INNOVATIVE STRATEGIES TO OPTIMIZE WATER RESOURCES

The focus on the rationalisation of the industrial consumption of energy and water has become central worldwide in the academic, governmental and industrial debate over the last 30 years. It is clear that water scarcity will become more and more critical worldwide, and that the increasing energy demand involved by the industrialisation of developing countries will provide a substantial contribution to this phenomena. However, Industry does not make many efforts to reduce freshwater demand, mainly for the low profitability of water optimisation projects, but also for practical issues that the operators may face when pursuing the water optimisation goal in existing factories not originally designed with this target in mind. The rationalisation of freshwater supply to industrial complexes involves the integrated application of different methodologies in the areas of Data Validation and Reconciliation, Pinch Techniques and Optimisation Methods. This study aims at testing the effectiveness of State of the Art methodologies for actual industrial cases to propose solutions to the potential technological gaps and limitations which might hinder their application. To pursue this goal, three practical exercises focused on actual industrial cases have been studied, the first two concerning a retrofit case and the last one a new design case: • The first exercise covers an existing industrial complex in the food industry (maize milling factory producing starch, sugars and co-products), where the problem of flowrates data reconciliation have been deepened. In this context, the issues related to the lack of measurements and fluctuating water (unavailability of direct analysis of water content in feedstock and product streams) have been addressed. A suitably modified data reconciliation approach, able to fit these specific requirements have been developed. • The second exercise consists in a Water Pinch Study aimed at targeting the potential freshwater saving in the base case and assuming the Reverse Osmosis treatment of a portion of the streams currently fed to the wastewater treatment facilities. • The third exercise covers the new design of a Reverse Osmosis Network (RON), where the problem related to the identification of the optimal arrangements of RO modules considering the goals of the treatment, the economics and the specific technical constraints of the system and RO modules have been studied. In this context, a numerical modelling algorithm suitably modified to reach robust and reliable solutions have been developed. The meaningful results obtained during the research activity can be summarized as follows: • the inclusion of statistical fluctuations in the composition of water in products, obtained by modifying the usual reconciliation algorithms; • the estimate the water savings obtainable, through the application of a well-established water pinch methodology; • the identification of the optimal arrangement of a RON (Process Synthesis problem) which involved the use of a modified Simulated Annealing algorithm.