Applied Real-Time Acoustic Chemometrics for Measurements of Canadian Standard Freeness

• In this paper we present a method for measuring Canadian Standard Freeness (CSF) on-line in real-time using acoustic measurements. The method can be used to present a new CSF value every second. The higher measurement rate and the reduced time-delay compared to conventional pulp sensors make it a suitable tool for improved refiner control. The method was developed during full-scale trials on two separate Sunds Defibrator double disc refiners at SCA Ortviken, Sweden. Acoustic measurements were performed using an accelerometer affixed to the refiner blow line. Trial conditions have been varied over a wide range of pulp quality and disturbances in the vibration signal. CSF was for example varied in the range 62-453 ml and refiner-housing pressure was varied from 0,35 to 0,39 MPa. The vibration signals collected during I second were treated to yield power spectra that were used for all further work. A median spectrum was calculated for each experimental point and these spectra were combined with reference values for freeness to make up the calibration matrices. The spectra were pre-treated using Orthogonal Signal Correction (OSC) and Subsequently Partial Least Squares Regression (PLSR) was used to build models between spectra and freeness. For model validation leave-one-out cross validation has been used. Over the range 90-250 ml we can predict CSF from median power spectra with a Root Mean Square Error of Prediction (RMSEP) of 23 ml. Over the larger CSF range of 62-453 mt the RMSEP deteriorates to 39 mt. Data from two separate trials on different refiners and from different seasons were included in these models.

Ämnesord

NATURVETENSKAP  -- Kemi -- Analytisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Analytical Chemistry (hsv//eng)

Nyckelord

pulp quality control; CSF; TMP; process sensor; sound; acoustics; chemometrics; digital signal processing

Analytical chemistry

Analytisk kemi

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)