Wood Fines Research Articles

Early detection of deep-seated smouldering fires in wood waste storage using ERT

Incidents of waste and biofuel fires are common at all stages of the waste recycling chain and have grave implications for business, employees, firefighters, society, and environment. An early detection of waste and biofuel fires in the smouldering stage could save precious lives, resources, and our environment. Existing fire detection methodologies e.g. handheld temperature sensors, IR cameras, gas sensors, and video and satellite-based monitoring techniques have inherent limitations to efficiently detect smouldering fires. An attempt was made to explore the potential of electrical resistivity tomography (ERT) as an alternate tool to address the problem. In the experiments an externally powered resistive wire was employed to initiate the smouldering fire inside the test material (wood pellets, wood shavings, wood fines). Time series of ERT that followed the initiation and development of smouldering were recorded using an automated monitoring instrument setup. The actual geometry of the experimental sample container and electrode setup was integrated in the 3D finite element method (FEM) model grid to perform inverse numerical modelling (inversion) and to develop resistivity tomographic images. The study shows a sharp increase in ratio of resistivity (R/Ro ≥ 50 %) in the test material in the region of smouldering hotspot and demonstrates the potential use of ERT technique for the detection of smouldering hotspots in silos and pile storage of organic material such as wood-based fuels, wood waste, coal, municipal solid waste (MSW), recyclables etc. More research is however required for enabling the use of this technique at the practical scale for different storage conditions.

Physical and mechanical characteristics of composite briquette from coal and pretreated wood fines

Melina wood torrefied at 260 °C for 60 min was agglomerated with lean grade coal fines into composite briquettes using pitch as binder. Torrefied biomass (3%–20%) and coal fines (80%–97%) were blended together to produce the composite briquettes under a hydraulic press (28 MPa). The briquettes were cured at 300 °C. Density, water resistance, drop to fracture, impact resistance, and cold crushing strength were evaluated for the composite briquettes. The proximate, ultimate, and calorific value analyses were carried out according to different ASTM standards. Microstructural studies were carried out using scanning electron microscope and electron probe microanalyzer equipped with energy dispersive x-ray. Fourier Transform Infrared Spectrophotometer (FTIR) was used to obtain the functional groups in the raw materials and briquettes. The density of the composite briquettes ranged from 0.92 to 1.31 g/cm3 after curing. Briquettes with < 10% torrefied biomass has good water resistance index (> 95%). The highest cold crushing strength of 4 MPa was obtained for briquettes produced from 97% coal fines and 3% torrefied biomass. The highest drop to fracture (54 times/2 m) and impact resistance index (1350) were obtained for the sample produced from 97% coal and 3% torrefied biomass. The fixed and elemental carbons of the briquettes showed a mild improvement compared to the raw coal. The peaks from FTIR spectra for the briquettes shows the presence of aromatic C=C bonds and phenolic OH group. The composite briquettes with up to 20% torrefied biomass can all be useful as fuel for various applications.

On the strength improvement of lightweight fibre networks by polymers, fibrils and fines

Novel lightweight cellulose fibre materials containing various strength enhancing polymeric and fibrillar components were formed with the help of foam technology. Increasing inter-fibre bond strength and local material density was attempted with unique lignin-containing wood fines (V-fines), cellulose microfibrils (CMF), TEMPO-oxidized cellulose nanofibrils (TCNF), and macromolecules such as cationic starch, polyvinyl alcohol (PVA), and locust bean gum (LBG). The investigated fibres included both long hemp bast fibres and northern bleached softwood Kraft pulp. In the low-density range of 38–52 kg/m3, the compression stress and modulus were highly sensitive to inter-fibre bond properties, the multi-scale features of the fibre network, and the foaming agent employed. Still, the compression-stress behaviour in most cases approached the same theoretical curve, derived earlier by using a mean-field theory to describe the deformation behaviour. At 10% addition level of fine components, the specific compression stress and compression modulus increased in the order of V-fines < CMF < TCNF. A tremendous increase in the compression modulus was obtained with LBG, leading to a material surface that was very hard. In general, the foams made with PVA, which acts both as foaming agent and reinforcing macromolecule, led to better strength than what was obtained with a typical anionic sodium dodecyl sulphate surfactant. Strength could be also improved by refining the softwood pulp.Graphic abstract

Pilot-Scaled Fast-Pyrolysis Conversion of Eucalyptus Wood Fines into Products: Discussion Toward Possible Applications in Biofuels, Materials, and Precursors

Based on a circular bioeconomy strategy, eucalypt wood fines rejected from a Kraft pulp line were used as starting material in a pilot-scaled fast-pyrolysis process. The bio-oil and its coproducts were characterized regarding their physical, chemical, and thermal aspects. We put in perspective their properties to bring forward considerations for applications on biofuels, materials, and precursors. The yields of the pilot-scaled fast-pyrolysis process reached interesting values even if compared with optimized laboratory conditions. The results indicated the highest heating values (22–27 MJ/kg) for bio-oil, char, and crust material. The higher water content of aqueous extract had a negative effect for its application as fuel. The lignin/carbohydrate ratio for the bio-oil (2.82) and aqueous extract (0.53) identified a higher concentration of lignin-derived compounds in the first, mainly syringyl units. Bio-oil and aqueous extract presented chemical compounds with many functionalities, such as syringaldehyde and levoglucosan, expanding their potential application for higher value-added products besides energy.

The sticky behavior of pulp and paper mill biosludge during drying

Pulp and paper mill biosludge becomes sticky after being dried to a certain solids content. As biosludge becomes sticky, it agglomerates and adheres to the heat transfer surfaces of the dryer. This undesirable property can lower the dryer efficiency and cause the drying equipment to fail. A systematic study was conducted to examine the sticky behavior of biosludge. The stickiness was evaluated by measuring the adhesive force between a sludge cake and a stainless steel substrate, and the cohesive force between a sludge cake and a sludge substrate. The results show that: i) both adhesive and cohesive forces increase markedly as the solids content increases, reaching a maximum value at about 13% solids, and then decrease steadily at a higher solids content; ii) cohesive force is stronger than adhesive force, implying that biosludge tends to agglomerate rather than adhere to smooth equipment surfaces; and iii) mixing wood fines or fly ash from a biomass boiler reduces the stickiness of the mixture. These findings may help mills improve the thermal efficiency of biosludge dryers and to turn biosludge into a more attractive fuel for burning in biomass boilers.

The evaluation of the potential ecotoxicity of pyroligneous acid obtained from fast pyrolysis

Pyroligneous acid (PA) is a by-product of bio-oil, which is obtained by pyrolysis of the wood. This product has been tested for use in several areas, such as agriculture, as a promising green herbicide; however, there are few scientific data regarding its environmental impacts. For this study, an ecotoxicity testing battery, composed of Daphnia magna acute toxicity test, Allium cepa test and in vitro Comet assay with the rainbow trout gonad-2 cell fish line (RTG-2) were used to evaluate the acute toxicity and genotoxicity of PA obtained from fast pyrolysis of eucalyptus wood fines. The PA presented acute toxicity to D. magna (microcrustacea) with EC50 of 26.12 mg/L, and inhibited the seed germination (EC50 5.556 g/L) and root development (EC50 3.436 g/L) of A. cepa (higher plant). No signs of genotoxicity (chromosomal aberrations and micronuclei in A. cepa and primary DNA lesions in RTG-2 cells) were detected to this product. The acute toxicity and absence of genotoxicity may relate to the molecules found in the PA, being the phenolic fraction the key chemical candidate responsible for the toxicity observed. In addition, daphnids seem to be more sensitivity to the toxicity of PA than higher plants based on their EC50 values. This first ecotoxicological evaluation of PA from fast pyrolysis pointed out the need of determining environmental exposure limits to promote the safer agriculture use of this product, avoiding impacts to living organisms.

PEG Acoustic Levitation Treatment for Historic Wood Preservation Investigated by Means of FTIR Spectroscopy and Wavelets

Background: The combination of Fourier Transform InfraRed and levitation techniques, both on levitated water mixtures of Polyethylene Glycols (PEG)s and on wood finds, allows to follow the polymeric drying process as a function of time through the O-H and C-H stretching contributions and to investigate the wood thermal response. Objective: The aim of this paper is to report the FTIR investigations on wood fines, extracted from a 700’ dated wooden crucifix. Methods: At first, different acoustically levitated Polyethylene Glycol (PEG) aqueous solutions were investigated by FTIR in order to characterize the levitation induced dehydration process; then the wood fines, after having been treated by immerging them into the PEG aqueous solutions, were acoustically levitated and investigated; finally the treated fines were again studied by IR spectroscopy through a thermic cycle in the 25 ÷ 350 °C temperature range. Levitation technique furnishes an innovative approach to sample treatment allowing, in the case of solutions, to obtain highly concentrated mixtures starting from diluted solutions while, in the case of wood find treatments, to increase the polymer solution penetration within the wood matrix. Results: It clearly emerges that, in the PEG200/PEG600 comparison, the lighter polymer shows a higher effectiveness in terms of thermal restraint. Conclusion: Acoustic levitation, in combination with IR spectroscopy, reveals to be a very powerful technique in many applications concerning wood preservation and conservation. It clearly emerges that, in the comparison with PEG600, PEG200 shows a higher effectiveness in terms of thermal restraint.

Cascading use of textile waste for the advancement of fibre reinforced composites for building applications

The Textile industry is the second most polluting sector in the world, accounting for the 10% of the total world's carbon emissions. Contributes to a complex, profuse, and fast generating post-consumer waste stream of unprecedented rate; estimated of 92 million tons in 2015. The relevance and key advantage of this end-of-life waste stream relies in the latent potential of a material blend rich in complex polymers and bio-polymers, which the traditional waste management protocol of incineration or landfill disposal has become obsolete, due to its major detrimental environmental consequences. This research targets the recovery of assorted end-of-life textiles with the emphasis on promoting multi-stage cascading use of mixed fibre bulk, as a low-carbon alternative feedstock, for the advancement of textile fibre reinforced composite (TFRC) materials, for building applications. For this purpose, a series of five novel multiphase blends were engineered. A homogeneous micro-fibrillated randomly oriented fine fleece constituted by polymers and bio-polymers mixture of thermoplastics (i.e. polyester, acrylic), lingo-cellulosic (i.e. cotton), and protein polymers (i.e. wool) were studied as the main filler phase. The effect of residual fine wood fibres was examined as secondary filler; and fibrillated polypropylene textile waste, was incorporated as the thermoplastic matrix phase, optimizing the filler/matrix interfacial adhesion with maleic anhydride grafted polypropylene coupling agent as 6 wt%. The sheet panel prototypes were manufactured under isothermal hot-compression moulded in a steel die. The material properties for mechanical performance, interfacial adhesion, moisture absorption, fire resistance, surface roughness and microstructural characteristics are reported. The experimental results indicated the series of innovative TFRCs presented optimal performance for moisture resistance, as well as for load-bearing and non-load bearing applications, in comparison to standard wood-based particleboards. The highest performance for mechanical strength (34.9 MPa) and low-moisture absorption (2.4%) was achieved by the specimens formulated with polypropylene textile matrix phase as 40 wt%. Highest flame retardant property was achieved by the prototype with wood fines as secondary filler.These results confirm an effective compatibility between diverse fibre wastes as composite blend mixture for TFRCs, providing a non-toxic low-carbon alternative material for high-end building applications.

Improving Compression Recovery of Foam-formed Fiber Materials

Foam technology enables the preparation of new fiber-based materials with reduced density and improved mechanical performances. By utilizing multi-scale structural features of the formed fiber network, it is possible to enhance the elasticity of lightweight cellulose materials under compressive loads. Sufficient strength is achieved by optimally combining fibers and fines of different length-scales. Elasticity is improved by adding polymers that accumulate at fiber joints, which help the network structure to recover after compression. This concept was demonstrated using natural rubber as the polymer additive. For a model network of viscose fibers and wood fines, the immediate elastic recovery after 70% compression varied from 60% to 80% from the initial thickness. This was followed by creep recovery, which reached 86% to 88% recovery within a few seconds in cross-linked samples. After 18 h, the creep recovery in those samples was almost complete at up to 97%. A similar improvement was seen for low-density materials formed with chemi-thermomechanical fibers. The formed structure and elastic properties were sensitive not only to the raw materials, but also to the elastomer stiffness and foam properties. The improved strain recovery makes the developed cellulose materials suitable for various applications, such as padding for furniture, panels, mattresses, and insulation materials.

Modeling of torrefaction of small biomass particles

ABSTRACTA simple single-step kinetic model consisting of two parallel reactions is proposed for torrefaction of small biomass particles. The model is validated against experimental data on torrefaction of poplar wood fines. Comparison of experimental data and model prediction shows that the results predicted by the proposed simplified model are as accurate as those from the models of Di Blasi and Lanzetta (1997) and Rousset et al. (2006) which involve larger numbers of model parameters – eight and sixteen, respectively – compared to four in the proposed model. This makes it suitable for incorporation into the overall reactor model. At 493 and 553 K, the relative mean errors are found to be 0.056, 0.080, 0.051 and 0.050, 0.100, 0.048 for the proposed model, Rousset et al.’s (2006) model and Blasi and Lanzetta's (1997) model, respectively. The effect of particle size, temperature and residence time on torrefaction of biomass is investigated. A transformation of rate-controlling regime from kinetic to heat transfer is identified with an increase in particle size and temperature. Sensitivity analysis shows that the dimensionless groups such as pyrolysis number, dimensionless heat of reaction and dimensionless activation energy have significant influence on the particle temperature and torrefaction behaviour.

Drying characteristics of biosludge from pulp and paper mills

Handling and disposal of biosludge has been a persistent problem for many pulp and paper mills primarily because of the material’s high moisture content and poor dewatering and drying characteristics. Most biosludge is landfilled or incinerated, and some is used as a soil amendment. To incinerate biosludge, the mills mix it with primary sludge, mechanically dewater the mixture to 15%–30% solids, and burn it with hog fuel in biomass boilers. For biosludge to burn effectively, however, it must be dewatered or dried to at least 30%–35% solids. A systematic study was conducted to examine the drying characteristics of biosludge collected from pulp and paper mills at various temperatures using a thermogravimetric dryer. The drying behavior of the tested biosludges was similar, adding fillers such as wood fines and biomass boiler fly ash to biosludge up to 30 wt% did not significantly affect the drying rate, higher organic content might make biosludge more difficult to dry, and increasing drying temperature significantly increases the drying rate as expected.

Bio-oil from a fast pyrolysis pilot plant as antifungal and hydrophobic agent for wood preservation

Residual wood fines were used as raw material to produce fast pyrolysis bio-oil in a pilot plant for further utilization as antifungal and hydrophobic agent for wood protection. Phenolic compounds derived from lignin mostly composed the obtained bio-oil. Pinewood was impregnated with natural and diluted bio-oil aiming three different final loads. Scanning electron microscopy images revealed that the internal surface of the tracheids was coated by the bio-oil. Fourier-transformed infrared analysis showed no chemical reactions between wood and bio-oil, while thermogravimetric studies stated changes in the thermal stability of the impregnated pinewood. The bio-oil impregnation proved to be effective to decrease the water absorption and wettability of the pinewood. In addition, the bio-oil impregnated pinewood with low load (7.95%) had decay resistance improved by 2.6 and 4.5 times against T. versicolor and G. trabeum fungi, respectively, meanwhile the highest bio-oil loading (81.3%) inside pinewood caused the mortality of the whole fungal colony in the first days of test.

Biological Durability of Injection Moulded Wood Plastic Composite Boards

The steadily growth of Wood Plastic Composite (WPC) in exterior applications resulted a need to understand their durability. In Malaysia, the durability of WPC is not only affected by mold and decay fungi as biodegradation agents but also due the termites attack. Therefore, this study was carried out to investigate the durability of WPC produced from different wood fine loadings (60, 65 and 70%) and MAPP (1, 2, 3 and 4%) concentration. The aim of this study is to determine the optimum WPC formulation associate with higher durability against biodegradation agents. Commercial polypropylene, wood fines and coupling agent premixed in dumper mixer for 30 min prior to extrusion process at temperature of 190°C using 110 mm counter-rotating twin-screw extruder. The premixed raw materials were then subjected to injection moulded using 40 ton press moulding machine and pressed into size of 30 mmx30 mm and 3 mm thick board. Biological durability tests were carried out according to ASTM D4445 for mold, ASTM method D 2017 for decay fungi and ASTM D 3345 for termites. From the result, 70% wood fine loading showed significantly lower durability due to the insufficient encapsulation of wood fine with polymer matrix. Higher percentage of coupling agent (MAPP) used in the WPC boards will provide higher durability of WPC. Conclusively, the optimum formulation for WPC i.e., 4% MAPP and 60% wood fine loading gave the highest protection against mold, decay fungi and termites.

Backward-mode photoacoustic transducer for sensing optical scattering and ultrasonic attenuation: determining fraction consistencies in pulp suspensions

An innovative backward-mode photoacoustic transducer was developed, consisting of an optical fibre, a composite absorber, piezoelectric film and high impedance preamplifier. By receiving scattering light from a turbid suspension, the transducer produces a photoacoustic source in it. This source emits two photoacoustic waves travelling in opposite directions. The waves' amplitudes relate to the optical scattering properties of the suspension, and the echo of a wave returning from the suspension carries information of acoustic attenuation. By assessing the optical scattering and acoustic attenuation, fraction consistencies in a two-fractional suspension can be determined if one fraction dominantly scatters light and the other mainly attenuates ultrasound. This technique is used in this paper to investigate paper pulp suspensions. Pulp consists of wood celluloses and wood fines (or extra-added fillers in some cases), where cellulose lengths range from a few sub-millimetres to millimetres and fines/filler sizes are a few tens of micrometres or smaller. Due to their different size and shape, celluloses and fines (or fillers) have different optical scattering and acoustic attenuation properties. Experimental results showed that the transducer can measure pulp consistency with good linearity at least in the range from 0.5% to 3%, and that it can distinguish pulp cellulose from fines or fillers (TiO2 particles). Needless to say, this technique is also suitable for determining other suspensions in the food, pharmaceutical and mineral industries.

Modelling of pyrolysis of large wood particles

A fully transient mathematical model has been developed to describe the pyrolysis of large biomass particles. The kinetic model consists of both primary and secondary reactions. The heat transfer model includes conductive and internal convection within the particle and convective and radiative heat transfer between the external surface and the bulk. An implicit Finite Volume Method (FVM) with Tridiagonal Matrix Algorithm (TDMA) is employed to solve the energy conservation equation. Experimental investigations are carried out for wood fines and large wood cylinder and sphere in an electrically heated furnace under inert atmosphere. The model predictions for temperature and mass loss histories are in excellent agreement with experimental results. The effect of internal convection and particle shrinkage on pyrolysis behaviour is investigated and found to be significant. Finally, simulation studies are carried out to analyze the effect of bulk temperature and particle size on total pyrolysis time and the final yield of char.

Modelling and experimental studies on pyrolysis of biomass particles

A simple mathematical model has been developed to describe the pyrolysis of a single biomass particle. A fully transient analysis involving a kinetic model coupled with heat transfer model has been presented. The kinetic model consists of both primary and secondary pyrolysis reactions while the heat transfer model includes diffusive, convective and radiative modes of heat transfer. Fourth-order Runge–Kutta–Gill method is used to solve the kinetic model, while implicit Finite Volume Method (FVM) with Tri-Diagonal Matrix Algorithm (TDMA) is employed to solve the heat transfer model. The kinetic parameters and heat of reaction are estimated by Levenberg Marquardt nonlinear optimization technique. A general-purpose FORTRAN program is developed to solve the model equations and estimation of parameters. Experimental investigations are carried out for wood fines and cylinders in an electrically heated reactor. The model predictions for temperature and mass loss histories are in excellent agreement with the experimental results. The model is also validated with published experimental results. Finally, the effects of temperature and particle size on pyrolysis time and yield of final char have been analyzed with model simulation.

The effect of pulping, bleaching, and refining operations on the electrokinetic properties of wood fines

Article The effect of pulping, bleaching, and refining operations on the electrokinetic properties of wood fines was published on August 1, 1990 in the journal Nordic Pulp & Paper Research Journal (volume 5, issue 3).

DEVELOPMENT AND TESTING OF THE INTERNAL ROTARY COMPRESSION PRESS

Abstract The Internal Rotary Compression (IRC) press is based on a concept patented by Anderson Metal Industries, Inc. (AMI) in which one dewatering roll is configured internally and eccentrically to the other. The press can simultaneously apply severe mechanical compression and shear forces to the material being dewatered. This design permits a larger no-slip entry volume for dewatering than that obtainable from conventional external roll presses of the same size. Bench-scale tests of the IRC press have been conducted at IGT with several different materials including peat, wood fines, and paper waste. Significant dewatering was achieved for each material tested. Dewatered peat moisture contents in the range of 40 to 50 weight percent have been achieved. These results represent a significant improvement over those achievable by conventional continuous presses. Tests have also been conducted in an IRC prototype press designed to produce 45 kg/h of dewatered peat. Tests with moderately and slightly decompos...