Search

EP-4735878-A1 - MEASUREMENT SYSTEM FOR DETECTING BUBBLES

EP4735878A1EP 4735878 A1EP4735878 A1EP 4735878A1EP-4735878-A1

Abstract

A measurement system (10) for detecting bubbles in a tank (1) comprising: an acoustic sensor (20) configured to detect acoustic waves in the tank (1); a controller (30) configured to receive a signal indicative of the acoustic waves from the acoustic sensor (20), wherein the controller (30) is configured to: sample the signal received from the acoustic sensor (20) over a predetermined time period to generate a sampled signal; extract an envelope of the sampled signal; detect, based on the envelope of the sampled signal, acoustic events above a predetermined threshold value which are indicative of the presence of bubbles in the tank (1).

Inventors

  • TIPTON, Carl
  • WATSON, Benjamin Callum
  • STITT, EDMUND HUGH
  • REES, IAN DAVID
  • DONEV, Nikolche

Assignees

  • Johnson Matthey Public Limited Company

Dates

Publication Date
20260506
Application Date
20240628

Claims (20)

  1. 1. A measurement system for detecting bubbles in a tank comprising: an acoustic sensor configured to detect acoustic waves in the tank; a controller configured to receive a signal indicative of the acoustic waves from the acoustic sensor, wherein the controller is configured to: sample the signal received from the acoustic sensor over a predetermined time period to generate a sampled signal; extract an envelope of the sampled signal; detect, based on the envelope of the sampled signal, acoustic events above a predetermined threshold value which are indicative of the presence of bubbles in the tank.
  2. 2. A measurement system according to claim 1 , wherein the signal is sampled at a frequency of at least 40 kHz, preferably at least 50 kHz, more preferably at least 100 kHz.
  3. 3. A measurement system according to claim 1 or claim 2, wherein in order to extract the envelope of the sampled signal, the controller is configured to: determine a Hilbert transform of the sampled signal.
  4. 4. A measurement system according to claim 3, wherein prior to determining the Hilbert transform, the controller is configured to filter the sampled signal.
  5. 5. A measurement system according to claim 4, wherein the controller is configured to filter the sampled signal using a low pass filter.
  6. 6. A measurement system according to claim 5, wherein the controller is configured to low pass filter the sampled signal with a low pass filter having a cut-off frequency of no greater than 20 kHz.
  7. 7. A measurement system according to claim 4, wherein the controller is configured to filter the sampled signal by: determining a discrete wavelet transform (DWT) of the sampled signal, applying a threshold to the DWT of the sampled signal, and determining the inverse DWT of the thresholded DWT of the sampled signal.
  8. 8. A measurement system according to any of claims 1 to 7, wherein the controller is further configured to: determine a time period associated with the detected acoustic events occurring; and calculate a ratio of the time period to the predetermined time period in order to provide an indication of the amount of bubbles present in the tank.
  9. 9. A measurement system according to any of claims 1 to 8, wherein the predetermined time period is at least 0.2 s.
  10. 10 A measurement system according to any of claims 1 to 9, wherein the controller is further configured to output the sampled signal to a cloud-based storage medium.
  11. 11. A measurement system according to any of claims 1 to 10, wherein the acoustic sensor is configured to detect acoustic waves associated with air entrainment in a stirred tank and/or acoustic waves associated with bubbles generated as a reaction product within the tank.
  12. 12. A measurement system according to any of claims 1 to 11 , wherein the measurement system is configured to be used with a stirred tank, the measurement system further comprising a sensor configured to sense a rotational speed of a stirrer of the stirred tank, wherein the controller is configured to receive data indicative of the rotational speed of the stirred tank over the predetermined time period.
  13. 13. A measurement system according to claim 12, wherein the controller is further configured to control the rotational speed of the stirrer based on the detection of acoustic events above a predetermined threshold value which are indicative of the presence of bubbles in the stirred tank.
  14. 14. The measurement system of any of claims 1 to 13 when provided as part of a tank, optionally a stirred tank, wherein optionally the stirred tank is an unbaffled stirred tank or a baffled stirred tank.
  15. 15. The measurement system of any of claims 1 to 14, wherein prior to extracting the envelope, the controller is configured to transform the sampled signal using a discrete wavelet transform (DWT).
  16. 16. The measurement system of any of claims 1 to 15, wherein prior to extracting the envelope of the sampled signal, the controller is further configured to transform the sampled signal using a discrete wavelet transform, wherein the envelope is extracted from the transformed signal; and the controller is configured to detect acoustic events which are indicative of the presence of bubbles in the tank based on the envelope of the sampled signal using a trained machine learning model.
  17. 17. The measurement system of claim 16, wherein the controller is configured: to determine a plurality of events from the transformed signal, wherein each event is determined based on an average amplitude of the envelope over an event time period, wherein the controller is configured to detect acoustic events which are indicative of the presence of bubbles by classifying the plurality of events using the trained machine learning model.
  18. 18. The measurement system of claim 17, wherein the controller is configured to classify the plurality of events into a plurality categories comprising two or more categories selected from the group comprising: Machinery Noise with Bubbles, Machinery Noise with No Bubbles, Detached Sensor, Anomalous Sensor Reading, Background Machinery Noise, No Machinery Noise with Bubbles, No Machinery Noise with No Bubbles.
  19. 19. The measurement system of any of claims 16 to 18, wherein the controller is configured to transform the sampled signal using a discrete wavelet transform having a plurality of levels to generate a transformed signal comprising details coefficients and approximation coefficients for each of the plurality of levels.
  20. 20. The measurement system of claim 19, wherein an envelope is extracted from the details coefficients of one or more levels of the transformed signal and/or the approximations coefficients of one or more levels of the transformed signal.

Description

Measurement system for detecting bubbles Field of the disclosure The present disclosure relates to measurement systems. In particular, the present disclosure relates to the detection of bubbles using a measurement system. Background The manufacture of various liquids including paint, inks, emulsions, suspensions, slurries, and the like typically involves the stirring of the liquid being manufactured. Such stirring processes may be performed in a stirred tank, for example an unbaffled stirred tank. Typically, an unbaffled stirred tank comprises a cylindrical tank having smooth internal walls. A stirrer (e.g. an impeller) is located towards the bottom of the tank which is configured to rotate in order to stir the liquid within the tank. Stirring of the tank with the stirrer when a liquid is present generally results in the formation of a vortex above the stirrer. As the rotation speed of the stirrer increases, the vortex extends deeper into the liquid of the tank, towards the stirrer. Under certain conditions where the rotation speed of the stirrer is sufficiently high, the vortex may contact the stirrer, which may lead to air becoming entrained in the liquid. Air may be entrained in the liquid in the form of bubbles. For some manufacturing processes, it may be desirable to avoid air becoming entrained in the liquid being stirred (e.g. due to the above mechanism, or any other air entrainment mechanism). Against this background, the present disclosure seeks to provide an improved, or at least commercially relevant alternative, measurement system and method. Summary According to a first aspect of the disclosure, a measurement system for detecting bubbles in a tank is provided. The measurement system comprisesan acoustic sensor configured to detect acoustic waves in the tank and a controller configured to receive a signal indicative of the acoustic waves from the acoustic sensor. The controller is configured to sample the signal received from the acoustic sensor over a predetermined time period to generate a sampled signal, extract an envelope of the sampled signal, and detect, based on the envelope of the sampled signal, acoustic events above a predetermined threshold value which are indicative of the presence of bubbles in the tank. As such, the measurement system of the first aspect may use acoustic measurements to detect the presence of bubbles in a liquid provided within a tank, optionally a stirred tank. For many manufacturing processes, it is desirable to stir a liquid without air becoming entrained within the liquid (i.e. to prevent bubbles forming in the liquid). For some manufacturing processes in tank, the presence of bubbles in a tank (e.g. due to a reaction) may be indicative of the progress of the manufacturing process. The measurement system according to the first aspect can detect the formation and/or presence of bubbles within a tank in order to provide improved monitoring and/or control over the manufacturing process. Such a measurement system may be particularly applicable to the manufacture of liquids such as emulsions, suspensions, slurries, inks, paints, washcoats and the like. The measurement system may also be applicable to manufacturing processes involving precipitation stirring and other stirring processes where air entrainment is to be controlled, reduced, or eliminated. It will be appreciated that during stirring, stirred tanks in particular generate acoustic signals across a broad range of frequencies. Thus, separating out acoustic events associated with the presence of bubbles simply based on a frequency analysis of acoustic data from a stirred tank is challenging, as it is difficult to distinguish signals associated with bubbles from the background noise. Accordingly, the controller of the first aspect, processes the acoustic data to more accurately identify when bubbles are present in real-time. The measurement system of the first aspect provides a controller which is configured to interpret acoustic data from a tank in order to detect acoustic events associated with the presence of bubbles in the tank. In particular, the measurement system may be configured to detect the presence of bubbles in an unbaffled stirred tank or a baffled stirred tank, or any other type of stirred tank. In such embodiments, as the rotation speed of a stirrer in the stirred tank is increased, the likelihood of air becoming entrained (i.e. bubbles being present) increases. In particular, as rotation speed increases, a vortex may form in the stirred tank, wherein the depth of the vortex increases with rotation speed. Where the rotation speed is sufficient for the vortex to reach the stirrer (towards the bottom of the tank), air may become entrained in the stirred liquid. Due the relatively complex nature of the formation of a vortex within a stirred tank, it is challenging to predict in advance the rotation speed at which air entrainment may occur. The measurement system of the first aspect allows a st