Unit consumptions of raw materials reveal distinctly a nonlinear relationship vs unit loads in chemical processes.To obtain more practically optimal solutions for production planning in chemical enterprises

piecewise linear function and polynomial function were used to model nonlinear unit consumptions.The optimal solutions obtained by the two approaches were compared in case studies.The results indicated that the piecewise linear function approach was easy to model nonlinear unit consumptions with a higher accuracy without regressing any parameter

and the related model could be solved quickly for a medium size problem.Meanwhile

the piecewise linear function approach could simultaneously handle nonlinearities of multi raw materials in a unit without adding any new integer variable.Comparatively

the quadratic function approach was lack of these advantages.The piecewise linear function approach has been implemented in the graphical modeling system for optimal production planning of chemical companies (GIOCIMS)

and the system is used in Baling Branch Company Sinopec.