DSP-based tension control and data acquisition for paper machine rewinding roll drive

The use of a new, technical, high-purity magnesium hydroxide-based peroxide bleaching additive was evaluated in full mill-scale trial runs on two target brightness levels. Trial runs were conducted at a Finnish paper mill using Norwegian spruce (Picea abies) as the raw material in a conventional pressurized groundwood process, which includes a high-consistency peroxide bleaching stage. On high brightness grades, the use of sodium-based additives cause high environmental load from the peroxide bleaching stage. One proposed solution to this is to replace all or part of the sodium hydroxide with a weaker alkali, such as magnesium hydroxide. The replacement of traditional bleaching additives was carried out stepwise, ranging from 0% to 100%. Sodium silicate was dosed in proportion to sodium hydroxide, but with a minimum dose of 0.5% by weight on dry pulp. The environmental effluent load from bleaching of both low and high brightness pulps was significantly reduced. We observed a 35% to 48% reduction in total organic carbon (TOC), 37% to 40% reduction in chemical oxygen demand (COD), and 34% to 60% reduction in biological oxygen demand (BOD7) in the bleaching effluent. At the same time, the target brightness was attained with all replacement ratios. No interference from transition metal ions in the process was observed. The paper quality and paper machine runnability remained good during the trial. These benefits, in addition to the possibility of increasing production capacity, encourage the implementation of the magnesium hydroxide-based bleaching concept.

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Microstructure simulation of early paper forming using immersed boundary methods

TAPPI Journal ◽

10.32964/10.32964/tj10.11.23 ◽

2011 ◽

Vol 11 (11) ◽

pp. 23-30 ◽

Cited By ~ 5

Author(s):

ANDREAS MARK ◽

ERIK SVENNING ◽

ROBERT RUNDQVIST ◽

FREDRIK EDELVIK ◽

ERIK GLATT ◽

...

Keyword(s):

Early Paper ◽

Contact Model ◽

Fiber Suspension ◽

Beam Equation ◽

Immersed Boundary ◽

Paper Machine ◽

Immersed Boundary Methods ◽

Element Discretization ◽

Microstructure Simulation ◽

Boundary Methods

Paper forming is the first step in the paper machine where a fiber suspension leaves the headbox and flows through a forming fabric. Complex physical phenomena occur as the paper forms, during which fibers, fillers, fines, and chemicals added to the suspension interact. Understanding this process is important for the development of improved paper products because the configuration of the fibers during this step greatly influences the final paper quality. Because the effective paper properties depend on the microstructure of the fiber web, a continuum model is inadequate to explain the process and the properties of each fiber need to be accounted for in simulations. This study describes a new framework for microstructure simulation of early paper forming. The simulation framework includes a Navier-Stokes solver and immersed boundary methods to resolve the flow around the fibers. The fibers were modeled with a finite element discretization of the Euler-Bernoulli beam equation in a co-rotational formulation. The contact model is based on a penalty method and includes friction and elastic and inelastic collisions. We validated the fiber model and the contact model against demanding test cases from the literature, with excellent results. The fluid-structure interaction in the model was examined by simulating an elastic beam oscillating in a cross flow. We also simulated early paper formation to demonstrate the potential of the proposed framework.

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Optical analysis of ink and other contaminants in process waters

TAPPI Journal ◽

10.32964/tj11.8.51 ◽

2012 ◽

Vol 11 (8) ◽

pp. 51-58

Author(s):

ANTTI HAAPALA ◽

MIKA KÖRKKÖ ◽

ELISA KOIVURANTA ◽

JOUKO NIINIMÄKI

Keyword(s):

Optically Active ◽

Process Water ◽

Paper Machine ◽

Optical Analysis ◽

Direct Process ◽

Active Components ◽

Water Contaminants ◽

Dependent Measurement ◽

Measurement Methodology

Analysis methods developed specifically to determine the presence of ink and other optically active components in paper machine white waters or other process effluents are not available. It is generally more interest¬ing to quantify the effect of circulation water contaminants on end products. This study compares optical techniques to quantify the dirt in process water by two methods for test media preparation and measurement: direct process water filtration on a membrane foil and low-grammage sheet formation. The results show that ink content values obtained from various analyses cannot be directly compared because of fundamental issues involving test media preparation and the varied methodologies used to formulate the results, which may be based on different sets of assumptions. The use of brightness, luminosity, and reflectance and the role of scattering measurements as a part of ink content analysis are discussed, along with fine materials retention and measurement media selection. The study concludes with practical tips for case-dependent measurement methodology selection.

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Impact of fiber structure on edge-wicking of highly-sized paperboard

TAPPI Journal ◽

10.32964/tj17.08.437 ◽

2018 ◽

Vol 17 (08) ◽

pp. 437-443

Author(s):

Lebo Xu ◽

Jeremy Meyers ◽

Peter Hart

Keyword(s):

Fiber Surface ◽

Manufacturing Processes ◽

Paper Machine ◽

Liquid Penetration ◽

Fiber Structure ◽

Cut Edge ◽

Local Fiber

Coffee edge-wicking testing was conducted on two groups of highly-sized paperboard manufactured at two mills with similar manufacturing processes, but with vastly different local fiber sources. Although the Hercules size test (HST) indicated similar internal size levels between the two types of board, the edge-wicking behavior was noticeably different. Analysis of fiber structure revealed that the board with more edge-wicking had fibers with thicker fiber walls, which kept the fiber lumen more open after pressing and drying on a paper machine. It was demonstrated that liquid penetration through voids between fibers in highly-sized paperboard was limited, because the fiber surface was well protected by the presence of sufficient sizing agent. Nevertheless, freshly exposed fiber walls and lumens at the cut edge of the sheet were not protected by sizing material, which facilitated edge-wicking. The correlation between fiber structure and edge-wicking behavior was highlighted in this work to inspire development of novel sizing strategies that protect the freshly cut edge of the sheet from edge-wicking.

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How to use alum with cationic dispersed rosin size

TAPPI Journal ◽

10.32964/tj15.5.331 ◽

2016 ◽

Vol 15 (5) ◽

pp. 331-335 ◽

Cited By ~ 3

Author(s):

LEBO XU ◽

JEREMY MYERS ◽

PETER HART

Keyword(s):

Zeta Potential ◽

Colloidal Particles ◽

Streaming Potential ◽

Excessive Amount ◽

Paper Machine ◽

Optimum Amount ◽

Potential Measurement ◽

Streaming Current ◽

Wide Range ◽

Laboratory Results

Retention of cationic dispersed rosin size was studied via turbidity measurements on stock filtrate with different alum and dispersed rosin size dosages. Stock charge characteristics were analyzed using both an analysis of charge demand determined via a streaming current detector and an evaluation of zeta potential of the fibers by streaming potential measurement. The results indicated that an optimum amount of alum existed such that good sizing retention was maintained throughout a wide range of dispersed rosin size dosages. However, when an excessive amount of alum was used and fines and colloidal particles were transitioned from anionic to cationic, the cationic size retention was reduced. Laboratory results were confirmed with a paper machine trial. All data suggested that a stock charge study was necessary to identify optimal alum dosage for a cationic dispersed rosin sizing program.

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