In the production of soybean oil, dried and flaked soybeans are brought into contact with a solvent (often hexane) that extracts the oil and leaves behind the residual solids and a small amount of oil.
a. The soybeans contain 18.5 wt% oil and the remainder insoluble solids, and the hexane is fed at a rate corresponding to 2.0 kg hexane per kg beans. The residual solids leaving the extraction unit contain 35.0 wt% hexane, all of the non-oil solids that entered with the beans, and 1.0% of the oil that entered with the beans. For a feed rate of 1000 kg/h of dried flaked soybeans, calculate the mass flow rates of the extract and residual solids, and the composition of the extract.
b. The product soybean oil must now be separated from the extract. Sketch a flowchart with two units, the extraction unit from Parts a and b and the unit separating soybean oil from hexane. Propose a use for the recovered hexane.