A characterization of diffusion distillation for azeotropic separation

J of Chemical Tech & Biotech

2011

BACKGROUND: Diffusion distillation of ethanol-water mixtures in the presence of air as an inert gas has been used to produce fuel grade ethanol, and studies on the effect of vaporization temperature and feed composition on the selectivity and total molar flux have been presented recently. This paper describes the separation of ethanol-water mixtures by diffusion distillation in the presence of light and heavy inert gases such as helium and argon and reports the changes in selectivity and total molar flux in comparison with those in air.

Section: Resultsmentioning

confidence: 99%

Experimental studies on the effect of inert gases on diffusion distillation of ethanol–water mixtures

J of Chemical Tech & Biotech

2011

“…The product of selectivity and total molar flux is proportional to the enrichment, defined for the separation of binary mixture in an integral diffusion distillation column by McDowell and Davis 6. For a given flow rate of 2.58 × 10 −3 m 3 h −1 , experimental and theoretical values of the product of selectivity and total molar flux is plotted against $x_{1}^{v}$ in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…They have shown how the energy consumption in the entire plant can be minimized. McDowell and Davis6 extended the investigation and the description of process behaviour along the length of an integral column via computer simulation. They presented a model of a diffusion distillation column which shows an improvement over the model of Fullarton and Schlunder 3.…”

Section: Introductionmentioning

confidence: 99%

Fuel grade ethanol by diffusion distillation: an experimental study

J. Chem. Technol. Biotechnol.

2011

BACKGROUND: Fuel grade ethanol (anhydrous ethanol) is considered to be an excellent alternative clean burning fuel to gasoline. It is now used as an additive to gasoline to enhance its octane number and combustibility. Owing to its high energy values, ethanol is the most promising future biofuel. Because of azeotrope formation, anhydrous ethanol cannot be achieved by conventional distillation. Diffusion distillation is one of the several processes that can be used to separate azeotropes. Diffusion distillation takes advantage of differences in relative rates of diffusion using inert gas as selective filter.

“…where

\frac{d x_{1}^{v}}{d l}

is change in mole fraction of ethanol in a differential height

d l

on the vaporization side, termed enrichment …”

Section: Modelingmentioning

confidence: 99%

“…where dx v 1 dl is change in mole fraction of ethanol in a differential height dl on the vaporization side, termed enrichment. 21 Similarly, the change in mole fraction of ethanol in a differential height dl on the condensation side is given by…”

Section: Mass Balancementioning

confidence: 99%

Performance of diffusion distillation column for production of fuel grade ethanol

J of Chemical Tech & Biotech

2014

BACKGROUND Diffusion distillation process was used for separation of ethanol–water mixtures of azeotropic composition. Experimental results were compared with a Stefan–Maxwell equations based mathematical model by assuming point behavior of the process. RESULTS The performance of a diffusion distillation column for anhydrous ethanol production has been investigated by extending the point behavior to an integral column under process relevant operating conditions. New modeling results are in better agreement with the experimental data than old modeling results. The maximum variation in selectivity is obtained at lowest flow rate (0.05 mol m‐1 s‐1). CONCLUSIONS The diffusion distillation column should be operated at the lowest possible feed rate and the highest possible vaporization temperature to minimize the column length requirement for anhydrous ethanol production. The effect of selectivity on enrichment of ethanol is negligible in long diffusion distillation columns and flux to flow ratio is more important for determination of enrichment. © 2014 Society of Chemical Industry