Volume 15 Issue 3

Using foam as a carrier fluid in papermaking gives interesting new opportunities. Foam as a more viscous fluid than water is expected to behave differently in a dynamic process. This study presents results obtained under dynamic forming conditions in a semi-pilot scale research environment. Effects of process configurations and running conditions on increased forming speed, web properties, and difference between water-laid and foam-laid processes are shown. The studies were carried out using a water-laid former and the same environment modified for foam forming. In order to achieve increased forming speed, the open headbox was replaced with a closed headbox, and the former geometry was updated. The process foam was boosted with an additional foam pulper. The foam pulper was used as a machine chest for improving the dispersion of fibers into the foam. A much broader tensile strength ratio range (~3 to 8) was achieved with foam forming than with water-laid forming. Foam-laid paper had a broader pore size distribution and higher mean pore size. Formation and the formation spectra of foam-laid sheets were more uniform, leading to improvements in the properties of the fiber network.

To investigate the decay mechanisms of red oak (Quercus rubra) and hemor (Schima spp.) woods in the old architectural structure of Xichuan Guild Hall, chemical composition changes were determined and analyzed with X-ray photoelectron spectroscopy (XPS). The results showed that decaying resulted in a noticeable decrease of the O/C from 0.59 to 0.42 in the red oak wooden components. The increase of C1 contribution, decrease of C4 contribution, increase of O1 and O3 contributions, and decrease of O2 contribution indicated that the carbohydrates in red oak wooden components can be easily degraded by fungi compared with lignin. Moreover, decaying resulted in a slight decrease of the O/C from 0.49 to 0.47 in the hemor wooden components. The results of increase of C1 contribution, decrease of C3 and C4 contributions, increase of O1, and decrease of O2 and O3 contributions indicated that carbohydrate and lignin were all degraded by fungi.

Five-year-old moso bamboo was torrefied under nitrogen and different oxygen concentrations of 3% to 9% and torrefaction temperatures of 200 °C to 300 °C. Mass yields of 31.7% to 96.6%, energy yields of 30.8% to 98.9%, and higher heating values (HHVs) in the range 18.8 to 27.1 MJ/kg were obtained. The torrefied sample was characterized by Fourier transform infrared spectrometry (FTIR). Under the different torrefaction temperatures and oxygen concentrations, hemicellulose and cellulose were thermally decomposed, which led to significant changes in the chemical functional groups of the raw and torrefied bamboo. The pyrolysis experiments on raw and torrefied bamboo were conducted using the pyrolyzer coupled with a gas chromatography/mass spectrometer (Py-GC/MS). According to the Py-GC/MS analysis, the pyrolytic bio-oil were mainly composed of acids, furans, phenols, ketones, aldehydes, esters, alcohols, and hydrocarbons. Higher torrefaction temperature reduced the relative contents of acids, ketones, furans, and aldehydes. However, lower torrefaction temperatures and moderate oxygen concentrations were optimal for the production of phenols and hydrocarbons.

The elastic strain of wood reflects the nature (stretching or compression) and the magnitude of the drying stress at that time during the conventional drying process. The accurate prediction of strain is important to optimize the drying process and to improve drying speed and quality. In this work, the elastic strain was measured in real time, and moisture content was measured by periodic weighing during the drying process. Using these data, the GM (1,1) grey prediction model was used to predict moisture content in adjacent periods in the future. Based on the moisture content predicted by GM (1,1), a BP neural network was constructed to predict the development trend of elastic strain in the surface layer and core layer. The prediction results of the GM-BP combination model showed that the fitting error range of the prediction of the surface layer elastic strain was [-5×10-3~5×10-3], with a mean square error (MSE) of 2.31×10-7. The elastic strain of the core layer was [-2×10-3~2×10-3], and the MSE was 3.86×10-8. Thus, the GM-BP model achieved high accuracy for predicting the development trend of elastic strain. It can provide a new method and innovative thinking for the optimization and control of wood drying process.

This work aimed to study the potential of defatted rice bran (DRB) and defatted soybean meal (DSM) as carbon and nitrogen sources for Lactococcus lactis growth and nisin production. First, a maximum nisin yield of 3630 IU/mL was achieved using 40% DRB hydrolysates and 30% DSM hydrolysates, which was 1.13 times greater than that found in commercial media. Second, to simplify the operation and shorten the length of the entire process, the processes of combined hydrolysis of DRB-DSM followed by fermentation, and simultaneous hydrolysis and fermentation of DRB-DSM were developed. Neutral proteinase enhanced the saccharification of DRB by cellulase and α-amylase. Furthermore, the strategy of NADH oxidase expression and hemin addition was innovatively proposed to overcome the oxygen stress in a simultaneous hydrolysis and fermentation process, which could alleviate the lag period following inoculation of L. lactis and result in a 77.3% increase in nisin titer.

A Zr4+-doped SiO2/TiO2 composite film (Zr4+-doped STCF) was prepared on a wood surface via a sol-gel method to improve its photocatalytic activity and aging resistance. The physicochemical characteristics of the composite film were analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and low-temperature N2 sorption methods. The photocatalytic degradation of methyl orange and its aging resistance under ultraviolet light were tested. The results showed that the composite film had an anatase TiO2 crystal form, and the addition of Zr4+ to the composite film noticeably improved photocatalytic activity and aging resistance. The highest degradation percentage occurred at 0.5 wt% Zr4+ (59.2%) when the Zr4+ ion doping amount was 2.5 wt%, and the aging resistance of the composite film also peaked under these conditions. The wood surface coated with Zr4+-doped STCF exhibited strong aging resistance and photocatalytic activity, which protected the surface from discoloration and decomposition. As it degraded organic pollutants, the modified wood surface had a good self-cleaning function.

Industrial-scale testing was performed for fine screen reject recovery technology with a mixed office waste (MOW) pulping line. Results showed that the recovery system removed macrostickies and dirt specks with an efficiency of 95.7% to 98.3% and 51.5% to 76.8%, respectively. These results were not affected by the running consistency (0.26% to 1.44%). The recovery system improved the physical strength of the pulp. Relative to untreated rejects, the tensile index increased 5.1% to 15.2%, the tear index increased 6.6% to 11.4%, and the breaking index increased 6.6% to 25.7%. Running consistency had no obvious effects on tensile strength and tear strength, but bursting strength increased with increasing running consistency (%). The volume energy consumption (y) increased with increasing running consistency (x), and a linear relationship of y = 0.73x + 4.2191 (R² = 0.9466) was observed. The specific energy consumption (y) of the pulp decreased with increasing running consistency (x), and the relationship could be expressed as y = 499.67x-0.906 (R² = 0.9959).

Wood processing waste, poplar wood shavings, were used for fiberboard production, and the pretreatment conditions using cellulase were studied using response surface methodology (RSM). After single factors optimization, central level of temperature, dosage, and liquid/solid ratio (LSR) of cellulase pretreatment conditions were obtained. Further optimization to study the influence of the factors was carried out using Box-Behnken design of experiments. A second-order polynomial equation was obtained, and the low p-value (<0.007) implied that the model was highly significant by analysis of variance (ANOVA). The optimized cellulase pretreatment conditions for maximum bending strength (BS) of the fiberboard were determined by ridge analysis as 44.4 °C of temperature, 1.23 U/g of dosage, 4.2 of LSR, and 5 h of pretreatment time. Under the optimized conditions, the BS of the fiberboard reached 25.12 ± 0.35 MPa by validation experiment, which was twice that of the fiberboard without pretreatment. Thus, the cellulase pretreatment should be a good choice to produce high-strength binderless fiberboard.

Insulation pressboard samples were obtained by thermal aging (according to Montsinger’s formula, at 130 °C, the pressboard is heated for 0 to 32 days) and discharge experiments. SEM images of samples were analysed. Image segmentation was applied to calculate the fibre width, cross-sectional porosity, and carbon-trace area. Inter-layer fibre models were established to observe fibre morphology using 3-D reconstruction. The initial discharge voltage decreased with age, and the discharge amounts increased. After 16 days of aging, the fibre width had decreased to between 68.1% and 81.8% of unaged pressboard. As the aging increased, cellulose hydrogen bonds were broken, which affected the expansion of interlayer pores, increasing the porosity of the pressboard. After 32 days of aging, the porosity increased to 2.38 times that of a new pressboard. In addition, the longer the aging, the larger the area of carbon marks caused by the discharge breakdown. With the aggravation of thermal aging, the insulating property of pressboard decreased due to the decrease of fibre width and increase of porosity that further accelerated the damage to the fibre structure. It was concluded that the fibre width and porosity could be used as criteria to judge the degradation of pressboard.

Effects of deep eutectic solvent (DES) treatment were determined for the chemical composition of the sapwood and heartwood of red pine (Pinus densiflora). Two DES systems were made from the mixture of choline chloride (ChCl) and two different hydrogen bond donors (HBDs), namely, lactic acid (LA) and glycerin (GLY), with different molar ratios (1:2, 1:6, and 1:10). The yield of the solid residue after DES treatment decreased with an increase in the HBD concentration and treatment time, indicating that the water-soluble fraction was increased. The amount of solid residue was lower in the DES with LA than in DES with GLY, and higher in sapwood than in heartwood during both DES treatments. There was no substantial change in the lignin content of the samples, each being 24.7 to 29.5 wt.%, based on the mass of the treated product. Similar to the yield of the solid residue, cellulose and hemicellulose content in the treated product decreased with an increase in the HBD concentration and treatment time, and it was higher in sapwood than in heartwood. The cellulose crystallinity exhibited a slight increase with increasing treatment time, but there was no difference among the treatments using different molar ratios and between sapwood and heartwood.