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How to Detect Dirt and Shives in Pulp Slurries.

Author: David Zerr, VP of R&D, Pulmac Systems

Event: PEERS 2022

Abstract: Historically, pulp manufacturers rely on manual laboratory tests to measure dirt and shives in pulps. Lab testing provides an equivalent black area (EBA) which delivers parts per million (PPM) value. Most virgin fiber pulp producers have targets of ≤ 4 PPM. When dirt, shives, or other impurities surface in matters exceeding 4 PPM, it’s an all hands on deck to troubleshoot and remove the contamination source. Unfortunately, the pulp has already been produced into lap pulp and has to be rejected due to an out-of-spec limit breach. Several technologies have moved from the lab to the pulp dryer. These will be discussed. Latest technology takes this a step further into the pulping process, into the pulp slurry itself.

New Technology to Measure Dirt in Pulp Slurries: This paper will present a fast, high-end optics system that measures dirt particles, shives, and other impurities in the pulp suspension. Dot area, number of dots, average length, width and area, the grey scale of each dot, and shives are photographed and recorded every three minutes. Results are displayed as a PPM value along with dot size categorization of all findings and preset alarms to alert operations if the process breaches upper control limits. This allows corrective action long before the pulp hits the pulp dryer.

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