Volumetric mass transfer coefficient in the fermenter agitated by Rushton turbines of various diameters in viscous batch
Volumetric mass transfer coefficient in the fermenter agitated by Rushton turbines of various diameters in viscous batch
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DOI：
10.1016/j.ijheatmasstransfer.2017.07.112
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发表时间：
2017-12
影响因子：
5.2
通讯作者：
R. Petříček;T. Moucha;F. Rejl;L. Valenz;J. Haidl
中科院分区：
文献类型：
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作者：
R. Petříček;T. Moucha;F. Rejl;L. Valenz;J. Haidl
在需氧发酵的情况下，用于其工业性能的设备也从足够的氧气供应的观点来设计，以避免生物质的氧气限制，即提供足够的氧气-液体转移速率。对于具有高呼吸速率的生化过程，其需氧量也很高，通常使用机械搅拌容器。与气升式反应器和鼓泡塔相比，这些设备能够达到更高的氧气-液体传递速率，即，它们达到更高的体积传质系数k L a值。由于机械搅拌的气液系统的流体动力学的复杂性，从第一原理的k L a的预测是不可靠的，因此，实验数据是需要合理的设计发酵罐。大多数发酵液具有增加的粘度，由于大多数测量方法的限制，因此缺乏可靠的k L a数据。我们最近建议和验证的方法，以获得可靠的实验k L的数据在粘性批次，即使是高耗散能量。我们使用的动压法（ESTA），其中的实验装置进行了修改，在粘性批次的测量。在我们以前的工作中，我们提供了相当大的k L a数据库，以建立合适的相关形状来描述k L a在粘性液体中对工艺条件的依赖性。现在，我们专注于叶轮直径对输送特性的影响，因为在剪切应力敏感的生物质的情况下，该参数强烈影响发酵效率。在多叶轮发酵罐中进行测量，实验室和中试规模，使用粘性牛顿批料在广泛的实验条件下（叶轮频率，气体流速，叶轮直径）。使用了各种直径的拉什顿涡轮机。根据实验数据，建立了工业发酵罐中k-L-a的关联式.标准相关系数k L a= 0.0024（P TOT）0.86 vs 0.49，SD 23%，基于充气功率输入P TOT和表观气速vs，具有低标准偏差。另一方面，当使用叶轮尖端速度（ND）的项而不是P TOT时，预测数据具有较高的标准偏差k L a= 0.29（ND）2.15 vs s 0.27，SD为37%，但是当考虑D/T比修改该相关性时，标准偏差显著降低。本文提出的相关式kLA = 1.14（ND）2.23 vs0.27DT1.3，SD25%，可用于工业发酵罐的精确设计。实验技术和相关形状都准备好用于获得具有不同粘度的其他批次的设计工具。
In cases of aerobic fermentations, the apparatuses for their industrial performance are designed also from the viewpoint of sufficient oxygen supply to avoid oxygen limitation of biomass, ie to provide sufficient oxygen gas-liquid transfer rate. For biochemical processes with high respiration rate, the oxygen demand of which is also high, mechanically agitated vessels are usually used. In comparison with airlift reactors and bubble columns, these equipments enable to reach higher oxygen gas-liquid transfer rates, ie, they reach higher values of volumetric mass transfer coefficient, k L a. Due to the hydrodynamic complexity of mechanically agitated gas-liquid systems, the k L a predictions from first principles are not reliable yet, and, therefore, experimental data are needed for rational design of fermenters. Most fermentation broths are of increased viscosity, for which the lack of reliable k L a data exists due to the limitations of most measurement methods. We recently suggested and verified the methodology to obtain reliable experimental k L a data in viscous batch even for high dissipated energies. We used the dynamic pressure method (DPM), the experimental set-up of which was modified for the measurement in viscous batch. In our previous work, we provided fairly large k L a database to establish suitable correlation shapes to describe k L a dependencies on process conditions in viscous liquids. Now, we focused on the effect of impeller diameter on transport characteristics because in cases of shear stress sensitive biomass this parameter strongly affects the fermentation efficiency. The measurements were conducted in multiple-impeller fermenters, both of laboratory and of pilot-plant scale, using viscous Newtonian batch under a wide range of experimental conditions (impeller frequencies, gas flow-rates, impeller diameters). Rushton turbines of various diameters were used. Based on the experimental data, the correlations were developed to predict k L a in industrial fermenters. Standard correlation k L a= 0.0024 (P TOT) 0.86 v s 0.49 with SD 23%, based on gassed power input P TOT and superficial gas velocity v s, has low standard deviation. On the other hand, when the term of impeller tip speed (ND) is used instead of P TOT, predicted data have a higher standard deviation k L a= 0.29 (ND) 2.15 v s 0.27 with SD 37%, but when this correlation is modified taking into account the D/T ratio, the standard deviation decreases significantly. The correlation k L a= 1.14 (ND) 2.23 v s 0.27 D T 1.3 with SD 25% suggested in this work can be used for the fairly accurate design of industrial fermenters. Both the experimental technique and the correlation shape are ready to be used to obtain the design tool for other batches with various viscosities.