Evolution of particle size and strength of hydrargillite from carbonization in seeded sodium aluminate liquors

Particles with high strength, low fine particle content and narrow size distribution are preferred in the Sinter Process. The particle size distribution and attrition index of gibbsite particles from sodium aluminate solution as a function of time have been investigated according to industrial carbonization conditions. It is shown that there is an appreciable distinction in particle size and attrition index between products precipitated at initial and final stages of the crystallization process. With the agglomeration and growth of gibbsite crystals in supersaturated liquors, the number of fine particles decreases and the particle average size increases to a stable value. The fine product precipitated early in the precipitation period has a low breakdown rate, but the rapidly aggregated product formed in the middle period has a lower strength than others, and the aggregated product, cemented by subsequently precipitated gibbsite shows an increase in strength. The product morphologies indicate that there are some superfine particles among the agglomerates, which are polycrystalline and show a “mosaic” type structure, different from the radial seed.