A new process to produce granular boric oxide by high temperature dehydration of boric acid in a fluidized bed

Beker U., Bulutcu N.

CHEMICAL ENGINEERING RESEARCH & DESIGN, vol.74, pp.133-136, 1996 (SCI-Expanded) identifier

  • Publication Type: Article / Article
  • Volume: 74
  • Publication Date: 1996
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.133-136
  • Istanbul Technical University Affiliated: No


The production of boric oxide has only been achieved as a hard, compact or spongy mass that requires crushing and grinding operations before utilization. This paper represents the production of pure and granular boric oxide by high temperature dehydration of boric acid in a fluidized bed. Such dehydration is incomplete since agglomeration starts at 603 K, and to avoid agglomeration the boric oxide particles have been covered with a material that has a higher melting point than boric oxide itself. In order to achieve this high melting cover, a mixture of boric acid and alkali berate has been fed into a fluidized bed. During dehydration, the proper percentage of alkali berate has been determined by examining the behaviour of different mixtures. As the percentage of alkali berate increases, a more homogeneous cover has been formed on the surface of boric oxide particles. This causes the agglomeration temperature of the end-product to shift to 728 K. A two stage dehydration process has been investigated to reduce the dehydration residence time and to make the process continuous. As a result, granular boric oxide of 99.85%-99.90% purity and containing 0.10%-0.15% Na2O has been produced.