The judicious exploitation of the inherent optimization capabilities of the Spectral-Projected-Gradient method (SPG) is proposed. SPG was implemented in order to achieve efficiency. The novel adjustments of the standard SPG algorithm showed that the parallel approach proves to be useful for optimization problems related to process systems engineering. Efficiency was achieved without having to relax the problems because the original model solutions were obtained in reasonable time. (c) 2015 Elsevier Ltd. All rights reserved.