A new online image analyzer for macrocontaminants in recycled pulps

Abstract

A new image analysis-based instrument has been developed for measurement of low density and high density macrocontaminants from recycled pulp or whitewater. The unit is coupled to a pulp classifier that isolates the contaminants from pulp and concentrates them before their transfer to a specialized chamber that further separates the contaminants based on their relative density to water. The low density contaminants float on the water surface, whereas the high density macrocontaminants sink onto the settling plate, where images of both contaminant types are then captured and analysed. Through image analysis, the high density contaminants are further classified into two categories: contaminants that are whitish in color and mainly comprised of stickies are named heavy stickies, whereas contaminants that are blackish in color and comprised of black toners and dark wood components are named dirt. When operating in the online mode with autosamplers delivering the samples to the pulp classifier, the instrument provides macrocontaminant determinations every 15 min. The total count and surface area of both types of 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 analyzer results obtained in terms of number and area of macrocontaminants show a linear relationship with TAPPI T-277 om-07 “Macro stickies content in pulp: the ‘pick-up’ method.”