Water is used to dissolve 1200 kg/h of NaCO3 from 3300 kg/h of a solid, where the balance is an insoluble oxide. If 3600 kg/h of water is used as the solvent and the total underflow from each stage is 30 wt% solvent on a solute -free basis.

a) Compute the minimum solvent feed rate.

b) What is the ratio of actual solvent rate to the minimum solvent rate?

c) Determine the percent recovery of soluble solids with a cascade of three countercurrent equilibrium stages if the solvent flow rate is 2 times the minimum valve.