Funnel shaped nozzle as ejectors

Suspension is connected with the presence of a dispersed solid phase, which is suspended ( whirled up ) in the liquid. The material system solid/liquid (S/L) is thus involved. Occasionally a gas is distributed and dispersed in the liquid at the same time, whereupon the material system concerned is a solid/liquid/gas (S/L/G) system. 

This stirring operation is exceedingly frequent according to a well known German stirrer manufacturer it was in the period 1976-80, at 65%, the most frequent of all stirring operations, closely followed by the stirring operation homogenization [277]. 

For solids to be dissolved rapidly in liquids, their total surface must be accessible to the liquid, i.e. the solid particles must be completely suspended in the liquid. In this case that critical stirrer speed is of primary interest, at which this state is just attained, and the other stirring conditions (stirrer type and instalation), which ensure the maintenance of these flow conditions with the lowest stirrer power. 

In crystallization or in solid catalyzed reactions it is, on the other hand, generally necessary, that the dispersed phase is largely uniformly distributed over the whole liquid height. This condition naturally requires both a higher stirrer speed and power and occasionally also another stirrer type than suspension alone. 

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