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 is chosen as a manipulated variable, while the volumetric-rate of stream-2 is 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 research 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 ( I) and Derivative time constant (D) for both alternatives are the same, i.e.  I = 16 second, and D = 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. As can be seen from our closed loop simulation, closed loop responses in PID control were faster than those in P and PI controls.