On-Line Debris Measurement in Pulp Suspensions by Means of Image Analysis, 1994 Process & Product Quality Conference Proceedings

S. J. Dougherty <>

Key issues relating to automated analysis of debris in pulp are considered. A system which addresses those issues is described. A unique sampling valve is used to extract and dilute only the amount of pulp needed for analysis. The sample consistency is between 0.005% and 1.0% depending upon the size and characteristics of the debris of interest. Debris between 10 micron and 10 mm diameter can be characterized. The sample, available at process pressure so that gases remain dissolved, is passed continuously through a windowed flow cell equipped with a CCD camera on one side and either a front light on the same side, or a back light on the other side. Halogen or LED array sources provide light at several wavelengths. The image information is processed through high speed node computers and then passed by LAN to a file server for presentation.

Procedures for validation of the method are given. Results are described for various furnishes and process positions, including long fiber/shive analysis, paper vs. liner grade discrimination, and screen performance.