Leaching numericals

Leaching numericals 1. Vegetable oil seeds containing 120 gm insoluble insoluble solid and 12 gm oil are contacted with 250 gm of organic solvent in a single stage leaching operation. The solvent used is fresh. Determine amount of oil left in the oil seeds after leaching. The equilibrium data can be expressed as N=-4y + 8, where N is gm insoluble/(gm solvent + gm oil), y is gm oil/(gm solvent + gm oil) in the seed phase and x is gm oil/(gm solvent + gm oil) in the solvent phase. The tie line data is y x

0.26 0.02

0. 2 8 0 .0 4

0.31 0.06

0.34 0.08

2. Oil is to be extracted extracted from meal by means means of benzene using continuous continuous counter  counter  current extractor. The unit is to treat 1000 kg of meal (based on completely exhausted solid) per hour. The untreated meal contains 350 kg of oil and 30 kg of  benzene. The fresh solvent is to contain 50 kg of unextracted oil. Experiments carried out under conditions identical with those of the projected battery, show that the solution retained depends on the concentration of the solution as follows `conc. Kg 0

0.1

0. 2

0.3

0.4

0. 5

0.6

0 .7

0.505

0.515

0.530

0.550

0.571

0.595

0.620

oil/kg solution Solution

0.5

retained kg/kg solid 3. 300 kg per hour of halibut liver is to be extracted in a counter current cascade with ether to recover oil. The ether which has been partially purified contains 3% oil. The fresh liver contains 15 % oil and is to be extracted to composition 0.8% oil (on solvent free basis). 200 kg of solvent is to be used. 1. What percentage of oil entering with the liver is recovered in the extract? 2. How many equilibrium stages are required?

4. Roasted copper ore containing copper as CuSO4 is to be extracted in a counter  current extractor. The feed charge to be treated per hour comprises of 12 tonnes of  gangue, 1.5 tonnes of copper sulphate and 0.5 tonne of water. The strong solution produced is to consist of 90% water and 10% copper sulphate by weight. The recovery of copper sulphate is to be 95% of that of the ore. Pure water is to be used as the fresh solvent. After each stage one tonne of inert gangue retains 2 tonnes of water plus the copper sulphate dissolved in that water. Equilibrium is attained in each stage. How many stages are required. 5. 50 tons per day of oil sand (25 mass % oil and 75 mass % sand) is to be extracted with 50 tons per day of naphtha in a continuous counter current extraction battery. The final extract from the battery contains 40 mass % oil and 60 mass % naphtha and the underflow from each unit is expected to consist of 35 mass % solutions and 65 mass % sand. If the overall efficiency of the battery is 60%, how many stages will be required? 6. 2000 kg of waxed paper per day are to be dewaxed in a continuous counter  current extraction system which contains a number of ideal stages by using kerosene as the solvent. The waxed paper contains, by weight 25% paraffin wax and 75 % paper pulp. The extracted pulp is put through a dryer to evaporate the kerosene. The pulp, which retains the unextracted wax after evaporation, must not contain over 0.2 kg of wax per 100 kg of wax free pulp. The kerosene used for  extraction contains 0.05 kg of wax per 100 kg of wax free kerosene. Experiments show that the pulp retains 2 kg of kerosene per kg of kerosene and wax free pulp as it is transferred from cell to cell. The extract from the battery is to contain 5 kg of wax per 100 kg of wax free kerosene. How many stages are required? 7. It is desired to extract the oil from halibut livers by continuous counter current extraction with ethyl acetate. The quantity of solution retained by the granulated livers is given as

`conc.

Kg 0

0.1

0.2

0.3

0.4

0.5

0.6

0.65

0.7

0.72

0.242

0.28

0.339

0.405

0.489

0.60

0.67

0.76

0.81

2

5

oil/kg solution Solution

0.20

retained kg 5

6

solution /kg oil free liver  The liver contains 0.257 mass fraction oil. If 95 % of the oil is to be extracted and the strong solution obtained from the system is to contain 0.7 mass fraction oil,determine a. The quantity and composition of discharged solids b. Kg of oil free ether required per 1000 kg charge of fresh livers c. The number of ideal stages required.