Band 38, Heft 1

Interaction between the microwave heating rate and dielectric properties of agricultural wastes is important in identifying suitable microwave operating conditions. This work focuses on the interaction between microwave heating rate (power intensity) and dielectric properties of selected agricultural wastes, namely castor shell, empty fruit bunch and palm kernel shell. Heating rate was recorded every 30 s for 10 min in a 2.45 GHz microwave at power intensities of 100, 300, 450, 600, 700 and 800 W. All materials tested display an increase in heating rate with increasing power intensity. Castor shell and empty fruit bunch at 800 W, and palm kernel shell at 600 W exhibit high heating rates of 0.134, 0.165, 0.247 °C/s, respectively. For dielectric properties, palm kernel shell series shows a high value of loss tangent compared to the other counterparts, indicating its effectiveness to be heated via microwave.

Although organosolv processes using high-boiling solvents have been investigated in recent decades for developing novel industrial processes, there are potential benefits of using high-boiling point solvents for traditional sulphate-based cooking processes, both from an industrial perspective and from a laboratory perspective. Using high-boiling solvents, experiments can be done under atmospheric conditions, thus making it easier to continually monitor laboratory experiments and extracting aliquots at desired intervals. Using such a system, alkaline consumption was monitored during impregnation of spruce chips in glycerol media using chemical charges of 1 M NaOH and 0.1 M NaHS, i. e., kraft pulping conditions, and compared to a similar investigation of alkaline consumption in water media using steel autoclaves. The resulting data was fitted to a first order kinetic model, with an apparent activation energy of 22 kJ mol −1 in glycerol media. Finally, a “normal quality pulp” of kappa number 28 and a viscosity of 1113 ml g −1 was successful produced using a cooking process with an impregnation step at 140 °C for 3 h and a cooking step at 160 °C for 4 h. A nuclear magnetic resonance study on the dissolved lignin produced for said experiment showed characteristics typical of other kraft lignins.

In view of the present situation that the exhaust waste heat of the hot air hood in the paper drying section is too much and the environment is not friendly, a closed heat pump drying system model applied to the exhaust air hood is proposed and established. Effects of evaporation temperature and condensation temperature on supply air temperature, supply air moisture content, system performance coefficient (COP) and dehumidification energy consumption ratio (SMER) were studied. Results show that with the increase of condensation temperature, the supply air temperature is unchanged, and the moisture content of the supply air increase, while the COP and SMER of the system show a downward trend. The moisture content of supply air decrease with the increase of evaporation temperature, while the supply air temperature, COP and SMER all show an upward trend. Therefore, in order to improve the drying characteristics and improve the performance of the heat pump system, the condensation temperature can be reduced and the evaporation temperature can be increased.

This study aims to investigate the applicability and accuracy of different machine learning (ML) methods for predicting paperboard properties based on raw material and process data. The goal is not to find an ML method that can predict all properties simultaneously, but rather the most suitable method for a single property. The examined properties are bending stiffness and the curl. Furthermore, the focus is not on the most accurate prediction model, but on the best model to interpret. The results show that ML methods are applicable for predicting paperboard properties based on raw material and process data, e. g., bending stiffness and curl in machine direction (MD) and cross-machine direction (CD). The feature selection is crucial for the quality of the prediction. Therefore, domain knowledge is needed to select the right features. This selection improves the model and ensures its reliability, comprehensibility, and interpretability. The self-implemented recursive feature addition (RFA) takes the features specified by a domain expert for the feature selection into consideration. It requires less computation time in comparison to the common recursive feature elimination (RFE). The extremely randomized tree (ET) was chosen due to its high interpretability and good results. It achieves a mean absolute error (MAE) for the bending stiffness MD of 0.913 mN m; an MAE for curl MD of 0.058 m −1 (in a value range from 7 mN m to 100 mN m and −1 m −1 to 1 m −1 , respectively); 0.474 mN m and 0.163 m −1 (in a value range from 5 mN m to 45 mN m and −1 m −1 to 2 m −1 , respectively) for the respective CD properties.

We describe a wet creping approach, applicable not only for softwood kraft papers in the grammage range of 30–120 g/m 2 but also for 300 g/m 2 CTMP board. Creping of board requires a certain level of deformability in the material, which is controlled by its solids content. The concept was tested at laboratory scale using a device on which temperature, blade angle and line load could be adjusted. The sample density was decreased by creping due to small-scale delamination of the structure, leading to separate inner layers with a wavy appearance. The strain at break was remarkably increased and agreed well with the theoretical estimate based on the crepe ratio and the breaking strain of the uncreped sample. Simultaneously, tensile strength was reduced by creping. In terms of tensile strength and stretch, 60–70 % solids content during creping was optimal for the tested board.

Especially in the field of paper and print post-processing on an industrial scale, continuous cutting operations generate paper dust. Despite preventive measures like dedusting units, a high paper web velocity induces the release of particulate dust. As a result, the particles settle and accumulate on machine components and in the surrounding area. Resuspended particles around a potential ignition source represent a fire hazard. The prevention of such fire incidents requires frequent servicing and maintenance. However, the shutdown time on industrial scale applications remains cost-intensive. In this research, a cutting plotter executes reproducible knife edge cutting sequences to identify significant parameters affecting the paper dust formation on a macro and micro scale. For this purpose, an extraction system collects the exposed particles along the cutting line. The applied methods include gravimetric determination of the dust mass and dynamic image analysis to characterise particle size and shape. Final results indicate a significant influence of the blade wear condition.

The bending properties of cardboard in the machine direction and cross direction were obtained via three-point bending and elastica bending tests using samples of various span lengths. The bending stiffness, moment at the proportional limit, and moment capacity per unit width were determined, and the effects of the testing method and span length were investigated. In the three-point bending test, the bending stiffness often decreased as the span length decreased because of the effect of the low interlaminar shear modulus of cardboard, and this tendency was more pronounced when the length direction of the sample coincided with the machine direction. Such dependence was less obvious in the moment at the proportional limit. In contrast, when the length coincided with the cross direction, the moment capacity of the cardboard often decreased as the span length increased because the large deflection prevented the accurate calculation of the moment capacity by using elementary beam theory. However, in the elastica bending test, both the bending stiffness and moment capacity could be obtained while reducing the effect of the span length. Therefore, to obtain the bending properties of cardboard, the elastica bending test was determined to be more advantageous than the three-point bending test.

A novel paper multifunctional protective solution was prepared by mixing berberine modified trimethoprimed carboxymethyl cellulose (TMP-DCMC-BBR), KH-791 modified nano-SiO 2 (KH791-SiO 2 ) and hydroxypropyl starch phosphate (HPDSP), and the mechanical properties, optical properties, antibacterial properties, aging resistance, acid and alkali resistance of the paper coated with the protective solution were investigated. It is shown that the paper coated with the multifunctional protective liquid showed good mechanical properties, and has little influence on optical properties of the paper. At the same time, it had good antibacterial properties, aging resistance and acid and alkali corrosion resistance, and there is no obvious change in paper appearance, no decolorization and ink diffusion, which is in line with the principle of “repairing the old as the old and keeping the original appearance”. Moreover, the compound solution has certain reversibility and can absorb a certain degree of ultraviolet rays, so as to weaken the damage of ultraviolet rays to the paper. It is an ideal multifunctional protective liquid for paper and has broad application prospects in paper protection.

Due to the complex storage environment, paper documents will suffer different degrees of damage during storage. Studying the aging behavior of paper after strengthening treatment is an important aspect of evaluate the effect of strengthening agent treatment. In this paper, the aging resistance properties of base paper, APTES, AEAPMDMS, and APTES/AEAPMDMS reinforced samples after dry heat aging and moist heat aging were studied. The results show that in the early stage of aging, the amorphous region of the fiber is mainly degraded gradually. With the passage of time, the crystalline region of cellulose is also degraded continuously, and the crystalline region of cellulose is degraded more significantly during moist heat aging. Compared with the base paper, the AAAS reinforced paper sample can significantly slow down the aging and degradation of the paper sample and has better aging resistance.

Paper-based artifacts, such as ink and wash paintings, paper cuts, etc., when exposed in environment for a long time, are prone to embrittling, yellowing and ageing because of ultraviolet light and weather elements. In a museum, special measurements are adopted to avoid these damages, but for common households, a functional coating is a good solution. However, this is not an easy task as the coating must be removable and cannot damage the articles. Graphene oxide (GO) has the potential as ultraviolet shielding material for the protection of paper-based artifacts, but the application of monolithic GO coatings on paper-based artifacts is difficult. In this work, feasible GO/polyacrylonitrile composite films were prepared and their protection properties for rice paper were explored experimentally. When GO loading reached 2 %, the UV-A and UV-B blocking percentages of the film were 57.47 % and 70.86 %, respectively, with a visible light transmittance of 77.09 %. These films also performed good moisture resistance. With a good flexibility, they could be easily transferred onto and peeled off the rice paper surface without damaging the paper texture and patterns on it. These films basically meet the demand of paper-based artifacts protection.

The use of activated carbon with KMnO 4 activators incorporated on the paper matrix is carried out in this research. Three methods of activated carbon incorporation on paper are carried out to evaluate the paper’s physical parameters and adsorption ability to ethylene. The paper’s physical parameters include grammage, bursting strength, Ring Crush Test (RCT), moisture content, water absorption (Cobb60), and paper microstructures using SEM. Evaluation of the performance of activated carbon paper nanopores as ethylene adsorbent is conducted using GC. The treatment of activated carbon nanopores on non-wood paper causes grammage to increase, but RCT and paper bursting strength decrease. The incorporation of nanopore-activated carbon by the mixing method has produced papers with activated carbon particles spread evenly inside the pulp fibers of the paper. Activated carbon paper with the best adsorption capacity is bamboo+KMnO 4 &mixing with an adsorption capacity of 1,348 ppm and ethylene amount of 88.58 %. Concentration equilibrium is reached in the 25 th minute. The non-linear pseudo-first-order absorbent kinetics model is an appropriate model to describe the equilibrium capacity of ethylene entrant (q e) by nanopore-activated carbon paper with the equation: qt = 1.35734 ( 1 − exp − 0.15312 t ) \mathrm{qt}=1.35734\hspace{0.1667em}(1-{\exp ^{-0.15312\hspace{0.1667em}\mathrm{t}}}) , with R 2 = 0.9981 {\mathrm{R}^{2}}=0.9981 .

The main aim of the present research is to examine the effect of progressive deinking and reprinting on the paper properties of inkjet-printed paper. A typical office copy paper was selected as the base paper and printed using an inkjet printer having at least 50 % ink coverage. Thereafter, it was deinked and reprinted thrice, and its paper properties were measured. The paper properties that were measured were roughness, porosity, opacity, brightness, specular gloss, whiteness, bursting strength, tearing resistance, tensile strength, contact angle, deinkability efficiency, visible dirt area, ink elimination factors, and color differences. The results showed that in comparison to the base paper, the progressively deinked and reprinted paper samples showed an increase in roughness, porosity, opacity, tearing resistance, dirt area, and color difference. On the other hand, there was a decrease in brightness, gloss, whiteness, burst strength, tensile strength, contact angle, deinkability efficiency, and ink elimination factors. The experiment shows that the progressively deinked and reprinted papers can be compared to the base paper in the major paper properties.

In this study, electrophotographic printing and inkjet printing systems were applied to some commercial A4 office papers and their effects on print quality were determined. It is to evaluate the print quality by determining the test parameters that measure the print quality by applying electrophotographic printing and inkjet printing systems to some commercial office papers that have determined the surface properties and optical properties supplied from the market. Print quality was measured by testing with parameters such as delta gloss 60°, print lightness, print chroma, print density. As a result of the tests determined for print quality; print density values were low in A4 office papers with high roughness and porosity values, and the specular gloss values of the samples decreased in both printing applications. In electrophotographic printing; it was determined that darker colors formed with print lightness parameter, and the color scale increases in two-sided printing with print chroma values. It was determined that the color scale of print chroma values increased in two-sided prints. It was determined that mostly some commercial office papers were positively affected by printing on one side in inkjet printing and by printing on two-sided in electrophotographic printing.

In the use of hot melt adhesives in the production of paper-based packaging, the controlled penetration of the adhesive is important to obtain rapid setting rates, good bond strength, and the efficient use of adhesive. Measuring adhesive penetration depth has been limited to cross-sectional images, but quantifying the depth of penetration is difficult from these images. No quantitative method is well established in the literature. Four different techniques are compared to quantitatively measure adhesive penetration depth. Two methods involve separating the paperboard from the adhesive layer. Two other methods use of silicone oil penetration and mercury porosimetry to measure the decrease of pore volume after the adhesive is applied. These methods are compared with samples generated for various parameters. Experiments were conducted using a typical hot melt glue on uncoated and coated paperboard sample. Cross-sectional images from Scanning Electron Microscopy (SEM) confirm the penetration of some samples. The accuracy and repeatability of these methods were compared. Because of some issues with trying to repeatably remove the paper layer for the weight and thickness methods, and the time and cost of the mercury porosimeter method, the silicone oil method is a nice method to characterize the adhesive penetration depth.

Coated paperboard not only has the advantages of traditional paper such as low density and cleanliness, but also overcomes its disadvantages such as poor barrier performance and sensitivity to moisture. It is more and more widely used in forming packaging containers. The current research on mechanical performance and inelastic deformation of paperboard mainly focus on its physical properties and simplified single-blank forming, but the studies on the forming limit diagram (FLD) of paperboard are relatively rare. In this paper, Nakajima tests have been carried out to determine the FLD curves of the polyethylene-coated paperboard blank along the machine direction, cross direction, and diagonal direction. A laminated stamping method for multi-blank is proposed and investigated by experiment and numerical simulation. Up to 5 blanks can be overlapped and stamped in a single punch stroke, and 5 bowl-shaped packaging containers can be formed simultaneously. Compared with the single-blank stamping process, the production efficiency can be greatly improved, but the flange area of the forming parts is easier to wrinkle. However, the wrinkling risk can still be controlled by optimizing the process parameters, such as friction factor and blank holder gap.

The pulp industry is a high natural resources consumer and has a large polluting potential. The pulping sector with the most effluent generation is the bleaching plant. Based on the need of water consumption reduction, this research aimed to evaluate the treatment of the alkaline effluent from an EP-stage bleaching plant and the white water from drying machine using ultrafiltration membranes in order to enable the reuse of the permeate in the process. An ultrafiltration pilot plant was used. Laboratory analyses were performed for the feed, permeate and retentate. Flux and transmembrane pressure (TMP) data were obtained from the pilot plant database. There were an average color and COD removals of 38 % and 39 %, respectively, for the EP-effluent and 58 % and 67 %, respectively for the white water; and a high turbidity and TSS removal (above 98 %) for both effluents. Substantial metals removal such as sodium, potassium, calcium, iron, magnesium and manganese was achieved. Some possibilities to reuse were considered: return to the water treatment plant, cooling of the digester bottom, equipment cooling, reuse in evaporation surface condensers. The use of ultrafiltration for the treatment of the alkaline effluent from the bleaching EP-stage and white water can be an interesting option.

Water system closure in recycled containerboard mills may have reached a technical limit due to the accumulation of organic and inorganic contaminants in the process water. The specific water chemistry characteristics of recycled containerboard mills with restricted water systems were analyzed and a computer model was developed to simulate calcium carbonate solubility in the presence of volatile fatty acids under relevant mill conditions. A strong linear correlation between VFAs and calcium ions was found. The calcium carbonate dissolution mechanism, solubility, and precipitation were investigated. The reaction of VFAs with calcium carbonate results in the formation of bicarbonate and carbonic acid. By binding hydrogen ions, the carbonate has a pH buffering effect. The carbonic acid dissociates into water and CO 2 . Gaseous CO 2 escapes from the water and leads to decarbonization. This mechanism is responsible for the uncoupling of pH from the concentration of VFAs, as well as from the concentration of dissolved calcium ions. The resulting lack of carbonates prevents the precipitation of calcium carbonate. The introduction of CO 2 contained in the biogas produced in anaerobic biological water treatment reverses the dissolution mechanism and causes the precipitation of calcium carbonate. Concentrating technologies such as membrane filtration and evaporation may therefore meet the specific requirements for complete water system closure in recycled containerboard mills better than current commonly used biological treatment.

Reasonable use and disposal of agricultural and forestry wastes become an urgent focus of attention with the dangers of pollution and squandering. In this paper, palm leaves, a typical kind of cellulose-rich agricultural and forestry waste, were attempted to prepare high-valued porous aerogels with cellulose by a short and mild extraction followed by the process of cross-linking with polyvinyl alcohol (PVA). Scanning electron microscope (SEM), Fourier transform-infrared (FTIR), X-ray diffraction (XRD), Bruno-Emmett-Teller (BET), and thermogravimetric analysis (TGA) were applied to examine their structures, chemical composition, and performance compared with hardwood cellulose aerogels. The results showed that palm leaf cellulose could be extracted friendly under mild extraction of 5% NaOH solution for 7 h, following 10% H 2 O 2 solution for 8 h at 80 °C, which inhibits effectively the alkaline hydrolysis of cellulose with the extraction rate of 35.25%, the cellulose purity of 87.12%, and crystallinity of 69.9%. Compared with hardwood cellulose aerogel, the prepared environmentally friendly and recyclable palm leaf cellulose aerogel is a promising application material with similar ultra-low density, high porosity, specific surface area, thermal stability, and better compression resilience, which provides a new technical direction for the high-value application of agricultural and forestry wastes.