Crystallization kinetics of Na2CO3 in Bayer aluminate solutions during the evaporation process

Abstract

The inevitable Na₂CO₃ in caustic aluminate solution is the major component of scale formed in the evaporation process. A deeper understanding of the Na₂CO₃ crystallization kinetics in Bayer aluminate solutions during the evaporation process is necessary to further understand the scaling process. The kinetics of Na₂CO₃ crystallization in sodium aluminate solutions during the evaporation process were investigated in a continuously operated mixed suspension mixed product removal (MSMPR) crystallizer. Based on the particle size distribution (PSD) of crystals in the MSMPR crystallizer, a typical population density distribution curve of Na₂CO₃ crystals was obtained. Furthermore, an agglomeration population balance model was used to calculate the kinetic parameters through the population density distribution. When the initial content of Na₂CO₃ (N_c) is in the range of 17.54–26.32 g L⁻¹, the agglomeration kernel has a good linear relationship with the initial N_c, while the volume growth rate and the nucleation rate have an obvious quadratic polynomial relationship with the initial N_c. All the regressions of the parameters had an adjusted R squared higher than 0.9945.