A new image analysis based instrument has been developed for measurement of contaminants with emphasis on heavy stickies and light macrocontaminants in deinked pulp or Whitewater. The unit is coupled to a pulp classifier that serves to separate the contaminants from pulp prior to their transfer to a chamber that facilitates image capture and analysis. When operating in the online mode with autosamplers delivering the samples to the pulp classifier, the instrument provides macrocontaminant determinations every 15 minutes. The total count and surface area of both light and heavy macrocontaminants per kilograms of pulp can then be sent by direct link to the mill data control system allowing an effective follow-up of macrocontaminant changes in process pulps and waters. The unit also allows the user to view images of the contaminants. The analyser results obtained in terms of number and area of macrocontaminants show a linear relationship with the Tappi standard method T-277. Because macrocontaminants are not flattened by a pressing step, the total area of the contaminants measured by the analyser is lower than that measured by the Tappi method but the value is more representative of the actual contaminant size as found in pulp slurry.
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