Papers : IFS - Indian Forest Service Chemical Engineering Previous Year Paper (2007)

PAPER - I : SECTION A

1. Answer any four of the following : (10 × 4 = 40)
(a) Prove that the velocity profile in a laminar flow of a Newtonian fluid through a circular pipe is a parabola.
(b) (i) Differentiate between differential and cumulative analysis to find the average size of the sample.
(ii) Derive the expression for the critical speed of a ball mill. Mention the meanings of symbols and their units clearly.
(c) Define humidification and dehumidification, Explain the working of a water cooling tower with a neat diagram.
(d) Derive the relation between rate of heat transfer and resistances in series in a composite wall.

2. (a) Starting from the first principles, obtain Bernoulli’s equation from momentum balance in potential flow and extend the equation for practical applications. (10)
(b) Define capacity and effectiveness of a screen. Derive an expression for the overall effectiveness of a screen. (10)
(c) Explain different types of fluidisation and their applications. (10)
(d) Give a critical account of Rittinger’s and Bond’s laws. (10)

3. (a) Explain the mechanism of drying during the constant rate and failing rate periods. Discuss the effects of humidity and velocity of the gas on drying rate. (10)
(b) Mention the various types of crystallisation equipment used in the process industry. Explain the working of any one of the crystallisers with a neat diagram. (10)

(c) Write the suitable conditions for liquid- liquid extraction. Discuss the importance of equilibrium distribution coefficient and selectivity in the choice of a solvent. (10)
(d) Write the procedure in detail for the design of a distillation column by Mc Cabe-Thiele method. (10)

4. (a) Discuss briefly the various regimes in boiling heat transfer. (10)
(b) Describe the construction of shell and tube heat exchanger with a neat sketch. (10)
(c) Define the capacity and steam economy of an evaporator. Discuss the effect of boiling point elevation on evaporator performance. (10)
(d) Air is heated in air heather from 30° C to 110°C and the hot gases are cooled from 210° C to 145°C. calculate the LMTD in parallel and counter glows. Give critical comments of the values obtained. (10)


SECTION B
5. Answer any four of the following: (10 × 4 = 40)
(a) Discuss various types of membranes.
(b) Write the design procedure of either torispherical head or elliptical head.
(c) Mention the principal stresses induced in a vessel. How they act over the vessel.
(d) Differentiate between pneumatic and electronic controllers.
(e) List the various liquid level measuring instruments. Give their range and applications.

6. (a) Compare and contrast the terms— osmosis” and “reverge osmosis”. (10)
(b) Discuss the principles of ultrafiltration. Mention its applications. (10)
(c) Describe the processes of dialysis and also of electrodialysis. Write their applications. (10)
(d) Briefly discuss about “Super critical fluid extraction”. (10)

7. (a) Discuss the selection of material of construction for pressure vessels. (10)
(b) Explain the design procedure for vertical type storage vessels.
(c) Mention various types of heads commonly used in cylindrical vessels and list their applications. (10)
(d) Define joint efficiency. Mention the factors influencing the choice of supports. (10)

8. (a) Explain the working principles involved in various pressure measuring instruments. (10)
(b) (i) Explain the negative and positive feedback control system. (5)
(ii) Explain the servo and regulatory control problems. (5)
(c) What are the elements of computer based process control? Explain their functions. (10)
(d) What are phase and gain margins? Discuss the bode stability criterion. (10)


PAPER - II : SECTION A
1. Answer any four of the following (Maximum 150 words):
(a) Discuss reversible thermodynamic processes. (10)
(b) Write short note on fugacity. (10)
(c) Write short note on reactors in series. (10)
(d) A solution of naphthalene, C10H8, in benzene, C6 H6, contains 25 mole per cent of naphthalene. Express the composition of the solution in weight percent. (10)

(e) A solution of Sodium Chloride in water contains 230 grams of NaCl per liter at 20°C. The density of solution at this temperature is 1.148 grams per cubic centimeter, calculate :
(i) Volumetric percent of water
(ii) Composition in mole percent
(iii) Modality.
Note : density of water at 20° C = 0.998 g/cc.

2. (a) The liquid phase reaction, (where K1=8 liter/mol.min K2=3 liter/mol.min) is carried out in 150 litre stirred tank reactor under steady state conditions. Reactants A and B are fed to the reactor at equal volumetric flow rates. The concentrations of A and B streams are 2.8 mole A/ litre and 1.6 mole B/litre. What should be the flow rate of each stream to get 75% conversion of the limiting reactant? (25)

(b) Prove that the heat transferred equals the enthalpy change of the system for a mechanically reversible, constant-volume, constant-pressure, non- flow processes. (15)

3 (a) A steel casting [Cp = 0.5 kJ kg-1 K-1] weighing 40 kg and at a temperature of 450°C is quenched in 150 kg of oil [Cp = 2.5 kJ kg-1 K-l at 25°C. If there are no heat losses, what is the change in entropy of :
(i) the casting,
(ii) the oil and
(iii) both considered together? (25)

(b) Derive the expression for the design equation of tubular reactor. (15)

4. (a) One litre/mm of liquid containing A and B [CA0 = 0.10 mol/litre, CBO =0.01 mol/litre] flow into a mixed reactor of volume of one litre. The materials react in a complex manner for which the stoichiometry is unknown. The outlet streak from the reactor contains A, B and C(CAf = 0.02 mol/litre, Cbt= 0.03 mol/litre, Ccf = 0.04 mol/litre). Find the rate of reaction of A, B and C for the conditions within the reactor. (20)

(b) Chlorobenzene is nitrated using a mixture of nitric acid and sulphuric acid. During the pilot plant studies, a charge consisted of 100 kg chlorobenzene (CB), 106.5 kg 65.5% (by weight) nitric acid and 108 kg 93.6% (by weight) sulphuric acid. After two hours of operation, the final mixture was analysed. It was found that the final product contained 2% unreacted chlorobenzene. Also the product distribution was found to be 66% p-nitrochlorobenzene and 34% o-nitrochloro benzene, calculate:
(i) The analysis of charge
(ii) The percentage conversion of chlorobenzene. (20)

SECTION B
5. Answer any four of the following in brief (Maximum 150 words):
(a) PERT (10)
(b) Break-even analysis (10)
(c) Biogas (10)
(d) Essential oils (10)
(e) Norms for air emission. (10)

6. Describe manufacture of ammonia giving neat flow diagram and discuss its major pollution problems. (40)

7. (a) Suggest and justi1’ a location for a soda ash plant. (20)
(b) Discuss greenhouse effect. (20)

8. (a) Discuss cracking in brief. (20)

(b) The original value of a piece of equipment is Rs. 22,000. Its salvage value is Rs. 2,000 at the end of service life of 10 years. Determine the book value of the equipment at the end of 5 years using:
(i) Straight-line method
(ii) Textbook declining-balance method
(iii) Double declining-balance method. (20)