Growth and agglomeration of boehmite in sodium aluminate solutions

Abstract

Boehmite precipitation is a new alternative way from sodium aluminate solutions to alumina, however, the too small particle size becomes one bottleneck for this methods replacing the current production route. Growth and agglomeration of crystals are the main factors influencing product size. The results show that the growth rate of boehmite is in a low range from 0.08 to 2.4 µm/h. Thus, agglomeration of boehmite is a major means to enlarge the particle size of precipitation products from sodium aluminate solutions. By means of laser particle size analyzer and powder attrition index analyzer, the agglomeration efficiency was represented by combining agglomeration degree and attrition index. The influences of seed ratio, temperature, the molar ratio of Na2O to Al2O3 and organic additives on agglomeration were investigated. The alcohol type additives PPG increases precipitation ratio and agglomeration degree, but reduces the strength of products and makes attrition index increase.