Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
ON THE THERMOECONOMIC APPROACHES FOR FUEL AND WASTES ALLOCATION IN A COGENERATION PLANT: ARBITRARINESS AND COMPLEXITIES
Submission Author:
Rodrigo Guedes dos Santos , ES
Co-Authors:
Lucas Rodrigues Loyola, Vitor Buson de Paula, Audrey Novelli, Carlos Eduardo Silva Abreu, Igor Belisario, Rodrigo Guedes dos Santos, José Joaquim Conceição Soares Santos
Presenter: Lucas Rodrigues Loyola
doi://10.26678/ABCM.COBEM2021.COB2021-2012
Abstract
Thermoeconomic approaches connect Thermodynamics and Economics concepts, usually used for diagnosis, optimization and, mainly, cost allocation to the products of thermal plants. Traditionally, exergy of the external fuels or monetary cost of fuel and capital are allocated. However, in the last year, the allocation of the overall fuel consumption and CO2 emission have been gained importance, mainly to calculate the specific fuel consumption and the specific CO2 emission due to the production of each intermediate and final products. For this purpose, several conventional thermoeconomic approaches have been adapted and modern ones were developed. Some methodologies use total exergy to define productive structure and other ones use disaggregated exergy. There are methodologies based on physical diagram, using the same physical flows presented at flow sheet, other ones uses productive diagrams based on subsystem fuel and products connected by means of fictitious units (junctions and bifurcations), and the ones that uses a comprehensive diagram, a mix of physical and productive diagrams, without fictitious units. Bearing this in mind, this work aims at comparing different thermoeconomic approaches for fuel and waste allocation in a gas turbine cogeneration plant, in order to evaluate the arbitrariness and complexity involved. Thus, the chosen plant allows the treatment of dissipative component and waste, which are the main challenge of the thermoeconomic approaches. The methodologies utilized in this work are divided into three groups according to the kind of diagram used to represent the cost formation process: (i) three of them use the physical diagram; and (ii) five ones use the productive structure; (iii) four ones use the comprehensive diagram in the system. This way, this work shows that. No matter the thermoeconomic diagram used, i.e., physical, productive or comprehensive, total exergy is unable to treat dissipative component and waste, without some level or arbitrariness. On the other hand, although the involved complexity, the comprehensive diagram, which combines physical and productive flows, avoids the arbitrariness related to the isolation of the dissipative component, remaining some level of arbitrariness in the treatment of wastes. However, although the involved complexity, the exergy disaggregation into enthalpic and entropic components (H&S Model) allows a systematic procedure for fuel and waste allocation, no matter using productive or the more complex comprehensive diagram, since the H&S Model allows a consistent relationship, in the process of cost formation, between the subsystems that compose the thermal system of the plant and the environment (atmosphere).
Keywords
thermoeconomic approaches, wastes allocation, fuel allocation, Cost Allocation, disaggregated exergy
