Question

 4.14. Strawberries contain about 15 wt% solids and 85 wt% water. To make strawberry jam, crushed strawberries and sugar are mixed in a 45:55 mass ratio, and the mixture is heated to evaporate water until the residue contains one-third water by mass.

 (a) Draw and label a flowchart of this process.

 (b) Do the degree-of-freedom analysis and show that the system has zero degrees of freedom (i.e., the number of unknown process variables equals the number of equations relating them). If you have too many unknowns, think about what you might have forgotten to do.

 (c) Calculate how many pounds of strawberries are needed to make a pound of jam.

 (d) Making a pound of jam is something you could accomplish in your own kitchen (or maybe even a dorm room). However, a typical manufacturing line for jam might produce 1500 Ib/h. List technical and economic factors you would have to take into account as you scaled up this process from your kitchen to a commercial operation.

 4.11. 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) Draw a flowchart of the process, labeling the two feed streams (beans and solvent) and the leaving streams (solids and extract).

 (b) The soybeans contain 18.5 wt% oil and the remainder insoluble solids, and the hexane is fed at a rate corresponding to 2.0kg 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.

 (c) 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.

Answer 1