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 = y_A f_{A, pure substance} = y_A π (f_{A, pure substance} / π )

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 X_{A, 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 (C_AO = 100) to produce wanted R and unwanted S and the following progressive concentration reading are recorded :

C_A (100) 90 80 70 60 50 40 30 20 10 (0)

C_R (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 Ψ versus C_A curve for this reaction. With a feed C_AO = 100 and C_Af = 10, find C_R

b) From a mixed flow reactor

c) From a plug flow reactor

d) Repeat parts (b) and (c) with the modification that C_AO = 70

5. For the system with C_AO = 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 , dC_R/dt = dC_T/dt = k₁C_A^1.5C_B^0.30

Is accompanied by the undesired side reaction

A + B --------------- S + U , dC_S/dt = dC_U/dt = k₂C_A^0.50C_B^1.8

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 :

X_A 0 0.1 0.2 0.2 0.4 0.5 0.6 0.7 0.8 0.85

-r_A 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)

C_AC_B
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 C_AO = C_BO = 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 μ= (μmaxS/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 μ.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) C_AC_B
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 ,
F_AO =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]