A two-unit separation is used to dewater ethanol. First, a 110 mol/hr feed of a mixture of 0.750 mole fraction ethanol (E) and the balance water (W) is distilled. The extractive agent, benzene (B), is added to the distillation column in a mixture of 0.940 mole fraction benzene (0.060 mole fraction water). This mixture consists of fresh benzene and the recycle stream of benzene and water recovered from the separator. The company wishes to produce 0.995 mole fraction ethanol (0.005 mole fraction benzene) product stream from the overhead of the distillation column. The bottoms product, containing just benzene and water, is sent to the separator. The composition of the benzene/water mixture leaving the bottom of the separator is 0.85 mole fraction benzene and the balance water. Some of the bottom stream leaving the separator is recycled and added to the fresh benzene feed to the column and the rest of the bottom stream (121 mol/hr) is sent to another unit (not included in this analysis). The stream leaving the top of the separator is pure water.
(a) Draw and label a process flow diagram for this process. Number each stream. Clearly label the components (E, W, B) in each stream.
(b) Calculate the flow rate (mol/hr) of all unknown streams entering and exiting the system.
(c) Calculate the flow rate (mol/hr) and mole fractions of the stream exiting the bottom of the distillation column.
(d) The stream leaving the top of the separator is an ideal gas at 22 psig and 190 degree C. Calculate the volumetric flow rate (cm³/s) of this stream.