During chemical process design

the margin of manipulated variables must be determined not only for the possible change of process and equipment condition but also for the dynamic control of process control system

but its size cannot be too large in consideration of equipment cost. Now advanced process control

represented by predictive control provides a new method to improve process control performance. It is necessary to analyze the relationship between manipulation margin and control performance under advanced process control and find out the process design scheme to improve process control performance significantly at a lower cost of manipulation margin. So the mathematical description of solving the manipulation margin of chemical process under advanced process control is established. In advanced process control the linear model predictive control is used based on linear state space model

which is obtained through linearization on the steady nominal operating point

and the possible disturbances are also involved

then the problem is solved through dynamic optimization. The air flow rate margin of FCC regenerator was calculated as an example. When prediction horizon of predictive control was changed

different control performances were obtained and those corresponding manipulation margins were calculated. So the relationship between control performance and manipulation margin was found out.