介电材料辅助的微波冷冻干燥的实验研究

Experimental Investigation on Freeze Drying with Dielectric Material Assisted Microwave Heating

设计、加工和装配了一套实验室规模的微波冷冻干燥装置,旨在实验验证介电材料对微波冷冻干燥液体物料的强化作用。介电材料用烧结的碳化硅(SiC),石英玻璃作为介电材料的参照物;甘露醇,一种典型的药物赋形剂被选为待干溶液中的溶质。实验结果表明使用介电材料可以有效地强化微波冷冻干燥过程。与传统冷冻干燥相比干燥速率大大加快,在试验条件下干燥时间可以节省20%。微波加热逐渐生效并且主要体现在干燥过程的后半部分。当溶液中的固含量很低或者固体物质具有很小的介电损耗因子时,如果不用介电材料,微波加热的效果不明显。

Aiming at experimentally verifying the beneficial effect of the dielectric material on freeze drying with microwave heating,a laboratory scaled microwave freeze drying apparatus was designed,fabricated and assembled.Sintered silicon carbide（SiC） was used as the dielectric material as well as quartz as a reference substance.Mannitol,a typical pharmaceutical excipient,was selected as the solute in the being freeze dried aqueous solution.The results show that use of dielectric material in microwave freeze drying can effectively enhance the freeze drying rate,and 20% of drying time can be saved compared with conventional freeze drying under the operating conditions examined.Microwave heating was found to take effect gradually,and the importance of microwave heating becomes more pronounced at the latter half period of drying.It was also found that,when the solid content in the solution being freeze dried is very low or the solid product has a very small dielectric loss factor,the effect of the microwave heating is not evident.