DYNAMIC SIMULATION AND COMPOSITION CONTROL IN A 10 L MIXING TANK

Abstract

The open loop experiment of composition dynamic in a 10 L mixing tank has been successfully done in
laboratory. A 10 L tank was designed for mixing of water (as a stream-1) and salt solution (as a
stream-2 with salt concentration, c2 constant). An electric stirrer was employed to obtain uniform
composition in tank. In order to keep the liquid volume constant, the system was designed overflow. In
this work, 2 composition control configurations have been proposed; they are Alternative-1 and
Alternative-2. For Alternative-1, the volumetric-rate of stream-1 was chosen as a manipulated
variable, while the volumetric-rate of stream-2 was chosen as a manipulated variable for Alternative-
2. The composition control parameters for both alternatives have been tuned experimentally. The
volumetric-rate of manipulated variable was changed based on step function. The outlet stream’s
composition response (c3) to a change in the input volumetric-rate has been investigated. This
experiment gave Proportional Integral Derivative (PID) control parameters. The gain controllers Kc
[cm6/(gr.sec)] for Alternative-1 and Alternative-2 are -34200 and 40459 respectively. Integral time
constant ( t
I) and Derivative time constant (tD) for both alternatives are the same, i.e. t
I = 16 second,
and tD = 4 second. Furthermore, closed loop dynamic simulation using computer programming was
also done to evaluate the resulted tuning parameters. The developed mathematical model of
composition control system in a mixing tank was solved numerically. Such mathematical model was
rigorously examined in Scilab software environment. The results showed that closed loop responses in
PID control were faster than those in P and PI controls.