WO2008009733A2

WO2008009733A2 - Improved method for producing ethanol, gluten and bran from cereals

Info

Publication number: WO2008009733A2
Application number: PCT/EP2007/057490
Authority: WO
Inventors: Günther TUSEL; André HAMERS; Ingo De Buhr
Original assignee: Prokon Nord Energiesysteme Gmbh; Acs Agrochemische Systeme Gmbh
Priority date: 2006-07-19
Filing date: 2007-07-19
Publication date: 2008-01-24
Also published as: EP2066698A2; DE102006033791A1; WO2008009733A3

Abstract

The invention relates to a method for producing ethanol, gluten, bran, yeast and carbon dioxide from cereals. The invention especially relates to improved methods for producing ethanol, gluten, bran, yeast and carbon dioxide from cereals.

Description

Improved processes for the production of ethanol, gluten and bran from cereals

The invention relates to a process for the production of ethanol, gluten, bran, yeast and carbon dioxide from cereals. In particular, the invention relates to improved processes for the production of ethanol, gluten, bran, yeast and carbon dioxide from cereals.

The fermentation (fermentation) for the representation of alcohols from the raw material grain is one of the oldest biotechnological procedures and is u.a. used for the production of alcoholic beverages, such as beer and wine. Industrially used alcohol can be represented by the fermentation of grain. Corresponding alcohols, in particular ethanol, are used as starting material for the production of pharmaceutical products and formulations, cosmetic products and for the synthesis of a range of chemicals.

Ethanol has long been known as an energy carrier, but was not economically viable in the past due to the higher process costs compared to the extraction of fossil fuels. Due to the shortage of fossil oil reserves and the reduction in CO ₂ demanded by the Kyoto agreement, the potential use of bioethanol as an energy carrier has new significance obtained. Economic as well as ecological interests demand an improvement of the existing processes for the production of ethanol as well as an efficient use of the existing biomass on a large scale.

State of the art are numerous processes for the production of alcohols from biomass. Since completely different starting materials (glucose, starch or cellulose) are used for these processes, i.a. Sugarcane, sugar beet, cereals, etc., the methods for obtaining the bioalcohol differ greatly from each other. Even when using identical starting materials, there are different technological and biological process concepts.

In conventional processes for the production of ethanol from cereals by fermentation is usually:

(a) first mow the grain,

(b) suspending the ground grain in water and adding microorganisms, in particular yeasts,

(c) the fermenter broth thus obtained is fermented, and then

(d) ethanol is concentrated by thermal separation from the fermenter broth.

The separation of the ethanol is usually carried out by distillation. The remainder is stillage, which is usually concentrated and used as a fertilizer or after drying as a proteinaceous feed.

Examples of corresponding fermentation processes and of individual process steps are AT 398981, DE 2944483 C2, DE 3007138 C2 and US Pat. No. 6569653 B1 The produced in the usual method vat is very high in protein, which is generally processed and used for feed, vinasse can only be used as a limited fertilizer. The production of the feed, in particular the drying of the stillage, however, involves a high expenditure of energy, which comprises about 50% of the energy required by the entire production process of a standard plant for bioethanol.

CO ₂ is a climate-damaging gas whose release should be avoided, economic use would make sense. The Greenhouse Gas Emissions Trading Act of 8 June 2004 makes the avoidance and reduction of CO ₂ economically sensible.

The resulting in a fermentation CO ₂ is generally released to the environment after the gases have been cleaned and separated from environmentally problematic impurities. The use of enriched with CO ₂ air zb by horticultural operations, has been possible only conditionally.

The overall method of the prior art requires very large amounts of water, in particular for the mashing per tonne of grain used up to 3.5 m ^{3 of} fresh water needed, this water must be worked up in part cost and energy intensive.

In all conventional methods according to the prior art, the problem arises that the energy consumption is very high, that the costs for enzymes and auxiliaries are very high, that short cleaning intervals are required for the plant, that the fermenter broth is fermented, and Obtaining the ethanol a long residence time is required, which means that the system is a total of equipment very expensive, since very large amounts of liquids and solids must be moved. System sizes for daily capacity of over 100m ³ / ethanol can therefore only be realized with considerable effort. It was therefore the object of the invention to remedy the disadvantages described above or to reduce them. In particular, it was the object of the invention to reduce the energy and water requirements of an ethanol Production without significantly affecting the ethanol yield or the duration of the process.

According to the invention, it has now been found that the process for the production of ethanol can be carried out in an energy-time and cost-saving manner as a whole, if a starch purified in a certain way is used as the fermentation product. Accordingly, according to the invention, there is provided a process for preparing purified starch comprising the steps of:

i) milling starchy grain in a fluidized air mill into a cornstarch such that 90% of the particles of the flour have a particle size of 150-250 μm, preferably 180-220 μm and particularly preferably 190-

Having 210 μm, ii) separating bran from the flour, and then iii) separating proteins from the flour.

Here, the grinding of the grain in an air vortex mill is of particular importance. Surprisingly, it has been found that for the energy-saving implementation of a fermentation process the gentle

Milling cereals is particularly conducive. If the fine structure of the

Starch particles of ground grain of those of unmilled

Cereals comes close, a particularly good fermentation and separation of the ethanol from the fermenter broth or mash can be achieved. best

Results for a gentle grinding were achieved with an air vortex mill.

As cereals in the context of this invention, in particular wheat, maize or triticale be used. The use of wheat is particularly preferred. The bran is preferably separated with a sieve. To separate de proteins, the ground starch is preferably mashed with water and the proteins separated by sieving and optionally dried. The separated proteins are preferably processed into gluten. According to the invention, an actual process for the production of ethanol is further specified which uses the starch which can be prepared by the above-described purification process. The method comprises the steps:

iv) providing purified starch, v) fermenting the starch provided by step iv) to a fermenter broth, optionally after liquefying the starch, vi) preparing a mash by separating microorganisms from the

Fermenter broth, vii) separating ethanol from the mash.

Surprising advantages could be achieved by the method according to the invention: particle sizes of 200 .mu.m can be achieved by using air vortex mills which preserve the natural fine structure of the starch, of the protein and of the bran. Maintaining the natural structure of starch, bran, and proteins allows the bran and proteins to be separated from the starch before any enzymatic or thermal treatment of the substrate is required. This results in particular advantages in the fermentation; Here, significantly shorter fermentation times were achieved, conventional processes require fermentation times of 60 hours for a fermentation cycle, a fermentation time of less than 40 hours was achieved by the method according to the invention, thereby the expenditure on equipment could be considerably reduced. The use of enzymes has been reduced, the costs for water treatment have been reduced, fresh water is not needed, waste water has no significant burden and can be given to consumers. According to the invention, it has furthermore surprisingly been achieved that segregation of all by-products prior to the thermal treatment no longer produces any sludge, as a result of which substantial advantages are achieved in the distillation. The aqueous residue of distillation and rectification contains as its main component organic compounds which can be used thermally or otherwise. Advantages result in a distillation to separate the ethanol substantially by energy and time savings and a considerable savings in the processing of by-products (bran, proteins, yeast).

The process according to the invention, in particular when the actual process of ethanol production is combined with the process for producing purified starch, thus advantageously permits the production of ethanol, gluten, bran, yeast and carbon dioxide from cereals.

The by-products protein, bran and the yeast obtained from the solid phase of the vinasse can be used as feed and of higher quality, as feed the processes known from the prior art are produced, since the by-products have been exposed to a low thermal stress due to the invention.

Preferably, the grain is first subjected to swelling by adding liquid, preferably water, before swaging. The grain is then ground in a swollen state, since the bran can be separated well in this state, the bran is separated by sieves.

Air vortex mills cause the material to be ground into extreme turbulence and, as a result of the impact of particles on particles, as well as by impact with the tool, the material to be ground is comminuted by impulse transmission. The ground material is picked up and accelerated by air turbulence, the rotation of the air is induced by the high radial acceleration and the high path speed of the rotating tool. A high volume of air efficiently removes the crushed grain and allows a low thermal load on the grain.

The milling of the grain with air vortex mills allows the separation of the proteins before the liquefaction, saccharification under enzymes is initiated, the proteins are separated by decantation and dried, whereby a starch milk and gluten are obtained. The carbohydrates contained in the starch milk are enzymatically liquefied in a conventional manner, saccharified and then fermented.

Equivalent amounts of ethanol to the starch employed are formed during fermentation by the yeasts generally added to start the fermentation. The fermentation may be carried out by any of the methods known in the art. The fermentation comes to a halt when all fermentable carbohydrates are fermented. After completion of the fermentation, the microorganisms and in particular the yeast are separated and worked up to forage yeast.

The CO ₂ produced in the fermentation comes from renewable raw materials and has only slight contamination with other gases compared to conventionally generated CO ₂ . It can be collected from the fermenter exhaust air, separated in a conventional manner and condensed.

By the fermentation and the subsequent separation of the yeast a mash is obtained. The present in the mash alcohol is preferably distilled and rectified, while the known methods for distillation and rectification can be used. The dehydration of the separated ethanol is preferably carried out by membrane sieves. As a result of the separation according to the invention of the bran and of the proteins, fewer secondary alcohol constituents are produced in the fermentation for ethanol. This leads to a high-quality raw alcohol and thus reduces the distillation and rectification effort. The efficiency of energy used to produce recovered ethanol is improved by the process of using a nearly completely freed solid mash.

According to the process of the invention, the water obtained by the distillation, rectification and dehydrogenation can be recirculated and recycled to the process. The invention accordingly relates in particular to a process for the production of ethanol from cereals, comprising the steps:

a) sourcing the cereals,

b) grinding the swollen cereal in an air fluidizing mill so that 90% of the particles of the ground material reach a particle size of 200 μm,

c) separating the bran from the material to be ground with a sieve,

d) separating proteins by a decanter and drying the proteins,

e) fermenting the starch depleted of bran and proteins with a microorganism, preferably a yeast, and

f) separating the microorganism,

g) wherein the CO ₂ produced by the fermentation is collected and optionally purified and liquefied,

h) separating ethanol from the ethanol / water solution obtained in step f), preferably by distillation and

i) optionally, absoluting the obtained ethanol by a pervaporation method.

In fermentation processes, in particular for producing ethanol in a process according to the invention as described above, the preparation of suitable sugar solutions as fermentable starting materials is a recurring problem. A disadvantage of conventional sugar solutions is considered in particular that a high proportion of non-recyclable waste in the fermentation and a high proportion of stillage is obtained in a subsequent distillation. Another task was therefore, sugar solutions as To provide starting materials for fermentations and preferably subsequent distillations and corresponding fermentation and distillation processes, with which the disadvantages of the prior art can be avoided or reduced.

Therefore, according to the invention, there is also provided a method for producing a first sugar solution, comprising the steps:

aa) producing or providing a starch milk,

ab) thermally liquefying the starch of the starch milk,

ac) columns of starch for obtaining mono-, di- and / or oligosaccharides,

ad) separating fats, oils and proteins from the starch milk obtained in step ac), and

ae) obtaining the first sugar solution as permeate of a first membrane filtration of the starch milk obtained in step ac) and / or ad).

The first sugar solution is largely free of hard-to-ferment ingredients and is therefore particularly suitable for avoiding or reducing the onset of a distillation stillage. The first sugar solution is sterile if the method is suitable. In addition, the production of the first sugar solution does not result in waste that is difficult to dispose of; instead, the separated fats, oils and proteins can be used as feed.

Preference is given to a method in which the first sugar solution contains not more than 0.01% by weight of starch, the first sugar solution being particularly preferably starch-free.

Particularly preferably, the first sugar solution comprises a proportion of 15-25% by weight of glucose, particularly preferably of 18-22% by weight of glucose. Such Sugar solutions can be fermented particularly easily and residue-free for ethanol production.

To further reduce the proportion of starch milk ingredients not converted to sugar solution and to increase the sugar yield, it is preferable to add a first retentate substream to the first membrane filtration of the starch milk to be split in step ac) to perform step ac). 25-30% by volume, preferably 27% by volume, of the starch milk used in the membrane filtration are preferably recycled as the retentate substream for carrying out step ac).

Also according to the invention, a method is provided for producing a second sugar solution, comprising the steps:

ba) preparing or providing a pentosan fraction of a starch milk,

bb) optionally concentrating the pentosan fraction,

bc) columns of cellulose and / or hemicellulose of the pentosan fraction, preferably with addition of acid and particularly preferably with addition of acid in a flash evaporator,

bd) separating fats, oils and proteins from the pentosan fraction obtained in bd), and

be) recovering the second sugar solution as permeate a third membrane filtration of the obtained in step bc) and / or bd) Pentosanfraktion.

The second sugar solution is also largely free from constituents which are difficult to ferment, and is thus particularly suitable for avoiding or reducing the onset of a distillation stillage. This is particularly advantageous because the pentosan fraction used to prepare the second sugar solution contains a high proportion of substances which are difficult or impossible to ferment, especially cellulose and / or hemicellulose. The second sugar solution is sterile if the method is suitable. In addition, the production of the second sugar solution does not result in waste which is difficult to dispose of; instead, the separated fats, oils and proteins can be used as feed.

Preference is given to a process in which the second sugar solution contains a proportion of not more than 0.01% by weight of starch, the first sugar solution being particularly preferably starch-free.

Particularly preferably, the second sugar solution comprises a proportion of 15-25% by weight of glucose, particularly preferably of 18-22% by weight of glucose. Such sugar solutions can be fermented particularly easily and residue-free for ethanol production.

In a particularly preferred process, a retentate substream is added to the first membrane filtration of the pentosan fraction to be cleaved in step bc) to carry out step bc). As a result of this process configuration, the yield of sugar solution measured in relation to the total amount of starch milk and pentosan fraction used can advantageously be increased. Preferably 1 to 5% by volume, preferably 3% by volume, of the starch milk used in the first membrane filtration is recycled as the retentate substream for carrying out step bc).

Particularly preferred are those methods for preparing a first or second sugar solution in which the starch milk in step ac) and / or the pentosan fraction in step bc) saccharification enzymes are added. The saccharification enzymes advantageously assist in cleaving the starch, cellulosic and / or hemicellulosic components into more easily fermentable sugars.

For producing the starch milk in step aa) the main stream and / or for producing a pentosan fraction in step ba) the secondary stream is particularly preferably a starch milk purified in a three-phase decanter used. Such mainstream and off-stream fractions of a starchy milk are easily prepared by conventional three-phase decanters. The term "main stream" designates a starch milk with the following composition (average data, in% by weight): 31% starch, 0.8% proteins, 0.3% fats, 0.1% pentosans, 0.2% Salts and minerals, 0.2% cellulose, balance water. The term "side stream" designates a pentosan fraction having the following composition: (average data, in% by weight): 5% starch, 2% proteins, 0.3% fats, 1% pentosans, 0.3% salts and minerals , 2% cellulose, balance water.

It is further preferred if a purified starch is taken up in an aqueous solvent as described above and then purified in a three-phase decanter as described above to obtain purified starch milk and / or a pentosan fraction. The purified starch of the present invention described above is particularly advantageously purified from constituents which are difficult to ferment, thus assisting the avoidance of stillage in a distillation and the avoidance of waste in the production of the easily fermentable sugar solution.

Particularly preferably, a second retentate substream of the first membrane filtration is added to the pentosan fraction to be cleaved in step bc) to carry out step bc). In this case, preferably 100 t of the total pentosan fraction 30 used in the membrane filtration is recycled to carry out step bc).

With the sugar solutions prepared or prepared according to the invention, a particularly advantageous fermentation process can be carried out. The fermentation process, preferably for the production of ethanol, comprises the steps:

ca) providing a first or second sugar solution as described above;

cb) carrying out the fermentation to produce a fermenter broth, cc) separating microorganisms from the fermenter broth to produce a mash,

cd) purifying the mash obtained in step cc) by membrane filtration to a permeate.

The permeate thus obtained is completely or substantially free of vaporizing constituents and therefore particularly suitable for carrying out a distillation, in particular for ethanol production.

A portion of the microorganisms separated in step cc) of the sugar solution provided in step ca) is preferably fed to perform step cb), and another part of the microorganisms separated in step cc) is preferably dried to a microorganism dry product. In this way, the amount of non-fermented substances can be further reduced.

It is particularly preferred to ferment a first sugar solution as described in a mainstream fermentation process, to ferment a second sugar solution as described in a sidestream fermentation process, and to combine the permeates obtained in each case in step cd). In this way, both fermentations can be optimally controlled to achieve a high fermentation product yield (in particular ethanol yield).

A preferred distillation method according to the invention comprises the steps:

da) carrying out a distillation to produce a distillate product vapor,

db) compressing a first distillation product vapor substream in a vapor compressor, operating a heat exchanger with the compressed one Partial flow for recovering heat to operate the distillation and recover a condensate as reflux for the distillation, and / or

de) purifying a second distillation product vapor substream in a permeation or pervaporation step to recover a purified distillation product and a depleted distillation product vapor substream wherein the depleted distillate vapor partial stream is compressed in a vapor compressor and stored in a heat exchanger for recovering heat to drive the distillation and Recovery of a condensate is used as reflux for the distillation.

With the distillation method according to the invention, in which in particular a permeate of a fermentation process according to the invention can be distilled, advantageously a lot of heat is recovered, so that only a minimum heating of the distillation apparatus used is needed. Furthermore, the operating conditions of the permeation or pervaporation step can be optimally adapted to the product to be recovered by distillation.

In an ethanol distillation using a distillation process according to the invention, the distillation product vapor has an ethanol content of preferably at least 80 wt .-%, more preferably at least 85 wt .-% and particularly preferably 85-90 wt .-%.

The invention will be described in more detail below with reference to the exemplary embodiments, without the examples restricting the scope of protection of the claims:

As shown in Figure 1, the grain, which is preferably stored in a silo, is introduced into the process. The grain is ground in an air vortex mill and the bran removed by deposition. Proteins are decanted and separated. By doing so, a starch milk is obtained which contains all the useful carbohydrates of the grain. The non-alcohol-forming components are thus separated before the fermentation process. This starch milk is liquefied with enzymes and saccharified.

This starch milk serves as a substrate for a fermentation, to start the fermentation yeast and nutrients are added.

The fermentation produces an alcoholic mash, from which, after completion of the fermentation, the resulting yeast is separated and separated. As a result, a feed is obtained which can be used very well for feeding animals, in particular cows, pigs, horses, chickens, etc.

The CO ₂ produced in the fermentation is washed and purified from other gases, it is separated and condensed in a conventional manner.

The thus obtained ethanol / water solution is used in a distillation apparatus for the production of raw alcohol according to a conventional prior art method. The distillation produces crude alcohol, which is purified by rectification to bioethanol or neutral alcohol. The complete drainage is done by a membrane sieve method. The purity of the product thus obtained may be up to 99.6 vol.%.

FIG. 2 shows a further, more detailed flow chart of a processing method according to the invention for obtaining ethanol.

Through a three-phase decanter, the starch milk is broken down into three fractions, one of which forms the proteins that can be worked up and purified in a known manner; the starch still contained in this fraction is separated by washing and processed further in the main stream. Second, a pentosan fraction is separated, which in addition to starch contains almost all residues, pentoses, cellulose and hemicelluloses and is further processed as a secondary stream. The third fraction forms a purified starch milk, which is further processed as the main stream. Before fermentation, the solids are separated from both the main and the secondary stream, so that only the so-called lutter water is obtained in the distillation, which is mostly used for pasting the flour and diluting it again in the process.

Processing of the main stream

The starch milk separated by the three-phase decanter is heated to liquefy and dissolve the starch in a series of heat exchangers in several stages, their viscosity initially rising sharply with temperature, passing through a maximum and decreasing again. The starch milk is kept in Zwischenbehältem over a period of 0.5 to 3 h, preferably 1 to 1, 5 h at a temperature between 80 to 90 ° C, preferably 85 ° C until the viscosity is sufficiently lowered. In a second stage, it is then brought to a temperature of 85 to 115 ° C, preferably 102 to 105 ° C, and held at this temperature over a period of 0.5 to 3 hours, preferably 40 to 80 minutes, wherein sterilized and all microorganisms are killed. The heating of the last stage of the heat exchanger is carried out with steam, the heat exchanger located in front of the process are heated for heat recovery with the already liquefied hot starch milk, which is cooled. Appropriate liquefaction enzymes may be added both prior to entry into the stage of the first heat exchangers and in the intermediate stages and before the final stage. After liquefaction, the starch solution cooled to 30 to 40 ° C, preferably about 35 ° C, is optionally diluted to lower the content of dry matter and appropriate saccharification enzymes are added thereto. The solution is stored in containers with stirring for a period of 1 to 20 hours, preferably 2 to 10 hours, until the saccharification process is completed. The duration of the saccharification process depends on the type and concentration of enzymes used. In a centrifuge, the fats and oils and the remaining proteins still contained in the saccharified starch solution are separated and discharged from the process. In a subsequent first membrane filtration, the saccharification enzymes and the not completely degraded starch fragments and oligosaccharides are retained, the purified and sterile sugar solution obtained as permeate has a glucose solids content of preferably 18-22 wt .-% and, optionally after an intermediate storage to Mainstream fermentation led.

The retentate of the membrane filtration is divided into two partial streams. A first substream is recycled to the inlet of the saccharification in order to increase the concentration of the enzymes in this process step and to carry out the saccharification in optimal time with a minimal addition of fresh enzymes. In addition to enzymes and fragments of the starting starch, the membrane filtration retentate additionally contains pentosans and hemicelluloses, which are not or only partially broken down by the saccharification enzymes used. In order to avoid a concentration of these substances by the return to the saccharification, a second partial stream of the retentate of the first membrane stage, optionally after an intermediate storage, fed into the secondary stream.

The fermentation of the sterile sugar solution of the main stream is carried out in closed stirred tanks of known type. They are provided with a cooling jacket to dissipate the heat generated during fermentation and with connections for cleaning and sterilization, for supplying the substrate, nutrient solution, compressed air, fresh and recycled yeast milk and the removal of the fermented mash and the resulting carbon dioxide. The latter is washed in a column with water before it is released into the atmosphere or sent to further use.

Several fermenters can be operated both in series and in parallel. By a suitable operation and selection of the yeast can be carried out at a temperature between 28 and 35 ° C, preferably at 32 ° C, with a high concentration of yeast, preferably by the use of flocculating yeasts and their return. This not only the Be shortened fermentation, it is also the formation of primary and secondary by-products suppressed and achieved a higher yield and purity of the final product.

After completion of the fermentation, a mash is obtained with an alcohol content of 6 to 14%, preferably 8-12% and a DS content of yeast between 5 and 8%. The mash is centrifuged, the clear water with a yeast content of less than 0.5% is further purified in a second membrane stage, stored only in water, alcohol and some dissolved minerals permeate stored in intermediate tanks and fed to the distillation column. The retentate of this membrane stage is fed to the inlet of the centrifuge. A partial flow of the thick phase from the centrifuge, the yeast milk, with a DS content of 18 to 20% is used to separate the alcohol after preheating in a vacuum evaporator at a temperature of 44 to 48 ° C to a residual alcohol content of less than 2%. evaporated, a second partial stream is fed back directly into the fermentation. The vapor from the evaporation is compressed and heats the vacuum evaporator, the condensate is combined with the clear water. A portion of the concentrated thick phase is diluted with water and, optionally after addition of nutrients, returned as yeast milk in the mainstream fermentation, the other portion is further evaporated separately and dried and forms as dry yeast another by-product.

Processing of the secondary flow

To use the fermentable substances contained in it, the separated by the three-phase decanter, very dilute pentosan fraction, optionally after intermediate storage, preheated and concentrated in a flash evaporator at a temperature of 70 to 85 ° C, preferably 74 to 80 ⁰ C. The resulting steam is compressed by a vapor compressor and serves to heat the evaporator, the cooled condensate is used as process water. The second partial stream of the retentate from the first membrane filtration after the saccharification of the main stream is combined with the pre-concentrated by evaporation side stream and heated in several stages to a temperature of 1 10 to 160 ⁰ C, preferably 125 to 150 ⁰ C and for 10 to 60 min , preferably 20 to 40 minutes, at this temperature and a pressure of 3 to 6 bar, preferably 4 to 5 bar held. Then it is suddenly relaxed to a pressure of 150 to 250 mbar in a flash tank. The resulting steam is compressed via a vapor compressor and also serves to heat the upstream evaporator.

Due to the high temperature and the sudden relaxation, the cellulose and hemicellulose contained in the by-pass fraction are split and the starch fragments not split by the enzymes into monosaccharides are further degraded. By adding acid during heating, this process can be accelerated.

In the lower part of the flash tank an already partially saccharified sterile solution of the secondary stream is obtained with a TS content of 30 to 35%. For complete saccharification, enzymes are added and the solution stirred in containers for a period of 1 to 20 hours, preferably 2 to 10 hours. It is then centrifuged to remove fats and proteins. In the third membrane filtration which optionally follows intermediate storage, the permeate obtained is a sterile sugar solution which, in addition to glucose, contains further hexoses and pentoses and is passed to the secondary flow fermentation. The retentate from the membrane filtration of the sidestream contains the separated saccharification enzymes, it is centrifuged to remove non-fermentable solids and returned to the saccharification tanks.

The fermentation of the sterile sugar solution of the secondary stream is carried out in closed stirred tanks per se known type, corresponding to those of

Fermentation of the main stream. They are equipped with a cooling jacket to dissipate the heat generated during fermentation and with connections for cleaning and sterilization, to supply the substrate, nutrient solution, compressed air, fresh and recycled yeast milk as well as to dissipate the fermented mash and the resulting carbon dioxide. The latter is washed in a column with water before it is released into the atmosphere or sent to further use.

Several fermenters can be operated both in series and in parallel. By a suitable operation and selection of the yeast can be carried out at a temperature between 28 and 35 ° C, preferably at 32 ° C, with a high concentration of yeast, preferably by the use of flocculating yeasts and their return. As a result, not only can the fermentation time be shortened, but also the formation of primary and secondary by-products is suppressed and a higher yield and purity of the end product is achieved. In the selection of yeasts are preferable to those who can also ferment pentoses to alcohol.

The mash is centrifuged, the clear water with a yeast content of less than 0.5% is further purified in a fourth membrane stage, stored only in water, alcohol and some dissolved minerals permeate stored in intermediate tanks and with the corresponding purified mash of the main stream to Guided distillation column. The retentate of this fourth membrane stage is fed to the inlet of the centrifuge. A partial flow of the thick phase from the centrifuge, the yeast milk, with a DS content of 18 to 20% is used to separate the alcohol after preheating in a vacuum evaporator at a temperature of 44 to 48 ° C to a residual alcohol content of less than 2%. evaporated, a second partial stream is fed back directly into the sidestream fermentation. The vapor from the evaporation is compressed and heats the vacuum evaporator, the condensate is combined with the clear water. A portion of the evaporated thick phase is diluted with water and recycled as yeast milk in the sidestream fermentation, the other portion is further separately evaporated with the appropriate proportion of the main stream and dried and forms as dry yeast another by-product. Distillation:

In the distillation or rectification of the product at the top of the distillation column in vapor form, the vapor is generally then condensed, a part is given as reflux to the top of the column, the other part is the desired product. The heat content of the overhead vapor is usually lost, its temperature is lower than that at the bottom of the columns, so it can not be used directly for heating the columns. It is known to the person skilled in the art that in special cases the overhead vapor can be compressed in a compressor, its compression and its temperature increase to such a level that it can now serve to heat the bottom of the column.

If the vapor at the top of the columns has an approximately azeotropic composition, it is often passed directly into a vapor permeation unit. In order for the steam to have the optimum temperature for the steam permeation plant, the column is often operated at a higher pressure than atmospheric pressure. Mostly saturated steam is present, with certain membranes the steam can also be overheated. Also, the product vapor of the Dampfpermeationsanlage generally has not sufficient temperature to heat the bottom of the columns.

It has now surprisingly been found that the product vapor of the vapor permeation system can be compressed by a vapor compressor and thus its temperature can be brought to such a level that the bottom of the column can be heated with the product vapor. This makes it possible to operate a combination of a distillation or rectification column with a downstream vapor permeation with a minimum of heating energy and to use the heat otherwise obtained in the product vapor.

The process described below for dewatering or absoluting ethanol may also be used for the separation of water from other water azeotropic forming components. These can be the be higher alcohols such as 2-propanol, butanol or the pentanols, but also be ketones such as butanone, esters such as ethyl esters or ethers. It is also clear to the person skilled in the art that even ternary or higher azeotropes can be dehydrated in the same way advantageously with the method. Furthermore, it is clear that when using suitable membranes and purely organic mixture can be separated, for example, the separation of methanol from mixtures with its esters or acetone may be mentioned, or the separation of aromatics, we benzene from its mixtures with aliphatic hydrocarbons.

The distillation column is operated in such a way that a vaporous ethanol / water mixture of approximately azeotropic composition is obtained at the top. It depends on the requirements of the purity of dehydrated ethanois how much impurities must be removed. For example, if the produced alcohol is to be used as a fuel, it is often sufficient to distill only to an ethanoic content of about 85% by weight and to remove the remaining water through the membrane unit, otherwise it must be distilled closer to the azeotrope. The resulting steam is divided into two partial streams. A partial stream is compressed in a vapor compressor and condensed in a heat exchanger which heats the bottom of the column. The hot condensate is added at the top of the column as reflux for the rectification. The second partial stream from the top of the column is passed into a vapor permeation unit and the water is removed to the specified residual content. The operating conditions of the Dampfpermeationsanlage with respect to pressure and temperature are given by the corresponding operating conditions, and can be chosen over this in a wide range. The dewatered vaporous product is compressed in a second vapor compressor and heated via another heat exchanger, the bottom of the column. The heat content of the hot condensate is used to preheat the feed to the column. In this way, the majority of the thermal energy required for the operation of the column is recovered from the overhead vapor of the column and used. An essential advantage of the method is that both partial streams are compressed separately and their pressures and temperatures can be controlled separately. Although it is possible to compress the entire vapor at the top of the column in a vapor compressor and thus reach the temperature required for the heating of the column, and only then divided into a partial flow for the return and a second for the Dampfpermeationsanlage. But then the Dampfpermeationsanlage must be operated at the required for the heating of the column bottom temperature, which greatly limits the freedom to choose the operating conditions. Furthermore, the steam undergoes a certain pressure loss when flowing through the Dampfpermeationsanlage whereby its temperature will differ from that of the partial flow for the return. Therefore, such an interconnection of a column, a vapor permeation and a vapor compression is less preferred.

According to the invention, the overall method has an energy requirement which is composed of:

1 Energy consumption distillation / rectification / dehydrogenation:

Steam requirement: 1590 kg / t ethanol x 2.10 MJ / kg = 3339 MJ / t ethanol

Electricity requirement: 490 kWh / t ethanol x 3.6 MJ / kg = 1764 MJ / t ethanol

Total energy consumption = 5103 MJ / t ethanol.

2 Energy consumption of by-product production:

Steam requirement: 1410 kg / t ethanol x 2.10 MJ / kg = 2961 MJ / t ethanol;

Electricity requirement: 300 kWh / t ethanol x 3.6 MJ / kg = 1080 MJ / t ethanol.

Total energy consumption = 3041 MJ / t ethanol. 3 As energy consumption of the overall process, (3.1 and 3.2) thus yields:

Steam demand of 3000 kg / t ethanol x 2.02 MJ / kg = 6300 MJ / kg

Electricity consumption of 790 kWh / t ethanol x 3.6 MJ / kg = 2844 MJ / kg.

The production of all products thus requires an energy consumption of 9144 MJ / t ethanol.

The energy balance of conventional methods, on the other hand, gives:

Steam required for distillation / rectification, absolution, drying of the grain slurry,

7000 kg / t ethanol x 2, 10 MJ / kg = 14700 MJ / t ethanol,

- Electricity required for distillation / rectification, absolute,

Drying the cereal slices,

330 kWh / t ethanol x 3.6 MJ / kg = 1188 MJ / t ethanol,

This corresponds to a total energy consumption of 15888 MJ / t ethanol.

It can be seen that the present invention uses 6744 MJ / t ethanol less energy than the prior art

Method. This corresponds to a 43% reduction in energy consumption.

The invention for the preparation of ethanol from grain requires only about

57% of the energy needed to carry out conventional procedures

Production of ethanol from grain are needed. This demonstrates the advantages of the invention of the process for the production of bioethanol, gluten, yeast and

Bran.

Claims

claims

A process for preparing purified starch, comprising the steps of: i) milling starchy grain in a fluidized fluid mill into a cornstarch such that 90% of the particles of the flour have a particle size of 150 to 250 μm, ii) separating bran from the flour , and then iii) separating proteins from the flour.

The method of claim 1, further comprising processing the separated proteins into gluten.

3. Purified starch, preparable by a method according to one of the preceding claims.

4. A process for producing ethanol, comprising the steps of: iv) providing purified starch according to claim 3, v) fermenting the starch provided by step iv) to a fermenter broth, optionally after

Liquefying the starch, vi) preparing a mash by separating microorganisms from the

Fermenter broth, vii) separating ethanol from the mash.

5. The method according to claim 4, characterized in that the ethanol is separated by distillation from the fermenter broth.

6. The method according to any one of claims 4 to 5, characterized in that the separated ethanol is dehydrated by a Pervaporationverfahren.

A process according to any one of claims 4 to 6, further comprising capturing CO ₂ released during the fermentation.

8. A method of making a first sugar solution, comprising the steps of:

aa) producing or providing a starch milk,

ab) thermally liquefying the starch of the starch milk,

ac) columns of starch for obtaining mono-, di- and / or oligosaccharides,

9. The method according to claim 8, characterized in that the first sugar solution is starch free.

10. The method according to claim 8 or 9, characterized in that the first sugar solution contains a proportion of 15 - 25 wt .-% glucose.

11. The method according to any one of claims 8 to 10, characterized in that a first retentate substream of the first membrane filtration in step ac) to be split starch milk for performing step ac) is added.

12. A method for producing a second sugar solution, comprising the steps of:

ba) preparing or providing a pentosan fraction of a starch milk,

bb) optionally concentrating the pentosan fraction, bc) columns of cellulose and / or hemicellulose of the pentosan fraction, preferably with added acid,

13. The method according to claim 12, characterized in that the second sugar solution is starch free.

14. The method according to any one of claims 12 to 13, characterized in that the second sugar solution contains a proportion of 15-25 wt .-% glucose.

15. The method according to any one of claims 12 to 14, characterized in that a retentate substream of the first membrane filtration in step bc) to be cleaved pentosan fraction for performing step bc) is added.

16. The method according to any one of claims 8 to 15, characterized in that the starch milk in step ac) and / or the pentosan fraction in step bc)

Verzuckerungsenzyme be added.

17. The method according to any one of claims 8 to 16, characterized in that for producing the starch milk in step aa) the main stream and / or for producing a pentosan fraction in step ba) the side stream of a purified in a three-phase decanter starch milk is used.

18. The method according to claim 17, characterized in that a purified starch is taken up according to claim 3 in an aqueous solvent and then purified in a three-phase decanter for obtaining a main stream and / or a secondary stream.

19. The method according to any one of claims 17 to 18, characterized in that a second retentate substream of the first membrane filtration in step bc) to be cleaved pentosan fraction for carrying out step bc) is added.

20. Sugar solution, preparable or prepared according to one of claims 8 to 19.

21. A fermentation process, preferably for the production of ethanol, comprising the steps:

ca) providing a first or second sugar solution according to claim 20,

cb) carrying out the fermentation to produce a fermenter broth,

cc) separating microorganisms from the fermenter broth to produce a mash,

22. Fermentation process according to claim 21, characterized in that a part of the microorganisms separated in step cc) is supplied to the sugar solution provided in step ca) for carrying out step cb), and another part of the microorganisms separated in step cc) to form a microorganism Dried dry product.

23. fermentation process according to any one of claims 21 to 22, characterized in that in a mainstream fermentation process, a first sugar solution is fermented according to claim 20, in a sidestream fermentation process, a second sugar solution is fermented according to claim 20, and in step cd) obtained Permeate be united.

24. Distillation process comprising the steps:

da) carrying out a distillation to produce a distillate product vapor,

db) compressing a first distillation product vapor substream in a vapor compressor, operating a heat exchanger with the compressed one

Partial flow for recovering heat to operate the distillation and recover a condensate as reflux for the distillation, and / or

25. Distillation method according to claim 24, characterized in that the distillation product vapor has an ethanol content of at least 80 wt .-%.