Aspen Plus® Study to Enhance Benzene Production by Hydrogen Purification at Dow's Aromatic ...

119 Pages·2015·3.86 MB·English

Aspen Plus® Study to Enhance Benzene Production by
Hydrogen Purification at Dow’s Aromatic Plants
in The Netherlands

Joana de Oliveira Moutinho

Thesis to obtain the Master of Science Degree in
Chemical Engineering

Supervisors:
Professora Doutora Maria Diná Ramos Afonso
Master Jan Tange
Bachelor Levien Everaert

Examination Committee
Chairperson: Professor Doutor Sebastião Manuel Tavares da Silva Alves
Supervisor: Professora Doutora Maria Diná Ramos Afonso
Members of the Committee: Professora Doutora Maria Rosinda Costa Ismael

May, 2015
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“Tell me and I forget

Show me and I may remember
Involve me and I understand”

by Benjamim Franklin

“Keep it simple” by Wim Kamperman

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Acknowledgments
First of all, I would like to thank Jan Tange for giving me the opportunity to work in such a great
international enterprise as The Dow Chemical Company. In particular, I also would like to deeply thank
Levien Evaraert and Wim Kamperman for their availability to help me and answer my questions
anytime. I had learned a lot from them during the four months internship.
I would like to express my gratitude to Professor Diná Afonso for all her guidance, support in many
issues, friendship and incredible patience during these last 9 months.
I also would like to thank all my friends and colleagues that in many ways helped me along the MSc
degree in Chemical Engineering.
A word of gratitude especially goes to Pedro Galamba for all his love, patience and endless support
shown throughout the last few years.
Last, but certainly not least, I would like to thank my parents for their unconditional support along the
journey that has been my academic life. This thesis is dedicated to them.

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Abstract
This work studied the hydrogen purification in the cold box unit (Aromatics-2 facility) at Dow´s plant in
The Netherlands, with the main aim of rising the benzene production in 35% at the hydrogenation
reactor (Aromatics-1 facility), whenever the hydrodealkylation reactor was stopped.
A model of the cold box was developed by using the Aspen Plus® V8.0 software and it was validated
based on the plant process data, revealing deviations < 10%. The cold box model was tested for its
robustness, being concluded that the model was valid for feed flow rates from 2,8 up to 30 t/h.
Subsequently, three distinct scenarios were analysed by using the developed Aspen model. Case
study 1 represented the current plant situation, in which the hydrodealkylation reactor was working.
Case Study 2 represented the main aim of this study, i.e., it considered the hydrodealkylation reactor
stopped. Additionally, Case Study 3 was analogous to Case Study 2 but it considered the washing
column working normally.
Sensitivity analyses were conducted for the Case Study 2 whereas Case Studies 1 and 3 were
analysed by single simulations. In all the cases, a cold box feed stream of 22,7 t/h and a hydrogen
purity of 90% (v/v) were set. In Case Study 1, the heavies ended up in the ethane outlet stream unlike
Case Study 3, in which the heavies ended up in the methane outlet stream. In Case Study 2, the
methane stripper was dispensable and yet the model yielded trustworthy results.

Keywords:
Aspen; benzene production; cold box unit; hydrodealkylation reaction; hydrogen

purification; trickle flow reactor.
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Resumo
Neste trabalho estudou-se a purificação de hidrogénio na caixa fria (unidade de Aromáticos-2) da
fábrica de produtos químicos da Dow na Holanda, com o objectivo primordial de aumentar a produção
de benzene em 35% no reactor de hidrogenação (unidade de Aromáticos-1), quando o reactor de
hidrodealquilação estiver parado.
Desenvolveu-se um modelo da caixa fria utilizando o software Aspen Plus® V8.0, que foi validado
pelos dados processuais da fábrica, revelando desvios < 10%. Efectuou-se um teste de robustez que
demonstrou que o modelo era válido para caudais de alimentação da caixa fria na gama 2,8-30 t/h.
Posteriormente, analisaram-se três cenários fabris recorrendo-se ao modelo desenvolvido. O Caso
Estudo 1 representou a situação actual da fábrica, na qual o reactor de hidrodealquilação estava em
funcionamento. O Caso Estudo 2 representou o objectivo deste projecto, i.e., considerou-se o reactor
de hidrodealquilação parado. O Caso Estudo 3, idêntico ao 2, considerou a coluna de lavagem em
funcionamento.
Realizaram-se diversas análises de sensibilidade ao Caso Estudo 2, enquanto que os Casos Estudo
1 e 3 foram analisados por simulações individuais. Em todos os casos, considerou-se a alimentação
da caixa fria de 22,7 t/h e fixou-se a pureza do hidrogénio em 90% (v/v). Nos Casos Estudo 1 e 3 os
componentes pesados surgiram nas correntes de saída da caixa fria referentes ao etano e ao
metano, respectivamente. O modelo do Caso Estudo 2 forneceu resultados fidedignos e concluiu-se
que a coluna de stripping era dispensável.

Palavras-chave:
Aspen; hidrodealquilação; produção de benzeno; purificação de

hidrogénio; reactor de hidrogenação; unidade criogénica.
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