超临界流体萃取天然产物传质模型

为开发超临界流体萃取天然产物过程简单可靠的传质理论模型，对其传质机理进行了分析，由微分质量衡算方程经合理简化得到了动力学模型的解析解.定义了新准数B_z(可以确切地表征萃取过程的动态传质状况)和特征时间t_k，当t=t_k时，-dr_c/dt取得极小值，其原因可能是由内扩散传质阻力与内扩散传质推动力（浓度差）相竞争的结果.采用此数学模型计算了完全萃取时间t_ex、萃取收率Y随时间t的变化以及流体流率Q对萃取收率Y的影响，计算结果与文献中的实验数据吻合良好.本模型简单可靠，可用于超临界流体萃取天然产物过程的预测、分析、设计、模拟和优化.

Mass transfer model of supercritical fluid extraction of natural products

The mass transfer mechanism of extracting natural products with supercritical fluid was analyzed and the analytical solution of the dynamic model of supercritical fluid extraction was deduced through rationally simplifying the differential mass balance equations. A new dimensionless number Bz was proposed to characterize the dynamic mass transfer conditions of the process accurately, and a characteristic time tk was found that -drc/dt reaches the minimum value when t=tk, which might be the competing results of intraparticle diffusion resistance with intraparticle mass transfer driving force. The complete extraction time tex, cumulative extraction yield Y as a function of time t and the influence of flow rate Q on extraction yield Y were calculated with the model. The results of calculation fitted well with the experimental data of literature. This simple and reliable model could be used to predict, analyze, design, simulate and optimize the process of extracting natural products with supercritical fluid.