Torrefied Samples Research Articles

Torrefaction and hydrothermal carbonization of waste from the paper industry: Effects of atmosphere choice and pretreatment with natural acidic reagent on fuel properties

The hydrothermal carbonization (HTC) and torrefaction of paper sludges and biological sludges from the paper industry were investigated and the effect of pretreatment of the samples with alcoholic vinegar was evaluated. The HTC was performed at two different reaction times, while the torrefaction took place at two different temperatures and two atmospheres. The gas analysis showed that the optimal torrefaction time for the N2 atmosphere can be determined by observing the CO2 content in the gas phase, which is not possible for the CO2 atmosphere. The TGA analysis showed that the choice of atmosphere influences further combustion, with samples torrefied at lower temperatures being more sensitive to it. The carbon (C) content in the thermally treated samples increases from 39.85 to 48.06 wt% for biological sludge and from 40.02 to 60.21 wt% for paper sludge. The H/C and O/C ratios decrease and approach the values of conventional fuels. The fuel ratio is higher for the torrefied samples. The higher heating value (HHV) increased from 17.4 to 21.4 MJ/kg for biological sludge and from 16.2 to 22.4 MJ/kg for paper sludge. Higher temperature and longer treatment time led to products with a higher HHV and a higher energy density. The highest energy yields were achieved during torrefaction at 250 °C, regardless of the atmosphere, with temperature and type of material having the greatest influence. Acidification of the samples or acidic media in the HTC affects the properties of the products by increasing the C content and HHV and affecting combustion.

Combustion Behaviors, Kinetics, and Thermodynamics of Naturally Decomposed and Torrefied Northern Red Oak (Quercus rubra) Forest Logging Residue

Torrefaction and combustion have been applied to naturally decomposed red oak logging residues. The results indicated that four-year natural decomposition would lower the energy density of red oak from 20.14 to 18.85 MJ/kg. Torrefaction reduced the O/C and H/C ratios but improved the energy yield values. Two combustion stages were observed for all samples, and no hemicellulose derivative thermogravimetric peak appeared for torrefied samples. The differential scanning calorimetry exothermic heat flow increased after torrefaction. In addition, the Kissinger–Akahira–Sunose average activation energy of untorrefied samples decreased in the first stage (from 157.77 to 149.52 KJ/mol), while it increased in the second stage (from 131.32 to 181.83 KJ/mol). The ∆H, ∆G, and ∆S values of all samples decreased in the first stage, while they increased when the conversion rate was greater than 0.5 for torrefied samples. These findings can aid in a better understanding of the fuel performance of torrefied and untorrefied naturally decomposed red oak logging residues.

Enhancing fuel characteristics and combustion performance of cellulose-rich straws through CO2-assisted torrefaction

Cellulose-rich straws of corn and rice were torrefied under carbon dioxide, and the fuel characteristics and combustion performance of the obtained biochar were investigated. A high severity resulted in surface collapse, greater pore volume, elimination of oxygen, elevated calorific value, and improved hydrophobicity in biochar. Following carbon dioxide torrefaction, the cellulose content in solid biochar experienced a slight decrease when the temperature was raised to 220 °C for longer residence durations. At 300 °C, the cellulose content in the biochar was nearly eliminated, while the relative proportion of non-sugar organic matter in corn stover and rice straw increased to 87.40 % and 77.27 %, respectively. The maximum calorific values for biochar from corn and rice straws were 22.38 ± 0.03 MJ/kg and 18.72 ± 0.05 MJ/kg. The comprehensive combustion indexes of rice and corn straw samples decreased to 1.06 × 10−7 and 1.31 × 10−7 after torrefaction at 300 °C, respectively. In addition, the initial decomposition temperatures increased by 38 °C and 45 °C, while the ultimate combustion temperatures rose by 13 °C and 16 °C for corn and rice straws, respectively. These results imply an extended combustion timeframe for the torrefied samples.

Optimization of waste cork powder torrefaction to improve biofuel parameters and storage properties

Waste cork torrefaction was optimized in order to improve the properties of this material for its application as biofuel. A two-level factorial design involving three factors -torrefaction temperature, torrefaction time and heating rate- was proposed with two-responses -mass yield (MY) and high heating value (HHV)-. Factorial design results revealed that torrefaction time and especially temperature were the most influential factors. Using simultaneous optimization of the two variables MY and HHV, and giving them two different weights, two different sets of optimum conditions were obtained. The first one (246 ºC, 60 min and 5 ºC/min) led to a biofuel with similar HHV as the raw material, therefore it did not give any benefit in terms of biofuel upgrading. The second one (275 ºC, 60 min and 5 ºC/min) gave a biofuel with 10% more energy density than the raw material, which allowed to classify this biofuel as lignite. Both torrefied samples showed significant increase in hydrophobic character. Finally, ATR-FTIR results revealed the occurrence of carbonization reactions during torrefaction.

Effect of torrefaction pretreatment on combustion behaviour of different agricultural wastes

In this study, which was carried out to investigate the effect of the torrefaction process on the combustion behaviour of agricultural wastes, almond hulls and shells, olive seeds and corn stalks were used. The samples, dried in a laboratory atmosphere, were torrified at 300 5ºC for 41 minutes. The change in fuel properties was determined by making proximate analyses of the solid product obtained after the process and compared with the raw sample. The effects of the torrefaction process on the combustion behaviour of agricultural wastes of different structures were investigated by burning the 1 0.15 g weighted raw and torrefied samples at 700ºC furnace initial temperature in a fixed bed system. Biochars containing higher fixed carbon were obtained with the torrefaction process applied to agricultural waste, and it was determined that this caused biochars to burn more efficiently and for a longer time than raw biomass. As a result, it was determined that biochar with better properties was produced by the torrefaction process applied to agricultural wastes and it was suitable for burning in solid fuel combustion systems. Thus, biochar obtained will both contribute to the country's economy and add value to agricultural wastes that cause problems during storage, transportation, loading into the burning system, and combustion.

Improving biomass fuel obtained from Brazil nut residues via torrefaction: A case of kinetic and thermodynamic study

The residues of Brazil nuts (Bertholletia excelsa) were evaluated, in their natural state and in torrefied form, for their energy potential after pyrolysis. Samples of shells (BNS) and husks (BNH) were torrefied at 220, 260 and 300 ºC for 30 and 60 min, and were characterized for their chemical and energetic composition. It was also determined which samples showed, simultaneously, the lowest hemicellulose content and the highest cellulose content after torrefaction via analysis of the decomposition profile at 10 ºC/min under pyrolysis. The evolution of gases such as H2O, CO2 and/or C3H8, and CH4 was observed by simulated pyrolysis on a microscale in a thermogravimetric analyzer coupled to a mass spectrometer (TGA-MS). In addition, the kinetics of the pyrolysis of untorrefied and torrefied samples were evaluated using the Flynn-Wall-Ozawa (FWO) and Vyazovkin (VYZ) models in order to obtain the activation energy, pre-exponential factor and thermodynamic parameters. The predominant reaction mechanism was determined by Criado Master-plot method. The mean value of the activation energies ranged from 132.24 to 134.95 kJ/mol for BNS, from 135.53 to 138.47 kJ/mol for ST263, from 149.10 to 150.96 kJ/mol for BNH and from 145.83 to 148.14 kJ/mol for HT263. It was found that D2 and D4 diffusion mechanisms are prevalent in the decomposition of untorrefied samples, while torrefied samples were better adjusted to the F1/A2/A3/A4 overlapping nucleation models. High pre-exponential factor values indicated the presence of multiple intermolecular collisional reactions. The thermodynamic parameters evaluated, as well as the variations in enthalpy, Gibbs free energy and entropy, indicated that the evaluated process is endothermic, though requires little energy. As a whole, in view of the optimized parameters and elevation of the thermal stability of the material, the results demonstrate good potential for the use of Brazil nut shells and husks torrefied at 260 ºC for 30 min as biochar. In addition, pyrolyzed Brazil nut residues also have great potential in the production of bio-oil and biogas, in view of the high content of volatile matter released during the decomposition of the hemicellulose and lignin.

Pyrolysis Characteristics and Determination of Kinetic and Thermodynamic Parameters of Raw and Torrefied Chinese Fir.

Torrefaction influences the structural and physicochemical properties of biomass, thus further altering its thermal degradation behavior. In this study, the pyrolysis characteristics, reaction kinetics, and thermodynamic parameters of raw and torrefied Chinese fir (CF) were investigated. The torrefaction was conducted at 220 °C (mild) and 280 °C (severe), the pyrolysis was performed from ambient temperature to 600 °C, and four different heating rates (i.e., 5, 15, 25, and 35 °C/min) were adopted. The activation energy for pyrolysis was estimated by adopting three isoconversional methods. The master-plot method was employed to analyze the reaction mechanism. Furthermore, thermodynamic parameters, i.e., the enthalpy change (ΔH), Gibbs free energy change (ΔG), and entropy change (ΔS), were calculated. The average activation energy increased with the torrefaction temperature, whose values estimated by using different methods ranged from 88.57 to 97.70, from 121.04 to 126.35, and from 167.51 to 179.74 kJ/mol for raw, mildly, and severely torrefied CF samples, respectively. A compensation effect between the activation energy and pre-exponential factor was observed for all samples. The degradation process was characterized as endothermic, involving the formation of activated complexes and requiring extra energy for torrefied samples.

Effect of torrefaction on yield, reactivity and physicochemical properties of pyrolyzed char from three major biomass constituents

Torrefaction is an efficient pretreatment technology for large-scale and high-value utilization of biomass fuel. To understand the effects of torrefaction pretreatment on the physicochemical characteristics of the pyrolyzed char from the three major constituents of lignocellulosic biomass (cellulose, xylan-representative of hemicelluloses, and lignin), torrefied samples were produced at 200, 260, 320, and 380 ℃, and then pyrolyzed at 1028 ℃ with a heating rate of 65 ℃/s and 0.25 ℃/s, respectively. The experimental results demonstrate that the torrefaction temperature strongly influences the pyrolyzed char’s yields, oxidative reactivities, and physicochemical structure. The sensitivity of the accumulated char yield and char reactivity to the torrefaction temperature differed with varied constituents. Accurate modeling of accumulated char yield is achieved through a weighted summative law, showing a decreasing deviation from 2.4 wt% to 0.6 wt% as torrefaction temperatures increase. Raman spectra indicate that there is a strong correlation between the relative amount of small and large aromatic rings and the accumulated char yield of torrefied samples, with the determination coefficient R2 of 0.98, 0.88, and 0.77 for cellulose, xylan, and lignin, respectively.

Development of a Biomass Component Prediction Model Based on Elemental and Proximate Analyses

Emerging global environmental pollution issues have caused a reduction in coal utilization, leading to an increased research focus on biomass use as an alternative. However, due to the low heat values of biomass, studies in this field are still in progress. Biomass primarily comprises cellulose, hemicellulose, and lignin. To determine the composition of these three components, the measurement methods recommended by TAPPI (Technical Association of the Pulp and Paper Industry) and NREL (National Renewable Energy Laboratory) are typically employed involving equipment such as HPLC. However, these methods are time consuming. In this study, we proposed a model for predicting cellulose, hemicellulose, and lignin contents based on elemental and industrial analyses. A dataset comprising 174 samples was used to develop this model. This was validated using 25 additional samples. The R2P values for cellulose, hemicellulose, and lignin were 0.6104–0.6362, 0.4803–0.5112, and 0.7247–0.7914, respectively; however, the R2CV values obtained from the validation results were 0.7387–0.7837, 0.3280–0.4004, and 0.7427–0.7757, respectively. The optimal models selected for cellulose, lignin, and hemicellulose were C1, L2, and 100-(C1-L2) or H2, respectively. Our predictions for woody and herbaceous biomass, including torrefied samples, should be applied with caution to other biomass types due to the potential accuracy limitations. To enhance the prediction accuracy, future research should broaden the range of biomass types considered and gather more data specifically related to woody and herbaceous biomass.

The Evaluation of Torrefaction Efficiency for Lignocellulosic Materials Combined with Mixed Solid Wastes

The paper presents the results of research aimed at evaluating the possibility of using selected biomass wastes to produce solid biofuels. In this work, the thermochemical properties of two lignocellulosic biomasses, namely, miscantshus (Miscanthus × Giganteus) and hops (Humulus lupulus), and non-lignocellulosic biomass, namely, municipal solid waste, and their mixtures (micanthus + municipal solid waste and hops + municipal solid waste) were studied using the torrefaction process as the main method for investigation. The effects of various torrefaction temperatures (250, 300, and 350 °C) and times (30 and 60 min) were evaluated. Proximate and ultimate analyses were performed on the torrefied samples. The following can be stated: as the torrefaction temperature and time increased, mass and energy yields decreased while the higher heating values (HHVs) and fuel ratios (FRs) increased, together with carbon contents (C). In addition, energy on return investment (EROI) was studied; the maximum EROI of 28 was achieved for MSW biochar at 250 °C for 30 min. The results of studying greenhouse gas emissions (GHGs) showed a reduction of around 88% when using torrefied biochar as a substitute for coal. In sum, this study shows that torrefaction pre-treatment can improve the physicochemical properties of raw biomasses to a level comparable with coal, and could be helpful in better understanding the conversion of those biomasses into a valuable, solid biofuel.

Understanding the compositional changes of organic matter in torrefied olive mill pomace compost using infrared spectroscopy and chemometrics

Composting olive mill pomace (OMP), the major by-product of the olive oil industry, is an attractive waste management practice in the context of sustainable food production. Thermal treatment of compost at mild temperatures (torrefaction) can aid to improve its characteristics as a soil amendment. This study aims to understand the chemical changes occurring during torrefaction of olive mill pomace-based (OMP) compost, as well as to evaluate the treatment effects on compost at different stages of maturation. Here, treatments at different temperatures (175, 225, and 275 °C) and duration (from 1 to 5 h) have been employed to obtain a sort of torrefied samples. In general, the H/C and O/C atomic ratios of compost samples decreased with torrefaction temperatures, which suggests an incipient coalification of the organic matter. Furthermore, the results showed that a combination of FT-NIR and FT-MIR spectroscopy using a low-level data fusion strategy is very sensitive to the molecular changes occurring both in the composting process and during heating. Principal Component Analysis (PCA) of the merged spectra revealed that the changes at 175 °C are mainly the loss of water (O–H contributions at 3300 and 5169 cm−1) together with the degradation of proteins (observed in the decrease of amide I and II characteristic bands). Furthermore, the samples heated at this temperature can still be differentiated by their initial maturation stage. On the other hand, thermochemical changes occurring at higher temperatures are more intense and make the samples more alike, independently of the composting time. When heating above 225 °C, the loss of O–H happens together with the decrease of aliphatic moieties, reflected in the bands 2920 and 2850 cm−1 (FT-MIR) and 4258, 4323, 5665, and 5781 cm−1 (FT-MIR). This can be attributed to the thermal degradation of cellulosic materials and, additionally, to the degradation of the residual oil in the case of poorly composted samples. Heated samples are characterized by the presence of carbonyl groups (1709 cm−1) and humic-like complex and polymerized aromatic structures (1579 cm−1). Since the characteristics of the torrefied compost at 275 °C are very similar regardless of the initial maturation stage, torrefaction may be a very interesting way to reduce the composting time of olive mill pomace to obtain a high-quality organic amendment for soil application.

Kinetic Mechanisms and Emissions Investigation of Torrefied Pine Sawdust Utilized as Solid Fuel by Isothermal and Non-Isothermal Experiments.

This study comprehensively investigated the utilization of torrefied pine sawdust (PS) as solid fuels, involving the characterization of torrefied PS properties, the investigation of combustion behaviors and kinetic mechanisms by non-isothermal experiments, and the evaluation of emissions during isothermal experiments. Results show that torrefaction significantly improved the quality of the solids. The upgradation of torrefied PS properties then further enhanced its combustion performance. For the kinetics mechanisms, degradation mechanisms and diffusion mechanisms were respectively determined for the volatile combustion and the char combustion by using both Coats-Redfern (CR) and Freeman-Carroll (FC) methods. Further, after torrefaction, the emission of NO for volatile combustion reduced while it increased for char combustion. An inverse relationship was found between the conversion of fuel-N to NO and the nitrogen content in the torrefied samples. This study provided comprehensive insights for considering torrefaction as a pretreatment technique for PS utilization as a solid fuel.

The combined effect of solar assisted torrefaction and pyrolysis on the production of valuable chemicals obtained from water hyacinth biomass

In this study, both the torrefaction and pyrolysis of water hyacinth biomass samples were accomplished by using concentrated solar radiation. The first attempt was to prepare torrefied samples and then used those in the following pyrolysis process. The aim of preparing pretreated torrefied samples was to reduce moisture from the feedstock and make it perfect for the pyrolysis process besides improving product quality. Three different torrefied samples were prepared by pretreating at 200, 250, and 300℃. The pyrolysis operation was done by maintaining a reactor temperature of 440±10℃. Torrefaction severity had a greater influence on char yields. The char yield was found to be 27.4 wt.% for the non-torrefied sample (ST-Raw) while 42.3, 51.2, and 59.4 wt.% for torrefied samples of ST-200, ST-250, and ST-300 respectively. However, an increase in torrefaction temperature had negative consequences on bio-oil and syngas yields. The acidity of the bio-oils was greatly reduced with an increase in torrefaction temperature. The lowest acid content in ST-300 bio-oil sample was confirmed by the FTIR, and GC-MS analysis. This ensures that the torrefied bio-oils are more non-corrosive than non-torrefied bio-oils. The heating values of ST-300 bio-oils were found to be about 75% of diesel fuel. The char obtained in the pyrolysis process for all torrefied samples was of high quality and graded as peat or brown coal. Considering the characteristics of biomass, products, and method used in this study, solar pyrolysis is a promising technique to produce high-quality chemical intermediates. • The combined effect of solar torrefaction and pyrolysis on the products was investigated. • Torrefaction severity significantly increased char (27.4 to 59.4 wt.%) content. • Torrefaction severity improved the product's heating values. • Torrefaction reduced the acidity of bio-oils obtained in solar pyrolysis.

In situ formation of fatty acid methyl esters via thermally assisted methylation by lignin during torrefaction of oil palm biomass

Torrefaction of oil palm empty fruit bunch (EFB) biomass was performed at six temperatures between 210 and 360 °C. The composition of the evolved and trapped condensates was analyzed by GC/MS and the torrefied biomass samples were characterized by pyrolysis-GC/MS (Py-GC/MS). The analyses showed that the thermal treatment of the biomass produced significant amounts of fatty acid methyl esters (FAMEs). The in situ FAME formation was explained by the reaction of the lipid and lignin contents of the biomass; i.e., the fatty acid moieties of triglycerides were methylated by the methoxy side groups of lignin during the thermal treatment. The reaction was verified by the pyrolysis of a model mixture, using Py-GC/MS and thermogravimetry/mass spectrometry, which consisted of the EFB lipid extract and an isolated beech wood lignin. Demethylation of lignin resulted changes in its thermal decomposition; smaller amounts of 4-methylguaiacol and 4-methylsyringol were evolved and the char yield was increased. The GC/MS analysis of the EFB condensates showed that FAME conversion was the highest and the sources of fatty acid moieties were depleted if the torrefaction temperature had been set at and above 330 °C. The free fatty acid content of EFB was relatively high, which evaporated at lower temperatures before the rate of FAME formation increased between 270 and 300 °C. In comparison with torrefaction, only a small portion of FAMEs formed during the flash pyrolysis of raw EFB at 450 °C indicating that the prolonged heating of the oily biomass favors the FAME formation. Pyrolysis-GC/MS measurements of the torrefied samples showed that the triglyceride residue could also be utilized if the torrefaction as pretreatment was performed at or below 300 °C. In addition, torrefaction increased the accessibility of the biomass components for FAME formation. Some other fatty acid derivatives (i.e., ketone, hydrocarbon, amide, and nitrile) were also detected in smaller amounts. The phenomenon of in situ FAME formation during pyrolysis might be a useful process to enhance pyrolytic biomass utilization by producing FAMEs as additional fuel products and increasing the char yield simultaneously.

Comparison and characterization of torrefaction performance and pyrolysis behaviour of softwood and hardwood

ABSTRACT In this study, the torrefaction and pyrolysis behaviors of softwood (pinewood) and hardwood (teakwood) were experimentally explored. Three different torrefaction temperatures (i.e. 210, 240, and 270°C) and two different residence times (20 and 40 min) were adopted. Various property indicators, for example, solid and energy yields, enhancement factor of higher heating value (HHV), and torrefaction severity index, were used to characterize the torrefaction performance. The principal component analysis (PCA) demonstrated the correlation among different torrefied samples with the help of chemical composition, solid yield, and HHV. Moreover, slow pyrolysis experiments were conducted at three different heating rates (i.e. 15, 30, and 40°C/min) to investigate the thermal degradation behavior of the torrefied biomass samples. Both thermogravimetric and differential thermogravimetric curves shifted to a higher temperature as the pyrolysis heating rate increased. The activation energies E a were estimated by using three isoconversional methods, that is, Kissinger-Akahira-Sunose (KAS), Starink and Flynn-Wall-Ozawa (FWO) methods. The E a broadly increased with torrefaction severity. When using the FWO method, the average E a values ranged from 97.51 to 168.68 kJ/mol and 120.73 to 180.25 kJ/mol for torrefied pinewood and teakwood samples, respectively. Scanning electron microscopy (SEM) images revealed that at higher torrefaction conditions, the samples experienced severe structural damages, leading to crack formation and augmentation. All these observations not only reveal that torrefaction can turn raw biomass into fuel with improved properties but also help to clarify the differences between soft and hardwood for energy utilization purpose.

Effects of oxygen deficient and flue gas torrefaction on the surface property and structural feature of typical agriculture waste: Rice husk

Effects of torrefaction condition on fuel qualities and combustion characteristics of rice husk were studied. The distribution of typical elements and components exhibited that rising torrefaction severity initially decreased and subsequently increased the values of H/C and O/C. The effects of torrefaction condition on lignin content and heating value for torrefied samples expressed identical law. Increasing torrefaction severity decreased the solid yield monotonically, while the corresponding energy yield expressed first upward and then downward trend. The participation of H2O in the torrefaction process was beneficial to the generation of edge nitrogen and the enrichment of reactive functionalities at the expense of hydrophilic groups. The addition of multiple oxidants was conducive to enlarging specific surface area and optimizing fuel combustion behavior at mild temperatures. According to the results obtained from this research, the upgraded sample derived from torrefaction occurred in wet flue gas at 543 K expressed the best fuel quality.

Torrefaction of Napier Grass and Oil Palm Petiole Waste Using Drop-Type Fixed-Bed Pyrolysis Reactor.

The torrefaction process in the preparation of energy materials has garnered a lot of attention and has been investigated as a means of improving biomass solid fuels. The aim of this study is to study the effect of the temperature and holding time of two biomass samples: wild Napier grass and oil palm petiole. The torrefied samples are operated in a pyrolysis reactor to replicate the torrefaction procedure. The temperature parameter ranges between 220 and 300 °C while the holding time of the reaction parameter ranges from 10 to 50 min. It is found that with increasing temperature and time, the moisture content and number of O and H atoms decrease and also cause both mass and energy yield to decrease. It is found that the calorific value and the energy density increase with both parameters, which shows that optimization is needed for better solid fuel production. Between the two parameters, temperature changes have more significant effects on the torrefied samples. The optimized temperature and time are found to be 260 °C and 30 min, respectively. The usage of the pyrolysis reactor for the torrefaction reaction has been proven to serve as a good option due to similar product characteristics and equivalent results.

Evaluation of weight loss and high heating value from biomasses during fungal degradation by NIR spectroscopy

Lignocellulosic biomasses have some characteristics that hinder their use as fuel. Further, the biodegradation processes that can occur during storage can affect their energy properties. Torrefaction can improve their energy properties while reducing the impacts of storage. Near-infrared (NIR) spectroscopy could be a promising tool to estimate changes to biomass properties during storage. A series of waste feedstocks, including: sugarcane bagasse, coffee husk, eucalyptus, and pine were torrefied at 290 °C in a screw reactor, over 5, 7.5, 10, 15, or 20 min. Then, raw and torrefied biomasses were submitted to leaching and to white and brown-rot fungi, to simulate storage conditions. The weight loss (WL) due to fungal degradation after 2, 4, 8, and 12 weeks was measured and the high heating value (HHV) of all biodegradation steps, including raw and torrefied samples after leaching, were determined. All the samples were analysed by NIR spectroscopy and chemometric models were then developed. Firstly, partial least squares for discriminant analysis (PLS-DA) models successfully classified the four different residual biomasses into raw and torrefied forms according to fungal decomposition. Secondly, partial least squares regression (PLSR) models showed potential utility in an industrial context as a standardized continuous method to predict the HHV during biomass storage steps. While, PLSR models did not present good accuracy when estimating WL resulting from fungal degradation, they can be useful for screening during decision making. Further studies are required to improve and develop more efficient models to predict the fungal degradation level of stored biomasses. For exemple, in considering the class of torrefied biomasses, the model could show better predictive capacity due to less variability in the data. These results highlight the potential of NIR spectroscopy as a simple, fast, and efficient tool to analyze the degradation process over time. Such a rapid and non-destructive characterization tool could be very useful in industry to assess biomass property changes during storage.

Investigation on the fuel quality and hydrophobicity of upgraded rice husk derived from various inert and oxidative torrefaction conditions

Torrefaction is a promising approach which could optimize the behavior of biomass effectively. In this research, a typical and abundant agricultural by-product rice husk was employed for clarifying the correlation between upgradation condition and the fuel quality of upgraded sample. Rice husk were torrefied in inert and oxidative atmospheres (O2: 0, 6, 10 and 21 vol%) at three temperatures (493, 543 and 573 K). After undergoing various torrefaction processes, the torrefied samples were analyzed by elemental analysis, componential determination, fiber component identification, Fourier Transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), pore structure identification, contact angle characterization and moisture re-absorption test. The results illustrated that the additional oxidizing atoms could participate in the optimization of surface physiochemical property of rice husk particles during torrefaction process. Oxygen deficient torrefaction expressed a tendency to increase the heating value and the fixed carbon content in torrefied samples significantly. The minimum hydrophilic groups remained on the surface of rice husk sample pretreated in 6 vol% O2, and the specific surface area of upgraded sample torrefied in 6 vol% O2 at 573 K was the maximum. The contact angle results were consistent with that of moisture re-absorption tests, implying that increasing torrefaction severity appropriately was beneficial to optimizing the surface behavior and hydrophobicity of upgraded rice husk. Torrefaction of rice husk performed in 6 vol% O2 at 573 K was the optimum condition in this study.

Torrefaction and Densification of Wood Sawdust for Bioenergy Applications

In this study, wood sawdust as waste residue from wood processing mills was pretreated using torrefaction to improve fuel properties and densified to facilitate transportation. Sawdust was torrefied in a fixed bed reactor using inside temperatures (IT) of 230, 260 and 290 °C for 15, 30 and 45 min, residence time. Due to the low calorific value of the treatments, the outside temperature (OT) of the fixed bed reactor was used instead for a fixed duration of 45 min, which resulted in an increase in energy value by 40% for the most severe conditions. The mechanical strength of the pellets was enhanced by adding 20% binder (steam-treated spruce sawdust) to biochar, which improved the pellet tensile strength by 50%. Liquid by-products from the torrefaction process contained furfural and acetic acid, which can be separated for commercial uses. Thermochemical analysis showed better fuel properties of OT torrefied samples such as high fixed carbon (52%), low volatiles (41%) and lower oxygen contents (27%) compared to IT torrefied samples (18, 77 and 43%, respectively). Low moisture uptake of torrefied pellets compared to raw pellets, along with other attributes such as renewability, make them competent substitutes to fossil-based energy carriers such as coal.