Análise e Simulação de Ciclos Térmicos Convencionais e Regenerativos para Cogeração de Bioenergia no Setor Sucroenergético
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Data
2019-01-22
Autores
Ursino, Welban Ricardo
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Neste estudo, realizou-se a análise da influência da pressão e da temperatura do vapor bem como da implementação de aquecedores regenerativos sobre a geração de bioenergia e a eficiência térmica (energética) em ciclos de cogeração no setor sucroenergético, considerando para priorização da geração de energia elétrica, consumo total do bagaço gerado no processo de produção de açúcar e álcool e moendas acionadas por motores elétricos. Para tanto, foram realizadas simulações dos ciclos de potência a vapor operando em diferentes condições de pressão e temperatura de vapor comumente empregadas no setor (pressão de 67 bar, em temperaturas de 490, 520 e 540°C e pressão de 100 bar à temperatura de 540°C) e temperatura da água de alimentação da caldeira variando entre 115 e 180°C, sendo a menor temperatura (115°C) aplicada em ciclos CEST (Condensing-Extraction Steam Turbine) convencional e as demais (140, 160 e 180°C) em ciclos CEST com pré-aquecedores regenerativos. Foram realizadas simulações para demandas de vapor pelo processo produtivo variando entre 380 e 460 kg/t de cana processada, em intervalos de 20 kg/t. As simulações foram baseadas em equações de conservação de massa e energia aplicadas ao sistema, as quais foram resolvidas usando-se o software Cycle-Tempo. Os resultados obtidos permitiram verificar que: (i) o aumento da temperatura e pressão de vapor proporciona um aumento na geração de energia e na eficiência energética do ciclo; (ii) a introdução de pré-aquecedores fechados de alta pressão em ciclos convencionais aumenta a geração de energia elétrica e a eficiência energética; (iii) a implementação de pré-aquecedores de baixa pressão em ciclos com pré-aquecedores de alta pressão não proporciona significativos acréscimos na geração de energia e na eficiência energética; (iv) o aumento de demanda de vapor pelo processo produtivo reduz a geração de energia elétrica e a eficiência energética; (v) a eficiência energética de Rankine é a mais adequada para representar a eficiência dos ciclos; (vi) o potencial de exportação de energia elétrica das unidades sucroenergéticas pode ser aumentado pelo uso de tecnologias mais eficientes de geração.
In this study, the influence of steam pressure and temperature as well as the implementation of regenerative heaters on the bioenergy generation and thermal (energetic) efficiency in cogeneration cycles in the sucroenergy sector was analyzed. For prioritization of electric power generation, it was considered total consumption of the bagasse generated in the sugar and alcohol production process and mills activated by electric motors. For this purpose, steam power cycle simulations were performed at different pressure and vapor temperature conditions commonly used in the industry (pressure of 67 bar, at temperatures of 490, 520 and 540°C and pressure of 100 bar at a temperature of 540°C) and boiler feed water temperature ranging from 115 to 180°C, the lowest temperature (115°C) applied in conventional Condensing-Extraction Steam Turbine cycles and the other (140, 160 and 180°C) in CEST cycles with regenerative preheaters. Simulations were carried out for steam demands from the production process, varying between 380 and 460 kg/t of processed cane, at 20 kg/t intervals. The simulations were based on mass and energy conservation equations applied to the system, which were solved using the Cycle-Tempo software. The obtained results allowed to verify that: (i) the increase of the temperature and vapor pressure provides an increase on the generation of energy and the energetic efficiency of the cycle; (ii) the introduction of closed high-pressure preheaters in conventional cycles increases both the generation of electrical energy and energetic efficiency; (iii) the implementation of low pressure preheaters in cycles with high pressure preheaters does not provide significant increases on the energy generation and on the energetic efficiency; (iv) the increase of steam demand by the production process reduces the generation of electric energy and the energetic efficiency; (v) the energetic efficiency of Rankine is the most adequate to represent the thermal of the cycles; (vi) the potential for the export of electricity from sugarcane plants can be increased by the use of more efficient generation technologies.
In this study, the influence of steam pressure and temperature as well as the implementation of regenerative heaters on the bioenergy generation and thermal (energetic) efficiency in cogeneration cycles in the sucroenergy sector was analyzed. For prioritization of electric power generation, it was considered total consumption of the bagasse generated in the sugar and alcohol production process and mills activated by electric motors. For this purpose, steam power cycle simulations were performed at different pressure and vapor temperature conditions commonly used in the industry (pressure of 67 bar, at temperatures of 490, 520 and 540°C and pressure of 100 bar at a temperature of 540°C) and boiler feed water temperature ranging from 115 to 180°C, the lowest temperature (115°C) applied in conventional Condensing-Extraction Steam Turbine cycles and the other (140, 160 and 180°C) in CEST cycles with regenerative preheaters. Simulations were carried out for steam demands from the production process, varying between 380 and 460 kg/t of processed cane, at 20 kg/t intervals. The simulations were based on mass and energy conservation equations applied to the system, which were solved using the Cycle-Tempo software. The obtained results allowed to verify that: (i) the increase of the temperature and vapor pressure provides an increase on the generation of energy and the energetic efficiency of the cycle; (ii) the introduction of closed high-pressure preheaters in conventional cycles increases both the generation of electrical energy and energetic efficiency; (iii) the implementation of low pressure preheaters in cycles with high pressure preheaters does not provide significant increases on the energy generation and on the energetic efficiency; (iv) the increase of steam demand by the production process reduces the generation of electric energy and the energetic efficiency; (v) the energetic efficiency of Rankine is the most adequate to represent the thermal of the cycles; (vi) the potential for the export of electricity from sugarcane plants can be increased by the use of more efficient generation technologies.
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Palavras-chave
Bagaço de cana-de-açúcar, Bioenergia, Cogeração, Ciclos convencionais e regenerativos, Eficiência térmica, Sugarcane bagasse, Bioenergy, Cogeneration, Conventional and regenerative cycles, Thermal efficiency