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Graduate Students Offer Hopes for the Next Generation


March 1, 2006
By Pulp & Paper Canada

Dr. Yonghao Ni congratulated the winner.

Stuart Heath of UBC opened the session, presenting a paper that combined medial tools with pulp and paper applications. Stuart used Positron Emission Tomography (PET) to dynamically visualize fibre su…

Stuart Heath of UBC opened the session, presenting a paper that combined medial tools with pulp and paper applications. Stuart used Positron Emission Tomography (PET) to dynamically visualize fibre suspension, putting detectors on either side of the event. He gained insight on how shear, created by the high turbulence of headboxing, affects the substance of the event. “PET is a non-invasive imaging method which can quantitatively measure the distribution [of upstream and downstream changes] in the expanding jet’s fibre concentration.”

Fang Huang of UQTR followed with a presentation on the effect of primary stage refining temperatures on fibre and paper properties. Huang examined the effects of two refining temperatures on the properties of Jack Pine TMP fibres, speculating that higher temperatures improve their collapsibility. Indeed, he proved that raising refining temperatures from 120 C to 160 C yielded greater sheet density without compromising tear strength. Comparatively, refining at 160 C also required 12% to 17% less energy for a given freeness, but produced a significant loss in pulp brightness.

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“Refining is probably one of the most important processes in pulp and paper mills because it can modify key factors such as strength,” started UBC’s Jens Heymer, the third presenter of the morning. “There is no device to quantify the refining heterogeneity,” he explained. Heymer shortened fibres, and analyzed fibre length distribution. He found an increase in short fibre length after the refining process, and expressed the comminution model with matrices. “We have to admit that the information on the breakage function is not yet explored,” said Heymer. “All we can say is that the fibres don’t seem to break at the beginning and at the end of fibres.” Heymer used a heterogeneity index and found that generally, a higher index meant a higher heterogeneity. This result was the first step in his objective to develop a test to determine heterogeneity using fibre lengths.

University of Toronto’s Daniel Staturnino discussed his prediction of solubility of recovery boiler precipitator ash. He explained the composition of precipitation ash, which is enriched in chlorine and potassium, creating fouling and corrosion problems for kraft pulp mills. By studying the solubility of the recovered ash in a water mix, Staturnino built a data bank to enable the effective removal of chlorine and potassium, and recover as much valuable minerals as possible.

Satya Mokamati of UBC used aperture geometry to determine the detailed flow behaviour through a periodic array of normally spaced wires in cross flow. “Pulp screening is an essential unit operation for pulp and paper producers because screens remove contaminants that reduce the strength and appearance of papers and also separates fibres by length for use in specialty products.” Mokamati used adaptive correlation to calculate the displacement of particles in the flow field, and found that lower contour heights increase efficiency up to an optimal height.

McMaster’s Chuanwei Miao examined the effect of Polyvinylamine Microgels on paper strength and the roughness of fibre surface. Miao found that microgels can fill the void at fibre bonding areas to achieve higher paper strength, and that the smaller the gel, the greater the adhesion. Using TAPPI testing methods, he concluded that microgels were superior to linear PVAm and that the crosslink density had a significant effect.

Shivamurthy Modgi, tested the aggregation of precipitated calcium carbonate (PCC) with starch in distilled and deionized water (DDW) and processed water (PW) in order to reduce the costs for mechanical pulp mills. Fibre fines retained in pulp, or anionic trash, neutralizes the retention acids like starch, which deters retention. In both DDW and PW, tapioca starch performed better than two potato starches. “Potato starch pretty much acts like an anionic trash collector,” said the UBC student. “I used the degrees used in the industry so we didn’t go above that [starch] dosage because they don’t.”

Dominique Simard of UQTR presented the effects of foam on paper quality and the development of an environment-friendly water-based defoamer. “My objective was to find a suitable blend of surfactants to make the water-based defoamer stable and efficient for three months in the factory.” Simard explained her method for producing a defoamer that is stable and has a good viscosity. “The defoamer’s efficiency is at least as good as the commercial products.”

McGill University’s Marcius H. de Oliveira concluded the morning session with a presentation on the adhesion of wet fibres focusing on wet breaks between the presses and the drying sector. “Most breaks in production occur there, so this is important for paper mills,” said de Oliveira. He used the Campbell effect to measure wet strength and shear strength, showing that the fibres cannot keep together when there is no water. “The main reason to use blotters is to see what keeps the fibres together when there is no free water,” explained de Oliveira. “This indicates that there might be some sort of friction between the two blotters that increase shear tension.”

All the morning speakers were given tips and constructive criticism on their methods, research, and presentations, as is the custom during the Graduate Students Seminar. Not only were they presenting their results, they were also being judged for the three Henry Bolker prizes, awarded annually in recognition of students who achieve excellence in communication and research in the pulp and paper industry.

Henry Bolker Prize Winners

Lucy Le also won 1st prize for the Henry Bolker for Best Seminar for her work, A Platform of Immobilization of Proteins on TiO2 Nanoparticles.

In second place was Chuanwei Miao, for Effect of Polyvinylamine Microgels on Paper Strength -Handsheet Testing.

In third place was Yi Zhang for, Examining Deflocculation Under Short-Term Oxygen Disturbance in the Activated Sludge Process.


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