Experimental Study Of Hydrodynamics, Liquid Mixing And Mass Transfer Of Taylor Flows

In the catalytic reaction engineering, improvements in performance of the conventional multi-phase reactors such as a slurry bubble reactor and a trickle-bed reactor could lead to substantial benefits in applications. As a new type of multi-phase reactors, monolithic or structured reactor is an attractive alternative, owing to its lower pressure drop, higher rate of mass transfer and ease to scaling-up. The present work is aimed at studying the hydrodynamics, mixing and mass transfer performance of Taylor flows encountered in this type of reactors, so as to provide basics for the design, development and operation of such reactors.First, a capillary two phase flow system was set up and used for developing a double-sensor conductivity method of measuring two phase Taylor flow characteristics through a circular capillary, including bubble velocity, void fraction, bubble frequency and Liquid slug length. Compared with the method of image, the double-sensor conductivity probe method was found to be effective and feasible for the measurement purpose. Furthermore, the conductivity probe was used to identify the observed flow regimes, i.e., dispersed bubble flow, bubble-chain, slug or Taylor and annular flows. It is demonstrated that the conductivity probe method is effective for flow regime identification of capillary two phase flows.Second, the experimental results of Taylor flow in a capillary show that: with increasing the two-phase flow rate, bubble rise velocity increases correspondingly; gas holdup increases along with gas superficial velocity, but reduces with the liquid superficial velocity. Meanwhile, a cold model monolithic reactor was set up and primary measurements therein were implemented, showing the behaviors of flow pattern and pressure drop in the monolith.Finally, liquid mixing and liquid-side mass transfer characteristics in a capillary were measured by semi-saturated KC1 solution pulse trace and the dynamic dissolved oxygen methods, respectively. The results show that with an increase in either superficial gas velocity or superficial liquid velocity, both the degree of liquid mixing and the liquid-side mass transfer are increased due to an increased liquid circulation within liquid slugs and enhanced surface renewal on the liquid side.