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This Chemical Engineering (Separations) assignment

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This Chemical Engineering (Separations) assignment.
 

A 100 mole/min feed stream comprising 55 mole percent benzene and 45 mole percent toluene is separated by continuous distillation at atmospheric pressure in a column fitted with a total condenser. Process specifications require a mole fraction of 0.9999 benzene in the distillate and 0.02 in the bottoms. The feed enters as a saturated liquid. The reflux ratio Ro = 1.5. Use the analytical procedure

(Kremser equation) for x > 0.9 and the graphical (McCabe-Thiele method)

for x < 0.9. Note that one point on the equilibrium curve is (x,y) =

(0.9000000, 0.9587266).

 

po B.

In | 1 niin a A TOO

With the following pearatmeter Vealttes,

Colh rotted f f. C"

vn Ee i

beetazectne 15.9008 | 2788.5] 2M

toliene LOOLST | 3006 52 | -35.67

eth Thensene LH OLN PBT Ae PF Hoo,

nopropvlbenszene | 16 D062 | 3453 84 > —60.01

ebatvlbensene | LO0793 | 36385 0, —71 77

Note that) 2oas ia Woasid A? as doit Hyg Mote dita ate paver: thea vou

need (pist as oa real life. tare datu are avarlable ai the dibtars and om the

faterqiet thr ven eee |

a. How many stages are required?

b.

c. What is the optimal stage to introduce the feed?

 

8. (Lecture 09) (40 points) A200 mole/hr feed of 55 mole percent n-pentane and 45 mole percent

n-heptane enters a continuous distillation tower operating at a reflux ratio Ro= 0.35

The column is fitted with a total condenser. The mole fraction, xp, of n-pentane in the

distillate is 0.98 and in the bottom product the mole fraction of n-pentane, xz, is 0.09. Feed

enters as a Saturated liquid.

a) How many plates will be required, assuming ideal stages?

b) What plate is optimum for the feed to enter?

c) Generate expressions for the enthalpies of Liquid mixtures, H,(T, x), and Vapor mixtures,

H\(T,y) of n-pentane and n-heptane.

d) Calculate the required rate of heat removal from the condenser, q,, and required rate of heating at the reboiler, q-.

e) Calculate the required flow rates of cooling water to the condenser and steam to the reboiler.

 

AH‘*? at normal boiling point | 26.40 31.77

in kJ/mol

Define reference states such that the liquid enthalpy is zero for each pure component at 309.2

K.

e Vapor pressure data for the components can be obtained from the Antoine’s equation

MATLAB code in the Computer Code tab on the course website.

e Heat capacity of Water 1 BTU/(Ib °F). Allow for a 10 C temperature rise in the cooling water.

e Steam: use 150 psig steam, which has a temperature of 188 C (461 K) and a latent heat of

evaporation of 1986 kJ/kg

 

9. (Lecture 09) (40 points) A500 kg/min stream with composition 80 mole percent Methanol

(CH30H, “light”), 20 mole percent Ethanol (C2HsOH, “heavy”) is to be distilled at atmospheric

pressure with 95 percent recovery of the light key in the distillate and 90 percent recovery of

the heavy key in the bottom product. The feed will enter as saturated liquid, a total condenser

will be fitted to the column, and a reflux ratio equal to 1.5 times the minimum will be used.

Assume ideal plates. The column will operate at 50 percent of the flooding velocity based on

conditions at the top of the tower, the plate spacing will be 24 inches and the plates have

bubbling area equal to 85 percent of the total area.

 

Given these specifications,

 

a. How tall should the column be according to the McCabe-Thiele method; and

 

b. What should the tower diameter be?

MW CH30H = 32.04 MW C,HSOH = 46.07

Note for part a: Why not calculate the number of plates and then multiply by the plate spacing?

Notes for part b: You may neglect the surface tension correction factor in equation 21.68. Also,

since the distillate is nearly pure CH30OH, you can use the density of pure CH3OH as a reasonable

approximation for p, at the top of the tower (750.7 kg/m? at 64.8 C). Pure CH30H may also be

used as a reasonable approximation for calculating py