System and Method of Producing Micro Fibrillated Cellulose (MFC)

Abstract

The invention relates to a system of producing MFC (micro fibrillated cellulose) having a process device (30) of a pulper, a refiner or a screen configured to process MFC suspension to consistency of 0.5-5%. The system has a continuous pressing means (15; 25, 26) configured to dry the MFC suspension to a consistency of 6-60%. A method of producing MFC has at least one process stage (30) which processes a MFC suspension to a consistency of 0.5-5% by a process device (30). In the process stage the MFC suspension is pulped in a pulping stage in a pulper and/or refined in a refining stage by a refiner and/or screened in a screening stage by a screen. The MFC suspension having the consistency of 0.5-5% is dried in a drying stage of continuous pressing (15, 25, 26) by continuous a pressing device (15, 25, 26) to a consistency of 6-60%.

Claims

1. A system for producing Micro Fibrillated Cellulose (MFC), the system comprising: at least one process device configured to process a MFC suspension to a consistency of 0.5-5%; at least one continuous pressing device configured to dry the MFC suspension to a consistency of 6-60%; a measuring device arranged after the continuous pressing device and configured to measure the consistency of the MFC suspension; and a control device configured to control at least one operation parameter affecting the consistency of the MFC suspension based on the measured consistency of the MFC suspension.

2. The system of claim 1 wherein the continuous pressing device forms a source of a filtrate, and further comprising: a measuring device configured to measure a fines content of the filtrate; and a control device configured to guide at least part of the filtrate back to the at least one process device.

3. The system of claim 1 wherein the at least one process device comprises a pulper.

4. The system of claim 1 wherein the at least one process device comprises a refiner.

5. The system of claim 1 wherein the at least one of process device comprises a screen.

6. The system of claim 1 wherein the at least one continuous pressing device comprises a twin wire press in which the MFC suspension is transported through the twin wire press between two wires, each wire forming a wire loop guided by guides or tension rolls, wherein the wire loops have a common run where the MFC suspension is guided between the two wires during the common run; wherein at least one press roll is located inside one of the wire loops and a counter roll to the press roll is located opposite to the press roll inside the other wire loop to form a pressing nip for removing water from the MFC suspension.

7. The system of claim 6 wherein the twin wire press comprises more than one press roll-counter roll pair and more than one pressing nip along the twin wire common run.

8. The system of claim 6 wherein the control device is configured to control at least one operation parameter, and controls wire tension to control the continuous water removal by the continuous pressing device.

9. The system of claim 6 wherein the control device is configured to control at least one operation parameter, and controls nip pressure to control the continuous water removal by the continuous pressing device.

10. The system of claim 6 wherein the control device is configured to control at least one operation parameter, and controls pressing rotation speed.

11. The system of claim 6 wherein the control device is configured to control at least one operation parameter, and controls pressing water removal rate.

12. The system of claim 1 wherein the at least one continuous pressing device comprises a twin roll press in which the MFC suspension is transported by a fabric through at least one pressing nip formed between a press roll and a counter roll.

13. The system of claim 12 wherein the twin roll press comprises a plurality of pressing nips each formed between two rolls forming a press roll and a counter roll.

14. A system for producing Micro Fibrillated Cellulose (MFC) the system comprising: at least one process device configured to process an MFC suspension to a consistency of 0.5-5%, which system further comprises at least one continuous pressing device configured to dry the MFC suspension to a consistency of 6-60%; and wherein the continuous pressing device forms a source of a filtrate, and further comprising a measuring device configured to measure a fines content of the filtrate, and a control device configured to guide at least part of the filtrate back to the at least one process device.

15. The system of claim 14 wherein the at least one process device comprises a pulper.

16. The system of claim 14 wherein the at least one of process device comprises a refiner.

17. The system of claim 1 wherein the at least one of process device comprises a screen.

18. A method of producing Micro Fibrillated Cellulose (MFC), comprising the steps of: pulping an MFC suspension having a consistency of 0.5-5%; following pulping, refining the MFC suspension having the consistency of 0.5-5%; following the refining, screening the MFC suspension having the consistency of 0.5-5%; 15 following the screening, dewatering the MFC suspension in a continuous pressing device to a consistency of 6-60%, wherein the continuous pressing device forms a source of filtrate, such that a filtrate is produced therefrom; following dewatering, measuring the MFC suspension consistency and measuring a fines content of the filtrate; and controlling the dewatering of the MFC suspension to a consistency of 6-60% by controlling the dewatering of the MFC suspension, and by controlling return of at least a part of the filtrate back to the pulping step, the refining step, or the screening step.

19. The method of claim 18 wherein the step of dewatering the MFC suspension to a consistency of 6-60% is controlled with the continuous pressing device, wherein the continuous pressing device is a screw press, a twin wire press or a twin roll press, adjusted to increase or decrease dewatering based on the measuring the MFC suspension consistency following the step of dewatering.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is shown schematically as an example of the system and the method of producing micro fibrillated cellulose (MFC).

[0025] FIG. 2 is shown schematically as another example of the system and the method of producing micro fibrillated cellulose (MFC).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] During the course of the following description like numbers and signs will be used to identify like elements according to the different views which illustrate the invention and its advantageous examples. In the figures some repetitive reference signs have been omitted for clarity reasons.

[0027] In FIG. 1 is shown schematically an example of the system and the method of producing Micro Fibrillated Cellulose (MFC). The system and the method 10 in this example comprises at least one process stage 30 by at least one process device 30, in which the MFC suspension is pulped in at least one pulping stage 30 in at least one pulper 30 and/or refined in at least one refining stage 30 by at least one refiner 30 and/or screened in at least one screening stage 30 by at least one screen 30. The system and the method 10 may also comprise other process stages 30 for processing the MFC suspension. In the system and in the method 10 in at least one stage 11 after at least one of the process stages 30, the MFC suspension has a consistency of 0.5-5%, at which stage 11 the MFC suspension is dried in at least one drying stage of continuous pressing 15 by at least one continuous pressing means 15 to a consistency of 6-60%, advantageously to a consistency of 10-40%, more advantageously to a consistency of 20-30%, for a dried MFC material in a ready stage 12.

[0028] In FIG. 2 is shown schematically another example of the system and the method of producing micro fibrillated cellulose (MFC). The system and the method 20 in this example comprises at least one process stage 30 by at least one process device 30, in which the MFC suspension is pulped in at least one pulping stage 30 in at least one pulper 30 and/or refined in at least one refining stage 30 by at least one refiner 30 and/or screened in at least one screening stage 30 by at least one screen 30. The system and the method 10 may also comprise other process stages 30 for processing the MFC suspension. In the system and in the method 20 in at least one stage 21 after at least one of the process stages 30, the MFC suspension has a consistency of 0.5-5%, at which stage 21 the MFC suspension is dried in at least one first drying stage of continuous pressing stage 25 by at least one first continuous pressing means 25 to a consistency of 6-15%, at which stage 22 the MFC suspension is dried in at least one second drying stage of continuous pressing stage 26 by at least one second continuous pressing means 26 to a consistency of 20-60% for a dried MFC material in a ready stage 27.

[0029] In the examples of the FIGS. 1 and 2 after the drying stage of the continuous pressing 15, 25, 26 consistency and/or fines content of the MFC suspension is measured by on-line or off-line measurement means 40, for example by filtrate and/or dried MFC quality measurement means such, as fines levels and/or consistency, and the received measurement data is used to control operation parameters of the continuous pressing by a control means 50, for example by a computer controller or manually, for example to adjust pressing load and/or pressing speed and/or water removal amount and/or water removal rate and/or dilution degree in the continuous pressing stage 15, 26, 26.

[0030] In the examples of the FIGS. 1 and 2 the drying by the continuous pressing 15, 25, 26 of the micro fibrillated cellulose (MFC) is provided by screw press pressing by a screw press and/or twin wire pressing by a twin wire press and/or twin roll pressing by a twin roll press.

[0031] In the examples of the FIGS. 1 and 2 in the system and in the method 10, 20 of producing micro fibrillated cellulose (MFC), filtrate 13, 23, 24 from the drying stage of the continuous pressing 15, 25, 26 is at least partially guided back to one of the previous stages 30 of processing the MFC, for example to a pulping stage and/or to a refining stage and/or to a screening stage.

[0032] In the description in the foregoing, although some functions have been described with reference to certain features and examples, those functions may be performable by other features and examples whether described or not. Although features have been described with reference to the certain examples, those features may also be present in other examples whether described or not.

[0033] Above only some advantageous examples of the invention have been described to which examples the invention is not to be narrowly limited, and many modifications and alterations are possible within the invention.