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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]

Milled wood lignins from alkaline pretreated wood with very low sugar content and a wide range of syringyl-to-guaiacyl (S/G) ratio between 1.2 and 3.0 were isolated from 12 industrially valuable hardwood (HW) species. The lignin preparations were investigated by means of a comprehensive 13C nuclear magnetic resonance (NMR) methodology to address the possibilities and limitations of this approach for HW native lignins and to estimate the structural variations within HW lignins. Good correlations were found for different independent methods for the quantification of major lignin moieties. The results were reliable at the C6 level and not only for relative comparison. The correlation was good between methoxyl group determinations by wet chemistry and those by 13C NMR spectroscopy. The limitations of the 13C NMR method were also pointed out. The differences in the S/G ratios can be large, but other structural deviations are less significant. Strong correlations between the S/G ratios and the amounts of other structural peculiarities could not be found by the 13C NMR approach. However, with increasing S/G ratios, the β-O-4 content showed increasing tendencies and the degree of condensation showed decreasing tendencies. [ABSTRACT FROM AUTHOR]

The kinetics of the bulk and residual delignification phases of Eucalyptus nitens, E. globulus, E. benthamii, acacia, maple, and loblolly pine were determined in an effort to improve the use of various hardwoods. Kinetic experiments were performed using a microwave digestion system for fast heating of the kraft liquor. Delignification rates were obtained for three different temperatures (150°C, 160°C, and 170°C) and correlated with the wood's syringyl-to-guaiacyl ratio. A linear correlation between the kraft delignification rate and the syringyl-toguaiacyl ratio was found to exist. [ABSTRACT FROM AUTHOR]

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. Application: By understanding the breeding and clonal developments that have occurred in the past and the results of those developments, the industry may be better equipped to rapidly advance the next stage of eucalypt progress. [ABSTRACT FROM AUTHOR]

The effect of wood chip acid leaching pretreatment on non-process elements removal and its impact on wood chemical components has been examined. Acid leaching treatments were carried out using two different acid pretreatment approaches: (1) acidified water and (2) filtrate from an acidic bleaching stage. Optimization experiments to identify the most suitable leaching conditions with regard to non-process elements removal and chemical oxygen demand generation were performed. The incorporation of an acid leaching stage significantly reduced the non-process elements content in the wood chips. Carbohydrate content and other wood constituents were not negatively affected by the applied pretreatment. Application: Mills can apply acid leaching pretreatment to the pulping process without degrading carbohydrates and with no major yield loss. [ABSTRACT FROM AUTHOR]

Brownstock washing is a complex, dynamic process in which dirty wash water or weak black liquor (dissolved organic and inorganic material obtained from the pulp cooking process) is separated from pulp fibers. The use of material balance techniques is of great importance to identify potential problems and determine how well the system is operating. The kraft pulping industry was the first known to combine pulp washing with the recovery of materials used and produced in the wood cooking process. The motivation behind materials recovery is economic, and more recently, environmentally driven. The chemicals used in the kraft process are expensive as compared to those used in the sulfite process. For the kraft process to be economically viable, it is imperative that a very high percentage of the cooking chemicals be recovered. To reach such high efficiency, a variety of washing systems and monitoring parameters have been developed. Antifoam additives and processing aids have also played an important role in increasing washing effectiveness. Antifoam materials help attain washing effectiveness by preventing entrapped air from forming in the system, which allows for an easier, unimpeded flow of filtrate through the screens and washers. [ABSTRACT FROM AUTHOR]

Most studies aimed at determining rates of hardwood delignification and carbohydrate degradation have focused on understanding the behavior of a single wood species. Such studies tend to determine either the delignification rate or the rate of carbohydrate degradation without examining the potential interactions resulting from related variables. The current study provides a comprehensive evaluation of lignin and carbohydrate degradation during kraft pulping of multiple hardwood species. The kraft delignification rates of Eucalyptus urograndis, E. nitens, E. globulus, sweet gum, maple, red oak, red alder, cottonwood, and acacia were obtained. The kinetics of glucan, xylan, and total carbohydrate dissolution during the bulk phase of the kraft pulping process for those species also were investigated. The wide ranges of delignification and carbohydrate degradation rates were correlated to wood chemical characteristics. It appears that the syringyl:guaiacyl lignin ratio and lignin-carbohydrate complexes are the main factors responsible for the differences in kraft pulping performance among the hardwoods studied. [ABSTRACT FROM AUTHOR]

Most studies aimed at determining rates of hardwood delignification and carbohydrate degradation have focused on understanding the behavior of a single wood species. Such studies tend to determine either the delignification rate or the rate of carbohydrate degradation without examining the potential interactions resulting from related variables. The current study provides a comprehensive evaluation on both lignin and carbohydrate degradation during kraft pulping of multiple hardwood species. The kraft delignification rates of E. urograndis, E. nitens, E. globulus, sweet gum, maple, red oak, red alder, cottonwood, and acacia were obtained. Furthermore, the kinetics of glucan, xylan, and total carbohydrate dissolution during the bulk phase of the kraft pulping process for the above species were also investigated. The wide ranges of delignification and carbohydrate degradation rates were correlated to wood chemical characteristics. It appears that the S/G ratio and lignin- carbohydrate-complexes (LCCs) are the main characteristics responsible for the differences in kraft pulping performance among the hardwoods studied. [ABSTRACT FROM AUTHOR]

Most of the studies on hardwood carbohydrate degradationfocusupon the understanding of carbohydrate behavior of a single wood species.These studies tend to determine the activation energies associatedwith the three different cooking phases and for the different reactionsthat participate in carbohydrate degradation. In the current study,a variety of hardwood species were comprehensively characterized andthe kinetics of carbohydrate degradation was studied. The kineticsof glucan, xylan, and total carbohydrate dissolution during the bulkphase of the kraft pulping process were investigated. A wide rangeof carbohydrate dissolution rates was obtained and correlated to chemicalfeatures and delignification rates for nine different hardwood species.It was determined that carbohydrate dissolution was dependent uponthe rate of delignification. Species with high carbohydrate dissolutionalso presented high lignin removal rates. Our results indicate thatthe presence of lignin carbohydrate complexes positively influencespulping process selectivity during the bulk reaction phase. [ABSTRACT FROM AUTHOR]

The article discusses the integration of the pulp and paper industry into the biofuels and biochemicals industry in the U.S.

The article discusses the highlights of the 2014 International Chemical Recovery Conference (ICRC) and the Pulping, Engineering, Environmental, Recycling and Sustainability (PEERS) Conference held in Tacoma, Washington. History of kraft chemical recovery, boiler design and corrosion mitigation are cited as topics at the 2014 ICRC. Particular focus is given to the 50th anniversary celebration of the Finnish Recovery Boiler Committee at the ICRC event. Five program tracks were featured at PEERS.