42. For this problem, the feed is 60 mol% dimethyl ether (DME) and 40 mol% methanol. Assume that the equilibrium data provided are correct. 1. A feed of 200 kmol/h is flashed at 5 bar and 50°C. What are the liquid and vapor flowrates and the mole fractions in the vapor and liquid exit streams? A feed of 200 kmol/h is to be fractionated to give a distillate containing 98 mol% dimethyl ether and a bottoms product containing 98 mol% methanol. The feed is 20% vapor and 80% liquid. There is a total condenser and a partial reboiler. 2. Determine the molar flowrates of the distillate and bottoms. 3. Calculate all internal flows for operation at a reflux ratio of 0.1. 4. In order to use cooling water in the condenser, assume that the DME must condense no lower than 55°C. Estimate the top pressure for this column. 5. In order to use low-pressure steam in the reboiler, the bottom temperature must be no higher than 148°C. Estimate the bottom pressure for this column.
Added by Martin M.
Close
Step 1
### Part 1: Flash Distillation ** Show more…
Show all steps
Your feedback will help us improve your experience
Penny Riley and 78 other Chemistry 101 educators are ready to help you.
Ask a new question
Labs
Want to see this concept in action?
Explore this concept interactively to see how it behaves as you change inputs.
Key Concepts
Recommended Videos
Adi S.
The feed to a distillation column (sketched below) is a 45.0 mole\% $n$ -pentane- 55.0 mole\% n-hexane liquid mixture. The vapor stream leaving the top of the column, which contains 98.0 mole\% pentane and the balance hexane, goes to a total condenser (which means all the vapor is condensed). Half of the liquid condensate is returned to the top of the column as reflux and the rest is withdrawn as overhead product (distillate) at a rate of $85.0 \mathrm{kmol} / \mathrm{h}$. The distillate contains $95.0 \%$ of the pentane fed to the column. The liquid stream leaving the bottom of the column goes to a reboiler. Part of the stream is vaporized; the vapor is returned to the bottom of the column as boilup, and the residual liquid is withdrawn as bottoms product.(a) Calculate the molar flow rate of the feed stream and the molar flow rate and composition of the bottoms product stream. (b) Estimate the temperature of the vapor entering the condenser, assuming that it is saturated (at its dew point) at an absolute pressure of 1 atm and that Raoult's law applies to both pentane and hexane. Then estimate the volumetric flow rates of the vapor stream leaving the column and of the liquid distillate product. State any assumptions you make. (c) Estimate the temperature of the reboiler and the composition of the vapor boilup, again assuming operation at 1 atm.(d) Calculate the minimum diameter of the pipe connecting the column and the condenser if the maximum allowable vapor velocity in the pipe is $10 \mathrm{m} / \mathrm{s}$. Then list all the assumptions underlying the calculation of that number.
Q.1 A total feed of 100 kmol/h having a composition of 50 mol % n-pentane and 50 mol % n-heptane is to be fractionated at 101.3 kPa total pressure to give a distillate containing 90 mol % n-pentane and bottoms containing 10 mol % n-pentane. Equilibrium data are given below at 101.3 kPa as mole fractions of n-pentane. If the feed enters as: (i) Liquid at 45°C. (ii) Saturated liquid at the bubble point. (iii) Mixture of 50% liquid and 50% vapor at 70°C. (iv) Saturated vapor at the dew point. (v) Vapor at 90°C. In each case use the graphical methods of McCabe-Thiele to calculate: (a) The amount of distillate and bottoms in kmol/h. (b) The minimum number of theoretical plates. (c) The minimum reflux ratio. (d) If the actual reflux ratio R = 1.35 × Rmin, determine the number of theoretical plates. (e) Determine the feed tray number. (f) Determine the boilup ratio. x | 1.000 | 0.867 | 0.594 | 0.398 | 0.254 | 0.145 | 0.059 | 0.000 y | 1.000 | 0.984 | 0.925 | 0.836 | 0.701 | 0.521 | 0.271 | 0.000 In your solution, use only HAND calculations and drawings.
Recommended Textbooks
Chemistry: Structure and Properties
Chemistry The Central Science
Chemistry
Watch the video solution with this free unlock.
EMAIL
PASSWORD