Claims:We claim:
1. A system for processing a starch based material comprising:
a) a cleaning unit for removing suspended matters from said material forming a clean material;
b) a milling unit for sizing said clean material to a desired particle size forming a flour;
c) a liquefaction unit for liquefying said flour at a desired temperature and pH forming a slurry;
d) a first set of vibratory screening devices for the treatment of said slurry forming a first filtrate stream and a first filtration residue;
e) a slurry tank for mixing hot water into said first filtration residue;
f) a second set of vibratory screening devices for the treatment of said first filtrate residue forming a second filtrate stream and a second filtration residue;
g) a screw press for pressing said second filtrate residue forming a third filtrate stream and residual solids; and
h) Collecting and using said first, second and third filtrate streams for preparation of ethanol by fermentation.
2. The system of claim 1, wherein said starch based material comprises one of cassava, corn, millet, rice, oat, wheat, barley, triticale, buckwheat, rye, manioc, tapioca, sorghum, potatoes, or combinations thereof.
3. The system of claim 1, wherein third stream and a portion of second filtrate stream is recycled to said liquefaction unit forming said slurry.
4. The system of claim 1, wherein the slurry containing about 25% to about 34% solids by weight.
5. The system of claim 1, wherein the liquefaction enzyme and viscosity reducing enzyme is added of about 0.6 kg to about 0.9 kg per ton and about 0.2 kg to about 0.4 kg per ton of the convertible starch respectively.
6. The system of claim 1, wherein the starch-based material is liquefied at a temperature of about 50oC to about 90oC and at pH of about 4.5 to about 6.5.
7. The system of claim 1, wherein a mesh size of the vibratory screening devices is in a range of about 80 microns to about 350 microns.
8. The system of claim 1, wherein said suspended matters comprises sand, filler material, fibers, or combinations thereof.
9. The system of claim 1, wherein sand separation efficiency of the system is about 75% to about 90%.
10. The system of claim 1, wherein said residual solids are used as fertilizer, animal feed or fuel material.
, Description:FIELD OF INVENTION
A method for processing a starch-based material is provided. The method includes liquefying the starch-based material in presence of a liquefaction enzyme to form a slurry and screening the slurry via one or more vibratory screening devices to form a first filtrate stream and a first filtration residue. The method includes mixing the first filtration residue with water to form an intermediate slurry and screening the intermediate slurry via one or more vibratory screening devices to form a second filtrate stream and a second filtration residue. The method also includes forming a fresh slurry using the second filtrate stream and optionally a portion of the first filtrate stream. The method also includes sterilizing and cooling first and second filtrate streams, and fermenting the cooled streams to form a fermentation product.
BACKGROUND
A variety of starch-based materials such as broken rice, corn, millets, cassava chips, tubers, oats etc are subjected to liquefaction and fermentation to produce various products through known bioprocesses. Such products include alcohols such as beverage grade and fuel grade ethanol, high fructose/ glucose syrups and its derivatives, organic acids and bio oils, among others. Alcohols are employed as a solvent for a wide range of industrial products such as paints, lacquers, dyes and oils.
The cassava flour is one of the starch based materials which is utilized for alcohol production due to its high starch content resulting in high fermentable sugars and a stable shelf life. However, the cassava (chips or tubers) raw material contains suspended matter such as sand, fiber/filler material and peels in significant amounts, that cause erosion of the process equipment such as stationary and rotary components, piping, fittings and other instrumentation used in the pretreatment and fermentation, distillation and solid-liquid separator operations. It is therefore desirable to separate and remove such suspended matter from the starch based materials to improve the process efficiency and durability of the plants.
One way of separating such suspended matter from the starch-based material is through duplex strainers. Typically, a duplex strainer includes two filtration chambers for filtering the starch-based materials. However, the strainers employed in the system are required to be replaced manually once they are blocked. Moreover, these strainers have substantially low sand separation efficiency and also result in loss of starch along with sand and fibers.
Another way of separating the suspended matter is through gravity settling tanks, where trough or settling tanks are employed to separate sand and other suspended matters from the starch-based materials. Unfortunately, only heavy sand is settled and separated through this technique and other suspended matters such as peels are not separated. Again, such systems also result in loss of starch along with the sand.
Some systems utilize hydrocyclone/ decantation separators that separate sand and other suspended matters based upon density variations. However, such systems again have erosion issues and are susceptible to loss of starch along with sand separation.
Although there are different method for sand separation, there exists a need to find a system for separating suspended matters from starch-based materials to avoid starch loss along with suspended matter and system erosion.

DESCRIPTION OF DRAWINGS
The features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, wherein:
FIGURE 1 illustrates an exemplary flow diagram of steps of the system for processing a starch-based material in accordance with aspects of the present invention.
FIGURE 2 illustrates a system for processing a starch-based material in accordance with aspects of the present invention.
DETAILED DESCRIPTION
As disclosed herein, embodiments of the present technique function to provide a system for separating or cleaning suspended matters (including organic and inorganic matters) such as sand, filler materials/ fibers and peels from a starch-based material.
In one embodiment of the disclosed invention, processing a starch-based material is illustrated in FIGURE 1; a starch-based material is received from a storage unit. An open yard (covered/un-covered) or silos may be used to store the starch-based material at ambient temperature. The starch-based material includes tubers, roots, whole grain, grits or flour, or combinations thereof. In one exemplary embodiment of the present invention, the starch-based material includes, but is not limited to, cassava, corn, millet, rice, oat, wheat, barley, buckwheat, rye, triticale, manioc, tapioca, sorghum (all variants), potatoes, or combinations thereof. The said starch-based material is cleaned to remove foreign particles. Further, said cleaned starch-based material is subjected to milling operation to form starch-based material of desired particle size. In one exemplary embodiment, a plurality of hammer mills may be employed to convert the raw material into a flour of desired particle size. Then said flour is further mixed with a water stream to form slurry. In certain embodiment, recycled water streams from a downstream process may be utilized to form the slurry. Then said slurry is then liquefied in the presence of liquefaction enzymes [like amylases, glucoamylases, etc] to hydrolyse convertible starch in the raw material to dextrin and glucose. In this exemplary embodiment, the liquefaction enzymes include an alpha-amylase enzyme. The liquefaction of the starch-based material may be performed at a desired temperature and pH. In this embodiment, the liquefaction process to form slurry is carried on at a temperature in a range of between about 50 ºC and about 90 ºC. Moreover, the pH is maintained in the range of about 4.5 to about 6.5. In one exemplary embodiment, caustic solution is utilized to maintain the pH levels during the liquefaction process. In another exemplary embodiment, a viscosity reducing enzyme is utilized to reduce the viscosity during the liquefaction process. Examples of viscosity reducing enzymes include beta glucananses, arabino xylanases, pectinases, cellulases, hemicellulases and proteases, among others. Then said slurry is screened via one or more vibratory screening devices to form a first filtrate stream and a first filtration residue. It should be noted that a number and a size of the one or more vibratory screening devices is based upon a desired quantity of the fermentation product to be produced. For example, the mesh size and the angle of the vibratory screening devices may be selected based upon composition of the raw material used, particle size distribution of the flour and sand and other suitable parameters. The first filtration residue includes sand, fiber, and peels as suspended matters. The first filtration residue also includes water, other dissolve solids and dextrin as dissolved solids. Then said first filtration residue is mixed with hot water to form an intermediate slurry in a suitable tank with a mixing device. The intermediate slurry is further screened via one or more vibratory screening devices to form a second filtrate stream and a second filtration residue. The second filtration residue further subjected to separation of remaining suspended matters. The remaining solids as a third stream is subjected to a screw pressing to remove water [third filtrate stream] and solids [residual solids] are collected for use as a fertilizer, animal feed, fuel, land filling material and for other suitable purposes. The first, second and third filtrate streams are collected together and used for fermentation as the feedstock. It will be appreciated by one skilled in the art the number of processing stages can be lesser or greater based on the desired product composition in filtrate residue.
In another embodiment of the invention, fresh slurry is formed by mixing the second filtrate stream and the flour of the starch-based raw material. In one exemplary embodiment, the second filtrate stream along with a portion of the first filtrate stream is mixed with the starch-based material to form the fresh slurry. In certain embodiments, a mixture of the first, second and third filtrate streams is heated in range of about 90 ºC to about 130 ºC with injection of steam to control contamination of the dextrin solution. Subsequently the streams are cooled using a heat exchanger. Then said cooled stream is fermented further to form a fermentation product such as, but not limited to, beverage grade alcohol, fuel grade alcohol, industrial alcohol and bio oils. The fermentation of the fresh slurry is accomplished by any organism (e.g., yeast) suitable for converting sugars, such as glucose and maltose to the desired fermentation product.
In yet another embodiment of the invention, the number of such screening cycles involving formation of intermediate slurry using filtration residues and screening such slurry may be more dependent upon a variety of factors such as raw material type and composition, a capacity of the production plant producing the fermentation product, desired level of alcohol in the fermentation product, type of the fermentation product and so forth. Moreover, the present technique may also be utilized in combination with other existing systems (e.g., gravity settling tanks and hydroclone /decantor separators) for separating suspended matter from the starch-based material. As technique described above utilizes two sets of vibratory screening devices to separate suspended matter such as sand from the starch-based material.
FIGURE 2 illustrates a system for processing a starch-based material in accordance with aspects of the present invention. As illustrated, the system includes a storage unit which contains the starch-based material. In this exemplary embodiment, the starch-based material comprises cassava chips or tubers. Other starch-based materials include whole grain, flour (dry milled), slurry (dry or wet milled) corn, millet, rice, oat, wheat, barley, triticale, milo, buckwheat, rye, manioc, tapioca, sorghum, and potatoes. Here, the starch-based materials such as cassava chips are cleaned in the cleaning unit. The cleaning unit may include a destoner for removing stones and other foreign particles from the material. Moreover, a magnetic separator may be employed to remove iron or other metallic material. Once the raw material is cleaned, it is subjected to milling operation in a milling section to convert the material into flour such as cassava flour having a desired particle size. A set of hammer mills may be used in the milling section to form the flour having the desired particle size. Yet other suitable milling devices may be used. Alternatively, wet milling may be used in the milling section for milling grains and tubers and to prepare slurry of desired solids concentrations. Then said flour is further processed in a liquefaction unit. The liquefaction unit utilizes fresh hot water streams, or recycled streams from a downstream process for mixing with the cassava flour in a premasher (not shown) of the liquefaction unit. Moreover, fresh steam is introduced into the liquefaction unit for maintaining a desired temperature for the liquefaction process. In this embodiment, the liquefaction process is carried on at a temperature in a range of about 50 ºC to about 90 ºC. Furthermore, the liquefaction unit employs liquefaction enzymes to hydrolyze convertible starch to dextrin that solubilizes in the slurry. In this exemplary embodiment, the liquefaction enzyme is alpha-amylase that is introduced in a dose of about 0.6 kg to about 0.9 kg per ton of the convertible starch.
In certain embodiment of the present invention, caustic solution is introduced in the liquefaction unit to control the pH during the liquefaction process. In this exemplary embodiment, the pH of the solution is maintained in a range of about 4.8 to about 6.5. A viscosity reducing enzyme is introduced into the liquefaction unit in a dose of about 0.2 kg to about 0.4 kg per ton of the convertible starch to reduce the viscosity during the liquefaction process. In this exemplary embodiment, the slurry includes about 25% w/w to about 34% w/w of dry solids. It should be noted that this composition may vary depending on the raw material type and composition as well as desired product concentration in the fermentation. Said system here includes a first set of vibratory screening devices to for separating suspended matters from the slurry. In this exemplary embodiment of the present invention, the cassava chips flour slurry containing the suspended matters is transferred continuously to the first set of vibratory screening devices using a pump and generates a first filtrate stream and a first filtration residue. The first filtrate stream may be stored in a storage tank. The suspended matters may include sand, fibers, filler materials, or combinations thereof. In this exemplary embodiment, the system may include one or more vibratory screening devices for screening the slurry. The system details are shown in FIGURE 2.
The vibratory screening devices are commercially available or may be custom designed depending on the requirements of the system. It should be noted that a number and a mesh size of the vibratory screening devices may be selected based upon a variety of parameters such as type of the starch material, a desired composition of a fermentation product formed by the starch-based material, among others. In this exemplary embodiment, the mesh size of the vibratory screening devices is in a range of about 80 microns to about 350 microns.
The first filtration residue contains fibers, peels and sand as suspended matter while water, other dissolve solids and dextrin as dissolve solids. The first filtration residue is mixed with hot water stream in a slurry tank to form an intermediate slurry. In particular, dextrin available as dissolved solids in the first filtration residue is recovered via the intermediate slurry. Said first filtration residue is further passed through a second set of vibratory screening devices for separating residual suspended matter and generate a second filtrate stream and a second filtration residue. Said second filtration residue is dewatered by a screw press to remove moisture and residual dextrin as a third stream and a suspended matter. Said third stream is subsequently collected in a collection tank. In certain embodiments, stream from screw press may be transferred to a storage tank for reprocessing. The suspended matters are utilized as a fertilizer, animal feed, fuel, land filling material, among other suitable purposes.
In yet another embodiment of present invention, the second filtrate stream is collected in the storage tank. In this embodiment, a portion of the second filtrate stream and third stream is recycled to the liquefaction unit for the liquefaction process to for slurry. The second filtrate stream and optionally a portion of the first filtrate stream are then utilized to form a fresh slurry. In the illustrated embodiment, the first, second and third filtrate streams are sterilized using steam in a sterilization unit. the first ,second and third filtrate streams and. heated to a temperature in a range of about 90 ºC to about 130 ºC for about 5 minutes to about 20 minutes with injection of steam supply for disinfecting the dextrin solution.
In yet another embodiment of present invention, the fresh slurry is formed by mixing cassava chips flour with the second filtrate stream and is cooled in a heat exchanger using cool water supply. Subsequently, the fresh slurry is fermented in a fermentation unit to form a fermentation product such as ethanol.
As described above, the present technique enables suspended matters separation and removal using a series of vibratory screening devices. In one exemplary embodiment, a sand separation efficiency of the system is in a range of about 75% to about 90%. Again, the sand separation efficiency may vary depending on raw material type, composition, milling, particle size distribution etc.
The cassava material contains starch in a range of about 65 % w/w to about 67 % w/w. The material further includes proteins, fats, fibers and peels, sand and water. It is desirable to separate the fibers and peels and sand from the material to increase the overall efficiency of the downstream processes and preventing erosion of the components of the system. The material is liquefied to form a slurry in the presence of the liquefaction agent. Said liquefied slurry provided to the first set of vibratory devices comprises dextrin that is in a range of about 21.5 % w/w to about 22.5 % w/w owing to the liquefaction process. Said slurry further includes reduced quantities of fats, fibers and peels and sand. The slurry is screened with the first set of vibratory devices to form the first filtrate stream and the first filtration residue. The quantity of suspended matter such as fibers and peels, and sand is reduced in the first filtrate stream and is separated via the first filtration residue. Said first filtrate stream includes the fibers and peels in a range of about 0.05% w/w and 0.06% w/w. Moreover, the first filtrate stream includes sand in a range of about 0.1 % w/w and 0.15% w/w. Said first filtration residue includes substantially high quantities of suspended matter separated through the first set of vibratory devices. In the illustrated embodiment, the first filtration residue includes the fibers and peels in a range of about 24 % w/w and 24.5% w/w. Moreover, the first filtration residue includes sand in a range of about 2 % w/w and 2.4% w/w. The first filtration residue is utilized to form an intermediate slurry that is screened through the second set of vibratory devices to form the second filtrate stream and the second filtration residue. The quantity of dextrin in the second filtrate stream is relatively less as compared to the first filtrate stream. The residual suspended matter is separated via the second filtration residue. The residual suspended matter i.e., fibers and peels and sand are separated and removed via the second filtration residue. As previously described, the second filtration residue with the separated suspended matter may be disposed or utilized for suitable uses.
The various aspects of the technique described hereinabove may be used for separating suspended matters from a starch-based material used for producing fermentation products in fermentation plants. In particular, the technique described above utilizes liquefaction and series of screening steps using vibratory screening devices to substantially separate the suspended matter from the starch-based material thereby enhancing overall efficiency of such plants. Advantageously, the technique effectively separates the suspended matter while reducing loss of starch during the separation process.
The technique utilizes motor driven vibratory screening devices that have fewer chances to get clogged thereby requiring minimal manual intervention. Also, the separation and removal of suspended matter minimizes erosion of components of the system thereby facilitating continuity of the manufacturing processes and reducing overall capital and operating/ maintenance costs of the production plants.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.