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A liquid-phase reversible reaction, A~ B, takes place
Chapter 15, Problem 15.8(choose chapter or problem)
A liquid-phase reversible reaction, A~ B, takes place isothermally in the continuous stirred-tank reactor shown in Fig. E15.8. The inlet stream does not contain any B. An overflow line maintains constant holdup in the reactor. The reaction rate for the disappearance of A is given by [ moles of A reacting] rA[=] -----,--.-----,-----,-----------,---.:::. (tlme) (volume) The control objective is to control exit concentration cs by manipulating volumetric flow rate, q. The chief disturbance variable is feed concentration cAi It can be measured on-line, but the exit stream compositions cannot. The control valve and sensor-transmitter have negligible dynamics and positive steady-state gains. Q Exercises 287 Figure E15.8 (a) Design a feedforward controller based on an unsteadystate analysis. (b) If the exit concentration cs could be measured and used for feedback control, should this feedback controller be reverse- or direct-acting? Justify your answer
Questions & Answers
QUESTION:
A liquid-phase reversible reaction, A~ B, takes place isothermally in the continuous stirred-tank reactor shown in Fig. E15.8. The inlet stream does not contain any B. An overflow line maintains constant holdup in the reactor. The reaction rate for the disappearance of A is given by [ moles of A reacting] rA[=] -----,--.-----,-----,-----------,---.:::. (tlme) (volume) The control objective is to control exit concentration cs by manipulating volumetric flow rate, q. The chief disturbance variable is feed concentration cAi It can be measured on-line, but the exit stream compositions cannot. The control valve and sensor-transmitter have negligible dynamics and positive steady-state gains. Q Exercises 287 Figure E15.8 (a) Design a feedforward controller based on an unsteadystate analysis. (b) If the exit concentration cs could be measured and used for feedback control, should this feedback controller be reverse- or direct-acting? Justify your answer
ANSWER:Step 1 of 5
(a) A dynamic model will be developed based on the following assumptions:
(i) Perfect amalgamation of concentration
(ii) Isothermal operation must be considered
(iii) Constant operation must be considered
Refer Figure E15.8 component balances are written as below,
The feed concentration is represented by 
Volumetric flow rate is represented by 
The exit concentration is represented by 
Subscript A and B represent a liquid-phase reversible reaction.