BIOCHEMICAL REACTION ENGINEERING - II

Code No: R05320804 Set No. 1
III B.Tech II Semester Regular Examinations, Apr/May 2009
BIO CHEMICAL ENGINEERING
(Chemical Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. Discuss in detail about DNA and write down the general chemical structure. [16]
2. What do you mean by enzyme?Name the types of it and in turn define cofactors
and explainits classification. [16]
3. What is Immobilization and describe the different types of Enzyme Immobilization?
[16]
4. (a) Define specific growth rate and give its units. Using this and the dilution rate
write the steady state material balance for call mass.
(b) What is diauxic growth? Explain with a figure.
(c) In a typical growth curve for batch cell cultivation, explain the reasons for
length of lag and suggest ways to reduce lag. [4+4+8]
5. Give a detailed account of carbohydrates with suitable examples. [16]
6. (a) Describe the various configurations of CSTRs used for enzyme-catalyzed reactions.
(b) Derive the general substrate balance equation for the single enzyme catalyzed
reaction S!P taking place in a CSTR. [10+6]
7. (a) What is inoculum? Explain the preparation and transfer of inoculum and the
precautions with all details.
(b) Write a detailed note on various parameters to be controlled and monitored
in industrial fermentation processes. [8+8]
8. Discuss briefly various purification procedures in down stream operations.

Code No: R05320804 Set No. 2
III B.Tech II Semester Regular Examinations, Apr/May 2009
BIO CHEMICAL ENGINEERING
(Chemical Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. Discuss characteristics and functions of Mitochondria, Ribosome, Endoplasmic
reticulum and Plasma membrane. [16]
2. (a) What do you mean by active sites of enzyme?How it is created in enzyme.Write
aboutthe structure ofactive sites.
(b) Name the reactive groups which may be attached to these active sites. [8+8]
3. Write the sequence of chemical reactions in EMP pathway with enzyme name in
respective reactions. What is the basic purpose of glycolysis. [16]
4. (a) Write the Monod equation and what are its limitations.
(b) Aiba et al(1968) reported the results of a chemostat study on the growth of
a specific strain of baker’s yeast as shown in the following table. The inlet
stream
Dilution Steady state glucose concn. Steady state cell concn.
rate D, hr-1 s, g/L x, g/L
0.084 0.054 2.00
0.100 0.079 1.20
0.160 0.138 2.40
0.198 0.186 2.33
0.242 0.226 1.25
of the
chemostat did not contain any cells or products. [4+12]
5. What are carbohydrates? Explain in detail with examples. [16]
6. (a) Obtain the differential form of mass balance equation in an ideal PFTR for
constant axial velocity.
(b) Compare CSTR and PFTR for carrying out enzyme reactions and for microbial
processes. [8+8]
7. Name the microorganism used for citric acid production. What is the basis for
commerical biochemical citric acid process? Briefly explain the citric acid recovery
process with a neat flow diagram. [16]
8. Discuss the following purification methods:
(a) Chromotography
(b) Electrophoresis.
Code No: R05320804 Set No. 3
III B.Tech II Semester Regular Examinations, Apr/May 2009
BIO CHEMICAL ENGINEERING
(Chemical Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. Briefly compare procaryotes and eucaryotes in terms of internal structure and functions.
[16]
2. Write theM.M.equation.How Vmax and Km values are determined by using linweaver-
Burk,Eadie-Hofstee and Hanes plots? [16]
3. How one can accomplish the synthesis of small and macro molecules? Explain with
necessary chemical equations. [16]
4. Suppose you have an organism that obeys the Monod equation where μmax = 0.5
hr-1 and Ks = 2g/L. The organism is being cultivated in a steady state CSTR,
where F = 100 L/hr, s = 508/L and YX/S = 0.5.
(a) What size vessel will give the maximum total rate of cell production?
(b) What are the substrate and cell concentrations of the optimum fermenter in
part(a). [6+10]
5. Discuss in detail about carbohydrates with suitable examples. [16]
6. Write in detail about CSTR cell reactors with recycle and wall growth. [16]
7. (a) Explain the following continuous sterilizer designs with a schematic diagram.
i. Direct heating using steam injection
ii. Indirect heating using plate heat exchangers
(b) Discuss the several advantages of continuous sterilization and also mention its
drawbacks. [5+5+6]
8. (a) Discuss the need for down stream processes in bio chemical and bio technological
industries.
(b) What is centrifugation? Explain its applications in bio chemical industries
with examples.
(c) Discuss the working of any centrifuge with a neat sketch.


Code No: R05320804 Set No. 4
III B.Tech II Semester Regular Examinations, Apr/May 2009
BIO CHEMICAL ENGINEERING
(Chemical Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. Write the classification of Protist Kingdom and explain the morphological and
functional features of different classes of microorganisms? [16]
2. (a) Write about the differences and similarities between enzymes and synthetic
catalysts.
(b) Explain the Enzyme-Substrate Complex formation? [8+8]
3. Compare the imporant characteristics of physical adsorption and covalent bonding.
[16]
4. (a) How can the kinetic parameters of the Monod equation be evaluated?
(b) A chemostat study was performed with yeast. The medium flow rate was
varied and the steady state concentration of cells and glucose in the fermenter
were measured and recorded. The inlet concentration of glucose was set at
100g/L. The volume of the fermenter contents was 500mL. The inlet stream
was sterile.
Flow rate Cell concentration Substrate concentration
F, ml/hr x, g/L s, g/L
31 5.97 0.5
50 5.94 1.0
71 5.88 2.0
91 5.76 4.0
200 0 100
Find the rate equation for cell growth assuming Monod kinetics. [4+12]
5. What are carbohydrates? Explain in detail with examples. [16]
6. Derive a suitable expression for estimating effluent cell mass and substrate concentration
in an ideal PFTR using Monod kinetics. [16]
7. Discuss the method of production penicillin in detail. [16]
8. Describe the various methods available for cell rupture.





BIO CHEMICAL REACTION ENGINEERING
BIO CHEMICAL REACTION ENGINEERING Question Papers (Regular, 2007)
SET : 1
1. 1. Derive the design equation for a batch reactor. Write the advantages and
disadvantages using batch reactors in bioprocessing.
1. 2. Decomposition of acetone dicarboxilic acid is a first order reaction :
Find out the energy of activation for this reaction graphically.
1. 3. What sort of fermentation would not need to be performed in a fed batch manner?
Derive the mathematical expressions for various feeding mechanisms of fed batch
reactor?
4. the below is the 4th question :
5. The following id the 5th Question :
ASSUME THAT the system is in an ideal solution :
f = yA fA, pure substance = yA (fA, pure substance / )
the quantity in brackets is given by the Newton charts, which may be found in most
thermodynamics texts for chemical engineers.
1. 6. Behavior of short laminar flow reactors . Consider laminar flow in a tubular
reactor, which is so short that the dispersion model is not applicable. For this
situation prediction of behavior becomes very difficult, however we can still estimate
the poorest expected performance of such reactors. As an example take a first order
reaction A ---- R with XA, plug = 0.99. recalling for laminar flow that maximum
velocity in the centerline of the pipe is twice the average velocity and that this
represents the smallest residence time in the reactor estimate the lower bound to the
expected conversion.
1. 7. Write about the stability analysis of bioreactors using mathematical model.
1. 8. Describe the mass transfer aspects you need to consider in the design of
bioreactors.
Describe the heat transfer aspects you need to consider in the design of bioreactors.
SET : 2
1. What are the ideal flow conditions in a bioreactor? Explain them in detail.
2. What is meant by a homogenous reaction? What is its importance in fermentation
industry? Explain in detail.
What is Michaelis – Menten equation? Describe its importance in enzymatic processor.
3. What is the difference between the specific growth rate (μ) and the rate of cell
increase (dx/dt)?
Why do we use the specific growth rate to describe cell growth instead of the doubling
time (or generation time)?
4. Reactant A decomposes in an isothermal batch reactor (CAO = 100) to produce wanted
R and unwanted S and the following progressive concentration reading are recorded :
CA (100) 90 80 70 60 50 40 30 20 10 (0)
CR (0) 1 4 9 16 25 35 45 55 64 (71)
Additional runs show that adding R or S does not affect the distribution of products
formed and that only A does. Also it is noted that the number of moles of A,R and S is
constant.
a) Find the versus CA curve for this reaction. With a feed CAO = 100 and CAf = 10,
find CR
b) From a mixed flow reactor
c) From a plug flow reactor
d) Repeat parts (b) and (c) with the modification that CAO = 70
5. For the system with CAO = 5 mol/lit
a) Find the space time in amixed reactor to achive 90% conversion of A to R
b) With a sketch show the location and determine the necessary heat exchanger if feed
enters at 25 C, product leaves at 25 C, and the allowable temperature range is from 5
C to 95 C.
6. Describe how do you estimate the conversion in a bioreactor with nonideal flow
behaviour using dispersion model.
7. Explain in detail the packed bed bioreactor dynamics using mathematical model?
8. Describe some characteristic features of a fermenter which are neede to be
considered while designing a fermenter.
What are the advantages and disadvantages of using off – centre impellers over baffles
for creating turbellence? Explain in detail.
SET : 3
1. Derive the design equations for the following using mathematical models for :
a) CSTR
b) PFR.
2. Explain how do you calculate the first order reaction rate constant using various
methods.
3. What is diauxie growth curve?
Why do cell numbers increase exponentially during the log phase in batch cultutre?
4. The desired liquid phase reaction :
A + B --------------- R + T , dCR/dt = dCT/dt = k1CA1.5CB0.30
Is accompanied by the undesired side reaction
A + B --------------- S + U , dCS/dt = dCU/dt = k2CA0.50CB1.8
What contacting schemes (reactor types) would you use to carry above reactions to
minimize the concentration of the undesired products?
5. Determine the equilibrium conversion for the following elementary reaction between
0 C and 100 C.
6. The kinetics of a homogeneous liquid reaction are studied in a flow reactor, and to
approximate plug flow the 48 cm long reactor is packed with 5mm nonporous pellets. If
the conversion is 99% for a mean residence time of 1 sec calculate the rate constant
for the first order reaction
a) Assuming that the liquid passes in plug flow through the reactor,
b) Accounting for the deviation of the actual flow from plug flow.
c) What is the error in calculated K if deviation from plug flow is not considered.
Data : Bed voidage = 0.4,
Particles Reynolds number = 200
7. Explain in detail the response of the nutristat operation?
8. Describe some characteristic features of a fermenter which are neede to be
considered while designing a fermenter.
What are the advantages and disadvantages of using off – centre impellers over baffles
for creating turbulence? Explain in detail.
SET : 4
1. A gas mixture consisting of 50 mole% A and 50mole% inerts enter the reactor with
the flow rate of 6l/s at 144C. the rate data is as follows :
XA 0 0.1 0.2 0.2 0.4 0.5 0.6 0.7 0.8 0.85
-rA 0.0053 0.0052 0.005 0.0045 0.004 0.0033 0.0025 0.0018 0.00125 0.001
If the reaction is carried out in two reactors in series with 40% conversion in the
first reactor and 85% overall conversion, estimate the total volume of reactors when
a) Reactors are both mixed flow, and
b) Reactors are both plug flow.
2. A batch fermenter is being used for the production of yeast cells from glucose. The
number of yeast cells is found to be in 1.5h. find the average specific growth of
cells(μ).
3. What is the effect of mutation and contamination on the operation of a chemostat?
What are the problems associated with the culture of genetically engineered yeast in
continuous culture system?
4. What are the various types of fermentation reactions? Explain with examples.
Explain in detail what are the effects of temperature, pressure, Ph on fermentation
reactions.
5. Given the gas – phase reaction A = B + C. start with pure A. suppose that 50% of
the original A is dissociated at 1000K and 10 atm as well as at 500 K and 0.1 atm.
a) Calculate the percent dissociation at 250 K and 1 atm
b) Calculate the % dissociation at 250 K and 0.1 atm.
Data : Average Cp of A = 12 cal/mol K
Average Cp of B = 7 cal/mol K
Average Cp of C = 5 cal/mol K
6. Define the following :
a) Dispersion coefficient
b) Dispersion number
c) Pecklet number
d) Damkohler number
7. How do you control the cascade bioreactors? Explain in detail using mathematical
model.
8. Describe some characteristic features of a fermenter which are needed to be
considered while designing a fermenter.
What are the advantages and disadvantages of using off – centre impellers over baffles
for creating turbulence? Explain in detail.
BIO-CHEMICAL ENGINEERING Question Papers (Supple, 2007 Feb, RR)
SET :1
1. (a) Define the following terms: order of a reaction, molecularity, elementary and
non-elementary reactions.
(b) Explain the term steady-state approximation ? [8+8]
2. (a) What are the advantages of continuous Bioreactors over Batch Bioreactors?
(b) If continuous Bioreactors have so many advantages over batch bioreactors, why they
are not widely used in industry? [8+8]
3. Explain CSTR designs for Enzyme catalyzed reactions with neat sketches? [16]
4. Equimolar quantities of A, B and D are continuously fed to a mixed flow reactor.
The elementary reactions that proceed in the reactor are as follows:
A + D ------(K1)-----> P;
B + D ------(K2)-----> Q
Given K1/K2 = 0.2, calculate the fraction of ‘P’ forced when
(a) 50% of A is consumed and
(b) 50% of D is consumed [8+8]
5. Qualitatively find the optimum temperature progression to maximize Cs for the
Reaction scheme
A ---> R ---> S ---> T
Data E1=10, E2=25, E3=15, E4=10, E5=20, E6=25 [16]
6. A first order reaction A!B (K=0.25 Min−1) is carried out in a PFR. An RTD analysis
is carried out in this reactor and the following data is obtained.
T(Min) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
C(gm/m3) 0 1 5 8 10 8 6 4 3 2.2 1.5 1.0 0.6 0.2 0
Calculate the mean conversion obtained in the reactor using Tanks-in-series Model?
[16]
7. A 12 m length of pipe is packed with 1 m of 2 mm material, 9m of 1 cm material and
2 m of 4 mm material. Estimate the variance in output c curve for this packed section
if the fluid takes 2 min to flow through the section. Assume a constant bed voidage
and a constant intensity of dispersion given by D/4dp=2. [16]
8. Explain in detail the stiochiometry involved in the cell growth? [16]
SET :2
1. (a) Define the following terms: order of a reaction, molecularity, elementary and
non-elementary reactions.
(b) Explain the term steady-state approximation ? [8+8]
2. Enumerate in detail various environmental conditions that effect the Growth
kinetics? [16]
3. The Acqueous reaction A+B ! pdt with known kinetics
−rA = 500 (lit/MolMin)
CACB
is to take place in an experimental tubular reactor (Assume Plug flow) under the
following conditions.
Volume of Reactor V = 0.1 liter
Volumetric flow rate v= 0.05 lit/Min
Concentration of Reactant in feed CAO = CBO = 0.01 Mol/Liter
(a) What fractional conversion of reactants can be expected?
(b) For the same conversion as in part (a) what size of stirred tank reactor is
needed?
(c) What conversion can be expected in a mixed reactor equal in size to the plug flow
reactor? [4+6+6]
4. Equimolar quantities of A, B and D are continuously fed to a mixed flow reactor.
The elementary reactions that proceed in the reactor are as follows:
A + D ---(K1)----> P;
B + D ---(K2)----> Q
Given K1/K2 = 0.2, calculate the fraction of ‘P’ forced when
(a) 50% of A is consumed and
(b) 50% of D is consumed [8+8]
5. A tubular-flow reactor is to be designed for the production of butadiene from
butene by the gas phase reaction
C4H8 ---> C4H6 + H2
The composition of the feed is 10 moles of steam per mole of butene and no butadiene.
The hydrogen operates at 2 atmospheres pressure with an inlet (feed) temperature of
12000F. The reaction rate follows a first order, irreversible reaction for which the
rate constant ‘K’ as a function of temperature is
T,K 922(12000F) 900 877 855 832
K 11.0 4.90 2.04 0.85 0.32
[K = ImolButene reacted/(Hour /Liter) atm]
The heat of reaction may be taken as constant and equal to HR=26360 cal/gmol. The
specific heat of the feed stream may be regarded as constant and equal to 0.5 But/lb
0R. What would be the volume required for a conversion of 20% if the reactor were
operated isothermally at 12000F with a butene plus steam feed rate of 22 lb mol/hr.
[16]
6. Write short notes on:
(a) Non-Ideal Tubular reactor
(b) Non-Ideal CSTR [8+8]
7. A specially designed vessel is to be used as a reactor for a first order liquid
phase reaction. The following concentration reading represent the response at the
vessel outlet to a delta function input to the vessel inlet. What conversion can we
expect in this reactor if conversion in a mixed flow reactor employing the same space
time is 82.18%. [16]
Time(Sec) 10 20 30 40 50 60 70 80
Tracer concn. 0 3 5 5 4 2 1 0
8. The Reactor with a rate expression = ( maxS/Ks+S) is carried out in a series of
two stirred
tanks of equal size. Calculate the dilution rate required to reduced the substrate
concentration to 50 gm/lit with sterile feed given .max = 1hr−1 S0=20 gm/lit. Ks=2
gm/lit Yx/s=0.6? [16]
SET :3
1. (a) Define the following terms: order of a reaction, molecularity, elementary and
non-elementary reactions.
(b) Explain the term steady-state approximation ? [8+8]
2. Enumerate in detail various environmental conditions that effect the Growth
kinetics? [16]
3. “Fed batch culture as the paradigm for many efficient microbial processes” Justify
it? [16]
4. Equimolar quantities of A, B and D are continuously fed to a mixed flow reactor.
The elementary reactions that proceed in the reactor are as follows:
A + D ---(K1)----> P;
B + D ---(K2)----> Q
Given K1/K2 = 0.2, calculate the fraction of ‘P’ forced when
(a) 50% of A is consumed and
(b) 50% of D is consumed [8+8]
5. Qualitatively find the optimum temperature progression to maximize Cs for the
Reaction scheme
A ---> R ---> S ---> T
Data E1=10, E2=25, E3=15, E4=10, E5=20, E6=25 [16]
6. Develop an expression for external age distribution of N number of equal sized back
mixed reactor in series assuming tank in series model holds good. [16]
7. An RTD analysis was carried out on a liquid phase reactor. The following data is
obtained.
T(S) 0 150 175 225 240 260 275 300 350 375 400 450
C × 1000 gm/cm3 0 0 1 7.4 9.4 9.4 8.2 5.0 1.2 1.2 0.2 0
(a) Plot the E(t) curve for these data.
(b) What fraction of material spends between 230 and 270 second in the reactor?
(c) What is the residence time? [4+6+6]
8. Explain in detail the stiochiometry involved in the cell growth? [16]
SET :4
1. For a gas phase reaction A ! 2R, the following data were obtained at 1000C in a
constant volume batch reactor. Find the rate equation which will satisfactorily fit
the data. [16]
Time (Min) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 5.0 6.0 7.0
Total Pressure (atm) 1.3 1.5 1.7 1.8 1.85 1.90 1.95 2.0 2.03 2.08 2.1 2.15
2. (a) What are the advantages of continuous Bioreactors over Batch Bioreactors?
(b) If continuous Bioreactors have so many advantages over batch bioreactors, why they
are not widely used in industry? [8+8]
3. The Acqueous reaction A+B ! pdt with known kinetics
−rA = 500 (lit/MolMin) CACB
is to take place in an experimental tubular reactor (Assume Plug flow) under the
following conditions.
Volume of Reactor V = 0.1 liter
Volumetric flow rate v= 0.05 lit/Min
Concentration of Reactant in feed CAO = CBO = 0.01 Mol/Liter
(a) What fractional conversion of reactants can be expected?
(b) For the same conversion as in part (a) what size of stirred tank reactor is
needed?
(c) What conversion can be expected in a mixed reactor equal in size to the plug flow
reactor? [4+6+6]
4. Equimolar quantities of A, B and D are continuously fed to a mixed flow reactor.
The elementary reactions that proceed in the reactor are as follows:
A + D ---(K1)---> P;
B + D ---(K2)---> Q
Given K1/K2 = 0.2, calculate the fraction of ‘P’ forced when
(a) 50% of A is consumed and
(b) 50% of D is consumed [8+8]
5. For the optimum temperature Progression in a plug flow Reactor, CAO= 4Mol
liter ,
FAO =1000 MolA/Min , XA = 0.8, TMin=50C, TMax=950C and feed and product both at
250C, how much heating and cooling would be needed. [16]
(a) For the feed stream?
(b) In the Reactor itself?
(c) For the stream leaving the Reactor?
6. Develop an expression for external age distribution of N number of equal sized back
mixed reactor in series assuming tank in series model holds good. [16]
7. Explain about Tracer pulse experiment to calculate conversion with respect to
tanks-in-series model? [16]
8. Explain in detail the stiochiometry involved in the cell growth? [16]
BIO-CHEMICAL ENGINEERING Question Papers (Supple, 2007 Nov, RR)
SET :1
1. For a second order reaction 2HI ! H2 + I2, the following rate constants were
obtained at various temperatures. Estimate the Arrhenius parameters. Also determine
by what factor the rate increases when the temperature raises from 3000C to
3100C. [16]
Rate Constant ‘K’ : 1.78×10−5 1.07×10−4 3.07×10−4 1.05×10−3 1.51×10−2
(lit/Mol sec)
Temperature K : 633 667 697 715 781
2. An industrial waste-water stream is fed to a stirred tank reactor continuously and
the cells are recycled back to the reactor from the bottom of the sedimentation tank
placed after the reactor. The following are given for the system.
F = 100lit/hr S0 = 5000mg/lit Max = 0.25 hr−1
Ks=200 mg/lit (Recycle ratio) = 0.6C
Cell concentration factor C=2.
Y Mx/s =0.4.
The effluent concentration is desired to be 100 mg/lit.
(a) Determine the Required Reactor volume.
(b) Determine the cell concentration in the reactor and in the recycle stream. [8+8]
3. A Homogenous liquid phase reactionA ---> R; −rA = K CA2 takes place with 50%
conversion in a mixed Reactor.
(a) What will be the conversion if this reactor is replaced by one 6 times are large
all else remaining unchanged?
(b) What will be the conversion if the original reactor is replaced by a plug flow
reactor of equal size all else remaining unchanged? [8+8]
4. Equimolar quantities of A, B and D are continuously fed to a mixed flow reactor.
The elementary reactions that proceed in the reactor are as follows:
A + D ---(K1)---> P;
B + D ---(K2)---> Q
Given K1/K2 = 0.2, calculate the fraction of ‘P’ forced when
(a) 50% of A is consumed and
(b) 50% of D is consumed [8+8]
5. The Reversible first order Gas reaction is to be carried out in a mixed
flow Reactor. For operations at 300 K, the volume of Reactor required is 100 liters
for 60% conversion of A. What should be the volume of the reactor for the same feed
rate and conversion but with operations at 400 K? [16]
Date K1 = 103 e− 2415
T
Cp = CPR − CPA = 0
Hr = −8000Cal/mol at 300K
K = 10 at 300K
Feed consists of Pure ‘A total pressure stays constant
6. Develop an expression for external age distribution of N number of equal sized back
mixed reactor in series assuming tank in series model holds good. [16]
7. Write short notes on
(a) RTD
(b) State of aggregation
(c) Earliness and latensess of mixing [6+6+4]
8. Explain in detail the stiochiometry involved in the cell growth? [16]
SET :2
1. (a) Define the following terms: order of a reaction, molecularity, elementary and
non-elementary reactions.
(b) Explain the term steady-state approximation ? [8+8]
2. Consider a 1000-litre CSTR in which Biomass is being produced with glucose as the
substrate. The Microbial system follows a Monod relationship with Max=0.4hr−1, Ks=
1.5 g/litre and the yield factor Yx/s=0.5 g g biomass/g substrate consumed. If Normal
operation is with a sterile feed containing 10g/lit glucose at the rate of 100 lit/hr.
(a) What is the specific Biomass production rate at steady state?
(b) If Recycle is used with a recycle stream of 10 lit/hr and a recycle biomass
concentration five times as large as that in the reactor exit, what would be the new
specific biomass production rate? [8+8]
3. (a) One liter/min of liquid containing A and B (CAO=0.10 mol/liter, CB0=0.01
mol/liter flow into a mixed Reactor of volume V=1 liter. The materials react in a
complex manner for which the stiochiometry is unknown. The outlet stream from the
reactor contains A, B, and C (CAf=0.02 Mol/liter). Find the rate of reaction of A, B
and C for the conditions with in the reactor?
(b) Pure Gaseous Reactant A (CA0=100 Milli Mol/liter) is fed at steady Rate into a
mixed Reactor (V=0.1 liter) where it dimerizes (2A- - - R). For different gas feed
rates the following data are obtained.
Run Number 1 2 3 4
V0 lit./hr 30.0 9.0 3.5 1.5
CA, out (Mil limol/Lit) 85.7 66.7 50 33.3
Find a Rate equation for this reaction. [4+12]
4. Equimolar quantities of A, B and D are continuously fed to a mixed flow reactor.
The elementary reactions that proceed in the reactor are as follows:
A + D ---(K1)---> P;
B + D ---(K2)---> Q
Given K1/K2 = 0.2, calculate the fraction of ‘P’ forced when
(a) 50% of A is consumed and
(b) 50% of D is consumed [8+8]
5. A tubular-flow reactor is to be designed for the production of butadiene from
butene
by the gas phase reaction
C4H8 -----> C4H6 + H2
The composition of the feed is 10 moles of steam per mole of butene and no butadiene.
The hydrogen operates at 2 atmospheres pressure with an inlet (feed) temperature of
12000F. The reaction rate follows a first order, irreversible reaction for which the
rate constant ‘K’ as a function of temperature is
T,K 922(12000F) 900 877 855 832
K 11.0 4.90 2.04 0.85 0.32
[K = ImolButene reacted/(Hour /Liter) atm]
The heat of reaction may be taken as constant and equal to HR=26360 cal/gmol. The
specific heat of the feed stream may be regarded as constant and equal to 0.5 But/lb
0R. What would be the volume required for a conversion of 20% if the reactor were
operated isothermally at 12000F with a butene plus steam feed rate of 22 lb
mol/hr.[16]
6. Explain in detail about models for Non-Ideal reactors? [16]
7. Explain about Tracer pulse experiment to calculate conversion with respect to
tanks-in-series model? [16]
8. Explain in detail the stiochiometry involved in the cell growth? [16]
SET :3
1. (a) Define the following terms: order of a reaction, molecularity, elementary and
non-elementary reactions.
(b) Explain the term steady-state approximation ? [8+8]
2. (a) Explain the significance of dissolved oxygen stat?
(b) Explain the significance of PH stat? [8+8]
3. A first order reaction is to be treated in a series of two mixed reaction. Show
that the total volume of the two reactions is minimum, when the reactions are equal in
size? [16]
4. For the elementary reactions as shown in figure below 4
Figure 4
(a) Show that for plug flow that
CRMax
CAO
= K1
K1+K3 K2
K1+K3 K2
K1−K2+K3 at opt =
In(K1+K3
2 )
K1−K2+K3
(b) Show that for mixed flow that CRMax
CAO
= K1
(pK1+K3+pK2)2
at opt = 1
pK2(K1+K3)
[8+8]
5. Explain Rate, Temperature and conversion profiles for exothermic and endothermic
Reactions in Adiabatic flow Reactors? [16]
6. A closed vessel has flow for which D/UL=0.2 to represent the vessel by the tanks in
series model. What value of ‘N’ should be selected ? [16]
7. The flow characteristics of a continuous reactor are studied by suddenly
introducing a quantity of miscible tracer into the feed stream. The concentrations of
tracer in the effluent at various times after the instant of addition are
Tmin 0.1 0.2 1.0 2.0 3.0 10 30
Tracer concentration mg/liter 0.02 0.17 0.15 0.125 0.07 0.02 0.001
(a) What type of ideal reactor does the actual vessel closely approach.
(b) If an isothermal first order reaction K1 = 0.15 Min−1 occurs in the vessel, what
conversion may be expected ? [8+8]
8. Explain in detail the stiochiometry involved in the cell growth? [16]
SET :4
1. For a gas phase reaction A ! 2R, the following data were obtained at 1000C in a
constant volume batch reactor. Find the rate equation which will satisfactorily fit
the data. [16]
Time (Min) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 5.0 6.0 7.0
Total Pressure (atm)1.3 1.5 1.7 1.8 1.85 1.90 1.95 2.0 2.03 2.08 2.1 2.15
2. (a) What are the advantages of continuous Bioreactors over Batch Bioreactors?
(b) If continuous Bioreactors have so many advantages over batch bioreactors, why they
are not widely used in industry? [8+8]
3. From the following data find a satisfactory rate equation for the Gas phase
decomposition A---> R+S taking place isothermally in a mixed reactor. [16]
Run Number 1 2 3 4 5
Based on Inlet feed conditons (Sec) 0.423 5.1 13.5 44.0 19.2
XA(for CA0=0.002 Mol/lit) 0.22 0.63 0.75 0.88 0.96
4. Equimolar quantities of A, B and D are continuously fed to a mixed flow reactor.
The elementary reactions that proceed in the reactor are as follows:
A + D ---(K1)---> P;
B + D ---(K2)---> Q
Given K1/K2 = 0.2, calculate the fraction of ‘P’ forced when
(a) 50% of A is consumed and
(b) 50% of D is consumed [8+8]
5. Explain Rate, Temperature and conversion profiles for exothermic and endothermic
Reactions in Adiabatic flow Reactors? [16]
6. Develop an expression for external age distribution of N number of equal sized back
mixed reactor in series assuming tank in series model holds good. [16]
7. Explain about Tracer pulse experiment to calculate conversion with respect to
tanks-in-series model? [16]
8. The Reactor with a rate expression = ( maxS/Ks+S) is carried out in a series of
two stirred
tanks of equal size. Calculate the dilution rate required to reduced the substrate
concentration to 50 gm/lit with sterile feed given .max = 1hr−1 S0=20 gm/lit. Ks=2
gm/lit Yx/s=0.6? [16]
BIO CHEMICAL ENGINEERING Question Papers (Regular, 2006)
SET :1
1. (a) Define the following terms: order of a reaction, molecularity, elementary and
non-elementary reactions.
(b) Explain the term steady-state approximation ? [8+8]
2. Consider a 1000-litre CSTR in which Biomass is being produced with glucose as the
substrate. The Microbial system follows a Monod relationship with Max=0.4hr−1, Ks=
1.5 g/litre and the yield factor Yx/s=0.5 g biomass/g substrate consumed. If Normal
operation is with a sterile feed containing 10g/lit glucose at the rate of 100 lit/hr.
(a) What is the specific Biomass production rate at steady state?
(b) If Recycle is used with a recycle stream of 10 lit hr and a recycle biomass
concentration five times as large as that in the reactor exit, what would be the new
specific biomass production rate? [8+8]
3. Define Ideal Bioreactors? What are the conditions that contribute for their
ideality, Explain different classes of Ideal bioreactors? [16]
4. A Reversible, first order reaction A
K1
!
K2
R is carried out in a mixed flow reactor.
When the temperature of operation was 3000K, for a 60% conversion of A, the volume of
the reactor was found to be 100 litres. Show that it is not possible to obtain a
conversion of 60%. If the temperature of operation is 4000K. Find the temperature of
operation which would minimize the size of the mixed reactor for the same conversion
and feed rate.
Given K1 = 103 e= −4800RT ; CP = CPR ? CPA = 0.
Hr = -8 Kcal/mol at 3000K.
K = 10 at 3000K. Feed is pure A and total pressure is constant. [16]
5. Qualitatively find the optimum temperature progression to maximize Cs for the
Reaction scheme
A!R!S!T
Data E1=10, E2=25, E3=15, E4=10, E5=20, E6=25 [16]
6. The following data is obtained from a tracer test conducted in Non ideal reactor
Time(Sec) 10 20 30 40 50 60 70 80
CMol.s lit 0 3 5 5 4 2 1 0
(a) What fraction of the material is spent in the reactor between 20 and 50 sec?
(b) What fraction of the material is spent, less than the mean residence time of the
reactor. [8+8]
7. Response measurements to a step-function input time are made for a reaction vessel.
Time Sec 0 15 25 35 45 55 65 75 95
Tracer g/cm3 concn. 0 0.5 1.0 2.0 4.0 5.5 6.5 7.0 7.7
(a) Plot the RTD Vs time
(b) What is the mean residence time for this flow rate? [8+8]
8. Explain in detail the stiochiometry involved in the cell growth? [16]
SET :2
1. Data on the effect of temperature on the reaction between ethanol and acetic acid
are reported below. Find out the values of the constants in the Arrhenious equation.
[16]
T0C : 30 40 50 60 70
K lit/gmol-hr : 0.5 1.1 2.2 4.0 6.0
2. (a) Explain the significance of dissolved oxygen stat?
(b) Explain the significance of PH stat? [8+8]
3. 100 liters/hr of Radio active fluid having a half life of 20 hr is to be treated by
passing it through two ideal stirred tanks in series, V=40,000 liters each. In passing
through the system how much has the activity decayed? [16]
4. Given the Reactions
A + 2B ! R rR = K1CAC2
B with K2 = 2K
A + B ! S rS = K2CACB
(a) What are the fractional yield expressions 􀀀 􀀀 R
A and 􀀀 􀀀 R
B for this reaction system.
(b) How to operate a mixed reactor so as to maximize the production of R from a single
feed consisting of CAO = CBO = 1. [8+8]
5. The Reversible first order Gas reaction A
1
!
2
R is to be carried out in a mixed flow Reactor. For operations at 300 K, the volume of
Reactor required is 100 liters for 60% conversion of A. What should be the volume of
the reactor for the same feed rate and conversion but with operations at 400 K? [16]
Date K1 = 103 e− 2415
T
Cp = CPR − CPA = 0
Hr = −8000Cal/mol at 300K
K = 10 at 300K
Feed consists of Pure ‘A total pressure stays constant
6. Develop an expression for external age distribution of N number of equal sized back
mixed reactor in series assuming tank in series model holds good. [16]
7. Discuss the Techniques employed in Diagnosing the ills of operating equipment with
regard to Non ideal flow ? [16]
8. Explain in detail the stoichiometry involved in the cell growth? [16]
SET :3
1. (a) Define the following terms: order of a reaction, molecularity, elementary and
non-elementary reactions.
(b) Explain the term steady-state approximation ? [8+8]
2. How cells grow in continuous culture and explain about specific devices for
continuous culture? [16]
3. Explain CSTR designs for Enzyme catalyzed reactions with neat sketches? [16]
4. Reactant A in a liquid either isomerizes (or) dimerizes as follows
A ! R desired rR = K1CA
A+A ! S undesired rS = K2C2A
(a) Write (R/A) and 􀀀 􀀀 R
R+S with a feed stream of concentration CAO find
CRMax which can be formed
(b) in a plug flow reactor
(c) in a Mixed reactor. [4+6+6]
5. A tubular-flow reactor is to be designed for the production of butadiene from
butene by the gas phase reaction
C4H8 ! C4H6 + H2
The composition of the feed is 10 moles of steam per mole of butene and no butadiene.
The hydrogen operates at 2 atmospheres pressure with an inlet (feed) temperature of
12000F. The reaction rate follows a first order, irreversible reaction for which the
rate constant ‘K’ as a function of temperature is
T,K 922(12000F) 900 877 855 832
K 11.0 4.90 2.04 0.85 0.32
K = ImolButene reacted
(Hour /Liter) atm
The heat of reaction may be taken as constant and equal to HR=26360 cal/gmol.
The specific heat of the feed stream may be regarded as constant and equal to 0.5
But/lb 0R.
What would be the volume required for a conversion of 20% if the reactor were operated
isothermally at 12000F with a butene plus steam feed rate of 22 lb mol/hr. [16]
6. Develop an expression for external age distribution of N number of equal sized back
mixed reactor in series assuming tank in series model holds good. [16]
7. A 12 m ? length of pipe is packed with 1 m of 2 mm material, 9m of 1 cm material
and 2 m of 4 mm material. Estimate the variance in output c curve for this packed
section if the fluid takes 2 min to flow through the section. Assume a constant bed
voidage and a constant intensity of dispersion given by D 4dp=2. [16]
8. Explain in detail the stiochiometry involved in the cell growth? [16]
SET :4
1. (a) Define the following terms: order of a reaction, molecularity, elementary and
non-elementary reactions.
(b) Explain the term steady-state approximation ? [8+8]
2. Pencillin is produced by P. Chrysogenum in a fed batch culture with the
intermittent addition of glucose solution to the culture medium. The initial culture
volume at quasi ? steady state is V0=500 lit and Glucose containing nutrient solution
is added with a flow rate of F=50 lit/hr. Glucose concentration in the feed solution
and initial cell concentration are S0=300 g/lit and X0= 20 g/lit respectively. The
kinetic and yield coefficients of the organism are max=0.2 hr−1 Ks=0.5 g/lit and
Yx/s=0.3 g dw
g glu cos e .
(a) Determine the Culture volume at t=10hr.
(b) Determine the concentration of glucose at t=10hr at quasi-steady state.
(c) Determine the concentration and total amount of cells at quasi-steady state when
t=10hr. [4+6+6]
3. (a) One liter/min of liquid containing A and B (CAO=0.10 mol/liter, CB0=0.01
mol/liter flow into a mixed Reactor of volume V=1 liter. The materials react in a
complex manner for which the stiochiometry is unknown. The outlet stream from the
reactor contains A, B, and C (CAf=0.02 Mol/liter). Find the rate of reaction of A, B
and C for the conditions with in the reactor?
(b) Pure Gaseous Reactant A (CA0=100 Milli Mol/liter) is fed at steady Rate into a
mixed Reactor (V=0.1 liter) where it dimerizes (2A- - - R). For different gas feed
rates the following data are obtained.
Run Number 1 2 3 4
V0 lit./hr 30.0 9.0 3.5 1.5
CA, out Millimol
Lit 85.7 66.7 50 33.3
Find a Rate equation for this reaction. [4+12]
4. Equimolar quantities of A, B and D are continuously fed to a mixed flow reactor.
The elementary reactions that proceed in the reactor are as follows:
A + D
K1
−! P; B + D
K2
−! Q
Given K1/K2 = 0.2, calculate the fraction of ‘P’ forced when
(a) 50% of A is consumed and
(b) 50% of D is consumed [8+8]
5. The reaction between sodium thiosulfate and Hydrogen peroxide in dilute aqueous
solution is irreversible and second order in thiosulfate. The rate constant is the
following function of temperature
K = 6.85 × 10−4 e −18300
RT Cm3 / moles sec
Reaction stiochiometry indicates that 2 moles of H2O2 react with one mole of
Na2S2O3. The heat of reaction at 250C is HR = -131000 cal/gmol
Reactor volume = 2790 cm3
Feed temperature = 250C
Feed Rate = 14.2 cm3/s
Consider Adiabatic operation and feed concentration of 2.04×10−3 gmol/cm3 and
4.08×10−4 gmol/cm3 of thiosulfate and H2O2 respectively. What would be the
conversion and temperature in the reactor effluent? [16]
6. Develop an expression for external age distribution of N number of equal sized back
mixed reactor in series assuming tank in series model holds good. [16]
7. (a) The concentration readings in table given below represent a continuous response
to a delta function input into a closed vessel which is to be used as a chemical
reactor. Plot the exit age distribution E.
Time(Min) 0 5 10 15 20 25 30 35
Tracer output conce.I/lit. 0 3 5 5 4 2 1 0
(b) The vessel of above problem is to be used as a reactor for a liquid decomposing
with rate ?rA=KCA. K=0.307 min−1. Find the fraction of reactant unconverted in the
real reactor and compare with the fraction unconverted in a plug flow reactor of the
same size. [8+8]
8. Explain in detail the stiochiometry involved in the cell growth? [16]
BIO CHEMICAL ENGINEERING Question Papers (Supple, 2005)
SET : 1
1. The Elementary irreversible reaction 2A ® 2R + S is carried out in a Batch reactor
at constant pressure pure ‘A’ is taken initially at a concentration of 1.33 mol/litre.
The volume increases from 4–5 litres in the first ten minutes. Assuming ideal gas law
to hold good. Evaluate the reaction rate constant?
2. In Fed Batch Culture operating with intermittent addition of glucose solution,
values of the following parameters are given at t=2h, when the system is at quasi –
steady state.
V = 1000 ml F= dv/dt =200 ml/h
S0= 100 g glucose/lit mMax = 0.3 h-1
Ks=0.1g glucose/lit
YMx/s=0.5 g dw cells/g glucose
a) Find initial volume of the Culture.
b) Determine the concentration of Growth limiting substrate in the Vessel at quasi
steady state.
c) Determine the concentration and total amount of Biomass in the vessel at t=2h.
3. Explain the significance of PH stat ?
4. A Homogenous liquid phase reaction A®R -rA = K C
A2 takes place with 50% conversion in a mixed Reactor.
a) What will be the conversion if this reactor is replaced by one 6 times are large
all else remaining unchanged?
b) What will be the conversion if the original reactor is replaced by a plug flow
reactor of equal size all else remaining unchanged?
5. A reaction with following kinetics
rA = KCA where K = 0.0387 min-1 is to be carried out in each case of the following
systems at an initial concentration of A as CAO = 1.3 g mol/litre and it is desired to
obtain a conversion of 95%. Find residence times required.
a) For equal Distribution of feed stream into two perfectly mixed flow reactors in
parallel.
b) For the perfectly mixed equal sized reactors in series.
6. The Reversible first order Gas reaction A •1R
2
is to be carried out in a mixed flow Reactor. For operations at 300 K, the volume of
Reactor required is 100 liters for 60% conversion of A. What should be the volume of
the reactor for
the same feed rate and conversion but with operations at 400 K?
Data K1 = 103 e-2415T
DCP = CPR-CPA =0
DHr = -8000 Cal/mol at 300K
K = 10 at 300 K
Feed consists of Pure ‘A’ total pressure stays constant
7. Describe the Non-ideal flow patterns that may exist in commercial reactors and
outline a method for estimating residence time distribution in such reactors ?
8. Explain in detail the stiochiometry involved in the cell growth?
SET :2
1. a) Milk is pasteurized if it is heated at 630C for 30 min. But if it is heated to
740C, it only needs 15 sec, for the same result. Find the activation energy of the
sterilization process?
b) Explain the effect of temperature on the chemical reaction?
2. Consider a 1000-litre CSTR in which Biomass is being produced with glucose as the
substrate. The Microbial system follows a Monod relationship with mMax=0.4hr-1, Ks=
1.5 g/litre and the yield factor Yx/s=0.5 ggbiomass/g substrate
consumed. If Normal operation is with a sterile feed containing 10g/lit glucose at the
rate of 100 lit/hr.
a) What is the specific Biomass production rate at steady state?
b) If Recycle is used with a recycle stream of 10lithr and a recycle biomass
concentration five times as large as that in the reactor exit, what would be the new
specific biomass production rate?
3. Explain the exponential feeding strategy with respect to synchronous growth and its
application in product purification?
4. The Homogenous gas decomposition of phosphine 4PH3 (g) ® P4(g) + 6H2 proceeds at
12000K with first order rate
-r PH3 = •10
hr • CPH3
What size of plug flow reactor operating at 12000K and 4.5 atm can produce 80%
conversion of feed consisting of 4 Kg.mol of Pure phosphine per hour?
5. Equimolar quantities of A, B and D are continuously fed to a mixed flow reactor.
The elementary reactions that proceed in the reactor are as follows:
A + D •K1 P ; B + D •K2 Q
Given K1/K2 = 0.2, calculate the fraction of ‘P’ forced when
a) 50% of A is consumed and
b) 50% of D is consumed.
6. The thermal decomposition of Acetaldehyde CH3CHO(g) ® CH4(g)+CO(g) is studied in an
ideal tubular flow reactor at a constant total pressure of Pt atm. Suppose pure
acetaldehyde vapour enters the reactor at T0 K and a steady rate of F g/s. The Heat of
reaction, specific heat of the reaction mixture can be assumed constant and equal to
H
Cal
g mol
and CP Cal/Gmol0C. The rate of reaction is given by the second order equation.
r = A•e−E/RT • PA
2 gmol/s cm3.
Where ‘E’ is the activation energy, in calories per mole and PA is the partial
pressure of Acetaldehyde in atmospheres. If the reactor operates adiabatically,
express the rate of reaction in terms of the conversion as the sole variable.
7. Develop an expression for external age distribution of N number of equal sized back
mixed reactor in series assuming tank in series model holds good.
8. Explain specific growth with relevant equations?
SET : 3
1. The gas phase irreversible reaction (CH3)2O ® CH4 + H2 + CO was carried out in a
constant volume batch reactor at 5040C. Show that the following data explains the I
order kinetics and evaluate the rate constant. Initially products were not
present.
Time (sec) 390 777 1195 3155 ¥
PT (mm Hg) 408 488 562 799 931
2. In a two stage chemostat system, the volumes of the first and second reactors are
V1=500 lit and V2=300 lit respectively. The first reactor is used for Biomass
production and the second is for a secondary metabolite formation. The feed flow rate
to the first reactor is F=100lit hr and the glucose concentration in the feed is S=5.0
g/lit.
use mMax=0.3 hr-1 Ks=0.1 g/lit Yx/s=0.4.
a) Determine cell and Glucose concentrations in the effluent of the first stage.
b) Assume that Growth is Negligible in the second stage and the specific rate of
product formation is Qp=0.02 g p/g cell h and Yp/s=0.6g P/g s. Determine the product
and substrate concentrations in the effluent of the second reactor.
3. Explain the significance of dissolved oxygen stat?
4. A Homogenous liquid phase reaction A®R -rA = K C A2 takes place with 50% conversion
in a mixed Reactor.
c) What will be the conversion if this reactor is replaced by one 6 times are large
all else remaining unchanged?
d) What will be the conversion if the original reactor is replaced by a plug flow
reactor of equal size all else remaining unchanged?
5. A first order liquid phase reaction takes place in a mixed reactor with 92%
conversion. The suggestion is to recycle a fraction of the product stream with no
additional treatment. In what way it effects the conversion as long as the feed rate
is not altered ?
6. Consider the irreversible constant density reaction sequence
A + B •K2 C r2 = K2CACB
C •K1 D r1 = K1CC
The rate constants are K2 = A2e−E2/RT
K1 = A1=e−E1/RT
Component ‘C’ is the desired product. The feed. Contains no C (or) D and
CA=CAO, CB=CAO
a) If an isothermal tubular reactor is employed, develop equations for calculating the
conversion of A for which the yield of ‘C’ is maximum and for the constant temperature
at which the reactor should operate to give the highest value of the maximum yield of
C.
b) Develop equations for predicting the conversion of A for which the selectivity of
‘C’ with respect to ‘D’ is a maximum.
7. Determine the residence time distribution for an isothermal tubular-flow reactor in
which the liquid is in laminar flow in an annulus of inner radius r1 and outer radius
r2. Take a=r1/r2. the velocity in the Axial direction at any radius r is given by
u •r •= A[1−• r
r2 •2
•
1− 2
ln• 1
• ln
r
r2 ]
Express residence time distribution in terms of mean residence time q.
8. Obtain the Rate equation describing the kinetics of an enzymatic reaction in a
continuous stirred tank reactor by applying mass Balance?
SET :4
1. Data on the effect of temperature on the reaction between ethanol and acetic acid
are reported below. Find out the values of the constants in the Arrhenious equation.
T0C : 30 40 50 60 70
K lit/gmol-hr : 0.5 1.1 2.2 4.0 6.0
2. a) What are the advantages of continuous Bioreactors over Batch Bioreactors?
b) If continuous Bioreactors have so many advantages over batch bioreactors, why they
are not widely used in industry?
3. Explain the significance of dissolved oxygen stat?
4. Assuming a stiochiometry A ® R for a first order gas reaction, we calculate the
size of plug flow reactor needed for a given duty (99% conversion of a pure A feed) to
be V=32 liters. In that however the reaction stiochiometry is A®3R with this corrected
stoichiometry, what is the required reactor volume?
5. A mixture consisting of 90 mole% A (45 mole/lits) and 10 mole% impurity B(5
mol/lit). To be of satisfactory quality the mole ratio of A to B in the mixture must
be 100 – 1 (or) higher. D reacts with both A and B as follows.
A + D ® R -rA = 21CA CD
6. The vapour phase decomposition of phosphine, which is irreversible and first order,
follows the reaction
4PH3•g••P4•g••6H2•g•
Pure phosphine is fed to a tubular flow reactor, operating at 1 atm and adiabatically
with a feed temperature of 953 K. The reaction is endothermic, DHR = 23900 J/mol of
phosphine at 250C. The molal heat capacities (J/mol K) are
P4(g) CP = 25.1 + 0.0040 T
PH3•g• CP = 28.0 + 0.027 T
H2(g) CP = 30.1
The Rate constant K, S-1 is the following function of temperature ln
K = -27.94 + 2 ln T – 43,672
What volume to molal feed ratio (V/F) would be required to obtain a conversion of 10%
in one pass through the reactor ? What would be the conversion for the same V/F if the
reactor operated isothermally at 953 K ?
7. A liquid phase reaction is currently carried out commercially in a series of three,
equal volume stirred tank reactors operating isothermally. It is planned to replace
these reactors with a single tubular flow reactor. To obtain the same conversion as in
stirred tank equipment for the same Vt/Q; what degree of dispersion of Necessary in
the tubular reactor. Determine the value of DL/UL, if the flow in the tubular reactor
could be represented by dispersion model ?
8.a) Calculate the Dilution Rate required to reduce the substrate concentration from
20gm/lit to 5 gm/lit given Max = 1 hr-1 Ks=2gm/lit Yx/s=0.6 the feed is sterile?
b) A Micro organism is being continuously cultured in a chemostrat of volume 10 lit
and Monod model applies to the system with rx=0.5 gm/lit hr and Ks=gmlit Y, x/s = 0.8.
A sterile feed enters the reactor at a substrate concentration of 50gmlit. What would
be the substrate and Biomass concentration for a steady flow rate of 6 lit/hr?
BIO CHEMICAL ENGINEERING Question Papers (Regular 2005)
SET :1
1. The following data is reported for the decomposition of N2O5 in the gas phase at
450C. The reaction takes place in a constant volume batch reaction.
Time (Min) 10 20 30 40 50 60 70 80 90 100
PN2o5 (mm Hg) 247 185 140 105 78 58 44 33 24 18
Determine the order of the reaction and the reaction rate constant? [16]
2. Enumerate in detail various environmental conditions that effect the Growth
kinetics? [16]
3. One liter/sec of a 20% ozone-80% air mixture at 1.5 atm and 930C passes through a
plugflow reactor. Under these conditions ozone decomposes by homogenous reaction.
203 ! 302, −rozone = KC2
ozone K = 0.05 Liter
Mol/s
What size reactor is needed for 50% decomposition of Ozone? [16]
4. For the reaction A
K1=1,n1=1
−−−−−−! R
K2=1,n2=1
−−−−−−! S find CR,max
CAO
and opt at the outlet of the two equal sized mixed reactors in series. [16]
5. Explain Rate, Temperature and conversion profiles for exothermic and endothermic
Reactions in Adiabatic flow Reactors? [16]
6. A closed vessel has flow for which D
UL=0.2 to represent the vessel by the tanks in series model. What value of ‘N’ should
be selected ? [16]
7. Discuss the Techniques employed in Diagnosing the ills of operating equipment with
regard to Non ideal flow ? [16]
8. The Reactor with a rate expression = maxS
Ks+S is carried out in a series of two stirred tanks of equal size. Calculate the
dilution rate required to reduced the substrate concentration to 50 gm/lit with
sterile feed given .max = 1hr−1 S0=20 gm/lit
Ks=2 gm/lit Yx/s=0.6? [16]
SET :2
1. (a) For a first order reaction A!R, the rate constant is equal to 30 min−1. Find
the time needed for 95% conversion in a batch reactor if CAO = 1 mol/lit ?
(b) At 5000K the rate of bimolecular reaction is 10 times the rate at 4000K. Find the
activation energy of this reaction from Arrhenius law ? [8+8]
2. Enumerate in detail various environmental conditions that effect the Growth
kinetics? [16]
3. In an Isothermal Batch Reactor 70% of liquid reactant is converted in 13 min. What
space-time and space velocity are needed to effect this conversion in a plug flow
reactor and mixed flow reactor. [16]
4. A reaction with following kinetics
rA = KCA where K = 0.0387 min−1 is to be carried out in each case of the following
systems at an initial concentration of A as CAO = 1.3 g mol/litre and it is desired to
obtain a conversion of 95%. Find residence times required.
(a) For equal Distribution of feed stream into two perfectly mixed flow reactors in
parallel.
(b) For the perfectly mixed equal sized reactors in series. [8+8]
5. The vapour phase decomposition of phosphine, which is irreversible and first order,
follows the reaction
4PH3(g) ! P4(g) + 6H2(g)
Pure phosphine is fed to a tubular flow reactor, operating at 1 atm and adiabatically
with a feed temperature of 953 K. The reaction is endothermic, HR = 23900 J/mol of
phosphine at 250C. The molal heat capacities (J/mol K) are
P4(g) CP = 25.1 + 0.0040 T
PH3(g) CP = 28.0 + 0.027 T
H2(g) CP = 30.1
The Rate constant K, S−1 is the following function of temperature ln K = -27.94
+ 2 ln T 43,672 What volume to molal feed ratio (V/F) would be required to obtain a
conversion of 10% in one pass through the reactor ? What would be the conversion for
the same V/F if the reactor operated isothermally at 953 K ? [16]
6. The first order reaction A ! B is carried out in a 10 mm diameter tubular reactor
6.36 m in length. The specific reaction rate is 0.25 min−1. Following are the results
of a tracer test carried out in this reactor. Calculate the conversion using tanks-inseries
model. [16]
t(sec) 0 1 2 3 4 5 6
c(mg/lit) 0 1 5 8 10 8 6
t(sec) 7 8 9 10 12 14
c(mg/lit) 4 3 2.2 1.5 0.6 0
7. Determine the residence time distribution for an isothermal tubular-flow reactor in
which the liquid is in laminar flow in an annulus of inner radius r1 and outer radius
r2. Take =r1/r2. the velocity in the Axial direction at any radius r is given by
u(r) = A1 − r
r22
+ 1−2
1n( 1
)
1n r
r2
Express residence time distribution in terms of mean residence time . [16]
8. Explain in detail the stiochiometry involved in the cell growth? [16]
SET :3
1. (a) Define the following terms: order of a reaction, molecularity, elementary and
non-elementary reactions.
(b) Explain the term steady-state approximation ? [8+8]
2. (a) What are the advantages of continuous Bioreactors over Batch Bioreactors?
(b) If continuous Bioreactors have so many advantages over batch bioreactors, why they
are not widely used in industry? [8+8]
3. The flow through a plug flow reactor affecting a first order irreversible reaction
is increased by 20% and in order to maintain the same fractional conversion it is
decided to increase the reactor operating temperature. If the reaction has an
activation energy of 4000 Cal/mole and the initial temperature is 1500C. Find the New
operating temperature of the reactor? [16]
4. A first order liquid phase reaction takes place in a mixed reactor with 92%
conversion. The suggestion is to recycle a fraction of the product stream with no
additional treatment. In what way it effects the conversion as long as the feed rate
is not altered? [16]
5. The exhaust from an internal combustion engine contains some unburned fuel and
carbon monoxide, combustion can be continued if an after burner is placed in the
exhaust line. Suppose such an after burner operates as an adiabatic, stirred tank
reactor with an average residence time of 9 seconds. Consider only the further
oxidation of CO and Assume that in excess air, the oxidation is first order and
irreversible with the following rate constant
K(s−1) = 1.5×1010 e −272RT
E = 272 KJ / mol.
If the combustion gases enter at 1073 K. What are the steady state values of the
temperature and CO conversion in the effluent. [16]
6. Water is drawn from a lake flows through a pump and passes down a long pipe in
turbulent flow. A slug of tracer enters the intake line at the lake and is recorded at
two locations in the pipe L meters apart. The mean residence time of fluid between
recording points is 100 sec and the spread in the two recorded signals is
2
1 = 800 sec2 ; 2
2 900 sec2
What would be the spread of C curve for a section of this pipe, free from end effects
and of length L/5 ? [16]
7. Explain the role of RTD, State of Aggresation, earliness of mixing in determining
reactor behaviour? [16]
8. A strain of mold was grown in Batch culture on Glucose and the following data were
obtained.
Time(h) 0 9 16 23 30 34 35 40
Cell concentration (g/1) 1.25 2.45 5.1 10.5 22 33 37.5 41
Glucose Concentration (g/1) 100 97 90.4 76.9 48.1 20.5 9.38 0.63
(a) Calculate the Maximum Specific Growth Rate.
(b) Calculate the Apparent Growth Yield
(c) What maximum cell cencentration could one expect of 150g of Glucose were used with
the same size inoculum? [4+6+6]
SET :4
1. A Bimolecular Reaction A+B ! R+S, with the rate equation rA = KCACB is carried out
isothermally in a batch reactor.
(a) Derive the following reaction
ln
M−XA
M (1−XA) = CAO (M − 1) Kt
Where M = CAO
CBO
(b) Using the following data, find the time needed for 50% conversion of A. No R and S
are present initially.
K = 0.003 lig/gm mol-hr
CAO = 4 gm mol/lit; CBO = 10 gm mol/lit.
(c) Also determine the volume of Batch reactor required for producing 1000 Kg of R per
day if half an hour time is needed for charging, discharging and cleaning each batch.
Molecular weight of R is 88. [8+4+4]
2. The specific growth Rate for inhibited growth in a chemostat is given by the
following equation
g = MaxS
Ks+S +IKs /KI
Where S0= 10 g/lit Ks= 1 g/lit I=0.05 g/lit
Y M
x/s = 0.1 g Cells
g subs X0 = 0 K1 = 0.01/lit
Max=0.5 hr−1 Kd=0
(a) Determine X and s as a function of ‘D’ when I=0
(b) With inhibitor added to a chemostat, Determine the effluent substrate
concentration and X as a function of D.
(c) Determine Cell productivity DX, as a function of Dilution rate. [4+6+6]
3. Write short notes on:
(a) Fed-batch reactors
(b) Enzyme catalyzed reactions in CSTR [8+8]
4. Equimolar quantities of A, B and D are continuously fed to a mixed flow reactor.
The elementary reactions that proceed in the reactor are as follows:
A + D K1
−! P; B + D K2
−! Q
Given K1/K2 = 0.2, calculate the fraction of ‘P’ forced when
(a) 50% of A is consumed and
(b) 50% of D is consumed [8+8]
5. Explain Rate, Temperature and conversion profiles for exothermic and endothermic
Reactions in Adiabatic flow Reactors? [16]
6. Develop an expression for external age distribution of N number of equal sized back
mixed reactor in series assuming tank in series model holds good. [16]
7. Explain about Tracer pulse experiment to calculate conversion with respect to
tanks-in-series model? [16]
8. Derive the Equation dci
dt =rfi + f(t)
VR
(c if -ci) representing the kinetics of a fed batch reactor system by applying mass
Balance? [16]
BIO CHEMICAL ENGINEERING Question Papers (Regular 2004)
1. What are the Assumptions necessary in deriving the rate expressions for
Nonelementary reactions? Also mention the sequence of steps involved in the formation
of Chain reaction?
2. How cells grow in continuous culture and explain about specific devices for
continuous culture?
3. Explain the significance of dissolved oxygen stat?
4. In an Isothermal Batch Reactor 70% of liquid reactant is converted in 13 min. What
space-time and space velocity are needed to effect this conversion in a plug flow
reactor and mixed flow reactor.
5. A Reversible, first order reaction A R
1
2
K
K¬¾¾® is carried out in a mixed flow reactor. When the temperature of operation was
3000K, for a 60% conversion of A, the volume of the reactor was found to be 100
litres. Show that it is not possible to obtain a conversion of 60%. If the temperature
of operation is 4000K. Find the temperature of operation, which would minimize the
size of the mixed reactor for the same conversion and feed rate.
Given K1 = 103RT4800
e = - ; DCP = CPR – CPA = 0.
DHr = -8 Kcal/mol at 3000K. K = 10 at 3000K. Feed is pure A and total pressure is
constant.
6. Explain Rate, Temperature and conversion profiles for exothermic and endothermic
Reactions in Adiabatic flow Reactors?
7.a) Explain the significance of Residence Time distribution data and how the same may
be used in the design of non-ideal flow reactors?
b) Explain the significance of E, F and C curves. How these functions are
interrelated? Draw the E and F curves for ideal plug flow reactor and mixed flow
reactor respectively?
8. Describe kinetics in Batch culture and Growth Patterns?
SET : 2
1. What are the various methods used in the Analysis of Batch Reactor Kinetic data?
Explain them?
2. Derive the Monod chemostat model for a CSTR operating with Sterile feed. Deduce
equations for substrate and Biomass concentration?
3. Explain the significance of PH stat?
4. A first order reaction is to be treated in a series of two-mixed reaction. Show
that the total volume of the two reactions is minimum, when the reactions are equal in
size?
5. The first order liquid phase reaction in series A®R®S is to be carried out in a
flow reactor, so as to maximize the intermediate ‘R’. Prove that the optimum space
time is equal to the reciprocal of log mean of the rate constants for the case of plug
flow reactor and to the reciprocal of Geometric mean of the rate constants for the
case of a mixed flow reactor. ?
6. For the optimum temperature Progression in a plug flow Reactor,
CAO=
liter
4Mol , FAO=1000
Min
M01A , XA = 0.8, TMin=50C, TMax=950C and feed and product both at 250C, how much
heating and cooling would be needed.
a) For the feed stream?
b) In the Reactor itself?
c) For the stream leaving the Reactor?
7. Discuss the Techniques employed in Diagnosing the ills of operating equipment with
regard to Non ideal flow?
8. A solution containing Bacteria at a concentration of 0.001 g/dm3 was fed to a semi
batch reactor. The nutrient was in excess and the Growth rate law is first order in
the cell concentration. The Reactor was empty at the start of the experiment. If the
concentration of Bacteria in the reactor at the end of 2h is 0.0025 g/dm3 what is
specific growth rate K in Min-1-?
SET : 3
1. Derive the michaelis – menten kinetic model for a single substrate, irreversible
enzyme catalysed reaction with the following mechanism.
E + S Û ES ® P + E
2. Classify the methods used in the quantification of cell concentration and Explain
them?
3. Explain the exponential feeding strategy with respect to synchronous growth and its
application in product purification?
4. The flow through a plug flow reactor affecting a first order irreversible reaction
is increased by 20% and in order to maintain the same fractional conversion it is
decided to increase the reactor operating temperature. If the reaction has an
activation energy of 4000 Cal/mole and the initial temperature is 1500C. Find the New
operating temperature of the reactor?
5. Discuss product distribution in series and parallel multiple reactions?
6. Consider the irreversible constant Density reaction sequence
A + B 2 C ¾¾K¾® r2 = K2 CACB
C 1 D ¾¾K¾® r1 = K1CC
The rate constants are
K2 = E /RT
2
A e 2
- ; K1 = E /RT
1
A e 1 -
Component ‘C’ is the desired product. The feed contains no ‘C’ or ‘D’, and CA=CAO,
CB=CBO.
a) In an CSTR, develop equations for calculating the conversion of ‘A’ for which the
yield of ‘C’ is a maximum and for the constant temperature at which the reactor should
operate to give the highest value of the maximum yield of ‘C’.
b) Develop equations for predicting the conversion of ‘A’ for which the selectivity of
C with respect to ‘D’ is a maximum?
7. A 12 m – length of pipe is packed with 1 m of 2 mm material, 9m of 1 cm material
and 2 m of 4 mm material. Estimate the variance in output c curve for this packed
section if the fluid takes 2 min to flow through the section. Assume a constant bed
voidage and a constant intensity of dispersion given by
2
4
=
dp
D
.
8. Derive the Rate equation representing the kinetics of enzymatic reaction in a Batch
reactor at any time ‘t’?
SET : 4
1. Show that the formation of 2A+B ® A2B can be expressed by the predicated rate
expression
[ ]
[ ] [ ]
2 3
2
1 3
2 K K A
K K A Br
r A B +
=
2. Enumerate in detail various environmental conditions that effect the Growth
kinetics?
3. Explain the significance of PH stat?
4. Substance A reacts according to second order kinetics and conversion is 95% from a
single flow reaction. A second unit identical to the first. For the same conversion,
by how much is the capacity increased if these two units are operated in parallel (or)
series?
a) The Reactor are both Plug flow.
b) The Reactor are both mixed flow.
5. A and B react with each other as follows
2A ® R rR = K1CA
2
A+B ® S rS = K2CACS
2B ® T rT = K3CB
2
Find what rato of A to B should be maintained in a mixed reactor so as to maximize the
fractional yield of desired products?
6. The exhaust from an internal combustion engine contains some unburned fuel and
carbon monoxide; combustion can be continued if an after burner is placed in the
exhaust line. Suppose such an after burner operates as an adiabatic, stirred tank
reactor with an average residence time of 9 seconds. Consider only the further
oxidation of CO and Assume that in excess air, the
oxidation is first order and irreversible with the following rate constant
K (s-1) = 1.5x1010
RT
e
- 272
E = 272 KJ / mol.
If the combustion gases enter at 1073 K. What are the steady state values of the
temperature and CO conversion in the effluent?
7. Calculate the conversion in a laminar flow tubular reactor for a second-order
reaction A+B ® C for which K2 = 100 cm3/gmols and mean residence time q = 10s . The
feed concentration of both reactors is the same 10-3 gmol/cm3. Neglect the molecular
diffusion so that flow is segregated?
8. Explain the following
a) Di Auxic lag
b) Growth Limiting substrate
c) Wash Out condition.