Patent Application
20200207807
The present invention relates generally to corn dry-milling, and more specifically, to a method and system for producing a zein protein product from a whole stillage byproduct produced in a corn (or similar carbohydrate-containing grain) dry-milling process for making alcohol, such as ethanol, and/or other biofuels/biochemicals.
Wet mill processing plants convert, for example, corn grain, into several different co-products, such as germ (for oil extraction), gluten feed (high fiber animal feed), gluten meal (high protein animal feed) and starch-based products such as alcohol (e.g., ethanol or butanol), high fructose corn syrup, or food and industrial starch. However, because constructing wet-milling plants is complex and capital-intensive, almost all new plants built today are dry-milling plants.
Dry milling plants generally convert grains, such as corn, into three products, namely alcohol (e.g., ethanol or butanol), distillers corn oil, and distiller's grains with solubles. A typical corn dry-milling process consists of four major steps: grain handling and milling, liquefaction, saccharification and fermentation, and co-product recovery. Grain handling and milling is the step in which the corn is brought into the plant and ground to promote better starch to glucose conversion. Liquefaction and saccharification is where the starch is converted into glucose. Fermentation is the process of yeast converting glucose into alcohol. Co-product recovery is the step in which the alcohol (e.g., ethanol) and corn by-products are purified and made market ready.
The recovery of alcohol (e.g., butanol, ethanol, etc.) and natural co-products generally begins with the beer (spent fermentation broth) being sent to a distillation system. With distillation, ethanol is typically separated from the rest of the beer through a set of stepwise vaporizations and condensations. The beer less the alcohol extracted through distillation is known as whole stillage, which contains a slurry of the spent grains including corn protein, fiber, oil, minerals, and sugars as well as spent yeast. These byproducts are too diluted to be of much value as mixed together at this point and are further processed to provide the distiller's grains with soluble.
In typical processing, when the whole stillage leaves the distillation column, it is generally subjected to a decanter centrifuge to separate insoluble solids or “wet cake”, which includes mostly fiber, from the liquid or “thin stillage”, which includes, e.g., protein, oil, and amino acids. After separation, the thin stillage moves to evaporators to boil away moisture, leaving a thick syrup that contains soluble (dissolved) solids. The concentrated syrup is typically mixed with the wet cake, and the mixture may be sold to beef and dairy feedlots as distillers wet grain with solubles (DWGS). Alternatively, the wet cake and concentrated syrup mixture may be dried in a drying process and sold as distillers dried grain with solubles (DDGS). The resulting DDGS generally has a crude protein content of about 29% and is a useful feed for cattle and other ruminants due to its protein and fiber content. The resulting product is a natural product.
While DDGS and DWGS provide a critical secondary revenue stream that offsets a portion of the overall ethanol production cost, it would be beneficial to provide a method and system where a back end stream(s) in the corn dry-milling process can be utilized to recover one or more other products that can provide other or additional revenue sources.
The present invention relates to a method and system for producing a zein protein product from a whole stillage byproduct produced in a corn dry-milling process for making alcohol, such as ethanol, and other biofuels/biochemicals.
In one embodiment, a method for producing a zein protein product from a whole stillage byproduct is disclosed that includes separating a whole stillage byproduct into an insoluble solids portion and a solubles portion, which includes zein protein. Then, prior to any evaporation step, the solubles portion is separated into a protein portion including the zein protein, and a water soluble solids portion. In one example, the solubles portion is separated, via weights, into a protein portion including the zein protein, and a water soluble solids portion. The zein protein is next separated from the protein portion to define a zein protein portion and a remaining protein portion, and then the zein protein portion is recovered to define a zein protein product, which includes at least 30 wt % zein protein on a dry basis.
In another embodiment, a method for producing a zein protein product from a whole stillage byproduct is discloses that includes separating a whole stillage byproduct into an insoluble solids portion and a solubles portion, which includes zein protein. Then, prior to any evaporation step, the solubles portion is separated into a protein portion including the zein protein, and a water soluble solids portion. In one example, the solubles portion is separated, via weights, into a protein portion including the zein protein, and a water soluble solids portion. The zein protein is next extracted from the protein portion, then the extracted zein protein separated from the protein portion to define a zein protein portion and a remaining protein portion. Thereafter, the zein protein portion is precipitated out or solvent removed from the zein protein portion to define a zein protein product, which includes at least 30 wt % zein protein on a dry basis.
In another embodiment, a system for producing a zein protein product from a whole stillage byproduct is disclosed that includes a first apparatus that is situated after a distillation column for distilling alcohol and that receives a whole stillage byproduct, the first apparatus separates the whole stillage byproduct-into an insoluble solids portion and a solubles portion, which includes zein protein. A second apparatus is situated after the first apparatus and prior to any evaporator and receives the solubles portion from the first apparatus, wherein the second apparatus separates the solubles portion into a protein portion, including the zein protein, and a water soluble solids portion. In one example, the second apparatus separates the solubles portion, via weights, into a protein portion, including the zein protein, and a water soluble solids portion. An evaporator situated after the second apparatus and receives the water soluble solids portion but does not receive the solubles portion, wherein the evaporator separates soluble solids from the water soluble solids portion, via evaporation. A zein protein extraction system is situated after the second apparatus and extracts the zein protein from the protein portion, which is received from the second apparatus. A third apparatus is situated after the extraction system and separates the extracted zein protein from the protein portion, which is received from the extraction system, to define a zein protein portion and a remaining protein portion. And a recovery system is situated after the third apparatus and recovers the separated zein protein portion to define a zein protein product, which includes at least 30 wt % zein protein on a dry basis.
Zein, an alcohol-soluble storage protein, comprises 45-50% of the protein in corn. Almost all of the zein is present in the endosperm. Zein is rich in glutamic acid, leucine, proline, and alanine but is deficient in basic and acidic amino acids. Zein and its resins can form tough, glossy, hydrophobic grease-proof coatings that are resistant to microbial attack. Other applications of zein include, but are not limited to, use in fibers, adhesives, ceramics, inks, cosmetics, textiles, food products, pharmaceuticals, and biodegradable plastics.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.
The present invention is directed to a method and system for producing a zein protein product from a whole stillage byproduct produced in a corn dry-milling process for making a biofuel, e.g., ethanol, or a biochemical, e.g., lactic acid.
With specific reference to
Liquefaction step 16 may be followed by followed by separate saccharification and fermentation steps, 18 and 20, respectively, although in most commercial dry grind ethanol processes, saccharification and fermentation can occur simultaneously. This single step is referred to in the industry as “Simultaneous Saccharification and Fermentation” (SSF). In the saccharification step 18, the liquefied mash is cooled and a commercial enzyme, such as gluco-amylase, is added to hydrolyze the maltodextrins and short-chained oligosaccharides into single glucose sugar molecules. In the fermentation step 20, a common strain of yeast (Saccharomyces cerevisae) is added to metabolize the glucose sugars into ethanol and CO2. Other fermentation agents such as bacteria and clostridia can be utilized. Upon completion, the fermentation mash (“beer”) will contain about 17% to 18% ethanol (volume/volume basis), plus soluble and insoluble solids from all the remaining grain components, including fiber, protein, minerals, and oil, for example. Yeast can optionally be recycled in a yeast recycling step 22. In some instances, the CO2 is recovered and sold as a commodity product.
Subsequent to the fermentation step 20 is a distillation and dehydration step 24 in which the beer is pumped into distillation columns where it is boiled to vaporize the ethanol. The ethanol vapor is separated in the distillation columns, then condensed and liquid alcohol (in this instance, ethanol) exits the distillation columns at about 95% purity (190 proof). The 190 proof ethanol can then go through a molecular sieve dehydration column or a membrane separation unit or similar dehydration system, which removes the remaining residual water from the ethanol, to yield a final product of essentially 100% ethanol (199.5 proof).
Finally, a centrifugation step 26 involves centrifuging, via a decanter centrifuge, the residuals or whole stillage leftover from distillation so as to separate the insoluble solids portion or “wet cake”, which includes fiber, from the liquid portion or “thin stillage” portion, which includes protein, amino acids, oil, etc. Next, the thin stillage portion enters evaporators in an evaporation step 28 in order to boil away moisture thereby leaving a thick syrup, which contains the soluble (dissolved) solids as well as protein and oil. The concentrated slurry can be sent to a centrifuge to separate the oil from the syrup in an oil recovery step 29. The oil can be sold as a separate high value product.
The resulting syrup is typically referred to as corn condensed distillers solubles and can be mixed with the centrifuged wet cake then sold to beef and dairy feedlots as distillers wet grain with solubles (DWGS). The wet cake and concentrated syrup mixture may be further dried in a drying step 30 and sold as distillers dried grain with solubles (DDGS) to dairy and beef feedlots and/or the monogastric markets. The distiller's grains with solubles co-product provides a critical secondary revenue stream that offsets a portion of the overall ethanol production cost.
In accordance with the present invention,
With reference now to
To filter the whole stillage byproduct, the optional paddle screen 34 can include screen openings of no greater than about 1000 microns. In another example, the paddle screen 34 can include openings therein of no greater than about 500 microns. In another example, the paddle screen 34 can include openings therein of no greater than about 250 microns. In yet another example, the openings therein are no greater than about 150 microns. In yet another example, the openings therein are no greater than about 75 microns. It should be understood that these values are exemplary and that those of ordinary skill in the art will recognize how to determine the size of the openings to achieve the desired filtration rates. In one example, the optional paddle screen 34 is a standard type paddle screen as is known in the art. One such suitable paddle screen 34 is the FQ-PS32 available from Fluid-Quip, Inc. of Springfield, Ohio. It should be understood that the optional paddle screen 34 may be replaced with other types of pre-concentration devices, e.g., a standard pressure screen, conic centrifuge, cyclone, or hydroclone, which can perform the desired filtration or preconcentration function. One such suitable pressure screen is the PS-Triple available from Fluid-Quip, Inc. of Springfield, Ohio. In addition, although a single paddle screen 34 is depicted, it should be understood that a plurality of paddle screens 34 or the like may be situated in-line and utilized for filtering the whole stillage byproduct.
The whole stillage from the distillation and dehydration step 24, if the optional paddle screen 34 is not present, or the cake (solids) from the optional paddle screen 34 is sent to the filtration centrifuge 40 whereat the whole stillage byproduct or overflow is separated into the insoluble solids portion, which includes fiber, and the centrate (solubles) portion, which includes protein, such as zein protein, amino acids, oil, yeast, etc. One such suitable filtration centrifuge is described in Lee et al., U.S. Pat. No. 8,813,973 entitled “Apparatus and Method for Filtering a Material from a Liquid Medium”, the contents of which are expressly incorporated by reference herein in its entirety. The filtration centrifuge 40 may be configured to perform both the initial filtering (sometimes referred to as a pre-concentration) of the whole stillage byproduct and washing of the fiber so as to clean the fiber and remove the protein, including zein protein, amino acids, oil, yeast, and other components that remain associated with the fiber after the initial filtration or pre-concentration.
With respect to the filtration centrifuge 40, the washing of the fiber may include a washing cycle, wherein the fiber is mixed and rinsed in wash water, followed by a de-watering cycle, wherein the wash water is separated from the fiber. The washing of the fiber may include multiple rinsing/de-watering cycles. Additionally, a counter current washing technique may be employed to save wash water usage. After washing the fiber, but before the fiber exits the centrifuge, the fiber may go through an enhanced de-watering stage, a compaction stage, and/or an air dry stage to further de-water or dry the fiber. This may reduce the dryer capacity or eliminate the dryer altogether. Eventually, the washed and filtered fiber exits the filtration centrifuge 40 so that the fiber can be further processed, as discussed further below to result in a desired product, such as DWGS or DDGS. In one example, the fiber can be transported to a remote site for further processing. Moreover, any separated out portion of slurry from the fiber, e.g., water, protein, amino acids, oil, etc., which occurs via screening, is collected to define the centrate (solubles) stream, then transported and further processed as described below. Optionally, a portion of the slurry and/or wash water may be piped back to the optional paddle screen 34 for further reprocessing. The filtration centrifuge 40 may provide the filtered material at a water concentration of between about 55% and about 75% water, which is a significant reduction compared to conventional filtration systems.
With continuing reference to
As further shown in
Fiber having a size less than that of the screen of the filtration centrifuge 40 and/or optional paddle screen 34 may pass through and to subsequent steps of the corn dry-milling process. At the pressure screen 50, the separated fine fiber can be separated from the centrate (solubles) and piped back to the filtration centrifuge 40 or similar unit operations whereat the fine fiber may be filtered out. One such suitable pressure screen 50 is the PS-Triple available from Fluid-Quip, Inc. of Springfield, Ohio. In an alternate embodiment, the optional pressure screen 50 may be replaced with a standard paddle screen or decanter centrifuge, as are mentioned above, or other like device, to aid in separation of the fine fiber from the centrate (solubles) portion. In addition, although a single pressure screen 50 is depicted, it should be understood that a plurality of pressure screens 50 may be situated in-line and utilized for filtering the centrate (solubles) underflow.
The remaining centrate (solubles) portion from the optional pressure screen 50 is piped and subjected to a nozzle centrifuge 52. Alternatively, if the optional pressure screen 50 is not present, the centrate (solubles) can be sent directly to the nozzle centrifuge 52. The nozzle centrifuge 52 can be provided with washing capabilities so that fresh water, along with the centrate (solubles) portion, can be supplied to the nozzle centrifuge 52. The additional fresh water allows for easier separation of the centrate (solubles) into its protein portion and water soluble solids portion. The nozzle centrifuge 52 separates the centrate (solubles) into a protein portion, which includes zein protein, and a water soluble solids portion. The heavier protein portion separates from the water soluble solids portion and is removed as the underflow whereas the lighter water soluble solids portion, which includes oil and sugars, can be removed as the overflow. One such suitable nozzle centrifuge 52 is the FQC-950 available from Fluid-Quip, Inc. of Springfield, Ohio. In an alternate embodiment, the nozzle centrifuge 52 can be replaced with a standard cyclone apparatus or other like device, as are known in the art, to separate the centrate (solubles) portion into the underflow protein portion and overflow water soluble solids portion. One such suitable cyclone apparatus is the RM-12-688 available from Fluid-Quip, Inc. of Springfield, Ohio. It is contemplated that other suitable apparatuses may be utilized here, which may effectively separate the components by other than weight, for example. The resulting protein portion from the nozzle centrifuge 52 can then be piped and subjected to a zein protein extraction step 53.
At the zein protein extraction step 53, the zein protein in the protein portion can be separated therefrom by extraction using a suitable solvent that solubilizes the zein protein. In one example, a polar solvent such as an aqueous solution of an alcohol, e.g., ethanol or isopropanol, can be added to the protein portion to solubilize the zein protein and extract it therefrom. Zein protein is not generally soluble in water except in the presence of an alcohol solvent or, for example, high concentrations of urea or alkali (pH 11 or above), or anionic detergents. Other alcohols suitable for use include, for example, methanol, isobutanol, and propyl alcohol. In one example, the aqueous alcohol solution is 20-99% alcohol. In another example, the aqueous alcohol solution is 30-95% alcohol. In another example, the aqueous alcohol solution is 40-90% alcohol. In another example, the aqueous alcohol solution is 50-90% alcohol. Other suitable solvents can include an anhydrous alcohol solution (e.g., methanol), ketones (e.g., methyl ethyl ketone and acetone), amide solvents (e.g., acetamide), high concentrations of salts (e.g., NaCl or KBr solutions), esters, and glycols. Mixtures and combinations of suitable solvents may also be used for extraction. Heat and/or one or more reducing agents may be added to aid in solubilizing the zein protein.
After the zein extraction step, the protein portion with its solubilized zein protein can be subjected to a zein protein separation step 54 to separate the extracted zein protein from the remaining protein. Separation can be accomplished using, for example, filtration, such as micro and/or ultrafiltration, and/or centrifugation. Concerning microfiltration devices, microfiltration membranes typically include polymer, ceramic, paper, or metal membrane disc or pleated cartridge filters generally rated in the 0.1 to 2 micron range and that generally operate in the 1 to 25 psig pressure range. One such suitable microfiltration separator is the PURON PLUS MBS system provided by Koch Membrane Systems of Wichita, Kans. Ultrafiltration is a crossflow process generally rated in the 10 angstrom to 0.1 micron range and that generally operates in the 10 to 100 psig range. One such suitable ultrafiltration separator is the HFK Series Ultrafiltration provided by Koch Membrane Systems of Wichita, Kans. Centrifugation can be accomplished by means and methods known in the art. In one example, a decanter or filtration centrifuge can be used. In addition, although a single zein protein extraction step 53 and a zein protein separation step 54 are depicted, it should be understood that a plurality of zein protein extraction steps 53 and/or separation steps 54 may occur in-line, either in series or parallel, and utilized for extracting and/or separating the zein protein portion. And although not specifically shown, the filtrate or separated zein protein portion from the zein protein separation step 54 may be further clarified by standing or vacuum filtration methods and/or may be further subjected to a non-solvent, such as toluol, toluene, hexane, or benzene, for removal of non-protein impurities, such as fats and color pigments.
The zein in the resulting zein protein portion from the zein protein separation step 54 can be recovered at zein protein recovery step 56 by means and methods known in the art, such as by precipitation thereof using excess amounts of cold water and/or low temperature (e.g., 0 to −25° C.), solvent removal methods, and the like. Thereafter, the recovered zein protein product can be further optionally dried, such as by being sent to a vacuum dryer 57, as is known in the art, or via other drying methods. In one embodiment, the final dried zein protein product includes at least 30 wt % zein protein on a dry basis. In another embodiment, the final dried zein protein product includes at least 80 wt % zein protein on a dry basis. The final dried zein protein product may be further processed to be sold and/or used as or in, for example, coatings, fibers, adhesives, ceramics, inks, cosmetics, textiles, food products, pharmaceutical, and biodegradable plastics.
The filtered out and remaining protein portion from the zein protein separation step 54 can be subjected to a decanter centrifuge 58. At the decanter centrifuge 58, the remaining protein portion can be dewatered to provide a dewatered remaining protein portion. The decanter centrifuge 58 is standard and known in the art. One such suitable decanter centrifuge 58 is the NX-944HS available from Alfa Laval of Lund, Sweden. In addition, although a single decanter centrifuge 58 is depicted, it should be understood that a plurality of decanter centrifuges 58 may be situated in-line, either in series or parallel. In an alternate embodiment, the decanter centrifuge 58 may be replaced with a standard filter press or rotary vacuum, or other like device, as are known in the art, to dewater the protein portion. A water portion or filtrate from the decanter centrifuge 58 may be recycled back, for example, to liquefaction step 16 or fermentation step 20 for reuse in the dry-milling process.
The dewatered protein portion can be further optionally dried, such as by being sent to a dryer 59, e.g., a spray dryer, as is known in the art. In another embodiment, the remaining protein portion can be subjected to vacuum filtration or other drying methods, as are known in the art. The final dried protein product defines a high protein corn meal. In one example, the final dried protein product defines a high protein corn meal that includes, for example, at least 35 wt % protein on a dry basis and which may be sold as pig, ruminant, fish, or chicken feed, for example. In another embodiment, the final dried protein product defines a high protein corn meal that includes, for example, at least 40 wt % protein on a dry basis and which may be sold as pig, ruminant, fish, or chicken feed, for example. In another embodiment, the high protein corn meal includes at least 45 wt % protein on a dry basis. In another embodiment, the high protein corn meal includes at least 50 wt % protein on a dry basis. In yet another embodiment, the high protein corn meal includes at least 60 wt % protein on a dry basis. In still another embodiment, the high protein corn meal includes about 56 wt % protein on a dry basis. The resulting high protein corn meal may be sold at a much higher cost per ton than DDGS or DWGS. It should be understood that the type and concentration of protein in the zein protein product and high protein corn meal may vary based on the carbohydrate-containing grain source, the fermentation process, and/or the specific application.
Returning now to the separated water soluble solids portion or filtrate from the nozzle centrifuge 52, which includes oil as well as minerals and soluble proteins, the separated water soluble solids portion may be recycled back, for example, to the liquefaction step 16 or the fermentation step 20 for reuse in the dry-milling process. Additionally or alternatively, as shown in
The remainder of the water soluble solids portion can be piped and subjected to another set of three evaporators 60d, 60e, and 60f whereat the liquid portion is further evaporated from the water soluble solids portion to ultimately yield a soluble solids portion. While the water soluble solids portion is subjected to two sets of three evaporators 60a-c, 60d-f, it should be understood that the number of evaporators and sets thereof can be varied, i.e., can be more or less, from that shown depending on the particular application and result desired.
The resulting soluble solids portion may be combined with the insoluble solids portion, e.g., fiber, received from the filtration centrifuge 40 to provide distillers wet grains with soluble (DWGS), which may be further dried by a dryer 62, as is known in the art, to provide distillers dry grains with solubles (DDGS), both of which can be sold to dairy and beef feedlots. In another example, the soluble solids portion may be used as a natural fertilizer. In another example, the soluble solids portion may be used as a raw material feed source for conversion to simple sugar, which than can be further converted to bioethanol or other biochemical processes.
Accordingly, in this dry-milling process, neither the DDGS nor DWGS receive the typical concentrated syrup from the evaporators 60. Despite the lower protein content, the DDGS and DWGS may still be sold to beef and dairy feedlots as cattle feed or other animal feed markets.
While the method and system 32 of
In yet another embodiment, as shown in
While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Thus, the invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative example shown and described. Accordingly, departures may be made from such details without departing from the scope of applicant's general inventive concept.
