ACOUSTIC EMISSION SYSTEM AND METHOD FOR PREDICTING EXPLOSIONS IN DISSOLVING TANK

• US 20170131240A1
• Filed: 10/25/2016
• Published: 05/11/2017
• Est. Priority Date: 11/06/2015
• Status: Active Grant

• Current Assignee: Andritz Incorporated
• Original Assignee: Andritz Incorporated
• Inventors: Aura, Kari Aatos, Timotheo, Alvaro Moura
• Granted Patent: US 10,012,616 B2
• Time in Patent Office: Days
• CPC Class Codes: D21C 11/00 Regeneration of pulp liquors or effluent waste waters
• CPC Class Codes: D21C 11/10 Concentrating spent liquor by evaporation evaporators B01D
• CPC Class Codes: D21C 11/12 Combustion of pulp liquors
• CPC Class Codes: D21C 11/122 Treatment, e.g. dissolution, of the smelt
• CPC Class Codes: D21G 9/0009 Paper-making control systems
• CPC Class Codes: G01N 29/02 Analysing fluids using acoustic emission techniques G01N29/14 ; constructional or flow details for analysing fluids G01N29/222; optoacoustic fluid cells G01N29/2425
• CPC Class Codes: G01N 29/4481 Neural networks

Abstract

The present disclosure describes a system for predicting explosions in a dissolving tank. The system includes acoustic emission sensors placed in or around the dissolving tank. By filtering the recorded frequencies to the range which is most sensitive for desired explosions “fingerprints,” it is possible to predict a smelt influx before the smelt influx occurs as well as program response actions to prevent compromising explosions.

Claims

1. A system comprising:

a dissolving tank adjacent to a recovery boiler,

a smelt spout having a first end proximate a recovery boiler and a second end opposite the first end, the second end being proximate a dissolving tank, wherein the smelt spout is configured to receive a smelt from the recovery boiler and convey the smelt to the dissolving tank;

an acoustic emission sensor having a reading end configured to detect acoustic emissions emanating from the smelt contacting a liquid in the dissolving tank, and wherein the acoustic emission sensor has a transducer in signal communication with the reading end, and wherein the transducer is configured to transduce the acoustic emissions into an initial electric signal;

a pre-processor configured amplify, filter, and digitize the initial electric signal to produce a pre-processed signal having a frequency of greater than 20 KHz, wherein the pre-processor is disposed downstream of the transducer;

a data processor in signal communication with the pre-processor, wherein the data processor is configured to transform the pre-processed signal with a transformation method to produce an output signal, wherein the output signal comprises a first set of processed waveforms representative of a first rate of smelt flow, and a second set of waveforms representative of a second rate of smelt flow, the second set of processed waveforms having amplitude peaks exceeding the first set of processed waveforms by more than 200% to comprise a pre-influx fingerprint.

2. The system of claim 1 further comprising the smelt disposed in the smelt spout.

3. The system of claim 1, wherein the acoustic emission sensor is disposed within the dissolving tank, within a wall of the dissolving tank, within a roof of the dissolving tank, within a base of the dissolving tank, or adjacent to the dissolving tank.

4. The system of claim 1, wherein the first end of the smelt spout is disposed in, engaged to, or extending toward the recovery boiler and the second end of the smelt spout is, disposed over, engaged to, or extending toward a dissolving tank.

5. The system of claim 1 further comprising a computer, wherein the computer is configured to detect the pre-influx fingerprint and restrict smelt flow into the dissolving tank after detecting the pre-influx fingerprint.

6. The system of claim 5, wherein the computer changes a process condition in response to detecting the pre-influx fingerprint.

7. The system of claim 5, wherein the pre-influx fingerprint further comprises a third set of processed waveforms having amplitudes below average amplitudes of the first set of processed waveforms, and wherein the computer initiates a response upon detection of the third set of processed waveforms.

8. The system of claim 1, wherein the data processor is an FPGA processor, wherein the FPGA processor transforms the pre-processed signal and continuously displays an intensity of chosen frequency bands in the second set of wave forms.

9. The system of claim 8, wherein the pre-influx fingerprint further comprises at least two amplitude peaks of the second set of waveforms exceeding the average amplitude of the first set of waveforms by at least 300% within a pre-defined time interval.

10. The system of claim 1, wherein the pre-processed signal has a frequency of greater than 100 KHz.

11. The system of claim 1, wherein the transformation method is selected from the group consisting of a continuous counting method, a Fast Fourier Transform, a root mean square method, a standard deviation method, a skewness method, a kurtosis method, a mean method, a variance method, a fuzzy logic method, and a neural network method.

12. The system of claim 1, wherein the acoustic emission sensor is selected from the group consisting of a piezoelectric sensor, an MEMS sensor or other acoustic emission sensor.

13. The system of claim 1, further comprising multiple acoustic emission sensors, and wherein each acoustic emission sensor further comprises a wave guide.

14. The system of claim 13, wherein the data processor transforms pre-processed signals produced by the multiple acoustic emission sensors.

15. The system of claim 13, wherein a wave guide extends into the liquid in the dissolving tank and a wave guide on a second acoustic sensor extends into a fluid emitted from the disruptor.

16. The system of claim 13, wherein an acoustic emission sensor of the multiple acoustic emission sensors extends through a wall of the dissolving tank or a top of the dissolving tank.

17. The system of claim 13, wherein an acoustic emission sensor of the multiple acoustic emission sensors is disposed proximate to the dissolving tank and outside of the dissolving tank.

18. The system of claim 1, wherein the first set of waveforms maps to a horizontal line representing the average amplitude of the first set of waveforms and wherein the horizontal line is a baseline level of activity.

19. The system of claim 1 further comprising a display, wherein the display displays the output signal as a continuous frequency spectrum display, a long-time envelope, or by displaying merely portions of the signal in the first set of processed waveforms.

20. The system of claim 1, wherein the pre-influx fingerprint further comprises a count trend and a Fast Fourier Transform trend, wherein the count trend depicts decreasing banging intensity in the dissolving tank prior to frequency bands in the Fast Fourier Transform trend surpassing the first set of processed waveforms by more than 300%.

21. The system of claim 5, wherein the pre-influx fingerprint further comprises a cyclic pre-influx fingerprint having repeating amplitude decay pre-influx fingerprints.

22. The system of claim 21, wherein the computer initiates a response after detecting the pre-influx fingerprint.

23. The system of claim 5, wherein the pre-influx fingerprint further comprises a prolonged pre-influx fingerprint and wherein the computer initiates a response after detecting the prolonged pre-influx fingerprint.

24. The system of claim 1, wherein the pre-influx fingerprint further comprises two or more amplitude peaks in the second set of processed waveforms surpassing a threshold within a pre-defined time interval.

25. The system of claim 1 further comprising a first floating threshold defined by the average amplitudes of the first set of processed waveforms and a second floating threshold defined by the second set of processed waveforms, wherein the pre-influx fingerprint further comprises a transition from the first floating threshold to the second floating threshold, wherein the second floating threshold exceeds the first holding threshold by at least 100%.

26. The system of claim 1, wherein the liquid in the dissolving tank is green liquor.

27. A method for predicting a smelt influx in a dissolving tank comprising:

detecting acoustic emissions emanating from smelt banging in a dissolving tank with an acoustic emission sensor;

generating an initial electric signal representing the acoustic emissions;

amplifying the initial electric signal to produce an amplified signal;

filtering the initial electric signal to a frequency range above 20 KHz to produce a filtered signal;

converting the initial signal from an analog signal to produce a digital signal, wherein a pre-processed signal comprises the amplified signal, filtered signal, and digital signal;

transforming the pre-processed signal with a data processor, wherein the data processor transforms the pre-processed signal with a transformation method, wherein the transformed pre-processed signal is an output signal;

outputting the output signal, wherein the output signal comprises a first set of processed waveforms representing a first rate of smelt flow, and a second set of waveforms representing a second rate of smelt flow, the second set of processed waveforms have having amplitude peaks exceeding the first set of processed waveforms by more than 200%, and wherein the first set of processed waveforms and the second set of processed waveforms comprise a pre-influx fingerprint.

28. The method of claim 27 further comprising comparing multiple pre-processed signals in a programmed frequency range from multiple acoustic emission sensors.

29. The method of claim 27 further comprising transmitting the output signal to a computer and restricting smelt flow into the dissolving tank after a computer detects a pre-influx fingerprint.

30. The method of claim 27 further comprising transmitting the output signal to a computer and changing a process condition after the computer detects a pre-influx fingerprint.

31. The method of claim 30, wherein the pre-influx fingerprint further comprises a third set of processed waveforms having amplitudes below the average amplitudes of the first set of processed waveforms.

32. The method of claim 27, wherein the transformation method is selected from the group consisting of a continuous counting method, a Fast Fourier Transform, a root mean square method, a standard deviation method, a skewness method, a kurtosis method, a mean method, a variance method, a fuzzy logic method, and a neural network method.