Example L$3.$

A $5,000kg$ of soya bean with a composition of $40wt\%$ oil and the remaining is the ash; is extracted in multistage continuous counter current extraction column using hot water as a solvent. The produced extract must contain $35wt\%$ oil and the total extraction efficiency has to be $85\%.$ It is given that $1kg$ inert material $($ash$)$ retains $2\mathrm{.}5kg$ solution and this value is constant ratio for underflow stream.

Compute underflow product stream composition.

Compute necessary amount of the solvent $($water$)$ needed