TAPPI Journal summaries.

Following are summaries of May 2006 peer reviewed papers from TAPPI JOURNAL, a monthly publication that includes full-text, peer reviewed research papers. TAPPI membership includes access to all TAPPI JOURNAL content online at www.tappi.org. In addition, print and electronic subscriptions are available. For more information about joining TAPPI or to subscribe to TAPPI JOURNAL, contact the TAPPI Member Connection Center: Phone: [phone] (USA); 1 800 446-9431 (Canada); or [phone] (International).

STICKIES

SIMULATION OF THE BEHAVIOR OF STICKIE-CONTAMINATED SHEETS IN A DRYER SECTION

By Gregory M. Fike, Tom Merchant, and Sujit Banerjee

APPLICATION: Certain conditions govern the transfer of stickies from a mat to a hot metal surface, but there are ways to minimize the transfer.

When stickies get stuck on the hot metal surface of the dryer, they make it harder for the sheet to separate cleanly from the dryer can. Stickies on the dryer surface tend to pick the sheet and increase maintenance costs. This study on the separation of stickie-filled sheets from a dryer was carried out with both dynamic and static drying simulators. Experiments with the dynamic drying simulator showed that the release of the sheet can be improved by increasing the incoming solids content of the sheet and the drying temperature.

RECYCLING

TONER PARTICLE COMMINUTION IN OFFICE PAPER DISPERSION

By Frantisek Ruzinsky and Chad P.J. Bennington

APPLICATION: This study may assist recycling mill in enhancing the efficiency of their deinking/disperser equipment.

Disc dispersers are used to detach and comminute recalcitrant ink in paper recycling operations. The dispersion efficiency of toner printed paper was studied using a laboratory 30-cm Sprout-Waldron refiner with barred and pyramidal plates. Particle comminution was most efficient when carried out at higher consistencies. Comminution with the pyramidal plates was less efficient due to the range of gap widths between the pyramidal elements.

PAPERMAKING

INFLUENCE OF THE PAPERMAKING SYSTEM CLOSURE ON PAPER PROPERTIES

By Hak Lae Lee, Chung Hyun Ham, and Sang Gil Lee

APPLICATION: This study may help mills evaluate and cope with some of the advantages and disadvantages of closing process water loops.

Papermaking system closure causes an inevitable increase of fines and organic and inorganic substances in the process water. To examine how system closure affects paper properties, we used reverse osmosis technology to prepare highly contaminated white water. We used that water to form hand-sheets from linerboard, newsprint, and fine paper stocks. Results showed that the quality of process water affected the strength properties of these paper grades, and that the amount of colloidal substances in the process water is critical for sheet strength.

DRYING

CHARACTERIZING LIQUID-VAPOR PHASE CHANGE PHENOMENA IN IMPULSE TECHNOLOGY WITH RESISTIVITY PROBES

By Andrew R. Martin and Marco F.C. Lucisano

APPLICATION: This study evaluated a method to detect changes in paper during impulse pressing as a means to gain further insights into the technology and advance its development.

This study (Part I of a two-part series) used resistivity probes for the dynamic detection of liquid-vapor phase change inside wet paper webs undergoing impulse pressing. Impulse pressing experiments were subsequently conducted with a platen press under realistic operating conditions. Results show that steam was detected inside the sheet only upon unloading of the hot nip for the layers closest to the heated surface.

PROCESS SIMULATION

DEVELOPMENT OF PREDICTIVE OXYGEN DELIGNIFICATION MODELS USING KINETIC EXPRESSIONS AND NEURAL NETWORKS

By Bibiana R. Rubini and Carlos I. Yamamoto

APPLICATION: The models evaluated in this study may help pulp mills pretest various process variables.

This work proposes mathematical models capable of predicting the outlet kappa number of the delignification reactor of the Klabin Celulose e Papel Mill--Unit Monte Alegre, in Telemaco Borba. Brazil. These models are a useful tool for cellulose mills when applied to process simulation, optimization, and control. This work proposes three kinetic models and identified nonlinear models for the delignification plant.

WATER TREATMENT

PURIFICATION OF PEROXIDE-BLEACHED TMP WATER BY DISSOLVED AIR FLOTATION 

By Ville Saarimaa, Anna Sundberg, Bjarne Holmbom, Angeles Blanco, Carlos Negro, and Elena Fuente

APPLICATION: This study provides valuable information for papermakers who might install a DAF cleaning stage in a TMP process and for optimizing the DAF functions.

Dissolved air flotation (DAF) is a technique that could be used as an internal cleaning stage to remove pitch and poly-galacturonic acids (pectins). This study investigated removal of pitch and galacturonic acids from peroxide-bleached, fiber-free TMP water by DAF. The results indicate that understanding the chemistry of aggregation and flotation is necessary for selection of flocculation chemicals, adjusting process conditions, and for obtaining an acceptable cleaning efficiency.