在谷氨酸分批等电结晶过程中,添加晶种与否直接影响产品的粒度分布(CSD)。通过在谷氨酸结晶过程中添加不同晶种的方法,研究晶种表面积及其粒径对结晶的影响,以期获得谷氨酸分批等电结晶中添加晶种的最优条件。实验结果表明,对于平均粒径不同的晶种,添加的晶种表面积存在临界值Sc使得此时得到的产品粒度分布均匀,中位径(D50)最大。当晶种平均粒径位于67.3～91.9μm,晶种表面积为50 cm2时得到的产品D50最大、CSD最好,即该晶种粒径对应的Sc不大于50 cm2;晶种平均粒径位于103.7～117.7μm时对应的Sc为100 cm2;晶种平均粒径为154.8μm时对应的Sc不小于250 cm2;当晶种平均粒径大于235.9μm时得到的CSD为双峰。表面积相同时,与粒径小的晶种相比,粒径大的晶种破碎率大、吸收溶质的速率小,所以晶种粒径越大表面积临界值越大。

In the process of batch isoelectric point crystallizaton of L-glutamic acid,the crystal size distribution(CSD) will be directly influenced by addition of crystal seeds.This work aims to determine the optimal conditions for seeding operations.Effects on crystallization are studied by adding seeds with different surface area and different average size.Results show that the CSD can be controlled if the seed surface area reaches critical surface value(Sc).When the average seed size ranged from 67.3 μm to 91.9 μm,the Sc was not more than 50 cm2,and the corresponding Sc was 100 cm2 for the region of 103.7 μm to 117.7 μm,and the corresponding Sc was 250 cm2 for the average seed size of 154.8 μm.When the average seed size beyond the 235.9 μm,the CSD of the final product are bimodal.As for the seed size,at the same seed surface area,the seeds with larger size have higher crushing rate and lower absorption rate for solutes,thus have greater critical surface value.