Ferrite production with fluidized bed calcination

For the process intensification of ferrite production, fluidized bed calcination of raw-mix (RM) particles for strontium ferrite was tested in a laboratory scale fluidized bed. In cases when the bed was made only of RM particles, agglomeration took place above 900 K, and above 1350 K rapid defluidization was unavoidable. However, successful calcination with no defluidization was achieved by calcining RM particles in the bed of coarse spherical alumina particles. One kilogram of calcined product was produced by repeated batch calcination at 1423 K and with retention time of 60 minutes. The products were made into magnets and their magnetic properties were evaluated. The magnetic properties of fluidized bed product were compatible with rotary kiln products, although residue of unreacted Fe2O3 seemed to have detracted the former somewhat. The presence of unreacted Fe2O3 was found to be caused by the selective adhesion of SrCO3 on the bed material. A slight adjustment of Fe/Sr ratio in the RM was found to be effective in the elimination of such residuals.

Automated summary

The study found that using coarse spherical alumina particles as the bed material in a fluidized bed can effectively prevent defluidization during the calcination process and somewhat impact the magnetic properties. Adjusting the Fe/Sr ratio in RM was effective in eliminating unreacted Fe2O3 residues.