Multilevel strategies for the retrofit of a large industrial water system

Abstract

This paper presents two multilevel strategies for retrofitting a large-scale water system, which integrates water-using operations and wastewater treatment units in different production sections within the same network. The proposed strategies are based on temporal decomposition. They can be applied to production processes with repeating batch/semi-continuous operations, and daily changes in production schedules over a working week. This approach uses a mixed-integer nonlinear programming (MINLP) model for water re-use and regeneration re-use in batch and semi-continuous processes (Tokos and Novak Pintaric, 2009). In the first step, both strategies perform simultaneous retrofit of an integrated water system for each working day, by identifying daily re-use and regeneration re-use connections among water consumers in all sections. At the second level, within the first strategy, the design of an integrated water system is performed over the entire working week for each section by fixing the identified daily matches between sections. In the second strategy, the freshwater upper and wastewater lower bounds of the integrated processes are modified, and retrofit is performed for each production section over the entire working week. The proposed strategies are applied to an industrial case study within a Brewery. © 2011 Elsevier B.V.