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.