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 deter-
mine 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 μMax = 0.25 hr−1
Ks=200 mg/lit α(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
Δ Cp = CPR − CPA = 0
Δ 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 μMax=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 τopt =
In(K1+K3
2 )
K1−K2+K3
(b) Show that for mixed flow that CRMax
CAO
= K1
(pK1+K3+pK2)2
at τopt = 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
λBased 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 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]