Influence of CaS Ratio

Investigations into the calcium/sulfur ratio represent an important aspect of the evaluation of the economy of this procedure. The influence of the stoichiometric relationship for different spraying mass fluxes has been investigated, and the adjusted experimental conditions are listed in Tabs. 16.3 and 16.4. 

The results demonstrate that for liquid mass fluxes, which do not lead into the direct proximity of the state of saturation of air, a stoichiometric relationship does not play an unimportant role. Rather, the mass transfer area of the fluidized bed is the limiting factor of the absorption. Over-stoichiometric operation does not lead to any improved separation of the SO2 (Figs. 16.14 and 16.15), the reason being the permanent destruction of the liquid film by particle-particle collisions and the consequent production of inactive reactants. 

In order to estimate the probability of impact of the moistened part of a particle by surrounded particles in the fluidized bed, a simple model was developed [69], As an assumption that the fluidized bed is in an homogeneous condition, a certain portion of the relative porosity is assigned to each particle, and the shape of air covering the particle is taken to be a cube (Fig. 16.16). The entire bed consists of stacked cubes containing a particle at their center. The amount of air - and in consequence the distance between the particles - becomes larger for example, with the same fluidization mass flow the Archimedes number is decreased. The bed will then expand with a greater fluidization throughput and with a constant Archimedes number hence, the distance between the surrounded particles will increase. 

A probability of impact Pr depends on the path length ap between surrounded particles and the relationship of the total projected surface of the surrounded particles AP,in relation to the surface of the sphere Asv,surrounded with the radius ap. 

The probability for n successful collisions between the particles with the distance ap and k follows with [22]  

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