Effect of LC refining intensity on fractionated and unfractionated mechanical pulp

In this study, a comparison of two pulping methods namely mechanical and chemical, on the dissolution of Eucalyptus grandis (E. grandis) wood chips was undertaken. The wood chip pulp was treated with an ionic liquid (IL): 1-allyl-3-methylimidazolium chloride to extract the cellulose. The IL was mixed with unbleached mechanical pulp (UBMP), bleached mechanical pulp (BMP), unbleached kraft pulp (UBKP) and bleached kraft pulp (BKP) in ratios of 10%, 20%, 30%. Each solution contained IL, wood pulp and 2-mL of 16 v/v % of dimethyl sulfoxide (DMSO). The 30 % IL pretreatment was the most effective IL pretreatment. The cellulose yield at 30 % IL pretreatment for UBMP, BMP, UBKP and BKP was 65.12%, 63.82%, 67.43%, 67.15%, respectively. This indicated that the kraft pulping method was more effective than the mechanical pulping method for the yield of cellulose after the IL pretreatment. The Crl value at 30 % IL pretreatment was highest for UBMP (72.03%) indicating that the pretreatment used was the least effective in reducing the cellulose crystallinity. The fractions of E. grandis wood chip namely, lignin, regenerated cellulose and hemicelluloses before and after the IL pretreatment, were characterized by a variety of analytical techniques such as High-Performance Liquid Chromatography (HPLC) (carbohydrates), Fourier Transform Infra-Red Attenuated Total Reflection (FTIR-ATR) (functional groups), Pyrolysis-Gas Chromatography /Mass Spectroscopy (Py-GC/MS) (lignin fractions), Ultraviolet/Visible spectroscopy (UV/Vis) (acid soluble lignin), Thermo Gravimetric Analysis (TGA) (degradation of pulp), X-Ray Diffraction (XRD) (crystallinity) and high resolution Scanning Electron Microscopy (SEM) (morphology). Kraft pulping was the most effective method for the yield of cellulose after the [AMIM][Cl]/DMSO pretreatment. The 30% [AMIM][Cl]/DMSO pretreatment gave the highest S/G ratio indicating that minimal bleaching was required.

Biomass use in chemical and mechanical pulping with biomass-based energy supply

In this paper we present an economic model predictive control (econ MPC) strategy for a two-stage (primary and secondary refining) Mechanical Pulping (MP) process. The MP process is a complex multi-input multi-output (MIMO) nonlinear process with strong interactions among the variables. In order to guarantee both stability and convergence of the closed-loop nonlinear MP process, two different econ MPC schemes are proposed: one with penalty on the increment of the input and one with penalty on the offset of the input from its steady-state target. We demonstrate that both econ MPC schemes achieve significant amount of energy reduction in terms of the specific energy consumed by the process while ensuring closed-loop stability and convergence to a nearby steady-state. In addition, we show that more energy reduction can be achieved by using the econ MPC with penalty on the input increment compared with the other scheme. Simulation results also demonstrate the potential benefits of using econ MPC over the standard MPC technique.

This paper describes a force-based refining intensity applicable to high and low consistency refiners. The intensity is based on forces on bars determined from refiner power, tackle, and operating conditions. Bar forces are linked to forces on fibres through fibre distribution over bars and gap size. Predictions of forces from this intensity were compared to forces measured in a high-consistency primary refiner, reject refiner, and a low-consistency refiner in mechanical pulping. The predicted and measured forces were in good agreement for the reject and low consistency refiner, and somewhat less so for the primary refiner.

The kinetics and reuse of spent liquor in the TEMPO-mediated oxidation of mechanical pulp have been studied. It was found that the oxidation reaction of the mechanical pulp by the 2,2,6,6-tetramethyl piperidine-1-oxyl radical (TEMPO)−NaBr−NaOCl system can be approximately described by first-order kinetics with respect to TEMPO and NaBr. In the concentration range used, the rate constant k is directly proportional to the concentration of TEMPO and NaBr, whereas the concentration of NaOCl determines the end of conversion of the primary alcohol groups on the mechanical pulp into carboxylic acid groups. It was also found that the spent reaction liquor can be recycled and reused with reinforced addition of NaOCl without additional TEMPO and NaBr and remains effective in generating carboxylic acid groups on mechanical pulp.

The compostability of several paper products was determined according to the standards and criteria of the European standardization committee (CEN). The lignin content of the materials seems to be the main reason for the low biodegradability level achieved in the controlled composting test, which is a biodegradability test based on microbial degradation and measurement of carbon dioxide evolution. Mechanically pulped paper, which contains more lignin and more closely resembles natural wood than chemically bleached paper, generated smaller amounts of carbon dioxide. All the chemically bleached papers generated more than 70% of their organic carbon content as CO2, while the mechanically pulped unbleached papers in general generated less than 70%. Paper containing mechanical pulp degrades slower because lignin both interferes the biodegradation of cellulose and becomes incorporated in the humus. The test protocol also defines that, even if the biodegradability of paper products is not tested, their disintegration and effect on compost quality have to be determined. In the present study, we also evaluated a number of disintegration test methods in full-scale composting facilities. According to CEN, the disintegration can be studied either in composter bin-scale test equipment or in full-scale composting facilities. In this study, we only present the data from full-scale composting in which several test methods were used to evaluate the degradation of the samples. The disintegration of the paper products in full-scale composting facilities is highly dependent on the method used. The slowest degradation rate was achieved when the samples were composted in nylon bags.

At present, paper industry has a lot of problems in China, such as the shortage of forest resources and high cost of pulping. Paper industry must be seeking high yield and low cost pulping process. In order to reduce the cost of mechanical pulp and increase the use of mechanical pulp, a lot of research and patent showed that the refining energy consumption of mechanical pulp would be further decreased using the corresponding enzyme to modify fiber of the raw materials before refining. The effects of cellulases modification on masson pine mechanical pulp were investigated in this paper. The modification conditions were as follows: the dosage of enzyme 75IU/g (to bone dry materials), temperature 500C, time 150min, pH value 5.5 and pulp concentration 15%. The effects of cellulase modification on the surface and quality of masson pine fiber of mechanical pulp were investigated by scanning electron microscope (SEM), atomic force microscopy (AFM) and fiber quality analyzer (FQA). It was found from the images of SEM that the original fiber surface was smoothly but markedly corroded after the cellulase modification. Moreover, the modification brought about more external fibrillation and longitudinal tearing during refining. AFM measurement results showed that the fiber surface roughness was improved after the cellulase modification because that the middle lamella, primary wall and outer layer of secondary wall were broken. The results of FQA measurement showed that the average fiber length increased slightly.

Natural fiber based composites have the potential to improve the mechanical properties of plastics while reducing the cost and weight. This study shows a practical method of blending natural-fiber with polypropylene to form a mat and then consolidated into a sheet by hot pressing. The natural fibers assessed were Pinus radiate and Eucalyptus regnan high temperature thermo- mechanical pulps and sisal (Agave sisalana) fibers. The tensile strength was shown to decrease with an increase in fiber content, while the tensile modulus was shown to increase. Tensile and flexural modulus were positively influenced by fiber length. The water performance tests of the sheets generally showed approximately 20% weight gain and approximately 3% thickness swell at 30% fiber content. The natural fiber surface chemical composition was determined by X-ray photoelectron spectroscopy and shown to be primarily covered with hydrophobic material such as lignin and extractives, while polypropylene was shown to be partially oxidized.

The utilization of western red cedar mechanical pulp is limited by low brightness caused by a high chromophore content. In this paper we identify these chromophores and provide a possible mechanism for their formation during the mechanical pulping process. Diffuse reflectance ultraviolet (DRUV) and Fourier-transform infrared (DRIFT) spectra were recorded for western red cedar chemimechanical pulp treated with hydrogen peroxide, sodium borohydride and acetic anhydride. Treatment with hydrogen peroxide was conducted over different time periods. The spectra indicate that three carbonyl-containing chromophores contribute to light absorption in the visible region. Two conjugated ortho-quinones contributed most of the color. These quinones were formed by oxidation and polymerization of lignans during the refining process. The third chromophore was coniferaldehyde. There was a large initial time lag for the reaction of peroxide with coniferaldehyde relative to reaction time with the quinones. We ascribe this to differences in topochemistry. It was deduced that coniferaldehyde was mainly associated with lignin in the interior of the fiber wall, whereas the quinones were derived from lignans that had been deposited on the fiber surface. Identification of the three chromophores provides a basis for studies of the kinetics of brightening of western red cedar mechanical pulps.

BACKGROUND The utility of the ascomycete Hormonema sp. CECT‐13092, an endophytic fungal strain recently isolated and identified from an eucalyptus tree in Spain , was investigated in different biorefineries‐industrial processes. The strain was used to improve the enzymatic saccharification and pulping of Eucalyptus globulus wood; and liquid culture of the strain enriched in laccase activity was used for E. globulus Kraft pulp biobleaching in the presence of acetosyringone as mediator. RESULTS With regard to enzymatic saccharification, treatment with Hormonema sp. and autohydrolysis pretreatment boosted enzymatic hydrolysis (eight‐fold increase in sugar yields compared with control without any pretreatment). This fungus provided 26.7% higher delignification than the control during Kraft pulping and a higher refining degree during mechanical pulping (69° SR vs. 48° SR control). Chemical and mechanical pulps from fungal pretreatment also showed better physical properties than control pulps (increases in tensile, tear and burst indexes of 28.4%, 15.6% and 43.9%, respectively). Regarding biobleaching, after the enzymatic treatment and a hydrogen peroxide stage, a brightness increase (2.3 points %ISO) was obtained. CONCLUSIONS The potential of the endophytic fungal strain Hormonema sp. for biotechnological applications such as fermentable sugars production, biopulping and biobleaching has been demonstrated. In this sense, this is the first study on the use of an endophytic fungus for a biobleaching sequence. © 2016 Society of Chemical Industry

Production of mechanical pulps (MP) have been increased for useful utilization of woods and global environmental problems. However, light-induced color reversion of mechanical pulps is the biggest problem on use of it. But, the problem of the color reversion has not solved yet though many researches on prevention of the color reversion have been conducted.This paper describes about the chemical and biological prevention of light-induced color reversion of mechanical pulps. And furthermore, a mechanism of the color reversion, change of lignins caused by pulping process and effect of the changes on the color reversion, and effect of bleaching of MP on the color reversion are also described.

This paper explores the evolution in the tensile strength of orange pruning fiber-reinforced polypropylene composites. The exploitation of these pruning’s can effectively avoid incineration, with the consequence of CO2 emissions and fire risk, while extending the value chain of the agricultural industry. This biomass was subjected to three different treatments yielding mechanical, thermomechanical, and chemi-thermomechanical pulps. It was found that 20 to 50% of these pulps, together with a coupling agent, were used as polypropylene reinforcement. The evolution in the tensile strength and morphological properties of the fibers, and the effect of treatments on these properties were analyzed. A modified rule of mixtures (mROM) was used to analyze the micromechanical properties of the interface. In addition, the mechanical properties were weighted against the fiber treatment yields. Finally, factors to compute the net contribution of the fibers to the final strength of the composite materials were proposed.

Paper chromatography and thin-layer chromatography (TLC) are two efficient analytical methods that can be used to characterize interactions between the ink (dye) and the paper surface in ink-jet printing. Both methods enable determination of ink adhesion rate as a function of fiber composition, pigment type, amount of binder, and dye fixation agent, etc. Paper chromatography was used to investigate the influence of fiber type and dye fixative on ink adhesion rate (comparison of R F values) and the waterfastness of printing on uncoated papers. The results suggested that Canon printing ink is more suitable for use on papers containing predominantly bleached, wood-free, i.e. chemical, fibers whereas the HP ink proved more appropriate for papers made from mechanical pulp. Addition of as little as 1% ( w/w ) dye fixative significantly improved print waterfastness. TLC was especially useful for optimization of coating color recipes for papers intended for photo-quality prints. The best color results were achiev...

In this study, the effects of low consistency refining (LCR) energy and intensity on mechanical pulp properties have been studied for three different types of reject pulps (softwood TMP, softwood CTMP and hardwood CTMP), which were refined at varying intensity. Resulting pulp properties have been compared with high consistency refining (HCR) of the same reject pulps. For all furnish types, it was shown that LCR can develop pulp properties matching those developed through HCR with significantly less energy. The resulting pulp properties were found to be affected not only by refining intensity and energy, but also by initial fibre morphology. Pilot LCR trials demonstrated that high freeness reject pulp is initially insensitive to refining intensity as specific energy is applied. This enables the first stage of LCR to be carried out at a higher specific energy and intensity, which can reduce the number of stages of LCR required to reach a target quality. This work shows that low intensity LCR is capable of achieving the same tensile index as HCR pulp at a target freeness of 200 ml CSF.

Mechanisms of leucochromophore and chromophore formation in mechanical pulping