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# Indian Institute of Technology Kharagpur (IIT-K) 2007 B.Tech Chemical Engineering Instrumentation and process control - Question Paper

Wednesday, 23 January 2013 11:45Web

INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR

Instrumentation & Process Control (CH33008)

Date of Examination:22/2/2007    Time: 2 hrs Mid Spring Semester, 2007    Full Marks: 30 Course: B.Tech in Chemical Engineering    No. of students: 38

Ql. A simple exothermic reaction A->B with first order kinetics takes place in a jacketed tubular reactor. Due to very large heat of reaction, molten salt, which flows counter-currently in the jacket, is used as coolant to maintain the reaction temperature at acceptable levels. The reaction takes place in the gas phase. The flow rates are volumetric and the compositions are in moles/volume.

(a)    Develop a dynamic model for the process assuming i) constant temperature for the molten salt along the length of the reactor, ii) plug flow conditions inside the tube, iii) temperature dependence of kinetic rate constant obeys Arrhenius law. Nomenclature should be provided for each variable used in modeling.

(b)    Develop the linearized model in terms of deviation variable.

[7+3]

Q2. Consider the system shown below.

gas

I

liquid

Flow In

Flow out

>

[P.T.O]

(a)    Develop a mathematical model to describe dynamic change in level (h) of the liquid and pressure (P) of the non-condensable gas. Assume isothermal compression and expansion of the gas due to liquid level changes. The square root relationship between flow out from the system and the pressure difference can also be assumed.

(b)    Find the transfer function relating pressure of the gas to liquid inflow.

[5+5]

Q3. a) The under damped response for unit step input change to a general 2nd order process is given by

1-

where,

and <j) = tan

CO =

\$

Derive expression for i) rise time and ii) decay ratio.

b) A cylindrical tank is used for storage between a tank car unloading facility and a continuous reactor. Feedstock is simultaneously transferred from the tank car to the storage tank and from the storage tank to the reactor. The reactor feed exits the storage tank at a constant flow rate of 0.02 m3/sec. The operator has to be careful not to let the storage tank overflow or empty. The storage tank is 5 meter high and has an internal area of 4 m2. Suppose after a long period of operation, the storage tank level is 2 meter at the time tank car empties (no more tank car available). How long can the reactor be operated with the feedstock in the storage tank?

[2+2+6]