Patent Application
20070284310
In this application, a distilled spirit is ethanol or ethyl alcohol prepared for use as a gasoline supplement by distillation of the broth or beer from the fermentation of corn or some other plant material such as starch, sugar or molasses.
Substances other than ethanol are produced during fermentation, such as higher alcohols, organic acids, esters, aldehydes, tannins and the like. Some of these substances are volatile. Most of the volatile substances have no effect on ethanol quality as a fuel. Some volatile substances in alcohol for beverage or medicinal purposes are undesirable.
Water and volatile substances are evaporated and then condensed with the ethanol in various amounts during distillation. The amounts, i.e. variety and concentrations, of such impurities in fuel grade ethanol are greater than in a grain neutral spirit, which is what is used in beverage or pharmaceutical grade alcohol.
The invention provides a method to adjust the quality of a distilled product or intermediate product from a fuel ethanol production plant.
To produce ethanol, a grain (frequently corn) or other biomass fermentation product is subjected to distillation, by which most of the ethanol is vaporized and condensed in a separate vessel. Along with the ethanol, other low boiling organic compounds and at least 4% water, are vaporized and condensed. These volatiles add specific distinctive qualities to the distillate, depending on the raw materials used in the original brew.
Ethanol can be made from seed grains, particularly corn, by a dry mill process or a wet mill process. Most of the ethanol in the U.S. is made using the dry corn milling method. In the dry mill process, the starch portion of the corn is converted into sugar by cooking and by adding enzymes, the sugars fermented with yeasts and the ethanol is removed by distillation. The wet milling process separates various components in the corn seeds first and then uses the separated starch to make ethanol in a similar process to the dry milling as described.
The majority of the ethanol in the U.S. is made from corn, but it can also be produced from other feedstocks such as grain sorghum, wheat, barley, potatoes, and even grass or wood chips. Brazil, the world's largest ethanol producer, makes the fuel from sugarcane.
The dry milling process first involves milling, liquefaction, saccharification and fermentation.
The beer is now ready to separate ethanol by distillation. The mash is pumped to the continuous flow, multi-column distillation system where the ethanol is removed from the solids and the water by evaporation. The ethanol leaves the top of the final column at 95-96% strength (190-192 proof). The residue mash, called stillage, is transferred from the base of the column to the co-product processing area
The ethanol from the top of the column passes through a dehydration system where the remaining water is removed as required for gasoline additives. Most ethanol plants use a molecular sieve to remove the remaining 4-5% water in the ethanol. The alcohol product at this stage is called anhydrous ethanol (pure, without water) and is approximately 200 proof. Denaturants such as gasoline are added subsequently to fuel ethanol to make the product undrinkable.
The fermentation process is conducted under anaerobic conditions and produces many substances in a reduced chemical state. Subsequent conditions are not conducive to their oxidation. All volatile substances are evaporated during the distillation and condensed with the ethanol. The distillate contains a variety of organic substances albeit in small concentrations. These are of no concern in fuel applications, but would affect the use of the ethanol for other purposes such as in pharmaceuticals or beverages.
The invention relates to the purification of a commercially produced ethanol or alcohol using ozonation to oxidize the reduced state impurities. Ozone (O3) is an allotropic form of oxygen. It is an unstable blue gas with a pungent odor, a molecular weight of 48 g/mol and a density as a gas of 2.154 g/liter at 0° and 1 atmosphere. It is approximately 13 times more soluble in water than is oxygen. Ozone is highly unstable and is a powerful oxidizing agent. It is non-persistent and has a very short half-life.
Typically, ozone is produced by passing oxygen, in some concentration, through a highly charged corona field, a technique known as “corona discharge” ozone generation. The corona may be produced by applying a very high electric potential (up to 20 kV) between two conductors that are separated by an insulating dielectric layer and a small gap. Under these conditions, molecular oxygen (O2) passing through the gap between the conductors experiences sufficient dissociation energy due to an electron bombardment to partially dissociate. A certain fraction of the free oxygen radicals will associate with oxygen molecules to form O3, according to the reaction equation:
3O2+69 kcal⇄2O3 (I)
The generation of ozone as represented by equation (I), is an equilibrium reaction. The reaction is endothermic to produce O3, requiring energy, and is exothermic to produce O2, giving up energy. Because of its equilibrium nature, actual conversion to ozone is relatively low, in the range of 2-14%, depending on the oxygen content of feed gas, the temperature of the reaction and properties of the ozone generator.
In an embodiment, the invention converts or removes impurities from ethanol by oxidizing with ozone and adsorption on granular activated carbon (GAC). In an embodiment the invention relates to a process for treating a distilled ethanol with ozone and adsorption, preferably with granular activated carbon to remove impurities in minutes to produce a higher quality pharmaceutical or beverage alcohol.
Ozonation has “generally regarded as safe” (GRAS) status and may be used in food processing. GRAS status is established by the Food and Drug Administration (See Federal Register Citation 66 FR 33829, docket number 00F-1482, Jun. 26, 2001, Final rule: Electric Power Research Institute, Agriculture and Food Technology Alliance, Ozone in gaseous and aqueous phase as an antimicrobial agent on food, including meat and poultry, 21 CFR 173.368).
Features of the invention will become apparent from the drawings and following detailed discussion, which by way of example without limitation describe preferred embodiments of the invention.
The temperature at the top of the column 14 can be maintained between about 172 to 176° F. so that water vapor condenses and eventually passes down to and exits via the bottom conduit 30. An ethanol rich steam passes from the top of the column 14 via conduit 32 to a cooler 16, where it is condensed into an ethanol-rich liquid. The liquid is fed 34 to the top of gas/liquid contact tower 18. The contact tower 18 can contain a contact medium to promote contact between liquid and gas.
Ozone generator 20 is shown connected by ozone feed line 36 to a lower part of the contact tower 18. The ozone generator 20 can be a typical commercial ozone generator that applies a high-voltage charge to an air or oxygen feed to convert a portion of the feed to ozone-rich discharge gas. For example, the generator 20 can be a corona discharge ozone generator that uses either a desiccated air feed or pure oxygen feed. The ozone air/oxygen mixture can be reacted with the liquid in a batch arrangement or in continuous flow as illustrated in
In a batch arrangement, a quantity of liquid is placed in a container or vat and an ozone gas mixture is dispersed through the liquid using porous diffusers at the end of a gas line. Porous diffusers can be submerged in liquid to a depth for example of at least 6 inches and up to 20 feet. The gas mixture is introduced gradually over a period of at least 10 minutes for lower ozone dosages and longer for higher dosages.
Continuous ozonation as shown in
In the
In an alternative ozone contact method, solid packing material 38, consisting of loose objects with large void spaces, such as ceramic rings, saddles or other irregularly shaped objects is placed in contact tower 18. The ethanol is pumped on to the top of this packing material and allowed to run through the packing material to flow as a film over the individual objects. Ozonated gas is still fed to the column from below. The countercurrent flow and the contact medium 38 within the tower effect an intimate contact between the ethanol rich liquid and gas to effectively ozonate the liquid. The packing material ensures a large contact area between the ethanol and the ozonated gas for good ozone transfer to the ethanol.
In an alternative ozone contact method, perforated plates or trays could be placed horizontally on top of each other in contact tower 18. Space is left between such plates. The ethanol will flow downwards through the holes in the plates, while the ozonated gas flows upwards through the holes. Contact between the gas and liquid phases is enhanced through these holes.
In an alternative contact method, the ethanol is sprayed into contact tower 18 through nozzles. The ethanol will then fall as droplets through the ozonated gas. The ozone encounters a large surface area of droplets for ozone transfer.
In an alternative contact method, the liquid is pumped in a line through a venturi or eductor or injector. The venturi or eductor or injector serves to suck ozone gas into the liquid line to mix the gas with the liquid. The resulting liquor/gas mixture can continue to flow within the line with or without a static mixer that can serve to ensure gas/liquid contact. Then, the gas-liquid mixture is conveyed within the line into a separation vessel to provide an opportunity for the inert gases (air or oxygen) to escape.
Ozone dosage is a function of impurities to be removed. Dosages of ozone between 5 mg/L to 1000 mg/L (ozone to liquid) can be effective. However, in some applications, a dosage of more than 30 mg/L is undesirable as producing a medicinal taste. The dosage can be linked and determined by GC/MS headspace analyses of volatiles. The analysis can identify unwanted compounds to control ozone dosage.
In the
The following EXAMPLE is illustrative and should not be construed as a limitation on the scope of the claims unless a limitation is specifically recited. The EXAMPLE represents work conducted at Iowa State University with the Atmospheric Air Quality Laboratory at this university conducting the analyses.
EXAMPLE A system including a gas/liquid vessel, ozone generator and adsorption vessel was built on laboratory scale and was used to ozonate and to subject samples to adsorption. In the procedure, ozone was generated from a commercial ozone generator (OZX-300U, Enaly Corporation, Shanghai) of 20 to 300 mg/h ozone production capacity, an internal air pump and an external air desiccator. Ozone production was measured using the iodometric method published in Standard Methods for Examination of Water and Wastewater by the American Public Health Association, American Water Works Association and Water Environment Federation, 20th Ed., 1999.
Ozone dosages ranging from 20 to 80 mg/L were applied to an ethanol sample from a corn dry milling facility, containing 95% ethanol. No ozone emerged from the ethanol as it was all consumed in reactions in the ethanol. Some of the ozonated ethanol samples were transferred to a vessel containing granular activated carbon (Filtrasorb® 300, Calgon Corporation, Pittsburgh) and retained there for 5 minutes. The liquor was then filtered through a 100 μm screen to remove any activated carbon granules.
Ethanol without additional treatment was analyzed firstly by adsorbing vapors from the headspace above a sample on a resin at room temperature for 1 hour, a technique known as solid phase micro-extraction (SPME). The adsorbed vapor was then released into a gas chromatograph coupled with mass spectrometry, which also featured a port for olfactory appreciation. The results of these studies are depicted in
As expected, much of the impurities are oxidized to acetic acid. Acetic acid is removed by adsorption on granular activated carbon.
The effect of ozonation at 40 mg/L and of ozonation at 40 mg/L followed by GAC adsorption on ethanol quality as measured by the same methodology as above are shown in
Oxidation by ozone results in a decrease in number and concentration of reduced substances. As expected, the permanganate time of samples after ozonation increases. GAC adsorption also increases permanganate time.
The odor intensity of the various components encountered in an untreated ethanol sample and in samples that have been ozonated to 20, 40 and 80 mg/L and samples ozonated to the same levels and also contacted with granular activated carbon were determined be separating the components as described above and by smelling the individual components. These results are shown in
A number of identified odors and their intensities (0 to 100% scale) and the effect of ozonation and GAC on their removal are listed in Table 1. Both treatments removed some undesirable odors from fuel ethanol, e.g., #10 burnt/burnt plastic, #13 smoky/medicinal. Both treatments produced a new “winey/sweet” note. The GAC treatment removed the offensive “skunky/rancid” note. Thus, both treatments have a great potential in aroma quality enhancement of liquor based on fuel ethanol.
Table 2 shows the removal of 10 selected components and their Chemical Abstract Service (CAS) ID number (identified with pure standard and matches with MS spectral libraries) and odor/aroma intensity removal from fuel ethanol by ozonation and GAC. All the information was obtained using SPME and analyses on GC-MS-O system. Both treatments show a great potential for significantly removing (up to 100%) some potentially/known toxic chemicals carried over from fuel ethanol, e.g., acetaldehyde, hexane, benzene, and styrene.
