Thermomechanical Pulp Research Articles

Effect of Moisture Contents of Raw Materials on the Dimensional Properties of Thermomechanical Pulp Fibers

Effect of Moisture Contents of Raw Materials on the Dimensional Properties of Thermomechanical Pulp Fibers

Development of fibre properties in mill scale: high- and low consistency refining of thermomechanical pulp (part 2) – Importance of fibre curl

Abstract Increased knowledge on the correlation between pulp processing, fibre-properties and paper properties is required to improve fibre-based products. Part 1 of this investigation deals with the effects of HC and LC refining on fibre properties development. LC refining reduced curl and increased tensile index in a manner similar to hot disintegration whereas HC refining increased curl slightly. In this second part, the correlation between fibre curl and handsheet properties of thermomechanical pulp, subjected to low consistency (LC) refining and hot/cold disintegration is examined. Fibre curl decreased by laboratory disintegration and LC refining and showed a linear correlation with increased tensile index and tensile stiffness. Evaluation of fibre property distributions gave a more detailed description of the development of fibre properties. These revealed that disintegration and LC refining gave different fibre curl versus fibre length distributions, even when their average values were similar. These results confirm that analysing fibre property distributions contributes to a more detailed knowledge of the development of pulp quality. Hot disintegration before laboratory testing exaggerated pulp quality and increase internal fibrillation and can therefore be questioned. When hot disintegration is performed before pulp analyses, the impact of LC refining on paper properties may be misjudged.

Geometric changes of TMP fibres due to thermo-hydrolytic disintegration of waste MDF evaluated by three fibre analysers

ABSTRACT Thermo-hydrolytic disintegration of medium-density fibreboard (MDF) is a promising method for recovering fibres. This process, however, may affect the geometry and size distribution of the applied fibres initially obtained by thermomechanical pulping (TMP), and thus, the properties of MDF produced thereof. Optical methods based on image acquisition are increasingly common for geometrical characterisation to assess fibre quality. In this study, we analysed the size distribution of recovered fibres (RF) obtained by thermo-hydrolytic disintegration of urea–formaldehyde-bonded waste MDF and subsequent hammer-milling by using three optical fibre analysers, FibreShape Pro, QICPIC and Valmet FS5, while comparing them to virgin fibres (VF). The analysers use different evaluation methods and therefore gave different absolute values. Thus, size distributions could not be directly compared. Nevertheless, the results provided an indication of the changes that occurred during the manufacturing and recycling process. The RF displayed a similar fibre geometry to the VF, in spite of process-related shortening. Mean fibre length and length-based distribution of the VF were always greater than those of the RF, while fibre width of the hammer-milled RF was slightly greater than that of the VF. The analysers, however, provided substantially different results, especially between FibreShape Pro and QICPIC, although the general tendencies observed for the process-related changes were consistent. It can be concluded that the thermo-hydrolytic disintegration applied to the UF-bonded MDF did not cause any substantial changes in fibre geometry (i.e. fibre shortening). All fibre analysers are capable of detecting these changes, but the absolute values provided can vary widely between the instruments.

Potential energy generation of sludge from a thermomechanical pulp (TMP) mill

Potential energy generation of sludge from a thermomechanical pulp (TMP) mill

Improved thermomechanical and rheological properties of polypropylene composites with thermomechanical pulp for injection molding

AbstractMaterial extrusion and injection molding are prevalent in polymer processing, but wood fiber‐reinforced polymer composites offer eco‐friendly alternatives for industries like automotive, and aviation. Our study explores biocomposites using bleached chemi‐thermomechanical pulp (BCTMP) and polypropylene (PP). BCTMP is rich in cellulose and hemicellulose and quite hydrophilic, while PP's hydrophobic structure creates a disconnect to creating a composite of the two. Traditional methods add costly coupling agents like maleic anhydride polypropylene (MAPP) in an attempt to enhance the adhesion properties of wood‐plastic composites. However, it is worth noting that even in the presence of MAPP, PP maintains its high hydrophobicity and low surface energy, despite exhibiting considerable heterogeneity. Further complexity arises from the thermal degradation characteristics of BCTMP during the melting processing of PP. Our proposed method involves premixing via cryo and planetary ball milling. This boosts PP and BCTMP adhesion, enhancing dispersion quality and mechanical properties without needing coupling agents. Moreover, the premixing of BCTMP and PP forms a thermal buffer layer around BCTMP, minimizing its thermal degradation during processing. This process also ensures even distribution of BCTMP into PP, resulting in a 200% rise in Young's modulus with 30 wt% BCTMP without compromising ultimate tensile strength.Highlights Exploration of biocomposites using bleached chemi‐thermomechanical pulp (BCTMP) and polypropylene (PP) thorough injection molding Implementation of premixing to enhance PP/BCTMP adhesion without coupling agents Premixing reduces thermal degradation of BCTMP, enhances dispersion, and improves mechanical properties Achieving a 200% increase in Young's modulus with 30% BCTMP incorporation, while maintaining ultimate tensile strength

Equilibrium Moisture Mediated Esterification Reaction to Achieve Over 100% Lignocellulosic Nanofibrils Yield.

Lignocellulosic nanofibrils (LCNFs) isolation is recognized as an efficient strategy for maximizing biomass utilization. Nevertheless, achieving a 100% yield presents a formidable challenge. Here, an esterification strategy mediated by the equilibrium moisture in biomass is proposed for LCNFs preparation without the use of catalysts, resulting in a yield exceeding 100%. Different from anhydrous chemical thermomechanical pulp (CTMP0%), the presence of moisture (moisture content of 7wt%, denoted as CTMP7%) introduces a notably distinct process for the pretreatment of CTMP, comprising the initial disintegration and the post-esterification steps. The maleic acid, generated through maleic anhydride (MA) hydrolysis, degrades the recalcitrant lignin-carbohydrate complex (LCC) structures, resulting in esterified CTMP7% (E-CTMP7%). The highly grafted esters compensate for the mass loss resulting from the partial removal of hydrolyzed lignin and hemicellulose, ensuring a high yield. Following microfluidization, favorable LCNF7% with a high yield (114.4 ± 3.0%) and a high charge content (1.74 ± 0.09mmolg-1) can be easily produced, surpassing most previous records for LCNFs. Additionally, LCNF7% presented highly processability for filaments, films, and 3D honeycomb structures preparation. These findings provide valuable insights and guidance for achieving a high yield in the isolation of LCNFs from biomass through the mediation of equilibrium moisture.

FABRICATION OF HIGH STRENGTH PAPER FROM DIFFERENT TYPES OF PHOSPHORYLATED FIBERS USING HOT PRESSING AND FORMING AGENTS

Phosphorylated fibers offer a broad range of applications, particularly in thermal insulation, notably with wood fibers, provided they exhibit improved mechanical characteristics. Despite encountering challenges in applying traditional papermaking methods, the creation of paper or board sheets with phosphorylated pulp fibers remains a challenge. Findings suggest that phosphorylation-modified fibers show increased roughness. Moreover, in comparison with unbeaten kraft sheets (KF) and thermomechanical pulp sheets (TMP), those made from phosphorylated kraft fibers (PKF), using a cationic coagulant and a flocculant, demonstrate significant enhancements in burst index, break index, and tensile energy absorption by 2.12 times, 1.7 times, and 2.77 times, respectively. Similarly, phosphorylated TMP sheets, prepared with a dual polymeric system (coagulant/flocculant), exhibit improvements of 1.42 times, 1.33 times, and 1.82 times, respectively, in these properties. The study emphasizes the ameliorating effect of cationic polymeric agents on the charge impact of phosphorylated fibers on overall sheet quality, while also highlighting the substantial influence of hot-pressing lignin-containing paper on all determined physical properties.

Impact of accelerated aging cycles on the performance of extruded cement-based composites reinforced with non-bleached eucalyptus fibers.

Thermo-mechanical pulping produces well-individualized fibers compared to wood particles and less fragile fibers compared to Kraft pulping, besides presenting higher volume, higher yield, and lower production cost, which can be an exciting alternative for the fiber-cement industries. This study evaluated the impact of soak and dry-aging cycles on the performance of extruded composites reinforced with non-bleached eucalyptus fibers. The cement matrix comprised cement (70%) and limestone (30%). Composites were reinforced with 1 to 5% of eucalyptus fiber by cement mass and tested on the 28th day of cure at 99% relative humidity and after 400 accelerated aging cycles. The water absorption and apparent porosity gradually increased with the reinforcement level. Composites with 4 and 5% fibers showed the highest toughness (0.21 and 0.23kJ/m2, respectively). The aging by 400 soak-dry cycles reduced the composites' water absorption and apparent porosity. The modulus of elasticity (MOE), rupture (MOR), and toughness increased, except for toughness for composites reinforced with 1 and 5% fibers, explained by the cementitious matrix's continuous hydration, fiber mineralization, and natural carbonation. In general, eucalyptus thermo-mechanical fibers were suitable for producing cementitious composites. Cementitious composites with 3% fibers presented a higher MOR, MOE, low water absorption, and apparent porosity after 400 accelerated aging cycles. In addition, the composites with 4% fibers also presented remarkable improvements in these properties. The aging cycles did not result in composites with less resistance, a positive fact for their application as tiles and materials for external use in civil construction.

Mold Fungal Resistance of Loose-Fill Thermal Insulation Materials Based on Processed Wheat Straw, Corn Stalk and Reed.

The present study evaluates the mold fungal resistance of newly developed loose-fill thermal insulation materials made of wheat straw, corn stalk and water reed. Three distinct techniques for the processing of raw materials were used: mechanical crushing (Raw, ≤20 mm), thermo-mechanical pulping (TMP) with 4% NaOH and steam explosion pulping (SEP). An admixture of boric acid (8%) and tetraborate (7%) was applied to all processed substrates due to their anti-fungal properties. The fourth sample group was prepared from SEP substrates without added fungicide (SEP*) as control. Samples from all treatments were separately inoculated by five different fungal species and incubated in darkness for 28 days at 28 °C and RH > 90%. The highest resistance to the colonization of mold fungi was achieved by TMP and SEP processing, coupled with the addition of boric acid and tetraborate, where molds infested only around 35% to 40% of the inoculated sample area. The lowest mold fungi resistance was detected for the Raw and SEP* samples, each ~75%; they were affected by rich amount of accessible nutrients, suggesting that boric acid and tetraborate additives alone did not prevent mold fungal growth as effectively as in combination with TMP and SEP treatments. Together, the achieved fungal colonization scores after combined fungicide and pulping treatments are very promising for the application of tested renewable materials in the future development of thermal insulation products.

Reducing friction between metal and thermo-mechanical pulp using alkyl ketene dimers and magnesium stearate

The friction between natural fibers and metal affects tool life, wear and tear and surface defects of extrudates. The ability of alkyl ketene dimer (AKD) and magnesium stearate (MgSt) to reduce coefficient of friction (COF) between thermomechanical pulp (TMP) and metal were determined at temperatures of 30, 100, and 180 °C and additive concentrations from 0.5 to 5 wt%. The AKD and MgSt were added to TMP sheets through spraying, followed by drying. ATR-FTIR and IR microscopy confirmed the presence of AKD and MgSt on the TMP. AKD addition at 2 wt%, consistently reduced the COF of TMP and metal, whereas MgSt reduced COF at 100 and 180 °C, only. No further reduction in COF was observed at 5 wt% of AKD or MgSt.

Isolation of arabinose and galactose from industrial sidestreams in high yield and purity

Monosaccharides such as L-arabinose (Ara) and D-tagatose (derived from D-galactose, Gal) are low-calorie sweeteners associated with improved glycaemic and insulin control compared to disaccharides such as sucrose. However, alternative sources and better sugar-sugar separation methods are needed to improve the sustainability and economics of their production. Here, these sugars were obtained from purified and ultrafiltered compression screw pressate (CSP) of thermo-mechanical pulping of softwood (Pinus radiata) and orange peels (OPs). Ba-substituted zeolite X (BaX) molecular sieves showed superior separation performance of Ara from other sugars compared to conventional Ca-form ion exchange resin. To facilitate subsequent separation of sugars, OP hydrolysates were fermented to leave just Ara and Gal, while OP pectin was hydrolysed to generate a Gal-rich mixture. Overall, BaX has good potential for separating Ara from Ara-rich hydrolysates containing several different sugars. It is also suited for separating Ara and another monosaccharide such as Gal or Xyl in the absence of other sugars.

Selectively fractionate hemicelluloses with high molecular weight from poplar thermomechanical pulp by tetramethylammonium hydroxide

Selective fractionation of hemicelluloses is of great significance for realizing high-value application of hemicelluloses and comprehensive utilization of lignocellulosic biomass. Tetramethylammonium hydroxide (TMAH) solvent has been confirmed as a promising solvent to selectively fractionate hemicelluloses from holocellulose. Herein, TMAH solvent was adopted to pretreat poplar thermomechanical pulp (PTMP) for the selective fractionation of hemicelluloses and enhancement of enzymatic hydrolysis performance of residues. The maximal hemicelluloses yield (65.0 %) and excellent cellulose retention rate (93.3 %) were achieved after pretreatment by the 25 wt% TMAH solvent, while the delignification was only 33.9 %. The hemicelluloses fractions could be selectively fractionated with high molecular weights (109,800–118,500 g/mol), the contents of Klason lignin in them were low (3.2–5.9 %), and the dominating structure of them was 4-O-methylglucurono-β-D-xylan. Compared to the H2SO4 and NaOH methods, the hemicelluloses fractionated by TMAH method exhibited higher yields, more complete structures and higher molecular weights. Furthermore, the crystalline structure of cellulose practically remained stable, and the highest yield of enzymatic hydrolysis glucose was 57.5 %, which was 3.3 times of that of PTMP. The fractionation effectiveness of TMAH solvent was not significantly reduced after repeatedly recycling. This work demonstrated TMAH solvent could selectively fractionate hemicelluloses from PTMP and efficiently promote sustainable poplar-based biorefinery.

Alkyl ketene dimer modification of thermomechanical pulp promotes processability with polypropylene

AbstractAlkyl ketene dimers (AKDs) are known to efficiently react with cellulose with a dual polarity in their structure: a polar component and a nonpolar component. AKD of three different carbon chain lengths, 4, 10, and 16 carbons have been synthesized, and thermomechanical pulp (TMP) fibers were modified by them. The modification of TMP fibers with AKD resulted in an increased water contact angle, showing the presence of the AKDs on the TMP fibers and a new carbonyl peak in the IR spectra, suggesting modification of the TMP fibers with AKD groups. Calculating the Hansen solubility parameters of AKD and AKD conjugated to TMP in polypropylene (PP) indicates improved compatibility, especially of longer chain AKD and TMP AKD. The rheological studies of the composites showed that the AKD with the longest carbon chain decreases the melt viscosity of the PP‐TMP‐AKD composite, which combined with the shape and the color of the extruded composite filaments indicates improved flow properties and reduced stress build up during processing. The research findings demonstrate the ability of AKD to enhance the dispersibility and compatibility of natural fibers with PP.

The Effect of Cellulose Nanofibres on Dewatering during Wet-Forming and the Mechanical Properties of Thermoformed Specimens Made of Thermomechanical and Kraft Pulps.

Due to environmental concerns regarding single-use plastic materials, major efforts are being made to develop new material concepts based on biodegradable and renewable resources, e.g., wood pulp. In this study, we assessed two types of wood pulp fibres, i.e., thermomechanical pulp (TMP) and Kraft pulp fibres, and tested the performance of the fibres in wet-moulding and thermopressing trials. Kraft pulp fibres appeared to retain more water than TMP, increasing the dewatering time during wet-moulding and apparently increasing the compression resistance of the pulp during thermoforming. Additionally, cellulose nanofibres (CNF) were added to the pulps, which improved the mechanical properties of the final thermopressed specimens. However, the addition of CNF to the pulps (from 2 to 6%) had a further decrease in the dewatering efficiency in the wet-moulding process, and this effect was more pronounced in the Kraft pulp specimens. The mechanical performance of the thermoformed specimens was in the same range as the plastic materials that are conventionally used in food packaging, i.e., modulus 0.6-1.2 GPa, strength 49 MPa and elongation 6-9%. Finally, this study demonstrates the potential of wood pulps to form three-dimensional thermoformed products.

Pilot-Scale Production of Hemicellulose Ethers from Softwood Hemicelluloses Obtained from Compression Screw Pressate of a Thermo-Mechanical Pulping Plant.

Bio-derived materials are becoming increasingly sought-after as a sustainable alternative to petrochemical-derived polymers. In the present pilot-scale study, a hemicellulose-rich compression screw pressate, obtained from the pre-heating stage of thermo-mechanical pulping (TMP) of radiata pine, was purified by treatment with adsorbent resin (XAD7), then ultrafiltered and diafiltered at 10 kDa to isolate the high-molecular weight (MW) hemicellulose fraction (yield 18.4% on pressate solids), and, finally, reacted with butyl glycidyl ether to plasticise the hemicelluloses. The resulting light brown hemicellulose ethers (yield 102% on the isolated hemicelluloses) contained ca. 0.5 butoxy-hydroxypropyl side chains per pyranose unit and had weight- and number-average MWs of 13,000 Da and 7200 Da, respectively. The hemicellulose ethers may serve as raw material for bio-based products such as barrier films.

Advanced design and operation of Energy Hub for forest industry using reliability assessment

A large part of the refining heat production in the thermomechanical pulp mill can be recovered to supply the paper machine heat demand. This study introduces a novel approach for the heat integration of a thermomechanical pulp mill and paper machine using Energy Hub. An Energy Hub consisting of a steam generator heat pump and the electric boiler is integrated with the thermomechanical pulp mill to provide the heating demand of the paper machine. The advanced cost-efficient design and operation of the Energy Hub are investigated in this research by integrating thermo-economic analysis, reliability & availability assessment, and load profile prediction. The thermo-economic analysis combines economics and thermodynamics, which is necessary for energy system unit commitments. Reliability assessment will lead to more accurate modeling of real-life system operating conditions since system components' availability is considered in the design process. Load profile prediction estimates the Energy Hub load for the next hour, which helps with the optimal operation of the Energy Hub.Different state-of-the-art long-short-term memory (LSTM) neural network models have been developed to achieve the best time series model for refining heat prediction in the thermomechanical pulp mill. Results show that all the time series models are effective for refining heat prediction, while Bidirectional LSTM appears to perform better than others with the correlation coefficient and root mean square error of 0.9 and 0.15, respectively. In addition, the proposed Energy Hub design approach is compared with the conventional design method. The proposed design method offers a robust design that isn't impacted by unsupplied demand penalty rates. Depending on the penalty rates, the total system cost could decrease by 14%-28% utilizing the proposed design method.

Fertirrigation with nanofiltration retentate from thermomechanical pulp mill effluents

The objective of the present study was to evaluate the potential for using the retentate from nanofiltration (NF) treatment of thermomechanical pulp (TMP) effluent for fertirrigation. Nanofiltration retentates from tertiary effluent treatment from a Brazilian TMP pulp mill were used. Electrical conductivity (EC) and the concentration of both metals (Mn2+, Mg2+, Fe2+, Ca2+, Na+, K+, Cu2+) and chlorides in the NF retentate were evaluated. The sodium (SAR) and potassium (PAR) adsorption ratios were calculated. The risks of increasing the salinity, effects on the infiltration rate, toxicity and excess nutrients were evaluated according to the American and European standards, and application according to crop and soil were analyzed according to the Brazilian standard. The NF retentate is classified as irrigation water Class I for the risks of reduced water infiltration into the soil, availability of nutrients and the concentration of copper and iron, Class II for the risks of toxicity, pH and concentration of manganese and Class III for the risks of salinity and concentrations of TS, TSS and turbidity, according to American and European standards. The salinity content and the physicochemical characteristics classify the effluent NF retentate, according to the Brazilian standard, as fresh water and Class III for irrigation. The NF retentate from thermomechanical pulp mill effluents, according to both the American and the European standards, cannot be used for fertirrigation, as it is classified as Class III. However, the Brazilian standard allows its use for the irrigation of any tree species, cereals and forages and as a source of nutrients to reduce fertilizer use. The retentate can be applied to highly salt-tolerant plant crops such as Eucalyptus globulus, Eucalyptus camaldulensis and sugarcane, and may be used in soil with a basic pH and high permeability.

Biocomposite panels with unidirectional core stiffeners − 3-point bending properties and considerations on 3D printing and extrusion as a manufacturing method

Sandwich panels with unidirectional core stiffeners are known for their relatively high bending stiffness at low weight, stability under compressive and shear loads and energy absorption capability. In this study, 3D printing was used to screen biocomposite sandwich panels easily and preliminarily with different unidirectional core stiffener designs. Thermomechanical pulp (TMP) fibre-reinforced poly(lactic acid) (PLA) was used in this study.A corrugated, trapezoid and arched cell structure were tested experimentally and numerically using a bimodular material model, accounting for different behaviour in tension and compression. The trapezoid structure showed the best flexural properties of the three 3D-printed sandwich beams. It was chosen to be explored further, manufacturing it by extrusion. Extrusion is a production process likely to be used in industry on a larger scale.Basic material properties of the biocomposites were obtained from injection moulded dogbone specimens. The flexural properties of the extruded panels were measured experimentally and simulated using finite element analysis. Simulations were done with a hyperelastic material model. Predictions and experiments were in adequate agreement, allowing such kind of simulation to be used for extruded biocomposite sandwich panels.

Isolation and purification of high-molecular weight hemicelluloses from radiata pine wood chips prior to thermo-mechanical pulp (TMP) production

Abstract A novel thermo-mechanical pulping (TMP) process has been developed to produce a by-product rich in high-molecular weight (MW) hemicelluloses, a potential raw material for barrier coatings and films. This process uses prehydrolysis to solubilise the hemicelluloses followed by chip compression to separate the soluble material from the wood matrix. The pressate from the chip compression stage was dark-coloured and had a high content of high-MW hemicelluloses and lignin. However, isolating the high-MW material from the pressate directly by ultrafiltration was not feasible because of membrane fouling by dissolved lignin and wood extractives, while coloured impurities are undesirable for many potential applications. To solve these problems the pressate was purified using XAD adsorbent resin to remove low-MW lignin, extractives and colour. Ultrafiltration of the purified pressate yielded lightly coloured high-MW hemicellulose with a low content of lignin and well suited for barrier films and coatings.

Comparison of membrane fouling during ultrafiltration with adsorption studied by quartz crystal microbalance with dissipation monitoring (QCM-D)

Even though membrane technology is used in numerous industrial applications, membrane fouling is still a major challenge. Valuable information on the formation kinetics and structure of the fouling layer can be obtained by in situ real-time monitoring. Quartz crystal microbalance with dissipation monitoring (QCM-D) enables the study of adsorptive fouling in situ on a model membrane. However, so far, there has been no in-depth investigation as to what extent observations from QCM-D relate to fouling during membrane filtration. This gap is here approached by comparing membrane fouling during ultrafiltration with QCM-D measurements using the same feed (process water from thermomechanical pulping) and the same material in the polymer film as in the membrane (hydrophilized polysulfone). The performance at two temperatures (25 °C and 50 °C) was studied. Fouling was analyzed by flux measurements, changes in frequency and dissipation over time with QCM-D, and surface characterization of the membrane samples and QCM-D sensors. QCM-D revealed an increase in rigidity of the fouling layer at 50 °C with time, which was consistent with a higher irreversible resistance during ultrafiltration. This was presumably caused by structural changes of hemicelluloses and colloidal wood extractive droplets in the process water at the higher temperature. The study shows that findings from QCM-D on the attachment of foulants on polymer films are comparable to membrane fouling. Thus, QCM-D, together with complementary analytical methods, can provide valuable insights on the development of membrane fouling of e.g., industrial wastewater.