Dissolution of Granular Solids in an Agitated Vessel

Illustration 5.6 Dissolution of Granular Solids in an Agitated Vessel 

The assumption made at the outset is that the concentration at the surface of the particles equals the saturation concentration Q of the solid material and that the mass transfer is driven by the linear potential (Q - C), where C is the prevailing concentration in the liquid at any particular instant. 

An initial unsteady mass balance over the solid phase leads to the following expression 

Note that both the surface area and concentration in the liquid C vary with time or indirectly with the remaining mass m. For the area, which can be quite irregular, we stipulate that it varies with the two-thirds power of volume, so that 

To obtain an expression for the external concentration C, we apply a simple cumulative mass balance, which reads 

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