2000 Volume 26 Issue 6 Pages 823-829
An iron oxide bubbling fluidized bed reactor in the direct causticizing process, which constitutes the main part of the process, is developed. Its optimum operating conditions and reaction characteristics were investigated through a 500mm sq. bench scale test. In this process, high-grade iron oxide, whose diameter is 0.2-1.0mm was used as causticizing agent as well as the bed material. Concentrated black liquor was fed over the bubbling iron oxide bed by means of a spray nozzle at the temperature of 1, 173-1, 273K. Reacted sodium ferrite was hydrolyzed to recover sodium hydroxide and residue iron oxide was recycled. During the reaction in the bed as well as hydrolysis, iron oxide particle is gradually attritted so that the operation of fluidized bed becomes difficult. A portion of the iron oxide fine particles was pelletized by compaction before it was recycled to the reactor. The minimum ratio of fines to be pelletized is found to be 50% to maintain the bed as well as to recover sodium from black liquor through 40hrs' of continuous operation of the bench scale test.