Energy efficient global optimisation of reactive dividing wall distillation column

This is the author accepted manuscript. The final version is avialable from Taylor & Francis via the DOI in this recordAn optimisation problem to minimise energy requirements in the synthesis of bio-additive ethyl tertiary butyl ether (ETBE) via reactive dividing wall distillation column (RDWC) is considered. The contribution of the article is to solve a real-world optimisation problem by addressing two challenges: (i) finding optimal process conditions in few numbers of simulations and (ii) handling mixed-integer variables. An efficient global optimisation algorithm is used to find optimal process conditions and adapted to handle both integer and continuous variables. ETBE is produced by the reaction of ethanol and isobutene in RDWC and has proven its niche in reducing the energy requirements for reaction–separation processes. However, the overall economics of the process is governed by the energy requirements. Therefore, it is crucial to find the optimal process conditions for achieving a cost-effective process. Reboiler duty of RDWC, considered as a measure of the energy requirements to be minimised by using the algorithm. Seven variables (four integers and three continuous) are used in the optimisation process to minimise the reboiler duty. A very low value of reboiler duty is obtained after doing the optimisation, which not only provides insight when using RDWC but also shows the potential of the algorithm used.Natural Environment Research Council (NERC

Production of Dimethyl Ether (DME) for Transportation Fuel

Dimethyl Ether (DME) is a proposed alternative to diesel fuel that is being looked into by car and truck manufacturers worldwide. The current market, based almost completely in China, is primed for growth and a U.S. based DME total plant that is economical and environmentally feasible stands to pave the way for America’s DME market, especially since states such as California have approved DME for use as vehicle fuel (Fuel Smarts). Conventionally, the DME is produced by feeding Methanol into a xed-bed gas-phase reactor over a ɣ-alumina catalyst (Dimian et al). Using this process and normal operating conditions (250-400°C and up to 20 bar) operations can reach 70-80% Methanol conversion. The proposed process utilizes the innovative reactive distillation technology and Amberlyst 35 catalyst to achieve a 99.8% Methanol conversion and produce 35,418 kilograms of DME fuel per hour. The reactive distillation is executed at ~130°C (in the reactive stages) and 700 kPa (condenser pressure), and produces water as a byproduct, which exits as the bottoms stream. In order to create a process that is environmentally sustainable, the small amounts of Methanol and DME in the bottoms stream are removed using biotreatment and the water is then released into a nearby river. The product DME is mixed with mineral oil to meet ISO standards and is then stored in an on-site spherical tank farm. Diesel prices will be undercut by the DME product at $1.716 a gallon in order to incentivise companies to make the switch to DME fuel. The DME total plant, located in Beaumont, Texas, serves to provide the local long-haul trucking industry with a cleaner burning fuel for a plant life of 20 years. The DME total plant has an Internal Rate of Return (IRR) of 12.6$12 million, and will turn its rst pro t in 2033. The report addresses nancial, economic, and process concerns to deliver recommendations for the construction that is safest for the environment, the investor, and the plant operator

Demonstration and experimental model validation of the DME synthesis by reactive distillation in a pilot-scale pressure column

The dehydration of methanol to produce the hydrogen carrier and alternative fuel dimethyl ether (DME) is an equilibrium limited reaction, resulting in a relatively complex and expensive production process. A promising method for process intensification is reactive distillation (RD), as this allows the synthesis and purification of DME in a single unit operation. However, existing kinetic models for liquid phase DME synthesis have never been validated in an industrially relevant reactive distillation environment, preventing a detailed model-based design of industrial-scale applications. In this work, a pilot-scale pressure distillation column was used to successfully demonstrate the feasibility of the process involving pure and crude MeOH feed using the catalyst Amberlyst 36. Based on the measured composition and temperature profiles, a kinetic model could successfully be validated for the RD system. A process simulation model was developed in Aspen Plus to analyze an industrial-scale process and validated on the pilot scale. Hereby the influences of column size, methanol feed purity and catalyst selection were examined in detail

Optimized design and techno-economic analysis of novel DME production processes

The shift from gas to liquid phase DME synthesis enables an intensified process concept towards efficient large scale DME production. In this work, four process concepts based on liquid phase DME synthesis were proposed and optimized. A comprehensive economic model was applied with the objective of minimizing the total production cost. All concepts were evaluated applying our previously validated reaction kinetics for commercial ion exchange resin selected catalysts. Furthermore, every process concept was studied with a pure MeOH feed and water-rich (crude) MeOH feedstock. The conventional gas-phase DME production process was simulated and evaluated using the same technical and economic parameters to serve as a benchmark. Using a chlorinated high temperature stable IER catalyst led to significant cost reduction in all the considered concepts. This was due to the higher reaction rate enabled by the higher operating temperature of this catalyst. In the integrated process concept with H2 and CO2 as sustainable feedstocks, it was shown that the reactive distillation process shows a 27% lower production cost, when the crude methanol is directly fed to the DME process instead of being purified in a dedicated crude methanol distillation column. A further techno-economic optimization can be achieved when complementing the reactive distillation column with an additional reactor. Overall, the process concept of a reactive distillation column with a side reactor presents the most promising process concept, enabling a 39% lower production cost than the conventional gas-phase process. By heat integration with a CO2-based MeOH plant, a DME production technology with no external heat demand and a net conversion cost of 54.4 € per tDME is possible

Conceptual design, simulation and experimental validation of divided wall column: application for non-reactive and reactive mixture

Les colonnes à cloison et la distillation réactive présentent de nombreux avantages. Si ces deux concepts sont couplés, cela conduit à un procédé intensifié appelé : colonne à cloison réactive. Ce nouveau procédé intensifié constitue le principal objet d’étude de cette thèse. Dans une première partie, une procédure de design d’une colonne à cloison basée sur le modèle FUGK a été proposée. Dans cette procédure les aspects technologiques et hydrodynamiques sont abordés. Ces paramètres de design obtenus sont ensuite utilisés pour réaliser une simulation rigoureuse et une optimisation de cette colonne en utilisant le logiciel ProSim. Afin de tester cette procédure, des mélanges idéaux et non idéaux ont été utilisés. Il a été montré que cette procédure de design aboutit rapidement aux paramètres de pré design qui permettent d’initialiser de manière satisfaisante la simulation rigoureuse. Dans un second temps, un pilote d’une hauteur de 4m a été conçu, monté et testé au laboratoire. Des résultats expérimentaux ont été obtenus qui valident la procédure sur des mélanges non réactifs en termes de profils de composition et de température ainsi que sur les compositions et les débits de sortie du procédé. Enfin, dans une dernière partie, cette procédure a été adaptée à des mélanges réactifs en combinant les approches de R. Thery et al (2005) et celle de Triantafyllou et al (1992). Ces ultimes développements ont été testés sur la production d’acétate de méthyl par estérification du méthanol par l’acide acétique à la fois d’un de vue expérimental et théorique. ABSTRACT : Divided wall column and reactive distillation have many advantages. If a divided wall column and a reactive distillation are integrated, they leads to a higher integrated process is a reactive divided wall column. However reactive divided wall column has still a new research area. First of all, the thesis proposed a procedure for design of divided wall column, which based on the FUGK model. Both technological and hydrodynamic aspects in the divided wall column are considered in the procedure. Design parameters are then provided to the rigorous simulation and optimization in the ProSimplus software. In order to test this procedure, both ideal and non-ideal ternary mixtures are chosen to be separated in a divided wall column. The results show that the procedure can determine parameters quickly in the case studies and can give a good initialization for rigorous simulation. Secondly, a pilot plant has been design, built and operated in our laboratory (LGC, Toulouse, France, 2013). The pilot plant will provide necessary experimental evidence to validate the previous procedure. Ternary mixture and four-component mixture of alcohols have been used in our pilot plant in steady state conditions. The results show that the composition of products, composition and temperature profile along the column are in very good agreement with simulation results. Finally, a conceptual design method for reactive divided wall column is presented. The pre-design method of R. Thery et al., (2005) and a modified shortcut method for reactive divided wall column that is based on the classical shortcut adapted to a non-reactive divided wall column by C. Triantafyllou and R. Smith (1992) are applied. To verify, simulation and experiment are considered. The methodology has been illustrated for the synthesis of Methyl Acetate from Methanol and Acetic Acid

Intensified distillation-based separation processes: Recent developments and perspective

Greater sustainability can be achieved by decreasing the production costs, energy consumption, equipment size, and environmental impact as well as improvement of the raw material yields, remote control, and process flexibility. Process intensification (PI) as the main route for improving the process performance is used widely in heat transfer, reactions, separation, and mixing, which results in plant compactness, cleanliness, and energy efficiency. Some of the main intensified separation processes and improvement mechanisms are reviewed briefly with the main focus on the PI of distillation processes, which are the most important separation methods. In addition to these technologies, the potential and reliability of reactive separation processes are addressed briefly, which will enable higher efficiency and capacity