Distillation | EPFL Graph Search

Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the heating of solid materials to produce gaseous products (which may condense into liquids or solids); this may involve chemical changes such as destructive distillation or cracking. Distillation may result in essentially complete separation (resulting in nearly pure components), or it may be a partial separation that increases the concentration of selected components; in either case, the process exploits differences in the relative volatility of the mixture's components. In industrial applications, distillation is a unit operation of practically universal importance, but is a physical separation process, not a chemical reaction. An installation used for distillation, especially of distilled beverages, is a distillery. Distillation includes the following

Evaluation of advanced technologies based on integration techniques - Application on dividing wall column

Seifeldine Ahmed Fathalla

In order to separate a mixture into high purity products, Dividing Wall Distillation Columns (DWCs) have shown to be, in most cases, more convenient than using conventional distillation column sequence. In fact in DWCs the entire separation task occurs in one thermally coupled column shell hence reducing investement and operationg cost up to 60%. The DWC is a one column shell with a condensor at the top and a reboiler at the bottom. A wall located inside the shell divides a particular region of the column in two. Size and position of the wall among other elements will have an important effect on product purities strongly dependent on the relative volatility of the components. The assembly of the wall inside the shell represents the most critical step of fabrication, two methods for assembling the wall inside the shell are used, by welding or using stacked wall elements. In order to evaluate DWC using pinch analysis, the DWC has to be separated from the rest of the process GCC, plotting the CGCC and mirroring it to the rest of the process GCC which helps then indentify possible heat recovery between the Column and the background process and hence identify the most efficient way of placing intermediate heat exchangers for heat recovery. Modelling a DWC has proven to be a very difficult task. Using sensitivity analysis we were able to identify the key parameters infulencing the composition of our product streams. In the case of our design, the required high purties in the two stream products meaning 99% Butanol purity and 99% 2-Ethyl- Butanol purity have been reached. Unfortunatly specification to reach low purities in some components for both streams presented to be challenging and were not quite reached (less than 0.5% 2-Ethyl-Butanol was required for the Butanol product stream and 0.68% was reached, less than 0.5% of Hexanol in the 2-Ethyl Butanol product was required and 0.76% was reached). Using pinch analysis tthe MER requirement of both the conventional sequence and the DWC was identified. The CGCC and Carnot CGCC was plotted. The MER for the conventional distillation sequence was found to be 2060 [Kw] while for the DWC model 1809 [Kw]. The DWC has hence an MER 12% lower than what is required for the conventional sequence. However exergy losses in DWC (195 [Kw]) have shown to be larger than for the sequential distillation column (192 [Kw]). This is contrary to the results found in the literature, further improvement of the DWC have to be made.

2013

An Atomistic Simulation Method for Oxygen Impurities in Aluminium Based on Variable Charge Molecular Dynamics

Andreas Elsener

Impurities are known to have a significant impact on materials properties. In particular, the presence of impurities can change mechanical properties and stabilize the microstructure by reducing grain growth and recrystallization processes. In the past atomistic simulations, in particular molecular dynamics, have contributed a lot to the understanding of deformation mechanisms in nanocrystalline metals. Especially, insights into details of dislocation/GB interactions have been gained. Additionally, simulations on coupled grain boundary migration in bicrystalline samples have played an important role in understanding stress assisted grain growth in nanocrystalline metals. However, all these simulations have been performed on monatomic systems. This means that the role of impurities has not yet been considered in these simulations. Some of the important difference between experiments and simulations could be removed by introducing dilute O distributions to computational Al samples. For this purpose, a simulation method is required which can deal with the oxidation of Al atoms around the O impurities and which can simulate the ionic and metallic nature of bonding simultaneously. Here, a method is suggested which fulfills the requirements by modifying the variable charge method of Streitz and Mintmire [Phys. Rev. B 50, 11996 (1994)]. A local chemical potential approach which optimizes the charge on only those atoms expected to be ionic is developed. Additionally the EAM potential for the non-electrostatic interaction given in the publication of Streitz and Mintmire is substituted by empirical potentials which treat the Al-Al interactions with a well-known Al potential. The Al-O and O-O interactions in these EAM potentials are fitted for the simulation of dilute O impurities in Al and additionally for the simulation of corundum in case of a second potential. The aforementioned developments are applied to study the effect of O impurities on the deformation of nc Al. A fully three-dimensional nc sample containing 15 grains of 12 nm grain-size is deformed with a dilute O content in the triple junction lines. The impact of O impurities on dislocation propagation is also considered in a sample which consists of a single grain extracted from a large molecular dynamics simulation. This simulation geometry contains a perfect dislocation, which is pinned at the surrounding grain boundary network. Therefore it allows the study of pinning strength and after unpinning the propagation behavior of the dislocation under various O impurity distributions. Additionally, the role of O impurities on coupled GB migration is investigated by studying two bicrystalline samples with different O distributions in both of them. In the discussion, the emphasis is on the simulation method. Especially, the significance of the samples, simulation conditions and the performance of the method in the different applications are discussed. Additionally, the different developments (local chemical potential approach and EAM potentials) are critically analyzed and improvements for future simulations of impurities are suggested.

EPFL2010

An Atomistic Simulation Method for Oxygen Impurities in Aluminium Based on Variable Charge Molecular Dynamics

Andreas Elsener

EPFL2010

Evaluation of advanced technologies based on integration techniques - Application on dividing wall column

Seifeldine Ahmed Fathalla

2013