454217 Integration of CFD and Polymerization for an Industrial Scale Cis-Polybutadiene Reactor
Integration of CFD and Polymerization for an Industrial Scale Cis-polybutadiene Reactor
Chao-zhong Xu, Jia-jun Wang, Xue-ping Gu, Lian-fang Feng
State Key Laboratory of Chemical Engineering, College of Chemical & Biological Engineering, Zhejiang University, Hangzhou P.R. China 310027
Abstract A major objective of polymerization reaction engineering is to understand how the reaction mechanism, the physical transport processes, reactor configuration and operating conditions affect the polymer properties that assessed product quality. In particular, cis-polybutadiene polymerization in industrial scale reactors becomes quite complicated due to complex mechanism and metastable behaviors. However, computational fluid dynamics (CFD) is barely exploited to forecast the polymer product quality in the general modeling approach though some efforts have been done toward a better understanding of polymerization process. Hence, modeling polymerization by CFD, which takes polymer quality indices into consideration, still remains very challenging and significant.
A CFD model coupled with polymerization kinetics was developed to investigate butadiene solution polymerization using three-component system (Ni, Al, B) as catalyst and raffinate oil as solvent not previously available for a 12 m3 industrial scale reactor equipped with a double helical ribbon agitator. The integration of kinetic model with two catalytic active sites and CFD model was accomplished by solving continuity, momentum, energy and species equations simultaneously, in which the reactive source terms related to polymerization were implemented by a user-defined function with the method of moments. Model validation was successfully conducted by comparing CFD results with plant data and the developed model was further extended to discuss the effects of operation conditions including inlet temperature, impeller as well as inlet flowrate of solvent, and finally shed light on the differences of reactor behaviors from ideal CSTR model.
The simulation indicated that the reactor behaviors with double helical ribbon agitator were very similar to traditional CSTR model in the middle and the top of the reactor, while at the inlet near the reactor bottom, there apparently existed a deteriorated area for polymerization in the present production process. The distinction between double helical ribbon agitator and frame impeller mainly embodied in axial circulation capability and it seemed to be easier to keep the uniformity of polymerization process when helical ribbon agitator was used. It was also found when compared with inlet temperature, the fluctuation of reactor performance was more sensitive to inlet flowrate of solvent and therefore it was more advisable to regulate the inlet temperature for normal operations in industrial production in most cases. The results showed the proposed method could be served as a guidance to achieve a better control on cis-polybutadiene production, thereby maintaining the stability of polymerization process and optimizing the quality of products.
See more of this Group/Topical: Catalysis and Reaction Engineering Division