A new industrial process of NaHCO3 and its crystallization kinetics by using the common ion effect of Na2CO3

Abstract

Sodium bicarbonate (NaHCO3) has been conventionally manufactured by a carbonation synthesis from the reaction of sodium carbonate (Na2CO3) and CO2 in a carbonation column. To enhance the quality and the production yield of NaHCO3, it is imperative to carefully control supersaturation in the carbonation crystallization process and make NaHCO3 concentration of filtrate obtained from column bottom possibly least. A new method of NaHCO3 production was proposed with help of common ion effect by adding Na2CO3 as feed in filtering liquor. A cooling crystallizer was incorporated in the system after the carbonation tower to generate more NaHCO3. The crystallization kinetics of NaHCO3 including nucleation and crystal growth was experimentally and theoretically investigated in a continuous mixed-suspension-mixed-product removal (MSMPR) crystallizer cooled from 353 to 308 K. The effect of Na2CO3 concentration and additives on the crystallization of NaHCO3 was studied. The growth and nucleation rate GV=6.618×10-15σ0.290, B0=2.560×10-32GV-3.82MT1.11 were determined by moments analysis based on the experimental crystal size distribution (CSD) data. The kinetic parameters in two empirical equations were estimated by linear regression with the 0.290 of the relative supersaturation rate order, indicating that the meant surface integration and diffusion play an equally importance to the growth of NaHCO3 crystal. The growth rate order of −3.82 suggested that nucleation of NaHCO3 from the Na2CO3-rich solution in the MSMPR crystallizer was particle size-limiting.