Superficial velocity trickle beds

As in the fluidized beds analysis (Section 3.8.3), a similar simplification has been made in Kunii-Levenspiel model for the material balances in the emulsion phase, where again the corresponding derivatives have been omitted (eqs. (3.529) and (3.530)). As in the case of liquid flow in trickle beds, the flow of the gas in the emulsion phase is considered too small and so the superficial velocities can be neglected. Thus, in trickle beds, from eq. (3.367),... 

The resulting gas (0.357 kg/m2 s) and liquid mass superficial velocities (2-12 kg/m2s) are within the operating region for commercial trickle beds (see Figure 3.47 and Satterfield, 1975). 

First, we have to check the wetting efficiency of the bed because the simple trickle-bed model assumes complete wetting and thus it is not applicable otherwise. By using the El-Hisnawi et al. correlation, the wetting efficiency can be estimated (eq. (3.411)). To do that, we need the Galileo number and the Reynolds number. The liquid superficial velocity can be evaluated as follows ... 

A trickle-bed reactor is to be designed to remove 75 per cent of the thiophene present in a hydrocarbon feed which contains 0.012 kmol/m3 thiophene. The bed of catalyst particles will operate at a temperature of 200CC and a pressure of 40 bar. Under these conditions the rate of the reaction may be assumed to be first order with respect to dissolved hydrogen and independent of the thiophene concentration. The superficial velocity of the liquid in the reactor will be 0.05 m/s. 

Suppose that the reaction takes place in a commercial trickle-bed reactor with D = 1 m and Z = 10 m and that the gas supeificial velocity is 0.02 m/s. The feed is H2 and 98% inerts. Tlie liquid mass superficial velocity vaiies between 2 and 12 kg/m s. 

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