Because of various uncertainties in a real chemical process

it is necessary to add enough margins on design variables to let the operating point be within the boundaries of process constraints during process design.According to first-order sensitivity analysis of process steady-state optimal design

local margins added on design variables result in that there are boundary distances on process constraints

and the maximum potential economic benefits which can be obtained from operation optimization of manipulated variables are determined by the boundary distances of active constraints.Therefore

the potential economic benefits derived from operation optimization can be used to evaluate the whole margin of the device.The potential economic benefits through operation optimization were used to evaluate the whole margin of FCCU

and a dynamic optimization approach for whole margin division was presented.The whole margin was divided into control margin for ensuring controllability and process margin for realizing economic benefits of the device.Through the analysis of the relationship between local margins of design variables and the whole margin of the device

the bottlenecks of process design could be found.