Atlanta, GA, United States
Atlanta, GA, United States

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Researchers have been attempting to improve the yield of bleachable-grade kraft pulp for several decades. Wood is typically one of the major costs associated with kraft pulping. Therefore, it is typically assumed that improving pulp yield or conversely, reducing the amount of wood required to make a specific mass of pulp, is a cost-effective, lucrative endeavor. Although this may be true, it is important to understand the impact of increasing pulp yield on the interconnected processes within an integrated pulp and paper mill and to fully evaluate the cost implications on these processes. The current work employed several sets of laboratory pulping conditions and a WinGEMS model of a pulp mill, fully integrated with chemical recovery, power, and recausticization, and pulp drying islands to determine where the largest cost impact associated with improved pulp yield may be experienced. Application: This work can give new engineers better understanding of interactions between different operational departments within a mill. It may also be used to develop an improved analysis of the true economic impact associated with enhancing pulp yield.

Santos R.B.,North Carolina State University | Jameel H.,North Carolina State University | Chang H.-M.,North Carolina State University | Hart P.W.,MWV Corporation
Industrial and Engineering Chemistry Research | Year: 2012

Most of the studies on hardwood carbohydrate degradation focus upon the understanding of carbohydrate behavior of a single wood species. These studies tend to determine the activation energies associated with the three different cooking phases and for the different reactions that participate in carbohydrate degradation. In the current study, a variety of hardwood species were comprehensively characterized and the kinetics of carbohydrate degradation was studied. The kinetics of glucan, xylan, and total carbohydrate dissolution during the bulk phase of the kraft pulping process were investigated. A wide range of carbohydrate dissolution rates was obtained and correlated to chemical features and delignification rates for nine different hardwood species. It was determined that carbohydrate dissolution was dependent upon the rate of delignification. Species with high carbohydrate dissolution also presented high lignin removal rates. Our results indicate that the presence of lignin carbohydrate complexes positively influences pulping process selectivity during the bulk reaction phase. © 2012 American Chemical Society.

Fu J.,MWV Corporation | Hart P.W.,MWV Corporation
Tappi Journal | Year: 2016

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.

Hart P.W.,Meadwestvaco Corporation | Nutter D.E.,MWV Corporation
Tappi Journal | Year: 2012

During the last several years, the increasing cost and decreasing availability of mixed southern hardwoods have resulted in financial and production difficulties for southern U.S. mills that use a significant percentage of hardwood kraft pulp. Traditionally, in the United States, hardwoods are not plantation grown because of the growth time required to produce a quality tree suitable for pulping. One potential method of mitigating the cost and supply issues associated with the use of native hardwoods is to grow eucalyptus in plantations for the sole purpose of producing hardwood pulp. However, most of the eucalyptus species used in pulping elsewhere in the world are not capable of surviving in the southern U.S. climate. This study examines the potential of seven different coldtolerant eucalyptus species to be used as replacements for, or supplements to, mixed southern hardwoods. The laboratory pulping and bleaching aspects of these seven species are discussed, along with pertinent mill operational data. Selected mill trial data also are reviewed.

Hart P.W.,MWV Corporation
Tappi Journal | Year: 2012

Several mills in North America have been successful in using xylanase enzymes expressed from Trichoderma reesei (a fungus) as part of their bleaching sequence for many years. These mills process hardwood and softwood species, with and without oxygen delignification. These mills also use three-, four-, and five-stage bleaching sequences. North American mills tend to report increased pulp brightness ceilings and decreased bleaching costs as benefits associated with the application of enzymes in the bleaching process. Laboratory testing suggests that eucalyptus pulp is highly susceptible to fungal- and bacterial-derived enzyme bleaching and should result in significant cost savings in South American mills. At least four different mills in South America have attempted to perform enzyme bleaching trials using bacterial-derived enzymes. Each of these mill trials resulted in significantly increased operating costs and/or unsustainable operating conditions. More recently, one of these South American mills performed a short trial using a commercially available, fungal-derived enzyme. This trial was technically successful. This report attempts to determine why the South American mill experiences with bacterial-derived enzymes have been poor, while North American mills and the one South American mill trial have had good results with fungal- derived enzymes. Operating conditions and trial goals for the North and South American mills also were examined. Application: By better understanding the differences between bacterial- and fungal-produced enzymes, mills should be able to choose commercial applications that minimize negative performance aspects associated with enzyme bleaching applications.

Hart P.W.,MWV Corporation | Santos R.B.,MWV Corporation
Tappi Journal | Year: 2015

Eucalyptus plantations have been used as a source of short fiber for papermaking for more than 40 years. The development in genetic improvement and clonal programs has produced improved density plantations that have resulted in fast growing, increased fiber volume eucalypts becoming the most widely used source of short fibers in the world. High productivity and short rotation times, along with the uniformity and improved wood quality of clonal plantations have attracted private industry investment in eucalypt plantations. Currently, only a handful of species or hybrids are used in plantation efforts. Many more species are being evaluated to either enhance fiber properties or expand the range of eucalypt plantations. Eucalyptus plantations are frequently planted on nonforested land and may be used, in part, as a means of conserving native forests while allowing the production of high quality fiber for economic uses. Finally, eucalypt plantations can provide significant carbon sinks, which may be used to help offset the carbon released from burning fossil fuels. The development and expansion of eucalypt plantations represents a substantial revolution in pulp and paper manufacturing. © 2015, TAPPI Press. All rights reserved.

Hart P.W.,MWV Corporation
Tappi Journal | Year: 2014

Chemical pulping consists of a collection of delignification reactions designed to remove amorphous lignin from the fiber matrix while preserving carbohydrates in a fibrous form. Commercially available cooking processes are relatively nonselective with reagents attaching both lignin and carbohydrates. Generally, the carbohydrates react more slowly than the lignin, so some carbohydrate selectivity does exist for modern pulping processes. However, extended reaction times or excessive reaction temperatures will substantially reduce pulp yield. To date, only a few methods of converting high-kappa pulp into enhanced fiber yield have been demonstrated.

Sabourin M.J.,Andritz Group | Hart P.W.,MWV Corporation
Industrial and Engineering Chemistry Research | Year: 2010

Two different enzyme applications were applied to black spruce thermomechanical pulping (TMP) in an attempt to selectively enhance the physical properties of the resulting pulp. Past studies have revealed some application difficulties between pulp and enzymes. A new method of enzyme application including fiberizing the wood chips and cooling the fiberized material prior to enzyme application was employed to maximize the fiber surface area available for enzyme reaction and to obtain optimal enzyme reaction temperatures. Fiberized chips are chips that have been destructured in a converging screw chip press followed by low energy refining to produce extremely coarse fiber pulp. TMP pulps obtained from a control sample of whole wood chips, fiberized wood treated with water, and fiberized wood with two different enzyme applications were evaluated for specific refining energy and various physical properties. Scanning electron microscopy (SEM) in conjunction with image analysis techniques was used to determine fiber wall thickness, degree of fiber fibrillation, and percent surface disruption for selected trial pulps. One monocomponent pectinase enzyme evaluated in this work was found to significantly improve various physical properties and increase the specific surface area of the resulting pulp. The multicomponent more aggressive pectinase enzyme evaluated was determined to be less effective at enhancing physical properties than the less aggressive monocomponent enzyme. The new fiberizing application method employed prior to enzyme application was found to reduce the specific refining energy requirements by 7%. When evaluated at a constant freeness, the enzyme treatment in conjunction with the new application method was found to reduce specific refining energy by about 9%. The enzyme application had only minimal impact on energy requirements. The enzyme application did significantly enhance the tensile and tear index of the resulting pulp. Dramatic increases in the amount of fibrillation and fiber surface disruption were also found to result from specific enzyme action upon the fiber. The resulting fiber wall thickness was reduced as a result of the enzyme action as well. Results from this work reveal that selective enzyme application is an effective method for enhancing specific physical properties of TMP pulps. © 2010 American Chemical Society.

This work evaluates the findings of various research efforts and describes the development, use, and benefits of applying techno-economic models of different types to various production and bleach plant scenarios. During the late 1980s and early 1990s, researchers determined that bleach plants were releasing potentially significant quantities of chlorinated organics into receiving waters. This led to extensive research to develop bleaching chemicals to eliminate chlorine and hypochlorite from the bleaching sequence. Over time, 100% chlorine dioxide substitution for chlorine became the industry standard (today's elemental chlorine free [ECF] bleaching), and research efforts shifted toward chemical optimization of the ECF bleaching sequence. Several delignification stage and brightening stage models were developed and refined for use in bleach plant simulations to optimize chemical performance. Advances in computing power and the availability of packaged spreadsheet and simulation programs likewise led to the development of detailed material and energy balance models of the bleach plants. These simulations are used to minimize bleaching and pulp production costs, and to assist engineers in the development of justifications for capital expenditures. These models have been used to predict operating conditions that could lead to or reduce scale formation. They have also been extensively used to predict environmental performance of both new and modified bleach plants.

Samistraro G.,MWV Rigesa | Hart P.W.,MWV Corporation
Tappi Journal | Year: 2012

Variability in wood properties has a major impact on pulp quality and the cost associated with pulp production. Frequently, accounting data for green tons of wood across the mill scales and the tons of pulp produced suggest that the pulp mill has affected the pulp yield because the tons of purchased wood divided by the tons of pulp produced changes. The current work examines the impact of the time - from when a tree is harvested in the forest to the time it is brought across the scales at the mill - on accounting yield and operating cost. Percentage weight loss (assumed to be changes in moisture content) were determined for Pinus taeda, Eucalyptus dunni, and Eucalyptus grandis over a 12-week period in the winter and summer seasons. Wood samples were obtained immediately after being harvested. The percentage weight loss within the first 5 days of storage varied from 2% to 13%, depending upon species and season, and reached 36% after 11 weeks of storage. For a 1000 tons/day mill with a 55% pulping yield on o.d. fiber, the difference between using fresh-cut wood verses cut trees that have been stored for 11 weeks is 1130 green tons. Assuming the mill pays $45/green ton, the change in green log usage between fresh-cut and 11-week-old logs can cost the mill US$50,850 per day.

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