EP2313199B1 - Apparatus and method for producing flour and/or semolina - Google Patents

Description

The present invention relates to the field of production of flour and / or semolina from cereals.

From the EP 0 335 925 B1 is a method and apparatus for the production of milled grain products such as flour, semolina or haze known on the principle of high milling. The material to be ground is mill-rolled here many times, preferably twelve times to twenty times, and repeatedly sieved. The material to be ground is thereby guided at least twice over double-roller grinding stages without screening between the individual stages of the double-grinding and then each sighted at the Doppelvermahlung.

These prior art devices and methods have the disadvantage that the material to be ground in the grinding arrangements is strongly heated during the grinding process. This is particularly disadvantageous in the milling of grain to flour, since the introduced into the grain heat the proteins present in the grain are changed or damaged. In particular, gluten is changed by the introduced heat, since this is thermolabile. Since gluten has a very large influence on the bread quality of a bread to be baked with the flour, changes in the gluten through the milling process lead to changes in the bread quality, which must be compensated for example in a bakery during the production process of a bread from the flour produced.

Another disadvantage of the prior art method and apparatus for producing flour from cereals is the compelling use of multiple sequential grinders for flour production, as these are expensive and their operation is energetically complex. This use of multiple grinders It also means that large buildings are needed for the mill, which further increases the cost of constructing a mill.

In addition, the previously known method and the device have the disadvantage that they require a high energy requirement for the production of flour and / or semolina from cereals. For example, in the prior art, at least 25 to 27 kWh / t, or even more than 33 kWh / t, are needed to produce flour of common fineness, i. common particle size.

From the DE 27 08 053 discloses a process for the fine and ultrafine comminution of ores by means of a high-pressure bed mill, wherein this comminution is carried out under high compressive stress, but limited to protect against oversized compressive stresses and pressure peaks.

EP 0 433 498 A1 discloses a roll mill, wherein the ground product is characterized by means of sensors and the nip is varied on the basis of the sensor signal. Furthermore, a return of a part of the milled product is disclosed in the roll mill.

WO 01/32311 A1 discloses a roll mill for grinding cereals and recycling a portion of the meal to the roll mill.

US 1,497,108 discloses a roller mill for flour production, wherein the rollers each have different sections with different in the axial direction grinding properties.

US 6,550,700 B1 discloses a method for estimating the grindability of grain due to the study of a subset from that. Furthermore, the milling of grain in a mill with recycling of a partial amount of the ground product into the corresponding grinding stage is disclosed.

DE 44 14 367 A1 discloses a method for fresh material grinding by means of a good bed roller mill, wherein a Bunkerfüllstand is regulated, from which the good bed roller mill fresh product is supplied. In addition, a return of regrind is disclosed.

DE 14 07 046 A1 discloses a riser internal sifter with a zigzag channel for use in the grain industry.

DE 43 20 362 A1 discloses a sifter for cereals or other granular or flowable products in the form of a climbing or oblique sifter, which is fed by known conveying or feeding devices.

DE 12 11 901 B discloses a method and apparatus for grinding cereals wherein the grains are passed between revolving pairs of rollers. The grinding should be done with a gap between the rolls of each pair, which is considerably smaller than the size of the grains to be ground.

GB 739 562 A discloses a roll mill for grinding cereals for flour production. A nip is adjusted due to the increase in temperature of the material to be ground by the grinding, with a certain grinding result is associated with a certain increase in temperature by the grinding.

DE 198 19 614 A1 discloses a method and apparatus for the milling of grain crops. The temperature distribution of the grinding rolls is continuous during the grinding process supervised. The product to be ground is conveyed as product veil in the nip. If different temperature values are detected across the width of the rollers, the rollers are adjusted to one another again by a control device, for example by regulating the contact pressure or by regulating the grinding gap.

It is an object of the present invention to avoid the disadvantages of the known, in particular therefore to provide a method by which flour from cereals with less heat input can be produced during the grinding process. Another object of the present invention is to provide a method by which flour from grain can be produced inexpensively and energetically.

These objects are achieved by a method and a use according to the independent claims.

A device disclosed here but not belonging to the invention relates to a grinding arrangement for producing flour from cereals, which in particular is bread wheat, durum wheat, corn or buckwheat. The grinding arrangement is characterized by at least one grinder, which is designed in particular as a good bed roller mill. The grinder has at least one supply opening and at least one discharge opening. The grinding arrangement comprises at least one separation stage for separating ground products into finer ground product and coarser ground product and a return arrangement for returning at least a portion of the coarser ground product into the feed opening of the grinder.

Bread wheat is also known as Triticum aevestivum and durum wheat as Triticum durum.

For the purposes of the application, rice is also understood as cereals.

Roll mills usually have two rollers rotating at different speeds, between which a nip and thus a grinding force is adjustable, is transported through the example, grain and thus ground. The freeness, i. the particle size of the milled product to be achieved is determined primarily by the size of the nip. During the grinding process, the nip remains constant. A grain to be ground is fed into this roll mill. In order to grind grain with such a roll mill, the nip must be adjusted to the particle size of the grain. In such a milling, a lot of heat is introduced into the grain by the mechanical grinding process and the pressure in the nip, especially in small nip widths, so that the grain is strongly heated. Since the grain is fed to the roll mill, i. especially as individual particles, the throughput at a small nip, so in particular in the final, so-called Feinmahlstufen, very small.

For the purposes of the present application, a good-bed roller mill is understood to mean a force-controlled roller mill. For example, mechanically biased springs or hydraulically coupled gas pressure accumulators are used to generate power. A pressure is applied to the rollers in the direction of the nip, so that a nip between these rollers, depending on the amount and the type of grain to be ground in the nip and the set pressure. For example, a gap of about 0.5% to 2% of a roll diameter may occur. The resulting grinding gap thus results in the collection of the grain, which in particular depends on the friction is through the rollers. In this case, a part of the particles may be larger than the gap. Typically, however, the particles are smaller than the resulting gap. In the catchment area between the rollers, a bed of material is formed when the bed of high-grade material can move in from an oversupply of grain, for example by means of a filled material shaft or funnel. The comminution is based on a packed particle bed in the grinding gap. The setting of the grinding force is used to control the energy input at the mill. The energy input determines - depending on material and grain size - the production of finer ground product in the good bed and is set to an optimum range.

In particular, the throughput through a good bed roller mill, for example, depends on the speed of the rollers. In general, a higher speed leads to a higher throughput. For example, peripheral speeds of the rollers, i. the speed on the surface which is in engagement with the grain during the grinding process is in the range of 1 m / s to 1.5 m / s, in particular less than 1 m / s and especially less than 0.1 m / s , In general, smaller peripheral speeds are set for finer mill products.

If, for example, the intake of grain into the bed of high-grade rollers is not sufficient, so that so-called fluidization phenomena occur, then a compressor, e.g. a so-called compressor screw, are used, which promotes the grain in the nip, supporting, for example, to gravity.

The good bed roller mill is thus characterized by a variable nip during grinding, an adjustment of the pressure in the grinding gap and in that an increase in the grain volume in the nip leads to an enlargement of the grinding gap.

Advantageously, the rolls of the good bed roller mill rotate at a different speed. This leads to an increased shear of the grain in the nip and thereby to an improved grinding in bran and semolina.

By bran is meant in the sense of the application also a mixture of bran and shell parts of the grain.

Furthermore, a separation stage in the sense of the present invention is understood to mean an apparatus for separating cereals into various sizes, shapes or densities, wherein a separation can take place either on the basis of one of these parameters or due to any combination of these parameters. For example, a separation can only take place in different particle size of the ground grain. Thereupon, for example, a further separation into different densities of the particles of a size range is possible. For example, in a first step, the ground grain can be separated into particles with particle sizes of 280 μm to 560 μm and particles with particle sizes of 560 μm to 1120 μm. In a second separation step, for example, the particles from the size range from 280 .mu.m to 560 .mu.m can then be sorted according to the density and / or the shape of the particles, while the particles from the size range from 560 .mu.m to 1120 .mu.m are ground a second time.

For the purposes of the present application, a separation of a ground product into a finer ground product and a coarser ground product means a relative separation according to particle sizes of the ground product. For example, at a separation of a Milled product in particles with particle sizes of 100 .mu.m to 200 .mu.m and from 200 .mu.m to 300 .mu.m, ie in two fractions, the ground product in the first size range, the finer ground product and in the second size range, the coarser ground product. A separation is also possible in two, three, four or more fractions.

The grinder arrangement disclosed herein but not belonging to the invention has the advantage that by returning at least a portion of the coarser meal into the feed opening of the grinder by means of the return arrangement, a reduction in the number of grinders required to achieve a defined degree of grinding, i. a particle size to be achieved after the grinding process, as the ground product is passed through the grinder again until the defined degree of grinding is reached. This leads to a more cost-effective grinding arrangement over the prior art, since the number of grinders and the size of the entire grinding arrangement are reduced.

Another advantage of the grinding arrangement, particularly when using a high bed roller mill, is the selective grinding of the grain in the grinder, i. the bran is less ground than the endosperm, also called endosperm. In other words, the bran retains a larger particle size than the ground meal body, which makes it easier to separate in a separation stage.

The recirculated ground product is mixed, for example, before re-grinding in the grinder with not yet ground grain, so that a throughput of the mixture of grain and recycled ground product is kept as constant as possible in the grinder. This can be achieved for example by a control mechanism for the not yet ground grain.

Preferably, in the grinding arrangement, a specific grinding force of the grinder is adjustable so that grain is heated during the grinding process by less than 30 ° C compared to the temperature of the grain before the respective grinding. Preferably, the grain is heated to less than 15 ° C, more preferably less than 10 ° C, and most preferably less than 5 ° C.

For the purposes of the present application, the ratio between the pressure exerted on the rollers in the direction of the grain, i.e., the specific grinding force S, is. the pressing force F, roller diameter D and the effective, with the grain engaging roller length L according to the formula S = F / LD understood.

The adjustability of the specific grinding force of the grinder so that the heating of the grain is limited by the grinding process, has the advantage that the change or damage to the proteins, especially the gluten in the grain is reduced. This leads to better reproducible properties of the flour prepared according to the present invention. In special applications, for example, even a cooling of the rollers, the grain or the rollers and the grain provide.

The specific grinding power is thus advantageously adjusted so that the desired grinding result is achieved, ie a generation of a high proportion of finer milled product without overheating the grain during the grinding process too much. This also achieves a reduction in the energy consumption of the grinding plant over the prior art, since the grain is heated less.

Preferably, a nip between two rollers of the grinder of the grinding arrangement is variable at a constant specific grinding force on the einbringbare in the nip grain.

It is also possible, the specific grinding power, e.g. depending on the particle size, the number of resulting particles or the heating of the grain by hand or by means of control or regulating device adjustable or regulated to make.

The exercise of a constant specific grinding force on grain in the nip has the advantage that the grain is kept under constant conditions, i. essentially constant heat input into the grain is ground by the grinding process. This is achieved in that the nip between the two rolls of the grinder is variable, so that, for example, when increasing the amount of grain in the nip this is increased and thus the force exerted on the grain specific grinding force remains constant. In the case where the amount of grain in the nip is reduced, the nip also decreases and the specific grinding force applied to the grain remains constant.

However, it is also possible that as the nip increases, the specific grinding force increases in a defined manner. This is achieved in that, for example, when using a mechanically biased spring for generating force an enlargement of the nip leads to a further elongation of the spring and thus an increased specific grinding force is adjusted due to the spring characteristic of the spring. Because the throughput of grain is increased by the enlarged nip at the same time increasing the specific grinding power remains an energy input per grain quantity is approximately constant, so that the grinding conditions also remain constant here. When the size of the grinding gap is reduced, the specific grinding force decreases accordingly so that an energy input per quantity of cereal remains approximately constant.

Quite surprisingly, it has now been shown that despite the gentle grinding of the grain by limiting the heat input into the compacted grain in the nip, the starch cores, i. the main constituent of the endosperm, be damaged. This damage is particularly adjustable, for example by adjusting the specific grinding force or a conditioning of the grain.

Particularly preferably, the separation stage of the grinding arrangement is designed such that cereal having a density of less than 2 g / cm ³ and in particular less than 1.5 g / cm ³ in finer ground product and coarser ground product is separable. The milling products have a density of less than 2 g / cm ³ and in particular less than 1.5 g / cm ³ .

This has the advantage that the separation step is adapted to the separation of grain into finer and coarser ground product and thus a better separation according to the density of the ground product is made possible. This is possible, for example, in separation stages which achieve separation by means of air flows, in that the geometry of the separation stage and the air flow are adapted precisely to the density range of the material.

More preferably, a specific grinding force in the grinding arrangement is set to less than 3 N / mm ² . This specific grinding force is preferably less than 2 N / mm ² , more preferably between 1 N / mm ² and 2 N / mm ² and most preferably less than 1 N / mm ² .

This limitation of the specific grinding power has the advantage that the heat introduced into the grain is further reduced by the grinding process, so that damage or changes in the proteins, in particular gluten, is further reduced.

Most preferably, the separation stage of the grinding arrangement at least one device from the list of the following devices: zigzag sifter, Griessputzmaschinen, Plansichter, turbo heaters, hopper separators, Querstromsichter. Preferably, the separation stage comprises two of these devices, and more preferably at least two of these devices.

Zigzag classifiers are known from the prior art, for example from the GB 468 212 and the DE 197 132 107 C2 or from the textbook " Principles and Newer Methods of Air Classification "by H. Rumpf and K. Leschonski (CIT 39 (1967) 21, 1261ff ).

Griessputzmaschinen are known from the prior art, for example according to the DE 612 639 C1 , of the DE 34 10 573 A1 or the textbook " Maschinenkunde für Müller "by AW Rohner (1986 ) and are available, for example, from Bühler AG.

Planifters which are designed as screening devices are also known from the prior art, for example from the textbook " Maschinenkunde für Müller "by AW Rohner (1986 ) and are produced, for example, by Buhler AG.

Turbosensors are also known from the prior art, for example from the textbook " Handbook of Process Engineering " by H. Schubert (Wiley-Verlag ) and are offered for example by the company Hosokawa Alpine AG, Augsburg in the series Turboplex or Statoplex.

This construction of the separation stage comprising at least one of the devices described above has the advantage that for the respective separation according to particle size, particle shape or density, the respectively suitable device, i. Zig-zag sifter, grinder, plansifter or turbo-gasifier can be integrated into the separation stage. For example, for a two-stage separation, it is possible to separate first according to the particle size and then according to the density of the particles. For example, a plansifter is used for the first separation step and, for example, a zigzag sifter or a moth cleaning machine for the second separation step. Here, the grain is first separated into finer and coarser ground product with the Plansichter and then, for example, the finer ground product separated by means of a zigzag sifter into components of different density, ie in particular in semolina and bran. It is also possible that the plan sifter separates the grain into several fractions and these fractions, including the coarser ground product, are then each conveyed to a separate zigzag sifter in which they are separated according to the shape and / or the density.

For the purposes of the application, semolina ground wheat with a small amount of bran, i. essentially clean semolina, understood.

However, it is also possible in particular for one separation stage to comprise one plan sifter and two or at least two successively arranged zigzag sifters.

Preferably, the grinding arrangement on two grinders. In particular, the grinding arrangement has three grinders, particularly preferably four grinders and very particularly preferably at least four grinders.

This has the advantage that, for example, structurally identical grinders can be arranged sequentially one after the other and in each grinder the grinding power for the grinding result to be achieved is individually adjustable. Furthermore, it is also possible, for example, to combine grinders of different construction, that is to say a good bed roller mill and a roller mill with a constant nip.

Particularly preferably, the grinding arrangement has two separation stages. This milling arrangement preferably has three separation stages, particularly preferably four separation stages and very particularly preferably at least four separation stages.

This has the advantage that, for example, if the grinding arrangement has several grinders, each of these grinders can be followed by a separation stage. Furthermore, it may be advantageous that two separation stages are arranged sequentially and each of these separation stages carries out a separation of the ground product according to different parameters.

Further, very particularly preferred is a flow-based separation stage, in particular with air flows, as Teilumluft- or circulating air separation stage (5), in particular containing a zigzag sifter (13) formed.

This has the advantage that at least a portion of the air passing through the separation stage separates the meal product, for example, according to density, ie, separation, for example Semolina and bran, is returned to the separation stage. This leads to a reduction in the energy consumption of the separation stage, as this, inter alia, the air consumption of the separation stage is lowered.

In a further preferred embodiment, the grinding arrangement comprises at least one separating step for the separate removal of bran from the finer ground product.

This has the advantage that the bran, for example, still contained in the finer ground product is removed, which is particularly advantageous for the production of white flour.

In an alternatively preferred embodiment, the grinder has at least one roller type according to the following list: smooth rollers, corrugated rollers, profile rollers. For example, profile rolls have a defined surface roughness.

This has the advantage that the grinder can be adapted to the respective grain to be ground and the grinding result to be achieved. It is possible that the grinder has two smooth rolls, two corrugated rolls or even a combination of smooth, profile and corrugated rolls.

Preferably, at least one grinder of the grinding arrangement, a conditioning device is vorschaltbar and / or nachschaltbar. At least one of the following cereal parameters can be set with this conditioning device: temperature, moisture, particle size, percentage of bran.

This has the advantage that the grain before and / or after grinding in the grinder is conditioned so that an optimum grinding result for the particular application is achievable.

For example, the conditioning device may be formed as a shot peeper, in which the grain is ground with a roller mill with a constant nip. In this case, a ground product of bran and endosperm is produced. In the conditioning stage, for example, in a first step, a part of the bran can be separated and thus the proportion of bran in the grain can be adjusted. By adjusting the grinder in the shot stage, the particle size of the grain can also be adjusted, which is then fed into the subsequent grinder.

The conditioning device may, for example, also contain a planifilter for separating different particle sizes or also a part of the bran. In addition, the conditioning device may also include a tempering for heating or cooling of the grain before the grinding process and a device for adjusting the moisture of the grain.

The grinding plant preferably has at least one sensor for measuring the ash content, the moisture, the temperature and / or the particle size of the ground grain, in particular the finer ground product and / or the coarser ground product. However, it is also possible to measure the temperature and / or the humidity of the air flowing out of the separation stage, for example from the zigzag classifier, with this sensor. This at least one sensor is preferably contained in the separation stage.

This has, inter alia, the advantage that the ash content or else the moisture content of the separated ground product, ie of the finer ground product and / or of the coarser ground product, can be measured, for example, after separation in the separation stage. Thereupon, the ground product may be in a conditioning device, for example are conditioned to an optimum moisture content for grinding.

Another advantage is the measurement of the temperature and / or the humidity of the effluent from the separation stage air. As a result of this measurement, it is now possible, for example, to regulate the separation stage, in particular the zigzag sifter, to optimum conditions, i. optimal flow conditions for optimal separation, in the separation stage.

In particular, this is a near-infrared spectrometer, i. NIR spectrometer, and / or a color sensor. The color sensor is particularly suitable for measuring the ash content of the meal product. The NIR spectrometer is particularly suitable for measuring the moisture content of the ground product and / or the air.

A first aspect of the invention is directed to a process for producing flour from cereals, preferably bread wheat, durum wheat, corn or buckwheat. This process is carried out in particular with a grinding arrangement as described above. In one process step, a comminution of the grain is carried out in a grinder, which is a good bed roller mill. This good bed roller mill has at least one feed opening, rollers, a catchment area, a grinding gap between the rollers and at least one discharge opening. In this case, the grain is drawn from a filled material shaft or funnel through the rollers, so that in the catchment area, a good bed is formed, and the grinding gap is greater than a typical grain particles. The milling of the cereals is carried out in particular with such a specific grinding force that during the grinding process, the cereals are less than 30 ° C higher than the temperature of the cereals before each grinding is heated. Preferably, the cereal is ground with such a specific grinding force so that the grain during the milling process by less than 15 ° C, more preferably by less than 10 ° C and most preferably by less than 5 ° C compared to the temperature of the cereal before heated the respective grinding. The cereal is in particular preferably ground with a specific grinding force of less than 3 N / mm ² , preferably less than 2 N / mm ² , more preferably between 1 N / mm ² and 2 N / mm ² and very particularly preferably less than 1 N / mm ² , In a further method step, the ground grain is conveyed by means of a conveyor arrangement in a separation stage. In a further step, the separation of the ground grain in the separation stage into finer ground product and coarser ground product. In particular, cereals having a density of less than 2 g / cm ³ , in particular less than 1.5 g / cm ³ , are separated into finer ground product and coarser ground product, wherein the ground products have a density of less than 2 g / cm ³ , in particular less than 1.5 g / cm ³ . In a next step, at least a part of the coarser meal product is returned to the feed opening of the good bed roller mill by means of the return arrangement. Furthermore, finer ground product is removed from the separation stage.

This method is preferably carried out with the device described above and thus has all the advantages of the device described above.

On the one hand, it is preferred to set starch damage to the grain by selecting the specific grinding force when grinding in the grinder. On the other hand, the heat input into the grain is limited by this setting of the specific grinding force.

Under starch damage to the grain is understood in the sense of the application damage to the starch core in the endosperm, so that this example, easier to absorb water or is more accessible to enzymes.

This adjustability of starch damage to the grain by selecting the specific grinding power has the advantage that the starch damage of the grain is adaptable to the respective market needs. For example, a strong starch damage is needed in breadmaking in England because high water absorption of the flour is required in breadmaking in England. In Asia, however, a small starch damage is required, so that the flour absorbs little water, since many products are sold in Asia in a dried state and thus after the manufacturing process of the product by starch damage increasingly absorbed water must be removed, which is energetically complex and thus is expensive.

Particularly preferably, the grain is ground by means of two passes through the grinder at least 90% in finer ground product. In particular, the grain is ground by means of three passes, particularly preferably by means of four passes and very particularly preferably by means of at least four passes through the grinder at least 90% in finer ground product.

This has the advantage that if the fraction of finer milled product with fewer passes is achieved, the throughput through the muller is increased, but a higher specific mulling force is required. This leads to a stronger heating of the grain during the grinding and to a greater starch damage to the grain. If the grinding plant is set so that several passes through the grinder are necessary to achieve 90% finer ground product, then reduced the throughput through the same grinding plant, but the specific grinding power is lower for the same grain to be processed. As a result, less starch damage to the grain is achieved as well as less heating of the grain during the grinding process.

Very particular preference is given to essentially separating bran from the vegetable ground product in the separation stage in one process step.

Particularly preferably, the separation stage is followed by a further grinder for further grinding of the finer meal product.

This has the advantage that after the separation of a finer grinding product, this can be ground in a separate grinder for the production of, for example, special flours.

Further particularly preferred is the first separation stage downstream of a further separation stage for further separation of the finer meal product.

This has the advantage that each separation stage can be adjusted to the specific separation result. For example, the separation stages may have different separating powers with regard to the density of the particles to be separated.

More preferably, at least one grinder downstream of a dissolver for the dissolution of the grain after grinding in the grinder. This has the advantage that with a possible compression of the grain in the grinder, the ground product is dissolved by the resolver into individual particles and thus a separation into finer and coarser ground product in the separation stage is made possible.

As a dissolver, so-called impact dissolvers are preferably used in practice. But there are also known to the expert drum, agitators or so-called attrition mills or friction mills.

Most preferably, at least one of the following parameters of the grain is adjusted in a conditioning device before and / or after grinding: temperature, moisture, particle size, proportion of bran.

In particular, the conditioning device is designed as a scraping stage.

An additional aspect disclosed herein, but not part of the invention, is directed to a zigzag classifier which is particularly suitable for carrying out the method as described above. The zigzag sifter is designed in such a way that cereal having a density of less than 2 g / cm ³ and in particular less than 1.5 g / cm ^{3 can be separated} into finer ground product and coarser ground product. The milling products have a density of less than 2 g / cm ³ and in particular less than 1.5 g / cm ³ .

This zigzag sifter is preferably used in the grinding arrangement described above and thus has all the advantages of the zigzag sifter described above.

An additional alternative aspect of the invention disclosed herein, but not part of the invention, is directed to a machine bed roll mill which is particularly suitable for carrying out the method as described above.

This good bed roller mill is preferably used in the grinding arrangement described above and thus has all the advantages of this grinding arrangement described above.

Preferably, grain in the high-bed roller mill is grindable into finer ground product and coarser ground product. A specific grinding force is less than 3 N / mm ² , preferably less than 2 N / mm ² , more preferably between 1 N / mm ² and 2 N / mm ² and most preferably less than 1 N / mm ² .

Another aspect of the present invention is directed to the use of a good bed roller mill for the production of flours and / or semolina from grain by comminution, in particular bread wheat, durum wheat, corn or buckwheat. The good bed roller mill includes at least one supply port, rollers, a collection zone, a refining gap between the rollers and at least one delivery port. The grain is drawn from a filled shaft or funnel through the rollers, so that in the catchment area, a good bed is formed. The grinding gap is larger than a typical grain particle.

The good bed roller mill is characterized by a variable nip during grinding, an adjustment of the pressure in the grinding gap and in that an increase in the grain volume in the nip leads to an increase in the grinding gap.

Another alternative aspect of the invention disclosed herein, but not part of the invention, is directed to the use of a zigzag sifter for separating cereals, preferably bread wheat, durum wheat, corn or buckwheat. The separation of grain takes place after a grinding process in a grinder into finer ground product and coarser ground product.

Preferably, cereals having a density of less than 2 g / cm ³ , in particular less than 1.5 g / cm ³ , are separated into finer ground product and coarser ground product. The milling products have a density of less than 2 g / cm ³ , in particular less than 1.5 g / cm ³ .

The zigzag sifter is particularly preferably used for separating bran from a finer ground product and / or coarser ground product.

Figur 1:

Schematische Darstellung einer Vorrichtung mit Gutbettwalzenmühle und einer Trennvorrichtung;

Figur 2:

Schematische Darstellung einer alternativen MahlAnordnung mit einer Walzenmühle und einer Trennvorrichtung;

Figur 3:

Schematische Darstellung einer weiteren alternativen Vorrichtung mit einer Gutbettwalzenmühle und einer alternativen Trennvorrichtung;

Figur 4:

Flussdiagramm eines erfindungsgemässen Verfahrens;

Figur 5:

Schematische Darstellung einer zusätzlichen alternativen Vorrichtung mit einer Gutbettwalzenmühle und einem Auflöser;

Figur 6:

Flussdiagramm eines alternativen erfindungsgemässen Verfahrens;

Figur 7:

Schematische Darstellung eines Mühlendiagramms mit Gutbettwalzenmühle, Auflöser, Plansichter, Zickzacksichter sowie Zyklonabscheider;

Figur 8:

Schematische Darstellung einer anderen alternativen Vorrichtung mit einer Walzenmühle mit konstantem Spalt und Computersteuerung der Getreidezufuhr;

Figur 9:

Schematische Darstellung einer Gutbettwalzenmühle mit Getreide im Walzenspalt.

Figur 10:

Schematische Darstellung eines Zickzacksichters.

Figur 11:

Schematische Darstellung eines Prallauflösers.

Figur 12:

Schematische Darstellung eines Plansichters.

The invention will be explained in more detail below with reference to embodiments for better understanding.

FIG. 1:

Schematic representation of a device with a good bed roller mill and a separator;

FIG. 2:

Schematic representation of an alternative MahlAordnung with a roll mill and a separator;

FIG. 3:

Schematic representation of another alternative device with a Gutbettwalzenmühle and an alternative separation device;

FIG. 4:

Flowchart of a method according to the invention;

FIG. 5:

Schematic representation of an additional alternative device with a good bed roller mill and a dissolver;

FIG. 6:

Flowchart of an alternative method according to the invention;

FIG. 7:

Schematic representation of a mill diagram with a good bed roller mill, disintegrator, plan sifter, zigzag classifier and cyclone separator;

FIG. 8:

Schematic representation of another alternative device with a roll mill with a constant gap and computer control of grain supply;

FIG. 9:

Schematic representation of a good bed roller mill with grain in the nip.

FIG. 10:

Schematic representation of a zigzag sifter.

FIG. 11:

Schematic representation of an impact dissolver.

FIG. 12:

Schematic representation of a plan sifter.

FIG. 1 shows a schematic representation of a grinding arrangement. 1

The grinding arrangement has as a grinder on a good bed roller mill 16, as for example in FIG. 9 is shown. The good bed roller mill 16 has a feed opening 3 and a discharge opening 4 for the cereal 20. Furthermore, the grinding arrangement 1, a separation device 5, the zigzag separator 13, for example according to FIG. 10 and a plansifter 15, for example according to FIG. 12 having. Ground cereal 20, which contains coarser ground product 21, finer ground product 22 and bran 23, is transported by means of a conveyor arrangement 9 from the high-grade bed mill 16 into the separation stage 5. The rolls of the good bed roller mill 16, not shown here, here have a diameter of 250 mm. The conveyor assembly 9 is included formed as a downpipe, so that the ground grain 20 is conveyed by gravity into the separation stage 5. The separation stage 5 has an inlet opening 6 for receiving the coarser meal product 21, the finer meal product 22 and the bran 23. Furthermore, the separation stage 5 has three outlet openings 7, through which in each case the coarser ground product 21, the finer ground product 22 and the bran 23 are separately dischargeable. The coarser ground product 21 is returned to the grinder 2 by means of the return arrangement 8. As a return arrangement, a chain conveyor is used here. Alternatively, however, the use of a bucket elevator as a return arrangement is possible.

Cereal 20 is transported through the feed opening 3 into the good bed roller mill 16, the cereal 20 being ground in the good bed roller mill 16 into coarser ground product 21, finer ground product 22 and bran 23. For this purpose, a maximum specific grinding force of 1 N / mm ^{2 is set} in the good bed roller mill 16, which typically forms a nip of between 1.25 mm and 5 mm, depending on the amount of grain 20 fed. The ground product is transported via the discharge opening 4 and the conveyor assembly 9 and through the inlet opening 6 in the separation stage 5. In the separation stage 5, the ground product is sorted by size into coarser ground product 21 and a mixture of finer ground product 22 and bran 23 in a first step. For this purpose, the plansifter 15 is used. The coarser ground product 21 is transported through one of the outlet openings 7 in the return assembly 8 and returned to the grinder 2 for re-grinding. The mixture of finer ground product 22 and bran 23 located in the separation stage 5 is separated into bran 23 and finer ground product 22 by means of a zigzag sifter. The finer ground product 22 is discharged via the lateral outlet opening 7 and the bran 23 via the upper outlet opening. 7

The good bed roller mills here have rolls with a roll diameter of 250 mm with a length of 44 mm. On the rollers, a force of 22 kN is exercised. The grinding is carried out with a specific grinding force of 2 N / mm ² with a nip of a gap thickness of 2 mm. A flour yield in ground product here is 12.5%, with about 5.3% bran being separated with a zigzag sifter. The specific energy consumption at the mill is only 1.6 kWh / t, corresponding to approximately 12.8 kWh / t are needed for the production of finished flour.

The grain fed to the circuit here has an ash content of 0.52%, the ash content of the flour produced being 0.47%.

FIG. 2 shows an alternative schematic representation of a grinding arrangement 1. The same reference characters in FIGS. 1 and 2 denote the same components here.

The grinding arrangement 1 according to the figure has, in contrast to the grinding arrangement on a grinder 2 with two rollers 10, which are spaced at a fixed distance s. The fixed distance s is adjustable and is adapted to the grain size and can be, for example, 1 mm.

Unlike the in FIG. 1 described process takes place here no return of the coarser meal product 21 in the feed opening 3 of the grinder 2. For example, the coarser ground product 21 can be conveyed into another, not shown here grinder.

FIG. 3 shows a further alternative schematic representation of a grinding plant 1. The same reference characters in FIG. 2 and FIG. 3 denote like components.

In contrast to the grinding plant 1 according to FIG. 2 has the grinding plant 1 according FIG. 3 a separating device 5, which comprises a zigzag separator 13 and a grime cleaning machine 14. In the separation stage 5, the mixture of coarser ground product 21, finer ground product 22 and bran 23 by means of the zigzag sifter 13 into coarser ground product 21 and a mixture of finer ground product 22 and bran 23 is separated. In a second step, the finer ground product 22 is separated from the bran 23 in the grime cleaning machine 14.

The process for grinding cereal 20 and separating the ground product from coarser ground product 21, finer ground product 22 and bran 23 is otherwise substantially as in FIG. 1 described.

FIG. 4 shows a flowchart of a method according to the invention. Cereal 20 is transported to a conditioning device 11 which contains a shot stage and there pre-ground into a mixture of bran 23 and semolina (21; 22). In addition, the grain is tempered in the conditioning device 11 to a temperature of 20 ° C. After this conditioning, the conditioned cereal 20 is fed to a high bed mill 16 and further ground, where it is mixed prior to grinding with coarser mill product 21 which is recycled. The temperature during grinding increases by less than 5 ° C. In other words, the temperature of the conditioned cereal 20, which has a temperature of about 20 ° C before the grinding, even after mixing with the recirculated coarser grind product 21, does not exceed 25 ° C during the grinding process heated in the high-bed roller mill 16. After grinding in the high-bed roller mill 16, the ground product is conveyed to a separating device 5 which comprises a planifter 15 and a zigzag classifier 13. In this separation stage 5, therefore, the ground product is separated into coarser ground product 21, finer ground product 22 and bran 23 and discharged separately from the separator 5.

It is also possible that the grain is cooled between the grinding stages or even a cooling of the rollers takes place itself. The combination of both cooling options is also possible.

FIG. 5 shows an additional alternative schematic representation of a grinding arrangement 1. grain 20 is conveyed in a bed of good-rolling machine 16 and ground in this. The grinding process compacts the meal so that it is conveyed into a dissolver 12 before separation into planifier 15 into individual particle sizes. The dissolver 12 is here as impact dissolver as in FIG. 11 shown formed. In this dissolver 12, the compacted ground product is substantially dissolved in the individual particles and then in a Plansichter 15 according to FIG. 12 promoted. This plansifter 15 separates the ground product into coarser ground product 21 and finer ground product 22. The coarser ground product 21 is conveyed by means of the return arrangement 8 to the high-pressure bed mill. Finer ground product 22 is removed from the grinding arrangement 1. As a return arrangement here a bucket elevator is used. Alternatively, however, the use of a chain conveyor as a return arrangement is possible.

FIG. 6 shows a flow chart of an alternative method according to the invention for the production of flour in a Gutbettwalzenmühle 16 according to FIG. 9 promoted and ground there. Subsequently, the ground grain 20 is in a Plansichter 15 according to FIG. 12 promoted and separated there into coarser ground product 21 and a mixture of finer ground product 22 and bran 23. The coarser ground product 21 is returned to the high pressure bed mill 16 for re-grinding. The mixture of finer ground product 22 and bran 23 is ground again in a further bed of fine-bed rollers 16. The ground product is then conveyed to a grinder 14 from Bühler AG (article number: MQRF-30/200) and there separated into coarser ground product 21, bran 23 and flour 24. The coarser ground product 21, which was separated as a finer ground product 22 after the first grinding stage, is thereby conveyed back to the good bed roller mill 16 for re-grinding.

FIG. 7 shows a schematic representation of an inventive mill diagram. Cereal 20 is in a Gutbettwalzemühle 16 according to FIG. 9 conveyed to the grinding and after grinding into a dissolver 12, which is designed here as impact dissolver according to Figure 11, promoted. Subsequently, the ground product is conveyed to another bed of fine-bed rollers 16 and ground there again. Then, the ground product in a Plansichter 15 according to FIG. 12 promoted, which separates the ground product into four fractions, each having particles in a defined size range. Each of these four fractions is placed in a separate zigzag sifter 13 FIG. 10 transported, in which the bran is removed from the ground product. The remainder of the ground product is then ground in a further good bed roller mill 16, fed to a further dissolver 12 and then separated into a further plan sifter 15 in at least two, three, four or even five fractions. These can be ground again in high-bed roller mills 16 or else be conveyed in a zigzag classifier 13 for separation of Bran. In addition, the mill diagram includes cyclone separator 18 for further separating bran from an air stream of a zigzag sifter 18.

FIG. 8 shows an additional schematic representation of a grinding plant 1. The same reference characters in FIG. 1 and FIG. 8 denote the same components here.

This grinding plant essentially corresponds to the grinding plant according to FIG. 1 and additionally has a sensor 31 for measuring the force exerted by the grain 20 in the nip W with the gap thickness s on the rollers 10 and a compressor 19. The sensor 31 is connected to a control device 30 for transmitting the measured forces to this control device 30. The control device 30 is further connected to the drive of the rollers 10 for adjusting the rotational speed of the rollers. In order to avoid overheating of the grain 20 by the grinding process, the force exerted on the rolls 10 by the amount of grain 20 in the nip W is measured. Increases now the measured force on the rollers 10 by, for example, a higher supply of grain 20 from the compressor 19, so more heat is introduced by the grinding process in the grinder 2 in the grain 20, resulting in changes or damage to the proteins, in particular Gluten, in the grain can lead 20. By means of the measured force by the sensor 31, the rotational speed of the rollers can now be reduced by the control device 30 such that the measured force on the rollers 10 again reaches a desired value. Thus, it can be ensured that not too much heat is introduced into the grain 20 by the grinding process and also the grinder 2 is not damaged.

The further process for the production of flour corresponds to that in FIG. 1 already described methods.

FIG. 9 shows a schematic representation of a good bed roller mill 16 with two rollers 10. In the high-bed roller mill 16 grain 20 is retracted by the opposite rotation r of the two rollers 10, so that a Gutbetttsituation in the nip W is formed. On the rollers 10 with a diameter D of 250 mm and a length of 1000 mm, a force F of 300 kN is exerted, so that a specific grinding force of 1.2 N / mm ^{2 is} achieved. The ground grain 20 contains coarser ground product 21, finer ground product 22 and bran 23 ground. This milled product is compacted by grinding in the high-bed roller mill 16, so that this before separation in a separation stage, not shown here in a resolver such as FIG. 11 to dissolve into individual particles.

FIG. 10 FIG. 12 shows a zigzag sifter 13 having an inlet 41 for a mixture of finer milled product 22 and bran 23 to be separated. An air stream 40 is directed along the axis of the zigzag sifter and adjusted so that the bran 23 has a lower density than the finer milled product 22 is blown through the bran outlet 42. The heavier ground product 22 falls in the zigzag classifier 13 so that it is conveyed through the semen outlet from the zigzag classifier 13. The so-called upward flow rate of the air flow 40 is here in the range of 0.7 m / s to 2.5 m / s depending on the material to be separated.

FIG. 11 Figure 3 shows an impingement dissolver 15 having an impingement dissipator inlet 51, rotors 51, and an impingement dissipator outlet 52. Compacted crop 53 is conveyed into the impingement dissolver 15 where it meets the rotors 51 containing the compacted crop by dissolving, inter alia, by the impact so that cereal 54 substantially dissolved into individual particles is formed. This resolution can take place in several stages by successively connected rotors 51, for example two to six, wherein here two rotors 51 are shown, which are mounted on a shaft 55. The rotors 51 have a shape such that the grain is conveyed to the impact dissolver outlet 52.

FIG. 12 shows a plan sifter 15 with a coarse sieve 61, a middle sieve 62 and a fine sieve 63. Ground cereal 20 containing coarser ground product, finer ground product 22 and bran 23 is conveyed into the Plansichter 15, so that the ground grain in several Fractions of different sizes can be separated. The coarse screen 61 has a mesh size of the screen of 1120 μm, the middle screen 62 has a mesh size of the screen of 560 μm, and the fine screen 63 has a mesh size of the screen of 280 μm. The ground grain 20 is thus separated into three fractions, the first fraction having a size range of 1160 microns to 560 microns, the second fraction has a size range of less than 560 microns to 280 microns and the third fraction a size range of less than 280 microns. The first fraction and the second fraction are classified here as a coarser ground product 21 and contain bran 23. These two fractions are then according to FIG. 1 promoted, for example, in a good bed roller mill. The third fraction containing finer milled product 22 and bran 23 is determined according to FIG. 1 For example, in a zigzag sifter according FIG. 10 encouraged to separate the bran.

Claims (14)

1. Method for producing flour from grain (20), characterized by the following steps:

   - material bed comminution of the grain (20) in a grinder designed as a material bed roller mill (16) having

   - at least one feed opening (3);

   - rollers (10);

   - a draw-in region;

   - a grinding gap (W) between the rollers (10); and

   - at least one delivery opening (4);

   wherein the grain (20) is drawn in by the rollers (10) from a filled material shaft or funnel such that a material bed is produced in the draw-in region, and wherein the grinding gap (W) is larger than a typical grain particle;

   - conveying the ground grain (20) into a separating stage (5) by means of a conveying arrangement (9);

   - separating the ground grain (20) in the separating stage (5) into finer ground product (22) and coarser ground product (21);

   - returning at least some of the coarser ground product (21) into the feed opening (3) of the material bed roller mill (16) by means of a return arrangement (8);

   - discharging the finer ground product (22) from the separating stage (5).
2. Method according to Claim 1, characterized in that starch damage of the grain (20) is set by selecting the specific grinding force during the grinding in the material bed roller mill (16).
3. Method according to Claim 1 or 2, characterized in that the grain (20) is ground at least up to 90 % into finer ground product (22) by means of at least four passes through the material bed roller mill (16).
4. Method according to Claims 1 to 3, characterized in that bran (23) is substantially separated from the grain (20) in the separating stage (5).
5. Method according to one of Claims 1 to 4, characterized in that a further grinder (2) is connected downstream of the separating stage (5) for the further grinding of the finer ground product (22).
6. Method according to one of Claims 1 to 5, characterized in that a further separating stage (5) is connected downstream of the first separating stage (5) for the further separation of the finer ground product (22).
7. Method according to one of Claims 1 to 6, characterized in that a detacher (12) is connected downstream of at least one grinder (2;16) for detaching the grain (20) after the grinding in the grinder (2; 16) .
8. Method according to one of Claims 1 to 7, characterized in that at least one of the following parameters of the grain (20) is set in a conditioner (11) before and/or after the grinding: temperature, moisture, particle size, proportion of bran (23).
9. Method according to one of Claims 1 to 8, characterized in that the grinding in the material bed roller mill (16) takes place with such a specific grinding force that the grain (20) is heated during the grinding operation by less than 30 °C relative to the temperature of the grain (20) before the respective grinding.
10. Method according to one of Claims 1 to 9, characterized in that the grinding in the material bed roller mill (16) takes place with a specific grinding force of less than 3 N/mm².
11. Use according to one of Claims 1 to 10, characterized in that in the separating stage (5) grain (20) having a density of less than 2 g/cm³ is separated into finer ground product (22) and coarser ground product (21), and the ground products (21; 22) have a density of less than 2 g/cm³.
12. Use of a material bed roller mill (16) for producing flour and/or semolina from grain (20) by material bed comminution, wherein the material bed roller mill (16) contains:

    - at least one feed opening (3);

    - rollers (10);

    - a draw-in region;

    - a grinding gap (W) between the rollers (10); and

    - at least one delivery opening (4);

    wherein the grain (20) is drawn in by the rollers (10) from a filled material shaft or funnel such that a material bed is produced in the draw-in region, and wherein the grinding gap (W) is larger than a typical grain particle.
13. Use according to Claim 12, characterized in that the grain consists of bread wheat, durum wheat, maize and/or buckwheat.
14. Use according to Claim 12 or 13, characterized in that a specific grinding force of the material bed roller mill (16) is set in such a way that grain is heated during the grinding operation by less than 30 °C relative to the temperature of the grain (20) before the respective grinding.

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