Abstract:

Accurate prediction of bubble size and volumetric mass transfer coefficient is very important for the scale-up design of aerated-stirred industrial bioreactors, and thus it is necessary to establish a suitable bubble coalescence and breakup model to ensure the efficient operation of the reactor. In this work, taking a 5 L aerated agitated bioreactor as a sample, and based on experimental data of bubble size and volumetric mass transfer coefficient, the effects of two coalescence models and five breakup models on the simulated flow behavior and mass transfer capacity were investigated. The results show that the combined simulation results of the modified coalescence model proposed based on the mesoscale and the breakup model considering viscous shear are in the best agreement with the experimental data, this provides a model basis for the paddle type optimization of large bioreactors. Because industrial bio-fermentation is usually carried out in large bioreactors, where the stirring paddle type is crucial to the bioreactor efficiency, this paper enlarges the 5 L aerated stirred industrial bioreactor to 400 m³ by the principle of equal terminal shearing force of the impeller on the basis of the optimal bubble aggregation and fragmentation model, and the influence of the combination of six-vertical-leaf disk turbine impellers, asymmetric parabolic impellers, Blumarkin impellers and six straight-blade disk turbine impellers on the bubble breaking capacity and gas dispersion effect were discussed. The optimal model combination is further used to optimize the stirring paddle type of a 400 m³ large-scale industrial bioreactor, meanwhile, the optimal combination of 400 m³ aeration-stirred bioreactor is obtained by comprehensively comparing multiple parameters such as gas holdup and volumetric mass transfer coefficient.

Key words: bioreactors, computational fluid dynamics, scale-up design, coalescence model, breakup model, optimal design

摘要：

对于通气搅拌式工业生物反应器的放大设计而言，精确预测气泡尺寸和体积传质系数非常重要，因此需要建立合适的气泡聚并和破碎模型，以保证反应器的高效操作。以5 L通气搅拌式生物反应器为对象，以气泡尺寸和体积传质系数的实验数据为基准，模拟并考察了两种聚并模型和四种破碎模型对生物反应器内流体流动行为以及传质能力的影响。结果表明，基于介尺度理论的修正聚并模型与考虑黏流剪切的破碎模型组合，所得模拟结果与实验数据吻合最好，这为大型生物反应器的桨型优化提供了模型基础。因为工业化生物发酵通常是在大型生物反应器中进行，搅拌桨型对生物反应器效能至关重要，故本研究在选定最优气泡聚并破碎模型的基础上，通过叶轮末端剪切力相等的放大原则将5 L通气搅拌式工业生物反应器放大到400 m³，同时考察了六斜叶圆盘搅拌桨、非对称式抛物线搅拌桨、布鲁马金式搅拌桨以及六直叶圆盘搅拌桨等桨型组合对气泡破碎能力和气体分散效果的影响，并通过综合对比气含率、体积传质系数等参数，得到400 m³通气搅拌式生物反应器的最优桨型组合。

关键词: 生物反应器, 计算流体力学, 放大设计, 聚并模型, 破碎模型, 优化设计