CH4404 Process Technology 1

CH4404 Process Technology 1 Page 1 of 6 Spring 2018
UNIVERSITY of LIMERICK
OLLSCOIL LUIMNIGH
School of Natural Sciences
Department of Chemical Sciences
End of Semester Assessment
Module Code: CH4404
Module Title: Process Technology 1
Lecturer(s): Dr. Saeed Shirazian

Dr. Peter Davern
Semester: Spring 2018
Duration of Exam: 2.5 hours
Grading Scheme: 70% Examination

30% Labs
Instructions to Candidates:
_____________________________________________________________________
1. There are three questions in this paper. Answer full questions.

2. Please use a separate answer booklet for Peter Davern’s parts (1b and 2d, marked PD).
3. Any non-programmable calculator may be used provided it has been cleaned of any information
that would subvert the purpose of the examination.
4. Calculations must be shown in sufficient detail to illustrate your understanding of the procedure.
5. An equation sheet is attached for your use in answering the questions.
6. Please write clearly and readably.
Question 1.
Q1. (a) A stirred tank flow reactor is operating in continuous mode (shown below), and an
exothermic (heat generating) chemical reaction is taking place inside the reactor. The control
objective is to maintain the concentration of product at a desired value (set point). The conversion
of chemical reaction is highly dependent on the reaction temperature. To maintain the reaction
temperature at the desired value, a cooling water jacket is used for the reactor. The major input
disturbance is fluctuation in the temperature of the Reactant in stream. The temperature of the
reactor is controlled by adjusting the flow rate of cooling water.
(i) Draw a simple diagram to show the physical representation of how a Feedback control loop
could be achieved (label clearly all items on your diagram) (5 marks)
(i) Draw a conventional block diagram to represent this process control system. Show clearly in
your diagram the input and output variables from each operational block and define each
variable. Explain the nature of each of the transfer functions for all of the operational blocks
in your diagram.
(12 marks)
Q1. (b) PD [Peter Davern’s section: please answer in a separate answer booklet]
Clearly define the following terms:

• hazard
• harm
• risk
(3 x 1 mark)
Q1 (b) continued
Describe the two different types of respiratory tract irritant. In your answer provide one
example of each type.
(2 x 1 mark)
List two acute and two chronic health effects of excessive exposure to organic solvents.
(4 x ½ mark)
Briefly explain the meaning of the two CLP hazard classification pictograms illustrated
below:
Symbol A Symbol B
(2 x ½ mark)
Question 2.
Q2. (a) Describe briefly various types of control configurations used in manufacturing process.
(3 marks)
Q2. (b) Describe two different types of controllers in terms of the relation between the error and the
output of the controller.
(2 marks)
Q2. (c) An open loop response experiment is to be performed on a controller. The following error
signal profile is to be used:
0
E (%) 0 1 2 3 4 5 6 7
-1
-2
-3
Time (sec)
Q2. (c) continued

Plot qualitatively the shape of the corresponding controller output signal
versus time for
(i) Integral control mode only
(ii) Derivative control mode only
Show clearly the variation in controller output during each 1 second time interval from
time = 0 to time = 6 seconds. Indicate which sections (if any) of the plots are linear (L) and
which are non-linear (N). You may assume that error signal is defined as set-point value
minus measured value, and that the initial controller output is 50%.
(12 marks)
Q2. (d) PD [Peter Davern’s section: please answer in a separate answer booklet]
The classification of active human failures is divided into intentional and unintentional
errors. Describe the different types of unintentional errors.
(3 marks)
The ‘Hierarchy of Control’ plays an important role in the management of chemicals in the
workplace. Describe the main levels in the ‘Hierarchy of Control’.
(5 marks)
Question 3.
A cylindrical vessel is used for a chemical reaction. It is desired to model the dynamic response
behaviour of the vessel shown below:
Gas flows into the vessel at a volumetric flow rate of V in and there is an outflow of gas through the
fixed flow restrictor, R. The volume of the vessel, V, changes depending on both the inlet and
outlet flow rates. You may assume that Vout = V/R, and that the gas has a constant density.
Q3. (a) Starting from first principles, derive a differential equation which models the dynamic
response of the vessel volume, V, to changes in the inlet flow rate, V in.
(5 marks)
Q3. (b) Using the equation from (i) derive, in a series of clearly explained logical steps, an
algebraic expression which relates V to time, for a step increase in Vin.
(10 marks)
Define clearly all of the parameters used in your derivations for (i) and (ii).
Q3. (c) Given that R = 2 minutes and that the vessel volume is 10000 cm3 initially, calculate the
vessel volume at 3 minutes and 10 minutes after V in has begun to increase at a constant rate of 1
cm3.min.-2
(5 marks)
Process Technology 1 CH4404 Equation Sheet
Time Function Laplace Transform

f(t) F(s)
a a/s
at a/s2
df(t)/dt sF(s) - f(0)
e-at 1/(s+a)
1
b-a
(
e − at − e − bt ) 1
(s + a )(s + b )
1
a2
(
at − 1 + e − at ) 1
s (s + a )
2
(where a and b are constants associated with the input signal)
 4 t  t D (32 + (6t D / )) 4t D

Kp =  + D TI = TD =
Kt D  3 4  (13 + (8t D / )) (11 + (2t D / ))
Kp = 0.6K TI = Tc/2 TD = Tc/8
R = 0.08206 dm3.atm.mol-1.K-1
= 8.314 J.mol-1.K-1
Surface area of a cylinder = 2rh + 2r2

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CH4404 Process Technology 1 Page 1 of 6 Spring 2018

School of Natural Sciences

Department of Chemical Sciences

End of Semester Assessment

Module Code: CH4404

Module Title: Process Technology 1

Lecturer(s): Dr. Saeed Shirazian

Semester: Spring 2018

Duration of Exam: 2.5 hours

Grading Scheme: 70% Examination

1. There are three questions in this paper. Answer full questions.

Clearly define the following terms:

Q2. (c) continued

Process Technology 1 CH4404 Equation Sheet

Time Function Laplace Transform

(where a and b are constants associated with the input signal)

 4 t  t D (32 + (6t D / )) 4t D

Kp = 0.6K TI = Tc/2 TD = Tc/8

Surface area of a cylinder = 2rh + 2r2

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