High gas velocity in the orifices reduces and even eliminates the deposition of solids, and it is obtained a good distribution of gas due to a large pressure drop in the distributors. However, this may cause a considerable increase in friction of the particles.
Attrition in fluidized beds has been extensively studied, but its characterization is difficult because it depends on the particle under study.
The erosion is not usually a problem, but it is found at positions located in one of the following forms:
- Local erosion on parts of the distributors and walls of the bed occur mainly due to the direct impact of the gas jet exit and transport of particles. This can be avoided by limiting the length of the jet;
- Erosion at the nozzle or at the hole is often associated with deposition of solids. This can be limited by proper selection of operating velocities;
- Erosion of the parts of the distributors, such as caps, orifices, etc., may also be due to secondary circulation.
- Tuyeres with multilayer of identical orifices may have erosion due to the impact on the orifices. These particles are sucked by the tuyere through the small orifices because of the Venturi effect.