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40187-AC9
Interfacial Area Transport and Flow Structure in a Trickle Bed Reactor

Shripad T. Revankar, Purdue University

1. Objectives The main goal of this project is to develop a framework and a mechanistic model for the interfacial area concentration transport equation (IACTE) for a gas-liquid two-phase downward flow through a packed bed reactor. In support of this work new experimental data has been obtained on the flow structure in terms of local void fraction and interfacial area distribution. A one dimensional two-fluid model based IACTE is developed for packed bed flow application. Detailed pore level and bed level measurements on the two-phase structure are obtained for the source and sink term in the IACTE. The flow regime transition, void fraction distribution and interfacial area concentration, which are key parameters to characterize the packed bed performance, are evaluated using the IACTE. Thus the specific objectives of the proposed research are to: 1. Develop experiments for the study of the gas liquid two-phase co-current down trickle and pulse flow through the packed bed reactor. 2. Develop pore scale and bed scale two-phase instrumentation for measurement of flow regime transition, void distribution and gas-liquid interfacial area concentration in the packed bed. 3. Obtain database on flow regime transition, pressure drop, void distribution, interfacial area concentration and liquid hold up as a function of bed characteristics such as bed particle size and porosity. 4. Develop mechanistic one-dimensional IACTEs for gas-liquid trickle flow and pulse flow through the packed bed reactor. 5. Perform systematic evaluation of the interfacial area transport equations using experimental data. 6. Train graduate and undergraduate students in instrumentation, measurement methods and analytical modeling of two-phase flow through packed beds. 2. Extended Year Executive Summary The focus of the continuation of the extended year was on obtaining photographic data on the basic mechanism of bubble coalescence and disintegration in a two phase air-water flow in downward direction in the trickle bed reactor. Experimental data were obtained on the bubble coalescence and disintegration probability and its impact on the interfacial area and void fraction During this period of this project the followings have been completed. (1) A two-dimensional test section was designed and built to study the packed bed. The test section consisted of two transparent walls enclosing disc shaped packing arranged to represent a packed bed with effective porosity of 0.37. Figure 1 show test section details. The inlet of the packing has ports for injection of air and water. The air-eater mixes and generates a bubble flow in the 2-D packed bed. (2) High speed (500 fps) video records of the flow were taken for different flow rates of the air and water in bubble flow regime. Figure 2 shows a frame from a video record. The video records were digitized and analyzed for the bubble coalescence and disintegration processes. (3) A software program was developed to calculate the bubble shape and size, void fraction and interfacial area. The program also calculates the number of coalescence and disintegration frequencies. (4) Data was obtained on the types of coalescence and disintegration, probability of coalescence and disintegration and interfacial area change in the flow.

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