LeachingLeachingLeachingLeaching Problem Solving DrillProblem Solving DrillProblem Solving DrillProblem Solving Drill

1. A slurry of flaked soybeans weighing a total of 100 kg contains 75 kg of inert solids and 25 kg of

solution with 10 wt % oil and 90 wt % solvent hexane. This slurry is contacted with 100 kg of pure

hexane in a single stage so that the value of N for the outlet underflow is 1.5 kg insoluble solid/kg

solution retained. Calculate the amounts and compositions of the overflow V1 and the underflow

L1, leaving the stage.

2. A treated ore containing inert solid gangue and copper sulfate is to be leached in a countercurrent

multistage extractor using pure water to leach the CuSO4. The solid charge rate per hour

consists of 10 000 kg of inert gangue (B), 1200 kg of CuSO4 (solute A), and 400 kg of water

(C). The exit wash solution is to contain 92 wt % water and 8 wt % CuSO4. A total of 95% of the

CuSO4 in the inlet ore is to be recovered. The underflow is constant at N = 0.5 kg inert gangue

solid/kg aqueous solution. Calculate the number of stages required.

Ans. 9 stages, LAns. 9 stages, LAns. 9 stages, LAns. 9 stages, LNNNN = = = = 20000kg/h, Y20000kg/h, Y20000kg/h, Y20000kg/h, YANANANAN = = = = 0.0030, V0.0030, V0.0030, V0.0030, V1111==== 14250kg/h14250kg/h14250kg/h14250kg/h

3. Soybean flakes containing 22 wt% oil are to be leached in a countercurrent multistage process to

contain 0.8 kg oil/100 kg inert solid using fresh and pure hexane solvent. For every 1000 kg

soybeans, 1000 kg hexane is used. Experiments give the following retention of solution with the

solids in the underflow, where N is kg inert solid/kg solution retained and yA is the wt fraction of oil in

solution:

N 1.73 1.52 1.43

yA 0 0.20 0.30

Calculate the exit flows and compositions and the number of theoretical stages needed.

4. It is desired to extract benzoic acid from toluene using water as the extracting solvent.

Data:Data:Data:Data:

Analysis 0f feed: Assumptions:Assumptions:Assumptions:Assumptions:

benzoic acid = l0% 1. All flow rates are steady

toluene = 90% 2: Toluene and water are immiscible

Rate of feed = 120 kg/minute 3. Feed concentration remains constant

Rate of solvent = 20 kg/minute 4. Two streams leaving each stage are in equilibrium

with each other and k =0.125

Calculate the % of the acid extracted with a single stage system and also for two stage

countercurrent extraction system.

5. The distribution coefficient of solute A between solvents B and S is given by Y = 3X where Y

and X are mass ratios of A to solvent in extract and in raffinate, respectively. B and S are

mutually insoluble to each other. One hundred kg of a 30% solution of A and B is to be

successively treated in two batch contacts with 60 kg of solvent each time. Calculate the overall

percent recovery of A .

Study Principles involve in LeachingStudy Principles involve in LeachingStudy Principles involve in LeachingStudy Principles involve in Leaching and Liquidand Liquidand Liquidand Liquid----LLLLiquidiquidiquidiquid ExtractionExtractionExtractionExtraction ....