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Agroforestry biomass involving cedar wood (CW), poplar wood (PW), corn stalk, and wheat straw was torrefied in a fixed-bed reactor at the torrefaction temperature (T) of 200–300 °C and the holding ...

Biomass pretreatment is a promising technology for reducing pollutants emitted by coal power plants and reducing coal usage. Pretreatment technologies (e.g., torrefaction and ashcontent, which grea...

This study compares the physicochemical properties and steam gasification reactivity of the chars produced from the pyrolysis of the raw and torrefied food wastes at 800 °C, including leftover rice...

Torrefaction as a thermal pretreatment was conducted on oat hull, canola hull, and barley straw in a fixed-bed reactor at temperatures in the range of 220–300 °C and residence times of 30-60 min to...

Torrefaction has been proven as a promising pretreatment process that can effectively reduce the moisture content and increase the energy density and higher heating value (HHV) of raw biomass and c...

The torrefaction process is an emerging thermal pretreatment method of biomass conversion, which enhances the fuel qualities of biomass. This paper presents different correlations to characterize t...

In this study, atmospheric (AP) and gas-pressurized (GP) torrefaction of Phragmites australis (PAS) were carried out in a rotary tube furnace and a gas-pressurized autoclave, respectively, aiming t...

The effects of temperature and rotating speed of a feeding screw on the key performance parameters (mass yield, energy yield, and energy densification index) of torrefaction in a stationary reactor...

Torrefaction is considered to be an important pretreatment method to enhance the fuel quality for efficient valorization of food waste. In this study, four typical food wastes (leftover rice, lefto...

The aim of this study was to investigate the effect of torrefaction severity and ratio of oxygen carrier to feedstock on syngas production and tar removal during chemical looping gasification of eu...

Biomass torrefaction can be carried out in the unsealed reactor filled with a quiescent layer of mineral filler. Mineral filler limits the oxygen access toward the biomass from the environment and ...

In situ catalytic fast pyrolysis of pretreated wood was investigated using a fluidized bed reactor. The pretreatments included acid-leaching, torrefaction, and a combined pretreatment of acid-leaching followed by torrefaction. Acid-leaching reduced amounts of biomass minerals introduced into the process. However, acid-leaching caused agglomeration during pyrolysis leading to reactor defluidization. Acid-leaching also resulted in an upgraded bio-oil that was less deoxygenated compared to the corresponding bio-oil obtained from raw wood. Conversely, torrefaction had a beneficial effect leading to an increased yield of upgraded bio-oil without affecting its chemical composition. Torrefaction of the acid-leached wood prevented agglomeration, reversed the negative effect acid-leaching had on bio-oil quality, and gave an improvement in upgraded bio-oil yield. These effects, combined with the removal of biomass minerals that are detrimental to the catalyst, suggests acid-leaching coupled with torrefaction is a p...

The combination of torrefaction and pelletization offers the potential to produce fuels with high energy densities on both mass and volume bases as well as excellent storage and transportation char...

Wet torrefaction emerges as a potential biomass pretreatment process to enhance the fuel properties of biomass. The present research was aimed to determine the energy-efficient conditions for the w...

Combined torrefaction and pelletization can effectively improve the quality of the biomass fuel. In this work, particulate matter (PM) emissions from combustion of corn stalk pellets derived from t...

In dedicated wood pellet combustion and cofiring with coal in large pulverized fuel furnaces, poor grindability and low bulk density of biomass are important issues for lowering the unburned carbon...

Seven kinds of highly porous activated carbon were prepared from two different lignocellulosic biomass feedstocks (hybrid willow and miscanthus grass) by utilizing four different processing routes,...

The increasing demand for wood pellets on the market, which is caused by their excellent combustion properties, inspires the production as well as the utilization of alternative biomass pellets as fuel. However, the emission of volatile organic compounds gives pellet materials a distinct odor or off-odor, which is directly perceived by the end user. Thus, there is an urgent need for knowledge about the emitted volatile organic compounds and their potential formation pathways as well as their contributions to odor properties of the pellets. In this study, pellets made of biomass energy crops (i.e., straw or miscanthus), byproducts from the food industry (i.e., rapeseed, grapevine, or DDGS (dried distillers grains with solubles from beer production)), or eucalyptus, as well as torrefied pinewood and torrefied sprucewood were investigated with respect to the emitted volatile compounds and their possible impact on the pellet odor. Headspace solid-phase microextraction in combination with gas chromatography–ma...

A fuel pretreatment technique is one of the most effective ways of using biomass fuel to solve problems including disadvantages of low calorific value, slagging, and fouling. Biomass fuel can gain a high calorific value and lower ash content by torrefaction and ash removal technology, respectively. In this study, a thermogravimetric analysis for deriving combustion parameters and the combustion characteristic factor (S) and an evolved gas analysis for investigating emission characteristics were studied by using a thermogravimetric Fourier transform infrared (TG-FTIR) system with coal, biomass, pretreated biomass, and their blends (10, 20, and 30%) to evaluate the combustibility and environmental performance. In the thermogravimetric analysis, coal and ashless biomass blends showed the greatest combustion performance and were confirmed to have a higher S index. Gas emissions (CO2, CO, NO, and SO2) were also investigated during the combustion process (O2, 21%; N2, 79%) to compare coal and biomass blends wit...

This study compares the influences of wet and dry torrefaction on pyrolysis behaviors of beech wood and wheat straw. These two types of torrefaction were compared at similar mass loss of samples. F...

Combustion of torrefied biomass for power generation has many advantages over combustion of raw biomass, one of which is lower emissions of chlorine-bearing gases. This is because partial evolution of these gases takes place during the torrefaction process; hence, the resulting torrefied biomass has a lower chlorine mass fraction than its raw biomass precursor. Research showed that, during torrefaction of corn straw, the predominant chlorinated species in the evolving gas (“torgas”) are CH3Cl and HCl. The former is more prevalent when torrefaction takes place at temperatures under 350 °C, whereas the latter is more abundant at higher temperatures. In this work, corn straw was torrefied at a furnace temperature of 300 °C for 20 min under atmospheric pressure in an inert nitrogen flow. Under this condition, corn straw lost nearly 40% of its original mass, along with 73% of its chlorine mass to the gas phase. To control the emissions of the chlorinated species, the torrefaction gas was heterogeneously reacte...

This research concerns the investigation of an alternative measurement to directly indicate the severity of torrefaction. Composition and process data from both batch and continuous torrefaction experiments using willow, wheat straw, and cattail biomass were combined and analyzed. The mass yield, which is an indication of torrefaction severity was correlated to the net change in residual carbon concentration (ΔC), and second the total change in mass (ΔMt) was correlated to net change in mass of carbon per 100 g of feedstock (ΔMc). Analysis of the experimental data show a polynomial relationship between the dry mass yield (Ym) and the change residual carbon concentration (ΔC). This relationship is Ym = 5.05ΔC2 – 3.96ΔC + 0.98 (R2 = 0.89). The uncertainty in this correlation is ±7.3% (w/w). The relation between total change in mass (ΔMt) and change in carbon mass (ΔMc) meanwhile was found to fit a linear model by ΔMc = 0.36ΔMt + 1.04 with a coefficient of determination of 0.96. Each of these models was then...

In a new development, Mg-based additives were introduced to the process of torrefaction of cotton stalk to enhance the deoxygenation effect. The properties of torrefaction products obtained using temperatures in the range 200–350 °C and three different types of Mg-based additives (MgO, MgO-K2CO3, and MgO-KNO3-NaNO3) with varied mass ratios (0.5, 1, and 2) were characterized. The yield of solid product significantly declined from 92.02% to 36.95% when the torrefaction temperature rose from 200 to 350 °C, while gas and liquid yields increased to 24.90% and 38.15%, respectively. MgO-K2CO3 was the most effective additive because it not only promoted deoxygenation in the solid product (oxygen content decreased by about 43%) but also reduced the loss of hydrogen. CO2 was the main gas component, and production was promoted as the Mg-based additive mass ratio rose from 0.5 to 2. The phenol and ketone content in the liquid product significantly increased, while the acid content decreased. Biomass torrefaction with...

Biomass for energy production has been extensively studied in the recent years. To overcome some constraints imposed by the chemical-physical properties of the biomass, several pretreatments have been proposed. Torrefaction is one of the most interesting pretreatments because torrefied biomass holds a wide range of advantages over raw biomass. The devolatilization of water and some oxygenated compounds influences the increase in the calorific value on both a mass and volumetric basis. The increase in the density reduces the transportation costs. Moreover, the decreased moisture content increases the resistance of biomass to biological degradation, thus facilitating its storage for long periods. Under torrefaction conditions, approximately 10-40 wt% of the initial biomass is converted into volatile matter including liquid and non-condensable combustible gases.1,2 The energy efficiency of the process could greatly benefit the exploitation of the energy content of these products. Recent studies and technological solutions have demonstrated the possibility to realize polygeneration systems that integrate torrefaction/pyrolysis to a combustion process with the aim of obtaining torrefied material/biochar and/or energy from biomass. Some examples include Pyreg, Pyreg-Aactor GT3, TorPlant, and Top Process.4 The identification of the main volatiles produced under torrefaction regime is useful for the optimization of the operating conditions of the integrated system. The integrated process raises some concerns when biomass from phytoremediation and wood from demolition and construction activities are used as feedstock because they could contain potential toxic elements (PTEs). During the torrefaction treatment, the fate of PTEs should be controlled in order to avoid their release in the gas phase and to evaluate the extent of their concentration in the torrefied biomass. The present work aims at studying torrefaction as an eco-sustainable process for the combined production of a solid biofuel with improved characteristics with respect to the starting material and a combustible vapor phase, embedded in the gas carrier flow, to be directly burned for energy recovery. Herein, torrefaction tests on Populus nigra L. branches from phytoremediation, and demolition wood were conducted at three temperatures, 250, 270 and 300 °C, at a holding time of 15 min. The energetic content of torrefied materials was determined. At the same time, the fate of the heavy metals (Cd, Pb, and Zn) in the raw biomass at different torrefaction temperatures was studied, and their mobility in the torrefied biomass was investigated and compared to the mobility in the raw biomass.

A process model is developed to simulate the performance of a biomass torrefaction unit, which consists of a dryer, a torrefaction reactor, a combustor, and two heat exchangers. The model is capable of predicting the composition of volatiles and torrefied biomass, mass and energy yields, thermal efficiency, process heat requirement, and CO2 emissions. Useful correlations are presented for the heating value, molecular weight, and specific heat of the volatiles. A comparison of the model prediction with the experimental data reported in the literature shows a very good agreement. The performance of a torrefaction unit with production capacity of 150 MWth is predicted with an acceptable accuracy using the presented process model. The effect of moisture content, torrefaction temperature, residence time, and adiabatic flame temperature on key process parameters are examined. The thermal efficiency of willow torrefaction unit is found to be 88% at a moisture content of 50% (dry basis), which increases to 94% as...

The high moisture level and ash content of biomass often hinder its further processing. In this study, torrefaction and degradative solvent extraction were employed to upgrade rice husk waste. Biomass torrefied at five different temperatures, in addition to dry raw biomass for comparison, was extracted in 1-methylnaphthalene at 300 °C for 1 h. Two solid fractions were obtained: extracted biomass (EB) and residue biomass (RB). The extraction yields of the EB and RB were 12–19.3% and 31.7–52% (db), respectively. The torrefaction temperature affected the extraction yields and slightly influenced product characteristics. The EB had almost no ash content as it was concentrated in the RB. However, both the EB and RB had higher heat values and carbon content as well as lower oxygen content than the raw biomass. Therefore, our findings suggest that EB could be utilized not only as fuel but also as functional materials.

With rapid global development, the amount of food waste is increasing, which has seriously affected the environment. Usually, food waste is composted with sawdust to prevent environmental pollution due to the loss of N and S. Unfortunately, the quality of the compost of food waste and sawdust (CFS) is poor, and the material is hard to handle. Torrefaction, a process of slow pyrolysis under anoxic conditions, can be used to improve the properties of a fuel sample. This study investigated the fuel properties of CFS samples subjected to torrefaction at five different temperatures (250, 300, 350, 400 and 450°C) and residence times of 30 min. Physicochemical analyses of the samples were carried out according to standard methods, and the combustion characteristics of the samples were studied by thermogravimetric analysis. Torrefaction has great impact on proximate and ultimate analysis, chlorine contents, energy and mass yields, grindability and combustion characteristcs. The grindability and combustion propert...

This communication reports on selected fuel characteristics of upgraded wheat straw samples prepared by hydrothermal carbonization and torrefaction, including the determination of the release behavior of selected inorganics during high temperature gasification of the raw and upgraded wheat straw, and the gross calorific value (GCV) of the products and raw material. The results of the chemical analysis of the upgraded biofuels samples and the preliminary results of the release of potassium chloride and hydrogen chloride indicate completely different release behaviors under hydrothermal carbonization versus torrefaction conditions. The gross calorific value was higher for hydrothermal carbonization products than for raw and torrefied samples.

Release of chlorine during combustion of raw biomass in boilers is detrimental as it contributes to slagging, fouling, and corrosion. Combustion of torrefied biomass can alleviate such issues, as it contains less chlorine than its raw biomass precursor. This work assessed the effect of the furnace temperature on the chlorine content of generated torrefied biomass and the released gaseous species during the torrefaction process (a mild pyrolysis). The selected biomass was corn straw, which was torrefied at furnace temperatures in the range of 250–400 °C under atmospheric pressure in an inert nitrogen flow. Upon torrrefaction, corn straw lost 32–50% of its original mass to the gas phase, accompanied by more than half of its original mass of chlorine in nearly all cases. The major chlorinated species in the evolving pyrolysis gas (“torgas”) were identified as CH3Cl and HCl. The former was more prevalent at the lower temperatures (

Low-temperature pyrolysis (torrefaction) is the first step for combustion. The produced vapors and solids undergo combustion with a different mechanism. Therefore, the composition of the vapors and the functional groups of the produced solids are very important for combustion because they directly influence the diffusion and transfer of oxygen. In this paper, low-temperature pyrolysis of pinewood was studied in a fixed-bed reactor and also by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The effects of temperature, flow rate of nitrogen, and atmosphere were considered to understand the distribution and properties of gas, liquid, and solid products. In situ DRIFTS was used to monitor the evolution of functional group on the solid during low-temperature pyrolysis. The results indicated that temperature was the dominant factor that influenced product formation. Gases released were mainly CO and CO2, and their yield increased with increasing temperature; noncondensable volatile...

The influences of torrefaction on the structure and pyrolysis behavior of lignin were investigated in this study. After torrefaction, the oxygen content of lignin was reduced, which led to the incr...

Biomass was wet-torrefied to improve its properties prior to gasification. Two kinds of biomass were employed as feedstock, including the larch wood and corn stalk. For both larch wood and corn stalk, the oxygen content of torrefied samples reduced greatly, while the carbon content increased. All of these features had a positive effect on the gasification process, which was discussed in the research. During steam gasification, all of the wet-torrified biomass samples yielded higher amounts of H2 and CO compared to the raw biomass samples, showing the superiority of the wet torrefaction (WT). During CO2 gasification, the CO production was also significantly improved by WT. The kinetic characteristic parameters for the gasification of raw and torrefied biomass samples were determined using the random pore model. It was found that the activation energy of gasification could be reduced by the WT process.

Torrefaction is a method for upgrading raw biomass to produce solid fuels that exhibit higher energy density relative to that of the raw material. In countries that produce significant amounts of agricultural residues, torrefaction may facilitate the utilization of waste in the energy sector by adding value to the raw fuel and opening pathways for new applications. In typical scenarios for utilization as fuel, both the raw and torrefied materials are stored in granular form. Dependent upon the properties of the granular material, the risk of dust explosion may be significant. Torrefaction changes the physical and chemical properties of the biomass and, therefore, affect explosion risk and severity. This work investigates the dust explosion characteristics of raw and torrefied agricultural wastes typically produced in Central European countries. The objective is to provide a characterization of these fuels in terms of explosion properties and make recommendations on storage design and safety. Three residue...

An agro-industrial residue, i.e., sugar beet pulp, was taken into consideration in this work as a feedstock for valorization as a solid fuel and, potentially, as a source of valuable biochemicals obtainable from the torgas condensable fraction. To this end, an experimental program based on torrefaction of such a residue after pectin extraction (PE-SBP) was performed. The alternative scenario of raw sugar beet pulp (raw-SBP) torrefaction was also investigated for comparison. Raw biomasses and torrefaction products were analyzed by different techniques including thermogravimetric analysis and derivative thermogravimetry (TGA-DTG), Fourier transform infrared spectroscopy (FTIR), gas chromatrography coupled to mass spectrometry (GC/MS), and proximate and ultimate analyses. This allowed the comparative investigation of the role played by the pectin extraction method and the torrefaction temperature on the process performance and main properties of the resulting solid products. Outcomes showed that light torrefaction (200-240 °C) is a suitable and more energy-efficient process for production of high quality solid fuels from SBP. Moreover, it resulted that PE-SBP is better than raw-SBP as a feedstock due to its lower nitrogen and ash content.

Waste Camellia oleifera shells (WCOSs) have potential to produce sustainable, clean, green energy sources. In this paper, hydrothermal carbonization (HTC), torrefaction, and pyrolysis were applied to investigate the characterization of three types of biochar from WCOSs. The biochars were analyzed with ultimate analysis, proximate analysis, hydrophobicity, Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction (XRD), scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR). The results showed that the biochars were able to replace the lignite or semi-anthracite coal because of the higher calorific value. In comparison to raw WCOSs, the BET characteristics and hydrophobicity of the biochars were improved by thermochemical processes. Evolutions of WCOSs under different conditions, as determined by FTIR and XRD, showed that hemicelluloses and cellulose were decomposed through HTC, torrefaction, and pyrolysis, while the degradation of lignin occurred through pyrolysis. In addition...

As a result of the characteristics of biomass, biomass exploitation as a secondary fuel feedstock in co-firing is only technically and economically acceptable in the range of 5–10% (w/w). In this study, torrefaction and solvent extraction as biomass pretreatments were conducted to address feedstock limitations, making a larger share of biomass for co-firing feasible. The physical and chemical characteristics of the solvent-extracted biomass were investigated using proximate analysis, ultimate analysis, thermogravimetric analysis, and Fourier transform infrared spectroscopy. Biomass torrefied at 200, 250, 270, 300, and 330 °C was extracted by nonpolar organic solvent 1-methylnaphthalene at 350 °C for 1 h to produce ash-less biomass (extracted biomass). A dry, raw, woody biomass was also extracted under the same conditions to see the effect of torrefaction on the characteristics of extracted biomass and residue biomass. The result shows that solvent extraction was effective in producing ash-less biomass, wi...

The aim of this study was the production of a good quality gasification gas (syngas) with rice husk residues. This material was torrefied before gasification with the aim of improving this last process, and the effect of torrefaction time and temperature was investigated. The variation of temperature from 200 to 300 °C decreased moisture and volatile matter and, consequently, increased higher heating value (HHV). The increase of reaction time from 30 to 60 min at 250 or 300 °C had a milder effect than the rise of torrefaction temperature. The optimum conditions for the rice husk torrefaction prior to gasification were 250 °C and 30 min, as the torrefied material presented an HHV of 22.1 MJ/kg daf and an ash content of 17.7%. The torrefaction increased the rice husk in extractives 14.8% (vs 12.6% in the raw material), mainly in nonpolar extractives and lignin (36.4% vs 28.9%). Py-GC/MS analyses determined that raw rice husk presented a monomeric composition of lignin (H/G/S) of 4:12:1 and ratio of carbohyd...

A mechanistic model of torrefaction was developed for a two-stage rotary reactor, and it was verified with experimental results. Mass and energy balances for each phase are considered in the model. A kinetic model that considers the progressive decomposition of biomass into volatiles and char released simultaneously from the raw biomass was coupled to the balances. Mathematical expressions for residence time, heat transfer coefficient, and bed height inside the kiln were taken from the literature for model calculations. Release of condensable and noncondensable volatiles from biomass during the process was considered in the gas phase, while the solid phase included raw and torrefied biomass. The model can predict different output parameters of torrefaction in a rotary continuous torrefier, such as final amounts of solids, gas yields, and temperatures, for different operational conditions. Properties for torrefied solid, such as high heating value, fixed carbon, and volatile matter, can also be predicted b...

The gasification reactivity of the chars from both raw and torrefied wood, grape marc, and macroalgae has been investigated in this paper. The variations in char gasification reactivity were explained using further investigation of the physicochemical characteristics of the char that can influence the gasification reactivity, i.e., specific surface area, uniformity of the carbonaceous structure, and concentration of alkali metals (Na and K). It was found that the influence of the torrefaction process on the char gasification reactivity strongly depends upon the solid fuel properties and pyrolysis conditions. For a pyrolysis temperature of 800 °C, the gasification reactivity of the chars from both the torrefied grape marc and the torrefied macroalgae was lower than that of the chars from their corresponding raw fuels. This is mainly due to a lower specific surface area and a lower content of alkali metals (Na and/or K) in the chars produced from both the torrefied grape marc and the torrefied macroalgae th...

As an established bioenergy industry, the global wood pellet sector is ideally positioned to adopt biomass torrefaction technologies. In this review, potential benefits and challenges of integrating torrefaction within the pellet industry are reviewed and the required technological interventions to enable this integration are analyzed. It is apparent that integration would accelerate the commercialization of biomass torrefaction and benefit the wood pellet industry, torrefaction developers, as well as coal-based utilities. Torrefied pellets are expected to have distinct applications in power generation and help coal-based utilities to reduce their emission levels and comply with increasingly stringent regulations. Co-firing coal with black pellets requires little-to-no retrofit of the existing power plant and, therefore, can offer a low-cost solution. Two potential pathways, in either an upstream or downstream configuration, for retrofitting torrefaction within a white pellet facility are assessed. A succ...

A two-stage, inclined continuous rotary torrefier with novel flights has been developed in the Biomass Conversion Laboratory at Dalhousie University for improving biomass torrefaction processes. Experimental work on torrefaction of small poplar wood particles (0.5–1.0 mm) in the torrefier was undertaken for a deeper understanding of the working of such torrefiers where the volatile gas released was used as the torrefaction medium instead of nitrogen. The rotary torrefier is operated under different operating conditions by varying its rotational speed, tilt angle and temperature. Measured chemical and physical properties of the torrefied products included ultimate and proximate analysis, structural analysis, energy density, mass yield, energy yield, and bulk density. A novel probe was developed to collect samples of biomass and measure temperature at different interior points along the length of the rotary torrefaction reactor while the biomass was being progressively torrefied in it. Axial temperature dis...

The washing pretreatment and torrefaction pretreatment of corn stalk were performed in this study. The effects of both separate and combined pretreatments on the pyrolysis were studied using TG-FTIR and a fixed bed reactor. Washing pretreatment had little impact on the physicochemical properties of corn stalk, contributing mainly to the removal of some ash and metallic species. Torrefaction pretreatment, on the contrary, decreased the oxygen content but increased the ash content. TG-FTIR analysis showed that TG/DTG curves of corn stalk (CS), washed corn stalk (W-CS), torrefied corn stalk (T-CS), and torrefied-washed corn stalk (TW-CS), in turn, showed a right shift trend, and the initial decomposition temperatures increased obviously. Among the samples, W-CS had the lowest values of 27.58 and 29.76 wt % for the final residue mass in the TG curve and the biochar yield, respectively, and the highest bio-oil yield of 48.32 wt %, indicating that the removal of metallic species facilitated the pyrolysis of cor...

Torrefaction is an effective pretreatment method to improve the uniformity and quality of lignocellolosic biomass before further thermal processing (e.g., gasification, combustion). The objective of this study was to determine the impacts of torrefaction as a pretreatment before liquefaction. Wood chips were torrefied for 2 h at three different temperatures (230, 260, 290 °C) and then subjected to microwave-assisted liquefaction, as was the untreated wood control. The dielectric properties of liquefaction materials, including the biomass samples and liquefaction reagent, were measured to evaluate their abilities to convert electromagnetic energy to heat. The effects of liquefaction time, temperature, and catalyst concentration on the liquefaction efficiency were also investigated. It showed that torrefaction temperature had significant influence on the liquefaction behavior of wood materials. Wood treated at the lowest torrefaction temperature (230 °C) retained the most structural/compositional characteri...

This study focuses on the influence of torrefaction on the char reactivity, char yield, and combustion time of 3–5 mm spherical wood particles in a single particle combustion reactor (SPC) operating at a nominal temperature of 1231 °C. The devolatilization times were reduced and the char burnout times were increased with increasing torrefaction degree. The devolatilization time depended linearly on the particle mass. The torrefaction pretreatment resulted in a marked increase in char yield and char particle density but no intrinsic reactivity change as determined by thermogravimetric analysis. The char yield and char particle density increased from 9 wt % and 123 kg/m3 for raw particles to 14 wt % and 259 kg/m3 for particles pretreated at 290 °C for 4 h. The results of this study demonstrate that the higher char yield and density are the main reasons for the longer combustion time of torrefied wood.

In the present work, the gasification performances of two pairs of raw and torrefied biomasses, including raw forest residue and torrefied forest residue, and raw spruce and torrefied spruce in a high-temperature entrained-flow reactor, are numerically examined and compared to each other using a Eulerian–Lagrangian CFD model developed based on OpenFOAM. Moreover, the sensitivities of three important operating parameters (excess air ratio, steam/carbon molar ratio, and biomass particle diameter), which vary in the range of practical significance, are also tested. The calculated results are analyzed both qualitatively and quantitatively by five indicators: isothermal profiles, char consumption rate, gas compositions, species yield, and carbon conversion along the reactor length. The obtained results show that torrefied biomass can increase the maximum temperature in the reactor as compared to its raw parent fuel. During gasification, CO, H2, and CO2 are the major species in the product gas and CH4 accounts ...

A combination of light bio-oil washing and torrefaction pretreatment of rice husk samples was proposed in this study, to investigate the impact on physicochemical characteristics and fast pyrolysis behavior. The results indicated that pretreatment removed a significant percentage of metallic species and significantly improved the fuel characteristics of rice husk samples. Fourier transform infrared spectroscopy (FTIR) analysis indicated that some organic groups decomposed by dehydration and decarboxylation reactions during the process of torrefaction pretreatment. The results of fast pyrolysis indicated that the yield and quality of pyrolysis products significantly changed with combined light bio-oil washing and torrefaction pretreatment. Pretreatment resulted in a significant increase of pH and higher heating values (HHVs) along with a reduction of the water content. Meanwhile, it can be obtained from gas chromatography/mass spectrometry (GC/MS) analysis of bio-oil that pretreatment enhanced selective py...

The use of pressurized reactors in industrial processes can improve efficiency and economics. Torrefaction is a partial pyrolysis of lignocellulosic biomass designed to result in a solid product with improved fuel properties for utilization in combustion and gasification. In this work, the influence of elevated pressure on the torrefaction of wood has been investigated. Wood samples were torrefied using a pressurized thermogravimetric reactor (PTGR) with pressures of 0.1 to 2.1 MPa. The results indicate that reactor pressure, particle size of feedstock, and wood species are all factors in torrefaction yield improvements. Torrefaction at 2.1 MPa pressure improved the higher heating value (calculated) of single-particle beech cylinders from 20.4 to 22.2 MJ kg–1, the increase ranging from 7.5 to 19% from the untreated heating value. Decomposition reactions were accelerated with pressure so that a given mass yield was realized in a shorter time. At 2.1 MPa pressure and 280 °C the time was reduced by over 60% ...

Biomass is seen as a viable alternative energy source for replacing fossil fuel. However, the inherent properties of raw biomass, including high moisture content, low energy density, hydrophilic behavior, and fibrous nature, limit its use. Thus, pretreatment becomes an important step in the path of biomass to energy conversion routes. Torrefaction is one such emerging pretreatment process, which makes biomass hydrophobic, more energy dense, and easier to grind. This paper investigates the torrefaction process in a continuous two-stage, indirectly heated rotary torrefier under the volatile gases medium. The rotary reactor is operated at different angular speeds, inclinations, and temperatures, and the produced torrefied solid product is characterized for physical and chemical compositions. The observed characteristics of the torrefied biomass produced under the volatile gases medium indicate that nitrogen supply can be avoided. Experimental results showed that torrefaction temperature has a more significan...

A comparative study of the modification of chemical composition of softwood and hardwood by torrefaction at different temperatures (150–300 °C) was carried out using microwave treatment and convective heating. The nonthermal effect was established for softwood, revealing increased aromaticity of the samples obtained under microwave treatment. A difference of the effects of microwave treatment on softwood and hardwood was revealed. In the case of softwood, both carbonization processes and unsaturation development of the matrix structure were promoted, whereas for hardwood only promotion of the carbonization processes was observed. Formation of extractable compounds as the result of wood microwave treatment was monitored, and the significant increase in formation of hydrophilic extractable compounds in the range of 210–280 °C (hardwood) and 250–300 °C (softwood) was found. The destructive changes of lignin macromolecules at relatively low temperatures (beginning with 150 °C) were confirmed by decreasing Kla...