TAPPI JOURNAL summaries.

Following are summaries of June 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).

RECYCLING

TONER PARTICLE COMMINUTION IN OFFICE PAPER DISPERSION

By Frantisek Ruzinsky and Chad P.J. Bennington

APPLICATION: This study may assist recycling mills 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. Disperser operation was characterized using the specific energy and specific edge load (SEL) while dispersion efficiency was measured using the ink particle size distribution and the equivalent black area (EBA) of sheets made from treated pulp. Particle comminution was most efficient when carried out at higher consistencies. The magnitude of the applied force affected particle comminution significantly. Comminution with the pyramidal plates was less efficient due to the range of gap widths between the pyramidal elements.

PAPERMAKING

INFLUENCE OF 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 the influence of papermaking system closure on paper properties, we used reverse osmosis technology to prepare highly contaminated white water. We used that water to form handsheets from linerboard, newsprint, and fine paper stocks. Results showed that the quality of process water affected the strength properties of these paper grades. We also examined the influence of colloidal and dissolved materials on linerboard properties. Results showed that the amount of colloidal substances in the process water--rather than the amount of dissolved substances--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 used resistivity probes for the dynamic detection of liquid-vapor phase change inside wet paper webs undergoing impulse pressing. The probes were made from thin copper wires insulated with a high-temperature polymeric material. 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. All suggested models presented errors comparable to the errors found in the literature. They can be applied indistinctly to simulate daily processes and can be used as a performance indicator of the process.

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.

Papermakers are continuously searching for better ways to overcome the problems related to accumulation of pitch and polygalacturonic acids (pectins) in process waters. Dissolved air flotation (DAF) is a technique that could be used as an internal cleaning stage to remove these substances. This study investigated removal of pitch and galacturonic acids from peroxide-bleached, fiber-free thermomechanical pulp (TMP) water by DAF. Study 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.