Time filter

Source Type

Atlanta, GA, United States

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.

Hart P.W.,MWV Corporation
2012 TAPPI PEERS Conference: Building a Sustainable Future | Year: 2012

Research efforts have attempted to improve the yield of bleachable grade kraft pulp for several decades. As wood is typically one of the major costs associated with kraft pulping, it is typically assumed that efforts to improve pulp yield or conversely, reduce 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 of improved pulp yield upon these processes. The current work employs 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 impacts associated with improved pulp yield may be experienced.

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
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.

Discover hidden collaborations