Development of combined models to describe the residence time distribution in fluidized-bed bioreactor with light beads

The modeling of bioreactors with immobilized cells is a complex process, incorporating in itself different complex operations. Depending on the design of the bioreactor and the biotechnological process are possible different combinations of mathematical models. Knowledge of the kinetics of biological processes and mass transfer are necessary to understand the basic principle of operation of the bioreactor. An important step in developing a complete model of the bioreactor is to explore and describe the flows’ structure in the working volume of the apparatus. For reactors with different flow and mixing characteristics are needed different methods for design, modeling and scaling-up. In this work an analysis of the experimental curves to determine the liquid residence time distribution (RTD) of liquid in the bioreactor was made. Based on this analysis, two different combined models of the flow structures were built. The study was done using specialized software RTD 3.14. The estimation of the models parameter was made using least square method. The algorithm permits parallel, serial and other kinds of connections of building blocks, including recycles. Directions of flows between blocks and flow fractions, when necessary, are set by user. The models are characterized with simple structure and with good ability to reproduce experimental results with high accuracy. They were built by plug flow and ideal mixing units, which is a prerequisite for easy and quick integration in the synthesis model of the fermentation process in the bioreactor. The developed combined models for RTD description will be used to establish a system for control of the ethanol fermentation with immobilized cells. Thus, the impact of flow hydrodynamics will be render in account on the fermentation process.