【摘要】 近年来发酵工业发展迅速,微生物发酵成为了获取目的资源的一种高效节能途径.在50L充气发酵罐内,选择生产岩藻多糖的阴沟肠杆菌发酵过程中第12,36,60 h的发酵液为研究目标,通过流变仪测量发酵液流动特性,使用CFD-PBM(Computational Fluid Dynamics-Population Balance Model)耦合模型对三层搅拌罐中的气液两相流动和气泡破碎聚并进行了数值模拟,并以功率消耗和混合指数定量评价混合效果.结果表明:3个阶段的发酵液流变曲线均满足幂律流动特征;在搅拌过程中,发酵罐内形成了3个流动循环,气泡尺寸范围处于1～25.19 mm之间;发酵液黏度的上升使功率消耗和气含率增加,同时使发酵罐混合效果变差. CFD-PBM耦合的模型对于中型搅拌罐中的气液分散状况具有很好的模拟效果,能为生物搅拌罐的实时监测与控制提供参考和指导.更多还原

【Abstract】 In the recent years, fermentation industry has developed rapidly, and microbial fermentation has become an efficient and energy-saving way to produce target resource. In this paper, a 50 L stirred tank was selected, and the fluid was fermentation liquid of Enterobacter cloacae at 12 th hour, 36 th hour and 60 th hour, which was to produce Fucoidan. The flow characteristics of the fermentation liquid were measured by a rheometer, and the CFD-PBM coupling model was used to numerically simulate the gas-liquid two-phase flow and bubble breaking and aggregation in the three-layer stirred tank. Power consumption and Mixing index are used to evaluate the mixing effect quantitatively. The result shows that rheological curve of the fermentation broth satisfies the flow characteristics of the power law curve. During the stirring process, three circulation flows were formed in the 50 L stirring tank. The increase of the viscosity in the stirred tank make the power consumption and gas holdup higher, but make the mixing effect worse. The bubble size distribution indicates that the bubble size distribution in the fermentation tank is between 1-25.19 mm. The CFD-PBM coupled model has a good simulation effect on the gas-liquid dispersion in the medium-sized mixing tank, and provides reference and guidance for the real-time monitoring and control of the biological mixing tank.更多还原