Temperature Control of An Open-loop Unstable Ethylene to Butene-1 Dimerization Reactor by Emad Ali & Khalid Al-humaizi Chemical Engineering Department King Saud University

Outline of the Presentation Objectives and motivation The process and its model Control objectives Controller design Closed-loop simulations Conclusions

Objectives and Motivation To determine the favorable plant operating conditions. To study the dynamics of the process To stabilize the plant operation via good controller design

The process and its model The process model Nonlinear ODE’s: dx/dt = f(x,u,t) Operating condition Bifurcation analysis: 95% conversion 69% Yield T = 67 o C

Open-loop Simulation

Control Objectives Stabilize the reactor temperature Maintain the favorable conversion and yield conditions

Controller Design Controlled variables: Reactor temperature C 4 concentration Manipulated variables: Coolant Flow Rate: W c Ethylene flow rate: F e Recycle ratio:  Catalyst conc.: Ak Feed Temperature: T f

Steady State Disturbance Analysis

PI Controller Tuning Tuning is important due to instability : –Continuous Cycling Method –Model-Based Methods

SISO Closed-loop simulation +4 o C step change in T c

SISO Closed-loop Simulation +6 o C step change in T c

MIMO Closed-loop Simulation +6 o C step change in T c T W c C 4 F e

Conclusions The favorable operating condition is unstable. The SISO PI control loop can stabilize the reactor to some extent. The MIMO PI control loop demonstrated trade-off between stability and performance.