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Torrefaction has been well known to improve the properties of various biomass pellets. However, the study on torrefaction of andong bamboo pellet is still limited. This study aimed to evaluate the changes in the physical and mechanical properties of Andong bamboo (Gigantochloa pseudoarundinaceae) pellets resulting from torrefaction. The pellets were torrefied at 200°C, 240°C, and 280°C using an electric furnace for 50 min. The physical properties analyzed were color, moisture content, density, water adsorption, and resistance to water immersion. A compressive strength test examined the mechanical property. The results showed that the color of bamboo pellets torrefied at 200°C, 240°C, and 280°C were changed, showing overall color change (∆E*) values of more than 12. The lightness (L*) of the pellet remarkably decreased with the increase of torrefaction temperature. In other words, the pellet became darker with increasing temperature. The yellow/blue chromaticity (b*) was also decreased with increasing the torrefaction temperature. However, the red/green chromaticity (a*) increased at 200℃ but decreased at 240℃ and 280℃. Moisture content and pellet density decreased with increasing torrefaction temperature. The pellets’ water adsorption decreased as the torrefaction temperatures increased at 200℃, 240℃, and 280℃. The results also showed that the torrefied pellets were more resistant to water immersion than the control pellet as they could maintain their original form even after 24 h immersion test. The compressive strength decreased as increasing the temperature. The torrefaction temperature affected and improved the properties of Andong bamboo pellets.

The paper presents tests connected to the torrefaction of agro-biomass residues as a case of biomass valorisation. The aim of the work is to compare the changes in energy and chemical properties of millet stalk (Panicum miliaceum L.) before and after the torrefaction process. The torrefaction of the millet stalk was done by using a scale reactor in two temperatures, 275oC and 300oC, in an N2 atmosphere. The millet stalk torrefied at 300oC has more promising parameters, i.e., higher heating value HHV 24,57 MJ/kg, the content of carbon 64,90% and energy density 1,42 compering to biochar produced at 275oC - 22,57 MJ/kg, 60,90% and 1,31 respectively. The results showed that torrefaction improves the parameters of the millet stalk for higher-quality biofuel, which can be used for heat generation.

In this study, the chars were derived through dry and wet torrefaction (DT and WT) of oil palm leaf (OPL), and techno-economic feasibility for char production was evaluated. DT was performed at 200 to 300 °C for 30 min under CO2 atmosphere. WT was performed at 180 to 220 °C for 30 min over process water (PW) reuse. Fuel properties of the DT-char and WT-char products, including mass yield, physiochemical characteristics, fuel properties, thermal stability, surface chemical functional groups, and surface structure were investigated. The study results indicated that DT affected OPL characteristics rather than WT, where the char with outstanding fuel properties was derived through DT. WT affected the fuel properties of OPL marginally. OPL chars with the highest HHV (28.67 MJ/kg), HHV improvement (0.48) and energy yield (131.78 %) could be derived via the DT. The O/C and H/C ratios of the DT-char were reduced and similar to those of lignite coal. PW reuse in WT slightly affected the char fuel properties, thus it is the outstanding method of PW utilization. Techno-economic feasibility analysis results determined that DT is the profitable process for converting OPL to char fuel, and its simple payback period is 14.13 years. These results recommended that DT constitutes a dominant technology for producing char fuel from OPL.

When fossil fuel substitution with biomass is viewed as a potential solution to global warming caused by greenhouse gas emissions, the demand for biomass fuel pellets has increased worldwide. Although agricultural waste is an attractive potential feedstock for fuel pellet production due to its relatively high calorific value and low cost, its excessive ash content is a major drawback. This research investigates the properties of sugarcane bagasse fuel pellets treated by dry and wet torrefaction and evaluates the economic value of selling the fuel pellets, which were priced based on their quality. It was found that the wet torrefaction could significantly reduce the ash content in the product (1% ash content at a torrefaction temperature of above 180°C), resulting in higher quality and more marketable fuel pellets. Consequently, the yield and the net present value of the production of wet torrefied fuel pellets were greater than those of dry torrefied pellets. Nevertheless, the production of fuel pellets from sugarcane bagasse treated by either process is shown to be economically viable.

Microwave simulation is significant in identifying a reactor design allowing the biomass to be heated and processed evenly. This study integrated the radio frequency and transient heat transfer modules to simulate the microwave distribution and investigated the performance of microwave heating in the cavity. The simulation results were compared with the experimental findings using the finite element analysis software of COMSOL MULTIPHYSICS to predict the temperature profile and electric field of microwave in the biomass (empty fruit bunch pellets). The higher temperature distribution was observed at the bottom and centre section of the empty fruit bunch pellet bed in the reactor, showing the uniqueness of microwave heating. According to the simulation results, the temperature profile obtained through the specific cavity geometry and dielectric properties agreed with the experimental temperature profile. The simulated temperature profile demonstrated a logarithmic increase of 120 °C/min at the first 50 s followed by 50 °C/min until 350 s. The experimental temperature profile showed three different heating rates before reaching 300 °C, including 78.3 °C/min (50–120 °C), 30.6 °C/min (121–250 °C), and 105 °C/min (250–300 °C). The results of this study might contribute to the improvement of microwave heating in biomass torrefaction.

In this paper, a matter of biomass torrefaction and gasification is closely looked at from different points of view during low load and low equivalence ratio regime, defined as λ=0.08. Considering gas production, the hot gas efficiency of conversion (30%) and its energy content (4.14 MJ m−3) were not quite satisfying, however, this matter of fact was compensated by an interesting yield of biochar. This material was generated in 0.387 and 0.314 rates for torrefaction and torrefaction + gasification processes, respectively, which, in both cases, represents an attractive, alternative approach to the functional energy storage. It was determined that a CO2 offset of 721 kg and 660 kg could be achieved per 1 tonne of woodchips for gasification of raw woodchips and a 2-stage process with torrefaction and gasification, respectively. The measured data from both technological complexes were compared with the computational model, applying equilibrium reactions for gas components determination. In addition, the question of tar compounds contained within the producer gas, is investigated through GC–MS analysis on both qualitative and quantitative basis.

Torrefaction is known to reduce the logistical costs of biomass. Torrefied biomass’ prospects as feedstock for fermentation to liquid biofuel are largely unknown. This study investigated the interactions of torrefaction and alkaline pretreatment of wheat straw on glucose yields from enzymatic hydrolysis, including treatment order and the potential for pH to play a role in the process. Across a range of torrefaction severities with temperatures of 200 °C, 220 °C, and 240 °C and durations of 20, 40, and 60 min, torrefaction had a negative impact on glucose yield of wheat straw with or without alkaline pretreatment and regardless of the order of alkaline pretreatment. Alkaline pretreatment after torrefaction results in higher glucose yield than alkaline pretreatment before torrefaction, or by torrefaction alone. Hence, there is the prospect for adding logistical benefits of torrefaction to the bioethanol system if alkaline pretreatment is coupled with torrefaction. Decreasing trend in pH with increase in torrefaction severities was observed for trials without buffer, indicating chemical changes causing the decrease in pH might be associated with the reduction in yield.

[Display omitted] • The heat source in the self-heating torrefaction of dairy manure was determined. • A mathematical model for self-heating torrefaction was developed. • The conditions that induce self-heating of manure up to 300 °C were determined. • Higher pressure and lower ventilation induce self-heating at lower temperatures. A self-heating torrefaction system was developed to overcome the difficulties in converting high-moisture biomass to biochar. In self-heating torrefaction, the ventilation rate and ambient pressure must be set properly to initiate the process. However, the minimum temperature at which self-heating begins is unclear because the effects of these operating variables on the heat balance are not theoretically understood. The present report presents a mathematical model for the self-heating of dairy manure based on the heat balance equation. The first step was to estimate the heat source; experimental data showed that the activation energy for the chemical oxidation of dairy manure is 67.5 kJ/mol. Next, the heat balance of feedstock in the process was analyzed. Results revealed that the higher the ambient pressure and the lower the ventilation rate at any given pressure, the lower the temperature at which self-heating is induced. The lowest induction temperature was 71 °C at a ventilation rate of 0.05 L min−1 kg-AFS−1 (AFS: ash-free solid). The model also revealed that the ventilation rate significantly affects the heat balance of feedstock and drying rate, suggesting an optimal range for ventilation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

There are increasing demands for syngas production. Fossil‐based fuels are expensive and environmentally unfriendly. Affordable, sustainable, and environmentally healthy alternatives and sustainable fuel sources are needed. This study focused on producing tor‐chars from two different tropical biomasses (from Nigeria, West Africa), which were torrefied and characterized to improve their properties for potential use as sustainable feedstocks in an entrained flow gasifier for syngas production. Torrefaction temperatures of 230, 240, 250, and 270 °C and residence times of 30 and 60 min were used to torrefy sundried sorghum straw (SS) and millet straw (MS) at particle size ≤5 mm. The properties of torrefied MS and SS improved significantly due to torrefaction. The optimum conditions for pretreatment of sundried MS and SS were 240 °C and 60 min, at which increased energy density significantly compensated for the severe mass loss and significant degradation of hemicellulose and cellulose. Under these conditions, the respective mass and energy yields were 53 wt% and 75% for millet straw and 49 wt% and 75% for sorghum straw. The O:C atomic ratio decreased to 0.3 in MS tor‐chars and 0.2 in SS tor‐chars resulting in higher heating values of 25 MJ kg−1 and 27 MJ kg−1, respectively. Under optimum conditions, the ash content increased by 107% to be approximately 7 wt% in MS tor‐char, and by 118% to about 7 wt% in SS tor‐char. These properties are promising for potential feedstocks in co‐firing plants or gasification systems. © 2022 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

The results of experimental and computational studies of torrefaction (low-temperature pyrolysis) of granular plant biomass are presented. As a result of this process, high-quality solid hydrophobic biofuel with increased calorific value is obtained from biomass of various types (including waste). Unlike fossil coal, torrefied fuel contains virtually no sulfur and heavy metals, has a lower ash content, and is a carbon-neutral product. The carbon dioxide released during the combustion of plant biofuels is completely absorbed during the period of plant growth. Biofuels are a renewable resource. The annual increase in biomass is 400 billion t, and the rate of energy accumulation by terrestrial biomass is 3 × 1021 J/year. The article considers a vertical reactor with a dense layer of pellets moving towards the heating gas flow under the action of its own weight and features of its operation, taking into account the possible implementation of the concept of a controlled exothermic reaction. To ensure the set mode, the plant has two control units: for controlling and maintaining the set temperature of the coolant at the reactor inlet and for controlling the opening of dampers for unloading finished products into the cooling zone. Experimental and calculated data are presented for three characteristic operating modes of the installation: with limitation of the exothermic reaction due to the control of the inlet temperature, with a controlled exothermic reaction, and with the production of biochar. The second mode turned out to be the most energy efficient. The deviation of the calculated data from the experimental data was no more than 4%. It is shown that the use of the energy of an exothermic reaction can significantly increase the energy efficiency of the process of obtaining carbon-neutral solid biofuel. [ABSTRACT FROM AUTHOR]

Torrefaction, as a pretreatment of biomass coupled with pyrolysis process, has gathered significant attention in recent years to obtain higher quality bio-oil. Being an energy-intensive process, the application of byproducts such as biochar from the integrated process might offset the extra energy provided during the torrefaction process. With this hypothesis, present work aimed to investigate the performance of biochar (BC) obtained from pyrolysis of native (BC-raw) and torrefied biomass (BC-torrefied) towards the synthetic wastewater treatment containing methylene blue (MB) dye. Both biochars were characterized by their physicochemical properties. The impact of time, dose of adsorbent, pH, concentration of MB, and temperature were examined during batch adsorption process. Results showed that BC-torrefied (103.47 m2/g) has higher Brunauer–Emmett–Teller (BET) surface area than BC-raw (80.40 m2/g). Both biochars behave in similar fashion toward MB removal; however, BC-torrefied had greater adsorption capacity (158.13 mg/g from Sips isotherm at 50 mg/L MB concentration) because of higher BET surface area, pore volume, and complexation on surface as compared to BC-raw (85.68 mg/g from Sips isotherm at 50 mg/L MB concentration). The experimental data were in good agreement with Sips isotherm and pseudo-second-order kinetic model for both biochars. The MB adsorption was unprompted and endothermic. Further, it was observed that hydrogen bonding, electrostatic force of attraction, ion exchange, surface complexation, and π - π interaction between MB dye and adsorbent were primarily accountable for adsorption process. Thus, BC-torrefied could be novel adsorbent for water treatment, and its application will facilitate the integrated torrefaction-pyrolysis process. [ABSTRACT FROM AUTHOR]

The pretreatment of biomass through torrefaction is an effective means of improving the fuel quality of woody biomass and its suitability for use in existing facilities burning thermal coal. Densification of torrefied biomass produces a fuel of similar energy density, moisture content, and fixed carbon content to low-grade coals. Additionally, if the torrefaction conditions are optimized, the produced torrefied pellet will be resistant to weathering and biological degradation, allowing for outdoor storage and transport in a manner similar to coal. In untreated biomass, lignin is the primary binding agent for biomass pellets and is activated by the heat and pressures of the pellet extrusion process. The thermal degradation of lignin during torrefaction reduces its binding ability, resulting in pellets of low durability not suitable for transportation. The use of a binding agent can increase the durability of torrefied pellets/briquettes through a number of different binding mechanisms depending on the binder used. This study gives a review of granular binding mechanisms, as they apply to torrefied biomass and assesses a variety of organic and inorganic binding agents, ranking them on their applicability to torrefied pellets based on a number of criteria, including durability, hydrophobicity, and cost. The best binders were found to be solid lignin by-product derived from pulp and paper processing, biomass tar derived from biomass pyrolysis, tall oil pitch, and lime. [ABSTRACT FROM AUTHOR]

In this paper, a new approach to the torrefaction process is proposed. The approach consists of obtaining a single torrefied product with an energy value and standardized physicochemical properties in the range of sub-bituminous coal from two types of waste: the cotton stalk and vine pruning. A multifactorial design was used to investigate the effect of temperature, time, and reaction atmosphere on the properties of the torrefied product (char). The process was optimized according to the mass and energy yield and the increase in the higher heating value (HHV). A series of physicochemical, kinetic, and microscopic analyses were carried out on the raw and torrefied biomass to evaluate the combustible properties. Char was obtained with an energy value in the range of sub-bituminous coal and with more uniform fuel properties concerning raw biomass. The optimal torrefaction conditions for cotton stalk were 6% O2–257.8°C–60 min and 0% O2–275°C–20 min for vine pruning. The HHV of the cotton stalk and vine pruning increased from 16.88 to 22.21 MJ kg−1 and from 17.01 to 22.43 MJ kg−1, respectively. The char from both residues presented similar O/C and H/C atomic ratios, and its value decreased compared with the raw biomass. Char is hydrophobic and easy to grind. Oxygen concentration played an essential role in reducing the time and temperature of torrefaction. [ABSTRACT FROM AUTHOR]

The amount of cattle manure generated accounts for over 40% of the livestock manure in South Korea. Most livestock manure is utilized as a fertilizer and a soil amendment. However, the soil nutrients have exceeded saturation in South Korea. Accordingly, cattle manure, including lignocellulosic biomass, was applied for solid fuel production in this study. The three different types of carbonization process, namely, hydrothermal carbonization, torrefaction, and carbonization (slow pyrolysis), were estimated for a comparison of the hydrochar, torrefied char, and biochar characteristics derived from cattle manure. The processes were performed at temperatures ranging from 190 to 450 °C. The evaluation of the hydrochar, torrefied char, and biochar produced by three processes was conducted by the proximate, ultimate, calorific value, fuel ratio, and energy yield, which were used for the analysis of fuel quality. Additionally, the ash properties, including silicon dioxide, chlorine, and base-to-acid ratio (B/A) on hydrochar, torrefied char, and biochar were investigated to predict ash deposition during combustion. These analyses are essential to stabilize the operation of the combustion chamber. The thermogravimetric analysis represented the upgraded quality of hydrochar, torrefied char, and biochar by three different carbonization processes. [ABSTRACT FROM AUTHOR]

Plant cultivation waste (straw and husk of sunflower, rice, miller, and other cereal crops) feature low moisture and ash content, and their heating value is close to or even higher than that of many power plant coals. The utilization of such waste for energy-generation purposes could help solve environmental problems connected with decreasing greenhouse gas emissions. At the same time, the chemical composition of the ash from this waste results in its having a low melting temperature, which causes the furnace slagging to occur and a rapid growth of ash deposits on the boiler convective heating surfaces. The well-known methods for waste pretreatment before combustion (water flushing and hydrothermal carbonization) feature excessive energy consumption and low yield. Therefore, it is proposed to estimate the effect on ash-melting properties of such a treatment method as torrefaction. Two biomass torrefaction methods were used: in the medium of gaseous torrefaction products in a plate reactor with a mechanically stirred biomass bed and fluidized bed torrefaction in a superheated steam medium. The chemical composition of the ash from biochars obtained using both methods is studied. Based on the known data, prediction criteria were calculated using which it is possible to estimate the possibility of biochar ash to melt, slag agglomerates to emerge, ash deposits to form on the boiler convective heating surfaces, and agglomerates to form during sunflower husk fluidized bed combustion. As is known, the use of prediction criteria often yields contradictory results. In view of this circumstance, for estimating the melting properties of ash from biochars and similar biomass, a 3D diagram was used, with the concentrations of various oxides contained in the ash marked on its axis. By using this diagram, the melting properties of the obtained biochars can be compared with those of other biomass kinds. This allows the following conclusion to be drawn: biochar produced as a result of torrefaction performed in a superheated steam medium is close in its fuel characteristics to wood waste; i.e., it can be combusted alone without additions or mixtures with other kinds of fuel having a refractory ash. [ABSTRACT FROM AUTHOR]

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In recent years, palm kernel shell (PKS) has become a viable feedstock for making biofuels and value-added commodities using a variety of thermal conversion routes. Therefore, significant conservation is required for PKS as a resource for fuel production in biofuel facilities. Thus, this research was intended to elucidate the effects on PKS as a solid fuel through torrefaction and the production of bio-char and bio-oil by single and co-pyrolysis of PKS and polyethylene (PE). The PKS was treated through torrefaction at different temperatures and holding times. The optimum parameters for torrefaction were a temperature of 250 oC and a holding time of 60 min. Then the PKS and PE were pyrolyzed in a fixed-bed reactor at different temperatures and ratios. The product yield was analysed for single and co-pyrolysis of PKS and PE for pyrolysis. The properties of the product composition for single and co-pyrolysis of the PKS and PE were determined by proximate analysis, Fourier transform infrared (FTIR) analysis, and gas chromatography-mass spectrometry (GC-MS). The optimum parameter obtained for biochar and bio-oil production from co-pyrolysis of PKS and PE was at temperature of 500 oC at a ratio of 1:2 (PKS: PE). The ester and phenol compounds were increased around 19.02 to 23.18% and 32.51 to 34.80 %, respectively, while amide and amine decreased around 4.94 to 18.87% and 0.63 to 32.39 %, respectively, compared to the single pyrolysis of PKS. Therefore, the PKS and PE co-pyrolysis significantly increased the amount of phenol and ester compounds while slightly reducing the amount of amide and amine compounds in the bio-oil product. As a conclusion, biomass conservation enables the manufacturing of value-added chemicals. [ABSTRACT FROM AUTHOR]

Torrefaction operation is an essential pathway for solid biofuel upgrading, and good hydrophobicity of torrefied biochar is conducive to its storage. Herein, a two-stage treatment of torrefaction followed by modification by hexadecyltrimethoxysilane was adopted to improve the moisture resistance performance of biochar. This two-stage treatment process led to a longer torrefied microalgal biochar preservation time (60–200% improved) and great superhydrophobicity and superlipophilicity. Therefore, the modified microalgal biochar could significantly adsorb leaking oil for environmental remediation and further improve the calorific value of the biochar. The obtained results indicated that the oil adsorption capacity of modified microalgal biochar was correlated to torrefaction temperature and oil species. Specifically, the oil adsorption capacity was enhanced up to 70–80% from the modification process when comparing to raw microalga. Increasing the torrefaction temperature enhanced the adsorption quantity of the modified microalgal biochar. By adsorbing the oil, the calorific value of oilchar, namely, biochar with adsorbed oil, could be higher than 40 MJ kg− 1. Furthermore, the pyrolysis and combustion characteristics suggested that biochar stability gradually rose as the torrefaction temperature increased. By comprehensively analyzing and comparing the fuel performance of the modified microalgal biochar with previous literature, the obtained modified microalgal biochar possessed better fuel properties and environmental sustainability. Highlights: The HHV of the modified microalgal biochar could be enhanced after oil adsorption. Oil adsorption capacity of two-stage treated biochar was enhanced to 70–80% than raw microalga. The hydrophobicity of two-stage treated biochar was improved to 60–200% than raw microalga. [ABSTRACT FROM AUTHOR]

Heat‐treated rice hull residues were evaluated as fillers in poly(styrene‐co‐butadiene) rubber (SBR) compounds. The currently used precipitated silica filler was replaced with torrefied filler in concentrations varying from 0 to 100 wt%, and the influence of coupler concentration varying from 0% to 3% (7 parts per hundred rubber or phr total) on the filler‐rubber interaction was investigated. The curing process, dynamic properties, and mechanical properties of the SBR compounds were examined for silica‐filled and torrefied rice hull (TRH)‐filled materials with and without the coupling agent. Partial or full replacement of silica with TRH resulted in a systematic decrease in compound viscosity. Longer scorch (ts2) and shorter cure times (t90) were also observed. Incorporation of TRH increased compound modulus (stress at 100% elongation or M100 and Young's modulus) but decreased tensile strength and elongation. The presence of coupler brought about improved dynamic and mechanical properties and 30% lower tan δ at 3 phr level. Results provided the first evidence that, when used as a filler in an SBR compound, torrefied rice hulls can be chemically coupled to the SBR polymer, resulting in increased polymer‐filler interactions analogous to the conventional silica‐coupler‐polymer system. [ABSTRACT FROM AUTHOR]

Combining biomass, a clean and renewable energy source, with waste plastic, which serves as a good auxiliary fuel, can produce high-quality clean fuel. The performance of biomass-derived fuel can be improved by torrefaction. This study optimized the co-torrefaction of fungus bran and polypropylene (PP) waste plastic to obtain clean solid biofuel with high calorific value and low ash content (AC) using response surface methodology. Two sets of mixed biochars were investigated using a multiobjective optimization method: mass yield–higher heating value–ash content (MY-HHV-AC) and energy yield–ash content (EY-AC). PP increased the heat value, decreased AC, and acted as a binder. The optimal operating conditions regarding reaction temperature, reaction time, and PP blending ratio were 230.68 °C, 30 min, and 20%, respectively, for the MY-HHV-AC set and 220 °C, 30 min, 20%, respectively, for the EY-AC set. The MY-HHV-AC set had properties close to those of peat and lignite. Furthermore, compared with that of the pure biochar, the AC of the two sets decreased by 15.71% and 14.88%, respectively, indicating that the prepared mixed biochars served as ideal biofuels. Finally, a circular economy framework for biobriquette fuel was proposed and prospects for preparing pellets provided. [ABSTRACT FROM AUTHOR]

In this research, the upgrading of agro-industrial wastes was investigated by using the torrefaction pretreatment technique. Two types of biomass waste, including sugarcane bagasse (SBG) and palm kernel shell (PKS), were used as raw materials. The operating conditions, i.e., torrefaction temperature and residence time, are between 225–300 °C and 30–90 minutes. The findings show that, in terms of mass yield and calorific value of the solid product, the torrefaction temperature is a more sensitive parameter than the residence time. By increasing the torrefaction temperature from 225 to 300 °C, the mass yields are dropped in the range of 28.79–31.57 wt.% and 28.00–29.88 wt.%, while the effect of holding time exhibits the mass yield decreasing only 3.12–5.90 wt.% and 1.53–3.41 wt.%, for SBG and PKS torrefaction, respectively. In terms of calorific value, higher heating values increase as torrefaction severity increases, varying in the range of 0.29–2.84 MJ/kg, with torrefaction temperature as the dominant factor. Regarding the calorific value, energy yield, energy gain, and energy-mass co-benefit index, the optimal operating conditions for SBG and PKS torrefactions are the same condition as 275 °C for 90 minutes. SBG and PKS bio-coals obtained from torrefaction are promising solid fuels with high calorific value (about 23 MJ/kg), with an energy yield of 73.93–77.41%, relative to coal that could be further utilized for co-firing in thermal power plants. [ABSTRACT FROM AUTHOR]

Torrefaction pretreatment is a mild form of pyrolysis that has the potential to produce a high-quality raw material for making biofuel that serves as a replacement for coal in the bioenergy industry. Microwave-assisted torrefaction was conducted on white spruce sawdust (WSS) at temperatures of 200 °C, 250 °C, and 300 °C and retention times of 5 min, 7 min, and 9 min in an inert environment. The torrefaction process produces a solid carbon, commonly known as biochar, and condensable (torrefaction liquid (TL)) and non-condensable gases. In this study, torrefaction characteristics were investigated to observe its effects on the thermal and physiochemical properties of the pellets produced. During the torrefaction process, a significant mass loss associated with the decomposition of hemicellulose was observed. The hemicellulose content drastically reduced to approximately 1.8% and the cellulose content was reduced by approximately 10%, while the lignin gained approximately 35% as the severity increased. This led to an improvement in the higher heating value (HHV), hydrophobicity, bulk, particle density, pellet dimensional stability, and pellet density. However, the pellet tensile strength decreased as the torrefaction severity increased. Pellet tensile strength is a critical indicator of biomass pellets that expresses the force required to crush or damage a pellet. Therefore, to enhance the tensile strength of the pellets, the introduction of a binder was necessary. Torrefaction liquid and sawdust were used as additives at different proportions during pelletization. The addition of binders (torrefaction liquid and sawdust) to the pellet formulation increased the tensile strength of the torrefied WSS by approximately 50%. The OH groups in the biomass break down to a limited degree due to dehydration. This hinders the formation of H bonds, thereby increasing the chances that the pretreated biomass will become hydrophobic. The SEM graphs showed that the torrefied WSS pellets demonstrated more firmly glued surfaces with fewer pores spaces when set side by side with the raw pellets. The thermogravimetric analysis conducted showed that the torrefaction of WSS slightly reduced its thermal stability. [ABSTRACT FROM AUTHOR]

Climate change, biomass utilization, and bioenergy recovery are among the biggest current global concerns. Wood is considered an environmentally benign material. Nevertheless, it must be processed for desired applications. Upon thermal treatment ranging from 180 °C to 280 °C, under low oxygen concentrations, wood becomes a material with improved dimensional stability, resistance to fungal attacks, grindability, hydrophobicity, and storage stability. Several strategies for wood treatment have been investigated over the course of the past decades, including the use of steam, nitrogen, smoke, vacuum, water, and hot oil. The goal of this work is to investigate the influence of pressure and atmosphere on the torrefaction of poplar. Through a systematic analysis of poplar wood samples treated under reduced pressures and different atmospheres, while keeping the same heating profile, it was possible to establish that changes observed for mass loss, color change, wood composition (via TGA/DTG analysis), functional groups (via FTIR), elemental analysis, and X-ray diffractograms relate directly to known reaction pathways occurring during torrefaction. Changes observed under reduced pressures have been associated with the relative concentration of oxygen in the reaction atmosphere and to the reduced diffusion times experienced by reactive by-products during the treatment. Conversely, extended diffusion times resulted in more significant changes for reactions carried out under N2, water vapor, and air. [ABSTRACT FROM AUTHOR]

Torrefaction is a pretreatment method for upgrading biomass into solid fuels. This study aimed to investigate the properties of agro-byproducts pretreated under different oxidative conditions at temperatures of 210–290 °C for 1 h to determine optimal operating conditions for upgrading biomass. The mass yields of lignocellulosic and herbaceous biomass were 90.27–42.20% and 92.00–45.50% and 85.71–27.23% and 88.09–41.58% under oxidative and reductive conditions, respectively. The calorific value of lignocellulosic and herbaceous biomass under oxidative conditions increased by approximately 0.14–9.60% and 3.98–20.02%, respectively. Energy yield of lignocellulosic and herbaceous biomass showed 63.78–96.93% and 90.77–44.39% showed 88.09–41.58% and 92.38–27.23% under oxygen-rich and deficit conditions. A decrease in oxygen and an increase in carbon dioxide and carbon monoxide were confirmed through gas measurements. Torrefaction evaluations were conducted using energy–mass co-benefit index (EMCI). Decreases of ΔEMCI were observed under certain conditions. Both oxidative and reductive conditions can be employed for pepper stems, wood pellets, and pruned apple branches. Based on standards, the optimal temperatures for pepper stems, wood pellets, and pruned apple branches in oxidative conditions were 250, 270, and 250 °C, respectively.

Biomass powers have been recently increased in Thailand, over demand of biomass has become a problem led to finding out alternative agricultural waste to be used as fuel. Rice straw is one of promising biomass with very high quantity and quality. However, upgrading rice straw could be more attractive. Rice straw, an agricultural waste, has been interested in being prepared as the renewable energy resource for industrial scale. In 2019–2021, rice straw was estimated to be 15 Mton/year and left on fields after harvesting. Its heating value is approximately 12 MJ/kg, and thus the energy could be 180 × 106 GJ/year. The objective of this study is to enhance the fuel properties of rice straw using torrefaction technology. The effect of positive and negative pressure (−0.4, 0.8 and 2 barg) on energy yield (EY) and specific energy consumption (SEC) was initially investigated at temperature and time of 200 °C and 40 min, respectively. It was found that the positive pressure of 2 barg gave the highest EY of 94.95%, but the SEC was higher than the condition while applying negative pressure (−0.4 barg). Furthermore, the factors of temperature, time, and pressure were designed to study their combined effects on EY and SEC. The ranges of temperature, time, and pressure for torrefaction of rice straw were 200–220 °C, 30 to 50 and -0.4 to 2 barg, respectively. The response surface methodology based on central composite design using Minitab V.18 program was investigated on two responses (EY and SEC). It was found that severe conditions gave lower mass yield but they resulted in higher heating values of the torrefied rice straw. However, higher energy was consumed during the process. The maximum EY of 94.43% and minimum SEC of 21.94 Wh/g were obtained at the optimum conditions of 200 °C, 30 min and −0.4 barg. In addition, from the proximate and ultimate analysis, the torrefied rice straw by this optimal condition had better fuel properties than the raw one due to higher fixed carbon (FC), hydrogen to carbon ratio (H/C) and oxygen to carbon ratio (O/C).

The torrefaction process represents a thermal conversion technique conducted at relatively low temperatures ranging between 200 to 300 °C. Its objective is to produce fuel with a higher energy density by decomposing the reactive portion of hemicellulose. In this study, the kinetics of mass loss during torrefaction were investigated for willow. The experiments were carried out under isothermal conditions using thermogravimetric analysis. Batch torrefaction reactor designs were conducted and explained in detail. Co-combustion of willow with hard coal (origin: Katowice mine) in different mass ratios (25% biomass + 75% coal, 50% biomass + 50% coal, and 75% biomass + 25% coal) was conducted in addition to raw biomass torrefaction. TG/MS analysis (a combination of thermogravimetric analysis with mass spectrometry analysis) was performed in the research. The optimal torrefaction conditions for willow were identified as an average temperature of 245 °C and a residence time of 14 min, resulting in the lowest mass loss (30.15%). However, it was noted that the composition of torgas, a by-product of torrefaction, presents challenges in providing a combustible gas with sufficient heat flux to meet the energy needs of the process. Prolonged residence times over 15 min and higher average temperatures above 250 °C lead to excessive energy losses from volatile torrefaction products, making them suboptimal for willow. On the other hand, the co-combustion of torrefied biomass with hard coal offers advantages in reduced sulfur emissions but can lead to increased NOx emissions when biomass with a higher nitrogen content is co-combusted in proportions exceeding 50% biomass. This paper summarizes findings related to optimizing torrefaction conditions, challenges in torgas composition, and the emissions implications of co-combustion.

Lignocellulosic biomass has demonstrated great potential as feedstock for pellet production, notwithstanding the fact that the industrial production of pellets is faced with some economic challenges. This study presents a technoeconomic analysis of six scenarios to develop a process model for pellet production from sawdust and oat straw that employs torrefaction and steam explosion pretreatment prior to pelletization. SuperPro Designer was used to carry out this evaluation. The pellet plants were designed to have a capacity of 9.09 t/h of sawdust and oat straw each. The pellet yield ranged from 59 kt to 72 kt/year. The scenarios analyzed included variations of steam explosion and torrefaction. In some scenarios, materials were lost in the form of liquid and gas due to the pretreatment process. The breakdown of equipment purchase cost showed that the torrefaction reactor is the most expensive unit with approximately 51% of the purchase cost. Facility-dependent and feedstock costs were the major significant contributors to the pellet production cost. The minimum selling prices of the pellets obtained from Scenarios 1–6 were $113.4/t, $118.7/t, $283.4/t, $298.7/t, $200.5/t, and $208.4/t, respectively. The profitability of pellet production as determined by the net present value (NPV), internal rate of return (IRR), and payback period was found to be sensitive to variations in feedstock cost.

The aim of this study is to investigate the thermal behavior of Pinus wood pellets during torrefaction under different operational conditions, as well as to evaluate the potential application of the torrefied product in metallurgical processes. Torrefaction tests were carried out in an oxidizing atmosphere (245 °C) and in an inert atmosphere (270 and 290 °C) at residence times of 15 and 60 min. The results of torrefaction in inert atmosphere were also statistically evaluated. To evaluate the potential application of torrefied biomass in metallurgical processes, reactivity tests with CO2 were performed in the temperature range of 200–1000 °C. The results showed that high torrefaction temperature and residence time decreased the mass yield. Statistical analysis showed the possibility of combining high temperatures with low residence times, or vice versa, to obtain satisfactory mass yields. The experimental results showed the highest reactivity for the torrefied biomass obtained in an inert atmosphere, at 290 °C and 60 min. However, considering the mass yield and reactivity with CO2, the best torrefaction conditions for biomass with potential application in metallurgical processes were in an inert atmosphere, at 290 °C and a residence time of 15 min.

The objective of this study was to evaluate the effects of torrefaction temperature on the physical and mechanical properties of betung bamboo (Dendrocalamus asper) pellets. Torrefaction was conducted in an electric furnace at 200°C, 240°C, and 280°C for 50 minutes. The physical properties evaluated included color change, density, moisture content, water resistance, and water adsorption. The mechanical properties were also investigated by compressive strength test. The result showed that torrefaction affected the color properties of betung bamboo pellets with ∆E values of more than 12 or totally changed. The density and moisture content of torrefaction bamboo betung pellets decreased with increasing torrefaction temperature. The results also showed that the hydrophobic properties of the bamboo betung pellets improved with the increased of torrefaction temperature. The highest compressive strength value was obtained by bamboo betung pellets torrefied at 200°C and the values decreased with the increase of temperature. In conclusion, there were differences in the physical and mechanical properties of bamboo betung pellets that were torrefied at different temperatures. Torrefaction with an electric furnace effectively improved the quality of betung bamboo pellets.

Biofuel and bioenergy production from diverse biomass sources using thermochemical technologies over the last decades has been investigated. The thermochemical conversion pathways comprise dry processes (i.e., torrefaction, combustion, gasification, and pyrolysis), and wet processes (i.e., liquefaction, supercritical water gasification, and hydrothermal carbonisation). It has been found that the thermochemical processes can convert diverse biomass feedstocks to produce bioenergy sources such as direct heat energy, as well as solid, liquid and gaseous biofuels for instance biochar, bio-oil and syngas. However, some of these processes have limitations that impede their large-scale utilisation such low energy efficiency, high costs, and generation of harmful chemicals that cause environmental concerns. Efforts are being made extensively to improve the conversion technologies in order to reduce or solve these problems for energy efficiency improvement. In this review, the emerging developments in the thermochemical techniques for producing biofuel and bioenergy from biomass are presented and evaluated in terms of their technological concepts and projections for implementation. It is suggested that an integration of torrefaction or hydrothermal carbonisation with combustion and/or gasification may optimise biomass energy use efficiency, enhance product quality, and minimise the formation of noxious compounds.

The aim of this study is to obtain new coffee product variants by torrefaction process with atmospheric media variations. The raw material used was Gayo-Arabica green beans, while the atmospheric medium variations were air, N2, and Ar at a rate of 1 1/minute. About 200 g coffee beans were torrefied in a fixed-bed at 235 ± 8 °C for 60 min and then cooled at the same rate medium. The process ended when temperature reached 50 °C. Subsequently, the beans were removed from the system and measured for yield, color, pH, chlorogenic acid and caffeine content using the UV–Vis method, as well as organoleptic tests. Variations in atmospheric media produced different characteristics of torrefied coffee bean products. The organoleptic test best value was obtained by using atmospheric media Ar (69.75) followed by N2 (67.875) and air (67.625). The absence of oxidizing elements in the atmospheric medium provided an improvement in the aroma and taste of coffee.

Various techniques are implemented to reduce odor emission due to their potential multi-source nature. One modern approach is the use of thermochemically processed biomass to eliminate odors. Compared with raw biomass, processed biomass is characterized by greater porosity and an expanded specific surface. In these laboratory experiments, adsorption tests for a mixture of indole, 2,3-dimethylpyrazine, and 2,3,5-trimethylpyrazine are carried out using torreficates produced from biomass from the agri-food industry (walnut shells, orange peels, peach stones, and apple wood chips). This research is focused on the determination of the correlation between the physical-hydraulic properties of the torreficates and their ability to reduce the odors simulated by the selected compounds. The results indicate that 2,3-dimethylpyrazine and 2,3,5-trimethylpyrazine are not detected in any of the investigated low-temperature biochars. However, indole is detected in most materials, and its most significant quantities are adsorbed on torreficates made of orange peels (45.64 µg·mL−1 ± 40.02 µg·mL−1) and peach stones (61.26 µg·mL−1 ± 49.55 µg·mL−1). The performed analysis reveals that the highest correlation with the ability to adsorb indole is found for the average pore size (r = 0.66) and specific density (r = −0.63) as well as the content of fixed carbon (r = 0.66), which may prove the importance of physical-hydraulic properties in odor sorption by low-temperature torreficates. [ABSTRACT FROM AUTHOR]

The behavior of pulverized woody biomass gasification in an entrained flow gasifier (EFG) is investigated by utilizing an analogy to a coal gasifier. A computational fluid dynamics (CFD) model of a laboratory-scale coal gasifier was developed intended to extend a tool for further investigation of woody biomass gasification. The model is based on a Eulerian-Lagrangian approach that incorporates sub-models of heat and mass transfer, devolatilization, radiation, homogeneous and heterogeneous reactions, as well as the interactions between the gas and particle phases. The developed model is primarily validated with available experimental data and two similar published works. The model is developed for three types of woody biomass, which include typical wood, raw bamboo, and torrefied bamboo, to predict the gas compositions, temperature, and heating value of the produced syngas. The results indicate that the torrefaction process significantly enhances the gasification performance. The heating value of the produced syngas from the torrefied bamboo is increased by more than 35% compared to that of raw bamboo. The maximum predicted temperature for the typical wood is 1940 K while it is 2010 K and 2160 K for the raw and torrefied bamboos, respectively. Moreover, the predicted results suggest that while the range of the volatile matter is between 50 to 60 wt%, the fixed-carbon range is between 30 and 40 wt%, and the moisture content is under 10 wt%, different woody biomasses could be replaced with each other without significant reduction in the gasification performance. [ABSTRACT FROM AUTHOR]

Torrefaction is an effective technology to overcome the defects of biomass which are adverse to its utilization as solid fuels. For assessing the torrefaction process, it is essential to characterize the properties of torrefied biomass. However, the preparation and characterization of torrefied biomass often consume a lot of time, costs, and manpower. Developing a reliable method to predict the fuel properties of torrefied biomass while avoiding various experiments and tests is of great value. In this study, a machine learning (ML) model of back propagation neural network (BPNN) hybridized with genetic algorithm (GA) optimization was developed to predict the important properties of torrefied biomass for the fuel purpose involving fuel ratio (FR), H/C and O/C ratios, high heating value (HHV) and the mass and energy yields (MY and EY) based on the proximate analysis results of raw biomass and torrefaction conditions. R2 and RMSE were examined to evaluate the prediction precision of the model. The results showed that the GA-BPNN model exhibited excellent accuracy in predicting all properties with the values of R2 higher than 0.91 and RMSE less than 1.1879. Notably, the GA-BPNN model is applicable to any type of biomass feedstock, whether it was dried or not before torrefaction. This study filled the gap of ML application in predicting the multiple fuel properties of torrefied biomass. The results could provide reference to torrefaction technology as well as the design of torrefaction facilities. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the influence of biomass particle size on the torrefaction characteristics under different torrefaction temperatures and times. Paulownia wood with particle sizes ranging from 12 to <0.3 mm was selected. It was torrefied at 260 and 290 °C in a fixed-bed reactor for 30–90 min. The results showed that biomass particle size did affect the product's evolution during biomass torrefaction. With the decrease in particle size from 12 to <0.3 mm, the yield of the solid product decreased by 5.41 and 3.54 wt.%, the yield of the liquid product increased by 5.87 and 3.25 wt.%, and the yield of the gas product changed insignificantly, at 260 and 290 °C, respectively. Comparatively, torrefaction temperature had a more significant effect on the composition of gas products than particle size and torrefaction time. At lower temperatures, decarboxylation reactions dominated in the torrefaction process with more CO2 produced. However, at higher temperatures, decarbonylation reactions were significantly strengthened with more CO generated. The contents of CO2 and CO could account for more than 98 vol% of the product gas. The influence of particle size on the chemical composition of the solid product was much smaller than that of torrefaction temperature and time, but the energy yield of the solid product decreased with the decrease in particle size. The increase in torrefaction temperature and time could significantly increase the C content in the solid product while reducing its O content. It is recommended to use a relatively higher temperature (e.g., 290 °C) for the torrefaction of large particle biomass, as it could significantly reduce the impact of particle size on the torrefaction process and reduce the torrefaction time. [ABSTRACT FROM AUTHOR]

In recent years, there has been growing interest in the pyrolysis of biomass due to economic and environmental reasons. Low-temperature pyrolysis is one of the most straightforward and low-cost pyrolysis processes that may be used to produce added-value biochars as well as liquid and gas products from waste biomass. Lignocellulosic biomass obtained from the fractionation of Quercus cerris bark including cork-rich and phloem-rich granules were subjected to low-temperature pyrolysis (250–325 °C) and the resulting pyrolysis products were examined. The results showed that 59–90% biochar, 8–24% bio-oil, and 2–16% gas products could be obtained from the waste cork, while phloem results in 53–89% biochar, 8–21% bio-oil, and 3–30% gas. The produced chars are rich sources of calcium, magnesium, and potassium and these elements are concentrated in the char as the pyrolysis temperature increases. The pyrolysis condensates contain high amounts of lignin-derived phenolic compounds with 2-methoxy phenol being the most abundant compound. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass from rice husk (RH) is a renewable resource for fuel production, but it could pose ash-related challenges. This work focused on investigating the effects of pretreatment at different sodium hydroxide (NaOH) concentrations (i.e., 0.0, 0.25, 0.50, 0.75 and 1.00 M) on the calorific values and ash contents of treated RH products, and also finding the optimal torrefaction conditions. The results showed that alkaline pretreatment by sodium hydroxide (NaOH) reduced the ash content in the RH samples by over 85 wt%. Due to its relatively excellent calorific values and low ash content, the RH sample with 0.25 M NaOH pretreatment (i.e., RH-25) was chosen as a starting feedstock in the subsequent torrefaction experiments as a function of 240–360 °C for holding time of 0–90 min. In addition, the surface properties by scanning electron microscopy—energy dispersive X-ray spectroscopy (SEM-EDS) and Fourier-transform infrared spectroscopy (FTIR) were also used to observe the elemental compositions preliminarily. Based on the fuel properties of the torrefied RH products, the optimal torrefaction conditions can be found at around 280 °C for holding 30 min. As compared to the calorific value of the RH-25 (i.e., 18.74 MJ/kg) and its mass yield (i.e., 0.588), the calorific value, enhancement factor and energy yield of the optimal product were 28.97 MJ/kg, 1.55 and 0.91, respectively. Although the resulting product has a high calorific value like coal, it could have slight potential for slagging and fouling tendency and particulate matter emissions due to the relatively high contents of silicon (Si) and sodium (Na), based on the results of EDS and FTIR. [ABSTRACT FROM AUTHOR]

In this study, the non-oxidative torrefaction of oil palm empty fruit bunch (OPEFB) pellets was investigated from 250 to 300 °C for 30 min in a horizontal fixed bed tubular reactor. The effects of the selected conditions on the yields, distributions and fuel characteristics of the torrefaction products were examined. The mass or solid yield (MY) decreased from 68.1 to 36.2%, whereas the liquid yield (LY) and gas yield (GY) increased from 19.4–40.1% and 12.5–23.7%, respectively, due to drying, devolatilization and depolymerisation during torrefaction. Physicochemical and calorific analyses showed that the torrefied OPEFB pellets have high carbon but low oxygen contents, which accounts for the high heating values (HHV = 22.83–25.81 MJ/kg). The torrefied OPEFB pellets also exhibit lower moisture (2–4%) and volatile matter (34.38–65.31 wt.%) but high ash (4–20 wt.%) and fixed carbon (28.69–41.62 wt.%) compared to the raw pellets. The OPEFB pellet fuel properties, namely pH that ranged from 6.65 to 7.74, hydrophobicity from 100 to 23.04% and grindability from 53.66 to 108, were markedly enhanced after torrefaction at 300 °C. The LY consisted of organics (67.64–62.62%) and water (32.36–37.38%) fractions characterised by high acidity (pH = 2.89–3.22) and dark hues formed by holocellulose and lignin thermal degradation at higher torrefaction temperatures. Based on the findings, the torrefied OPEFB pellets is a highly grindable, hydrophobic, thermally stable and promising solid biofuel for firing, co-firing or substituting coal in power plants provided the existing challenges that affect global biomass supply chains are addressed in detail. [ABSTRACT FROM AUTHOR]

Torrefaction is a process of mild pyrolysis at 200–300 °C under nitrogen atmosphere and has been considered to be an effective way to improve the properties of biomass. In this study, lignin was subjected to torrefaction at 200 °C, 230 °C, 260 °C, and 290 °C. Thermogravimetric analysis of lignin samples was performed at a temperature ramp of 25 to 550 °C with the heating rates of 10, 20, 30, or 40 °C min−1. A distributed activation energy model was used to analyze the pyrolysis kinetics of lignin. Then, the lignin samples were subjected to pyrolysis at 600 °C for 10 s. The results showed that torrefaction had a significant effect on the physicochemical properties and pyrolysis characteristics of lignin. Among the torrefied samples, the sample treated at 290 °C exhibited the lowest mass yield (86.07%), lowest energy yield (93.25%), highest content of carbon (63.76%), highest higher heating value (25.18 MJ kg−1), and lowest content of oxygen (30.25%). The activation energy of torrefied lignin samples slightly changed in comparison with those of the raw samples. Torrefaction has a significant effect on pyrolysis products. The peak area % of S-type (41.4%) and P-type (5.4%) phenols in the bio-oil obtained by pyrolysis of LN-200 was the highest. [ABSTRACT FROM AUTHOR]

There is an urgent need for replacement of fossil fuels worldwide. Raw biomass has a low energy density, contains too much moisture, can rot, and it is hygroscopic. This paper presents a very prominent thermal technology that could overcome mentioned deficiencies of raw biomass. This technology is known as torrefaction. Torrefaction is mainly used to convert lignocellulosic materials into 'fuels' that can be used in power plants, combustion units, or gasifiers. [ABSTRACT FROM AUTHOR]

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Torrefaction is a pretreatment method that converts biomass to a fuel-like substance that can replace coal for sustainable power generation. In this work, a thermodynamic-based process simulation model was developed to simulate the gasification of empty fruit bunch (EFB), with torrefaction as pretreatment, to determine the optimum conditions; equivalence ratio, reactor temperature, torrefaction medium concentration, steam-to-biomass (S/B) ratio and system configuration were studied to determine their influence on hydrogen concentration, higher heating value (HHV), syngas ratio and cold gas efficiency (CGE). The highest hydrogen yield was obtained at an S/B ratio of 1.3 at 800 °C, with a syngas ratio of 2.5 and a CGE of 84%. Concentration of torrefaction medium showed no effect on hydrogen concentration due to the simplicity of the model used, but work is in progress in this direction. Therefore, steam gasification is more suitable than air gasification in hydrogen production. • A process model for biomass torrefaction and gasification was developed. • Introduction of steam into gasifier increased H 2 concentration by 10.1%. • The H 2 /CO ratio was higher with lower gasifier temperature, lower equivalence ratio and higher steam/biomass ratio. • Optimum conditions for hydrogen production have been identified. [ABSTRACT FROM AUTHOR]

To reveal the effect of torrefaction pretreatment on pyrolysis and gasification reactivity of biomass, corn cob was first subjected to torrefaction pretreatment in a fixed-bed reactor at various reaction temperatures. The pyrolysis reactivity, kinetics, and gasification reactivity of torrefied corn cob were systematically assessed by various methods, proving that torrefaction pretreatment has a substantial influence on the physicochemical properties of corn cobs. The O/C and H/C molar ratios of corn cobs considerably drop with the increasing torrefaction temperature, and their higher heat-ing value (HHV) and energy density rise as well. It is found that torrefaction improves the pyrolysis reactivity of corn cobs because hemicellulose degradation is more severe than cellulose degradation during torrefaction, resulting in an increase in the percentage of cellulose in torrefied corn cobs. However, the severe depolymerization, polycondensation, and carbonization reaction during torre-faction of corn cobs at 280–300 °C can lead to a significant decline in the pyrolysis reactivity of corn cobs. Torrefaction pretreatment increases the pyrolysis activation energy of corn cobs, in addition to decreasing the char gasification reactivity of corn cob. The average char gasification reactivity of corn cobs drops when torrefaction severity increases. The passivation of active sites on the char surface may cause condensation and carbonation reactions of corn cobs during torrefaction. These findings provide new sights into the reasonable design of efficient torrefaction methods for appli-cation prior to pyrolysis and gasification of biomass. [ABSTRACT FROM AUTHOR]

Motivated by green building applications (bio-composite and insulation materials), thermogravimetric and kinetic analysis is applied to investigate the thermal degradation of cleaned hemp fibers (F), obtained after water retting and mechanical decortication of dioecious plant stalks, and technical fiber (TF), obtained after field retting of monoecious plant stalks. Celluloses (microcrystalline PH105 cellulose and cotton linter cellulose) are used for comparison. F and TF dynamic curves are well described by a four-step scheme. The dominant one concerns pseudo-cellulose decomposition with the release of 70 and 54 mass% volatile matter, respectively. The corresponding activation energies are in the range of typical cellulose values (223 and 211 KJ mol−1). Fiber pretreatments (water washing, mild torrefaction, mercerization) modify the pseudo-cellulose content (release of 73–80 mass% volatile matter) and properties, as testified by the higher activation energies (229–248 kJ mol−1) of the decomposition process. The decortication method also contributes remarkably to the characteristics of the fiber cellulose. [ABSTRACT FROM AUTHOR]