| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 3.53 MB | Adobe PDF |
Advisor(s)
Abstract(s)
No ano 2010, a União Europeia desperdiçou 43% da energia produzida para os setores de energia e indústria, sob a forma de calor. Motivados pela recuperação da crise económica e pelo crescimento sustentável, a recuperação do excesso de calor tornou-se um objetivo importante no aumento da eficiência energética.
Neste trabalho foi desenvolvido um estudo às alternativas de recuperação do excesso de calor numa unidade de polietileno de baixa densidade. No reciclo desta unidade, constituído por 66 t/h de etileno a 310 °C e 280 bar, distribuído por duas linhas de produção, existe um total de 9,3 MW de energia a ser desperdiçada para o meio ambiente, por intermédio de um aeroarrefecedor, que reduz essa temperatura para cerca de 130°C.
Foram analisados, como alternativas ao aeroarrefecedor, ciclos de produção de eletricidade (ciclo Rankine e ciclo Kalina), ciclo de produção de frio (refrigeração por absorção de LiBr/água) e produção de vapor por permuta de calor, através do simulador Aspen HYSYS®.
No ciclo Rankine avaliou-se o desempenho de 22 fluidos, concluindo-se que os hidrocarbonetos seriam fluidos de Rankine válidos, tendo o pentano uma eficiência de 18,3%, a funcionar entre 1,4 e 33 bar. O ciclo Kalina teve um desempenho máximo de 19,9%, com amoníaco a 90%, a funcionar entre 13 e 113 bar. As necessidades de vapor a baixa pressão podem ser totalmente satisfeitas com permuta de calor com o etileno a 310°C e ainda 99,7% da água quente pode ser produzida com etileno a 130°C.
A produção de 4,5 MW de água fria por absorção de LiBr/água consegue satisfazer as necessidades totais do processo, usando-se entre um a três aparelhos. Para a temperatura inicial de 310 °C, é possível satisfazer as necessidades de frio com 32,3 t/h de etileno em sistemas de efeito duplo a vapor de 8 bar, 46,4 t/h em sistemas de efeito simples a vapor de 1 bar e 41,7 t/h em sistemas de efeito simples a água quente a 90°C.
O custo de capital estimado para investir no ciclo Rankine foi de 9 milhões de euros, no ciclo de absorção foi entre 8 e 8,7 milhões e na produção de vapor foi de 4,4 milhões. Os períodos de retorno foram de 3 a 4 anos para a absorção e 7 para a produção de vapor, finalizando-se com um VAL de mais de 16 milhões de euros para a absorção e 2,4 milhões para a produção de vapor, considerando um horizonte de projeto de 15 anos com uma TIR de 10%. O ciclo Rankine não obteve lucros ao fim dos 15 anos para este projeto em particular.
In 2010, the European Union wasted 43% of produced energy under the form of heat, in power and industry sectors. Leveraged by the retrieval of the economical crisis and sustainable growth, recovery of waste heat has been established as an important goal to the improvement on energy efficiency. In this work, it was studied the alternatives to recovery of excess heat from a low density polyethylene unit. There is a total of 9.3 MW (31.7 million BTU/h) of recoverable waste energy from an ethylene recycling stream, at 280 bar (4 060 psi), cooled from 310°C (590°F) to 130°C (266°F) through an air cooler. Two power cycles (Rankine and Kalina), a cooling cycle (LiBr/water absorption refrigeration system) and heat exchange to produce steam have all been analysed as alternatives to the air cooler, via simulations on Aspen HYSYS®. The performance of 22 potential Rankine fluids was evaluated, being concluded that the hydrocarbons could be suitable Rankine fluids, with pentane having a performance of 18.3%, working in a range of 1.4 to 33 bar (20 to 479 psi). Kalina cycle had a performance of 19.9%, with 90% ammonia, working from 13 to 113 bar (188.5 to 1 639 psi). The need for low pressure steam can be completely satisfied by heat exchanging with ethylene at 310°C (590°F), while 99.7% of hot water can be produced by heat exchanging with ethylene at 130°C (266°F). The production of 4.5 MW (15.5 million BTU/h) of chilled water by an absorption refrigeration system can satisfy all the process needs, using up to three chillers. For an initial temperature of 310°C (590°F), the needs are fulfilled using 32.3 t/h (71,200 lb/h) of ethylene to an 8 bar (114 psi) steam powered double effect system, 46.4 t/h (102,300 lb/h) to a 1 bar (14.5 psi) steam powered single effect system and 41.7 t/h (91,900 lb/h) to a hot water (90°C, 194°F) powered single effect system. Total investment costs were estimated on 9 million € for a Rankine cycle, up to 8.7 million € for an absorption refrigeration cycle and 4.4 millions for low pressure steam production heat exchange. The absorption cycle returns its investment in 3 to 4 years and the steam production heat exchange takes 7 years to profit, resulting in a net worth over than 16 million € for the absorption cycle and 2.4 million € for low steam production after 15 years, with an Internal Rate of Return of 10%. The Rankine cycle didn’t profit in this particular project.
In 2010, the European Union wasted 43% of produced energy under the form of heat, in power and industry sectors. Leveraged by the retrieval of the economical crisis and sustainable growth, recovery of waste heat has been established as an important goal to the improvement on energy efficiency. In this work, it was studied the alternatives to recovery of excess heat from a low density polyethylene unit. There is a total of 9.3 MW (31.7 million BTU/h) of recoverable waste energy from an ethylene recycling stream, at 280 bar (4 060 psi), cooled from 310°C (590°F) to 130°C (266°F) through an air cooler. Two power cycles (Rankine and Kalina), a cooling cycle (LiBr/water absorption refrigeration system) and heat exchange to produce steam have all been analysed as alternatives to the air cooler, via simulations on Aspen HYSYS®. The performance of 22 potential Rankine fluids was evaluated, being concluded that the hydrocarbons could be suitable Rankine fluids, with pentane having a performance of 18.3%, working in a range of 1.4 to 33 bar (20 to 479 psi). Kalina cycle had a performance of 19.9%, with 90% ammonia, working from 13 to 113 bar (188.5 to 1 639 psi). The need for low pressure steam can be completely satisfied by heat exchanging with ethylene at 310°C (590°F), while 99.7% of hot water can be produced by heat exchanging with ethylene at 130°C (266°F). The production of 4.5 MW (15.5 million BTU/h) of chilled water by an absorption refrigeration system can satisfy all the process needs, using up to three chillers. For an initial temperature of 310°C (590°F), the needs are fulfilled using 32.3 t/h (71,200 lb/h) of ethylene to an 8 bar (114 psi) steam powered double effect system, 46.4 t/h (102,300 lb/h) to a 1 bar (14.5 psi) steam powered single effect system and 41.7 t/h (91,900 lb/h) to a hot water (90°C, 194°F) powered single effect system. Total investment costs were estimated on 9 million € for a Rankine cycle, up to 8.7 million € for an absorption refrigeration cycle and 4.4 millions for low pressure steam production heat exchange. The absorption cycle returns its investment in 3 to 4 years and the steam production heat exchange takes 7 years to profit, resulting in a net worth over than 16 million € for the absorption cycle and 2.4 million € for low steam production after 15 years, with an Internal Rate of Return of 10%. The Rankine cycle didn’t profit in this particular project.
Description
Trabalho final de mestrado para obtenção do grau de Mestre em Engenharia Química e Biológica – Processos Químicos
Keywords
Excesso de calor Excess heat Indústria petroquímica Low density polyethylene Polietileno de baixa densidade Low density polyethylene Simulação Simulation Ciclo Rankine Rankine cycle Ciclo Kalina Kalina cycle Sistema de refrigeração por absorção Absorption refrigeration system. Permuta de calor Heat exchange
Citation
MATOS, Rodolfo Daniel Cerqueira de - Reaproveitamento do excesso de calor proveniente do reciclo de uma unidade de PEBD. Lisboa: Instituto Superior de Engenharia de Lisboa, 2017. Dissertação de mestrado.
Publisher
Instituto Superior de Engenharia de Lisboa