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Relação da qualidade dos crudes com as emissões de NOX da chaminé principal da refinaria de Sines
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Os óxidos de azoto, NOX, são uns dos principais poluentes atmosféricos provenientes
de uma refinaria, sendo prejudiciais para o meio ambiente e saúde humana.
O principal objetivo desta dissertação é o estudo da relação da qualidade de crudes com
as emissões atmosféricas da chaminé principal da refinaria de Sines, nomeadamente, os óxidos
de azoto. A chaminé principal da refinaria de Sines tem várias fontes de NOX, sendo a principal
a unidade FCC (Fluid Catalytic Cracking) que representa cerca de 60% das emissões totais. As-
sim, estudou-se em pormenor a unidade FCC.
Foram realizadas várias análises com recurso à utilização de ferramentas como a análise
dos componentes principais (PCA), a regressão linear multivariada (RLM) e a regressão por
mínimos quadrados parciais (PLS). Os resultados obtidos concluem que a implementação do
IMO 2020, que limita o teor de enxofre dos combustíveis navais de 3.5% para 0.5%, resultou
num aumento de nitrogénio no crude, que por sua vez levou ao aumento das emissões de
NOX. Os crudes com origem geológica no Brasil, Rússia, Estados Unidos da América, Nigéria
e Líbia estão relacionados com as maiores emissões de NOX. Por sua vez, concluiu-se, pela
análise PCA, que a variável processual, percentagem de oxigénio nos fumos, é a que maior
importância tem no aumento das emissões de óxidos de azoto.
Foram desenvolvidos modelos para cinco períodos, utilizando os métodos de RLM e
PLS. Concluiu-se que as variáveis que mais influenciam a emissão de óxidos de azoto são a
percentagem de oxigénio nos fumos (34%), o coque formado/consumido (16%) e a tempera-
tura de combustão de coque (14%). O modelo entre 22/07/2020 e 17/08/2020 foi o modelo
com melhor ajuste, apresentando um R2 de 0.95 e valores de erro quadrático e a sua raiz de
0.59 e 0.77, respetivamente.
Como proposta de solução para a diminuição das emissões de NOX sugere-se a substi-
tuição de queimadores convencionais por queimadores low NOX, que reduzem em média 40%
as emissões de NOX. Na unidade FCC sugere-se a implementação da técnica redução catalítica
seletiva (SCR), que apesar de ter elevados custos é a que mais reduz a formação de NOX,90%.
Nitrogen oxides, NOX, are one of the main air pollutants from a refinery, being harmful to the environment and human health. The main objective of this dissertation is to study the relationship between crude oil quality and atmospheric emissions from the main chimney of the Sines refinery, namely nitro- gen oxides. The main chimney of the Sines refinery has several sources of NOX, the main one being the FCC (Fluid Catalytic Cracking) unit which represents about 60% of the total emis- sions. Therefore, the FCC unit was studied in detail. Various analyses were conducted employing advanced methodologies including prin- cipal component analysis (PCA), multivariate linear regression (MLR) and partial least squares (PLS) regression. The findings unequivocally demonstrate that the implementation of IMO 2020, which limits the sulphur content of marine fuels from 3.5% to 0.5%, has resulted in an increase of nitrogen in crude oil, which in turn has led to an increase in NOx emissions. Moreover, it was observed that crudes oils originating in Brazil, Russia, the United States of America, Nigeria and Libya exhibit the highest NOX emissions. Futhermore, the PCA research concludes that the percentage of oxygen in smoke, as a process variable, plays a pivotal role in escalation of nitrogen oxide emissions. Models were developed for five periods using the RLM and PLS methods It was con- cluded that the variables that most influence the emission of nitrogen oxides are the percent- age of oxygen in smoke (34%), the coke formed/consumed (16%) and the coke combustion temperature (14%). The model between 22/07/2020 and 17/08/2020 was the model with the best fit, presenting an R2 of 0.95 and values of squared error and its root of 0.59 and 0.77, re- spectively. As a proposed solution to reduce NOX emissions, it is suggested to replace conventional burners with low NOX burners, which reduce NOX emissions by 40% on average. In the FCC unit it is suggested the implementation of the selective catalytic reduction (SCR) technique, which despite having high costs is the one that most reduces the formation of NOX,90%.
Nitrogen oxides, NOX, are one of the main air pollutants from a refinery, being harmful to the environment and human health. The main objective of this dissertation is to study the relationship between crude oil quality and atmospheric emissions from the main chimney of the Sines refinery, namely nitro- gen oxides. The main chimney of the Sines refinery has several sources of NOX, the main one being the FCC (Fluid Catalytic Cracking) unit which represents about 60% of the total emis- sions. Therefore, the FCC unit was studied in detail. Various analyses were conducted employing advanced methodologies including prin- cipal component analysis (PCA), multivariate linear regression (MLR) and partial least squares (PLS) regression. The findings unequivocally demonstrate that the implementation of IMO 2020, which limits the sulphur content of marine fuels from 3.5% to 0.5%, has resulted in an increase of nitrogen in crude oil, which in turn has led to an increase in NOx emissions. Moreover, it was observed that crudes oils originating in Brazil, Russia, the United States of America, Nigeria and Libya exhibit the highest NOX emissions. Futhermore, the PCA research concludes that the percentage of oxygen in smoke, as a process variable, plays a pivotal role in escalation of nitrogen oxide emissions. Models were developed for five periods using the RLM and PLS methods It was con- cluded that the variables that most influence the emission of nitrogen oxides are the percent- age of oxygen in smoke (34%), the coke formed/consumed (16%) and the coke combustion temperature (14%). The model between 22/07/2020 and 17/08/2020 was the model with the best fit, presenting an R2 of 0.95 and values of squared error and its root of 0.59 and 0.77, re- spectively. As a proposed solution to reduce NOX emissions, it is suggested to replace conventional burners with low NOX burners, which reduce NOX emissions by 40% on average. In the FCC unit it is suggested the implementation of the selective catalytic reduction (SCR) technique, which despite having high costs is the one that most reduces the formation of NOX,90%.
Descrição
Palavras-chave
Óxidos de azoto FCC Fornos Emissões atmosféricas Refinaria