating a vacuum powered, high velocity Air-Jet for fluidization of sample material and for pneumatic conveying of undersized material through the sieve. It is ideally suited for powders that agglomerate in traditional vibratory screens. This is especially the case for particle sizes less than 60 microns, for which Air-Jet sieves offer the perfect solution.

The method can use only one sieve at a time, and analysis is always started with the smallest size mesh in the range. The sample powder is spread uniformly over the mesh on the sieve, which is placed in a vacuum chamber and covered with a lid. The portion of the chamber below the mesh is connected to an industrial vacuum cleaner. Just below the mesh is a rotating slotted fresh air distribution nozzle. With the vacuum chamber closed and vacuum cleaner switched on, undersized material on the screen is sucked downward, through the mesh and into the vacuum cleaner. At the same time, fresh air jets-in through the rotating slotted nozzle, fluidizes powder on the mesh and redistributes it evenly, preventing agglomeration and mesh blockage. Thus, complete recovery of undersized fines is ensured. The change in weight of the sieve due to loss of undersized material is recorded. Oversized material retained on the first sieve is now completely transferred to a fresh sieve, to filter the next (larger) particle size. The Air-Jet sieve procedure is repeated until the sample has been completely classified by the full range of sieves.

A variation of the above method is the Swiss method in which multiple samples are used, one for each sieve in the stack. Each sample quantity should be representative and identical. Typical standard sieve diameters are of 200 and 203 millimeters and batch sizes range from 10 grams to 100 grams. The particle size distribution that can typically be covered, ranges from 20 microns to 5000 microns. Parameters such as vacuum level and speed of rotating nozzle can be adjusted and if needed a cyclone can be introduced between the Air-Jet sieve and the vacuum cleaner, to collect material passing through the sieves.

Common Uses of Air-Jet Sieve Particle Size Distribution Analysis

• Gravimetric size classification of dry powders 
• Quality control of raw material and products
• Control of batch processes involving solids handling

 Advantages of Air-Jet Sieve Particle Size Distribution Analysis

• Rapid and easy handling
• Enclosed and dust free measurements
• Accurate and reproducible gravimetric technique

 Limitations of Air-Jet Sieve Particle Size Distribution Analysis

• Suitable only for dry powders
• Loss of test material

 Industrial Applications of Air-Jet Sieve Particle Size Distribution Analysis

• Cement Industry
• Plastics Processing
• 3D Printing
• Pharmaceutical Industry
• Speciality Chemicals
• Food Industry