Ladisch and his students at Purdue University found that drying of ethanol vapors saved energy and was economic. The corn industry makes ethanol by fermentation and has corn grits readily available.Passing the wet vapor over corn grits or other drying agents yield a product that is close enough to absolute ethanol. When the drying agent approaches exhaustion, it is regenerated by heating and reused.Eventually the drying agent breaks down and is used elsewhere in corn processing
The adsorption of water from water/ethanol mixtures over ground corn or corn grits indicates that a combined wavefront is formed. Although a pure thermal wave is possible, the necessary conditions are not satisfied for the ranges of ethanol compositions, temperatures, and initial adsorbent moistures examined in this work.
Other polysaccharide containing materials are also indicated to be potential adsorbents. Starch, hemicellulose, and cellulose have similar water sorption properties (Hong et al., 1982). Hence, depending on the application, a variety of polysaccharide adsorbents including cellulose, carboxymethyl cellulose, cornmeal, corncobs, wheat straw, bagasse, starch, xylan, wood chips, other grains, and mixtures of such materials could be considered (Ladisch and Tsao, 1982).
Under laboratory and pilot plant conditions, cornmeal or associated corn products are stable adsorbents. We speculate that cellulosic materials will also exhibit similar stability. In the event that capacity were lost for corn over a period of time, the cornmeal could still be used to make fermentation-derived ethanol.
Cornmeal and other polysaccharides are attractive for small and medium scale production facilities where other separation schemes do not seem to be appropriate. A need apparently exists for small-scale (ca. 3.8 X 10m L/year) adsorption processes for removing water from organic azeotropes (Garg and Ausikaitis, 1983). Polysaccharide adsorbents appear to have potential in practical schemes for energy-efficient water removal from alcohol.
However, common rocksalt, such as used in water softeners is cheap and available. Remember that the salt must be dry. After absorbing water from a certain amount of alcohol, the salt must be re-dried.
Fill the jar about 3/4 full with 160 Proof Ethanol
Close lid to seal the contents
Shake jar vigorously to be sure the salt and water combine.
Stand jar on a table for 30 minutes
and salt water to fully separate
The dividing line is clearly visible
Siphon the Ethanol from the top
Poor out the water laden salt on a cookie sheet
Oven dry the salt at 300°F for 1 Hour
Or lay it in the sun until the salt is completely dry
The salt can be re-used indefinitely
Solubility" (LAR-14894), the proposed alcohol/water separation process could be exploited industrially to produce clean fuel from fermented vegetable matter.
In one version of this process, castor oil would be added to an ethanol/water solution. The ethanol would mix freely with castor oil, which is insoluble in water. The resulting ethanol/castor-oil phase, which would contain less than 1 percent water, would collect as the top layer, the bottom layer being the remainder of the ethanol/water solution somewhat depleted in ethanol. Heating this two-layer mixture to a temperature slightly below the boiling temperature of ethanol (78.5 °C) would cause the partial pressure of ethanol above the top layer to be much greater than the partial pressure of either castor oil or water. This vapor-phase ethanol could be condensed in a relatively pure state.
Although heating an isolated ethanol/water solution like that in the bottom layer would normally raise the vapor pressure of both ethanol and water above the solution, this would not be the case in the presence of the top castor-oil/ethanol layer for the following reasons: The amount of water that could dissolve in the top castor-oil/ethanol layer would increase only slightly upon heating. On the other hand, ethanol could readily cross the interface between the two layers and enter the top layer. As long as the total mix was kept at a temperature below the boiling temperature of ethanol (thereby preventing agitation of the layers by boiling), the diffusion of water through the castor-oil/ethanol phase would be inhibited.
In an alternative version of this concept, the upper castor-oil/ethanol layer would be skimmed off and heated to obtain the ethanol. Once the ethanol was driven off, the castor oil could be returned to an ethanol/water solution to dissolve more ethanol to repeat the process. This concept could readily lend itself to a continuous process. Substances other than castor oil (one of its components perhaps, or another substance) could be used in this process or to extract other compounds from other mixtures by using this upper-of-two-phases vaporization technique.
A 'molecular sieve' is a material with selective adsorption properties capable of separating components of a mixture on the basis of a difference in molecular size and shape.
In dehydration of ethanol, 3A Zeolite is used to absorb the water content from the ethanol.
MOLECULAR SIEVES EXPLAINED
These beads are like sponges that are full of holes, and are made so that the holes have a rather narrow range of sizes, just the right size to hold water and let ethanol roll off the surface..
Photomicrograph of the surface of a zeolite bead showing the chrystals with holes between the chrystals providing the right space to grab and hold the smaller water molecules. Letting the larger Ethanol molecules slide off the surface of the bead.
Photomicrograph of the surface of a Zeolite bead showing the christal like structure which provide the right space to grab and hold the smaller water molecules. Letting the larger Ethanol molecules slide off the surface of the bead.
Zeolite Dehydartion Technique for Small Producers
The following comment from Peggy G.Korth illustrates this very well.