Abstract:
A process for obtaining a starch and a protein or both from grain flour, the process steps comprising: providing grain flour; mixing the grain flour with processed or fresh water to form a slurry; separating the slurry into it at least two fractions, the at least two fractions including two or more of a heavy A-starch fraction, a protein and B-starch fraction, and a pentosan fraction; and generating a biogas from at least one of the fractions from the separating step, the biogas being used for generating energy.

Description:
[0001]    This application is a National Phase Application based upon and claiming the benefit of priority to PCT/EP2008/051500, filed on Feb. 7, 2008, which is based upon and claims the benefit of priority to German Patent Application No. DE 10 2007 006 483.9, filed on Feb. 9, 2007 the contents of both of which Applications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
     Background and Summary 
       [0002]    The present disclosure relates to a method or process for obtaining a valuable product, such as starch and/or protein, from grain flour. The grain flour may be wheat flour. 
         [0003]    For example, a process for obtaining starch from grain flour, such as wheat flour, according to the state of the art, is illustrated in  FIG. 6 . 
         [0004]    Accordingly, the grain corn, from which the stalks and the chaff were removed, is supplied to a mill for further processing. For example, see Step  100  in  FIG. 6 . 
         [0005]    In the mill, the grain is first slightly moistened, or conditioned, in order to break open the outer hull of the corn and expose the inner parts. The resulting bran, or hull, is separated from the still coarse flour and from the process by sifting. The bran can later be admixed to the created by-products, such as feed products, for example, coagulated protein and thin fibers, or can be partially split or directly burnt for obtaining energy. 
         [0006]    Subsequently, the flour passes through several rolling steps until the necessary fineness of the flour has been reached, as required, by means of intermediate sifting in order to remove additional undesirable parts and ensure the required granulation and yield. Before the processing of the wheat flour to gluten and starch, as well as its by-products, the flour is conditioned by storage. Alternative measures for a conditioning are, for example, ventilation, fluidization or a direct enrichment with oxygen. 
         [0007]    Following the conclusion of the grinding, the finished flour will be mixed with fresh water or process water at a ratio of 0.7 to 1.0 parts relative to 1 part flour for forming a wheat flour slurry which is free of dry flour particles. Subsequently, energy is mechanically fed to the slurry by way of a so-called high-pressure pump or a perforated-disk mixer in order to promote the matrix formation, for example, the cross-linking and agglomeration of the protein fractions for forming the actual wet gluten. Then, the slurry pretreated in this manner reaches a moderately stirred tank in which a dwell time of from 0 to 30 minutes is set. For example, see Step  101  in the Drawings. 
         [0008]    In the next process step, the slurry is diluted again with a defined quantity of water, such as fresh or processed water, at a ratio of 1 part slurry to 0.5 to 1.5 parts water directly in front of the advantageously used 3-phase decanter in a so-called U-tube in the inverse current. In the 3-phase decanter, such as a horizontal centrifuge, the separation of the slurry will then take place mechanically into three different fractions under the influence of centrifugal forces. That is, the heavy A-starch fraction, or the underflow of the decanter, the protein phase and the B-starch phase, or the nozzle phase of the decanter, and the pentosan fraction, such as mucous substances or hemicelluloses. For example, see Step  102  in the Drawings, which is shown as a three-phase separation. The use of other separating processes, such as other centrifuges, is also conceivable according to the present disclosure. 
         [0009]    Because of its special characteristics, such as visco-elasticity, the protein of wheat, also called “gluten”, represents a desired and valuable product which is easily sold in the foodstuff industry, such as, for example, to bakeries and meat or sausage products businesses, the feed product industry, for example, for fish farms and for many technical applications, such as glues and paper coating dyes. 
         [0010]    For obtaining the valuable protein, the nozzle phase from the decanter is first subjected to a sifting at, for example, Steps  201  and  202  in order to separate the gluten from the B-starch. In this sifting step, the fine-grain starch, for example, the B-starch, and the fibers are separated from the gluten. 
         [0011]    For example, starch with a fraction of less than 40% particles of a grain size of less than 10 μm is used here as the A-starch, and a granular starch, in whose fraction the portion of starch corns with a particle diameter of less than 10 μm is greater than 60%, is used as the B-starch. The B-starch product does not necessarily only consist of particles of the above type but may also contain additional constituents, such as a certain fraction of pentosans. 
         [0012]    This sifting is predominantly carried out in 2 steps. In the subsequent process step, the gluten is subjected to a washing, for example, at Step  203 , in order to remove additional enclosed “non-protein particles” as well as undesirable soluble constituents before it is then dehydrated, for example, at Step  204  and dried, for example, at Step  205 . 
         [0013]    The A-starch obtained from the 3-phase separation, like the protein, is further processed in an independent line. 
         [0014]    A safety sifting first takes place at, for example, at Step  301 , in order to remove and recover the smallest gluten particles. 
         [0015]    Subsequently, a further sifting, at, for example, at Step  302 , takes place during which the fiber parts are separated from the A-starch. 
         [0016]    For the concentrating and washing, at, for example at Step  303 , the A-starch is placed in a nozzle or disk separator, such as, for example, a vertical centrifuge. 
         [0017]    Following the concentrating, washing of the A-starch, at, for example, Step  304 , takes place by means of a 5- to 12-step hydrocyclone system or a 1- to 2-step or 3-phase separator line. This occurs before a further process step, for example, at Step  305 , in which the starch is first dehydrated by means of a vacuum filter, a dehydration centrifuge or a decanter and is then dried, at, for example, Step  306 . 
         [0018]    The washed starch may also be subjected to a further treatment, such as a chemical and/or physical modification before the drying. Such further treatment is not illustrated. 
         [0019]    In the course of the concentration in a 3-phase separator, at, for example, Step  303 , the starch is split into two different fractions, such as a heavy coarse-grained starch fraction, called A-starch, and a finer starch fraction. 
         [0020]    The fine-grain starch is carried away by way of the medium phase of the separator and, together with the sifted fine-grain starch from the protein sifting, is carried to an additional separator, at, for example, at Step  402 . In this separator, the possibly sorted large-grain A-starch is recovered and fed back to the A-starch line, while the small-grain B-starch which, in turn, is discharged in the medium phase, is further processed in a “B-starch line”. 
         [0021]    In this processing, the thus separated B-starch is obtained as a further by-product in that it is first dehydrated by means of a decanter, at, for example, Step  403 , and is then dried, at, for example, Step  404 . 
         [0022]    The excess of process water, such as from Step  402  and possibly additional excess process water from other process steps are brought together, for example, at Step  501 . 
         [0023]    Then, liquid is separated from solids remaining in the process water by means of a phase separation, for example, at Step  502 , which solids may then, for example, be dried and be used as feed products, at, for example, Step  504 . 
         [0024]    The dissolved and liquid constituents discharged with the top flow can be moved into an evaporating device, for example, at Step  503 , in which the liquid flow is further concentrated before a further processing takes place, for example, by a biological waste water treatment. The remaining concentrate of the evaporating device is mixed with the bran from the grinding, and is mixed together with the concentrate from the 2-phase separation and is dried, for example, at Step  504 . 
         [0025]    Decanters, self-cleaning separators or 3-phase separators can be used in the phase separation process step  502 . 
         [0026]    Prior art relating to the general technological background, for example, a process for producing a high-protein and high-glucose starch hydrolyzate, is known from German Patent Document DE 41 25 968 A1. German Patent Document DE 196 43 961 A1 describes a use and a system for obtaining proteins from the flour of legumes. German Patent Document 100 21 229 A1 discloses a process for producing protein preparations. 
         [0027]    The present disclosure relates to a further development of this known process such that the economic efficiency is increased. 
         [0028]    The present disclosure thus relates to a process for obtaining a valuable product, such as a starch and/or protein, from grain flour. The steps of the process include: i.) grain flour being mixed with fresh or processed water for forming a slurry; ii.) the slurry is separated into at least two fractions, such as centrifugally into a heavy A-starch fraction, into a protein and B-starch fraction at a nozzle phase of the decanter, and into a pentosan fraction; iii.) biogas is generated from at least one of the fractions obtained during the separation of step ii., which biogas is used for generating energy; and iv.) the fraction used for generating the biogas is subjected to at least one liquefaction step, for example, at Step  505  and one phase separation, for example, at Step  506 , and wherein the biogas is generated from the liquid phase of the phase separation. 
         [0029]    According to illustrative embodiments of the present disclosure, the protein phase is further processed in the protein processing steps for forming a protein product, the A-starch fraction is further processed for forming an A-starch product and biogas is generated from the B-starch. 
         [0030]    In addition, it is expedient for the B-starch with bran and the pentosan fraction from the three-phase separation, at, for example, at Step  102 , to be processed for forming biogas. 
         [0031]    Advantageously, the liquefaction and a phase separation are included in a process of a biogas system, and energy is obtained directly from poly- and oligosaccharides naturally occurring during the starch production. 
         [0032]    The preceding heat treatment and enzymatic treatment, as well as the subsequent separation of the substances, such as proteins, phospholipoproteins, celluloses, which are very difficult to utilize microbiologically, represent a difference with respect to a “conventional” biogas system. 
         [0033]    Overall, it is achieved that a short amount of time is required until the generating of biogas is concluded. As a result of the “splitting” into low-molecular sugars, the latter are easily made accessible to the acid-forming and ethanoic-acid-forming bacteria, for example, these can rapidly metabolize the offered substrate. 
         [0034]    As a result, the required dwell times are low relative to the load in the reactors, and therefore the construction of the latter can be relatively small. A good high value is achieved regarding COD freight. In this manner, an economically and technically controllable and meaningful processing of one or more phases or fractions from the starch production process into biogas easily becomes possible. 
         [0035]    A special advantage is the resulting use of byproducts from obtaining protein and starch for directly generating energy. So far, all products had either been sold directly or had been converted to other products, such as, for example, modification, saccharification, ethanol production. The obtained energy can, in turn, be returned directly into the system. On the one hand, as electric energy and/or, on the other hand, as thermal energy, such as, for engine-based cogeneration system, gas engine, gas turbine. 
         [0036]    The water draining off the methane stage can advantageously be processed in a membrane system that follows. As such, the membranes stressed to a slight degree and high flow rates are obtained. The permeate obtained from the membrane system can be returned as process water into the system. 
         [0037]    Concerning the background of biogas systems, reference is made to Konstandt, H. G. (1976) “Engineering, Operation and Economics of Methane Gas Fermentation”, Göttingen: Microbiol. Energy Conservation Seminar, and to Kleemann, M. &amp; Meliβ, M. (1993), “Regenerative Energy Sources”, Second, completely revised edition, Berlin, Springer, which should also be used as an example with respect to numerical data of the specification. Reference is also made to German Patent Document DE 103 27 954 A1 which describes a process for producing ethanol from a biomass. German Patent Document DE 198 29 673 A1 suggests the treatment of waste water from oil seed and grain processing of rape, sunflower or olive oils, the separating of the solids and the utilizing of these solids for obtaining biogas. 
         [0038]    Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]      FIGS. 1 to 5  are diagrams of different embodiments of a process according to the present disclosure. 
           [0040]      FIG. 6  is a diagram of a process according to the state of the art. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    Analogous to  FIG. 6 , the processing of the grain and of the resulting flour respectively in Steps  100  to  102 ,  201  to  205  and  301  to  306  can take place in the manner shown in  FIG. 6  or in the above-described process steps. 
         [0042]    However, in contrast to  FIG. 6 , according to illustrative embodiments of the process of  FIGS. 2 to 5 , when the process is carried out, the B-starch is not obtained directly as a product but brought together with the substance flows from the 3-phase separation of: Step  102 , the pentosans; the fiber sifting of Step  302  and possibly Step  401  as shown in, for example,  FIGS. 1-5 ; the excess process water of Step  501 ; the bran from the grinding of Step  100 ; and, as a mixture, is subjected to a liquefaction at Step  505 . 
         [0043]    As illustrated, as an example, in  FIG. 1 , different substance flows from the process are brought together in the liquefaction at Step  505 . 
         [0044]    These are the pentosan fraction from Step  102  and the excess of process water, such as from Step  402  and starch recovery, as well as possibly additional process water excess from other process steps. 
         [0045]    In the liquefaction at Step  505 , the substances contained in the flows fed into the liquefaction are subjected to an enzymatic as well as to a thermal treatment in order to split the remaining macromolecular carbon compounds, such as starch, celluloses, and hemicelluloses, into smaller units and to coagulate and precipitate the remaining protein. 
         [0046]    For the splitting of the macromolecular carbohydrates and the subsequent saccharification, various enzymes, such as cellulases, for example, Genencor 220 and SPEZYME FRED, for example, Genencor, are added which become effective at different temperature ranges. The temperature ranges may be, for example, I: 40° C.-60° C., or 45° C.-55° C., or 50° C., and II: 80° C.-95° C., or 85° C.-95° C., or, 90° C. During this step-by-step temperature treatment, the proteins are denatured in a parallel manner and precipitate together with the fine fibers and phospholipoproteins as a so-called protein coagulate. 
         [0047]    Together with this coagulate, phosphorus, sulfur and nitrogen compounds are also precipitated, which microbiologically can be reduced only with difficulty and over an extended period of time. The separation of these substances is advantageous for a good efficiency of the biogas system, as well as for the splitting of poly- and oligosaccharides into low-molecular compounds. 
         [0048]    Another advantage, according to the process of present disclosure, is the possibility of a good processing of the remaining waste water from the methane reactor to process water in a membrane filtration system because the danger of clogging the membranes is rather low. 
         [0049]    In the subsequent process step of the phase separation, for example, at Step  506  using, for example, a decanter, self-cleaning separator or 3-phase separator, the thus precipitated solid constituents will then be separated from the liquid phase. 
         [0050]    In such a case, the solids are the residual solid constituents which could not be influenced by the enzymes and heat, as well as the coagulated proteins and phospholipoproteins, such as protein coagulate. 
         [0051]    This dehydrated mass can be further utilized as a feed product, a fertilizer or a combustion material, as suggested at Step  507 . 
         [0052]    Simultaneously, the content of P-, N- and S-compounds is thereby considerably reduced in the saccharified solution, which, advantageously, significantly improves a later anaerobic treatment. 
         [0053]    The dissolved low-molecular sugars from the mechanical separation are moved into an acidification reactor in which they are microbiologically metabolized to different carbon acids and alcohols. The implementation of this process takes place, for example, by fermentative microorganisms of the  pseudomonas, clostridium, lactobacillus  and  bacteroides  species. In an illustrative embodiment according to the present disclosure, the dwell time in such a process step, for example, at Step  601 , may be assumed to be approximately 2 days. 
         [0054]    The metabolic products from the acidification step occurring in the acidogenesis are subsequently, in a second reactor, the so-called methane reactor, also microbiologically transformed to ethanoic acid, the  syntrophomonas wolfei  microorganism, for example, participating in Step  602 , representing, methanogenesis. 
         [0055]    The obtained ethanoic acid will then be anaerobically metabolized by methane-forming agents, such as  methanobacterium bryantii , to methane and carbon dioxide. The duration of this process step or the dwell time amounts to approximately 10 days, the reactor having to handle a COD load of approximately 15-25 kg 3 . 
         [0056]    The thus obtained gas mixture, or biogas, is collected and, in an engine-based cogeneration system, at, for example, Step  603 , engine-based cogeneration system BHKW, and Step  604  energy generation converted to energy, such as to thermal and electric energy, for example, by means of a gas turbine or a gas engine. 
         [0057]    During the anaerobic fermentation of the substrates in the methane reactor, a few residual substances and a little liquid still remain which have to be removed again from the reactor. In order to make the remaining water from the fermentation usable again, it is processed in a membrane system, for example, at Step  701 . This system may be composed of one or more, for example, two or three steps. 
         [0058]    It could therefore be possible, according to the present disclosure, to use only a single membrane step, or reverse osmosis. 
         [0059]    When two membrane steps are used, for example, particles which have a diameter of &gt;1 μm can be separated first in a first step, or micro-/ultrafiltration. The thus obtained permeate will then be largely demineralized in the 2 nd  step by reverse osmosis, so that it can be used again as process water. 
         [0060]    When three membrane steps are used, for example, particles which have a diameter of &gt;1 μm can be separated first in a first step, or micro-/ultrafiltration. In view of the permeate of the first step, a low-pressure reverse osmosis step would be conceivable, according to the present disclosure, with the advantage of a rather low energy consumption, and a high-pressure reverse osmosis would be conceivable, according to the present disclosure, as a third step. 
         [0061]    Because of the enriched mineral and nutrient contents, the remaining residues at, for example, Step  702  from the purification steps may possibly be sold as fertilizer. 
         [0062]    The permeate can again be used as process water and can be returned, for example, into the process water treatment or collection system. 
         [0063]      FIGS. 2 to 5  show different illustrative embodiments, according to the present disclosure, for carrying out the process for obtaining the energy carriers, the byproduct utilization, such as feed products, modified starch, as well as an added obtaining of process water. 
         [0064]      FIG. 2  illustrates an implementation of the process in which the system part of Step  401  for the B-starch fiber sifting is removed from the process because the fibers are returned again to this product flow in the later process. This approach has the result that the recovered starch from the recovery separator, at Step  402 , has to be conducted back in front of the fiber sifting of Step  302  of the A-starch so that the A-starch can be separated again from the fibers. 
         [0065]      FIG. 3  describes an alternative use of the feed product obtained from variant B at Step  507 . Instead of using these residual constituents as feed products, the possibility exists, according to the present disclosure, of fermenting these substances, such as proteins, or residual fibers, etc., also in a separate biogas system in the “Acidogenesis” at Step  601 ′ and Acetogenesis at Step  602 ′ which steps may be parallel to Steps  601  and  602 , to obtain methane in order to increase the energy efficiency. 
         [0066]      FIG. 4  illustrates another illustrative embodiment according to the present disclosure. In order to increase the effectiveness as a result of the specificity of the enzymes, the pentosans and the bran are moved into a separate liquefaction, at, for example, Step  505 ′, where special pentanases and cellulases are used. 
         [0067]    The fine-grain starch and fine fibers from the recovery separator, the fiber sifting and the process water treatment are also moved into their own liquefaction, such as at Step  505 . 
         [0068]    The flows from the separated liquefaction Steps  505  and  505 ′ are brought together again before the mechanical separation of Step  506 . 
         [0069]    Furthermore, the process variant of  FIG. 5  should be indicated as an additional alternative. When implementing the process of this illustrative embodiment, a portion of the energy generation is not carried out for the benefit of a further product. 
         [0070]    In contrast to the preceding illustrative embodiments, the B-starch occurring in the course of the process is not used as an energy carrier in the gas fermentation but as a valuable product such as modified starch. 
         [0071]    In the following, the energy balance of the illustrative process or processes, according to the present disclosure are considered as an example. 
         [0072]    The following reaction equation is used as a starting or simplified basis for the theoretical analysis of the gas yield and the energy that can be obtained therefrom: 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 2 C 6 H 12 O 6 → 6 CH 4  + 6 CO 2   
                 Molar glucose 
               
               
                   
                   
                 mass 180 g/mol 
               
               
                   
                   
                 correspondingly 360 g/mol 
               
               
                   
                   
                 for saccharose 
               
               
                   
                 Molar methane mass 16 g/mol 
               
               
                   
                 Spec. methane enthalpy 802 KJ/mol 
               
               
                   
                   
               
             
          
         
       
     
         [0073]    Approximately 0.2667 kg methane is therefore obtained from 1 kilogram starch. This amount of methane has an energy value of 13.4 MJ. An energy quantity of 13.4 GJ can therefore be obtained per one ton of starch. 
         [0074]    A medium-sized wheat starch facility processes approximately 10 tons of flour per hour, which corresponds to a grain quantity of approximately 12.5 t/h. For obtaining energy, approximately 2,900 kg usable carbohydrates are obtained from the above. A facility of this processing capacity can therefore theoretically produce approximately 10.8 MWh of energy in one hour. 
         [0075]    The estimated energy demand of such a facility, without B-starch drying, fiber drying and evaporating system, amounts to approximately 307.5 KWh/t of flour electrically and 2.2 GJ/t of flour thermally, that is, steam. 
         [0076]    When a realistic efficiency of η=0.3 is assumed for converting methane gas to electric energy, 326 KWh of electric energy per ton of flour can be obtained from the gas obtained from the starch. 
         [0077]    Furthermore, when it is assumed that, by means of a coupling of power and heat, the lost energy during the generating of current can be converted to heat and finally steam, 2.74 GJ/t of flour as energy are still available for producing steam. With an efficiency of η=0.88, an energy quantity of 2.4 GJ is therefore obtained, which can influence the generating of steam. 
         [0078]    It is illustrated that the required energy for the operation of the facility is covered from the obtained energy of the biogas production, and the latter could therefore be operated self-sufficiently with respect to energy. 
         [0079]    For the purpose of comparison, the following values for the gas yield from biogas facilities can be found in literature: 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 From carbohydrates 
                 790 Ln biogas/kg TS with a 
               
               
                   
                   
                 methane fraction of 50% 
               
               
                   
                 Energy content biogas 
                 approximately 5 KWh/Nm 3   
               
               
                   
                   
                 (natural gas: approx. 
               
               
                   
                   
                 10 KWh/Nm 3 ) 
               
               
                   
                   
               
             
          
         
       
     
         [0080]    From 290 kg carbohydrates/t of flour, an energy quantity of approximately 1,145.5 KWh/t of flour can therefore be obtained, at facility capacity of 10 t/h corresponding to 11.45 MWh. 
         [0081]    Ln: Standard liter 
         [0082]    Nm 3 : Standard cubic meter 
         [0083]    TS: Dry substance 
         [0084]    Although the present disclosure has been described and illustrated in detail, it is to be clearly understood that this is done by way of illustration and example only and is not to be taken by way of limitation. The scope of the present disclosure is to be limited only by the terms of the appended claims.