Research Articles

This study sought to determine the suitability of fractionation and consequence-selective processing (separation of long fiber and short fiber, beating long fiber, and remixing with short fiber to target freeness) as a new approach to use of kenaf whole stem pulp for paper and paper-board production. A laboratory Bauer-McNett Classifier with screen 18 mesh was used to separate short fibers and long fibers of the unbeaten kenaf whole stem soda-anthraquinone high kappa and low kappa pulps. For comparison, the initial unbeaten pulps were beaten in the PFI mill to the same freeness (300 mL CSF). Results of our patented method showed that the fractionation process was able to provide a good opportunity to beat the long fiber portion at higher PFI revolutions and to achieve better fibrillation, significantly improving all paper properties of kenaf pulps except for tear index and producing sheets with better drainage and strength properties compared to conventionally beaten pulps, especially in the case of kenaf high kappa pulp.

Removal of detrimental contaminants from paper machine circulation waters is known to benefit process runnability and paper quality. The applicability of selective flotation to remove substances of a hydrophobic nature from paper machine circulation waters was investigated in laboratory-scale experiments. The separation efficiency of ink, stickies, and wood extractives was studied by using a flotation scheme in which the froth was generated by the white water’s inherent surface active components without any chemical addition. The removal efficiency of detrimental contaminants was considered in relation to total losses of solid materials. The results showed that while not all white waters were able to produce stabile froth, those that generated froth also exhibited substantial separation of contaminants in the froth. With a moderate removal of 10% of total solids from white waters, removal of 45% of stickies, 27% of ink, and 20 to 50% of wood extractives was observed. Higher removal of contaminants resulted in solids losses at levels that are not economically feasible in paper production. The results showed that selective white water flotation can have beneficial results for papermaking processes.

By removing the primary fines from an oxygen-delignified mill birch pulp, a fiber fraction was obtained having low metals content and no extractives. After DEDeD bleaching the fiber fraction had somewhat higher brightness and better brightness stability than the birch pulp containing the primary fines. The fines fraction was enriched with lignin, extractives, xylan, and metals. Bleaching the fines fraction in a QQP sequence did not affect the extractives, whereas a ZeQP sequence clearly reduced the extractives content. In a biorefinery concept, the fines fraction could be utilized as a source of xylan, fatty acids, sterols, and betulinol. Another possibility is to use the fines fraction unbleached or separately bleached as a bonding material in various fiber furnishes.

A pyrolysis tube furnace system was designed to assess the impact of different components on pyrolysis characteristics under nitrogen atmosphere, and pyrolysis temperature (400 to 900oC) as important factors acting on the samples during pyrolysis. The obtained pyrolysate was classified into three groups, i.e. the condensed liquid product (bio-oil), solid product (bio-char), and light gas. Gas chromatography (GC) was used to analyze ingredients of the light gas released during pyrolysis, and a gas chromatography/mass spectrometer (GC/MS) was used to analyze bio-oil. The results revealed that the volatiles from rice straw pyrolysis exceeded that from lignin at temperatures below 700oC as a result of the higher char generation from lignin pyrolysis. With an increase of pyrolysis temperature, the yield of char decreased and light gas persistently increased, and the yield of bio-tar was maximized at 500oC. In the gas product, H2, CO, CO2 and some light hydrocarbons (CH4, C2H4 and C2H6) could be found, and H2 and CO were abundant. Compounds of bio-oil derived from lignin were simple and consisted of aromatic hydrocarbons, chain hydrocarbon, monoaromatics, and a minor amount of ketones. Phenolic compounds, which comprised 50 to 60%, can be converted easily to obtain high-value chemicals and high quality biofuels.

Mechanical properties of polyethylene (PE) composites were evaluated as a function of the addition of bacterial cellulose (BC). It was found that BC could improve the mechanical properties of the composites with or without the combination of traditional wood fiber. The improvements were affected by post-treatment. It was confirmed that BC had a significant influence on impact strength. The pellicle form of BC was able to achieve superior impact strength compared to the fluffy form of BC, but had similar effects on the tensile strength in comparison to the composites with fluffy BC.

The peroxymonocarbonate mono-anion (HCO4─) is generated when the bicarbonate anion is added to a H2O2 solution. The mono-anion is believed to have a pKa value of ca. 10 and as such would start dissociating to the di-anion (CO42─) at pH ca. 8. The mono-anion should demonstrate electrophilic properties, while the di-anion should be a nucleophile. In an alkaline, non-sulfur pulping process such as soda/AQ, Na2CO3 could be obtained from the chemical recovery system and carbonated with CO2 from a flue gas stream to produce NaHCO3. In such a case only H2O2 would need to be purchased to generate the peroxymonocarbonate (PMC) anions. Bicarbonate anions could also be produced from the carbonation of solutions containing NaOH, Mg(OH)2 or mined Na2CO3. One or both of the PMC anions was found to be effective in oxidizing two lignin model compounds as well as lowering the lignin content of kraft and soda/AQ hardwood pulps. The PMC anions were generated in-situ by NaHCO3 or Na2CO3 + CO2 addition to dilute H2O2 solutions.

The peroxymonocarbonate mono-anion (HCO4─) is generated in solutions containing bicarbonate anions (HCO3─) and hydrogen peroxide (H2O2). The mono-anion is believed to have a pKa value of ca. 10 and as such would start dissociating to the di-anion (CO42─) at pH ca. 8. The mono-anion should demonstrate electrophilic properties, while the di-anion should be a nucleophile. Results that appear to be due to electrophilic reactions of HCO4─ were presented in Part 1 of this series for lignin model compounds (LMCs) and chemical pulps. Some evidence was also observed for nucleophilic reactions with LMCs in the pH range of 8.8 to 9.5. Results are now being presented for mechanical pulp brightening, where nucleophilic reactions were observed. Hydrogen peroxide decomposition in the HCO3─ solutions was significant on some occasions, and Fe catalyzed decomposition was the most significant contributor in both pulp slurries and pulp-free solutions.

The aim of this study was to investigate the effect of esterification via acetic or propionic anhydride on the surface roughness of eastern cottonwood. Eastern cottonwood (Populous deltoides) was esterified by using acetic or propionic anhydride without using any solvent or catalyst under different conditions. Two different weight percentage gains (WPGs) were obtained for each of the modifying chemicals. Three main surface roughness parameters, namely average roughness (Ra), mean peak to valley height (Rz) and maximum roughess (Rmax) were measured by a stylus method before and after esterification. The surface roughness was significantly increased due to the esterifications. The surface roughness of wood increased with increasing WPG.