0 votes
30 views
ago in Chemical engineering by (510 points)
Design a distillation column to separate a mixture of cyclohexane and toluene with a feed composition of 60 mol% cyclohexane and 40 mol% toluene. The distillate product should contain a minimum of 90 mol% cyclohexane and the bottom product should contain a maximum of 10 mol% cyclohexane. You have access to a temperature range of 80-150°C and a pressure range of 1-5 atm. Determine the number of theoretical plates required for this separation and the corresponding ref

1 Answer

0 votes
ago by (730 points)
To design a distillation column for separating a mixture of cyclohexane and toluene, we need to follow these steps:1. Choose the operating pressure: We will choose an operating pressure of 1 atm for this separation since both cyclohexane and toluene have relatively low boiling points, and operating at a lower pressure will reduce the energy required for the separation.2. Obtain the vapor-liquid equilibrium  VLE  data: For the chosen operating pressure, we need to obtain the VLE data for the cyclohexane-toluene system. This data can be found in literature or by using software like Aspen Plus or ChemCAD. For this problem, we will assume that we have the VLE data available.3. Determine the feed quality: The feed quality  q  is the fraction of the feed that is liquid. Since the feed is not specified as liquid or vapor, we will assume it is a saturated liquid, so q = 1.4. Locate the feed, distillate, and bottom compositions on the McCabe-Thiele diagram: Using the VLE data, we can plot the equilibrium curve and locate the feed composition  60 mol% cyclohexane , distillate composition  90 mol% cyclohexane , and bottom composition  10 mol% cyclohexane  on the McCabe-Thiele diagram.5. Determine the minimum reflux ratio  Rmin : Using the McCabe-Thiele diagram, we can find the intersection of the q-line  q = 1  with the equilibrium curve and draw a tangent line from this point to the distillate composition. The slope of this tangent line is the minimum reflux ratio  Rmin .6. Choose an actual reflux ratio  R : To ensure a good separation, we will choose an actual reflux ratio that is 1.2 times the minimum reflux ratio  R = 1.2 * Rmin .7. Calculate the number of theoretical plates  N : Using the chosen reflux ratio, we can now construct the operating line for the rectifying section and the stripping section on the McCabe-Thiele diagram. By stepping off the stages from the distillate composition to the bottom composition, we can determine the number of theoretical plates required for this separation.8. Design the distillation column: Based on the number of theoretical plates, we can design the distillation column with the appropriate number of trays or packing height. The column will also need a reboiler and a condenser to provide the necessary heat input and output for the separation.In summary, by following these steps and using the VLE data for the cyclohexane-toluene system, we can determine the number of theoretical plates required for this separation and the corresponding reflux ratio. The actual design of the distillation column will depend on the specific equipment and operating conditions chosen.

Related questions

Welcome to Sarvan Science Q&A, where you can ask questions and receive answers from other members of the community.
...