Influence of the Liquid Injection Rate

The separation efficiency is determined by the difference in gas concentration between the inlet and outlet of the fluidized bed. A dimensionless quantity defined by Hill [40] - the so-called absorption factor - can be used in reaction technology at a constant volume flow rate if mole fluxes are replaced by concentrations 

In the diagrams (Figs. 16.7 and 16.8), there are two normalized quantities, the normalized liquid mass flow 

A physical explanation of the process where the injection rate is changed can be described with help from the mass balance of the liquid within the fluidized bed. For simplicity, the suspension is regarded as a pure liquid. The particle movement follows the model of the ideal mixing, and the liquid on the particles is a thin film of constant thickness. Under these stationary conditions, the degree of wetting can be formulated from the moisture balance around the entire apparatus 

It is clear from the equation that an increase in the liquid injection rate results in a larger degree of wetting. If this surface becomes larger, the gas temperature will decrease above the bed as a result of the increasing evaporation (Fig. 16.7). 

The absorption process in the bed is affected, as with all mass transfer processes, by the surface. If no other factors have any strong limiting effect on the process, an increase in mass transfer surface leads to a reduced sulfur dioxide concentration (Fig. 16.8). 

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