Continuous distillation | EPFL Graph Search

Continuous distillation, a form of distillation, is an ongoing separation in which a mixture is continuously (without interruption) fed into the process and separated fractions are removed continuously as output streams. Distillation is the separation or partial separation of a liquid feed mixture into components or fractions by selective boiling (or evaporation) and condensation. The process produces at least two output fractions. These fractions include at least one volatile distillate fraction, which has boiled and been separately captured as a vapor condensed to a liquid, and practically always a bottoms (or residuum) fraction, which is the least volatile residue that has not been separately captured as a condensed vapor. An alternative to continuous distillation is batch distillation, where the mixture is added to the unit at the start of the distillation, distillate fractions are taken out sequentially in time (one after another) during the distillation, and the remaining bo

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

A hybrid absorption-adsorption method to efficiently capture carbon

Berend Smit, Jin Wang, Xiaoqi Zhang

Removal of carbon dioxide is an essential step in many energy-related processes. Here we report a novel slurry concept that combines specific advantages of metal-organic frameworks, ion liquids, amines and membranes by suspending zeolitic imidazolate framework-8 in glycol-2-methylimidazole solution. We show that this approach may give a more efficient technology to capture carbon dioxide compared to conventional technologies. The carbon dioxide sorption capacity of our slurry reaches 1.25 mol l(-1) at 1 bar and the selectivity of carbon dioxide/hydrogen, carbon dioxide/nitrogen and carbon dioxide/methane achieves 951, 394 and 144, respectively. We demonstrate that the slurry can efficiently remove carbon dioxide from gas mixtures at normal pressure/temperature through breakthrough experiments. Most importantly, the sorption enthalpy is only -29 kJ mol(-1), indicating that significantly less energy is required for sorbent regeneration. In addition, from a technological point of view, unlike solid adsorbents slurries can flow and be pumped. This allows us to use a continuous separation process with heat integration.

Nature Publishing Group2014

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

Seifeldine Ahmed Fathalla

2013