Hydrodynamics Performances In A Jet Intensified Reactor

In order to achieve energy saving and green chemical engineering process, improvement and application of new reactors are proved to be a proper way way. As a type of highly mixing reactor, the JIR (Jet Intensified Reactor) has many advantages, such as simple structure, easy controlling, no leakage, high efficiency and safety performance. Its performs better than conventional reactors in many fields, and unfortunately, the systematic study on the hydrodynamic features greatly restricts the industrial application.One of the key determinants of hydrodynamic features for JIR is the structure of downcomeron which little attention has been put. Downcomer structure of a ejector directly affects the gas distribution in the reactor, gas holdup, gas entrainment rate, the bubble Sauter mean diameter, as well as the gas-liquid interfacial area.In view of the facts discussed above, this dissertation will focus on the study of JIR’s downcomer structure and its influence on the reactor hydrodynamics. Seven different downcomer structures were designed and tested to reveal the influence of downcomer. A CCD(Charge Coupled Device) camera was used to obtain the real images of bubble distribution inside the reactor. DIA(Digital Image Analysis) technique was applied to analyze the images and obtain information such as the bubble Sauter mean diameter, gas liquid interfacial area, gas hold up, gas entrainment rate and other hydrodynamic relevant parameters.Achievements obtained in this study are shown as follows:The single bubble with free rising velocity was observed and compared with the theoretical calculation according to model proposed by Fan. It was found that:the experimental value and the theoretical value are in good agreement; the liquid viscosity, surface tension, density and other physical properties have magnitude impact on the single bubble free rising velocity. With the increasing of viscosity, the free rising velocity of single bubbles decreases rapidly. The bubble size distribution inside the reactor under different operating conditions were obtained by DIA software developed cooperatively with HTU. Then a preliminary verification of the bubble Sauter mean diameter theoretical model was made. The study found:at low liquid circulation flow rate (0.5～1.3 m3/h) model predictions are more accurate; in the liquid circulation flow rate 1.3 m3/h or more, due to bubble coalescence, bubble Sauter mean diameter differs from the theoretical model calculate value. At the same downcomer open area, the smallest bubble Sauter mean diameter was presented with 8 holes.The gas hold up, gas entrainment rate and gas-liquid interfacial area in the JIR were also measured. The measured values were in good agreement with theoretical model proposed by my group, indicating that the theoretical models can guide the design of the such reactors.Based on the experimental results, gas liquid interfacial area per energy unit first increased then decreased with a rise in liquid flow rate. There exist an optimal liquid circulation flow rate 1.0m3/h for the tested JIR.