Integration of nonconvexities/nonlinearities in wastewater treatment engineering design into production cost functions for ethylene

Abstract

The primary objective of this study was to integrate the engineering design relationships of wastewater treatment into production cost functions for ethylene. The integration of these nonlinear/nonconvex functions was accomplished by adding wastewater treatment constraints to a mathematical programming model for ethylene. Ethylene production costs as a function of allowed BOD discharges were computed by an adaptation of the "cutting-plane" method. The nonconvexities in wastewater treatment gave rise to mini-valley, mini-peak and plateau sections along the generally U-shaped marginal cost curve. Including the nonconvexities in production process design in addition to those considered would be..