Research Articles

In order to improve the acid-resistant property of papermaking grade precipitated calcium carbonate filler and to obtain modified filler in powder form, sodium silicate/zinc chloride based modifiers were used in filler modification, and the use of modified filler in papermaking of deinked pulp derived from recycled newspaper was also preliminarily investigated. Under the preliminarily optimized experimental conditions, when sodium silicate, zinc chloride, sodium hexametaphosphate, and phosphoric acid with dosages of 10 wt%, 3 wt%, 1 wt% and 0.2 wt%, respectively, were used as modifiers, and when the temperature, aging time, and PCC concentration during the filler modification process was 70 oC, 7 h and 9.1 wt%, respectively, the acid-resistant property of filler was significantly improved after modification, as evaluated using alum consumption and pH methods. The use of modified precipitated calcium carbonate filler prepared under the optimized conditions provided considerably more brightness and light scattering improvement in comparison to unmodified filler, and filler modification was found to have only negligible influence on tensile and burst strength of the paper, air permeability of the paper, and retention performance of the filler. Surface analysis of the modified filler using XPS and SEM confirmed the occurring of surface encapsulation and modification of precipitated calcium carbonate filler when the relevant modifiers were used in filler modification. The encapsulating effect of modifiers on filler was thought to be favorable to improvement in acid-resistant property, and optical properties of the filled paper.

The objective of this study was to develop a supported tri-metallic catalyst (nano-Ni-La-Fe/γ-Al2O3) for tar removal in biomass steam gasification, to significantly enhance the quality of the produced gas. For this purpose, the supported tri-metallic catalysts were prepared by a deposition-precipitation (DP) method. Different analytical approaches were used to characterize the synthesized catalysts. The results showed that the prepared tri-metallic catalysts had an egg-shell structure with a specific surface area of 214.7 m2/g. The activity of the catalysts for gas production and tar removal in the process of biomass gasification was also investigated using a bench-scale combined fixed bed reactor. The experiments indicated that the tar yield after adding catalyst was reduced significantly and the efficiency of tar removal reached 99% for the biomass steam gasification at 800oC, while the gas yield after adding catalysts increased markedly and less coke was found over the catalyst. Meanwhile, the compositions of gas products before and after adding catalyst in the process also changed significantly; in particular, the content of hydrogen in catalytic steam gasification was improved by over 10 vol%. Therefore, using the prepared tri-metallic catalyst in biomass gasification can significantly improve the quality of the produced gas and efficiently eliminate the tar generation, preventing coke deposition on the catalyst surfaces, thus demonstrating a long lifetime of the catalyst.

Wettability of the fire retardant treated (FRT) laminated veneer lumber (LVL) manufactured from wood veneers dried at different temperatures was investigated. Commercially manufactured veneer of beech wood (Fagus orientalis L.) was treated with borax-boric acid (BX/BA, 1:1 by weight), monoammonium phosphate (MAP), and diammonium phosphate (DAP) using a full-cell pressure process. The veneers were then dried at different temperatures (120, 140, 160, and 180°C), and experimental LVLs were made from these veneer sheets. The wettability of LVL was characterized by contact angle analysis. The lowest contact angle was obtained from LVL made from BX/BA-treated veneers, while the highest value was found for the control LVL. The CA values of these samples at each re-drying level were lower than LVLs made from untreated veneers. Re-drying of the treated veneers decreased the CA values of the LVL, while it was found higher for the LVL made from untreated veneer.

The aim of this study was to evaluate the effect of heat treatment on the shear strength of tali (Erythrophleum ivorense) and iroko (Chlorophora excelsa) woods, bonded with some structural adhesives. Shear strength of untreated and heat-treated woods bonded with phenol-formaldehyde (PF), melamine-urea-formaldehyde (MUF), melamine-formaldehyde (MF), and polyurethane (PUR) adhesives was studied. An industrial heat treatment method (ThermoWood) was used. The timbers were thermally modified for 2 hours at 180 ºC. Laminated samples having two sample sets were prepared from untreated and heat-treated wood for the shear strength test. The results of the tests showed that the heat treatment affected shear strength of laminated wood negatively. Although there was a considerable difference in adhesive bond shear strength between untreated and treated wood, both wood species bonded with the adhesives fulfilled the required value for shear strength of the adhesive bonds. PF, MUF, MF, and PUR adhesives performed in a rather similar way for both wood species.

Pulp and paper mills are large energy consumers which can often achieve economic savings by implementing energy-saving measures. The process unit with the greatest energy demand in a mill is usually the evaporation plant. If excess heat can be made available in the mill, and the heat can be used in the evaporation plant, significant energy-savings can be achieved. In this paper, this kind of energy-efficient evaporation is called process-integrated (PI) evaporation, and the paper investigates the techno-economic consequences of PI evaporation. Theoretical plants with 6–8 evaporation effects are simulated using an in-house simulation tool called OptiVap. Conventional plants are used as reference, and evaporation plants with either lower surface condenser temperature or extraction of lignin are included. The results show that the additional profit of PI evaporation plants is 0.3–1.5 €/ADt in comparison with conventional plants. By lowering the temperature of the surface condenser, the profit is raised by 0.6–0.9 €/ADt for both conventional and PI plants. With lignin extraction, the PI plants are 0.7–1.7 €/ADt more profitable than the conventional ones.

Bleached unrefined and refined sawdust kraft pulps were added to bleached Norway spruce thermomechanical (TMP) and pressurised groundwood (PWG) pulps in different proportions. Handsheets were prepared and tested for physical properties. In addition, economic calculations were done to estimate the production costs of different bleached pulps in Finland. It was found that the addition of unrefined and refined sawdust kraft pulp improved drainability of the mechanical pulps. Tear strength of PGW furnishes was increased when either unrefined or refined sawdust pulp was added. Tear strength of TMP furnishes was not influenced when different sawdust kraft pulps were added. Up to 30 % of unrefined sawdust kraft pulp could be added and no significant negative effect was observed in TMP and PGW furnishes. On the other hand, when refined sawdust kraft pulp was added into the mechanical pulp furnishes, a clear improvement in the tensile strength was observed. According to the economic calculation the production cost of bleached sawdust kraft pulp is almost as low as the production cost of bleached mechanical pulp. We suggest that economically viable sawdust kraft pulp can be used as a substituent for expensive long fibre reinforcement kraft pulp in the production of mechanical pulp based papers.

A study was conducted to investigate the hydrolysis of cellulose-enriched corncob residue, a cellulosic waste from the xylo-oligosaccharides industry, by two processes. The corncob residue was hydrolyzed by cellulases via direct hydrolysis and two-step hydrolysis. Cellulases were produced by Trichoderma reesei RutC-30 with kraft pulp as the substrate. When the cellulase dosage was above 8 FPU•g-1 of corncob residue and the corncob residue concentration was 3%, over 90% hydrolysis yield and 49.99% glucose yield were obtained at 48 h. To enhance the hydrolysis yield of corncob residue, a new process coupling enzymatic hydrolysis, separation, and acid treatment was investigated. The corncob residue was first hydrolyzed using cellulase for 24 h. Then the remaining solids of corncob residue was separated from the liquid containing soluble oligosaccharides, and allowed to subsequently hydrolyze, using the adsorbed enzyme for 24 h. Using this method, the total hydrolysis yield was up to 97.60%, which represents an increase by 7.5% in comparison to the direct 48 h enzymatic hydrolysis. When the hydrolysates of the two-step enzymatic process were subjected to the concentrated acid hydrolysis at 110 ºC for 2 h, the glucose yield could be increased from 43% to 90%.

Reflectance UV-Vis spectroscopy and UV resonance Raman (UVRR) spectroscopy are both nondestructive techniques that are applicable to study trace concentrations of lignin in-situ. In this study, unbleached and bleached softwood kraft pulps were analyzed by reflectance UV-Vis (k/s) and UVRR spectroscopy to follow lignin and hexenuronic acid (HexA) contents and structural changes in residual lignin. The height of the lignin band in the UV-Vis spectra (280 nm) correlated well with the lignin band in the UVRR spectra (1605 cm-1) for semi- or fully-bleached pulps. However, the correlation was much weaker for unbleached pulps. Also the results for hexenuronic acid content by UV-Vis (240 nm) and UVRR (1658 cm-1) methods correlated well for most of the pulps, but for unbleached or peroxide-bleached samples the interference from other structures affecting these bands was obvious.

Some scientific contributions have used near infrared (NIR) spectroscopy as a rapid and reliable tool for characterizing engineered wood products. However, to our knowledge, there are no published papers that used this technique in order to evaluate wood-cement panels. The main objective of this paper was to evaluate the ability of NIR spectroscopy to estimate physical and mechanical properties in wood-cement panels. The wood-cement panels were produced using Eucalyptus grandis x E. urophylla, Pinus taeda, and Toona ciliata woods with Portland cement under different manufacturing conditions. Wood-cement panels were characterized by traditional methods, and Partial Least Squares regressions were used to build calibrations. Our cross-validated models for MOR, IB, and TS24h of the panels yielded good coefficients of determination (0.80, 0.82, and 0.91, respectively). Based on the significant absorption bands and regression coefficients of the PLS models, our results indicate that cellulose and aromatic groups in lignin are components that play an important role in the calibrations.

In-situ precipitation of calcium carbonate in bagasse fibers resulted in a very significant increase in specific scattering coefficient and consequently large improvements in opacity and brightness of the handsheets made from such pulp. At the same level of filler loading, the scattering coefficient of in-situ precipitated pulp was much greater than for directly loaded pulp. In-situ precipitation of calcium carbonate caused a drop in strength properties of bagasse pulp, but such loss could be recovered to a large extent by blending with other pulps. The effect of in-situ precipitation of calcium carbonate on pulp fibers was quite different for bagasse pulp from hardwood pulp. In-situ precipitation of calcium carbonate on hardwood fibers showed neither much improvement in optical properties nor much reduction in strength properties.