Method for reducing the sugar loss in the removal of a coagulate from pre-liming juice and for thickening the coagulate, use of a decanter centrifuge, fraction containing protein, and sugar beet pre-liming juice

Abstract

The present invention relates to the provision of a method for producing a clear sugar beet pre-limitation juice and a coagulate removed from the pre-liming juice, and to a pre-liming juice and protein-containing fraction that are provided by means of said method. A decanter centrifuge having an angle between the longitudinal axis of the bowl and the generatrix of the conical portion of 6 to 10° is used.

Claims

1. A method for producing a clear sugar beet pre-liming juice and a protein-containing fraction from sugar beet raw juice, comprising the following method steps: a) providing the sugar beet raw juice; b) pre-liming the sugar beet raw juice provided in method step a) to obtain a pre-liming juice, forming a coagulate of non-sucrose solids forming in the obtained pre-liming juice; c) setting a solids content of 15-25% by volume (based on the total volume of the pre-liming juice provided in method step b), in the pre-liming juice; d) separating the coagulate from the pre-liming juice obtained in method step c) using at least one decanter centrifuge, comprising a motor-driven, rotating centrifugal bowl including a cylindrical portion and a conical portion, wherein the angle between the longitudinal axis of the centrifugal bowl and the generatrix of the conical portion is 6° to 10°, and an extruder screw mounted rotatably in the centrifugal bowl; and e) obtaining the clear sugar beet pre-liming juice and the removed coagulate in the form of a protein-containing fraction.

2. The method according to claim 1, wherein the solids content of the pre-liming juice is set in method step c) by means of at least one separating device.

3. The method according to claim 1, wherein, in a method step f), the protein-containing fraction obtained in method step e) is thickened using at least one further decanter centrifuge.

4. The method according to claim 1, wherein at least a portion of the clear sugar beet pre-liming juice obtained in method step e) is mixed in a further method step with pre-liming juice from method step b), a pre-liming juice mixed with clear sugar beet pre-liming juice is obtained, the solids content is set in method step c) and subsequently fed to a coagulate removal process in method step d).

5. The method according to claim 1, wherein the angle between the longitudinal axis of the centrifugal bowl and the generatrix of the conical portion is 8° to 10°.

6. The method according to claim 5, wherein the angle between the longitudinal axis of the centrifugal bowl and the generatrix of the conical portion of the at least one decanter centrifuge is exactly 8°.

7. The method according to claim 1, wherein the pre-liming juice used in method step d) has a solids content of 20% by volume.

8. The method according to claim 1, wherein the at least one decanter centrifuge used in method step d) and/or f) is operated at a torque of no more than 50% of the maximum permissible torque.

9. The method according to claim 3, wherein the at least one further decanter centrifuge used in method step f) is operated at a torque of no more than 50% of the maximum permissible torque.

10. The method according to claim 1, wherein the at least one decanter centrifuge used in method step d) is operated at a torque of no more than 40% of the maximum permissible torque.

11. The method according to claim 3, wherein the at least one further decanter centrifuge used in method step f) is operated at a torque of no more than 40% of the maximum permissible torque.

12. The method according to claim 1, wherein, following method step b), a flocculation is carried out in a method step b1), adding at least one flocculation aid.

Description

EXAMPLE 1

(1) Raw juice from sugar beets is added and heated to 55° C. in a heatable container, which comprises a stirrer, an inlet for sugar beet raw juice and an outlet, and a pH electrode. Over a period of 20 min, milk of lime is gradually added to the raw juice, up to the pH of the optimum flocculation point of the pre-liming step (approx. 0.1 to 0.3 g CaO/100 ml of juice). To increase the settling rate, a polyanionic flocculation aid (Praestol 2540TR) is subsequently added. The pre-liming juice is drained, set to a solids content of 20% by volume using a static decanter, and fed to a decanter centrifuge, which has an angle between the longitudinal axis of the centrifugal bowl and the generatrix of the conical portion of 8° and is operated at 10 to 30% of the maximum permissible torque. The pre-liming juice (inflow) is fed to the decanter centrifuge at 3000 l/h. The protein-containing fraction is removed from the pre-liming juice and discharged from the decanter centrifuge via the solids discharge, and the clear sugar beet pre-liming juice is discharged from the central outlet of the decanter centrifuge. The solids content of the protein-containing fraction is 38 to 42% by weight, and the solids quantity is 192 kg/h of dry substance. The sugar amount of the protein-containing fraction is 15 kg/h, and the solids content in the clear sugar beet pre-liming juice is 4 to 6% by volume.

EXAMPLE 2

(2) Comparison of different discharge angles between the longitudinal axis and generatrix of the conical portion of the centrifugal bowl

(3) Sugar beet raw juice is prelimed as in Example 1 and fed at 3000 L/h and a solids content of 20% by volume to various decanter centrifuges using different discharge angles of 5°, 8°, 10° and 15° between the longitudinal axis and the generatrix of the conical portion of the centrifugal bowl. The different decanter centrifuges are operated with different torques in each case to allow a removal of the coagulate. The protein-containing fractions separated by way of the different decanter centrifuges as well as clear sugar beet raw juices show differences in the solids content of the clear sugar beet pre-liming juice, as well as the sugar amount and the solids quantity and content of the protein-containing fraction (see Table 1). The use of a decanter centrifuge having an angle of 5° results in an increased amount of sugar as well as a low solids content (DS in % by weight) and a lower quantity of solids (kg/h) in the protein-containing fraction as well as in an increased solids content (in % by volume) in the clear sugar beet pre-liming juice. The use of a decanter centrifuge having an angle of 8° yields a particularly clear sugar beet pre-liming juice as well as a high solids content, a high quantity of solids and a lower sugar amount in the protein-containing fraction. The use of a decanter centrifuge having an angle of 10° likewise results in a comparable sugar amount and solids quantity as well as solids content of the protein-containing fraction. The decanter centrifuge having an angle of 15° is not able to separate the protein-containing fraction from the pre-liming juice, even when the maximum permissible torque is exceeded briefly.

(4) TABLE-US-00001 TABLE 1 Discharge angle ° 5 8 10 15 Inlet (pre-liming juice) l/h 3000 3000 3000 3000 Torque applied (% of max- % very <40%   40-80% >100% imum permissible torque) low Solids content in pre-liming % by 20 20 20 20 juice volume Clarified product (clear l/h 2400 2600 2650 3000 sugar beet pre-liming juice) Protein-containing l/h 600 400 350 — fraction Protein-containing kg/h 148 192 164 — fraction, solids quantity Protein-containing fraction % by 23 38-42 38-40 — (DS), solids content weight Sugar amount of the kg/h 22 15 15 — protein-containing fraction Solids content in the % by 12-14 4-6  8-12 — clear sugar beet pre- volume liming juice

EXAMPLE 3

(5) Comparison of the solids content in the inlet

(6) A pre-liming juice prepared according to Example 1 is set to a solids content of 10, 20 and 30% by volume by means of a static decanter. These differently set pre-liming juices are each added to a decanter centrifuge using a discharge angle of 8°. The use of a pre-liming juice having different solids contents lead to different results:

(7) The use of the pre-liming juice having a solids content of 10% by volume results in insufficient removal of the protein-containing fraction, and the use of the pre-liming juice having a solids content of 30% by volume results in an increased solids content in the clarified product (see Table 2). The use of a pre-liming juice having a solid content of 20% by volume results in a very clear sugar beet pre-liming juice and a high solids content in the protein-containing fraction.

(8) TABLE-US-00002 TABLE 2 Discharge angle ° 8 8 8 Inlet (pre-liming juice) l/h 3000 3000 3000 Torque applied (% of max- % <40% <40%   20-60% imum permissible torque) Solids content in pre-liming % by 10 20 30 juice volume Clarified product (clear l/h 2780 2600 2600 sugar beet pre-liming juice) Protein-containing fraction l/h 220 400 400 Protein-containing fraction, kg/h 100 192 192 solids quantity Protein-containing fraction % by 36-40 38-42 38-42 (DS), solids content weight Sugar amount of the protein- kg/h 9 15 15 containing fraction Solids content in the % by 2-3 4-6 16-20 clear sugar beet pre- volume liming juice

EXAMPLE 4

(9) A pre-liming juice produced according to Example 1 having a solids content of 15% by volume is added to a decanter centrifuge having a discharge angle of 10° (operated as described in Example 1). The obtained clear sugar beet pre-liming juice is collected and treated further. The protein-containing fraction having a solids content of 36% by weight is collected, diluted to a solids content of 20% by volume and added to a further decanter centrifuge. This further decanter centrifuge has a discharge angle of 8° and is operated at a torque of no more than 50% of the maximum permissible torque. The protein-containing fraction is thickened to a solids content of 45% by weight by way of the further decanter centrifuge.