Proportional, Integral and Derivative Control Strategy of Triethylene Glycol Recovery Regenerator for Optimum Natural Gas Dehydration Process

Abstract

The research considered the application of the conservation principle of mass and energy balance in the development of the dynamic model of a triethylene glycol (TEG) recovery regenerator. The mass and energy balance was performed at the feed point (inlet) and the bottom (outlet) of the regenerator. The natural gas TEG dehydration plant was designed using HYSYS while the control analysis was performed at the feed point and bottom (reboiler) of the regenerator.The behaviour of the process was analyzed in terms of an open loop with disturbance and a closed loop for both manual and automated proportional, integral and derivative (PID) control configurations using Simulink. The effect of the process variable (temperature) was measured using a thermocouple configured in the closed-loop system. The result of process behaviour for an open loop system with a disturbance at the feed point, and reboiler section as a function of temperature with time indicates a high level of process instability. While the use of manual tuning of various
PID controllers. Parameters or gains in the closed loop system for temperature control at the feed point and reboiler section of the regenerator also showed a high degree of system or processinstability as indicated in the temperature and time profile behaviour, where the system failed to attain its stability even at 10seconds. However, the use of automated controller gains of (1.438,-2.733, and 0.1864) and (0.1773, 0.1665, and 0.04408) for K௉,Kூ and K஽ at the feed point and reboiler section of the regenerator showed that the system attained its stability at 10seconds and 2.5seconds after a tuning of 402.5 times and 205.3 times respectively and at a set point temperature of 80°c for the regenerator feed point and 2040C for the regenerator reboiler section. The above analysis clearly shows that for optimum TEG recovery during the dehydration process, the use of an automated PID controller gives a better performance characteristic compared to manual tuning and ensures the system or process attains its stability within the shortest possible time.