Exam 2016, questions PDF

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Past exam paper for Chemical Engineering, Reaction Engineering (CHEN3010) 2016...

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End of Semester 1, 2016

EXAMINATION PAPER CHECKLIST for examination CHEN3010 Reaction Engineering This page is to remain part of your examination file and is to be submitted with your Examination Cover Sheet and content. This page is for information only and will not be printed.

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Questions for the examination commence on page 3 (following the Examination Paper Checklist and Examination Cover Sheet) – Questions page should state page 1 of X.

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Ensure type of examination is correct ‘CLOSED, OPEN OR RESTRICTED’ o o o

CLOSED - no text books or written materials permitted OPEN - any text books or written materials permitted RESTRICTED - specified text book or written material only permitted

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All pages, sections and questions are numbered sequentially i.e. pages, Part A, B, C, … etc. Questions 1, 2, 3, … Subsections to question numbering is to be consistent throughout the examination paper i.e. (a), (b), (c), …

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General instructions to students are to be entered in the ‘Instructions to Students’ area of the online exam request and is reflected on the Exam Cover Sheet

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If there is insufficient space to enter all the general instructions to students in the ‘Instructions to Students’ section of the Exam Cover Sheet, the top section of page 2 may be used, preceding the commencement of the examination questions

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Instructions regarding the answering of questions are communicated clearly to students. e.g. Answer Part A in the answer book provided and Part B on the examination paper

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All questions, including subsections and parts of questions are to have marks allocated clearly. The total of all marks is to agree with the Total marks on the Exam Cover Sheet

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‘END OF EXAMINATION PAPER’ is to be stated on the last page of the examination paper

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Student Name and ID is only required if the student answers on the examination paper or if the School wishes the paper to be returned

The examination paper has been proof read, the above checks completed, and approved for submission.

EXAMINER

NAME OR ELECTRONIC SIGNATURE Dr GIA HUNG PHAM

DATE 30 March 2016

CO-EXAMINER

Dr KHALIQ AHMED

30 March 2016

HEAD OF SCHOOL/DEPARTMENT (OR DELEGATE)

Venue

End of Semester 1, 2016 CHEN3010 Reaction Engineering

____________________

Student Number

|__|__|__|__|__|__|__|__|

Family Name

_____________________

First Name

_____________________

Department of Chemical Engineering EXAMINATION End of Semester 1, 2016

CHEN3010 Reaction Engineering This paper is for Bentley Campus and Bentley Campus (External) students

This is a CLOSED BOOK examination Examination paper IS NOT to be released to student

Examination Duration

2 hours

Reading Time

10 minutes

For Examiner Use Only

Students are permitted to write notes during reading time in the margins of the exam paper

*Mark12345678910111213

Total Marks

Total

100

Supplied by the University 1 x 16 page answer book Formula sheet (attached to exam paper) Graph paper 2mm

Supplied by the Student Graph paper 2mm (2 pages) A Non-programmable calculator is permitted in this exam

Instructions to Students Answer all six questions (totally 100 marks) Please do not detach any pages from the examination paper. This paper must be returned intact within your answer book. All answers must be written in the answer book supplied and no writings on the examination paper will marked. Some possibly useful formulas are given on pages 4 to 7 Examination Cover Sheet

1415161718

________

End of Semester 1, 2016 CHEN3010 Reaction Engineering You MUST write your Name and Student ID Number on all the graph paper used and you must return all graph paper, whether used or not, inside your answer book.

Examination Cover Sheet

End of Semester 1, 2016 CHEN3010 Reaction Engineering

Question 1 (14 Marks) The gas phase reaction A  2S is carried out in a tubular reactor operated isothermally. The reaction rate is first order with respect to A and has a rate constant of 15 s-1 at 600K. A feed containing 80% (molar basis) of A and the diluent N2 as the balance, is fed to the reactor at 600K and 2 bar, at the rate of 700 moles s-1. [Value of the Gas Constant R = 8.31441 J mol-1 K-1] (1) Neglecting the pressure drop through the reactor, calculate the volume of the reactor and space time, required for a conversion of 90%. (2) Calculate the change in volumetric flow rate from inlet to outlet, as a result of the reaction. Question 2 (21 Marks) [Graph paper supplied] The reaction A  4R is run at 5.2 atm. and 137°C in a plug flow reactor of 10L volume and uses a feed consisting of partially converted product from 15 litres/h of pure unreacted A. The results are as follows: Run No CA(in), mol/h 1 0.1 2 0.08 3 0.06 4 0.04 Find a rate equation to represent this reaction.

CA(out), mol/h 0.084 0.07 0.055 0.038

[Value of the Gas Constant R = 0.082058 L atm mol-1 K-1] Question 3 (15 Marks) Consider the unimolecular series reactions A  R  S being carried out in a batch reactor. The rate expressions and reaction parameters are as follows: rA = -k1CA rR = k1CA – k2CR rS = k2CR k1 = 30 exp(-20,000/RT) and k2 = 1.9 exp(-15,000/RT), with units of min-1 [Value of the Gas Constant R = 8.31441 J mol-1 K-1] It is desired to produce R from A in a batch reactor at a temperature somewhere between 5 and 90°C. Considering the activation energies of the two rate constants at what temperature

Page 1 of 7

End of Semester 1, 2016 CHEN3010 Reaction Engineering

would you run this reaction? Determine the run time which will give the maximum concentration of R. What is the corresponding fractional conversion of A to R? Given:

Question 4 (10 Marks) An isothermal differential reactor is used to study reaction rate law of the following heterogeneous catalytic reaction Solid Catalyst

A



P

Use the sequence of individual steps to show the overall process by which heterogeneous catalytic reaction proceed. Question 5 (20 Marks) The irreversible gas-phase reaction A → P is carried out in a Tubular Fixed Bed reactor, which is filled with spherical catalyst. We assume that the chemical reaction is very fast so that the overall reaction rate is controlled by external mass transfer. Calculate the conversion XA at the reactor outlet. Additional information: -

Catalyst bed length L=2m

-

Catalyst bed diameter dr=6 cm

-

Bed porosity φ = 0.5

-

Catalyst sphere diameter dp = 3 mm

-

Feed flow rate F=8.48 L/s

-

Sherwood number Sh = 60

Diffusion coefficient DAB = 10-7 m2/s Page 2 of 7

End of Semester 1, 2016 CHEN3010 Reaction Engineering

Question 6 (20 Marks) A number of experiments were carried out at very high feed flow rate and small catalyst particle. The partial pressure of the reactant A at the reactor inlet and outlet were , measured. The calculated initial reaction rate ro for each experiment and the partial pressure of the reactant A at the reactor inlet are given in the following table Experiment PA [atm] at reactor inlet 1 2 3 4 5 6 7 8 9 10 11 12 13 14

0.125 0.25 0.50 0.75 1 2 3 4 5 6 7 8 9 10

,

- ro [mol/gcat.s] .10^10 10 20 40 60 78 110 130 147 160 165 169 170 170 170

Assume that the studied reaction has the following reaction mechanism and the second step is the rate limiting step. A  S



A.S



B.S

B.S



B

A.S (S is active centre on catalyst surface)

 S

a. Derive the rate law for the studied reaction. (15 marks) b. Are the assumptions supported by the experimental data? Justify your answer. (5 marks).

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End of Semester 1, 2016 CHEN3010 Reaction Engineering

END OF EXAMINATION Some possibly useful equations:

1  x  2 dx  1  x 2 0 x

2 1    ln1  x  

2

2  1   x x

1 x

dN A  rAV dt X dX t  NA 0  0  rAV FA  FA 0  FA 0 X F A0 X   rA  exit dF rA  A dV

V

F A0

V

dFA

 r

FA

A

X

dX V  FA0   rA 0 rA r r r  B  C  D a b c d kB KC  k B 

K C T  K C T 0 e

H Rx  1 1     R  T0 T 

kT   Ae  E / RT b c d A B  C D a a a c d b       1 a a a  Nj Cj  C A0   j  j X  V NT NT 0  N A0 X T P0 V V0 1   X  T0 P

Page 4 of 7

End of Semester 1, 2016 CHEN3010 Reaction Engineering

F j FA 0   j   j X 

FT FT 0  FA 0 X

  y A0  v v 0 1  X 

P0 T P T0

Fj  j   j X P T0 C A 0 v 1  X P0 T P T0 I CI  CA 0 1  X  P0 T Cj 

C j  CT 0



F j T0 P FT T P0

V v0

 rA0 V FA0 Da1 X 1 Da1 Da 

X 1 

1

1  Da1

n

1

1

 1 k n

1  2 Da2  1  4 Da 2 X 2 Da2 Da2 X 1  Da 2 Da2  2  1    ln 1 X   

2

2 1   X  X

1 X

 CA 0   1  e 1 k    t S  4.6  1 k  dC A  ln   ln k A   ln C A  dt  t   1k  

CA 

xn

dy yn  y1  dx dx x1

 dCA   3 CA 0  4 CA1  CA 2    2t  dt  t0 1  dCA  CA( i 1)  CA i  1     dt  ti 2 t





1  dCA  C A N  2  4C A  N  1 3C A  N      dt  tN 2 t





Page 5 of 7

End of Semester 1, 2016 CHEN3010 Reaction Engineering 2 N r  r  s   im ic N  K i 1 N  K 1   n 1  1 k   1C A0 1

2

2  t1 / n





kcat  Et  S   S   KM 1 K 1   M Vmax Vmax S  1 S   KM  Vmax Vmax

 rS  1  rS S  rS

 r S Vmax  K M

 rS S 

Q  W S  FA 0  i CPi Ti 0  T 





 F A0 X H 0Rx T R   C P T  T R   0 0 X C PTR   i C PiTi 0  X H Rx TR  T XCP   i CPi





dT Ua Ta  T   rA   H Rx   dV FA0   iC Pi  C P X  dT a dV



Ua T  Ta   c CPc m

dTa UaT  Ta   dV m cC Pc UA Ta  T  / FA0    i C Pi  Ti0  T  X EB  H Rx0  TR   CP  T  TR  CA S  Rate 

K A PAC t 1 K A PA

 kinetic factor driving - force group adsorption group

dP G  1    dz g c D p   3

  150 1     1.75 G   Dp   

 1  dP G   dz 0 gc D p   3

 P TF   150 1      1.75G  0 T Dp    PT0 FT 0

dP P TF  0 0 T dz PT0 FT 0

0 

G  1    0 g c D p   3

   1501      1.75G    Dp   

dP  T P0 1   X   dW 2 T 0 P / P0



2 0 Ac  c 1   P0 Page 6 of 7

End of Semester 1, 2016 CHEN3010 Reaction Engineering

ln

k a 1  c c L U 1 X

ac 

6(1   ) dp

P  2 0z   1  P0  P0 

1/ 2

x

A2 W dX  A FA 0 xA 1  rA

 rA  a t k T  f  CA , CB , ........  da  p a t  k d T h C A , C B , ... rd  dt 1 1 a p  p np 1  CC A t 1



a e   1CC 1 a 1  2 CC C C At n

0.5  n  1

 E A  nE A E d  1 1    R  T T0 

  

1 e t k d0 1  n  E d E A  W t Us

ln

1 1 X



k ln 1  k d t  kd

X kC2 U  A0 s F A 0k d 1 X Da2 

kd W   1  e U s  

   

kC A20 W F A0

Da2 1  e      Da2 1  e    dT s ha~ T  T   P s If T Ts dW U sC p s dT dT s Ua~W T a  T   r A  H Rx  If T Ts   dW dW U sC Ps   Fi C pi X

X

0

1 a (t )  1k d t

J Az  DAB kc 

dCA k c C Ab  C As  dz

D AB 

Sh 

kc dp D AB

t

dX dt k   1 X kd t 0

1 

U dp Re   Page 7 of 7

End of Semester 1, 2016 CHEN3010 Reaction Engineering

Sc 

 DAB

Page 8 of 7...