MILP synthesis of separation processes for waste oil-in-water emulsions treatment

This paper presents a novel synthesis method for designing integrated processes for oil-in-water (O/W) emulsions treatment. General superstructure involving alternative separation technologies is developed and modelled as a mixed integer linear programming (MILP) model for maximum annual profit. Separation processes in the superstructure are divided into three main sections of which the pretreatment and final treatment are limited to the selection of one alternative (or bypass) only, while within the intermediate section various combinations of different technologies in series can be selected. Integrated processes composed of selected separation techniques for given ranges of input chemical oxygen demand (COD) can be proposed by applying parametric analyses within the superstructure approach. This approach has been applied to an existing industrial case study for deriving optimal combinations of technologies for treating diverse oil-inwater emulsions within the range of input COD values between 1000 mg.L-1 and 145000 mg.L-1. The optimal solution represents a flexible and profitable process for reducing the COD values below maximal allowable limits for discharging effluent into surface water.