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Pinch analysis and Mixed Integer Linear Programming (MILP) have been extensively studied for optimization of industrial processes addressing heat recovery, utility selection and sizing. Analysis of renewable utility integration, such as solar thermal or photovoltaics, introduces several obstacles for established methods: the time-dependency of resources, storage inertia and losses, and intrinsic non-linearities of the system performance are difficult to represent by linearized, time-invariant MILP equations. Moreover, waste heat recovery options such as heat pumping cannot be neglected as a potential competitor to solar heat. This work presents a set of multi-period MILP equations for solar technologies as well as a superstructure for optimization of heat pump cycles. Additionally, a methodology is proposed and applied to simultaneously optimize the process' refrigeration and renewable utility system using ɛ-constrained parametric optimization. The proposed methodology is illustrated on the basis of a dairy plant for which the different utility technologies are compared and evaluated based on economic and environmental criteria. It is illustrated that integration of solar energy can contribute to strongly reduce the environmental impact of the process (65–75% reduction in CO 2 equivalent emissions), but only in combination with heat recovery (27%) and an improved heat pump system (33%). Heat recovery and heat pump placement for industrial processes are hereby shown to reduce exergy destruction and total cost while improving system energy efficiency by means of thermo-economic optimization. The solutions show that investment in solar energy can be economically and environmentally attractive for industrial processes by considering the whole system and ensuring that solar energy is optimally integrated and utilized. [ABSTRACT FROM AUTHOR]

An optimization methodology based on Mixed Integer Linear Programming (MILP) has been developed for simultaneous optimization of water and energy (SOWE) in industrial processes. The superstructure integrates non-water process thermal streams and optimizes the consumption of water, while maximizing internal heat recovery to reduce thermal utility consumption. To address the complexity of water and energy stream distribution in pulp and paper processes, three features have been incorporated in the proposed SOWE method: (a) Non-Isothermal Mixing (NIM) has been considered through different locations to reduce the number of thermal streams and decrease the investment cost by avoiding unnecessary investment on heat exchangers; (b) the concept of restricted matches combined with water tanks has been added to the superstructure; and (c) the Integer-Cut Constraint technique has been combined with the MILP model to systematically generate a set of optimal solutions to support the decision-making for cost-effective configurations. The performance of the proposed improved MILP approach has been evaluated using several examples from the literature and applied to a Canadian softwood Kraft pulping mill as an industrial case study. The results indicate that this approach provides enhanced key performance indicators as compared to conceptual and non-linear complex mathematical optimization approaches. [ABSTRACT FROM AUTHOR]

This paper addresses the synthesis problem of non-isothermal water networks using a mathematical programming approach. A heat-integrated water network superstructure and its corresponding mixed integer nonlinear programming (MINLP) model is proposed for the synthesis of individual as well as interplant water networks. A new feature of the proposed model includes piping installation cost within the objective function minimising the total annual cost of the network. This introduces additional trade-offs between operating and investment costs that can impact a final network design. Three examples were solved in order to demonstrate the applicability and effectiveness of the proposed model and solution approach. The results show that additional saving in total annual cost can be achieved by enabling direct water integration between plants. Improved solutions were obtained compared to those reported in the literature considering freshwater and utilities consumption as well as total annual cost. [ABSTRACT FROM AUTHOR]