Understanding the Limits of a Screening Operation. Part 1: Characterization of Screen Plugging

Abstract

Pressure screening is a critical step in the production of high-quality paper. In efforts to meet sustainable market demands, mill operators are forced to push the limits of screening operation to the point where plugging becomes a recurrent issue. This two-part study provides insights into the limits of screening operations. In the first part, some published imaging data was analyzed to delve into the plugging mechanisms. The observed hysteresis and intermittency were measured by image processing techniques, which revealed that an intermittent behavior of plug-and-release events is intensified as permanent, stable plugs start to form. The intermittency was characterized as changes in the distribution of open area fluctuation peaks. Thus, the kurtosis of the fluctuation peak distribution is proposed as a metric for a plugging soft-sensor. In part 2 of this investigation, the limits of screening operation were characterized by performing a series of screening trials. The utility of the soft-sensor metric for plugging was assessed with the pressure fluctuation data.

Keywords

• pressure screen
• plugging
• rotor speed
• intermittency
• hysteresis