Global Optimization in Property-Based Interplant Water Integration Eusiel Rubio-Castro Dept. of Chemical Engineering, Universidad Michoacana de San Nicola ´s de Hidalgo, Morelia, Michoaca ´n 58060, Me ´xico Dept. of Chemical and Biological Sciences, Universidad Auto ´noma de Sinaloa, Culiaca ´n, Sinaloa 80000, Me ´xico Jose ´ Marı ´a Ponce-Ortega and Medardo Serna-Gonza ´lez Dept. of Chemical Engineering, Universidad Michoacana de San Nicola ´s de Hidalgo, Morelia, Michoaca ´n 58060, Me ´xico Mahmoud M. El-Halwagi Dept. of Chemical Engineering, Texas A&M University, College Station, TX 77843 Dept. of Chemical and Materials Engineering, King Abdulaziz University, Jeddah, Saudi Arabia Viet Pham Dept. of Chemical Engineering, Texas A&M University, College Station, TX 77843 DOI 10.1002/aic.13874 Published online in Wiley Online Library (wileyonlinelibrary.com). This article presents a new global optimization method for the interplant water integration based on properties to characterize streams with numerous components. The problem is formulated as an mixed-integer non-linear programming (MINLP) model based on a superstructure that involves all possible options of interest (i.e., reuse and recycle in the same and to other plants and a set of shared treatment units). This formulation exhibits multiple local minima, and to overcome this problem, this article proposes effective branching rules in addition to two new reformulations for the upper bound (integer feasible solution) and the lower limit (relaxed solution), which are incorporated into a spatial branch and bound procedure to handle the bilinear terms in the model. The objective consists in finding the configuration with the minimum total annual cost. Results show that the global optimal solution (involving significant reductions in the fresh water consumption) is reached in few iterations and short central processing unit (CPU) time. V V C 2012 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2012 Keywords: interplant water integration, deterministic global optimization, property integration, eco-industrial parks, bilinear terms Introduction Nowadays, the current situation in the industry around the world has demanded the development of efficient strategies for reducing simultaneously the environmental impact and the associated costs to yield sustainable industrial processes. In this regard, water is probably the most intensively used resource in the process industries and, in recent years, sev- eral works have addressed the problem for the efficient use of water considering the recycle, reuse, and regeneration for this important resource in single industrial facilities (i.e., the single plant water integration). The review articles by Baga- jewicz, 1 Dunn and El-Halwagi, 2 and Foo 3 summarize the methodologies reported for the single plant water integration. Because significant environmental and economic benefits have been observed by implementing water integration in indi- vidual plants, this approach has been extended to study the water integration between multiple plants in eco-industrial parks (EIP) or interplant water integration. In this regard, the interplant water integration represents additional savings in the fresh water consumption and additional reductions in the overall wastewater discharged to the environment, in addition to the economic benefits for the use of a shared treatment sys- tem respect to the single plant integration. The reported methodologies for interplant water integra- tion can be classified as graphical, algebraic, and mathemati- cal programming-based approaches. The articles by Olesen and Polley 4 and Spriggs et al. 5 address the interplant water integration using graphical methods based on the water pinch technology. On the other hand, the articles by Chew et al., 6 Foo, 7 Bandyopadhyay et al., 8 Chew et al. 9,10 present alge- braic approaches for targeting minimum fresh water and waste flow rates for interplant water networks. The major advantage of the graphical and algebraic methods is that they provide targets for water integration before the Correspondence concerning this article should be addressed to J. M. Ponce-Ortega at jmponce@umich.mx. V V C 2012 American Institute of Chemical Engineers AIChE Journal 1 2012 Vol. 00, No. 0