Evaluation of a gas-liquid stirred reactor emulator via network models

Abstract

Backmixed stirred reactor has always been the first choice equipment for carrying out gas-liquid reactions. However, they may not be the best, mainly because of the non-uniform gas distribution in the vessel. Moreover, the gas liquid flow behaviour is not clearly understood partly due to the complex interactions between gas and liquid. Due to these reasons, a model which can first predict the internal behaviour of two-phase flow accurately is needed. A2-D experimental rig has been used to study the liquid flow behaviour. From photographic evaluations, valuable insight of the gas-liquid flow in the vessel is obtained. Two models have been tested to evaluate the experimental results. The models are able to predict the local gas hold-up, which is an important variable to predict gas-liquid flow pattern. The first model is the simple zones-in-loops based on the gas and liquid flowing in loops through a series of eight backmixed zones in the half 2-D stirred vessel. The second model is a more complex equal sized square cells network which accommodates a more realistic liquid flow pattern and thus, a more successful prediction of the two-phase flow behaviour. The predicted local gas hold-ups are exhibited on a unique 3-D spatial map. They display very encouraging predictive values in comparison with the experimental results. With improvements in the bubble detection techniques and also by assuming non-uniform bubble size the model has a potential to predict accurately not only the hydrodynamics characteristics, but also the physico-chemical interactions.