Simultaneous Energy and Water Minimization Applied to Sugar Process Production

In this work, a procedure that can simultaneously minimize the fresh water consumption and heat usage in a process plant is proposed. This method begins with the application of mass integration followed by heat integration to target and design a network with minimum usage of fresh water and heat utility usage. During the past decade, considerable design techniques have been developed to minimize the heat and mass (mainly focused on water) consumption simultaneously. Focusing on reducing the two resources separately may result in extra energy and heat exchanger being designed unnecessarily. Due to this reason, various academic and industrial studies had been carried out to respond to this need, and process integration techniques have been successfully applied to minimize heat and mass consumption. The water streams are resources that often are subjected to not only the constraints of concentration levels, but also the temperature levels. When a water-using process requires hot water for the operation, water stream of the operation involves the changes of concentration levels through the mass transfer between process stream(s) and water stream(s), as well as the changes of temperature levels resulting from heat transfer within the process. Under these circumstances, both contaminant and temperature conditions need to be considered simultaneously, if any attempts for minimising water or energy consumptions for the site are made. On the other hand, the synthesis of heat recovery systems maximises potential recovery from waste heat, and identify the amount of energy to be exchanged between hot and cold water streams, and their network configuration. Therefore, design tasks in the study of simultaneous water and energy minimisation are to identify targets for the design, freshwater usage, energy consumption and wastewater generation, as well as a network design to achieve the targets, water reuse network and heat exchanger network. The developed design method aims to exploit water reuse potentials between water-using operations, and simultaneously to minimise any potential lost of energy resulted from water disposal. Systematic approach was developed and tested with the water minimization project in a sugar plant.