Study On Crystallization Of Sodium Gluconate

Sodium gluconate is a common, widely used organic salt. Evaporative crystallization is utilized in the purification of sodium gluconate. Both the solubility and viscosity of sodium gluconate for the crystallization system were high. And the current crystallization processes maintains high temperature and high concentration in the residue liquid, which led to unsatisfactory purity and yield of sodium gluconate as product. Study on the crystallization process will have practical significance to improve quality and production yield.The crystallization thermodynamics of sodium gluconate were studied in this paper. The aqueous solution density, viscosity and solubility empirical equations of sodium gluconate were fitted and obtained based on the experimentally measured data as followed:ρ=1146.34+590.46x-0.51T, The empirical equations were fitted well in the range of 30℃≤t≤70℃and 0≤x≤0.5. The effects of operating factors on the metastable zone width were studied. Experimental results show that the metastable zone width decreases with the increase of concentration and mixing intensity and decreases of cooling rate.The crystallization kinetics of evaporation crystallization of sodium gluconate were researched using the intermittent dynamic method. The results show that the growth of the sodium gluconate crystallization is related to particle size. The nucleation rate equation is that The growth rate equation can be expressed asDecolorization process of sodium gluconate crystallization mother liquor was investigated in this paper. The effects of the operating conditions of the evaporative crystallization on crystallization product quality were studied and the crystallization process were optimized. The conclusions are as follows:The decolorization of 40wt% sodium gluconate crystallization mother liquor should be operated in the flow rate of 15BV/h with the resin HZ806 and then mixed with the filtrated sodium gluconate fermentation liquid. The crystallization of the obtained mixture should be operated under the following conditions:Stirring intensity is 200rpm, Evaporation temperature is about 55℃, Addition amount of crystallization nucleus is 1%. The total crystallization yield reached 87.68% with the purity of 98.2% and average particle size of 462.3μm. Crystalline is good with narrow size distribution. The crystallization quality of the product is better than the factory product.