This work addresses the challenges in design of heat integrated low-temperature separation processes. A novel, systematic and robust methodology is developed, which contributes to the design practice of heat-integrated separation sequence and the refrigeration system in the context of low-temperature separation processes. Moreover, the methodology exploits the interactions between the separation and refrigeration systems systematically in an integrated design context. The synthesis and optimisation of heat-integrated separation processes is complex due to the large number of design options. In this thesis, task representation is applied to the separation system to accommodate both simple and complex distillation columns. The stream conditioning processes are simulated and their associated costs are included in the overall cost of the process. Important design variables in separation systems, such as the separation sequence, type and operating conditions of the separation units (e.g. the operating pressure, feed quality and condenser type) are optimised. Various refrigeration provision strategies, such as expansion of a process stream, pure and mixed multistage refrigeration systems and cascades of multistage refrigeration cycles, are considered in the present work. A novel approach based on refrigeration system database is proposed, which overcomes the complexities and challenges of synthesis and optimisation of refrigeration systems in the context of low-temperature separation processes. The methodology optimises the key design variables in the refrigeration system, including the refrigerant composition, the number of compression stages, the refrigeration and rejection temperature levels, cascading strategy and the partition temperature in multistage cascaded refrigeration systems. The present approach has selected a matrix based approach for assessing the heat integration potentials of separation and refrigeration systems in the screening procedure. Non-isothermal streams are not considered isothermal and stream splitting and heat exchangers in series are taken into account. Moreover, heat integration of reboiler and condenser of a distillation column through an open loop heat pump system can be considered in this work. This work combines an enhanced simulated annealing algorithm with MILP optimisation method and develops a framework for simultaneously optimising different degrees of freedom in the heat integrated separation and refrigeration processes. Case studies extend the approach to the design of heat integrated separation sequences in above ambient temperature processes. The robustness of the developed framework is further demonstrated when it is utilised to design the LNG and ethylene plant fractionation trains.

Heat-integrated crude oil distillation systems are energy and capital intensive, and have a very complex structure with strong interactions between the individual units. Retrofit of these systems is of major interest to petroleum refiners. Retrofit objectives are various and preferably achieved with minimum capital expenditure, while equipment constraints are met. Traditional approaches to retrofit design of crude oil distillation systems identify promising modifications based on experience or pinch analysis. Later, sequential approaches to retrofit design were developed, in which distillation and heat recovery units are modified individually. Recent approaches considered simultaneously the distillation column and heat integration targets, rather than the existing heat recovery system. That shortcut models for retrofit design of distillation columns are not available is an additional limitation of established methodologies. In this thesis, a new approach is presented for retrofit design of heat-integrated crude oil distillation systems. Shortcut models are developed for distillation retrofit, including reboiled and steam-stripped columns. These models are based on the Underwood equation and are appropriate for retrofit design of simple columns and various complex column arrangements. Models are also proposed for exchanger network retrofit, addition of new columns to the existing distillation unit, modifying column internals, enhancing heat transfer in exchanger tubes and for evaluating CO2 emissions in existing crude oil distillation units. The retrofit design methodology is optimisation-based, and considers the existing distillation process simultaneously with the details of the associated heat recovery system. Existing equipment limitations, such as the hydraulic capacity of the distillation column, exchanger network pressure drop and bottlenecked exchangers, are accounted for. The approach considers various structural modifications and design options resulting in significant benefits. Examples of these are the installation of preflash and prefractionator units to the existing column configuration, replacement of column internals with packing, enhancement of exchanger heat transfer and integration of a gas turbine with an existing furnace. The optimisation framework comprises column and exchanger network retrofit models, cost models and suitable objective functions. The approach optimises all operating conditions of the existing distillation process and any new columns to minimise or maximise a specified objective function, while satisfying existing constraints. The objective function is flexible and varies according to retrofit objectives. Several objectives are taken into account, such as reducing energy consumption and overall cost, increasing capacity, improving profit and reducing CO2 emissions. The approach allows these objectives to be met by considering several design alternatives. The new retrofit approach is applied to different industrial cases of crude oil distillation units, for energy and total cost savings, throughput enhancement, product yield changes, profit increase and emissions reduction. Typical results conclude that retrofit goals can be achieved with substantial savings in energy and total cost, and improved profit with minimal capital investment.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-03-19T17:03:38Z No. of bitstreams: 1 WAGNER BRANDÃO RAMOS - TESE PPGEQ 2016..pdf: 17733872 bytes, checksum: 5e6f59ac00a4f15f43c3f335dc3b2075 (MD5) / Made available in DSpace on 2018-03-19T17:03:39Z (GMT). No. of bitstreams: 1 WAGNER BRANDÃO RAMOS - TESE PPGEQ 2016..pdf: 17733872 bytes, checksum: 5e6f59ac00a4f15f43c3f335dc3b2075 (MD5) Previous issue date: 2016-08-22 / Capes / A destilação extrativa é um método bastante utilizado em indústrias alcooleiras para se obter etanol anidro, cujo processo é composto por duas colunas de destilação, onde a primeira coluna (coluna de destilação extrativa) tem como função desidratar o etanol e a segunda coluna (coluna de recuperação) recuperar o solvente utilizado no processo. Colunas de destilação são responsáveis por um consumo bastante elevado de energia em uma planta e, por isso, diversos métodos de otimização têm sido publicados na literatura, cujos resultados propõem mudanças nas condições operacionais e design do sistema. Além da necessidade de que este sistema opere em condições ótimas, também é necessário se obter um sistema de controle eficiente e que seja capaz de manter o etanol anidro produzido dentro da especificação desejada, mesmo diante distúrbios que ocorrem normalmente neste processo. Sendo assim, o tema deste trabalho surgiu da união destes dois pontos importantes, otimização e controle, no qual o objetivo é estudar o comportamento dinâmico e o controle do processo de destilação extrativa para obtenção de etanol anidro, utilizando etileno glicol como solvente e com integração térmica entre correntes do processo. Sob este escopo, traçou-se objetivos específicos inexistentes na literatura consultada, que são as influências da integração térmica, do teor de solvente e do grau de pureza de etanol anidro que se deseja obter sobre o controle de sistemas de destilação extrativa. Os resultados mostram que o teor de solvente e a presença da integração térmica causam desvios na composição do produto de interesse (etanol anidro), em comparação com o processo sem integração térmica, quando ocorrem distúrbios na alimentação para o mesmo sistema de controle. O grau de pureza de etanol anidro que se deseja obter também causa influência no controle da pureza. De maneira geral, estes efeitos se apresentaram de forma mais acentuada nos casos em que o sistema opera com alto teor de solvente (condição que representa menor consumo energético). Sendo assim, foram propostas modificações no esquema de controle, proporcionando melhores resultados para estes casos. / Extractive distillation is a method widely used in the alcohol industry to obtain anhydrous ethanol, which process consists of two distillation columns where the first column (extractive distillation column) has the function to dehydrate ethanol and the second column (recovery column) recovers the solvent used in the process. Distillation columns are responsible for a very high energy consumption in a plant and thus various methods of optimization, which results suggest changes in operating conditions and system design, have been published in the literature. In addition to the need for this system to operate in optimum conditions, it is also necessary to provide an efficient control system that is able to maintain anhydrous ethanol produced within the desired specification even after the disturbances that normally occur in this process. Thus, the theme of this work arose from the union of these two important points, optimization and control, in which the goal is to study the dynamic behavior and the control of the extractive distillation process for obtaining anhydrous ethanol, using ethylene glycol as a solvent and thermal integration between process streams. Under this scope, specific objectives nonexistent in the literature were drawn, which are the influences of thermal integration, solvent content and the degree of purity of anhydrous ethanol to be obtained on the control of extractive distillation systems. The results show that the solvent content and the presence of thermal integration causes deviations in the product composition of interest (anhydrous ethanol) compared to the process without heat integration, when disturbances occur in the feed for the same control system. The degree of purity of anhydrous ethanol to be obtained also causes influence over controllability. Generally, these effects are exhibited more markedly when the system operates with high solvent content (optimum operating point). So changes were proposed for the control scheme, providing better results for these cases.

Submitted by (edna.saturno@ufrpe.br) on 2016-07-26T14:17:38Z No. of bitstreams: 1 Jose Armando Pires Pereira.pdf: 1552648 bytes, checksum: 8d29d0e12da5e608b1f9eafb6a0bd31c (MD5) / Made available in DSpace on 2016-07-26T14:17:38Z (GMT). No. of bitstreams: 1 Jose Armando Pires Pereira.pdf: 1552648 bytes, checksum: 8d29d0e12da5e608b1f9eafb6a0bd31c (MD5) Previous issue date: 2010-02-25 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The State of Pernambuco, the second largest producer of cachaça in Brazil, has been consolidating the quality of its cachaça and pursued, with success, paths for exporting the product. However, the levels of ethyl carbamate (EC), a recognized genotoxic carcinogen, in the cachaças and sugar cane spirits produced in Pernambuco State are still unknown. A Brazilian regulation (prepared by Ministry of the Agriculture, Livestock and Provisioning – MAPA) that limits the amount of EC in cachaça or sugar cane spirit (150 μgL-1) will come into effect from 30 June 2010. Taking into consideration a possible association between the processing of cachaça, in particular the distillation step, and its EC level, the objective of this work was to investigate the EC levels of recorded (legal) cachaças and sugar cane spirits produced in the State of Pernambuco and their technological profile. Duplicate samplings of 33 brands of cachaças and sugar cane spirits from Pernambuco State were analyzed for EC (through GC-MS) and 9 cachaça producing companies were visited to obtain details on their distillation process. In addition, the samples were analyzed for the following physiochemical parameters: alcoholic degree, volatile acidity, total sugars, total dry extract, and copper. Regarding the physiochemical parameters investigated in the 33 brands, the following percentages of nonconformity with the current MAPA regulations, per parameter, were found: alcoholic degree (27%), volatile acidity (9%), total sugars (9%) and copper (9%). According to the distillation systems applied to the 33 brands, it was found that 13 (39%) were obtained by batch distillation in pot stills (pot still cachaça) and 20 (61%) by continuous distillation in columns stills (column still cachaça). The average EC concentrations varied from less than 10 μgL-1 (detection limit) up to 532.5 μgL-1. Eighteen brands (55%) contained EC levels above the MAPA regulation limit, among these brands only two came from distillation in pot stills. In comparison to columns still cachaças, lower EC levels in cachaças distilled in pot stills, particularly pot stills with the ascending and descending parts made of copper and stainless stills, respectively, were observed. In spite of the higher levels of EC in column still cachaças from Pernambuco State, they can be considered as low when compared to average levels of EC reported by other studies on column still cachaças. One of the possible reasons was the observation that producers of column still cachaça from Pernambuco State have been gradually including and excluding copper in the ascending and descending parts of their column stills, respectively. This study has confirmed that batch distillation in pot still, probably due to the removal of "heads" fraction, richer in EC precursors, combined with high reflux (ascending part) and low distillate contamination with copper (descending part), produces cachaça with very low levels of EC. / O estado de Pernambuco, segundo maior produtor de cachaça do Brasil, tem procurado consolidar a qualidade de suas cachaças e buscado, com sucesso, caminhos para exportação. Até aqui, entretanto, os níveis de carbamato de etila (CE), uma substância reconhecidamente carcinogênica, nas cachaças e aguardentes de cana pernambucanas são desconhecidos. A partir de 30 de junho de 2010 entrará em vigor a Instrução Normativa 13/2005 do Ministério da Agricultura, Pecuária e Abastecimento (MAPA) para CE, a qual estabelece uma tolerância de 150 microgramas (μg) desta substância por litro (L) de cachaça ou aguardente de cana. Tendo em vista uma possível relação entre o processo produtivo, em particular a destilação, e os níveis de CE na cachaça, a presente pesquisa teve como objetivo investigar os níveis de CE nas cachaças e aguardentes de cana produzidas legalmente no estado de Pernambuco em associação com os perfis de produção dos respectivos estabelecimentos produtores. Foram analisadas 33 marcas de cachaças e aguardentes de cana, sendo duas amostras por marca, através da técnica de cromatografia gasosa-espectrometria de massas, e visitados 9 estabelecimentos produtores para obter detalhes do processo de destilação. Complementarmente, as amostras foram analisadas quanto aos seguintes parâmetros físico-químicos: grau alcoólico real, acidez volátil, açúcares totais, extrato seco total e cobre. Do ponto de vista dos parâmetros físico-químicos investigados nas 33 marcas, foram constatados os seguintes percentuais de não atendimento a legislação vigente, por parâmetro: grau alcoólico real (27%), acidez volátil (9%), açúcares totais (9%) e cobre (9%). Relativo aos tipos de aparelho destilador utilizados para produzir as 33 marcas, constatou-se que 13 delas (39%) foram obtidas utilizando sistema de destilação descontínua em alambiques (cachaça de alambique) e 20 (61%) em sistema contínuo por meio de colunas de destilação (cachaça de coluna). As concentrações médias de CE por marca variaram desde menor que 10 μgL-1 (limite de detecção) até 532,5 μgL-1. Dezoito marcas (55 %) apresentaram níveis de CE acima do tolerado pela legislação, sendo que apenas duas delas eram provenientes de sistema de destilação em alambique. Em comparação com as cachaças de coluna, foram observados níveis de CE mais baixos para as cachaças destiladas em alambiques, especialmente os manufaturados com as partes ascendentes e descendentes de cobre e aço inoxidável, respectivamente. Apesar dos maiores níveis de CE nas cachaças pernambucanas de coluna, estes ainda podem ser considerados como baixos quando comparados aos níveis médios de CE reportados em outros estudos sobre as cachaças de coluna do Brasil. Uma das possíveis razões foi a constatação que os produtores de cachaça de coluna do estado de Pernambuco vêm gradualmente incluindo e excluindo o cobre das partes ascendentes e descendentes, respectivamente, de seus aparelhos de destilação. Este estudo confirmou que a destilação descontínua em alambique, motivada provavelmente pela remoção da fração “cabeça” do destilado, mais rica em precursores de CE, aliada com o alto refluxo (parte ascendente) e baixa contaminação do destilado por cobre (parte descendente), produz cachaças com níveis muito reduzidos de CE.