Amixture of iso-propanol (more volatile, i-proh) and n-propanol has an approximately constant relative volatility of 1.8. 100 kmol/h of a saturated liquid feed containing 40 mol% i-proh is available. the distillate is to contain 90% i-proh, and the bottoms product 10% i-proh. a. if the reflux ratio is 4, how many ideal stages are required for this separation? do stage-by-stage calculations by hand or the mccabe-thiele method. b. what is the minimum reflux ratio possible? c. what is the minimum number of stages needed for this separation? d. compare the results for parts (a) to (c) to what is obtained using the fug method.

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?