An MILP model for simultaneous mass allocation and heat exchange networks design with regeneration units

Abstract

Abstract Environmental standards impose strict specifications for waste treatments to be able to discharge them. These regulations are more and more constraining because sustainability and pollution prevention place high in political agendas. Consequently, waste management can represent a considerable and unavoidable financial burden for companies. It can require heavy investments and account significant part of annual operating costs. Therefore, it can be economically interesting to reuse waste effluents generated by industrial processes and use them as resources to supply heat and matter to the process. But, it still may be necessary to treat parts of these waste effluents to either recycle them more easily or comply with environmental standards to discharge them. In this perspective, this paper proposes a new mixed integer linear programming (MILP) model to design economically optimal mass allocation and heat exchangers networks (MAHEN) including regeneration technologies. This model allows evaluating their impact on the mass and heat integration of a process. For this purpose, a novel approach is introduced to represent any type of regeneration units with a generic formulation. This formulation is added to the MILP model presented by Ghazouani et al. (2016). A phenol production case is used to illustrate the model potentials. In this case study, the purpose is recovering wastewaters polluted with phenol. The results show that the new model of treatment units helps to generate applicable results and, in this case, to find MAHEN structure that allows being independent from any fresh water source while reducing heat requirements, and the wastes generated by the process, making it more cost-efficient. The main limitation of the linear formulation of regeneration unitsḿodel is the decoupling between the inlet and outlet streams properties. However, this type of model allows understanding the influence of regeneration technologies on the mass and heat integration of processes.