Addition Of Kraft Lignin Research Articles

Comparing industrial and analytical kraft lignins as biobased UV-protective additives in coatings

Lignin as the second most abundant biopolymer on Earth has the potential to become the alternative to petroleum-derived materials. It exhibits excellent UV absorption ability due to its aromatic structure and the presence of numerous phenolic, ketone, and intramolecular hydrogen bonds. Due to its complex nature, it is important to investigate its properties which is a very important step towards the valorization of lignin. Revealing its structural complexity allows for a better examination of its influence on the properties of the final lignin-based materials. In our research, we used two different kraft lignins: commercial analytical kraft lignin (AL) and industrial LignoBoost kraft lignin (KL) as UV-protect additives in BPA(Bisphenol A)-free polymer coatings based on diurethane dimethacrylate (DIUR). The maximum addition of KL and AL was 2 wt%. Both lignin samples were characterized in detail (composition analysis, ash content, molar mass and polydispersity, surface morphology, thermal properties, and quantitative measurement of hydroxyl group content). We investigated the influence of lignins on the textural and thermal properties of the coatings. Finally, we studied the application of lignin as a value-added UV-protective component by UV-Vis electronic absorption spectroscopy. KL with a higher purity and lower number of aliphatic OH had a better dispersion in the polymer matrix than AL lignin which had more agglomeration in the polymer matrix. The better dispersion resulted in producing a smoother surface in the coatings made from KL. Finally, a noticeable and significant impact of KL additive on the photoprotective properties of the coating material was demonstrated. These results showed a potential application and opportunity in the valorization of available industrial lignins toward sustainable and value-added products.

Viscoelastic behavior of pressure-sensitive adhesive based on block copolymer and kraft lignin

ABSTRACT Practical adhesion of pressure-sensitive adhesives (PSAs) is strongly dependent on their viscoelastic properties. The use of biobased materials emerged as an effective approach to modify the rheological, mechanical, and adhesive properties of PSAs. The biopolymer kraft lignin (KL), a by-product of pulp and paper manufacturing, appeared as a potential candidate for modifying the adhesive behavior of PSAs. In this study, we developed a block copolymer-based PSA by incorporating a hydrocarbon resin (HCR) and kraft lignin into the block copolymer polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS). “Viscoelastic windows”, which describe the potential application of a PSA based on its viscoelastic behavior, were constructed for PSAs with the addition of KL. These results demonstrate the potential for application as a high-shear PSA due to the increased energy dissipation of the samples. Practical adhesion was evaluated using probe tack tests and lap shear strength measurements, which effectively demonstrated an increase in the cohesive strength of the PSA with an optimized concentration of 5 wt% KL.

Effect of the combined addition of ultrasonicated kraft lignin and montmorillonite on hydroxypropyl methylcellulose bionanocomposites.

Although hydroxypropyl methylcellulose (HPMC) has been proposed as renewable substitute for traditional plastic, its barrier and active properties need to be improved. Thus, the combination of an organic residue such as kraft lignin (0-10% w/w) and a natural clay such as montmorillonite (3% w/w) by application of ultrasound can significantly improve HPMC properties. This is most likely due to the close interaction between lignin and montmorillonite, which leads to delamination of the clay and improves its dispersion within the HPMC matrix. Specifically, the addition of kraft lignin to the bionanocomposite films provided them with UV-shielding, antioxidant capacity and antibacterial activity. The incorporation of 3% montmorillonite resulted in reductions of 65.8% and 11.4% in oxygen (OP) and water vapor permeabilities (WVP), respectively. Moreover, a reduction of 43.8% in WVP was achieved when both lignin (1%) and montmorillonite (3%) were incorporated, observing a synergistic effect. Thus, the HPMC bionanocomposite with 1% lignin and 3% montmorillonite, presented good thermal stability and mechanical strength with significantly improved gas barrier permeability, as well as UV-shielding (maintaining a good transparency), antioxidant and antibacterial activities.

Taxonomic and functional dynamics of the soil microbiome from a tropical dry forest in kraft lignin-amended microcosms

The Caatinga, a Brazilian dry tropical forest that sheds its leaves seasonally, harbors diverse lignocellulose-degrading microbes as a valuable source of lignin-modifying enzymes useful for the chemical and biofuel industry. Nonetheless, the detailed process of lignin decomposition in soils is still poorly understood due to most studies focusing on the biodegradation of non-ligninolytic components of plant biomass (i.e., cellulose, hemicellulose, and oligosaccharides). Hence, the microbial dynamic was investigated in kraft lignin (KL) amended soil microcosms incubated at 45 °C for 9, 18, and 27 days. The changes in the GC-MS profile indicated rapid and complete biodegradation of lignin-derived compounds (i.e., phenol, guaiacol, paracyclophane, eugenol, benzene, ethisterone, and methadone N-oxide) by the microbial ligninolytic systems. Metabarcoding analyses showed that species richness (Chao 1 index from 14313,6 ± 338 to 7230,4 ± 1056) and diversity (H′ index from 7,9 ± 0,05 to 5,6 ± 0,6) decreased in response to KL addition. However, the bacterial diversity was stabilized from the 18th to the 27th day, shaping a soil bacterial community dominated by members of the Proteobacteria (Bordetella and Roseomonas), Firmicutes (Bacillus, Pullulanibacillus, Lysinibacillus, Cohnela, and Ornithinibacilus), and Actinobacteria (Isoptericola, Saccharomonospora, and Beutenbergia) phyla, some of which have not yet been reported as able to degrade lignin. Although the KL addition has promoted the extinction of microbial taxa, the co-occurrence networks reveal high modularity values (0.92) of the microbial structure in the 18th and 27th days of KL-amended soil microcosms, indicating metabolic plasticity even with the ecological disturbance. Some individual taxa clustering into more distinct modules might be explained by the emergence of new ecological niches resulting from the heterogeneous features of KL. Metagenome-based evidence suggests that key bacterial (Bordetella and Streptomyces), and fungal (Aspergillus) members may play synergistic ecophysiological roles in decomposing lignin-derived compounds by carrying the most genes encoding lignin-modifying enzymes belonging to the auxiliary activity (AA) family. The great increase of Aspergillus-affiliated genes of the AA9 family (log ratio of 1.46), which includes the copper-dependent lytic polysaccharide monooxygenases (LPMOs), suggests a key role in lignin-derived compounds degradation. Overall, the insights gathered herein reveal the microbial dynamics of a tropical dry forest soil in kraft lignin-amended microcosms and open perspectives for a rational exploration of potentially novel enzymes and microbial candidates for biotechnological applications.

Multifunctional lignin-poly (lactic acid) biocomposites for packaging applications.

Lignin is the most abundant aromatic biopolymer with many promising features but also shortcomings as a filler in polymer blends. The main objective of this work was to improve the processability and compatibility of lignin with poly (lactic acid) (PLA) through etherification of lignin. Commercial kraft lignin (KL) and oxypropylated kraft lignin (OPKL) were blended with PLA at different weight percentages (1, 5, 10, 20, and 40%) followed by injection molding. Low lignin contents between 1 and 10% generally had a favorable impact on mechanical strength and moduli as well as functional properties of the PLA-based composites. Unmodified lignin with free phenolic hydroxyl groups rendered the composites with antioxidant activity, as measured by radical scavenging and lipid peroxidation tests. Incorporating 5–10% of KL or OPKL improved the thermal stability of the composites within the 300–350°C region. DSC analysis showed that the glass transition temperature values were systematically decreased upon addition of KL and OPKL into PLA polymer. However, low lignin contents of 1 and 5% decreased the cold crystallization temperature of PLA. The composites of KL and OPKL with PLA exhibited good stabilities in the migration test, with values of 17 mg kg−1 and 23 mg kg−1 even at higher lignin content 40%, i.e., well below the limit defined in a European standard (60 mg kg−1). These results suggest oxypropylated lignin as a functional filler in PLA for safe and functional food packaging and antioxidant applications.

Evaluation of the physical-mechanical and energy properties of coffee husk briquettes with kraft lignin during slow pyrolysis

The objective of the study was to evaluate the properties of briquettes produced with coffee husks with the addition of kraft lignin for the production of solid biofuels of high physical-mechanical and energetic quality and to analyze the feasibility of converting these briquettes into co-products with higher energy value at from the pyrolysis process. The ratios of kraft lignin to the coffee husk mass were: 10%, 20% and 50%. The briquetting was performed at temperature 120 °C and at a pressure of 15 MPa for 15 min. The physical mechanical characteristics such as apparent density and compressive strength were determined. Slow pyrolysis was performed in 350 °C, 400 °C and 450 °C at a heating rate of 5 °C/min; the final residence time was 1 h. The product yields were calculated at the end of the pyrolysis process. The chemical compounds present in the bio-oil were identified by gas chromatography mass spectrometry (GC-MS) and the biochar was evaluated for proximate analysis, higher heating value (HHV) and Fourier transform infrared spectroscopy with total reflectance attenuated (FTIR-ATR). The briquettes produced with 50% of lignin kraft showed higher apparent density and compressive strength. The pyrolysis performed at 350 °C of the briquettes with 50% lignin favored the production of biochar, on the other hand the pyrolysis performed at 350 °C of the briquettes with 10% lignin provided a higher bio-oil yield. In the bio-oil obtained in the pyrolysis at 400 °C of briquettes with 50% lignin kraft, the greatest production of phenolic compounds occurred. On the other hand, the greatest yield of nitrogen compounds (caffeine) occurred in pyrolysis at 350 °C of briquettes with 20% kraft lignin. The chemical and energetic properties of biochars did not vary considerably in the studied pyrolysis temperature ranges. However, the use of the thermochemical process enhanced the energetic properties and the FTIR analysis showed that biochars have become more aromatic and carbonaceous, in relation to the raw agro-industrial residues. It is concluded that the combination of the different agro-industrial residues (coffee husk and kraft lignin) can offer a sustainable solution for part of the energy scenario, considering that both the properties of the briquettes and the characteristics of the pyrolysis products have been improved.

Improving the properties of botanical concrete based on waste concrete, wood, and kraft lignin powder

Botanical concrete (BC) is a novel sustainable material that can simultaneously recycle concrete and wood waste without using cement. It has potential for use provided its high water absorption and low stability, caused by the inclusion of hydrophilic wood particles, are mitigated. This study aims to improve the water resistance of BC by experimenting with forming conditions and varying the amounts (0–20%) of hydrophobic kraft lignin that is added. The investigations were conducted, using water-immersion and three-point-bending tests, to determine the water resistance (water absorption, swelling, spring back) and bending strength of BC. Scanning electron microscopy (SEM) and systematic analysis of the effects of the composition of BC were performed to understand its behavior. Experimental results show that the water resistance and bending strength of BC could be enhanced by changing the forming conditions and by the addition of kraft lignin. Kraft lignin content of up to 20% can significantly improve the performance of BC, providing a new insight into its utilization and its added value as a renewable resource. SEM results suggest that the plasticization of wood particles and the excellent fusion of kraft lignin with the particles, aided by the alkaline concrete powder, might help enhance the performance of BC.

Improvements in thermal and mechanical properties of composites based on thermoplastic starch and Kraft Lignin

Thermoplastic starch (TPS) is a widely studied biopolymer as an alternative to the use of conventional polymers. In this sense, the incorporation of fillers or reinforcements coming preferably from other substances of natural origin, can be an alternative to try to improve some mechanical and thermal properties of starch polymers. Thus, Kraft Lignin (KL), can be an excellent filler to be incorporated, since it presents mechanical and thermal properties and reduces the cost and weight of the final compounds. TPS films were prepared by casting using dimethyl sulfoxide (DMSO) as solvent and additives with 2, 4 and 8% KL. Characterization of TPS films and compositions with KL were carried out by Fourier-Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM), Thermogravimetric Analysis (TGA), Dynamic Thermomechanical Analysis (DMTA), tensile testing and contact angle. Samples were also analyzed for biodegradation and for the ability to remove contaminants in water, Metil Orange (MO), by Ultraviolet-Visible Spectroscopy (UV–Vis). The FT-IR spectra of the films showed bands typical of functional groups derived from starch and lignin, with the intensity of these bands varying among the samples studied. Micrographs revealed slightly different morphologies among the films, but all showed irregular shapes with structures that appeared as plots. Increasing the percentage of KL led to an increase in contact angle values, showing a more hydrophobic behavior. In the TGA analysis, it was possible to observe a change in the main degradation event of the films for lower temperatures, especially of TPS – 4 and 8% KL compared to the TPS film. Films with KL had the peak of maximum degradation shifted to temperatures below the starch film, where the decrease in intensity of the main peak in the TPS - 4% KL and TPS - 8% KL samples demonstrates that there was less mass loss in the event. There was also in the percentage of residue as the addition of KL was increased The DMTA analyses allowed for the conclusion that presence of KL in TPS film allowed for an increase in its energy storage property, and that the loss modulus followed a decreasing order of storage modulus values to TPS - 8% KL from TPS. For the tensile strength property only TPS - 4% KL has significant improvement, and the elongation at break showed an increase for TPS – 4 and 8% KL compared to TPS. Samples showed a continuous and progressive biodegradation process, being completely biodegraded within 10 days. The monitoring of the ability to remove contaminants from water by UV–Vis, also showed promising results of compounds for this application. The best results were obtained, in most tests, for the TPS- 4% KL films.

Tuning the Adhesive Properties of Soy Protein Wood Adhesives with Different Coadjutant Polymers, Nanocellulose and Lignin.

Commercial wood adhesives are based on products that contain formaldehyde; however, environmental and health concerns about formaldehyde emissions from wood products have influenced research and development efforts in order to find alternative, formaldehyde-free products for wood adhesives. In this work, different soy protein-based wood adhesives are proposed, and their performance is compared to commercial urea formaldehyde (UF) adhesive. Soy protein-based wood adhesives were prepared using either soy protein isolate (SPI) or soy protein flour (SF) with different coadjutant polymers: polyethylene oxide (PEO), hydroxypropyl methylcellulose (HPMC), cellulose nanofibrils (CNF) or polyvinyl alcohol (PVA) with and without addition of kraft lignin. The effects of the type of soy protein, solids content, coadjutant polymer and lignin addition were investigated. The wood adhesive formulations were tested on the bonding of hardwood (white maple) and softwood (southern yellow pine) and the dry shear strength of test specimens was measured according to method ASTM D905-08. The adhesive formulations with SPI achieved significantly higher values than those with SF. The dry shear strength of the adhesives varies depending on the coadjutant polymer, the wood species and the addition of lignin.

Lignin-Containing Coatings for Packaging Materials-Pilot Trials.

One severe weakness of most biopolymers, in terms of their use as packaging materials, is their relatively high solubility in water. The addition of kraft lignin to starch coating formulations has been shown to reduce the water solubility of starch in dry coatings. However, lignin may also migrate into aqueous solutions. For this paper, kraft lignin isolated using the LignoBoost process was used in order to examine the effect of pH level on the solubility of lignin with and without ammonium zirconium carbonate (AZC). Machine-glazed (MG) paper was coated in a pilot coating machine, with the moving substrate at high speed, and laboratory-coated samples were used as a reference when measuring defects (number of pinholes). Kraft lignin became soluble in water at lower pH levels when starch was added to the solution, due to the interactions between starch and lignin. This made it possible to lower the pH of the coating solutions, resulting in increased water stability of the dry samples; that is, the migration of lignin to the model liquids decreased when the pH of the coating solutions was reduced. No significant difference was observed in the water vapor transmission rate (WVTR) between high and low pH for the pilot-coated samples. The addition of AZC to the formulation reduced the migration of lignin from the coatings to the model liquids and led to an increase in the water contact angle, but also increased the number of pinholes in the pilot-coated samples.

A Comparison of the Influence of Kraft Lignin and the Kraft Lignin/Silica System as Cell Carriers on the Stability and Efficiency of the Anaerobic Digestion Process

This study compares the effects of pure kraft lignin and the kraft lignin/silica system (1:4 by weight). The comparative analysis of the physicochemical properties of both carriers showed that the kraft lignin/silica system was characterised by better properties. The experiment conducted in the study involved continuous anaerobic digestion under mesophilic conditions. Three samples were degraded in the following order: (i) sewage sludge (SS), (ii) SS with the addition of kraft lignin, and (iii) SS with the addition of the kraft lignin/silica system. A quantitative analysis of the digestate samples was carried out by means of in situ fluorescence. It showed more intense proliferation of microorganisms in the SS + kraft lignin/silica variant than in the sample with pure kraft lignin. The highest amount of biogas was obtained in the SS + kraft lignin/silica variant (689 m3 Mg−1 VS, including 413 m3 Mg−1 VS of methane; VS—volatile solids). There were comparable amounts of biogas in the SS variant (526 m3 Mg−1 VS of biogas, including 51% of methane) and the SS + kraft lignin variant (586 m3 Mg−1 VS of biogas, including 54% of methane). The research clearly showed that the material with a high share of silica was an effective cell carrier.

Lignin-based dual component additives as effective electrode material for energy management systems

A functional PbO-lignin electrode hydrid material composite was designed and manufactured. Moreover, its connection efficiency was confirmed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). We noted that the superficial layers of PbO combined with layers of the biopolymer and that oxygen atoms present in both materials had influence on the chemical environment of the neighboring compound. Hence, it can be said that the addition of PbO significantly contributes to the improvement of thermal stability of the final inorganic-organic system. In the framework of the study, the dispersive, morphological and structural characteristics were determined using scanning electron microscopy (SEM) and laser diffraction method. Electrochemical studies indicated that the PbO-lignin material exhibits better electrochemical properties compared to PbO without the addition of kraft lignin (increased capacitance, lower charge transfer resistance), as the specific capacitance after 5000 charge/discharge cycles was still at 95% of the initial value. Such promising operating parameters show that this material can be successfully used as an electrode material for energy management systems.

Effect of Lignin Modification on Properties of Kenaf Core Fiber Reinforced Poly(Butylene Succinate) Biocomposites.

In this study, the effects of lignin modification on the properties of kenaf core fiber reinforced poly(butylene succinate) biocomposites were examined. A weight percent gain (WPG) value of 30.21% was recorded after the lignin were modified with maleic anhydride. Lower mechanical properties were observed for lignin composites because of incompatible bonding between the hydrophobic matrix and the hydrophilic lignin. Modified lignin (ML) was found to have a better interfacial bonding, since maleic anhydrides remove most of the hydrophilic hydrogen bonding (this was proven by a Fourier-transform infrared (FTIR) spectrometer—a reduction of broadband near 3400 cm−1, corresponding to the –OH stretching vibration of hydroxyl groups for the ML samples). On the other hand, ML was found to have a slightly lower glass transition temperature, Tg, since reactions with maleic anhydride destroy most of the intra- and inter-molecular hydrogen bonds, resulting in a softer structure at elevated temperatures. The addition of kraft lignin was found to increase the thermal stability of the PBS polymer composites, while modified kraft lignin showed higher thermal stability than pure kraft lignin and possessed delayed onset thermal degradation temperature.

Synthesis and characterization of lignin-polyurethane based wood adhesive

The present work aims to evaluate the influence of addition of kraft lignin in moisture curing polyurethane (PU) based wood adhesives. The mechanical, thermal properties and chemical structure of the adhesive were studied. The lignin-PU adhesives were obtained by replacing 1%, 3% and 5% of polypropylene glycol (PPG) by Kraft lignin and further reacted with monomeric diphenylmethanediisocyanate (MDI). The aliphatic hydroxyl level of lignin was not taken into consideration in the stoichiometry, in order to find out effect on % free NCO of the final product. The chemical structure of the synthesized lignin-PU adhesives were analyzed by Fourier transform infrared spectroscopy (FTIR). The lap shear strength of the adhesives was tested by bonding canarium wood substrates. The results illustrated that by increasing the weight % of lignin in such lignin-PU adhesives, a decrease in the free isocyanate content, leading to slower setting time but higher shear strength values, were observed. Similarly, the thermal properties of lignin-PU adhesive were also studied, showing an increase in glass transition temperature (Tg) with increase in lignin content.

Influence of Lignin and Polymeric Diphenylmethane Diisocyante Addition on the Properties of Poly(butylene succinate)/Wood Flour Composite

Poly(butylene succinate) (PBS)/wood flour (WF) composites with different WF content were prepared by twin-screw extrusion at 160 °C. With increasing WF content, the tensile strength of the PBS/WF composite without polymeric diphenylmethane diisocyante (pMDI) decreased, while that of the composite with pMDI increased. The addition of kraft lignin (KL) deteriorated the tensile properties of the composites both with and without pMDI. The melt flow index (MFI) decreased with increasing WF content, but increased with increasing KL content. The addition of pMDI caused an increase in the melt viscosity of the PBS/WF and PBS/WF/KL composites, resulting in a decrease in the MFI. The composites had lower thermal stability than neat PBS. The exotherms of the PBS/WF (50/50) composite appeared at a higher temperature than that of the neat PBS, but the PBS/WF/KL (50/50/20) composites had similar exotherms as the neat PBS. The addition of KL caused a decrease in the crystallization rate of PBS.

The Efficiency of Biobased Carbonization Agent and Intumescent Flame Retardant on Flame Retardancy of Biopolymer Composites and Investigation of their Melt-Spinnability.

The objective of this study is to assess the efficiency of biobased carbonization agent in intumescent formulations (IFRs) to examine the flame retardant properties of polylactic acid (PLA) composites and to investigate their melt-spinnability. We used phosphorous-based halogen free flame retardant (FR) and kraft lignin (KL) as bio-based carbonization agent. After melt compounding and molding into sheets by hot pressing various fire related characteristics of IFR composites were inspected and were characterized by different characterization methods. It was fascinating to discover that the introduction of 5–20 wt% FR increased the limiting oxygen index (LOI) of PLA composites from 20.1% to 23.2–33.5%. The addition of KL with content of 3–5 wt% further increased the LOI up to 36.6–37.8% and also endowed PLA/FR/KL composites with improved anti-dripping properties. Cone calorimetry revealed a 50% reduction in the peak heat release rate of the IFR composites in comparison to 100% PLA and confirmed the development of an intumescent char structure containing residue up to 40%. For comparative study, IFR composites containing pentaerythritol (PER) as a carbonization agent were also prepared and their FR properties were compared. IFR composites were melt spun and mechanical properties of multifilament yarns were tested. The analysis of char residues by energy dispersive X-ray spectrometry (EDS) and SEM images confirmed that PLA/FR/KL composites developed a thicker and more homogeneous char layer with better flame retardant properties confirming that the fire properties of PLA can be enhanced by using KL as a carbonization agent.

Sulfonated Kraft lignin addition in urea–formaldehyde resin

Urea–formaldehyde (UF) resins are widely used over the world as an adhesive, principally in the civil construction, but its use leads to formaldehyde emissions when exposed to higher temperatures. In this way, the aim of this study was to evaluate the partial replacement of adhesives made of UF resin by sulfonated Kraft lignin, up to 30 mass%, and study its effects on the mechanism and on the kinetic/thermodynamic parameters of the thermal degradation, as well as on the thermal stability of the UF resin through thermogravimetric analysis and using isoconversional methods. The results showed that the lignin addition to the UF resin was beneficial, as there was synergy between the materials and verification of enhancement of thermal stability. Aside from the changes in the thermal behavior, the probable reduction of the emission of formaldehyde in the second step of degradation of the UF resin was also observed. These results indicate that the lignin can be used as a potential material to partially replace the UF resin.

Potential of kraft lignin as an additive in briquette production

Abstract Lignin, a renewable product with high potential for various applications, can be recovered from kraft black liquor by precipitation in acid medium. The objective of this study was to evaluate the effect of the addition of kraft lignin to wood biomass on the properties of briquettes. Hymenolobium petraeum, Eucalyptus, and Pinus biomasses received the addition of 0, 3, 6, 9, and 12 % (w/w) of kraft lignin, and briquettes were manufactured. Wood biomasses and briquettes were characterized chemically and physically. Addition of kraft lignin positively influenced the apparent density, energy density, and mechanical resistance of briquettes. Furthermore, kraft lignin increased the calorific value of briquettes. Addition of 6 % (w/w) of kraft lignin was sufficient to improve the quality properties of briquettes, which demonstrates the great potential of kraft lignin as an additive in briquette production.

KRAFT LIGNIN AS AN ADDITIVE IN PINE AND EUCALYPTUS PARTICLE COMPOSITION FOR BRIQUETTE PRODUCTION

ABSTRACT The objective of this study was to evaluate the properties of briquettes produced with different proportions of pine and eucalyptus wood, as well as to characterize the potential of kraft lignin as an additive in the composition of briquettes for energy generation. The treatments differed from one another in the pine and eucalyptus wood particle ratios (0, 25, 50, 75 and 100%), as well as for the kraft lignin content (0, 2, 4, 6, 8, 10, and 12%). The biomasses were characterized by their physical and chemical properties, and briquette properties were evaluated according to apparent density, lower calorific value (LCV), energy density, and maximum burst load. The results showed an increase in the apparent density as the proportion of lignin and eucalyptus in the briquettes increased. The particle composition of the briquettes had a higher influence on the energy density increase compared to the addition of kraft lignin, being more significant in briquettes produced with higher proportions of eucalyptus. It was also observed that the addition of lignin increased the resistance to the rupture load, and that there was a specific value at which this resistance was higher (at 7% or 11% of lignin, depending on the proportion of particles). Additionally, the briquettes made with 100% pine achieved greater mechanical resistance. In general, kraft lignin presented good potential for use as a briquette additive, contributing to improved energy and mechanical properties.

Effect of Charcoal and Kraft-Lignin Addition on Coke Compression Strength and Reactivity

The aim of this research was to investigate the effects of charcoal and Kraft-lignin additions on the structure, cold compression strength, and reactivity of bio-cokes produced at the laboratory scale. Bio-cokes were prepared by adding charcoal and Kraft-lignin (2.5, 5.0, 7.5, and 10.0 wt %) to medium-volatile coal and coking the mixture with controlled heating rate (3.5 °C/min) up to 1200 °C. In addition, four particle sizes of charcoal were added with a 5 wt % addition rate to investigate the effect of particle size on the compression strength and reactivity. Thermogravimetric analysis was used to evaluate the pyrolysis behavior of coal and biomasses. Optical microscopy was used to investigate the interaction of coal and biomass components. It was found that by controlling the amount of charcoal and Kraft-lignin in the coal blend, the compression strength of the bio-cokes remains at an acceptable level compared to the reference coke without biomass addition. The cold compression strength of the charcoal bio-cokes was higher compared to Kraft-lignin bio-cokes. The reactivity of the bio-cokes with charcoal addition was markedly higher compared to reference coke and Kraft-lignin bio-cokes, mainly due to the differences in the physical properties of the parental biomass. By increasing the bulk density of the coal/biomass charge, the cold compression strength of the bio-cokes can be improved substantially.