Refiner control

• US 20040022128A1
• Filed: 06/17/2003
• Published: 02/05/2004
• Est. Priority Date: 07/14/2000
• Status: Active Grant

• Current Assignee: ABB AB (ABB Limited)
• Original Assignee: ABB AB (ABB Limited)
• Inventors: Becka, Stefan, Liljenberg, Thomas, Thegel, Lennart
• Granted Patent: US 6,935,164 B2
• Time in Patent Office: Days
• US Class Current: 367/96
• CPC Class Codes: D21D 1/002 Control devices
• CPC Class Codes: D21D 1/30 Disc mills
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/02416 Solids in liquids
• CPC Class Codes: G01N 2291/02836 Flow rate, liquid level
• CPC Class Codes: G01N 2291/02872 Pressure
• CPC Class Codes: G01N 29/032 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00

Abstract

In the present invention a refiner (108) of a mechanical pulping line is supplied with a controllable acoustic source (14), arranged for emitting acoustic signals into the pulp fluid. The controllable acoustic signal is allowed to interact with the fibres in the pulp, and the acoustic (pressure) signals resulting from such an interaction is measured. At least one spectral component is measured. The measured spectral component is used to predict properties, content and/or size of the fibres. These properties may then be used to control the refiner (108) process. The used acoustic signal has preferably a wavelength that is large compared with a typical site of the particles.

Claims

1. A pulp refiner control method, comprising the step of:

measuring acoustic signals (22) from a pulp fluid (10), characterised by the further steps of;

emitting controllable acoustic signal into said pulp fluid (10) for interaction of said controllable acoustic signal (18) with fibres (12) in said pulp (10), being responsive to acoustic signals;

whereby said step of measuring of acoustic signals (22) comprises measuring of at least one spectral component resulting from said interaction of said controllable acoustic signal (18) and said fibres (12);

determining at least one process control parameter based on said measured acoustic signals (22); and

controlling a refiner process treating said pulp fluid (10).

2. A method according to claim 1, characterised in that said determining step in turn comprises the step of predicting, from said measured acoustic signals (22), properties of said fibres (12) in said pulp fluid (10), giving process control parameters for said refiner process.

3. A method according to claim 2, characterised in that at least one of said properties being selected from the list of:

mechanical property,

chemical property,

concentration,

shape, and

size.

4. A method according to any of the claims 1 to 3, characteris d in that measuring of acoustic signals (22) from said pulp fluid (10) is performed downstream relative to said refining process, providing a feed-back of the result of the refining process.

5. A method according to any of the claims 1 to 4, characterised in that measuring of acoustic signals (22) from said pulp fluid (10) is performed upstream relative to said refining process, providing a feed-forward from the pulp fluid entering the refining process.

6. A method according to any of the claims 1 to 5, characterised in that said emitted acoustic signal (18) is composed by acoustic waves having a large wavelength compared to a typical size of said fibres (12), and a typical distance between said fibres (12).

7. A method according to any of the claims 1 to 6, characterised in that said measured spectral component has a frequency below 20 kHz.

8. A method according to any of the claims 1 to 7, characterised in that said controlling step comprises the step of controlling at least one of the parameters of the following list

rate of entering chips/pulp,

distance between refining disks,

water addition flow,

pressure on refining disks,

refiner speed,

addition of dewatering agents, and

refiner power.

9. A method according to any of the claims 1 to 8, characterised by the further step of evaluating trends of measured acoustic signals for detecting ageing information of the refining disks.

10. A method according to any of the claims 1 to 9, characteris d in that said step of measuring spectral component(s) comprises measuring, for at least one frequency, at least one of the properties in the list of:

amplitude,

phase, and

time-delay.

11. A method according to claim 10, characterised in that said step of measuring spectral component(s) comprises measuring, for at least one frequency, at least two of the properties in the list of:

amplitude,

phase, and

time-delay.

12. A method according to any of the claims 1 to 11, characterised by the further step of tuning frequency/frequencies of said controllable acoustic signal (18) to characteristic frequencies of said fibres (12).

13. A method according to any of the claims 1 to 12, characterised in that said controllable acoustic signal (18) is pulsed and emitted during limited time intervals.

14. A method according to any of the claims 1 to 13, characterised by the further steps of:

amplitude modulating of said controllable acoustic signal (18); and

reducing background signals in said measured acoustic signals (22), based on said amplitude modulation.

15. A method according to any of the claims 2 to 14, characterised in that said step of predicting further comprises the step of predicting, from said measured acoustic signals (22), properties of paper manufactured by said pulp (10).

16. A method according to any of the claims 2 to 15, characteris d in that said step of predicting comprises multivariate statistical analysis of said measured acoustic signals (22).

34. A computer program product comprising computer code means and/or software code portions for making a processor perform the steps of any of the claims 1 to 16.

35. A computer program product according to claim 34 supplied via a network, such as Internet.

36. A computer readable medium containing a computer program product according to claim 34 or 35.

17. An apparatus for analysis of a pulp fluid (10) comprising:

acoustic signal sensor (24) for measuring acoustic signals from said pulp fluid (10); and

data processing means (28) connected to said acoustic signal sensor (24) for predicting, from said measured acoustic signals, mechanical/chemical properties of fibres (12) in said pulp fluid (10),

characterised by

acoustic signal source (14);

control means (16) for said acoustic signal source (14);

said acoustic signal source (14) being arranged to emit controllable acoustic signal (18) into said pulp fluid (10) for interaction with said fibres (12);

whereby said acoustic signal sensor (24) is arranged for measuring at least one spectral component resulting from said interaction of said controllable acoustic signal (18) and said fibres (12).

24. An apparatus according to any of the claims 17 to 23, characterised in that at least one of said properties being selected from the list of:

mechanical property,

chemical property,

concentration,

shape, and

size,

25. An apparatus according to any of the claims 17 to 24, characterised in that said acoustic signal sensor (24) has a small size compared to the wavelength of waves emitted by said acoustic signal source (14).

26. An apparatus according to any of the claims 17 to 25, characterised in that said acoustic signal sensor (24) is operable for frequencies below 20 kHz.

29. An apparatus according to any of the claims 17 to 28, characteris d in that said control means (16) comprises means for tuning the frequency/frequencies of said controllable acoustic signal (18) to characteristic frequencies of said fibres (12).

30. An apparatus according to any of the claims 17 to 29, characterised in that said control means (16) comprises means for causing said acoustic signal source (14) to emit during limited time intervals.

31. An apparatus according to any of the claims 17 to 30, characterised in that said control means (16) further comprises amplitude modulation means for said controllable acoustic signal (18) and in that the apparatus further comprises means for reducing background signals in said measured acoustic signals (22), connected to said control means (16), for receiving information about said amplitude modulation.

32. An apparatus according to any of the claims 17 and 19 to 31, characterised in that said data processing means (28) is further arranged for predicting, from said measured acoustic signals (22), properties of paper manufactured by said pulp (10).

33. An apparatus according to any of the claims 17 and 19 to 32, characterised in that said data processing means (28) comprises means for multivariate statistical analysis of said measured acoustic signals (22).

18. A refiner apparatus for handling a pulp fluid (10) comprising:

means (212) for carrying out a refiner process of said pulp fluid (10), acoustic signal sensor (24) for measuring acoustic signals from said pulp fluid (10),

characterised by;

acoustic signal source (14);

control means (16) for said acoustic signal source (14);

said acoustic signal source (14) being arranged to emit controllable acoustic signal (18) into said pulp fluid (10) for interaction with fibres (12) in said pulp fluid (10);

whereby said acoustic signal sensor (24) is arranged for measuring at least one spectral component resulting from said interaction of said controllable acoustic signal (18) and said fibres (12);

data processing means (28) containing a processor and connected to said acoustic signal sensor (24) for determination of at least one process control parameter based on said measured acoustic signals (22); and

process control means (105, 114, 116, 118) for controlling said means (212) for carrying out a refiner process according to said determined process control parameter(s).

19. An apparatus according to claim 18, characterised in that said data processing means (28) is further arranged for predicting, from said measured acoustic signals (22), said properties of said fibres (12) in said pulp fluid (10).

20. An apparatus according to claim 18 or 19, characterised in that at least one acoustic signal sensor (24) is positioned downstream relative to said means (212) for carrying out said refiner process, providing a feed-back of the result of the refiner process.

21. An apparatus according to claim 18, 19 or 20, characterised in that at least one acoustic signal sensor (24) is positioned upstream relative to said means (212) for carrying out said refiner process, providing a feed-forward from the process fluid (10) entering the refiner process.

22. An apparatus according to any of the claims 18 to 21, characterised in that said process control means (105, 114, 116, 118) comprises means for controlling of at least one of the parameters of the following list:

rate of entering chips/pulp,

distance between refining disks,

water addition flow,

pressure on refining disks,

refiner speed,

addition of dewatering agents, and

refiner power.

23. An apparatus according to any of the claims 18 to 22, characterised by means for evaluating trends of measured acoustic signals (22) for detecting ageing information of the refining disks (110, 112).

27. An apparatus according to any of the clams 17 to 26, characterised in that said acoustic signal sensor (24) is arranged for measuring, for at least one frequency, at least one of the properties in the list of:

amplitude,

phase, and

time-delay.

28. An apparatus according to claim 27, characterised in that said acoustic signal sensor (24) is arranged for measuring, for at least one frequency, at least two of the properties in the list of:

amplitude,

phase, and

time-delay.