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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. [ABSTRACT FROM AUTHOR]

Recycled fiber-based papermaking in America is experiencing a persistent reduction in the strength of the incoming fiber. To maintain paper strength properties, paper mills respond by increasing basis weight, dry strength, etc. On average, the fiber cost component in recycled paper is approximately 40% of the total manufacturing cost. Increased fiber weight results in higher operating cost and has a negative effect on production rate, especially on dryer-limited paper machines. Increased pH and use of certain enzymes can improve strength during subsequent refining. The ProLab refiner was used to generate laboratory refining curves to evaluate changes in fiber bonding. The effect of pH and enzymes pretreatment on the strength development and change in drainage of recycled fibers with refining was evaluated. [ABSTRACT FROM AUTHOR]

The present work focused on characterizing the chemical and structural properties of isolated lignin from six hardwoods and their kraft pulps in an attempt to better understand the relationship between lignin's chemical properties and resultant oxygen delignification performance. Several hardwood samples were cooked under the same conditions with varying alkali charges to obtain unbleached pulps with kappa numbers between 19 and 20. These pulps were then subjected to an oxygen delignification stage. Both processes were evaluated for pulp quality, residual lignin, and O-stage delignification efficiency. The oxygen delignification stage was carried out under fixed conditions and evaluated with regards to kappa number, which was corrected for hexenuronic acid (HexA) contributions. Results revealed that different hardwood species exhibited differing oxygen delignification efficiencies. A high correlation was found between the O-stage delignification efficiency and the content of phenolic groups in the unbleached lignin, which confirmed that free phenolic groups are the reactive site for molecular oxygen attack. When different hardwood species were compared, the HexA contents were not found to affect O-stage delignification efficiencies. [ABSTRACT FROM AUTHOR]

The current trend to further reuse water within paper mills has resulted in more accumulated salts, as reflected by increased conductivity values. Although conductivity measurement is widely used in paper mills, its fundamental principles and interpretation are not often fully understood. This keeps papermakers from reaching the full benefits of using conductivity measurements to help manage the wet end chemistry of paper or board machines. High and variable conductivity affects the intrinsic properties of pulps, the performance of chemical additives, and the interaction between them. This paper reviews principles of conductivity; its measurement; its effect on important aspects of papermaking operations, such as retention, drainage, sizing, strength development and deposit control; and the fundamentals behind the effects of conductivity on the papermaking process. Specific mill examples are also provided. Potential solutions for operating a mill under high and variable conductivity conditions are discussed. [ABSTRACT FROM AUTHOR]

The use of eucalyptus as a partial replacement for mixed southern hardwoods can result in significant amounts of eucalyptus bark being incorporated into the chips going to the digester. When eucalyptus is first harvested, the bark peels off in large sheets, which will pass through chippers designed for southern hardwood. After being cut for more than about 4-6 weeks, the bark tightens onto the bole of the tree and again passes through chippers not designed for eucalyptus. As a result, significant quantities of eucalyptus bark could go to the digester. This study describes the effect of pulping eucalyptus bark in the laboratory. A series of control studies were performed on eucalyptus and mixed southern hardwood bark. The results show that incorporating bark into the cook results in increased kappa number, decreased pulp yield, and increased alkali consumption. If the percentage of applied active alkali is increased to counteract the increased alkali consumption, increased hexenuronic acid is generated. [ABSTRACT FROM AUTHOR]

The impact of commercially prepared, fully bleached pulp viscosity variation on handsheet physical properties was evaluated at different levels of pulp refining. Hardwood pulps from the same brownstock species mix, cooking parameters, and kappa numbers were processed through two different commercial bleach plants: one with a D0 (EP)D1D2 sequence and the second with an OD0 (EOP)D1 sequence. Additionally, a commercial softwood (predominately Scotts pine) brownstock pulp bleached by an OD0 (EP)D1D2 sequence was employed in this study. Pulps with viscosities ranging from 14 to 21 mPa·s were refined in a Valley beater to two freeness levels, and the associated handsheet physical properties were measured in this study. Over the pulp viscosity range of 14 to 21 mPa·s, no clear correlation was found to exist between pulp viscosity and related paper physical properties. Finally, a series of laboratory prepared bleached pulps were purposely prepared under non-ideal conditions to reduce their final viscosities to lower values. Handsheets made from these pulps were tested in their unbeaten condition for physical strength properties. Significant and rapid strength loss occurred when the measured pulp viscosity dropped below 12 mPa·s; overall strength properties showed no correlation to viscosity above the critical 12 mPa·s value. [ABSTRACT FROM AUTHOR]

The WestRock mill in Covington, VA, USA, initiated a long term diagnostic and optimization program for all three of its bleaching lines. Benchmarking studies were used to help identify optimization opportunities. Capital expenditures for mixing improvement, filtrate changes, equipment repair, other equipment changes, and species changes were outside the scope of this work. This focus of this paper is the B line, producing southern hard-wood pulp in a D(EP)DD sequence at 88% GE brightness. The benchmarking study and optimization work identified the following opportunities for improved performance: nonoptimal addition of caustic and hydrogen peroxide to the (EP) stage, carryover of D0 filtrate to the (EP) stage, and carryover of (EP) filtrate to the D1 stage. As a result of actions the mill undertook to address these opportunities, D0 kappa factor decreased about 5%, sodium hydroxide consumption in the (EP) stage decreased about 35%, chlorine dioxide consumption in the D1 stage decreased about 25%, and overall bleaching cost decreased about 15%. Application: A long term, sustainable, bleach plant optimization and cost reduction study was performed with minimal to no capital. Mills can apply similar methodologies to their own 'bleach plants and obtain reasonable results. [ABSTRACT FROM AUTHOR]

An automated shower water control system has been implemented to reduce the volume and variability of weak black liquor being sent from the pulp mill to the evaporators. The washing controls attempt to balance the need for consistent and low soda carryover to the bleach plant with consistently high weak black liquor solids being sent to the evaporators. The washer controls were implemented on two bleachable grade hardwood lines one with oxygen delignification, one without oxygen delignification) and one pine line. Implementation of the control program resulted in an increase in black liquor solids of 0.6 percentage points for the hardwood lines. Significant foam reduction was realized on the pine line since the pine black liquor solids were able to be consistently maintained just below the soap separation point. Low black liquor solids excursions to the evaporators were eliminated. Bleach plant carryover was stabilized and no negative impact on chemical consumption was noticed when controlling weak black liquor solids to recovery. Application: This information can be used by kraft mills around the world. The authors have provided an easy approach to control brownstock washing and maximize pulp production by avoiding evaporator capacity reduction. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The MWV mill in Covington, VA, USA, experienced a long term trend of increasing episodes of paper indents that resulted in significant quantities of internal rejects and production downtime. When traditional troubleshooting techniques failed to resolve the problem, big data analysis techniques were employed to help determine root causes of this negative and increasingly frequent situation. Nearly 6000 operating variables were selected for a deep dive, multi-year analysis after reviewing mill-wide process logs and 60000+ PI tags (data points) collected from one of the major data historian systems at the MWV Covington mill. Nine billion data points were collected from November 2011 to August 2014. Strategies and methods were developed to format, clean, classify, and sort the various data sets to compensate for process lag time and to align timestamps, as well as to rank potential causes or indicators. GE Intelligent Platforms software was employed to develop decision trees for root cause analysis. Insights and possible correlations that were previously invisible or ignored were obtained across the mill, from pulping, bleaching, and chemical recovery to the papermaking process. Several findings led the mill to revise selected process targets and to reconsider a step change in the drying process. These changes have exhibited significant impacts on the mill's product quality, cost, and market performance. Mill-wide communications of the identified results helped transform the findings into executable actions. Several projects were initiated. [ABSTRACT FROM AUTHOR]

MWV Forestry has been actively pursuing the establishment of cold- and frost-tolerant eucalyptus plantations in southeast Texas and in the higher, frost-prone regions of southern Brazil for several years. Currently, the major species being examined is Eucalyptus benthamii. Interspecific crossing efforts, cold tolerance established from field trials, and intercountry cooperation in this program are discussed. The ability of the southeastern Texas program to return value to our collaborators in southern Brazil and other locations is reviewed. Pulp and papermaking properties of the cold-tolerant species are also reviewed. Currently, E. benthamii plantations in southeast Texas are producing trees with a density range of about 460-523 kg/m3, suggesting some degree of genetic variability within the bulk seeds currently being employed. Good pulping yields of around 48% on o.d. wood have been obtained in laboratory studies. For comparison, this yield is about 3 percentage points higher than for traditional mixed southern hardwoods. In general, the physical properties of pure E. benthamii are inferior to those of mixed southern hardwoods. When used in a blend, the differences in physical properties are substantially mitigated. [ABSTRACT FROM AUTHOR]

We used two different experimental methods to study the effects of sheet temperature at a given moisture content on web densification and sheet smoothness. Commercially prepared paperboard obtained from the WestRock Mahrt mill in Cottonton, AL, USA, was used in this study. Laboratory made handsheets prepared from Mahrt high yield kraft pine pulp were also used for portions of this work. Sheets were sealed in moisture-proof bags, heated to various temperatures, and calendared at multiple nip loads. The resulting changes in sheet density were determined. Additionally, a pilot-scale calendar was modified to preheat the non-print side of the sheet before entering the nip. The modified sheet run allowed for an increase in the bulk temperature of the board with minimal changes in the moisture content of the print surface. Increasing the bulk temperature increased board density at a given print surface smoothness. We determined that increasing the board temperature by 14°C resulted in about a 1% increase in board density. The results of this study help explain the commercial results obtained with thermal gradient calendaring. [ABSTRACT FROM AUTHOR]