Maldistribution, packings, liquid wall flow

The flow pattern of fluids in gas-liquid-solid (catalyst) reactors is often far from ideal. Special care must be taken to avoid by-passing of the catalyst particles near the reactor walls, where the packing density of the catalyst pellets is lower than in the centre of the bed. By-passing becomes negligible if the ratio of reactor to particles diameter is larger than 10 a ratio of 20 is recommended. Flow maldistributions might be serious in the case of shallow beds. Special devices must be used to equalize the velocity over the cross-section of the reactor before reactants are introduced onto the catalyst bed. 

With random packing, the degree of maldistribution u [2.2] of the liquid across the column cross section is influential due to wall effects on flow, channeling, etc., u varies in the limits... 

The smaller the reflux ratio, the more the separation effect decreases with maldistribution. To restrict maldistribution of the liquid by channeling or flow at the wall, the total height of the packing Z is separated into single packing heights Z. each with its own support and cover grids, and liquid distributor [2.118]. 

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