Simulação e avaliação termodinâmica de configurações de sistemas de cogeração a vapor para recuperação energética dos gases exaustos dos fornos de uma carboquímica
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Data
2024-08-30
Autores
Quintão, Alexsander Luíz
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Universidade Federal do Espírito Santo
Resumo
Energy efficiency plays a crucial role in the transition to more sustainable energy sources and in the decarbonization of industries. Within this context, the recovery of residual energy from processes stands out as a strategy, as is the case of the carbochemical plant, which is the subject of this study, where the calcination furnaces release exhaust gases containing thermal and chemical energy. These gases, originating from six furnaces, have a total flow rate of 1.36 kg/s at 800°C, with a volumetric composition of 26% H2, 4.2% CH4, and 5% CO, among other gases, resulting in a total energy potential of 8.30 MW. of which 1.63 MW is thermal and 6.67 MW is chemical. This study aims to analyze cogeneration system configurations based on steam cycles for this energy recovery, aiming to heat the thermal oil of the process, in addition to generating electricity. To this end, four configurations were simulated based on an example from Norway, using the IPSEpro software, followed by evaluation based on the first and second laws of thermodynamics to assess their performance and identify opportunities for future optimizations. The results indicated that, in addition to providing useful heat of 70 kW for heating the oil, it is possi-ble to obtain an electrical power of up to 2.654 MW. The energy and exergy efficiencies of the steam cycles reach up to 43.35% and 80.45%, respectively, while the system as a whole achieves up to 32.8% and 32.03% energy and exergy efficiencies, respectively. The exergy analysis revealed opportunities to improve various processes, with the greatest exergy des tructions occurring in the combustion chambers and boilers, in addition to the recoverable heat in the exhaust gases from the boilers. Although the environmental assessment was not the main objective of the study, qualitatively, it was observed that there is a drastic reduction in the temperature of the gases currently released into the atmosphere, as well as the combustion of combustible elements present, mainly methane, drastically reducing thermal and chemical pollution. Furthermore, quantitatively, by generating electricity and thus reducing the demand on the power grid, more than 3,234 tons/year of CO₂ emissions can be avoided. These indicators, as well as the thermodynamic evaluation of these four simulated configurations, demonstrate the significant theoretical potential for recovering this residual energy, which brings substantial benefits in terms of both effici-ency and reduction of environmental impacts. This potential also suggests the need for further studies for other assessments, particularly regarding economic viability, especially if the project is to be enabled for integration into a carbon market.
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Palavras-chave
Energia residual , Eficiência energética , Análise exergética