Maziar Kermani

An Improved Linear Programming Approach for Simultaneous Optimization of Water and Energy

An optimization method based on Mixed Integer Linear Programming (MILP) has been developed for simultaneous optimization of water and energy (SOWE) in industrial processes. The superstructure integrates process thermal streams and optimizes the consumption of water while maximizing internal heat recovery to reduce thermal utility consumption. In this paper, additional concepts have been implemented in the superstructure to target the issues of the pulp and paper processes. Non-Isothermal Mixing (NIM) has been considered at different locations in order to reduce the number of thermal streams and decrease the investment cost by avoiding unnecessary investment on heat exchangers. The concepts of restricted matches and water tanks have been added to the superstructure to adapt it to the pulp and paper case studies. The Integer-Cut Constraint (ICC) technique has been combined with the MILP model to generate systematically a set of optimal solutions to support the decision-making for cost-effective configurations.

A novel MILP approach for simultaneous optimization of water and energy: Application to a Canadian softwood Kraft pulping mill

Abstract 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.

Synthesis of single and interplant non-isothermal water networks

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.

General Superstructure Synthesis and Bi-level Solution Strategy for Industrial Heat Pumping

Industrial waste heat is abundant and represents significant energy inefficiency for many processes. With increasing emphasis on improving industrial energy efficiency, heat pump systems (including refrigeration) offer a solution by valorizing low-temperature waste heat. Optimization of industrial heat pump systems attempts to reach the cost-optimal configuration of equipment (compressors, evaporators, etc.), the sizes, operating conditions (pressures levels, temperatures), and working fluids which can be expressed as a mixed integer nonlinear programming (MINLP) problem. This work presents a general MINLP heat pump superstructure which incorporates enhanced features such as fluid after-cooling (after compression) and inter-cooling (during multi-stage expansion) while considering pressure levels and fluid selection. The MINLP is solved using a bi-level mathematical approach to explore a large solution space. The superstructure was applied to a set of MILP literature cases and it is shown that the MILP sub-problem performs well; furthermore, the full MINLP superstructure achieves up to 10% improvement compared to the literature optimal scenario with respect to the total annualized cost.

A Hybrid Methodology for Combined Interplant Heat, Water, and Power Integration

Abstract The growing desire to improve resource efficiency and environmental impact of industrial processes is directly linked to optimal management of heat, mass and power flows. The concept of industrial symbiosis tackles this issue by proposing interplant heat recovery and resource transfer which can bring economical and environmental benefits to each party. A comprehensive methodology is required which can easily be incorporated in the planning of industrial clusters. Therefore, a generic hybrid mixed integer linear programming superstructure has been developed to address simultaneous heat, water, and power optimization in interplant operations. Additional concepts are included in the previously-proposed water network superstructure (Kermani et al., 2017) to account for the issues related to interplant heat and mass exchange. A cold utility superstructure is included in the water network while a steam network superstructure is modified to better represent the feedwater heaters and heat recovery opportunities. The proposed methodology is applied to an industrial case study. Results exhibit a large potential for synergies among industrial sites, even in disparate sectors, and emphasize the importance of a generic approach.

Techno-Economic and Environmental Optimization of Palm-based Biorefineries in the Brazilian Context, 27th European Symposium on Computer Aided Process Engineering

Abstract Due to the global increase in energy consumption, greenhouse gas emissions, and the depletion of fossil energy resources, the research presented here is focused on finding economically and environmentally competitive renewable energy resources. Fuel production from biomass is an attractive solution in this regard. Competing interests between food and energy have yielded increased interest in lignocellulosic biomass (LGB) as a feedstock. Processes such as biodiesel production from palm oil generate large volumes of LGB residues. Valorization of these residues through biorefineries may bring economic and environmental benefits through substitution of fossil fuels and such options must be studied in a systematic manner. The goal of this research is to propose a methodology for economic and environmental analysis of such biorefineries. A case study of a palm-based biorefinery in Brazil is used to illustrate this. Results indicate that multi-product processes can yield significant cost and environmental benefits.