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Summaries of December 2005 peer-reviewed papers.

TAPPI JOURNAL is a monthly publication that includes full-text, peer reviewed research papers exploring every aspect of pulp and papermaking. Each issue presents technically sound, applications-based research; special insights from the authors; and more. TAPPI Membership includes access to all TAPPI JOURNAL content online at www.tappi.org. In addition, convenient print and electronic subscription options are available; TAPPI members receive substantial subscription discounts.

For more information about joining TAPPI, or to subscribe to TAPPI JOURNAL, contact the TAPPI Member Connection Center: Phone: 1 800 332-8686 (USA), 1 800 446-9431 (Canada), +1 770 446-1400, by email at memberconnection@tappi.org, or visit www.tappi.org.

MOISTURE

THE EFFECT OF PULP REFINING ON LATERAL AND TRANSVERSE MOISTURE DIFFUSION IN PAPER

APPLICATION: The information in this report may help mills predict the rate of moisture transport into rolls and sheets under varying humidities.

Moisture diffuses through the pore space and the fiber matrix in paper materials. The diffusivity through paper increases strongly with moisture content. We measured the moisture diffusivity of handsheets made of refined bleached kraft pulp at various relative humidity conditions. Steady state moisture fluxes were measured and diffusivities in the lateral (x-y) and in the transverse (z) directions were calculated. The lateral diffusivity was found to be higher than the transverse diffusivity for all the samples and the effective moisture diffusivities depended strongly on the moisture content. View this paper online at http://www.tappi.org/index.asp?pid=33688&ch=1

Ademilson Massoquete, Sergei A. Lavrykov, and Bandaru V. Ramara are with Empire State Paper Research Institute, Faculty of Paper Science and Engineering, State University of New York CESF, Syracuse, New York, USA Ankur Goel and Shri Ramaswamy are with the Department of Biobased Products. University of Minnesota, St. Paul, Minnesota, USA Email Ramarao at bvramara@esf.edu.

KRAFT PULPING

DETERMINING THE HEAT OF REACTION OF KRAFT PULPING

APPLICATION: Knowing the magnitude and generation rate of the exothermic heat is important for the proper control of digesters.

The extent of heat given off during kraft pulping needs to be defined more precisely for engineers to improve digester control programs and to size relief systems properly. Exothermic reactions in kraft pulping arise mostly from the neutralization of native wood acids and the neutralization of acids that form during the cook as carbohydrates and lignin are degraded.

The exothermic heat of reaction was measured for both softwood and hardwood cooks in a laboratory digester. Experiments were designed to measure the electrical energy required to carry out a kraft cook and the electrical energy required to "cook" an equivalent amount of water. We then determined the amount of heat evolved during kraft pulping by subtracting the energy required for the water from that required for the pulp.

WE found that the heat of reaction is both measurable and significant. Most of the exothermic heat is given off during the heat-up phase, with little effect in the time-at-temperature stage of a cook. The exothermic heat of reaction is evolved gradually and causes problems with pressure only if the digester is overly filled. The results can be used in modeling the heat balance for a batch digester, which in turn could lead to better designs for control systems. View this paper online at http://www.tappi.org/index.asp?pid=33689&ch=1

Charles E. Courchene, Thomas J. McDonough, Earl W. Malcolm, and Blair R. Carter are with the Institute of Paper Science and Technology, Georgia Institute of Technology, 500 10th Street, NW, Atlanta, GA 30332-0620. Peter W. Hart is with MeadWestvaco, 232 E. 8th Street, Chillicothe, OH 45601-3478. Email Courchene at charles.courchene@ipst.gatech.edu.

TJ PERSPECTIVE TESTING METHODS

NEW ISO TEST METHOD FOR HIGH-GLOSS PAPERS

APPLICATION: A brief presentation of this new method will be valuable for those within the paper industry who are trying to understand why there is more than one standard procedure for measuring gloss.

In November 2004, a new ISO standard was published for the determination of paper gloss at a specular angle of 20[degrees]. This method, which is essentially the same as the corresponding TAPPI method, is particularly suitable for high-gloss papers and boards. It is a complement to the two ISO Standards previously published, which are more suitable for matte and low-gloss papers and boards. The three methods have the same basic ISO number, but are published as separate parts.

There are important differences in gloss scale and application of existing methods for measuring gloss. A brief examination of these differences illustrates the need for several standards. This paper has been read and approved for publication by the members of ISO/TC6/WG3, Paper and Board-Optical test methods. View this paper online at http://www.tappi.org/index.asp?pid=33709&ch=1

J. Anthony Bristow, Bristow Consulting AB, was formerly convenor of ISO/TC6/WG3 (Optical properties of paper and board). Email Bristow at bristow@beta.telenordia.se.

PROCESS SIMULATION

STUDY OF THE MULTICYLINDER DRYING SECTION OF THE KLABIN-PR MP-7 PAPER MACHINE

APPLICATION: Neural networks may be useful to help control moisture content and increase dryer efficiency.

Multicylinder sections of paper dryers consume the most energy in an industrial plant. They are also responsible for the final characteristics of the paper produced. In this context, the modeling of the paper drying process is very important, and is normally done by phenomenological approaches. An interesting and promising alternative, due to the possibilities of its application, is through the identification of an operational standard behavior, obtained by the use of neural networks in the simulation of the final paper moisture content. This alternative was implemented in the drying section of the Klabin Parana Papeis S.A. (Klabin-PR) MP-7 paper machine. For this study, we collected operational data related directly and indirectly to the drying process, composing a database with 110 preselected variables. These data were analyzed with the help of Statistica Neural Network software, which, besides its use for training and choosing the more capable neural networks to model the chosen variable, allows the selection of the group of variables of larger influence in the studied process. The results obtained by the use of the neural network modeling were quite satisfactory, with an average error of less than 2% in the prediction of the final paper moisture content. View this paper online at http://www.tappi.org/index.asp?pid=33690&ch=1

Oswaldo Curty da Motta Lima and Nehemias Curvelo Pereira are professors in the Chemical Engineering Department (DEQ)--State University of Maringa (UEM), Colombo Avenue 5790, BI. D90, CEP 87020-900, Maringa-PR, Brazil, Flavio Deganutti is chemical engineer, M.Sc.--Klabin-PR. Email Motta Lima at oswaldo@deq.uem.br
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Title Annotation:TAPPI JOURNAL SUMMARIES
Publication:Solutions - for People, Processes and Paper
Date:Dec 1, 2005
Words:1106
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