Expressions of the overall effectiveness factor as a function of the wetting efficiency, the Biot numbers for the gas and liquid covered parts of the catalyst and the Thiele modulus have been developed for a slab, a cylinder and a sphere. The effect of particle shape on the overall effectiveness factor is discussed. Its significance over a wide range of wetting efficiencies. Biot numbers and Thiele moduli is pointed out. LWRODUCTION An important factor that influences the performance of trickle-bed reactors is the partial wetting of the outer surface of the catalyst particles. This partial wetting of the catalyst bed, termed here as the wetting efficiency f which is defined as the fraction of the particle external surface covered by liquid, has been discussed in several recent reviews [4,6,11].
Incomplete wetting of the catalyst bed in the gascontinuous flow regime has been reported in a number of studies. These studies have been conducted in both reactive systems [5,8,10,13] and non-reactive systems [3,12].
In the latter it was also reported that the catalyst pores were nearly completely filled with liquid.
Quantitative measurements of the wetting efficiency f as a function of the liquid flow rate provided contradictory results [3,5,8,12].
The former three found that f increased with increasing liquid flow rate while the gas flow rate had no effect. In contrast, Schwartz et a1. [12] reported a constant value of f (about 0.68) independent of liquid flow rate.
The incomplete wetting of the catalyst particle leads to non-uniform concentration of reactants and products on the outer surface of the particle. As a result, the concentration profiles inside the pores may be nonsymmetrical.
This would indicate that the overall effectiveness factor v0 in partially wetted catalysts