US20080308427A1

US20080308427A1 - System and process for producing alcohol

Info

Publication number: US20080308427A1
Application number: US12/140,864
Authority: US
Inventors: Bruce F. Field
Original assignee: Tennant Co
Current assignee: Tennant Co
Priority date: 2007-06-18
Filing date: 2008-06-17
Publication date: 2008-12-18
Also published as: BRPI0813674A2; JP2010530244A; AU2008266893A1; MX2009013743A; WO2008156736A1; CN101743315A; EP2164973A1; KR20100041773A

Abstract

A production system and process comprising mixing electrochemically-activated liquid and feedstock granules to form a slurry a slurry cooker, and producing alcohol from the slurry.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to U.S. Provisional Application No. 60/944,547, filed on Jun. 18, 2007, and entitled “Distillation Process Enhancement for the Production of Ethyl Alcohol”, the disclosure of which is incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present disclosure relates to systems and processes for producing alcohols. More specifically, the present disclosure relates to alcohol production using electrochemically-activated water.

BACKGROUND

Alcohols, such as ethyl alcohol, are typically produced using wet milling or dry milling processes. Wet milling processes involve separating feedstock into components parts, such as starch, prior to undergoing a fermentation process to produce the alcohol. In comparison, dry milling processes involve grinding the feedstock into fine powder granules, and the starch in the granules is then converted to alcohol during the fermentation process.
Agricultural feedstock products of many kinds can be made into alcohol. However, certain steps in production are desirably adhered to maintain process efficiencies. For example, typically about 30 gallons of water is required for every bushel of grain used to produce alcohol. When cooking with steam or at higher temperatures, it is possible to conserve energy by using less water at the beginning. Furthermore, conversion to alcohol is increased by using large amounts of water to encourage a rapid rolling boil. Accordingly, there is an ongoing need for techniques to increase efficiencies in alcohol production systems.

SUMMARY

An aspect of the disclosure is directed to a production system that includes an electrolysis cell configured to electrochemically activate a received liquid, a slurry cooker configured to mix the electrochemically-activated liquid and feedstock granules to form a slurry, a fermentation vessel configured to receive the slurry in a hydrolyzed state and to produce a liquid mixture from the hydrolyzed slurry, where the liquid mixture includes water and alcohol, and a distillation assembly configured to separate at least a portion of the alcohol of the liquid mixture from the water of the liquid mixture.
Another aspect of the disclosure is directed to a process for producing an alcohol product. The process includes heating an electrochemically-activated liquid and feedstock granules in a slurry cooker to form a slurry, where the electrochemically-activated liquid at least partially solvates the feedstock granules. The process further includes hydrolyzing the slurry, fermenting the hydrolyzed slurry to form a liquid mixture that includes water and alcohol, and separating the alcohol of the liquid mixture from the water of the liquid mixture in a distillation assembly.
A further aspect of the disclosure is directed to a process for producing an alcohol product. The process includes electrochemically activating a liquid mixture comprising water and alcohol, feeding the electrochemically-activated liquid mixture to a distillation assembly, and separating the alcohol of the electrochemically-activated liquid mixture from the water of the electrochemically-activated liquid mixture in the distillation assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a production system for producing alcohol using an electrochemically-activated liquid.

FIG. 2 is a schematic illustration of an alternative production system for producing alcohol using an electrochemically-activated liquid, and further using an electrochemically-activated, alcohol/water mixture.

FIG. 3 is a schematic illustration of an electrolysis cell of the production system, where the electrolysis cell has a dual-chamber arrangement with an ion-exchange membrane.

FIG. 4 is a schematic illustration of an alternative electrolysis cell of the production system, where the alternative electrolysis cell includes a single-chamber arrangement without an ion-exchange membrane.

FIG. 5 is a flow diagram of a process for producing alcohol with an electrochemically-activated liquid.

FIG. 6 is a flow diagram of a process for producing alcohol with an electrochemically-activated liquid, and with an electrochemically-activated alcohol/water mixture.

DETAILED DESCRIPTION

An aspect of the present disclosure relates to systems and methods for producing alcohol, such as ethyl alcohol (CH₃CH₂OH), with the use of an electrochemically-activated liquid in the form of an alkaline liquid, an acidic liquid, or a blended combination of the alkaline and acidic species. The electrochemically-activated liquid may be used for one or more stages of the alcohol production, and is particularly suitable for creating slurries with feedstock granules for hydrolysis reactions and fermentation. The following discussion focuses on the use of water and electrochemically-activated water for producing alcohol, such as ethyl alcohol, with the understanding that a variety of different liquids may be used.
FIG. 1 is a schematic illustration of production system 10, which illustrates an aspect of the present disclosure for producing alcohol (e.g., ethyl alcohol) using electrochemically-activated water. As shown, production system 10 includes electrolysis cell 12, feedstock mill 14, slurry cooker 16, fermentation tank 18, solid/liquid (S/L) separator 20, distillation assembly 22, and collection tank 24. The illustration of production system 10 shown in FIG. 1 is simplified for ease of discussion, and production system 10 also desirably includes a variety of additional processing and regulatory components, such as fluid and gas pumps, filters, heat exchangers, valve assemblies, processing sensors (e.g., thermocouples), process-control mechanisms, and the like.
Electrolysis cell 12 is a fluid treatment cell that is adapted to apply an electric field across water (or other liquid) between at least one anode electrode and at least one cathode electrode. Suitable cells for electrolysis cell 12 may have any suitable number of electrodes, and any suitable number of chambers for containing the water. As discussed below, electrolysis cell 12 may include one or more ion exchange membranes between the anode and cathode, or can be configured without ion exchange membranes. Electrolysis cell 12 may have a variety of different structures, such as, but not limited to those disclosed in Field et al., U.S. Patent Publication No. 2007/0186368, published Aug. 16, 2007. In an alternative embodiment, production system 10 may include multiple electrolysis cells 12 that operate in series and/or parallel arrangements to electrochemically activate the water. In additional alternative embodiments, the water may be electrochemically activated from one or more external sources (e.g., one or more external electrolysis cells).
Water is supplied to electrolysis cell 12 through inlet line 26, which correspondingly receives water from feed line 28 and recirculation line 30. Feed line 28 is a water line that provides fresh water from a supply source (not shown), and recirculation line 32 is a water line from distillation assembly 22. The water streams from feed line 28 and recirculation line 30 converge to supply water to inlet line 26. In one embodiment, the water may flow through electrolytic cell 12 as separate streams. For example, as shown in FIG. 1, inlet line 26 may separate into a pair of water lines, thereby separating the water into sub-streams prior to entering electrolytic cell 12. Alternatively, the water may be separated after entering electrolytic cell 12. As the water flows through electrolytic cell 12, the electric field applied across the water in electrolysis cell 12 electrochemically activates the water, which separates the water by collecting positive ions (i.e., cations, H⁺) on one side of an electric circuit and collecting negative ions (i.e., anions, OH⁻) on the opposing side. The water having the cations is thereby rendered acidic and the water having the anions is correspondingly rendered alkaline. In alternative embodiments, the water may enter electrolysis cell 12 directly from inlet line 26 as a single stream.
The electrolysis process may also generate gas-phase bubbles, where the sizes of the gas-phase bubbles may vary depending on a variety of factors, such as the pressure through electrolysis cell 12 and the extent of the electrochemical activation. Accordingly, the gas-phase bubbles may have a variety of different sizes, including, but not limited to macrobubbles, microbubbles, nanobubbles, and mixtures thereof. In embodiments including macrobubbles, examples of suitable average bubble diameters for the generated bubbles include diameters ranging from about 500 micrometers to about one millimeter. In embodiments including microbubbles, examples of suitable average bubble diameters for the generated bubbles include diameters ranging from about one micrometer to less than about 500 micrometers. In embodiments including nanobubbles, examples of suitable average bubble diameters for the generated bubbles include diameters less than about one micrometer, with particularly suitable average bubble diameters including diameters less than about 500 nanometers, and with even more particularly suitable average bubble diameters including diameters less than about 100 nanometers.
The electrolysis process also restructures the water by breaking the water into smaller units that can penetrate cells much more efficiently than normal water. For example, most tap water and bottled water are made of large conglomerates of unstructured water molecules that are too large to move efficiently into cells. The electrochemically-activated water, however, is structured water that penetrates the cells at a much faster rate for better nutrient absorption and more efficient waste removal. Smaller water units also have a positive effect on the efficiency of metabolic processes.
As further shown in FIG. 1, the resulting streams of the electrochemically-activated water may exit electrolysis cell 12 through separate water lines (referred to as outlet lines 32 and 34). Outlet line 32 interconnects electrolysis cell 12 and slurry cooker 16, thereby directing the desired water product stream from electrolysis cell 12 to slurry cooker 16. Outlet line 34 is a purge line of the undesired water product stream, and may be discarded or recycled.
In one embodiment, the water rendered acidic exits electrolysis cell 12 through outlet line 32 as the desired water product stream. The resulting acidic water lacks electrons (i.e., oxidizing water) and has a high oxidation reduction potential. Thus, the acidic water may function as an antibacterial agent, an antimicrobial agent, and/or an antifungal agent. In this embodiment, the water rendered alkaline exits electrolysis cell 12 through outlet line 34 as the undesired water product stream.
In an alternative embodiment, the water rendered alkaline exits electrolysis cell 12 through outlet line 32 as the desired water product stream. The resulting alkaline water is abundant with electrons (i.e., reducing water), and has the capacity to neutralize free radicals at efficient rates. In this embodiment, the water rendered acidic exits electrolysis cell 12 through outlet line 34 as the undesired water product stream. In an additional alternative embodiment, the water rendered acidic and the water rendered alkaline are recombined, and exit electrolysis cell 12 through outlet line 32 as the desired water product stream. As discussed below, despite being recombined, the acidic water and the alkaline water retain their ionic properties and gas-phase bubbles for a sufficient duration to assist in forming a slurry within slurry cooker 16. In this embodiment, outlet line 34 may be omitted.
Feedstock mill 14 includes one or more mechanisms configured to grind received feedstock into fine powder granules for use in slurry cooker 16. Grain mill 14 may have a variety of different configurations for grinding the feedstock (e.g., a hammer mill). Suitable feedstock for use in producing alcohol include materials containing sugars (e.g., sugar beets, sugar cane, sweet sorghum, and ripe fruits), starches (e.g., grains, potatoes, and Jerusalem artichokes), cellulose that may readily be convertible to fermentable sugars (e.g., stover, grasses, and wood), and combinations thereof. Examples of particularly suitable feedstock include materials containing polysaccharide carbohydrate starches (C₆H₁₀O₅)_n, such as amylose-amylopectin-based starches. Feedstock mill 14 grinds the feedstock granules down to suitable particle sizes for suspending the feedstock granules in the electrochemically-activated water (within slurry cooker 16). After being ground, the resulting feedstock granules are relayed to slurry cooker 16 via transit line 36.
Slurry cooker 16 includes one or more tanks in which the feedstock granules are mixed with the electrochemically-activated water and one or more enzymes (e.g., alpha-amylase enzymes) to prepare the feedstock granules for a hydrolysis reaction. Additional materials may also be added to the mixture (e.g., pH modifiers). Suitable ratios of the feedstock granules to electrochemically-activated water may vary depending on a variety of factors, such as the type of feedstock used, the type of enzyme used, the cooking temperature, and the duration of cooking. Examples of suitable ratios of the feedstock granules to electrochemically-activated water range from about 2:1 to about 10:1, with particularly suitable ratios ranging from about 4:1 to about 8:1. The resulting slurry is desirably heated for a suitable duration to attain a desired viscosity for subsequent processing. Suitable elevated temperatures for the cooking process range from about 77° C. (about 170° F.) to about 93° C. (about 200° F.), with particularly suitable elevated temperatures ranging from about 82° C. (about 180° F.) to about 88° C. (about 190° F.). Suitable durations for the cooking process range from about 15 minutes to about two hours, with particularly suitable durations ranging from about 30 minutes to about one hour.
The cations and/or the anions in the electrochemically-activated water assist in at least partially solvating the feedstock granules and enzymes in the liquid medium. The cations and/or the anions of the water at least partially associate with various molecules of the feedstock granules and enzymes, thereby suspending the feedstock granules in the liquid medium. For example, the cations and/or anions may form ionic bonds with the hydroxyl (—OH) groups of the amylose and amylopectin components of starch chains. This is beneficial to prevent the feedstock granules from settling, which can otherwise reduce the uniformity of mixing with the enzymes. This may correspondingly reduce the percentage of conversion during the subsequent hydrolysis reaction. Settling of the feedstock granules may also undesirably cause the feedstock granules to collect along the walls of slurry cooker 16, which may reduce raw material efficiencies in production system 10, and can potentially block passage of the resulting slurry from slurry cooker 16 after the cooking process is complete. In one embodiment, the slurry is also agitated during the cooking process to further assist in suspending the feedstock granules in the liquid medium, and to prevent the formation of hot spots in the slurry, which may otherwise scorch the feedstock granules.
After the cooking process is completed, the resulting slurry is cooled to induce the hydrolysis reaction. In one embodiment, slurry cooker 16 is configured to also function as a coolant heat exchanger to rapidly cool the slurry down. In alternative embodiments, the slurry may be transferred from slurry cooker 16 to a separate cooling unit (e.g., flash condensers, not shown). Additional electrochemically-activated water may also be added via outlet line 32 to assist in cooling the cooked slurry.
In one embodiment, after being cooled, the slurry is reheated for a sufficient duration to allow the enzymes to break the starches down into smaller chains (e.g., dextrose and dextrin). Suitable reheating temperatures for the hydrolysis reaction range from about 77° C. (about 170° F.) to about 93° C. (about 200° F.), with particularly suitable elevated temperatures ranging from about 82° C. (about 180° F.) to about 88° C. (about 190° F.). Suitable durations for the hydrolysis reaction range from about 30 minutes to about four hours, with particularly suitable durations ranging from about one hour to about two hours. After the hydrolysis reaction is completed, the resulting hydrolyzed slurry (i.e., mash) is relayed to fermentation tank 18 via transfer line 38.
Fermentation tank 18 includes one or more vessels configured to allow the hydrolyzed slurry to be further broken down into simple sugars with the use of one or more enzymes (e.g., glucoamylase). Yeast introduced into fermentation tank 18 then breaks down the simple sugars into ethyl alcohol and carbon dioxide, where the carbon dioxide may be purged from fermentation tank 18 through purge line 40. Suitable durations for the fermentation process range from about 50 hours to about 75 hours. The resulting alcohol/water mixture, along with solids (e.g., grain and yeast residue), are then transferred to S/L separator 20 via transit line 42.
S/L separator 20 includes one or more separator units configured to separate the solids from the desired alcohol/water mixture. Suitable separator units for S/L separator 20 may incorporate a variety of separation techniques, and may include centrifuges, rotary screens, perforated tubing with augurs, and combinations thereof. The separated solids may exit S/L separator 20 via purge line 44, and may be collected for further use (e.g., animal feed). The desired alcohol/water mixture is relayed to distillation assembly 22 through fluid line 46.
Distillation assembly 22 includes one or more distillation columns (e.g., column 48), and one or more condensers and reboilers (e.g., condenser 50 and reboiler 52), and is configured to separate the water from the desired alcohol. Examples of suitable distillation columns for column 48 include packed columns, perforated plate columns, bubble cap plate columns, and combinations thereof. As shown, the alcohol/water mixture desirably enters column 52 at a mid-point location between the enriching and stripping sections. Because the water and the alcohol each have a fixed rate of vaporization, which varies with heat and is determined by the vapor pressure developed in a closed container to achieve equilibrium with the fluid, the alcohol can be separated from the water by controlling the heat applied to the mixture. The vapor pressure of alcohol is higher than that of water, so the vapor pressure of the alcohol reaches an equilibrium with atmospheric pressure before the vapor pressure of water does. However, when water and alcohol are mixed, the boiling point of the combination falls between the boiling points of the separate constituents (i.e., water boil at 100° C., and ethyl alcohol boils at 78.3° C.). The ratio of the water to alcohol also determines the actual temperature of boiling for the mixture. Higher concentrations of alcohol lower the boiling point, and vice versa. As such, the temperature of the mixture will rise throughout the distillation run as the alcohol is drawn off.
Because alcohol has a higher vapor pressure than water, the vapors given off by boiling a combination of the two will have a disproportionately large share of alcohol. For example, in a mixture that has 10% by volume ethyl alcohol and 90% by volume water, the vapors released will be about 80% by volume alcohol. To increase the percentage of alcohol, the vapors are condensed and revaporized using condenser 50 and reboiler 52. Each redistillation increases the alcohol concentration of the batch until the liquid reaches the azeotropic limit.
The desired alcohol (e.g., ethyl alcohol) collected at the top of column 22 and condenser 50 may then be transferred to storage container 24 through fluid line 54. In one embodiment, the desired alcohol may also pass through a molecular sieve to remove the water retained due to the azeotropic limit. The separated water collected at the bottom of column 22 and reboiler 52 may then be purged via purge line 56 and/or recycled via recirculation line 30. As discussed above, the use of the electrochemically-activated water increases the suspension of the feedstock granules, thereby increasing the conversion rate of the hydrolyzed slurry into alcohol. This correspondingly reduces the amount of feedstock required to produce alcohol.
FIG. 2 is a schematic illustration of production system 110, which is an alternative to production system 10 (shown in FIG. 1), and where reference labels for the respective components are increased by “100”. As shown in FIG. 2, production system 110 functions in the same manner as production system 10 to produce alcohol (e.g., ethyl alcohol) using electrochemically-activated water that is generated in electrolysis cell 112. Additionally, production system 110 also includes electrolysis cell 158 disposed between S/L separator 120 and distillation assembly 122. Electrolysis cell 158 is a second fluid treatment cell that is adapted to apply an electric field across the alcohol/water mixture, between at least one anode electrode and at least one cathode electrode. Accordingly, electrolysis cell 158 may function in the same manner as electrolysis cell 12 (shown in FIG. 1), and suitable designs for electrolysis cell 158 include those discussed above for electrolysis cell 12.
The alcohol/water mixture is supplied to electrolysis cell 158 through fluid line 146. In one embodiment, the alcohol/water mixture may flow through electrolytic cell 158 as separate streams. For example, as shown in FIG. 2, fluid line 146 may separate into a pair of fluid lines, thereby separating the alcohol/water mixture into sub-streams prior to entering electrolytic cell 158. Alternatively, the alcohol/water mixture may be separated after entering electrolytic cell 158. As the alcohol/water mixture flows through electrolytic cell 158, the electric field applied across the alcohol/water mixture in electrolysis cell 158 electrochemically activates the alcohol/water mixture, which separates the alcohol/water mixture by collecting cations on one side of an electric circuit and collecting anions on the opposing side. In alternative embodiments, the alcohol/water mixture may enter electrolysis cell 158 directly from inlet line 126 as a single stream.
The electrolysis process also desirably generates gas-phase bubbles, where the sizes of the gas-phase bubbles may vary depending on a variety of factors, such as the pressure through electrolysis cell 158 and the extent of the electrochemical activation. Accordingly, the gas-phase bubbles may have a variety of different sizes, including, but not limited to macrobubbles, microbubbles, nanobubbles, and mixtures thereof. In embodiments including macrobubbles, examples of suitable average bubble diameters for the generated bubbles include diameters ranging from about 500 micrometers to about one millimeter. In embodiments including microbubbles, examples of suitable average bubble diameters for the generated bubbles include diameters ranging from about one micrometer to less than about 500 micrometers. In embodiments including nanobubbles, examples of suitable average bubble diameters for the generated bubbles include diameters less than about one micrometer, with particularly suitable average bubble diameters including diameters less than about 500 nanometers, and with even more particularly suitable average bubble diameters including diameters less than about 100 nanometers.
The electrochemically-activated, alcohol/water mixture may then be recombined and directed to distillation assembly 122 via fluid line 160. Due to the higher volatility of the alcohol, the gas-phase bubbles desirably include high concentrations of the alcohol, thereby increasing the separation rate of the alcohol and the water in distillation assembly 122. This increases the efficiency in operating distillation assembly 122 by reducing the duration and energy required to separate the alcohol from the water.
FIG. 3 is a schematic illustration of electrolysis cell 158, which is also a suitable design for electrolysis cell 12 (shown in FIG. 1) and electrolysis cell 112 (shown in FIG. 2). As shown in FIG. 3, electrolysis cell 158 includes membrane 162, which separates electrolysis cell 158 into anode chamber 164 and cathode chamber 166. While electrolysis cell 158 is illustrated in FIG. 3 as having a single anode chamber and a single cathode chamber, electrolysis cell 158 may alternatively include a plurality of anode and cathode chambers separated by one or more membranes 162.
Membrane 162 is an ion exchange membrane, such as a cation exchange membrane (i.e., a proton exchange membrane) or an anion exchange membrane. Suitable cation exchange membranes for membrane 162 include partially and fully fluorinated ionomers, polyaromatic ionomers, and combinations thereof. Examples of suitable commercially available ionomers for membrane 162 include sulfonated tetrafluorethylene copolymers available under the trademark “NAFION” from E.I. du Pont de Nemours and Company, Wilmington, Del.; perfluorinated carboxylic acid ionomers available under the trademark “FLEMION” from Asahi Glass Co., Ltd., Japan; perfluorinated sulfonic acid ionomers available under the trademark “ACIPLEX” Aciplex from Asahi Chemical Industries Co. Ltd., Japan; and combinations thereof.
Anode chamber 164 and cathode chamber 166 respectively include anode electrode 168 and cathode electrode 170, where membrane 162 is disposed between anode electrode 168 and cathode electrode 170. Anode electrode 168 and cathode electrode 170 can be made from any suitable electrically-conductive material, such as titanium, and may be coated with one or more precious metals (e.g., platinum). Anode electrode 168 and cathode electrode 170 may each also exhibit a variety of different geometric designs and constructions, such as flat plates, coaxial plates (e.g., for tubular electrolytic cells), rods, and combinations thereof; and may have solid constructions or can have one or more apertures (e.g., metallic meshes). While anode chamber 164 and cathode chamber 166 are each illustrated with a single anode electrode 168 and cathode electrode 170, anode chamber 164 may include a plurality of anode electrodes 168, and cathode chamber 166 may include a plurality of cathode electrodes 170.
Anode electrode 168 and cathode electrode 170 may be electrically connected to opposing terminals of a conventional power supply (not shown). The power supply can provide electrolysis cell 158 with a constant direct-current (DC) output voltage, a pulsed or otherwise modulated DC output voltage, or a pulsed or otherwise modulated AC output voltage, to anode electrode 168 and cathode electrode 170. The power supply can have any suitable output voltage level, current level, duty cycle, or waveform. In one embodiment, the power supply applies the voltage supplied to anode electrode 168 and cathode electrode 170 at a relative steady state. The power supply includes a DC/DC converter that uses a pulse-width modulation (PWM) control scheme to control voltage and current output. Other types of power supplies can also be used, which can be pulsed or not pulsed, and at other voltage and power ranges. The parameters are application-specific. The polarities of anode electrode 168 and cathode electrode 170 may also be flipped during operation to remove any scales that potentially form on anode electrode 168 and cathode electrode 170.
During operation, the alcohol/water mixture is supplied to electrolysis cell 158 from feed inlets 146 a and 146 b, which are the separated pathways of fluid line 146. The alcohol/water mixture flowing through feed inlet 146 a flows into anode chamber 164, and the alcohol/water mixture flowing through feed inlet 146 b flows into cathode chamber 166. A voltage potential is applied to electrochemically activate the alcohol/water mixture flowing through anode chamber 164 and cathode chamber 166. For example, in an embodiment in which membrane 162 is a cation exchange membrane, a suitable voltage (e.g., a DC voltage) potential is applied across anode electrode 168 and cathode electrode 170. The actual potential required at any position within electrolytic cell 158 may be determined by the local composition of the alcohol/water mixture. In addition, a greater potential difference (i.e., over potential) is desirably applied across anode electrode 168 and cathode electrode 170 to deliver a significant reaction rate. Platinum-based electrodes typically require an addition of about one-half of a volt to the potential difference between the electrodes. In addition, a further potential is desirable to drive the current through electrolytic cell 158. Examples of suitable applied voltage potentials for electrolysis cell 158 range from about 1 volt to about 40 volts, with particularly suitable voltages ranging from about 5 volts to about 25 volts, and with even more particularly suitable voltages ranging from about 10 volts to about 20 volts.
Upon application of the voltage potential across anode electrode 168 and cathode electrode 170, cations (e.g., H⁺) generated in the alcohol/water mixture of anode chamber 164 transfer across membrane 162 towards cathode electrode 170, while anions (e.g., OH⁻) generated in the alcohol/water mixture of anode chamber 164 move towards anode electrode 168. Similarly, cations (e.g., H⁺) generated in the alcohol/water mixture of cathode chamber 166 also move towards cathode electrode 170, and anions (e.g., OH⁻) generated in the alcohol/water mixture of cathode chamber 166 attempt to move towards anode electrode 168. However, membrane 162 prevents the transfer of the anions present in cathode chamber 166. Therefore, the anions remain confined within cathode chamber 166.
While the electrolysis continues, the anions in the alcohol/water mixture bind to the metal atoms (e.g., platinum atoms) at anode electrode 168, and the cations in the alcohol/water mixture (e.g., hydrogen) bind to the metal atoms (e.g., platinum atoms) at cathode electrode 170. These bound atoms diffuse around in two dimensions on the surfaces of the respective electrodes until they take part in further reactions. Other atoms and polyatomic groups may also bind similarly to the surfaces of anode electrode 168 and cathode electrode 170, and may also subsequently undergo reactions. Molecules such as oxygen (O₂) and hydrogen (H₂) produced at the surfaces may enter small cavities in the liquid phase of the alcohol/water mixture (i.e., bubbles) as gases and/or may become solvated by the liquid phase of the alcohol/water mixture. As discussed above, due to the higher volatility of the alcohol (relative to the volatility of the water), the gas-phase bubbles desirably include high concentrations of the alcohol, thereby increasing the separation rate of the alcohol and the water in distillation assembly 122.
Surface tension at a gas-liquid interface is produced by the attraction between the molecules being directed away from the surfaces of anode electrode 168 and cathode electrode 170 as the surface molecules are more attracted to the molecules within the alcohol/water mixture than they are to molecules of the gas at the electrode surfaces. In contrast, molecules of the bulk of the alcohol/water mixture are equally attracted in all directions. Thus, in order to increase the possible interaction energy, surface tension causes the molecules at the electrode surfaces to enter the bulk of the liquid.
In the embodiments in which gas-phase nanobubbles are generated, the gas contained in the nanobubbles (i.e., bubbles having diameters of less than about one micrometer) are also believed to be stable for substantial durations in the liquid phase alcohol/water mixture, despite their small diameters. While not wishing to be bound by theory, it is believed that the surface tension of the alcohol/water mixture, at the gas/liquid interface, drops when curved surfaces of the gas bubbles approach molecular dimensions. This reduces the natural tendency of the nanobubbles to dissipate.
Furthermore, nanobubble gas/liquid interface is charged due to the voltage potential applied across membrane 162. The charge introduces an opposing force to the surface tension, which also slows or prevents the dissipation of the nanobubbles. The presence of like charges at the interface reduces the apparent surface tension, with charge repulsion acting in the opposite direction to surface minimization due to surface tension. Any effect may be increased by the presence of additional charged materials that favor the gas/liquid interface.
The natural state of the gas/liquid interfaces appears to be negative. Other ions with low surface charge density and/or high polarizability (such as Cl⁻, ClO⁻, HO₂ ⁻, and O₂ ⁻) also favor the gas/liquid interfaces, as do hydrated electrons. Aqueous radicals also prefer to reside at such interfaces. Thus, it is believed that the nanobubbles present in the catholyte (i.e., the sub-stream flowing through cathode chamber 166) are negatively charged, but those in the anolyte (i.e., the sub-stream flowing through anode chamber 164) will possess little charge (the excess cations cancelling out the natural negative charge). Accordingly, catholyte nanobubbles are not likely to lose their charge on mixing with the anolyte sub-stream at the convergence point of fluid line 160 (shown in FIG. 2), and are otherwise stable for a duration that is greater than the residence time of the electrochemically-activated, alcohol/water mixture within fluid line 160.
Additionally, gas molecules may become charged within the nanobubbles (such as O₂ ⁻), due to the excess potential on the cathode, thereby increasing the overall charge of the nanobubbles. The surface tension at the gas/liquid interface of charged nanobubbles can be reduced relative to uncharged nanobubbles, and their sizes stabilized. This can be qualitatively appreciated as surface tension causes surfaces to be minimized, whereas charged surfaces tend to expand to minimize repulsions between similar charges. Raised temperature at the electrode surface, due to the excess power loss over that required for the electrolysis, may also increase nanobubble formation by reducing local gas solubility.
As the repulsion force between like charges increases inversely as the square of their distances apart, there is an increasing outwards pressure as a bubble diameter decreases. The effect of the charges is to reduce the effect of the surface tension, and the surface tension tends to reduce the surface whereas the surface charge tends to expand it. Thus, equilibrium is reached when these opposing forces are equal. For example, assuming the surface charge density on the inner surface of a gas bubble (radius r) is Φ(e⁻/meter²), the outwards pressure (“P_out”), can be found by solving the NavierStokes equations to give:
P _out=Φ²/2D∈ ₀ (Equation 1)
where D is the relative dielectric constant of the gas bubble (assumed unity), “∈₀” is the permittivity of a vacuum (i.e., 8.854 pF/meter). The inwards pressure (“P_in”) due to the surface tension on the gas is:
P _in=2g/r P _out (Equation 2)
where “g” is the surface tension (0.07198 Joules/meter²at 25° C.). Therefore if these pressures are equal, the radius of the gas bubble is:
r=0.28792∈₀/Φ². (Equation 3)
Accordingly, for nanobubble diameters of 5 nanometers, 10 nanometers, 20 nanometers, 50 nanometers, and 100 nanometers the calculated charge density for zero excess internal pressure is 0.20, 0.14, 0.10, 0.06 and 0.04 e⁻/nanometer²bubble surface area, respectively. Such charge densities are readily achievable with the use of electrolysis cell 24. The nanobubble radius increases as the total charge on the bubble increases to the power 2/3. Under these circumstances at equilibrium, the effective surface tension of the alcohol/water mixture at the nanobubble surface is zero, and the presence of charged gas in the bubble increases the size of the stable nanobubble. Further reduction in the bubble size would not be indicated as it would cause the reduction of the internal pressure to fall below atmospheric pressure.
In various situations within electrolysis cell 158, the nanobubbles may divide into even smaller bubbles due to the surface charges. For example, assuming that a bubble of radius “r” and total charge “q” divides into two bubbles of shared volume and charge (radius r^1/2=r/2 ^1/3, and charge q_1/2=q/2), and ignoring the Coulomb interaction between the bubbles, calculation of the change in energy due to surface tension (ΔE_ST) and surface charge (ΔE_q) gives:
$\begin{matrix} Δ E_{ST} = + 2 (4 πγ r_{1 / 2}^{2}) - 4 π γ r^{2} = 4 π γ r^{2} (2^{1 / 3} - 1) and & (Equation 3) \\ Δ E_{q} = - 2 [1 / 2 \times \frac{{(q / 2)}^{2}}{4 π ɛ_{0} r_{1 / 2}}] - \frac{1}{2} \times \frac{q^{2}}{4 π ɛ_{0} r} = \frac{q^{2}}{8 π ɛ_{0} r} [1 - 2^{- 2 / 3}] & (Equation 4) \end{matrix}$
The bubble is metastable if the overall energy change is negative which occurs when ΔE_ST+ΔE_qis negative, thereby providing:
$\begin{matrix} \frac{q^{2}}{8 π ɛ_{0} r} [1 - 2^{- 2 / 3}] + 4 π γ r^{2} [2^{1 / 3} - 1] \leq 0 & (Equation 5) \end{matrix}$
which provides the relationship between the radius and the charge density (Φ):
$\begin{matrix} Φ = \frac{q}{4 π r^{2}} \geq \sqrt{\frac{2 γ ɛ_{0}}{r} \frac{[2^{1 / 3} - 1]}{[1 - 2^{- 2 / 3}]}} & (Equation 6) \end{matrix}$
Accordingly, for nanobubble diameters of 5 nanometers, 10 nanometers, 20 nanometers, 50 nanometers, and 100 nanometers the calculated charge density for bubble splitting 0.12, 0.08, 0.06, 0.04 and 0.03 e⁻/nanometer²bubble surface area, respectively. For the same surface charge density, the bubble diameter is typically about three times larger for reducing the apparent surface tension to zero than for splitting the bubble in two. Thus, the nanobubbles will generally not divide unless there is a further energy input.
The electrochemically-activated, alcohol/water mixture, containing the gas-phase bubbles (e.g., macrobubbles, microbubbles, and nanobubbles), exits electrolysis cell 158 via feed outlets 160 a and 160 b, and the sub-streams re-converge at fluid line 160 prior to entering distillation assembly 148. Although the anolyte and catholyte fuels are blended prior to entering distillation assembly 148, they are initially not in equilibrium and temporarily retain their electrochemically-activated states. Accordingly, the electrochemically-activated, alcohol/water mixture contains gas-phase bubbles dispersed/suspended in the liquid-phase alcohol/water mixture, which increases the separation efficiencies of the alcohol/water mixture within distillation assembly 122.
FIG. 4 is a schematic illustration of electrolysis cell 172, which is an example of an alternative electrolysis cell to cell 158 (shown in FIGS. 2 and 3) for electrochemically activating the alcohol/water mixture flowing through fluid line 146, without the use of an ion exchange membrane. Electrolysis cell 172 is also a suitable alternative design for electrolysis cell 12 (shown in FIG. 1) and electrolysis cell 112 (shown in FIG. 2) for electrochemically activating water for use in slurry cooker 16 (shown in FIG. 1) and slurry cooker 116 (shown in FIG. 2).
As shown in FIG. 4, electrolysis cell 172 may engage directly with fluid lines 146 and 160, and includes reaction chamber 174, anode electrode 176, and cathode electrode 178. Reaction chamber 174 can be defined by the walls of electrolysis cell 172, by the walls of a container or conduit in which anode electrode 176 and cathode electrode 178 are placed, or by anode electrode 176 and cathode electrode 178 themselves. Suitable materials and constructions for anode electrode 176 and cathode electrode 178 include those discussed above for anode electrode 168 and cathode electrode 170 (shown in FIG. 3).
During operation, the alcohol/water mixture is introduced into reaction chamber 174 via feed line 146, and a voltage potential is applied across anode electrode 176 and cathode electrode 178. This electrochemically activates the alcohol/water mixture, where portions of the alcohol/water mixture near or in contact with anode electrode 176 and cathode electrode 178 generate gas-phase bubbles in the same manner as discussed above for electrolysis cell 158. Thus, the alcohol/water mixture flowing through electrolysis cell 172 contains gas-phase bubbles dispersed or otherwise suspended in the liquid-phase alcohol/water mixture. In comparison to electrolysis cell 158, however, the electrochemically-activated, alcohol/water mixture is blended during the entire electrolysis process, rather than being split upstream from, or within, the electrolysis cell, and then re-converged, or within, downstream from the electrolysis cell. Accordingly, the resulting electrochemically-activated, alcohol/water mixture contains gas-phase bubbles dispersed/suspended in the liquid-phase alcohol/water mixture, which increases the separation efficiencies of the alcohol/water mixture within distillation assembly 122, as discussed above.
FIG. 5 is a flow diagram of process 180 for producing alcohol (e.g., ethyl alcohol) with an alcohol production system such as production system 10 (shown in FIG. 1). Method 180 includes steps 182-194, and initially involves milling a feedstock into fine powder granules for use in a slurry cooker (step 182). One or more water streams are then supplied to an electrolysis cell, and, while the water streams flow through the electrolysis cell, a voltage potential is applied across anode and cathode electrodes and to the streams (step 184). As discussed above, this electrochemically activates the water.
The electrochemically-activated water is then combined with the milled feedstock to form a slurry, and the slurry is cooked in a slurry cooker (step 186). The cations and/or the anions in the electrochemically-activated water assist in at least partially solvating the feedstock granules and enzymes in the liquid medium, thereby suspending the feedstock granules in the liquid medium. This is beneficial to prevent the feedstock granules from settling, which can otherwise reduce the uniformity of mixing with the enzymes, and reduce the percentage of conversion during a subsequent hydrolysis reaction. After the cooking process is completed, the cooked slurry is hydrolyzed to break the feedstock materials (e.g., starch) into smaller chains (e.g., dextrose and dextrin) (step 188), and the hydrolyzed slurry is then fermented for a suitable duration to convert the hydrolyzed slurry into alcohol (e.g., ethyl alcohol) (step 190).
After the fermentation process is completed, the resulting alcohol/water mixture is desirably separated from the residual solids (step 192), and the alcohol/water mixture is distilled to at least partially separate the alcohol from the water (step 194). As discussed above, electrochemically-activating the water increases the suspension of the feedstock granules, thereby increasing the rate of converting the hydrolyzed slurry into alcohol. This correspondingly reduces the amount of feedstock required to produce alcohol.
FIG. 6 is a flow diagram of process 196 for producing alcohol (e.g., ethyl alcohol) with an alcohol production system such as production system 110 (shown in FIG. 2). Method 196 includes steps 198-212, where steps 198-208 may be performed in the same manner as discussed above for steps 182-192 of process 180 (shown in FIG. 5). In comparison to method 180, process 196 further includes supplying one or more streams of the alcohol/water mixture to an electrolysis cell prior to feeding the mixture to the distillation assembly. While the alcohol/water mixture streams flow through the electrolysis cell, a voltage potential is applied across anode and cathode electrodes and to the streams (step 210). This electrochemically activates the alcohol/water mixture, and desirably generates gas-phase bubbles. The resulting electrochemically-activated, alcohol/water mixture is then distilled to at least partially separate the alcohol from the water (step 212). As discussed above, the electrochemically-activated, alcohol/water mixture increases the separation efficiencies of the alcohol/water mixture within the distillation assembly, thereby increasing the operational efficiency of the distillation assembly.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

1. A production system comprising:

an electrolysis cell configured to receive a liquid, and to electrochemically activate the received liquid;

a slurry cooker configured to receive the electrochemically-activated liquid and feedstock granules, and to mix the electrochemically-activated liquid and the feedstock granules to form a slurry;

a fermentation vessel configured to receive the slurry in a hydrolyzed state, and to produce a liquid mixture from the hydrolyzed slurry, the liquid mixture comprising water and alcohol; and

a distillation assembly configured to receive the liquid mixture, and to separate at least a portion of the alcohol of the liquid mixture from the water of the liquid mixture.

2. The production system of claim 1, wherein the electrolysis cell comprises:

a chamber;

an anode electrode disposed within the chamber, and configured to be electrically connected to a power source; and

a cathode electrode disposed within the chamber, and configured to be electrically connected to the power source.

3. The production system of claim 2, wherein the electrolysis cell further comprises an ion exchange membrane disposed between the anode electrode and the cathode electrode.

4. The production system of claim 1, and further comprising:

a first outlet line interconnecting the electrolysis cell and the slurry cooker, and configured to direct a first portion of the electrochemically-activated liquid from the electrolysis cell to the slurry cooker; and

a second outlet line extending from the electrolysis cell, and configured to direct a second portion of the electrochemically-activated liquid away from the electrolysis cell.

5. The production system of claim 4, wherein the first portion of the electrochemically-activated liquid is selected from the group consisting of alkaline water and acidic water.

6. The production system of claim 1, wherein the electrolysis cell is a first electrolysis cell, and wherein the production system further comprises a second electrolysis cell.

7. The production system of claim 6, wherein the second electrolysis cell is configured to electrochemically activate the liquid mixture, the electrochemically-activated liquid mixture being the liquid mixture received by the distillation assembly.

8. A process for producing an alcohol product, the process comprising:

heating an electrochemically-activated liquid and feedstock granules in a slurry cooker to form a slurry, wherein the electrochemically-activated liquid at least partially solvates the feedstock granules;

hydrolyzing the slurry;

fermenting the hydrolyzed slurry to form a liquid mixture comprising water and alcohol;

feeding the liquid mixture to a distillation assembly; and

separating the alcohol of the fed liquid mixture from the water of the fed liquid mixture in the distillation assembly.

9. The process of claim 8, and further comprising:

introducing feed liquid into an electrolysis cell, the electrolysis cell having at least one cathode electrode and at least one anode electrode; and

applying a voltage potential across the at least one cathode electrode and the at least one anode electrode to generate the electrochemically-activated liquid from the feed liquid.

10. The process of claim 9, and further comprising maintaining separation of at least two portions of the feed liquid with at least one ion exchange membrane disposed between the at least one cathode electrode and the at least one anode electrode.

11. The process of claim 8, and further comprising electrochemically activating the liquid mixture prior to feeding the liquid mixture to the distillation assembly.

12. The process of claim 11, wherein electrochemically activating the liquid mixture comprises:

introducing the liquid mixture into an electrolysis cell, the electrolysis cell having at least one cathode electrode and at least one anode electrode; and

applying a voltage potential across the at least one cathode electrode and the at least one anode electrode to electrochemically activate the liquid mixture.

13. The process of claim 11, wherein electrochemically activating the liquid mixture comprises generating gas-phase bubbles in the liquid mixture.

14. A process for producing an alcohol product, the process comprising:

electrochemically activating a liquid mixture comprising water and alcohol;

feeding the electrochemically-activated liquid mixture to a distillation assembly; and

separating the alcohol of the electrochemically-activated liquid mixture from the water of the electrochemically-activated liquid mixture in the distillation assembly.

15. The process of claim 14, wherein electrochemically activating the liquid mixture comprises:

applying a voltage potential across the at least one cathode electrode and the at least one anode electrode to generate the electrochemically-activated liquid mixture from the liquid mixture.

16. The process of claim 15, and further comprising maintaining separation of the anode chamber and the cathode chamber within the electrolysis cell with an ion exchange membrane.

17. The process of claim 14, wherein electrochemically activating the liquid mixture comprises

introducing a first portion of a liquid mixture into an anode chamber of an electrolysis cell;

introducing a second portion of the liquid mixture into a cathode chamber of the electrolysis cell; and

applying a voltage potential across the first and second portions of the liquid mixture to electrochemically activate the first and second portions of the liquid mixture.

18. The process of claim 14, wherein electrochemically activating the liquid mixture comprises generating gas-phase bubbles in the liquid mixture.

19. The process of claim 14, and further comprising:

heating a feed liquid and feedstock granules in a slurry cooker to form a slurry, wherein the feed liquid at least partially solvates the feedstock granules;

hydrolyzing the slurry; and

fermenting the hydrolyzed slurry to form the liquid mixture.

20. The process of claim 19, wherein fermenting the hydrolyzed slurry also forms residual solids, and wherein the process further comprises at least partially separating the liquid mixture from the residual solids prior to electrochemically activating the liquid mixture.