Freeze Drying Preparation Of Ultrafine Sodium Bicarbonate Technology Research

In order to obtain the superfine NaHCO₃ powers with high quality, the technology of freeze-drying is adopted in this paper. And the feasibility and technology regularity of superfine NaHCO₃ by the preparation method of freeze-drying were studied. Based on the experimental research, the way to optimize technique parameter and increase productive efficiency is discussed.The superfine NaHCO₃ powers are obtained by the three most important steps:precursor solution preparation, solution freezing and its freeze-drying. All powers synthesized are detected by XRD,laser particle size analyzer and SEM. The results shows that all powers synthesized by the freeze-drying in this thesis are composed of small and even diameter, narrow granularity distribution, weak agglomeration, easy dispersal and weak crystallization.Three kinds of freezing styles of precursor solution:solution-direct freezing, vacuum evaporation freezing and spray freezing-are used in the synthesis experiment. The particles are finer and more uniform by spray freezing than the other two freezing styles. while injection pressure is the greatest impact, followed by solution concentration. It is found in the experiment that conditions with fast freezing rate and low solution concentration are in favor of getting superfine NaHCO₃ of small particle size.In the paper, the influence of process conditions upon productive efficiency is studied, too. The result shows that faster freezing rate, thinner materials thickness and larger sublimation proportion are benefit to increase the rate of evaporation and shorten freeze-drying time., while the materials thickness is the key factor.5% tert-butyl alcohol added in the precursor solution can change the crystallization modality of solvent, thus increase the rate of evaporation.