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Simulação e Otimização da Unidade de Produção de MTBE, Minimizando a Formação de Compostos Oxigenados na Corrente de Refinado II
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O MTBE é um composto oxigenado amplamente utilizado como aditivo na gasolina melhorando o seu desempenho e reduzindo algumas emissões resultantes da sua combustão.
Este, provem da reação no estado líquido entre isobuteno e metanol na presença de um catalisador ácido, sendo posteriormente purificado e armazenado. A fábrica de MTBE/ETBE da Repsol Polímeros (Sines) está a operar com excesso de oxigenados totais na corrente de Refinado II (>700 ppms wt.), que segue para o steam cracker. Isto deve-se principalmente à presença de DME em excesso. As reações de cracking de oxigenados originam CO e metanol, podendo conduzir a um envenenamento temporário de catalisadores (CO). E na produção de etileno fora de especificação (metanol). O trabalho foi desenvolvido no sentido de identificar a causa raiz do excesso de DME e a sua relação com os parâmetros de operação. Para isto a unidade foi simulada em Aspen Plus®, sendo também estudada a viabilidade económica de possíveis soluções para o problema.
O modelo de simulação foi validado para os vários cenários com erro relativo entre 14% e 30%. Recorrendo a dados reais de operação. Inicialmente foi avaliada a correlação estatística entre o teor de DME reportado e alguns parâmetros de operação (excesso de metanol, temperatura de entrada no R0901, caudal de água de lavagem). Não havendo dependências flagrantes a relatar. Realizou-se depois uma análise de sensibilidade à produção de DME onde se variaram as temperaturas de entrada no primeiro reator (R0901), da água de arrefecimento (R0901), de entrada no segundo reator (R0902) e o excesso molar de metanol (resultando em sensibilidades respetivas de 1,37; 4,17; 0,12 e 2,24). Das quatro soluções propostas (crivo molecular, destilação reativa, coluna de lavagem adicional e uma purga de água de lavagem na coluna existente). Apenas o crivo molecular e a purga de água se revelaram viáveis. Apontando o primeiro para um teor combinado de 10 ppms (wt.) de DME e MTBE, com um VAL de 0,33 milhões de €. Já a purga conseguiu diminuir a concentração de DME em ≈ 50%, com um VAL de 0,14 milhões de €.
MTBE is widely used as an additive in gasoline, improving its performance and reducing some of its emissions. This compound is derived from the liquid phase reaction between isobutene and methanol in the presence of an acid catalyst, and it is subsequently purified and stored. Repsol Polímeros’ MTBE/ETBE plant in Sines is operating with an excess of total oxygenates in the Raffinate II stream (>700 ppms wt.), which is then sent to the steam cracker. This is mainly due to the presence of excess DME. Cracking reactions of oxygenates produce CO and methanol, which can lead to temporary catalyst poisoning (CO) and out-of-spec ethylene production (methanol). This work was carried out to identify the root cause of the DME excess and its relationship with operational parameters. For this purpose, the unit was simulated in Aspen Plus®, and the economic feasibility of possible solutions to the problem was also studied. The simulation model validated with relative errors between 14% and 30%, using real operational data. Initially, the statistical correlation between reported DME content and some operational parameters (excess methanol, inlet temperature in R0901, washing water flow rate) was evaluated, with no significant dependencies to report. A sensitivity analysis of DME production was then conducted, varying the inlet temperatures in the first reactor (R0901), cooling water temperature (R0901), inlet temperature in the second reactor (R0902), and excess molar methanol (resulting in respective sensitivities of 1.37, 4.17, 0.12, and 2.24). Out of the four proposed solutions (molecular sieve, reactive distillation, additional washing column, and a washing water purge in the existing column), only the molecular sieve and the water purge proved to be viable. They respectively led to a combined DME and MTBE content of 10 ppms (wt.) with a Net Present Value (NPV) of €0.33 million and a roughly 50% reduction in DME concentration for the purge, with an NPV of €0.14 million
MTBE is widely used as an additive in gasoline, improving its performance and reducing some of its emissions. This compound is derived from the liquid phase reaction between isobutene and methanol in the presence of an acid catalyst, and it is subsequently purified and stored. Repsol Polímeros’ MTBE/ETBE plant in Sines is operating with an excess of total oxygenates in the Raffinate II stream (>700 ppms wt.), which is then sent to the steam cracker. This is mainly due to the presence of excess DME. Cracking reactions of oxygenates produce CO and methanol, which can lead to temporary catalyst poisoning (CO) and out-of-spec ethylene production (methanol). This work was carried out to identify the root cause of the DME excess and its relationship with operational parameters. For this purpose, the unit was simulated in Aspen Plus®, and the economic feasibility of possible solutions to the problem was also studied. The simulation model validated with relative errors between 14% and 30%, using real operational data. Initially, the statistical correlation between reported DME content and some operational parameters (excess methanol, inlet temperature in R0901, washing water flow rate) was evaluated, with no significant dependencies to report. A sensitivity analysis of DME production was then conducted, varying the inlet temperatures in the first reactor (R0901), cooling water temperature (R0901), inlet temperature in the second reactor (R0902), and excess molar methanol (resulting in respective sensitivities of 1.37, 4.17, 0.12, and 2.24). Out of the four proposed solutions (molecular sieve, reactive distillation, additional washing column, and a washing water purge in the existing column), only the molecular sieve and the water purge proved to be viable. They respectively led to a combined DME and MTBE content of 10 ppms (wt.) with a Net Present Value (NPV) of €0.33 million and a roughly 50% reduction in DME concentration for the purge, with an NPV of €0.14 million
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Simulação Aspen Plus DME Oxigenados