[XBOX999]

2. Sap from maple trees contains 2.1% (on a mass basis) sugar. It needs to be concentrated to 18% sugar prior to a final evaporation. The final evaporation step serves to caramelize the sap and result in a good quality maple syrup containing 67% sugar. Traditional methods can be used to evaporate the water from 2.1 to 18% and then from 18 to 67%. Nowadays, maple syrup producers use a reverse osmosis membrane process to concentrate the sap from 2.1 to 18%. The process is illustrated in the figure below. Use the information given in the figure to determine:
a. The rate of production of concentrated sap (B);
b. The rate of production of rejected water (P);
c. The percentage of water extracted from the sap prior to the final evaporation step;
d. The fraction of the sap leaving the reverse osmosis cell (which acts in essence as a separator) that is recycled;
e. The percentage of water evaporated (based on the sap feed rate) after the reverse osmosis process to obtain the final syrup.

[Gerard]

mass balance:
mass balance in=mass balance out
accumulation=mass in-mass out

Energy balance:
q=S x latent heat of steam= Fhf+Lhl-Vhv= UA(T2-T1)

that will give you the cue, the rest is up to you, read your McCabe, Geankoplis or your Felder book