40 kg s^-1 of heptane is to be used to extract sunflower oil from sunflower seed

Question

40 kg s^-1 of heptane is to be used to extract sunflower oil from sunflower seeds in a counter-current process which uses a centrifuge to separate extract and raffinate. 100 kg s^-1 of sunflower seeds which 40% oil are to be extracted until the final raffinate contains less than 2% by mass of oil. The ratio of solution to insoluble solids in the raffinate is 1: 4 by mass and no insoluble solids are present in the extract. There is sufficient solvent to ensure all the oil is dissolved. Determine: (a) the composition and amount of the final extract and raffinate (b) the number of stages required. A blank triangular diagram is provided in FIGURE 1.

Explanation / Answer

(a) Mass fraction = Substance mass m/ Total mass

So, mass of solute (raffinate) = 2*40 = 80 g

Similarly, mass of the solvent (oil) = 40*100 = 4 kg

Total amount = 4000+80 = 4080 g

Given that the composition has a ratio 1:4

So, Composition contains 40*100/4080 = 0.9804% of insoluble solid, 100*100/4080 = 2.45098% of raffinate and 96.569% of oil.

(b) Mainly, three stages are involved in this,

Firstly, sunflower seeds are extracted from seeds by the help of counter process using heptane. Then, the extracted oil is separated from raffinate mixed in the oil, and Finally, the oil is purified to remove any present insoluble solids.

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