On the Allocation of Residues Cost using Conventional and Comprehensive Thermoeconomic Diagrams

In a productive process, the achievement of products occurs simultaneously with residues generation. Environmental impact of residues is an important issue in energy systems analysis due to environmental regulations and sustainability assessment. Many waste treatment methodologies have been proposed and applied in thermoeconomics. However, this is a complex problem and the solution depends on the residue nature and its formation process. Most conventional methodologies are based on productive diagrams, using productive flows only, and allocate the residues cost among the productive equipment. This work surveys the main conventional methodologies for treatment of waste and presents an improved/updated methodology based on a comprehensive diagram, in which both physical and productive flows are represented and their flows cost are assessed and the subsystems are connected using the same physical flows presented in the flowsheet of the plant. Both the CGAM system and a combined cycle are analyzed. Comparisons are made with literature results, considering the same case studies. The presented methodology obtains consistent results from the point of view of the cost allocation in thermoeconomics. The novelty of this updated approach concerns how the residue cost is allocated in the comprehensive diagram: it is reinternalized in the internal loop of physical flows, instead of in the productive unit. It represents advantages since the equipment product/fuel ratio index is not affected, which is beneficial for thermoeconomic diagnosis application.