A process for reducing sugar loss in separating a dalme from a preliming extract and for concentrating the dalme

Abstract

A process for reducing sugar loss in separating a dalme from a preliming extract and for concentrating the dalme

Description

A process for reducing sugar loss in separating a dalme from a preliming extract and for concentrating the dalme Description of the invention The invention relates to a method for producing a highly clear sugar beet preliming extract, wherein the clear sugar beet preliming extract contains a significantly lower amount of solids, and also to a method for better separation of the separated floc from the preliming extract. Sugar is usually extracted from sugar beets by first washing the sugar beets, in which a large portion of the soil and leaves still attached to the sugar beets are removed. After the washing step, the beets are cut into small pieces with cutting machines. The sugar is extracted from the small pieces using hot water that is slightly acidic by extraction in the opposite direction. Filtration of the crude sugar beet extract and the compressibility of the extracted small pieces are preferably carried out by acidifying the extracted liquid. The crude sugar beet extract, obtained during extraction, is then sent to the extract purification stage. The extract purification operation is usually carried out with the help of carbonic acid-lime extract purification in the form of a preliming stage and a main liming stage, as well as primary and secondary carbonation and sediment separation after primary and secondary carbonation. The main task of extract purification is to remove non-sucrose substances from the pure sugar beet extract, especially those with high molecular weight. The non-sucrose substances to be separated should be decomposed as much as possible, so that no additional low molecular weight substances are introduced into the crude sugar beet extract. The crude sugar beet extract is gradually alkalized by adding milk of lime in preliming. Preliming is carried out by adding certain amounts of calcium hydroxide (milk of lime). As a result of alkalization of the sugar beet juice, the organic and mineral acids present are neutralized and the anions are precipitated, forming insoluble or sparingly soluble salts with divalent calcium ions. In this way, for example, phosphate, oxalate, citrate and sulfate are separated as calcium-related calcium ions. In addition, flocs of non-sucrose organic matter dissolved in colloidal form precipitate. The precipitation of any substance, for example anions such as oxalate, phosphate, citrate, sulfate or colloids such as pectin or protein, is defined within a pH range. Within these pH ranges, precipitation condensation occurs at the same time. The addition of milk of lime before preliming also leads to the coagulation of proteins present in the pure sugar beet juice. Due to the presence of these proteins, the above-mentioned separated non-sucrose substances are also called protein-containing fractions of the pure crude sugar beet extract. The purpose of the subsequent main liming step with the addition of milk of lime is in particular the chemical destruction of invert sugar and acid amides, which occur during the concentration of the extract with the formation of acids. Milk of lime added in the main liming also plays an important role in the first and second carbonation. A strong adsorbent for a number of non-sucrose soluble materials and a filter are provided by reacting calcium carbonate. Milk of lime, which is not consumed during the main liming process, is converted into carbonation gas in the two carbonation steps by injecting carbon dioxide into the calcium carbonate. Carbonation is carried out in two stages. In the first carbonation, the non-sucrose substances that have precipitated and concentrated and some of the colors present in the sugar beet juice are adsorbed onto the calcium carbonate formed. The extract obtained in the first sludge in the first carbonation is filtered and passed through a decanter and concentrated to obtain a concentrated sludge. In the subsequent second carbonation, a second water sludge is produced, which is also filtered and concentrated. Then the calcium carbonate sludge (sludge extract concentrate) concentrated in the first and second carbonation is usually combined and pressed. In this way, carbocalc is formed. This carbocalc is a storable product and its dry matter content is more than 70%. The preliming extract of sugar beet carbocalc is the refining of the purified extract and is reprocessed to obtain white sugar. The major drawback of conventional carbonic acid-lime extract purification is that relatively little purification is performed, as a maximum of 40% of the total non-sucrose material is removed from the crude sugar beet extract. Another disadvantage is that this process requires a very large amount of milk of lime. However, the production of the milk of lime used in the purification of carbonic acid-lime extraction and the disposal of waste generated in the production of quicklime is relatively expensive. Also, carbon dioxide emissions from lime kilns and extract cleaners are very high. In addition, the carbocalc from the carbonic acid-lime extract purification process, which consists of lime and separated water impurities, can only be used as fertilizer. A process for purifying pure sugar beet extract is known from EP 682 683 A, which comprises the following steps: preliming of the raw sugar beet extract by adding milk of lime to coagulate the non-sucrose substances and the protein-containing fraction, adding at least one auxiliary flocculant, separating the floc from the preliming water using at least one first separator to obtain a clear preliming extract, main liming of the clear preliming extract after separating the floc by adding milk of lime, and carrying out a first, and if necessary a second, carbonation step. According to “Zukerindustrie 135, (5.228-294) Fasol it is specified that decanter centrifuges with different discharge angles should be used to thicken the resulting flocs and prepare them for the subsequent addition of pressed and dried pieces. The relatively high sugar loss, i.e. the relatively high proportion of sugar in the separated floc and the undesirably high proportion of solids in the resulting clear preliming extract, both of which are the result of separating the preliming extract with a high sugar content from the floc, also still needs to be improved because it is considered one of the disadvantages of this process. In addition, another disadvantage is that under certain conditions, the decanter centrifuges used according to Fasol are more stable than other centrifuges, but continuous operation was not possible due to the different frictional viscosities of the solid fractions to be separated. Therefore, the present invention is based on the technical problem of providing a process for producing a clear preliming sugar beet extract and a protein-containing fraction from the raw sugar beet extract, as well as products made by this process, which overcomes the aforementioned disadvantages, and in particular provides a process that reliably and accurately separates the floc from the said raw sugar beet extract that has been prelimed, causing less sugar to be lost during the separation, thereby obtaining a clear preliming sugar beet extract. Likewise, the method according to this invention is capable of a continuous mode of operation. The present invention solves the existing technical problem by providing the teachings set forth in the independent claims. The present invention specifically solves the technical problem by providing a process for producing a clear preliming extract of sugar beet and a protein-containing fraction, comprising the following steps. (a) Providing a crude sugar beet extract, (b) preliming the crude sugar beet extract provided in step b) to obtain a preliming extract by forming a floc of non-sucrose solids in the obtained preliming extract, c) Setting the solid ratio to 15-25% by volume in the preliming extract (based on the total volume of preliming extract provided in process step b), d) separating the preliming extract floc obtained in step c) with a solids ratio of 15-25% by volume using at least one decanter centrifuge, comprising a motorized peripheral centrifuge drum with a cylindrical section and a conical section, wherein the angle between the longitudinal axis of the centrifuge drum and the surface line of the conical section is 6 degrees to 10 degrees, and rotating an extruder screw embedded in the centrifuge drum, e) Obtaining a clear pre-liming extract of sugar beet and a protein-containing fraction. This invention also solves the existing technical problem by providing a clear preliming extract of sugar beet, produced by the process of the invention, and a protein-containing fraction, which is preferably concentrated by the process according to the invention. The invention therefore advantageously and unexpectedly provides a process in which sugar beet extract is provided in a first process step a) for example by extraction, preferably in countercurrent extraction from sugar beet, in particular sugar beet slices, and in which preliming of this sugar beet extract is carried out in a further process step b), thereby forming a preliming extract in which a floc of non-sucrose solids is formed. According to this invention, the solid content ratio of the preliming extract in process step c) should be up to 15 to 25% by volume (based on the total volume of the preliming extract used in process step b). The invention provides in a further step process d) that the floc must be separated from this resulting preliming extract with at least one centrifugal decanter from a sugar beet preliming extract obtained. The decanter centrifuge used according to the invention comprises a motorized centrifugal peripheral drum, having at least a cylindrical section and a conical section, in which the angle between the longitudinal axis of the centrifuge drum and the surface line of the conical section is 6 to 10 degrees, and an extruder screw mounted inside the centrifuge drum. A clear preliming extract of sugar beet and a floc, in the form of a protein-containing fraction, are obtained in a process subsequent to step e). The use of at least one decanter centrifuge according to the invention as provided in the method of the invention, comprising at least one motorized peripheral centrifuge drum with a cylindrical section and a conical section, wherein the angle between the longitudinal axis of the centrifuge drum and the surface line of the conical section is 6 to 10 degrees, and a rotating extruder screw mounted within the centrifuge drum for separating a protein-containing fraction from a preliming extract having solids in an amount of 15 to 25 percent by volume (based on the total volume of the preliming extract used in process step B). The proportion of solids in the clear preliming extract of sugar beet thus obtained is lower compared to a method using crude sugar beet extract of the same composition and a different discharge angle, in particular 5 degrees and / or a different fraction of solids in the preliming extract, in particular 10% by volume. The protein-containing fraction thus obtained has a higher solids content and less sugar obtained per unit time (corresponding to lower sugar loss in the clear preliming extract of sugar beet) and a higher solids content per unit time, compared to a process using the same composition of the crude extract and a different volume of discharge angle, in particular 5 degrees and / or a different solids fraction in the preliming extract, in particular 10% by volume. The process of the invention unexpectedly leads to a better extract compared to the prior art, which means that it has a lower solids content in the sugar beet extract, i.e. the clear phase obtained after floc separation with simultaneous floc separation, and at the same time has a lower solids content per unit time and solids content, and also a lower sugar content in the protein-containing fraction. In particular, the combination of the discharge angle in the method provided according to the invention, namely the angle between the longitudinal axis of the centrifuge drum and the surface line of the conical section, with the specific proportion of solids in the preliming extract, i.e. the clear phase, appears to result in a significant loss of sugar and a very low proportion of solids in the clear phase. In particular, the combination according to the invention with the discharge angle of the specific solids fractions used unexpectedly simultaneously results in the discharge of more solids with a lower sugar content, as well as in a higher solids content and solids ratio in the protein-containing fraction. In a preferred embodiment of the invention, preliming in a process step b) is carried out by adding milk of lime to the raw sugar beet extract, in particular to an alkalinity of from 0.1 to 0.3 g CaO / 100 ml raw sugar beet extract. In particular, the pH is increased from 10 to 12, in particular from 10.5 to 12, in particular from 10.5 to 11.5, in particular 11. According to the invention, in a preferred configuration at least one coagulation aid is added to the preliming extract after preliming and before separating the flocs formed in step b1), for example a polyanionic coagulant, a copolymer, a copolymer of acrylamide and sodium acrylate, in particular a molar volume of approximately 5 million to 22 million, preferably to a concentration of 1 to 8 ppm. In a particularly preferred configuration, the solids content is preferably determined to be 17 to 23% by volume, in particular 18 to 22% by volume, in particular 20% by volume, in process step c). In a particularly preferred configuration, the solid content of the preliming extract used in process step d) is adjusted in process step c) using at least one separation device, in particular a decanter, for example a dynamic or static decanter or a sedimentation device. In a particularly preferred configuration, the angle between the axial angle of the centrifuge drum and the conical surface line of the centrifuge drum of at least one decanter centrifuge in process step d) and / or f), also referred to herein as the "discharge angle", is an angle of 6 to 10 degrees, preferably 8 to 10 degrees, preferably 8 degrees. In a particularly preferred configuration, at least a portion of the clarified sugar beet preliming extract obtained in process step e) is mixed with the preliming extract from process step b). The solids are subsequently settled in step c) and the floc is then separated in process step d). In a particularly preferred configuration, at least a portion of the clarified sugar beet preliming extract obtained in step e) is mixed with the preliming extract from process step b). The solids are subsequently settled in step c) and the floc is then separated in process step d). In a particularly preferred embodiment of the invention, in process step f) the protein-containing fraction obtained in step e) is concentrated, i.e. concentrated, in particular after diluting the albumin-containing fraction obtained in process step e) to a solids fraction of the protein ratio of 15 to 25% by volume, in particular 20% by volume. Process step f) is particularly and preferably carried out using at least one further decanter centrifuge. In a preferred configuration, the decanter centrifuge comprises a motorized peripheral centrifuge drum with at least one cylindrical section and at least one conical section, wherein the angle between the longitudinal axis of the centrifuge drum and the surface line of the conical section is 6 to 10 degrees, preferably 8 to 10, preferably 8 degrees, and at least one extruding screw embedded in the rotating centrifuge drum. In a particularly preferred configuration, the decanter centrifuge operates with at least one decanter centrifuge with a maximum of 50% of the maximum permissible torque for concentrating the protein-containing fraction in process step e) with at least one other aforementioned decanter centrifuge. The process according to the invention provides a sequence of process steps a) to e), optionally method step f), in a particularly preferred configuration, the process subject to the invention comprises process steps a) to e), in particular a) to f), i.e. between method steps a) to f) no further process steps are carried out, in particular between process steps a) to f). In a particularly preferred configuration, a process of the invention is provided in which the process steps a) to e), in particular a) to f) are carried out in exactly the sequence mentioned a), b), c), d), e) or a), b), c), d), e), f). According to the invention, the process steps are carried out simultaneously, at common times or sequentially. The invention provides a protein-containing fraction, which is obtained in particular by one of the methods of the subject matter of the invention. The invention provides a clear preliming extract of sugar beet, which is prepared in particular by one of the methods of the subject matter of the invention. The invention also relates to a decanter centrifuge comprising a peripheral centrifuge drum with a cylindrical section and a conical section, wherein the angle between the longitudinal axis of the centrifuge drum and the surface line of the conical section is 6° to 10°, and a rotating extruder screw in the centrifuge drum for obtaining a clear sugar beet preliming extract and a protein-containing fraction. Within the scope of the invention, the term "crude sugar beet extract" means the extract, also the aqueous sugar-containing medium, obtained from sugar beet, for example from sugar beet slices, by an extraction or pressing process, in particular by thermal extraction methods such as countercurrent extraction, for example at 65 to 70°C in a process known as extraction by electroporation or pressing. This sugar beet extract contains, in addition to sugar, various organic and inorganic sugar beet substances, also called non-sucrose substances. In this invention, the extract is also an aqueous sugar-containing medium, namely a "clear preliming extract of sugar beet" which is obtained as a clear phase after separation of the protein-containing fraction. According to the invention, the characteristic feature of this extract is that, according to the invention, its solids content is low (in percent by weight), i.e. the solids content is less than or equal to 12% by volume. According to the invention, the solids content in the clear preliming extract of sugar beet is from 1 to 12% by volume, in particular from 1 to 10% by volume, in particular from 1 to 6% by volume, in particular from 2 to 12% by volume, in particular from 2 to 10% by volume, in particular from 2 to 10% by volume, in particular from 2 to 6% by volume, in particular from 4 to 12% by volume, in particular from 4 to 10% by volume, in particular from 4 to 6% by volume. In the context of this invention, high molecular weight substances such as proteins, polysaccharides and cell wall components, as well as low molecular weight compounds such as organic acids, amino acids and minerals are among the “non-sucrose substances” present in the crude sugar beet extract. Cell wall components are in particular pectin, lignin, cellulose and hemicellulose. These substances, such as proteins, are in particular nucleoproteins or glycoproteins, such as macromolecules dispersed in colloidal form. Amino acids are, for example, lactates, citrates, pectinic acid or oxalates. Inorganic acids are in particular sulphates or phosphates. "Preliming" means adding milk of lime to sugar beet juice or sugar beet extract at a rate of about 0.1 to 0.3 g CaO / 100 ml of crude sugar beet extract. In preliming, the crude sugar beet extract is alkalized under mild conditions, the pH value of the crude sugar beet extract being increased from about 6 to 11.5. Preliming is for the purpose of displacing non-sugar substances, such as pectin and protein, and for the precipitation of soluble calcium salts. According to the invention, "milk of lime" is in particular calcium hydroxide, which is formed during the strong exothermic reaction of quicklime (calcium oxide) and is used as a preliming and main liming agent. Adding milk of lime to the pure sugar beet extract in preliming causes the destruction or coagulation of non-sucrose substances in the form of flocs. In this invention, the non-sucrose substances of the pure sugar beet extract are separated in process step b) to form a floc, which is called the "protein-containing fraction" or "colloidal fraction". This fraction is alkaline, is biodegradable due to its organic nature and is thixotropic. It behaves as a non-Newtonian fluid, in particular the viscosity decreases under shear stress and then the first viscosity occurs again after stress. According to this invention, "flocculate" means the mass of non-sucrose substances present in the crude sugar beet extract that is formed by the flocculation process. The floc specifically consists of insoluble or sparingly soluble salts resulting from the reaction of anions of organic and inorganic acids with calcium and high molecular weight molecules of crude sugar beet extract, especially hydrophilic properties such as proteins, polysaccharides and cell wall components, which are normally dispersed in pure colloidal sugar beet extract. Anions such as oxalate, citrate phosphate, and sulfate, and pectin acid are present in the coagulation and therefore in the protein containing colloid fraction, especially pectin, protein, cellulose, and hemicellulose. The flocculation process is divided into one in which aggregation occurs by adsorption of binding polymers and another in which aggregation occurs by destruction or reduction of dissociative forces. The rate of flocculation depends on the temperature, pH value and type of lime milk addition. The precipitation of individual components of the extract, for example anions such as oxalate, phosphate, citrate and sulphate, as well as colloids such as pectin and protein, occurs within a specific pH range and the precipitation also occurs within a specific pH range. The pH value at which the maximum amount of colloids is discharged and the precipitation of insoluble lime salts is almost complete is called the optimum flocculation point of the precipitate. If settling occurs at the desired flocculation point, a uniform, stable precipitate is formed, colloidally dispersed, high molecular weight extract components occur. The settling and flocculation of pectin and proteins requires a specific temperature-dependent residence time. According to the invention, the preliming can be carried out as a cold or hot preliming. Cold preliming is preferably carried out at a preliming temperature of about 38 to 40 degrees Celsius. According to the invention, it is also preferred to add milk of lime to the pure sugar beet extract as a hot preliming at a sugar beet extract temperature of 55 to 75 degrees Celsius. The addition of milk of lime to the pure sugar beet preliming extract according to the invention is preferably carried out as a gradual preliming. Gradual preliming means a gradual increase in the alkalinity or pH value of the pure sugar beet extract, preferably by slow addition of milk of lime or by intermittent addition of milk of lime, in which the optimum pH is slowly passed. According to the invention, it is preferred that the gradual alkalization of the raw sugar beet extract can be carried out in countercurrent during preliming by means of a raw sugar beet extract that has already been alkalized, for example by means of a sludge extract concentrate from the carbonation steps. Countercurrent gradual alkylation means that the added extract with high alkalinity is mixed as quickly as possible with an extract with lower alkalinity, without a different alkalinity gradient being able to be created in the mixing zone. According to the invention, the protein containing protein fraction separated in process step d) is obtained in process step e). According to another preferred embodiment of the invention, the protein containing fraction obtained in process step e) is concentrated using a decanter centrifuge according to the invention, preferably as in process step d), in an optional process step f). According to the invention, concentration of the protein containing fraction means a preferred solids ratio of 35 to 50%, preferably 38 to 45%, preferably 45% (solids content in the protein containing fraction to the total weight of the composition in this text unless otherwise stated in the text). In the context of this invention, the preliming extract ratio is preferably expressed as a percentage based on the volume of the preliming extract, which is obtained after centrifugation, in particular at 4000 rpm and 10 minutes, and the removal of the supernatant means the "solids ratio". In the context of this invention, the "solids content" of the protein-containing fraction is the proportion, preferably in weight percent, of the protein-containing fraction obtained after removal of water, for example by drying. In the context of this invention, the "solids ratio" of the protein-containing fraction is the mass of the protein-containing fraction obtained in step e). According to this invention, it is per unit time, preferably in kilograms per hour. The solids ratio is calculated from the measured volume per unit protein-containing fraction after determining the concentration of the protein-containing fraction. Within the framework of this invention, the "solids content" in the crude preliming clear sugar beet extract is the proportion of the crude preliming clear sugar beet extract obtained after centrifugation, in particular at 4000 rpm for 10 minutes, and after removal of the supernatant. Within the scope of this invention, the "sugar content" of the protein-containing fraction means the sugar content present in the protein-containing fraction after separating the floc from the preliming extract. "Decanter", especially a static or dynamic decanter, is a device or apparatus that operates to remove separated materials from a liquid according to the principle of separation of components with the help of gravity. A decanter centrifuge comprises a motorized peripheral centrifuge drum with at least one cylindrical section and at least one conical section, and at least one rotating extruder screw embedded in the centrifuge drum, as well as an inlet, at least one central outlet, and at least one solids discharge passage. In particularly preferred configurations, the torque during the centrifugation operation in step d) and / or f) is at most 50 percent, in particular at most 40 percent, of the maximum permissible torque. In particularly preferred configurations the torque during centrifuge operation is from 10 to 50 percent, preferably from 20 to 50 percent, preferably from 30 to 50 percent, preferably from 10 to 40 percent, preferably from 20 to 40 percent, preferably 30 to 40 percent of the maximum allowable torque. In the context of this invention, the "maximum allowable torque" is the highest torque at which the torque can be operated without causing permanent damage. In the context of this invention, "permanent damage" means damage that has significant effects on the operation in question, in particular the centrifuge is no longer able to operate or its performance is reduced to such an extent that it produces a significantly lower quality pre-liming extract associated with the operation, in particular a phase with a solids content of more than 15% by volume of a protein-containing fraction with a solids content of 35% by weight. In the context of this invention, a "flocculating aid" is a substance that influences the potential of particles in colloidal reactions in such a way that they accumulate in the form of flakes and can be removed from the system, for example, after sedimentation. The flocculating aid must therefore overcome the electrostatic repulsion of the particles, most of which are negatively charged. According to this invention, the flocculating aid can also be a sedimentation accelerator. Within the scope of this invention, "flocculation aid" or "sedimentation accelerator" means compounds which have the effect of agglomerating solid particles into larger units or grains. As a result of the agglomeration of grains, the solids settle more quickly due to their larger mass. At the same time, the pores between the individual particles increase so that the water present in the settled sludge can be removed by filtration or centrifugation. The preferred polyanionic flocculants of this invention have no flocculating effect because they do not affect the dispersion of particles in the liquid phase but cause the adsorbent-binding polymers to aggregate. The copolymers of acrylamide and sodium acrylate used in a preferred embodiment of the invention as polyanionic flocculants are synthetic organic water-soluble polyelectrolytes with relatively high molecular weights of about 5 million to 22 million. These compounds are medium to strong ions. Products 2440 and 2540 (from Stockhausen) and NA 945 (from Clarflock) are particularly preferably used as flocculant aids. Other configurations that are considered an advantage result from dependent claims. The invention will be described in more detail with reference to the following exemplary configurations. Example 1 The raw extract from sugar beet is added to a heating tank containing a stirrer, a feed for the raw sugar beet extract, a discharge line, and a pH electrode and heated to 55°C. Over a period of 20 minutes, milk of lime is gradually added to the pH of the optimum flocculation point of the sediment (approximately 0.1-0.3 g CaO / 100 ml water). A polyanionic flocculant (Praestol 2540TR) is then added to increase the preliming rate. The preliming extract is drained, adjusted to a solids ratio of 20% by volume using a static decanter and fed to a decanter centrifuge having an angle between the longitudinal axis inside the centrifuge tank and the surface line of the conical section of 8° and operating at 10-30% of the maximum allowable torque. The preliming extract (feed) is fed to the decanter centrifuge at 3000 l / h. The protein-containing fraction is separated from the preliming extract and is discharged from the decanter centrifuge through the discharge port, and the clear preliming extract of sugar beet is removed from the outlet of the decanter centrifuge. The solids fraction of the protein-containing fraction is 38 to 42% by weight and the solids content is 192 kg / h of dry matter.The sugar content of the protein-containing fraction is 15 kg / h, and the solids ratio in the pre-liming sugar beet clear extract is 4 to 6% by volume. Example 2 Comparison of different discharge angles between the longitudinal axis and the surface line of the conical section of the centrifuge drum The raw sugar beet extract is prelimed again as in Example 1 and fed at 3000 l / h with a solids ratio of 20% by volume to different decanter centrifuges into the centrifuge drum with different discharge angles of 5°, 8°, 10° and 15°. The different decanter centrifuges operate with different torques in each case so that floc separation can be carried out. The protein-containing fractions separated from the different decanter centrifuges as well as the raw sugar beet extracts differ in the solids ratio in the prelimed sugar beet extract, and also in the sugar content and the solids ratio and the protein-containing fraction 1 (see Table 1). Using a 5° decanter centrifuge results in higher sugar content as well as lower solids content (DS by weight percent) and lower solids content (kg / h) in the protein-containing fraction as well as higher solids content by weight percent in the preliming clear extract of sugar beet. Using an 8-degree decanter centrifuge, a clear pre-liming extract of sugar beet is obtained, as well as a high solids ratio, a high solids content, and a lower sugar content in the protein-containing fraction. Using a 10° decanter centrifuge also yields comparable sugar and solids content, as well as a protein-containing solids ratio. Even if the torque is slightly higher than the maximum allowable torque, the 15° decanter centrifuge is unable to separate the protein-containing fraction from the preliming extract. Table 1 Outlet angle ° 5 8 1 0 1 5 Feed (preliming extract) L / h 3 000 3 000 3 000 3000 Torque used (% of maximum permitted torque) % Very low < 40 % 40 - 80 % > 100 % Solids content of preliming extract by volume .-% 20 20 20 20 Shaft phase (clear preliming extract of sugar beet) L / h 2400 2600 2650 3000 Protein containing fraction L / h 600 400 350 - Protein containing fraction, solid content kg / h 148 192 164 - Protein containing fraction (DS), solids content by weight -% 23 38 - 42 38 - 40 - Sugar content of protein containing fraction kg / h 22 15 15 - Solids ratio in sugar beet preliming clear extract Volume -% 12 - 14 4 - 6 8 - 12 - Example 3 Comparison of solids ratio in the inlet stream The preliming extract prepared according to Example 1 was adjusted to 10, 20 and 30% by volume of solids by means of a stationary decanter. These preliming extracts with different adjustments were each added to a decanter centrifuge with an 8° discharge angle. Using preliming extracts with different solids ratios led to different results: The use of a preliming extract with a solids content of 10% by volume leads to insufficient separation of the protein-containing fraction, and a preliming extract with a solids content of 30% by volume leads to an increase in the solids content during the clarification phase (see Table 2). Using a preliming extract with a 20% solids ratio results in a very clear sugar beet preliming extract and a high solids ratio in the protein-containing fraction. Table 2 Outlet angle ° 8 8 8 ° Feed (preliming extract) L / h 3000 3000 3000 L / h Torque used (% of maximum permitted torque) % < 40 % < 40 % 20 - 60 % % Solids ratio preliming extract Vol.-% 10 20 30 Vol.-% Clear execution (clear sugar beet preliming extract) L / h 2780 2600 2600 L / h Protein containing fraction L / h 220 400 400 L / h Protein containing fraction, solids content kg / h 100 192 192 kg / h Protein containing fraction (DS), solids ratio weight-% 36 - 40 38 - 42 38 - 42 Weight-% Sugar ratio protein containing fraction kg / h 9 15 15 kg / h ratio Solids in preliming sugar beet clear extract Wt.-% 2 - 3 4 - 6 16 - 20 Vol.-% Example 4 The preliming extract prepared according to Example 1 with a solids content of 15% by volume is added to a decanter centrifuge with a discharge angle of 10 degrees (operated according to Example 1). The resulting clear sugar beet preliming extract is collected and reprocessed. The protein-containing fraction is collected at 36% solids, diluted to 20% solids by volume, and added to a decanter centrifuge. The decanter centrifuge has an 8° discharge angle and operates at a maximum torque of 50% of the maximum allowable torque. The protein fractions are concentrated by centrifugation at 45% solids by weight.

Claims

Claim 1. A process for preparing a clear preliming extract of sugar beet and a protein-containing fraction from a crude sugar beet extract, comprising the following steps: (a) providing a crude sugar beet extract, (b) preliming the crude sugar beet extract provided in step b) to obtain a preliming extract by forming a floc of non-sucrose solids in the obtained preliming extract, (c) adjusting the solids ratio of 15-25% by volume in the preliming extract (based on the total volume of the preliming extract provided in process step b) using a dynamic or static decanter, (d) separating the floc of the preliming extract obtained in step c) with a solids ratio of 15-25% by volume using at least one decanter centrifuge, comprising a motorized centrifugal drum with a cylindrical section and a conical section, wherein the angle between the axes The longitudinal axis of the centrifuge drum and the surface line of the conical section are 6° to 10°, and the rotation of an extruder screw embedded in the centrifuge drum, e) obtaining a clear preliming extract of sugar beet and a protein-containing fraction.

2. The process according to claim 1, wherein in a process step f) the protein-containing fraction obtained in process step e) is concentrated using a further decanter centrifuge.

3. A process according to any one of the preceding claims, wherein at least a portion of the clear sugar beet preliming extract obtained in process step e) is mixed in another step of this process with the preliming extract from process step b), a preliming extract mixed with the sugar beet preliming extract, the solids fraction is adjusted and then added to the floc separation in process step d).

4. The process according to any one of the preceding claims, wherein the angle between the longitudinal axis of the centrifuge drum and the surface line of the conical section is 8 to 10 degrees.

5. The process according to claim 4, wherein the angle between the longitudinal axis of the centrifuge drum and the surface line of the conical section of at least one decanter centrifuge is exactly 8 degrees.

6. The process according to any one of the preceding claims, wherein the preliming extract used in process step d) has a solids content of 20% by volume.

7. The process according to any one of the preceding claims, wherein the at least one decanter centrifuge used in steps d) and / or f) operates at a torque of at most 50 percent of the maximum allowable torque.

8. The process according to any one of the preceding claims, wherein the at least one decanter centrifuge used in steps d) and / or f) operates at a torque of at most 40% of the maximum allowable torque.

9. Process according to any one of the preceding claims, wherein, after step b); a flocculation is carried out in a step b1) by adding at least one flocculating aid.