Indian Institute of Technology Kharagpur (IIT-K) 2007 M.Tech Chemical engineering Chemical reactor analysis - Question Paper

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INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR*^-'

Date 20.02.2006(FN) Time : 2 Hrs Full Marks : 30

Spring, 2007 III-yr.B.Tech.(Hons)/I-yr.M.Tech

Subject No : CH62016 Subject Name : Chemical Reactor Analysis

No. of Students :46 Department: Chemical Engineering

Instructions : Attempt all questions. Assume the missing parameters.

Part-A

Q1 . The vapor-phase reaction A + B C + D is earned out in a packed-bed reactor. The feed consists of 30%A, 45% B and30% of inerts at 50 atm and 600 C. The rate equation is proposed as

kP_AP_B

^rA~ \+k_ap_a+k_cp_c

(a) Derive the above rate equation assuming a suitable mechanism.

(b) Derive an expression for dX/dW in presence of pressure variation in the catalyst bed. How the pressure varies as a function W? [5+5]

Q2. A liquid-phase isomerization reaction n-butane (A) iso-butane(R) is to be carried out adiabatically in a plug flow reactor. The rate equation is given as follows:

-r_A = ki (C_A - Cr/Kc) kmol/m³.hr

The feed consisting of 90 mol% of n-butane and 10mole% of inerts (I) enters the reactor at 330K and at the rate of 100 kmol/hr. Using the following data design a PFR (Volume only) to achieve 65% conversion of A. Show all steps of the calculation.

[8]

Data:

79061 2.778xlO~^J'-

1 = 31.1 exp

830.31 3.003x10---

K_c =3.03 exp

Cao - 9 kmol/m AH_r- -7000 J/mol. of A

Average Cp values (independent of temperature):

c

p.R

'P-A

135 J/mol.K

C_p,i = 150 J/mol.K

Part B

Q .Describe the influence of pore size of a catalyst on diffusivity of gas phase molecules

(3)

Q4- Wh^at is Thiele Modulus (<f>) and write down its physical significance. (2)

Q 5. a) List the critical assumptions made in the BET method for evaluation of surface area.

(2)

b) From the BET plot provided in the figure I, estimate the surface area per gram of the silica gel by using the adsorption data for Nitrogen at -183 C. The density of liquid nitrogen at this temperature is 0.751 gm/cc.

The area covered by one adsorbed molecule is equal to 1.07 [M/(No .p)]²*³ (5)

'C.

I