Dynamics of Countercurrent-flow Fixed-bed Column

In spite of the widespread use of fixed-bed reactors, much remains to be done to define the dynamics of the reactor [30], Most of these reactors are operated in the concurrent mode at which the gas and the liquid both flow from the top to the bottom. A number of flow regimes have been distinguished for packed columns in downflow operation [31, 32], Based on the Reynolds number for liquid and gas flows, the flow regimes include (i) trickle flow, (ii) pulsed flow, (iii) dispersed bubble flow, (iv) wavy flow, and (v) spray flow (Figure 12.7) [17]. In general, countercurrent flows lead to much larger pressure drops across the bed, and this would be the case for FTS. Thus, the countercurrent flow mode is not used in today s plants. 

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