Optimization with Integrated Offline Parametric Optimization of Detailed Process Model of an Interceptor Unit for Water Network Synthesis and Retrofit Design

Petroleum refineries is a prime example of industrial plants that demand high
quantities of water for process consumption and generate volumes of highly
contaminated industrial eflluents and wastewaters. Scarcity of freshwater resources
and increasingly stringent environmental regulations on industrial effluents have
motivated refineries to develop water reuse technologies for sustainability of plant
operations. The technology concept can be characterized into three (3) strategies:
reuse, regeneration, and recycle (W3R). The major contribution of this work is to
consider the design of alternative refinery water network structures that incorporate
the detailed design of wastewater treatment technology (or interceptor) in an
optimization-based modeling framework as an offline parameter optimization
problem. For this purpose, a source-interceptor -sink superstructure representation is
adopted that embeds many feasibly possible alternative water network
configurations. A mixed-integer nonlinear programming (MINLP) optimization
model is formulated based on the superstructure with the objective of minimizing
freshwater import, wastewater generation, piping interconnections, and the total cost
of installing and operating the treatment technology. The parametric optimization
problem comprising of material balances and the detailed phenomena model for
interceptor, specifically for a single-stage hollow fiber reverse osmosis (HFRO)
membrane module, is incorporated in the overall MINLP framework. The modeling
approach is developed in conjunction with its implementation into general algebraic
modeling system (GAMS), using data of a real operating refinery situation. The
model is solved iteratively by branch and reduce optimization navigator (BARON),
resulting in freshwater consumption requirements to be 296.2 m3 /h at the optimal
refinery water network structure and operating conditions, which accounts for nearly
61% of water recovery compared to current operating requirements (before the
integration and retrofit initiatives based on W3R).