Features Research & Innovation
Automation of a Microcontaminants Deposition Tester Relating the Rate of Deposition to the Pressure Drop Across a Collector

Automatisation d’un appareil d’essai de dpts de contaminants indiquant la vitesse de dpt lors de la chute de pression dans un collecteur

Abstract: The importance of organic microcontaminants (i. e. pitch and microstickies) as contributors to deposition problems in paper machines is recognized but there is no consensus in the industry on a microcontaminants definition and on monitoring method. Rather than measuring the quantity of pitch/microstickies in pulp or whitewater samples, we previously described a means of monitoring their deposition rate in forming fabrics because this is one of the most common deposit locations in paper mills using recycled pulps. In this report, we describe the automation of this dynamic deposition test, whose key feature is the continuous measurement of pressure across a fabric rather than the measurement of deposited material. The sigmoid shape of the deposition curve is explained by a change in flow regime as the pores of the fabric are progressively plugged. Capture of the P100 whitewater elements in the fabric is caused by a combination of overlapping phenomena such as surface pore deposition, pore bridging by fibrillar elements, and filtration of flowing elements when the pores start to be constricted. To obtain a measurable rate of deposition, the presence of lypophilic extractives is required both on the surface of the fines and also in the water phase, as colloidal particles.

Paper presented at 94th PAPTAC Annual Meeting in Montreal, February 5-7, 2008

Full manuscript available at www.paptac.ca.