Patent Description:
The conventional processes for producing various types of biochemicals, such as biofuels (e.g., alcohol) and other chemicals, from grains generally follow similar procedures. Wet mill processing plants convert, for example, corn grain, into several different coproducts, 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. Dry grind plants generally convert grains, such as corn, into two products, namely alcohol (e.g., ethanol or butanol) and distiller's grains with solubles. If sold as wet animal feed, distiller's wet grains with solubles are referred to as DWGS. If dried for animal feed, distiller's dried grains with solubles are referred to as DDGS. This co-product provides a secondary revenue stream that offsets a portion of the overall alcohol production cost.

With respect to the wet mill process, <FIG> is a flow diagram of a typical wet mill alcohol (e.g., ethanol) production process <NUM>. The process <NUM> begins with a steeping step <NUM> in which grain (e.g., corn) is soaked for <NUM> to <NUM> hours in a solution of water and sulfur dioxide in order to soften the kernels for grinding, leach soluble components into the steep water, and loosen the protein matrix with the endosperm. Corn kernels contain mainly starch, fiber, protein, and oil. The mixture of steeped corn and water is then fed to a degermination mill step (first grinding) <NUM> in which the corn is ground in a manner that tears open the kernels and releases the germ so as to make a heavy density (<NUM> to <NUM> Be) slurry of the ground components, primarily a starch slurry. This is followed by a germ separation step <NUM> that occurs by flotation and use of a hydrocyclone(s) to separate the germ from the rest of the slurry. The germ is the part of the kernel that contains the oil found in corn. The separated germ stream, which contains some portion of the starch, protein, and fiber, goes to germ washing to remove starch and protein, and then to a dryer to produce about <NUM> to <NUM> (dry basis) of germ per m<NUM> of corn (<NUM> to <NUM> pounds (dry basis) of germ per bushel of corn (lb/bu)). The dry germ has about <NUM>% oil content on a dry basis.

The remaining slurry, which is now devoid of germ but contains fiber, gluten (i.e., protein), and starch, is then subjected to a fine grinding step (second grinding) <NUM> in which there is total disruption of endosperm and release of endosperm components, namely gluten and starch, from the fiber. This is followed by a fiber separation step <NUM> in which the slurry is passed through a series of screens in order to separate the fiber from starch and gluten and to wash the fiber clean of gluten and starch. The fiber separation stage <NUM> typically employs static pressure screens or rotating paddles mounted in a cylindrical screen (i.e., paddle screens). Even after washing, the fiber from a typical wet grind mill contains <NUM> to <NUM>% starch. This starch is sold with the fiber as animal feed. The remaining slurry, which is now generally devoid of fiber, is subjected to a gluten separation step <NUM> in which centrifugation or hydrocyclones separate starch from the gluten. The gluten stream goes to a vacuum filter and dryer to produce gluten (protein) meal.

The resulting purified starch co-product then can undergo a jet cooking step <NUM> to start the process of converting the starch to sugar. Jet cooking refers to a cooking process performed at elevated temperatures and pressures, although the specific temperatures and pressures can vary widely. Typically, jet cooking occurs at a temperature of about <NUM> to <NUM> (about <NUM> to <NUM>°F) and a pressure of about <NUM> to <NUM> MPa (about <NUM> to <NUM> psi). This is followed by liquefaction <NUM>, saccharification <NUM>, fermentation <NUM>, yeast recycling <NUM>, and distillation/dehydration <NUM> for a typical wet mill biochemical system. Liquefaction occurs as the mixture or "mash" is held at <NUM> to <NUM> in order for alpha-amylase to hydrolyze the gelatinized starch into maltodextrins and oligosaccharides (chains of glucose sugar molecules) to produce a saccharafied mash or slurry. In the saccharification step <NUM>, the liquefied mash is cooled to about <NUM> and a commercial enzyme known as gluco-amylase is added. The gluco-amylase hydrolyzes the maltodextrins and short-chained oligosaccharides into single glucose sugar molecules to produce a liquefied mash. In the fermentation step <NUM>, a common strain of yeast (Saccharomyces cerevisae) is added to metabolize the glucose sugars into ethanol and CO<NUM>.

Upon completion, the fermentation mash ("beer") will contain about <NUM>% to <NUM>% ethanol (volume/volume basis), plus soluble and insoluble solids from all the remaining grain components. The solids and some liquid remaining after fermentation go to an evaporation stage where yeast can be recovered as a byproduct. Yeast can optionally be recycled in a yeast recycling step <NUM>. In some instances, the CO<NUM> is recovered and sold as a commodity product. Subsequent to the fermentation step <NUM> is the distillation and dehydration step <NUM> in which the beer is pumped into distillation columns where it is boiled to vaporize the ethanol. The ethanol vapor is separated from the water/slurry solution in the distillation columns and alcohol vapor (in this instance, ethanol) exits the top of the distillation columns at about <NUM>% purity (<NUM> proof). The <NUM>% purity (<NUM> proof) ethanol then goes through a molecular sieve dehydration column, which removes the remaining residual water from the ethanol, to yield a final product of essentially <NUM>% ethanol (<NUM> proof). This anhydrous ethanol is now ready to be used for motor fuel purposes. Further processing within the distillation system can yield food grade or industrial grade alcohol.

No centrifugation step is necessary at the end of the wet mill ethanol production process <NUM> as the germ, fiber, and gluten have already been removed in the previous separation steps <NUM>, <NUM>, <NUM>. The "stillage" produced after distillation and dehydration <NUM> in the wet mill process <NUM> is often referred to as "whole stillage" although it also is technically not the same type of whole stillage produced with a traditional dry grind process described in <FIG> below, since no insoluble solids are present. Other wet mill producers may refer to this type of stillage as "thin" stillage.

The wet grind process <NUM> can produce a high quality starch product for conversion to alcohol, as well as separate streams of germ, fiber, and protein, which can be sold as coproducts to generate additional revenue streams. However, the overall yields for various coproducts can be less than desirable and the wet grind process is complicated and costly, requiring high capital investment as well as high-energy costs for operation.

Because the capital cost of wet grind mills can be so prohibitive, some alcohol plants prefer to use a simpler dry grind process. <FIG> is a flow diagram of a typical dry grind alcohol (e.g., ethanol) production process <NUM>. As a general reference point, the dry grind method <NUM> can be divided into a front end and a back end. The part of the method <NUM> that occurs prior to distillation <NUM> is considered the "front end," and the part of the method <NUM> that occurs after distillation <NUM> is considered the "back end. " To that end, the front end of the dry grind process <NUM> begins with a grinding step <NUM> in which dried whole corn kernels can be passed through hammer mills for grinding into meal or a fine powder. The screen openings in the hammer mills or similar devices typically are of a size of about <NUM> to <NUM> (<NUM>/<NUM> to <NUM>/<NUM> inch), but some plants can operate at less than or greater than these screen sizes. The resulting particle distribution yields a very wide spread, bell type curve, which includes particle sizes as small as <NUM> microns and as large as <NUM> to <NUM>. The majority of the particles are in the range of <NUM> to <NUM> microns, which is the "peak" of the bell curve.

After the grinding step <NUM>, the ground meal is mixed with cook water to create a slurry at slurry step <NUM> and a commercial enzyme called alpha-amylase is typically added (not shown). The slurry step <NUM> is followed by a liquefaction step <NUM> whereat the pH can be adjusted to about <NUM> to <NUM> and the temperature maintained between about <NUM> to <NUM> so as to convert the insoluble starch in the slurry to soluble starch. Various typical liquefaction processes, which occur at this liquefaction step <NUM>, are discussed in more detail further below. The stream after the liquefaction step <NUM> has about <NUM>% dry solids (DS) content, but can range from about <NUM>-<NUM>%, with all the components contained in the corn kernels, including starch/sugars, protein, fiber, starch, germ, grit, oil, and salts, for example. Higher solids are achievable, but this requires extensive alpha amylase enzyme to rapidly breakdown the viscosity in the initial liquefaction step. There generally are several types of solids in the liquefaction stream: fiber, germ, and grit.

Liquefaction may be followed by separate saccharification and fermentation steps, <NUM> and <NUM>, 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). Both saccharification and SSF can take as long as about <NUM> to <NUM> hours. Fermentation converts the sugar to alcohol. Yeast can optionally be recycled in a yeast recycling step (not shown) either during the fermentation process or at the very end of the fermentation process. Subsequent to the fermentation step <NUM> is the distillation (and dehydration) step <NUM>, which utilizes a still to recover the alcohol.

Finally, a centrifugation step <NUM> involves centrifuging the residuals produced with the distillation and dehydration step <NUM>, i.e., "whole stillage", in order to separate the insoluble solids ("wet cake") from the liquid ("thin stillage"). The liquid from the centrifuge contains about <NUM>% to <NUM>% DS. The "wet cake" includes fiber, of which there generally are three types: (<NUM>) pericarp, with average particle sizes typically about <NUM> to <NUM>; (<NUM>) tricap, with average particle sizes about <NUM> micron; (<NUM>) and fine fiber, with average particle sizes of about <NUM> microns. There may also be proteins with a particle size of about <NUM> microns to about <NUM> microns.

The thin stillage typically enters evaporators in an evaporation step <NUM> in order to boil or flash away moisture, leaving a thick syrup which contains the soluble (dissolved) solids (mainly protein and starches/sugars) from the fermentation (<NUM> to <NUM>% dry solids) along with residual oil and fine fiber. The concentrated slurry can be sent to a centrifuge to separate the oil from the syrup in an oil recovery step <NUM>. The oil can be sold as a separate high value product. The oil yield is normally about <NUM>/m<NUM> (about <NUM> lb/bu) of corn with high free fatty acids content. This oil yield recovers only about <NUM>/<NUM> of the oil in the corn, with part of the oil passing with the syrup stream and the remainder being lost with the fiber/wet cake stream. About one-half of the oil inside the corn kernel remains inside the germ after the distillation step <NUM>, which cannot be separated in the typical dry grind process using centrifuges. The free fatty acids content, which is created when the oil is heated and exposed to oxygen throughout the front and back-end process, reduces the value of the oil. The (deoil) centrifuge only removes less than <NUM>% because the protein and oil make an emulsion, which cannot be satisfactorily separated.

The syrup, which may have more than <NUM>% oil, can be mixed with the centrifuged 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 step <NUM> and sold as Distillers Dried Grain with Solubles (DDGS) to dairy and beef feedlots. This DDGS has all the corn and yeast protein and about <NUM>% of the oil in the starting corn material. But the value of DDGS is low due to the high percentage of fiber, and in some cases the oil is a hindrance to animal digestion and lactating cow milk quality.

Further, with respect to the liquefaction step <NUM>, <FIG> is a flow diagram of various typical liquefaction processes that define the liquefaction step <NUM> in the dry grind process <NUM>. Again, the dry grind process <NUM> begins with a grinding step <NUM> in which dried whole corn kernels are passed through hammer mills or similar milling systems such as roller mills, disc mill, flaking mills, impacted mill, or pin mills for grinding into meal or a fine powder. The grinding step <NUM> is followed by the liquefaction step <NUM>, which itself includes multiple steps as is discussed next.

Each of the various liquefaction processes generally begins with the ground grain or similar material being mixed with cook and/or backset water, which can be sent from evaporation step <NUM> (<FIG>), to create a slurry at slurry tank <NUM> whereat a commercial enzyme called alpha-amylase is typically added (not shown). The pH can be adjusted here, as is known in the art, to about <NUM> to <NUM> and the temperature maintained between about <NUM> to <NUM> so as to allow for the enzyme activity to begin converting the insoluble starch in the slurry to soluble liquid starch. Other pH ranges, such as from pH <NUM> to <NUM>, may be utilized, and an acid treatment system using sulfuric acid, for example, can be used as well for pH control and conversion of the starches to sugars.

After the slurry tank <NUM>, there are normally three optional pre-holding tank steps, identified in <FIG> as systems A, B, and C, which may be selected depending generally upon the desired temperature and holding time of the slurry. With system A, the slurry from the slurry tank <NUM> is subjected to a jet cooking step <NUM> whereat the slurry is fed to a jet cooker, heated to about <NUM>, held in a U-tube or similar holding vessel for about <NUM> to about <NUM>, then forwarded to a flash tank. In the flash tank, the injected steam flashes out of the liquid stream, creating another particle size reduction and providing a means for recovering the injected stream. The jet cooker creates a sheering force that ruptures the starch granules to aid the enzyme in reacting with the starch inside the granule and allows for rapid hydration of the starch granules. It is noted here that system A may be replaced with a wet grind system. With system B, the slurry is subjected to a secondary slurry tank step <NUM> whereat the slurry is maintained at a temperature from about <NUM> to <NUM> for about <NUM> to about <NUM> hour. With system C, the slurry from the slurry tank <NUM> is subjected to a secondary slurry tank - no steam step <NUM>, whereat the slurry from the slurry tank <NUM> is sent to a secondary slurry tank, without any steam injection, and maintained at a temperature of about <NUM> to <NUM> for about <NUM> to <NUM> hours. Thereafter, the slurry from each of systems A, B, and C is forwarded, in series, to first and second holding tanks <NUM> and <NUM> for a total holding time of about <NUM> minutes to about <NUM> hours at temperatures of about <NUM> to <NUM> to complete the liquefaction step <NUM>, which then is followed by the saccharification and fermentation steps <NUM> and <NUM>, along with the remainder of the process <NUM> of <FIG>. While two holding tanks are shown here, it should be understood that one holding tank, more than two holding tanks, or no holding tanks may be utilized.

In today's typical grain to biochemical plants (e.g., corn to alcohol plants), many systems, particularly dry grind systems, process the entire corn kernel through fermentation and distillation. Such designs require about <NUM>% more front-end system capacity because there is only about <NUM>% starch in corn, with less for other grains and/or biomass materials. Additionally, extensive capital and operational costs are necessary to process the remaining non-fermentable components within the process. By removing undesirable, unfermentable components prior to fermentation (or other reaction process), more biochemical, biofuel, and other processes become economically desirable.

<CIT> discloses a dry grind ethanol production process and system with front end milling method. <CIT> discloses a dry grind system and method for producing a sugar stream from grains or similar carbohydrate sources and/or residues, such as for biofuel production. <CIT> discloses a combination corn and sugar cane processing plant and systems and processes for producing alcohol thereat.

It thus would be beneficial to provide an improved dry milling system and method that produces a sugar stream, such as for biochemical production, that may be similar to the sugar stream produced by conventional wet corn milling systems, but at a fraction of the cost and generate additional revenue from high value by-products, such as oil, protein, and/or fiber, for example, with desirable yield.

The present invention provides for a dry milling system and method that produces a sugar stream, such as for biochemical production, that may be similar to the sugar stream produced by conventional wet corn milling systems, but at a fraction of the cost, and generate additional revenue from high value by-products, such as oil, protein and/or fiber, for example, with desirable yield.

The method and system according to the present invention are described in the claims.

In one embodiment, a method for producing a sugar stream is provided. The method is defined in claim <NUM> and includes, among others, mixing ground grain particles with a liquid to provide a slurry, then separating the slurry into an initial solids portion and an initial liquid portion. The method further includes subjecting the initial solids portion to liquefaction to provide a first liquefied starch solution including starch and subjecting at least a portion of the initial liquid portion to a separate liquefaction step to provide a second liquefied starch solution including starch. Thereafter, the second liquefied starch solution is subjected to saccharification to convert the starch to simple sugars and produce a saccharified stream including the simple sugars. And after saccharification of the initial liquid portion but prior to further processing of the simple sugars, the saccharified stream is separated into a solids portion and a liquid portion including the simple sugars, wherein the separated liquid portion from the saccharified stream defines a sugar stream having a dextrose equivalent of at least <NUM> DE and a total unfermentable solids fraction that is less than or equal to <NUM>% of a total solids content. In one example, the method can further include subjecting the first liquefied starch solution to a separate saccharification step from the initial liquid portion to convert the starch in the first liquefied starch solution to simple sugars and produce a saccharified stream including the simple sugars for further processing.

In another embodiment, a system for producing a sugar stream is provided. The system according to the present invention is defined in the claims and includes, among others, a slurry tank in which ground grain particles mix with a liquid to provide a slurry. A solid/liquid separation device is situated after the slurry tank and receives the slurry and separates the slurry into an initial solids portion and an initial liquid portion. A first liquefaction system is situated after the solid/liquid separation device and receives the initial solids portion to provide a first liquefied starch solution including starch. A second liquefaction system is situated after the solid/liquid separation device and receives the initial liquid portion to provide a second liquefied starch solution including starch. A first saccharification system is situated after the first liquefaction system and receives the first liquefied starch solution to convert the starch to simple sugars and produce a first saccharified stream including the simple sugars. A second saccharification system is situated after the second liquefaction system and receives the second liquefied starch solution to convert the starch to simple sugars and produce a second saccharified stream including the simple sugars. A sugar separation device is situated after the second saccharification system and receives and separates the second saccharified stream into a solids portion and a liquid portion including the simple sugars, wherein the separated liquid portion from the second saccharified stream defines a sugar stream having a dextrose equivalent of at least <NUM> DE and a total unfermentable solids fraction that is less than or equal to <NUM>% of a total solids content.

The features and objectives of the present invention will become more readily apparent from the following Detailed Description taken in conjunction with the accompanying drawings.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, with a detailed description of the embodiments given below, serve to explain the principles of the invention.

<FIG> and <FIG> have been discussed above and represent flow diagrams of a typical wet mill and dry grind alcohol production process, respectively. <FIG>, likewise, has been discussed above and represents various typical liquefaction processes in a typical dry grind alcohol production process.

<FIG> illustrates an embodiment of a dry grind system and method <NUM> for producing a sugar stream from grains or similar carbohydrate sources and/or residues, such as for biochemical production, in accordance with the present invention. As further discussed in detail below, a sugar/carbohydrate stream, which includes a desired Dextrose Equivalent (DE) where DE describes the degree of conversion of starch to dextrose (a. glucose) and/or has had removed therefrom an undesirable amount of unfermentable components can be produced after saccharification and prior to fermentation (or other sugar utilization/conversion process), with such sugar stream being available for biochemical production, e.g., alcohol production, or other processes. In other words, sugar stream production and grain component separation occurs on the front end of the system and method <NUM>.

For purposes herein, in one example, the resulting sugar stream that may be desirable after saccharification, but before fermentation, such as for use in biochemical production, can be a stream where the starch/sugars in that stream define at least a <NUM> DE and/or where the total insoluble (unfermentable) solids fraction of the stream is less than or equal to <NUM>% of the total solids content in the stream. In other words, at least <NUM>% of the total starch/sugar in that stream is dextrose and/or no greater than <NUM>% of the total solids in that stream includes non-fermentable components. In another example, the sugar stream may define at least <NUM> DE. In another example, the resulting sugar stream may define at least <NUM> DE. In yet another example, the starch/sugars in the stream can define at least a <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> DE. In another example, the total insoluble (unfermentable) solids fraction of the stream is less than or equal to <NUM>% of the total solids content in the stream. In another example, the total insoluble (unfermentable) solids fraction of the stream is less than or equal to <NUM>%. In still another example, the total insoluble (unfermentable) solids fraction of the stream is less than or equal to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%. In other words, the total fermentable content (fermentable solids fraction) of the stream may be no more than <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% of the total solids content in the stream. In another example, on a dry mass basis, the weight % fermentable material in the sugar stream that may be desired is greater than or equal to <NUM>%. In another example, on a dry mass basis, the weight % fermentable material in a sugar stream is greater than or equal to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%.

In addition, although the system and method <NUM> described herein will generally focus on corn or kernel components, virtually any type of grain, whether whole and fractionated or any carbohydrate source, including, but not limited to, wheat, barley, sorghum, rye, rice, oats, sugar cane, tapioca, cassava, pea, or the like, as well as other biomass products, can be used. And broadly speaking, it should be understood that the entire grain or biomass or less than the entire grain, e.g., corn and/or grit and/or endosperm or biomass, may be ground and/or used in the system and method <NUM>.

With further reference now to <FIG>, in this dry grind system and method <NUM>, grains such as corn and/or corn particles, for example, can be subjected to an optional first grinding step <NUM>, which involves use of a hammer mill, roller mill, pin mill, impact mill, flaking mill, or the like, either in series or parallel, to grind the corn and/or corn particles to particle sizes less than about <NUM> (about <NUM>/<NUM> inch) or, in another example, less than about <NUM> (about <NUM>/<NUM> inch) and allow for the release of oil therefrom to define free oil. In one example, the screen size for separating the particles can range from about <NUM> (about <NUM>/<NUM> inch) to about <NUM> (about <NUM>/<NUM> inch). In another example, the resulting particle sizes are from about <NUM> microns to about <NUM>. The grinding also helps break up the bonds between the fiber, protein, starch, and germ. In one example, screen size or resulting particle size may have little to no impact on the ability to separate the sugar from the remaining kernel or similar raw material component(s). If the carbohydrate source is pre-ground or initially in particulate form, the optional grind step <NUM> may be excluded from the system and method <NUM>.

Next, the ground corn flour can be mixed with backset liquid at slurry tank <NUM> to create a slurry. Optionally, fresh water may be added so as to limit the amount of backset needed here. An enzyme(s), such as alpha amylase, optionally can be added to the slurry tank <NUM> or in a slurry blender (not shown) between the first grinding step <NUM> and the slurry tank <NUM>. The slurry may be heated at the slurry tank <NUM> from about <NUM> (<NUM>°F) to about <NUM> (<NUM>°F) for about <NUM> to about <NUM>. The stream from the slurry tank <NUM> contains about <NUM>/m<NUM> (about <NUM> lb/bu) free oil, about <NUM>/m<NUM> ( about1. <NUM> lb/bu) germ (particle size ranges from about <NUM> microns to about <NUM>), about <NUM>/m<NUM> (about <NUM> lb/bu) grit (particle size ranges from about <NUM> microns to about <NUM>), which can include starch, and about <NUM>/m<NUM> (about <NUM> lb/bu) fiber (particle size ranges from about <NUM> microns to about <NUM>).

The stream from the slurry tank <NUM> next may be subjected to a liquid/solid separation step <NUM> to remove a desired amount of liquids therefrom. The liquid/solid separation step <NUM> can separate a generally liquefied solution (about <NUM>% to about <NUM>% by volume), which includes free oil, protein, and fine solids (which do not need grinding), from heavy solids cake (about <NUM>% to about <NUM>% by volume), which includes the heavier fiber, grit, and germ, which can include bound oil, protein, and/or starch. That is, the liquid/solid separation step <NUM> can separate out at least a portion of the liquefied solution from the heavy solids cake to define an initial liquid portion. In one example, at least a majority or all of the liquefied solution can be separated from the heavy solids cake to provide the initial liquid portion. The liquid/solid separation step <NUM> uses dewatering equipment, e.g., a paddle screen, a vibration screen, screen decanter centrifuge or conic screen centrifuge, a pressure screen, a preconcentrator, a filter press, or the like, to accomplish separation of the solids from the liquid portion. The fine solids can be no greater than <NUM> microns. In another example, the fine solids are no greater than <NUM> microns, which is generally dependent upon the screen size openings used in the liquid/solid separation device(s).

In one example, the dewatering equipment is a paddle screen, which includes a stationary cylinder screen with a high speed paddle with rake. The number of paddles on the paddle screen can be in the range of <NUM> paddle per <NUM> to <NUM> (<NUM> to <NUM> inches) of screen diameter. In another example, the dewatering equipment is a preconcentrator, which includes a stationary cylinder screen with a low speed screw conveyor. The conveyor pitch on the preconcentrator can be about <NUM>/<NUM> to about <NUM>/<NUM> of the screen diameter. The number of paddles on the paddle screen and the conveyor pitch on the preconcentrator can be modified depending on the amount of solids in the feed. The gap between the paddle screen and paddle can range from about <NUM> to about <NUM> (about <NUM> to about <NUM> inch). A smaller gap gives a drier cake with higher capacity and purer fiber but loses more fiber to filtrate. A larger gap gives a wetter cake with lower capacity and purer liquid (less insoluble solid). The paddle speed can range from <NUM> to <NUM> RPM. In another example, the paddle speed can range from <NUM> to <NUM> RPM. A higher speed provides higher capacity but consumes more power. One suitable type of paddle screen is the FQ-PS32 paddle screen, which is available from Fluid-Quip, Inc. of Springfield, Ohio.

The screen for the dewatering equipment can include a wedge wire type with slot opening, or a round hole, thin plate screen. The round hole screen can help prevent long fine fiber from going through the screen better than the wedge wire slot opening, but the round hole capacity is lower, so more equipment may be required if using round hole screens. The size of the screen openings can range from about <NUM> microns to about <NUM> microns. In another example, the screen openings can range from <NUM> to <NUM> microns. In yet another example, the screen openings can range from <NUM> to <NUM> microns. Smaller screen openings tend to increase the protein/oil/alcohol yield with higher equipment and operation cost, whereas larger screen openings tend to lower protein/oil/alcohol yield with less equipment and operation cost.

The wet cake or dewatered initial solids portion at the liquid/solid separation step <NUM> (about <NUM>% to about <NUM>% water), along with any remaining portion of the liquefied solution, next may be subjected to an optional second grinding/particle size reduction step <NUM>, which may involve use of a disc mill, hammer mill, a pin or impact mill, a roller mill, a grind mill, or the like, to further grind the corn particles to particle sizes less than about <NUM> microns and allow for additional release of oil and protein/starch complexes therefrom. In another example, the particle sizes are from about <NUM> microns to about <NUM>. The grinding further helps continue to break up the bonds between the fiber, protein, and starch and facilitates the release of free oil from germ particles. The stream from the second grinding/particle size reduction step <NUM> contains about <NUM>/m<NUM> to about <NUM>/m<NUM> (about <NUM> lb/bu to about <NUM> lb/bu) free oil. After milling, the milled solids, along with any portion of liquefied solution, can be sent on and subjected to a liquefaction step <NUM>, such solids optionally may be mixed with solids from filtration/membrane separation step <NUM>, as described further below.

The liquefaction step <NUM> can include multiple steps as discussed above and shown in <FIG>. In one embodiment, the pH can be adjusted here to about <NUM> to about <NUM> and the temperature maintained between about <NUM> to about <NUM> so as to convert the insoluble starch in the stream to soluble or liquid starch. Other pH ranges, such as from pH <NUM>-<NUM>, may be utilized and an acid treatment system using sulfuric acid, for example, may be used as well for pH control and for conversion of the starches to sugars. The stream may be further subjected to jet cooking whereat the slurry is fed to a jet cooker, heated to about <NUM>, held for about <NUM> to about <NUM>, then forwarded to a flash tank. The jet cooker creates a sheering force that ruptures the starch granules to aid the enzyme in reacting with the starch inside the granule and for hydrating the starch molecules. In another embodiment, the stream can be subjected to a secondary slurry tank whereat steam is injected directly to the secondary slurry tank and the slurry is maintained at a temperature from about <NUM> to about <NUM> for about <NUM> to about one hour. In yet another embodiment, the stream can be subjected to a secondary slurry tank with no steam. In particular, the stream is sent to a secondary slurry tank without any steam injection and maintained at a temperature of about <NUM> to about <NUM> for <NUM> to <NUM> hours. Thereafter, the liquefied slurry may be forwarded to a holding tank for a total holding time of about <NUM> hour to about <NUM> hours at temperatures of about <NUM> to about <NUM> to complete the liquefaction step <NUM>. With respect to the liquefaction step <NUM>, pH, temperature, and/or holding time may be adjusted as desired.

The stream after the liquefaction step <NUM> can have about <NUM>% to about <NUM>% dry solids (DS) content with most of the components contained in the corn kernels, including starches/sugars, protein, fiber, germ, grit, oil, and salts, for example. There generally are three types of solids in the liquefaction stream: fiber, germ, and grit, which can include starch and protein, with all three solids having about the same particle size distribution. The stream from the liquefaction step <NUM> can contain about12. <NUM>/m<NUM> (about <NUM> lb/bu) free oil, about <NUM>/m<NUM> (about <NUM> lb/bu) germ particle (size ranges from less about <NUM> microns to about <NUM>), about <NUM>/m<NUM> (about <NUM> lb/bu) protein (size ranges from about <NUM> microns to about <NUM>), and about <NUM>/m<NUM> (about <NUM> lb/bu) fiber (particle size ranges from about <NUM> microns to about <NUM>). The stream from the liquefaction step <NUM> can be sent to the saccharification/fermentation step <NUM> and processed as further discussed below.

Returning now to the separated liquid portion or liquefied starch solution of the liquid/solid separation step <NUM>, the initial liquid portion can be sent on and subjected to an optional second liquefaction step <NUM>. In one example, a portion of the initial liquid portion can be sent to and subjected to liquefaction step <NUM> instead of being subjected to second liquefaction step <NUM>. Like liquefaction step <NUM>, second liquefaction step <NUM> can include multiple steps as discussed above and shown in <FIG>.

The stream from the second liquefaction step <NUM> can be sent to an optional saccharification step <NUM> whereat the starches, including complex carbohydrate and oligosaccharides, can be further broken down into simple sugar molecules (i.e., dextrose) to produce a saccharified mash. In particular, at the saccharification step <NUM>, the stream may be subjected to a two-step conversion process. The first part of the cook process, in one example, includes adjusting the pH to about <NUM> to about <NUM>, with the temperature being maintained between about <NUM> to about <NUM> for <NUM> to <NUM> hours to further convert the insoluble starch in the slurry to soluble starch, particularly dextrose. In another example, the pH can be adjusted to about <NUM> to <NUM> or <NUM>, for example. In another example, the temperature can be maintained at <NUM> for about <NUM> hours. Also, an enzyme, such as alpha-amylase, may be additionally added here. In one example, the amount of alpha-amylase may be from about <NUM> wt% to about <NUM> wt% of the slurry stream. In another example, the amount of alpha-amylase may be from about <NUM> wt% to about <NUM> wt% of the total stream.

The second part of the cook process, in one example, may include adjusting the pH to about <NUM> to <NUM>, with the temperature being maintained between about <NUM> to about <NUM> for about <NUM> minutes to about <NUM> hours so as to further convert the insoluble starch in the slurry to soluble starch, particularly dextrose. In another example, the pH can be <NUM>. In another example, the temperature can be maintained from about <NUM> (<NUM>°F) to about <NUM> (<NUM>°F) for about <NUM> hours or up to about <NUM> hours. An enzyme, such as glucoamylase, also may be added here. In one example, the amount of glucoamylase may be from about <NUM> wt% to about <NUM> wt% of the stream. In another example, the amount of glucoamylase may be from about <NUM> to about <NUM> wt% of the stream. Other enzymes or similar catalytic conversion agents may be added at this step or previous steps that can enhance starch conversion to sugar or yield other benefits, such as fiber or cellulosic sugar release, conversion of proteins to soluble proteins, or the release of oil from germ.

A saccharified sugar stream having a density of about <NUM> grams/cc to about <NUM> grams/cc can result here. At this point, the saccharified sugar stream may be no less than about <NUM> DE. In another example, the saccharified sugar stream may be no less than <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> DE. In this example, the saccharified sugar stream may not be considered desirable or "clean" enough, such as for use in biochemical (e.g., biofuel) production, because the total fermentable content of the stream may be no more than <NUM>% of the total solids content in the stream. In this example, the saccharified sugar stream can have a total solids fraction of about <NUM>% to about <NUM>%, such solids including sugar, starch, fiber, protein, germ, oil, and ash, for example. In yet another example, the total fermentable content of the stream is no more than <NUM>, <NUM>, <NUM>, <NUM>, <NUM>% or <NUM>% of the total solids content in the stream. The remaining solids are fiber, protein, oil, and ash, for example. The stream from the saccharification step <NUM> contains about <NUM>/m<NUM> to about <NUM>/m<NUM> (about <NUM> lb/bu to about <NUM> lb/bu) free oil.

After the saccharification step <NUM> (but before any potential fermentation or processing of the sugar stream), so as to provide a more desirable sugar stream, the saccharified sugar stream can be subjected to a sugar separation step <NUM>, which can include a cyclone, decanter, disc centrifuge, rotary vacuum filter, microfilter/microfiltration, membrane filtration, ultrafiltration, precoat/diatomaceous earth filter, or the like, to produce a more desirable sugar stream, which may be considered a purified or refined sugar stream, by further separating out any remaining insoluble components, color, ash, minerals, or the like. In one example, the filter screen size here may be from about <NUM> micron to about <NUM> microns. In another example, the filter screen size may be from about <NUM> microns to about <NUM> microns. Due to the input of water, the sugar stream can have a total solids fraction of <NUM>-<NUM>%. In this example, the sugar stream here may be considered purified or refined enough because the total insoluble (unfermentable) solids fraction of the stream is less than <NUM>%. In another example, the total insoluble (unfermentable) solids fraction of the stream is less than or equal to <NUM>%. In another example, the total insoluble (unfermentable) solids fraction of the stream is less than or equal to <NUM>%. In another example, the total insoluble (unfermentable) solids fraction of the stream is less than or equal to <NUM>%. In still another example, the total insoluble (unfermentable) solids fraction of the stream is less than or equal to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%.

The sugar separation step <NUM> may be replaced by, or additionally include, a cyclone, a decanter, a disc centrifuge, ultrafiltration, carbon column color removal, filter press, flotation, adsorption, and/or demineralization technologies (e.g., ion exchange), either in series or parallel. Resin refining, which includes a combination of carbon filtration and demineralization in one step, can also be utilized for refining the sugars. Additionally, due to a low solids content of the sugar stream here, an optional evaporation step (not shown) may be added hereafter to further concentrate the total solids fraction.

The sugar stream from the sugar separation step <NUM> can be sent on to a further processing step, such as a fermentation step where the sugars are converted, e.g., via a fermenter, to alcohol, such as ethanol or butanol or any other fermentation conversion process or similar sugar utilization/conversion process, followed by distillation and/or separation of the desired component(s) (not shown), which can recover the alcohol or byproduct(s)/compound(s) produced, as is known in the art. The sugar stream can allow for recovery of a fermentation agent from the fermentation step. The fermentation agent can be recovered by means known in the art and can be dried as a separate product or, for example, can be sent to a protein separation step or other streams/steps, in the system and method <NUM>, which can allow for capture of the fermentation agent and/or used for further processing. Fermentation agent (such as yeast or bacteria) recycling can occur by use of a clean sugar source. Following distillation or desired separation step(s), the system and method <NUM> can include any back end type process(es), which may be known or unknown in the art to process, for example, the whole stillage. The fermentation step may be part of an alcohol production system that receives a sugar stream that is not as desirable or clean, i.e., "dirtier," than the sugar stream being sent and subjected to the same fermentation step as the dirty sugar stream. Other options for the sugar stream, aside from fermentation, can include further processing or refining of the glucose to fructose or other simple or even complex carbohydrates, processing into feed, microbe-based fermentation (as opposed to yeast based) and other various chemical, pharmaceutical or nutraceutical processing (such as propanol, isobutanol, citric acid or succinic acid), and the like. Such processing can occur via a reactor, including, for example, a catalytic or chemical reactor. In one example, the reactor is a fermenter.

Still referring to <FIG>, at least a portion of the solid or heavy components (raffinate) from the sugar separation step <NUM> may be sent to the liquefaction step <NUM>, and combined and processed with the stream from the second grinding step <NUM>, as discussed above, and/or can be combined together with the stream from the liquefaction step <NUM> and sent to saccharification/fermentation step <NUM>. These heavier components or underflow from the sugar separation step <NUM>, can be more concentrated in total solids, at about <NUM>% with a potential range of <NUM>-<NUM>%.

Concerning now the saccharification/fermentation step <NUM>, although illustrated in a single box and as would be understood, saccharification and fermentation may occur separately here, in order, or may occur simultaneously. Both processes, i.e., saccharification and fermentation, are described in detail above. Generally, the stream from the liquefaction step <NUM>, alone or combined with the solids from the sugar separation step <NUM>, can be subjected to saccharification whereat complex carbohydrate and oligosaccharides can be further broken down into simple molecules (i.e., dextrose) to produce a saccharified mash. With fermentation, the glucose sugars are metabolized into ethanol and CO<NUM>. Other options for the solids stream, aside from fermentation in the saccharification/fermentation step <NUM>, can include further processing or refining of the solids into feed, microbe based fermentation (as opposed to yeast based) and other various chemical, pharmaceutical or nutraceutical processing (such as propanol, isobutanol, citric acid or succinic acid), and the like. Such processing can occur via a reactor, which can include a fermenter.

The saccharification/fermentation step <NUM> is followed by distillation <NUM>. At the distillation tower, the fermented solution is separated from the stillage, which includes fiber, protein, and germ particles, to produce alcohol. The fiber can be separated from the germ particles and protein (gluten) at a fiber/protein separation step <NUM> by differences in particle sizes using a screen device, such as a filtration centrifuge, a filtration decanter, a paddle screen, a pressure screen, or the like to remove the fiber therefrom. The screen openings normally will be about <NUM> microns to capture amounts of tipcap, pericarp, as well as fine fiber, but can range from about <NUM> microns to about <NUM>,<NUM> microns. The separated fiber is used to produce a low protein (less than about <NUM>%)/low oil (less than about <NUM>%) DDG.

If a lower protein and oil content in the fiber is needed or desired, the fiber may be sent to a holding tank (not shown), for example, whereat the pH of the separated fiber can be adjusted to about <NUM> to about <NUM> (or about <NUM> to about <NUM>), such as by the addition of chemicals, e.g., sodium hydroxide, lime, sodium carbonate, trisodium phosphate, or the like to help release additional oil from the germ. Also, cell wall breaking enzymes, e.g., protease, cellulase, hemicellulose, phytase, and the like, and/or chemicals, e.g., sodium sulfite and the like, may be added here to help release additional oil from the germ. In one example, the fiber can be held in the tank for about <NUM> hour at a temperature of about <NUM> (about <NUM>°F) to about <NUM> (about <NUM>°F) (or about <NUM> to about <NUM> (about <NUM>°F to about <NUM>°F)). Thereafter, the fiber can be subjected to a grind step to release more oil and protein from the fiber. The fiber produced by these additional treatment steps can give a much lower oil (less than <NUM>%) and lower protein (less than <NUM>%) and can be used for secondary alcohol production.

The centrate from the fiber/protein separation step <NUM> goes to an evaporator <NUM> to separate any oil therefrom and to produce syrup, which can be mixed with the DDG and dried, as represented by numeral <NUM>, to give the low protein (less than about <NUM>%)/low oil (less than about <NUM>%) DDGS, such as for cows or pigs, particularly dairy cows. The DDGS contains less than about <NUM>% protein, less than about <NUM>% oil, and less than about <NUM>% starch.

In addition, an optional centrifugation step (not shown) may be provided to recover the xanthophyll content in the emulsion layer of the recovered oils, both prior to and after saccharification in the saccharification/fermentation step <NUM>, and mixed with the protein by-product prior to drying to increase the feed value. The overflow from the centrifuge(s) can go back to the oil storage tanks (not shown).

Also, further modifications can be made to the above system and method <NUM> to improve co-product recovery, such as oil recovery using surfactants and other emulsion-disrupting agents. In one example, emulsion-disrupting agents, such as surfactants, or flocculants may be added prior to steps in which emulsions are expected to form or after an emulsion forms in the method. For example, emulsions can form during centrifugation such that incorporation of surfactants prior to or during centrifugation can improve oil separation and recovery. In one example, the syrup stream pre-oil separation can also have emulsion breakers, surfactants, and/or flocculants added to the evaporation system to aid in enhancing the oil yield. This may result in an additional <NUM> to <NUM>/m<NUM> (<NUM> to <NUM> lb/bu) oil yield gain.

Claim 1:
A dry milling method for producing a sugar stream comprising:
dry grinding grain and/or grain components into ground grain particles;
mixing the ground grain particles with a liquid to provide a slurry;
separating the slurry into an initial solids portion and an initial liquid portion,
subjecting the initial solids portion to liquefaction to provide a first liquefied starch solution including starch and subjecting at least a portion of the initial liquid portion to a separate liquefaction step to provide a second liquefied starch solution including starch;
thereafter, subjecting the second liquefied starch solution to saccharification to convert the starch to simple sugars and produce a saccharified stream including the simple sugars; and
after saccharification of the initial liquid portion but prior to further processing of the simple sugars, separating the saccharified stream into a solids portion and a liquid portion including the simple sugars, wherein, prior to separating the saccharified stream into the solids portion and the liquid portion, the separated initial solids remain separate from the saccharified stream of the second liquefied starch solution, and wherein the separated liquid portion from the saccharified stream defines a sugar stream having a dextrose equivalent of at least <NUM> DE and a total unfermentable solids fraction that is less than or equal to <NUM>% of a total solids content.