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[Display omitted] • Biocarbons produced from five woody biomasses at 1000 °C was investigated. • Conversion behaviors and release of gases were considerably different for the tested biomass feedstocks. • Parental feedstock has considerable effects on yields and properties of solid product from the studied pyrolysis process. • The bark biocarbon has high ash content and poor mechanical properties with less ordered carbon structure. • Pyrolysis of steam exploded pellets gave the highest yield of biocarbon that has superior mechanical strength. Controlled pyrolysis experiments have been performed on five different biomass types that include birch and spruce woodchips, wood pellets, steam exploded pellets and birch bark. Biocarbons have been produced at a temperature of 1000 °C at a slow heating rate of 10 °C/min. The focus of this work was to study and compare the characteristics of the produced biocarbons. The properties of the biocarbons were evaluated in terms of proximate and ultimate analyses, ash composition, SEM-EDX, Raman, XRD, density, and abrasion strength. In addition, the gas release and element distribution across the different pyrolytic products from pyrolysis of the studied biomasses are reported. The results showed that the yield and physio-chemical properties of the produced biocarbons differ across the tested materials. The bark biocarbon has the lowest fixed carbon and carbon content, in comparison to the other tested feedstocks. On the other hand, the bark biocarbon has a considerably higher ash content compared to the other biocarbons. The presence of ash-forming elements in the bark biocarbon was confirmed by SEM-EDS and XRD analysis, which are dominated by Ca and Si. SEM analysis also revealed that biocarbon produced from the birch and spruce wood have cellular and porous structure, whereas the biocarbon produced from the wood pellet and steam exploded pellets have much more dense and compact structure. Raman analysis results indicate that birch bark biocarbon has less ordered carbon structures. Abrasion test results showed that the birch bark biocarbon has poor mechanical properties and tends to fragment and break, forming particles and fines with small sizes. The biocarbon produced from the steam exploded pellets has superior mechanical strength with the least formation of fines compared to the other studied biocarbons. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ru/NC (PVP) with uniform Ru particles were fabricated by the polyol reduction method. • Catalytic hydrotreatment of PLs were carried out under both mild and deep conditions. • Ru/NC (PVP) with PVP as the protective agent showed better performance. • The H/C ratios of the product oils from both mild and deep conditions are the highest. • The MCRT values of the product oils from both mild and deep conditions are the lowest. Catalytic hydrotreatment is one of the promising routes for upgrading pyrolysis liquids (PLs) to intermediates that can be co-fed with vacuum gas oil for FCC refinery. Among all the factors, catalysts are always crucial in catalytic hydrotreatment of PLs as hydrogenation and repolymerization reactions occur in parallel. Therefore, catalysts with sufficient hydrogenation activity are generally required to enhance the hydrogenation reaction and to inhibit the repolymerization reaction of the thermally liable compounds in PLs. Among all noble metal catalysts tested, Ru/C catalysts showed a better performance than other catalysts in terms of the oil yield and deoxygenation level. However, a clear repolymerization was observed during catalytic hydrotreatment of PLs using Ru/C catalysts, especially during mild hydrotreatment, thus there is still ample room for their activity improvement. Here, a series of Ru-based catalysts supported on nitrogen-doped carbon materials (NC) and activated carbon (AC) were prepared. The catalytic performance was evaluated for hydrotreatment of PLs in a batch autoclave (250 °C, 8 MPa H 2 , 4 h for mild hydrotreatment; 340 °C, 6 MPa H 2 , 4 h for deep hydrotreatment). The Ru catalyst supported on nitrogen-doped carbon materials, obtained by the polyol reduction method with polyvinylpyrrolidone (PVP) as the protective agent (Ru/NC (PVP)), showed a better performance (in terms of product oil properties) than the other catalysts investigated in this work, due to a good distribution of the ruthenium nanoparticles. For mild hydrotreatment the H/C ratio, O/C ratio and MCRT value were 1.42, 0.37 and 9.9 wt%, respectively. For deep hydrotreatment the H/C ratio, O/C ratio and MCRT value were 1.26, 0.16 and 4.6 wt%. The comparison with results published earlier for other hydrotreatment catalysts is satisfactory but also shows room for further improvement. GC–MS and 1H NMR results showed that the contents of thermal liable components like aldehydes (16.7 %), ketones (24.3 %) and sugars (4.0 %) in PLs were quantitatively converted under mild hydrotreatment, while phenols and alkanes significantly increased from 35.9 %, 0 % to 49.1 %, 35.3 %, respectively, especially for deep hydrotreatment compared with PLs feed. The catalyst characterization revealed that Ru/NC (PVP) with the most uniform dispersion and the smallest average particle size (1.5 nm), rendered the best performance. These findings indicate that Ru/NC (PVP) catalyst is a promising candidate for the catalytic hydrotreatment of PLs. [ABSTRACT FROM AUTHOR]

Ru 1 Co 10 /CW-2 exhibits good intrinsic activity and stability for the hydrogen evolution reaction (HER), which can be attributed to tunable lattice tensile strain and electronic interactions, while the porous carbonized wood facilitates rapid electron transfer, electrolyte transport and gas escape. [Display omitted] • Ru doping regulates the lattice tensile strain in Ru-Co bimetallic nanoparticles. • Porous structure favors electron transfer, electrolyte transport and gas escape. • Ru-Co bimetallic nanoparticles decorated on carbonized wood exhibits good HER. • The best alkaline HER overpotential was −42 mV at −10 mA/cm−2. The development of high-performance catalysts for hydrogen production originating from water electrolysis at the cathode is very crucial, but still a challenge. Here, trace Ru-doped Co bimetallic nanoparticles (named Ru x Co y /CW-z, x/y and z represent the molar ratio and total molar content of metals) were in situ decorated on carbonized wood by the vacuum impregnation and high-temperature annealing method. Ru 1 Co 10 /CW-2 demonstrates good hydrogen evolution reaction (HER) intrinsic activity with the overpotential of −42 mV (at −10 mA/cm−2) and Tafel slope of 75 mV dec−1 in a 1.0 M KOH, indicating its favorable HER reaction kinetics, and Ru 1 Co 10 /CW-2 exhibits good stability for 100 h (at −50 mA/cm−2). The good performances of Ru 1 Co 10 /CW-2 can be ascribed to the adjustable lattice tensile strain and electronic interactions, while the porous carbonized wood promotes electron transfer, electrolyte transport and gas escape. This work combines the advantages of lattice tensile strain with self-supported porous carbonized wood for HER in alkaline solution, which provides a valuable reference for synthesizing carbonized wood electrode materials with very low Ru content. [ABSTRACT FROM AUTHOR]

• Klason and native lignin in torrefied wood show similar decomposition characteristics. • Decomposition kinetics of beech wood Klason lignin is described by a three-step scheme. • Kinetic and thermogravimetric parameters of the dominant reaction step are correlated. • Three-step decomposition kinetics is also shown by lignin isolated from agricultural residues. • Reaction orders around 2–4 and activation energies of 60–150 kJ/mol testify component overlap. Lignin decomposition is of paramount importance for the formulation of biomass pyrolysis mechanisms useful for the development and optimization of the pyrolysis technology. In this study the decomposition behavior of residual lignin in torrefied woods is found to roughly coincide with that of the Klason isolated samples, which thus can be used as reliable model compounds. Previous kinetic models for the Klason and the pseudo-component lignin in beech wood are compared. A correlation is observed between the kinetic and the thermogravimetric parameters. The analysis is used as the initial basis for the formulation of a more accurate three-step kinetic model over the temperature range 300–973 K. Three main decomposition zones of the curves for beech wood Klason lignin are identified and described by activation energies of 61, 147 and 113 kJ/mol and corresponding reaction orders in the range 2–3.4. The active pyrolysis zone of Klason lignin isolated from two agricultural residues (olive pomace, wheat straw) is reached at lower temperatures and exhibits higher peak rates compared to the wood counterparts, but three- step kinetics can again be used with small variations on the estimated parameters. [ABSTRACT FROM AUTHOR]

• Impact of adding kaolin on the partitioning of chemical elements in the particulate matter (PM). • Virgin wood (VW) and grade A recycled wood (RW) were fired in a 250 kW grate boiler. • Reduction of alkali species when adding kaolin with woody biomass. • SiO 2 and Al 2 O 3 , significantly increased in the PM emissions in the presence of kaolin. • Adhesion and aggregation of particulates between airborne kaolin and the PM. The aim of the study was to investigate the impact of adding kaolin on the partitioning of chemical elements in the particulate matter (PM) when virgin and waste woody biomass fuels were fired in a 250 kW grate boiler. A comprehensive analysis of the chemical compositions of the PM has been conducted, including alkali and non-volatile species, size-fractionated mass concentrations and micromorphology images. The results showed that the PM emission levels were significantly decreased by approximately 70–76 % and 60–66 % after the addition of kaolin to virgin wood (VW) and grade A recycled wood (RW), respectively, which inhibited the partitioning of the alkali species into fine and ultrafine PM. On the other hand, the concentration of the non-volatile elements, SiO 2 and Al 2 O 3 , significantly increased in the PM emissions after the addition of kaolin due to the adhesion and aggregation of particulates between airborne kaolin and the fine and ultrafine PM. Moreover, the addition of the kaolin at 1.55 wt% showed comparable effects with that at 2.5 wt% on the chemical composition of PM emission. Furthermore, the SEM morphology suggested that KCl salts were diminished after the addition of the kaolin. These findings demonstrate the practicality of adding kaolin to mitigate PM emissions and their impacts in actual biomass combustion scenarios. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lignin's recalcitrant nature prevents significant degradation below 240 °C. • Extended reaction times may cause adsorption of degraded components. • Water recirculation led to hydrocarbon with a higher aromatic phenolic compound. • HTC industrial integration reduces power output in 1 MW. Lignin, one of the main constituents in wood and the second most abundant natural polymer, has generated great interest as a source for generating bio-based materials and fuels. The properties of lignin can be affected by various methods, for example, hydrothermal carbonization (HTC). The thermal treatment could thus be used to produce more suitable raw materials for added-value products. This work studies the relationship between the properties of the solid product (hydrochar) from HTC treatment and the choice of reaction conditions for typical HTC parameters: temperature – 200, 220, and 240 °C; residence time – 3, 6, 12, and 24 h; and water recirculation– 40, 60 and 80 vol% of process water (PW). The chemical composition of the hydrochar (HC) generated from industrial kraft lignin is evaluated along with their thermal degradation behavior under inert and oxidizing conditions by thermogravimetry. Compositional variations led to changes in characteristics such as volatile, fixed carbon, and ash content, varying to a greater or lesser extent according to the operational parameters. Although an increase in the temperature of the process leads to an increase in the caloric value of the hydrochar, this temperature change also leads to a slight decrease in the thermal stability of HC in oxidizing atmospheres. Additionally, the integration of a lignin HTC treatment process in a large modern Nordic pulp mill is presented, indicating minor disturbances when adding an HTC unit to the plant. [ABSTRACT FROM AUTHOR]

[Display omitted] • Activation of bio-oil impregnated wood with ZnCl 2 forms more activated carbon (AC) via condensation. • Impregnation of bio-oil hinders infiltration of ZnCl 2 and reduces overall specific surface area. • Activation of bio-oil impregnated wood with K 2 C 2 O 4 generates more pores but diminishes AC yield. • Additional aliphatic structures from impregnated bio-oil facilitate pore formation via intensified cracking with K 2 C 2 O 4. • More mesopores from impregnating bio-oil render AC superior performance of phenol adsorption. Bio-oil contains abundant aliphatic organics, which can be used to impregnate a biomass feedstock for increasing aliphatic content, as aliphatics are important for pore development in activation. Herein, impregnation of homologous bio-oil to spring jasmine wood (SJW) and further activation of the impregnated sample (SJW-oil) with ZnCl 2 or K 2 C 2 O 4 were conducted, aiming to explore another alternative outlet for application of bio-oil. The results showed that the impregnated bio-oil increased yield of activated carbon (AC) by 29.9 % (on SJW basis) in activation with ZnCl 2 , due to promoted condensation of organics from the impregnated bio-oil. Nevertheless, the specific surface area was reduced from 2098.5 m2g−1 in activation of SJW only to 1602.1 m2g−1 from SJW-oil, as the impregnated bio-oil suppressed infiltration of ZnCl 2 to internal structures of SJW. However, more mesopores were generated in AC-Oil-ZnCl 2 (85.9 %) than in AC-ZnCl 2 (92.5 %), originating from activation of organics in impregnated bio-oil. K 2 C 2 O 4 could easily crack organics in the impregnated bio-oil and in SJW, increasing specific surface area from 1152.2 m2g−1 in AC-K 2 C 2 O 4 to 1283.4 m2g−1 in AC-Oil-K 2 C 2 O 4. In-situ IR characterization showed formation of additional aliphatic structures from the impregnated bio-oil and also intensified cracking reactions, favoring pore developing but diminishing AC production. The impregnated bio-oil also rendered the AC with superior performance for phenol adsorption but lowered environmental impact of the activation process. [ABSTRACT FROM AUTHOR]

• A new apparatus enabling coupled convective and radiative heating is built. • Glowing and flaming autoignition of 5 and 15 mm wood is experientially studied. • A new glowing ignition temperature correlation is proposed. • Da and heat loss ratio are indictors of flaming ignition in gas and solid phases. • An ignitibility map identifying ignition and nonignition regimes is drawn. Autoignition of solid fuels driven by coupled convective and radiative heating is frequently encountered in fires, whereas its controlling mechanism is rarely revealed. To challenge this issue, autoignition tests of 5 and 15 mm thick cylindrical wood samples were conducted using a newly developed apparatus enabling coupled convective and radiative heating. The total heat flux imposed on wood was maintained at 25 kW/m2, while the fractions of the two heating components changed as the airflow velocity and temperature varied in the ranges of 0–1.51 m/s and 298–473.3 K. Glowing ignition occurred in all scenarios except for one case due to enhanced heat loss and declined radiative heating. Flaming ignition was observed in all conditions except for 298 K airflow temperature. Four stages were identified during flaming combustion: a preheating and deformation stage, a glowing combustion stage, a coupled glowing and flaming combustion stage, and an extinction stage. Compared to 5 mm samples, the surface temperature rise of 15 mm wood was significantly delayed due to its thermally thick nature. By fitting experimental data, a new formula was proposed to correlate glowing ignition temperature with radiative heat flux, airflow velocity, and airflow temperature. Both glowing and flaming ignition times were affected by airflow and radiative heating in a complex manner, and their values to the power of −0.5 approximately linearly depended on radiative heat flux. Damköhler number and nondimensional heat loss ratio were employed to quantitively analyze the flaming ignition propensity. Meanwhile, an ignitability trend map identifying the flaming and non-flaming ignition regimes was drawn. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple electrodeposition process is performed to obtain highly efficient catalysts. • A nanoflower-like NiFeCo catalyst is developed on carbonized wood. • Effects of H+ concentration and electrodeposition time on catalyst morphology are discussed. • Catalyst reveals 37 mV at 10 mA cm−2 and 298 mV at 1000 mA cm−2 for HER. The development of cost-effective, simple, and highly active catalysts for electrochemical water splitting in alkaline electrolytes to produce renewable source H 2 is critical to solve the environmental pollution and energy crisis. In this study, a series of nanoflower-like NiFeCo/CW catalytic electrodes were prepared by a facile one-step dynamic hydrogen bubble template (DHBT) method for electrodeposition on carbonized wood (CW), which have excellent HER performance. By reasonably investigating the effects of H+ concentration and time, a catalyst with ideal deposition results was obtained. In 1 M KOH solution, the prepared NiFeCo/CW-450 catalyst exhibits a small overpotential of 37 mV to achieve a current density of 10 mA cm−2, and still possess a satisfactory low overpotential when a larger current density is reached (η 400 = 238 mV, η 1000 = 298 mV). Furthermore, NiFeCo/CW can keep structure and catalytic performance stable after long-term test. The remarkable HER performance results from the unique nanoflower electrode structure that is uniformly dispersed on CW to fully expose the active site. As a result, this work will provide new inspiration and strategy for the preparation of novel simple, inexpensive and efficient electrocatalytic hydrogen evolution electrodes using earth-abundant resources. [ABSTRACT FROM AUTHOR]

• Comprehensive investigation into pyrolysis kinetics of different wood samples using DAEMs. • High model fit accuracy exceeding 98% demonstrated in all three distribution models. • Identified increased cellulose content in naturally aged wood, influencing resource utilization. • Weibull model exhibited superior predictive power in capturing the complexities of pyrolysis process. • Recognition of key parameters ln A and E as influencers over accurate DAEMs establishment. Recycling and reusing biomass is an effective strategy to enhancing bioenergy utilization and minimizing resource waste. This study aims to investigate the pyrolysis mechanisms and kinetic predictions of typical Cypress Wood (CW), Fir Wood (FW), Old Cypress Wood (OCW), and Old Fir Wood (OFW) samples, Distributed Activation Energy Models (DAEMs) were employed to fit the pyrolysis processes of the two types of wood before and after natural aging. For this purpose, three activation energy distributions, Gaussian, Logistic, and Weibull, were selected to investigate the optimal reaction function model. Each model was simultaneously fitted the extracted experimental α and d α /d T data at three heating rates. Important features and relationships of the models were discussed, and the best model was chosen. Additionally, the isoconversional method was used to validate the optimal model, and the sensitivity of the best parameters were estimated. The result shows that the Weibull distribution is more effective in predicting the trend of the conversion rate against the activation energy. In addition, the most obvious effects of the pre-exponential factor and activation energy on the pyrolysis process. [ABSTRACT FROM AUTHOR]

• The positive interactions between semi-coke and biomass will promote the combustion of semi-coke in advance during co-combustion. • Blending biomass can decrease the NO emission of semi-coke effectively in fluidized bed. • The ash deposition problem may occur when more than 20% corn stalk and rice stalk are blended. • The optimal blending ratios of corn stalk and rice stalk are considered as 20% to co-combust with semi-coke, while the appropriate blending ratio for pine wood is 40%. In order to realize the integrated utilization of semi-coke (SC) and biomass, the co-combustion behavior of SC and three typical biomass (corn stalk (CS), rice stalk (RS) and pine wood (PW)) was experimentally studied in terms of combustion, NO emission and ash characteristics. The results of thermogravimetric (TG) analysis show that the positive interactions between SC and biomass mainly occur at the later combustion stage of blends, leading to the combustion of SC in advance. Based on the ignition and comprehensive combustion indexes, the optimal blending ratios of CS and RS are considered as 20%. The co-combustion experiments conducted at the biomass blending ratio of ≤40% in an electrical-heated fluidized bed rig also prove that the combustion performance of SC can be improved by biomass, and the NO emission decreases with the biomass blending ratio. The ash deposition problem should be paid attention when more than 20% CS or RS is blended, which is related to the alkali aluminosilicates and K 3 Na(SO 4) 2 in the fly ash of SC/CS and SC/RS blends, respectively. Meanwhile, the effect of PW in this regard is limited due to its extreme low ash content. In summary, the blending ratio for CS and RS is suggested as 20% when co-combusting with SC, while the appropriate PW blending ratio is 40%. The achievements of this study are conducive to the clean and high-efficiency utilization of semi-coke and CO 2 emission reduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • The interaction has insignificant effects on biochar without the presence of potassium salts. • More C-O-K bonds are formed after the interaction for biochar of wood doped with K 2 CO 3 /K 2 SO 4. • The interaction generates more active sites and decreases the biochar order. • Insignificant additional release of potassium after the interaction. Co-gasification of biomass and coal has many advantages. However, the volatile-char interaction during co-pyrolysis, which is the first step of co-gasification, significantly changes the properties and the structure of biochar, thus affecting gasification. The present work investigated the effect of the interaction between the volatile from a coal and the biochar of K-salt-doped (K 2 CO 3 , K 2 SO 4 and KCl) pine wood in a lab-scale, fixed-bed reactor at 600, 700 and 800 °C to understand how the occurrence mode of inorganic K in biomass alters the volatile-char interaction during co-pyrolysis. The volatile-char interaction has insignificant effects on the biochar of pine wood without the doping of K salts while it has significant effects on the biochar of K-salt-doped pine wood, especially for K 2 CO 3 and K 2 SO 4. The volatile-char interaction significantly increases the formation of C-O-K bonds, the content of oxygen containing compounds and the aromaticity of the biochar for K 2 CO 3 -doped and K 2 SO 4 -doped pine wood. In contrast, the evident presence of C-O-K bonds can only be found for KCl-doped pine wood at 800 °C after the volatile-char interaction. The increase in the pyrolysis temperature and the presence of the volatile-char interaction make the carbon structure of the biochar of K 2 SO 4 -doped and KCl-doped pine wood less ordered and generate more active sites. However, although the char order is lower and the number of active sites is higher for the biochar of K 2 CO 3 -doped pine wood than for that of K 2 SO 4 -doped and KCl-doped pine wood, the volatile-char interaction has insignificant effects on improving the activity of its biochar. Lastly, the volatile-char interaction causes insignificant additional release of K from the biochar. This may indicate that significant amounts of stable C-O-K bonds have been formed in the biochar to retain K. [ABSTRACT FROM AUTHOR]

[Display omitted] • One-step pyrolysis of sawdust and Na 2 S mixture in a muffle furnace generated SBC. • SBC300 exhibited 96.4 % Hg removal efficiency and 54.34 mg/g adsorption capacity. • SBC's sulfur groups and Hg(II) form HgS, enhancing Hg removal. • SBC removal has a high cost-effectiveness ratio of USD1.74/1 g Hg. • A higher cost-effectiveness ratio is indicative of future biochar production. Biochar is an effective agent for removing mercury (Hg(II)) from industrial wastewater. However, its cost is usually high which restricts large-scale applications. It is urgent to perform techno-economic assessments for quantifying the cost-effectiveness ratio of biochar material, which would produce cheaper, more effective, and feasible biochar to push it from lab to market. In this work, sodium sulfide (Na 2 S)-modified biochar (SBC) was produced with a single pyrolyzing step by mixing sawdust with Na 2 S. Hg removal efficiency, purifying mechanism, and potential costs were compared between SBC and unmodified wood biochar (UBC). Results indicate that SBC prepared at 300 °C (SBC300) had the highest Hg removal efficiency, 96.4 %, which was well described by the pseudo-second-order model. SBC300 had a maximum adsorption capacity of 54.34 mg/g. Incorporation with sulfur-containing functional groups and precipitation on biochar surface accounted for most Hg removal. Techno-economic assessments proved that SBC300 had a high cost-effectiveness ratio, costing USD 1.74/1 g Hg for removing from wastewater, and is an alternative for industrial production and large-scale applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Online alkali measurement during gasification of wood with fresh bed material mixtures. • The main elements in bed material migrate to the char surface and affect gasification. • Dolomite affects pyrolysis and gasification due to deposition and element migration. • Si-containing materials inhibit gasification and alkali release in the final stage. • Residual Na in sea sand and alumina moves to char surface and catalyzes gasification. Bed materials provide efficient heat transfer and catalytic function in the thermochemical conversion of biomass, but their interactions with the fuel remain incompletely understood. In this study, the effects of bed materials on alkali release and fuel conversion during wood pyrolysis and CO 2 gasification are investigated by online alkali detection combined with thermogravimetric analysis. The investigated bed materials include silica, sea sand, alumina and the natural ores olivine, ilmenite and dolomite. Only dolomite has a significant effect on fuel mass loss and alkali release during wood pyrolysis, while all bed materials influence char reactivity and alkali release during gasification. Sea sand, alumina and dolomite enhance the char gasification during the whole or most of the gasification process, which is related to alkali migration from the bed materials. All bed materials affect char reactivity and alkali release when the conversion approaches completion, and small amounts of some bed materials reduce the alkali release by an order of magnitude. The findings can be understood based on the chemical composition of the different materials. Silicon-rich materials reduce the levels of catalytically active alkali by formation of stable alkali silicates, and a similar explanation applies for ilmenite that captures alkali efficiently. Magnesium and calcium in contrast promote alkali release through their influence on alkali silicate chemistry. Analysis of char surfaces using scanning electron microscopy with energy dispersive spectroscopy indicates that low amounts of several elements are transferred from the bed material to the char where they may be directly involved in the char conversion process. The transferred elements are specific for each bed material and relates to their chemical composition. Mechanisms for material exchange between bed material and char are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Smouldering-to-flaming transition in solid wood was observed at 830 °C under airflow. • Fully penetrated vertical char crack or pre-perforated hole promotes the StF transition. • External airflow made solid wood smouldering transition to flaming easier and faster. • StF transition was an autoignition of a pyrolysate-oxygen by hot smouldering surface. • Numerical model reproduces the StF transition of solid wood under external airflow. The shrinkage, deformation and cracking of the wood affect their smouldering and flaming dynamics, but the scientific understanding is still limited. We study the burning behaviours of disc wood samples with a diameter of 60 mm and thicknesses of 5–40 mm under external airflows up to 6 m/s. Results show that the smouldering-to-flaming (StF) transition can be observed at about 830 °C under external airflow, which is caused by the interactions between smouldering-induced crack and environmental airflow. The fully penetrated vertical char crack or pre-perforated hole promotes the StF transition because of (1) enhanced radiation between the two smouldering surfaces and (2) greater air supply under the chimney effect. As the wind velocity increases, both the smouldering surface temperature and crack size increase, so the transition to flaming becomes faster. For a larger wood thickness, a larger airflow is required to generate the crack and cause a StF transition. A numerical model is proposed to investigate the volatile convection and flaming ignition. Numerical analysis reproduces the StF transition, as an autoignition of a pyrolysate-oxygen mixture promoted by hot smouldering surfaces. The numerical model further reveals the effects of smouldering temperature and cross wind on the StF transition. This work deepens the understanding of the StF transition dynamics and provides insights into the wildfire ignition dynamics and fire hazards of timber structures. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Resolution-enhanced KMDs using fractional base units are extended to carbonaceous samples. • Mass spectra of wood and coal extracts become compositional maps with a KMD analysis. • Consecutive data processing with slicing and zooming produces informative KMD plots. • Highly confident assignments of ion series and comparison of datasets are made possible. • Improvements of the KMD-based processing are compiled into an advanced KMD toolkit. Abstract The Kendrick mass defect (KMD) analysis conveniently turns a complex high-resolution mass spectrum into a compositional map with informative clustering of points depending on the elemental composition of the associated ions. It has nevertheless been left unchanged for thirty years with the use of chemical moieties such as methylene as base units for the computation of "regular" mass defects displayed in condensed plots regardless of the samples. The concept of "resolution-enhanced" KMD analysis using the mass of the repeating unit divided by an integer as the new fractional base unit has been recently introduced for the computation of expanded plots from polymeric mass spectral data with a dramatically improved separation of ion series. This user-friendly data processing is extended to the case of carbonaceous samples for the first time with the analysis of water-insoluble organic microspheres recovered from the hydrothermal extraction of wood and coals. In a didactic discussion with illustrative examples, the direct resolution-enhanced KMD analysis, the consecutive resolution-enhanced analysis of a part of a regular KMD plot or the systematic slicing of plots in a multistep procedure are shown to produce simple resolution-enhanced KMD plots or resolution-enhanced zooming from complex mass spectra. The combination of these techniques in a unique "advanced KMD analysis" toolkit is expected to revolutionize the data processing of high-resolution mass spectra with unprecedented separating and unraveling capabilities. [ABSTRACT FROM AUTHOR]

Small-scale batch combustion of wood is a major source of fine particles, black carbon emission and polycyclic aromatic hydrocarbons in Finland. The mass and chemical compositions of batch combustion emissions are known to be highly time-dependent. In this study, the gaseous and particulate batch combustion emissions of three European wood species (beech, birch and spruce) were quantified in detail with an extensive set of online analysers, including a soot particle aerosol mass spectrometer (SP-AMS) for real-time detection of particulate chemical composition. Ignition and a new batch addition on top of glowing embers were identified as the primary low temperature events during which both particulate and gaseous organic emissions peaked. The flaming combustion created high temperature conditions and produced increased emissions of refractory black carbon (rBC) and PAHs. The residual char combustion phase was characterized by low particulate mass emission consisting mainly of alkali salts and elevated concentrations of gaseous organic emissions and CO. Overall, hardwood species (beech and birch) had the highest PM 1 emissions, and the difference between the lowest average emission (spruce) and the highest (birch) was more than 3-fold. The increasing combustion chamber temperature during sequential combustion of wood batches was found to decrease the carbonaceous fraction of the PM as well as OC/EC ratio, as the result of more efficient secondary combustion. [ABSTRACT FROM AUTHOR]

In recent years, the world has witnessed a rapid rise in waste production and energy demand, which has increased interests in waste to energy processes, particularly the co-pyrolysis of wood and plastic waste. Nonetheless, for plastic waste, most research studies narrowly focus on polyolefins because of their abundance in waste streams and their high oil yields from pyrolysis. In this paper, we study the co-pyrolysis of non-polyolefins – polystyrene (PS) and polyvinyl chloride (PVC) – and poplar wood (PW), in order to investigate the synergistic effect of PS and PVC content on product yield, gas specie yield and heating value. The experiments were performed using a fixed-bed reactor, heated to 750  ° C at a rate of 20  ° C/min under nitrogen atmosphere. Our results show that PVC has a large positive synergy on char yield with a maximum value of 8 wt% at 30 wt% PVC content, whereas PS only showed a slightly positive synergy (2.5 wt% maximum). Concerning oil and gas production, PS provides a small synergy. However, PVC showed a significant positive synergy on oil yield with a maximum value of 11 wt% at 50 wt% PVC content, which was linked to a strong negative synergy in gas production. Regarding gas specie yields, the addition of PS led to positive synergies in the formation of H 2 , CH 4 , CO and CO 2 , although insignificant interactions were observed for C x H y compounds. Furthermore, by comparing the distribution of chloride species in the products of co-pyrolysis with PVC, using experimental and theoretical methods, we discovered that the negative synergy in HCl yield observed was mainly due to the dissolution of HCl in the water fraction of the condensed oil phase, rather than the formation of chlorinated organic compounds, as suggested in previous literature works. Our study therefore consolidates the understanding of the synergistic interactions between wood, PS and PVC co-pyrolysis, under conditions that favour gas production. [ABSTRACT FROM AUTHOR]

The impact of biochar modification on its behavior towards the adsorption and cracking of naphthalene (in a mixture naphthalene/toluene) as tar model compound has been investigated. Both tar adsorption and cracking may be considered alternative tar cleaning technologies which enable its further energetic use. Biochars were produced using different feedstocks and process conditions to tune their physico-chemical and morphological properties. Beech wood, representative of woody biomass, and almond shell and rice husk, representative of agricultural residues, were used. Furthermore, beech wood was also washed with deionized water and doped with KCl and FeSO 4. Biochars were produced at 700 °C under several atmospheres (pure N 2 and mixtures of N 2 , CO 2 , H 2 O, and CO), resulting in different physico-chemical properties and thus naphthalene adsorption and cracking behavior. Naphthalene adsorption experiments were performed at 250 °C and naphthalene cracking experiments were carried out at 750 °C and 850 °C. The performance of the investigated biochars towards naphthalene adsorption and cracking depended strongly on the production conditions, with biochars produced under reactive atmosphere (including N 2 , CO 2 , and H 2 O) yielding the best behavior. For naphthalene adsorption, an easily accessible high surface area seemed to be the dominant parameter determining the biochar adsorption capacity. Wood doping with FeSO 4 resulted in biochars with higher adsorption capacity due to the formation of mesopores and Fe clusters within these mesopores that could likely enhance the adsorption capacity. In the case of naphthalene cracking, biochars produced under reactive atmosphere (G1) with untreated wood and H 2 O-washed wood showed the highest naphthalene conversion. In this case, the specific surface area was not the most relevant parameter determining the biochars performance. Wood doping with KCl had a negative impact on naphthalene cracking, while wood doping with FeSO 4 impacted positively when the biochar was produced in N 2 atmosphere, but negatively when produced in reactive atmosphere (G1), likely due to the oxidation state of Fe. Biochars from agricultural residues and woody biochars, produced under the same conditions, performed similarly. • Combination of biomass pretreatment and conversion conditions resulted in significantly different porous structures. • Doping of the biomass with FeSO 4 led to the formation of mesopores. • Adsorption behavior of naphthalene depended on the available surface area and its accessibility. • Biochar structure changed after naphthalene adsorption or cracking. • High microporosity did not ensure a good naphthalene adsorption or cracking capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Raman mapping technology was developed to study micro-structural evolution. • Combined Raman/TG/BET analysis enables a quantitative structural analysis. • Cellulose and lignin contribute to mesopore and micropore formation respectively. Characterizing the pore structure evolution of biomass-derived carbon during processing and exploring the relationship between the porous carbon structure and the intrinsic micro-structure of biomass precursor are of great importance to advance the knowledge of pore creation/evolution mechanism and manufacture demanded pore structures by controlled processing. So far, the manipulation of pore structure still heavily relies on trial-and-error approach due to the lack understanding of the relationship between precursor structure/composition and the pore evolution during processing. In this work, the micro-structural evolution across the multi-layered wood tracheid in carbonization and oxidation processes was revealed by Raman mapping which can provide a unique insight into the pore structure evolution of carbon materials. The different degrees of graphitization enable the differentiation of carbonized forms of lignin and cellulose by Raman mapping and thus quantify the changes of both species during carbonization and oxidation. It is revealed that micropore formation is more related to the degradation of lignin and mesopore formation is closely associated with cellulose. The diffusion of reactive gas through the multi-layered wood tracheid and the corresponding reactions occurred along the diffusion path create the comprehensive porous channels. This work provides a new and convenient method to get a comprehensive understanding of biomass structure/composition in related to the pore structure evolution and allows a more specific regulation of pore structure in biomass-derived porous carbon materials. [ABSTRACT FROM AUTHOR]

• The ignition point of fresh pine is higher than that of natural aging pine. • Starink method was used to evaluate the kinetic parameters of pine combustion. • Natural aging degrades the burning performance of pine wood when burned. Given the long-term effects of natural ageing, the wooden structure and combustion performance of ancient buildings have changed. Therefore, studying the combustion characteristics of naturally aged pine (NAP) trees may help provide a basis for the numerical simulation of fires in ancient buildings. In this study, NAP and fresh pine (FP) with a natural ageing duration of approximately 100 years were selected as samples. The morphology, thermal weight loss process, exothermic characteristics, and combustion characteristics of these two types of pine were examined through scanning electron microscopy, synchronous thermal analysis, and cone calorimetry. In addition, the thermodynamic parameters of both the samples were analysed and evaluated. The results indicated that the natural ageing effect resulted in pore enlargement and severe damage to the cell structure of pine wood. Compared with FP, the ignite of NAP decreased by 15.2 °C, and the heat dissipation of NAP during oxidative combustion decreased by 0.26 kJ/g. In addition, the average apparent activation energy of NAP during pyrolysis combustion increased by 22.03 kJ/mol compared with FP, but the overall combustion performance decreased. During the combustion process, NAP tended to form a dense carbonisation layer, resulting in a decrease in the heat release rate, total heat release rate, flue gas release rate, and CO and CO 2 release rate during combustion. [ABSTRACT FROM AUTHOR]

The available data on intrinsic kinetic parameters of wood char combustion is limited in the literature. The intrinsic reactivity of porous char particles reflects the variance in the pore structure resulted from various compositions of parent biomass or coal fuels. In this study detailed kinetic models for calculating the intrinsic reaction rate and the Arrhenius parameters in two combustion zones are developed for the char combustion. The influence of the parent fuel composition and the thermal treatment on the char oxidative reactivity observed on the char surface area and particle density are explored through a mathematical model of the char service area and density. A higher reactivity of the wood pellets than coal and enhanced reactivity with the increasing pyrolysis temperature were observed as well. [ABSTRACT FROM AUTHOR]

• Experiments on overfeed packed bed combustion of wood particles. • Sample particles attached to thin rods to follow movement and allow removal for analysis. • Technique yields detailed information on particle shape and density changes under bed conditions. This paper introduces a simple technique for sampling individual fuel particles at various stages in overfeed packed bed combustion. A particle is secured to the end of a thin stainless steel rod, which is then used to track the motion of the particle and to remove it from the bed for sampling at the desired time. The particles so tracked provide a record of changes in mass, volume, density, and individual dimensions as combustion proceeds in the bed. Results of a number of experiments of this sort on the packed bed combustion of parallelepipedal wood particles are presented, which among other things show that particle shrinkage during pyrolysis is generally – but not always – largest along the direction of the wood grain and less in the cross-grain directions. The "tracker rod" technique has the advantage over single particle experiments in a furnace that the particles are exposed to the varying and non-uniform conditions in the actual packed bed of fuel; it is, however, only suited to fixed beds, not fluidized or moving beds. [ABSTRACT FROM AUTHOR]

• Pyrolysis of beech wood particles in a bubbling fluidized bed was investigated. • Effect of beech wood particle shape on their pyrolysis conversion was studied. • A high-precision scale was used to measure the beech wood mass evolution. • Pyrolysis time is proportional to the particles heat transfer characteristic length. • A simple shrinking model proposed can properly predict the effect of particle shape. The effect of biomass particle shape on the conversion of beech wood during pyrolysis in a bubbling fluidized bed (BFB) was experimentally quantified. A lab-scale BFB installed on a high-precision scale was used to characterize the mass loss of the biomass particles immersed in the bed. The scale could monitor the mass loss of the beech wood particles while moving freely inside the bed, which was operated at 2.5 times the minimum fluidization velocity of the bed material employed. The tests were performed at 500 and 600 °C using beech wood particles of the same mass, but different in shape. All particles used were cylindrical in shape, with the same mass, and differing in their aspect ratio, analyzing particles from typical biomass chips to standard biomass pellets. The experimental results indicate that the velocity of pyrolysis for the different particles is proportional to the characteristic heat transfer length of the particles, with pyrolysis times ranging from 27 to 53 s for a bed temperature of 600 °C and from 43 to 85 s for a bed temperature of 500 °C. The minimum pyrolysis time was obtained for particles with a diameter of 20 mm and a length of 2 mm pyrolyzing in a bed at 600 °C, whereas the maximum pyrolysis time corresponds to particles of 10 mm in diameter and 8 mm in length converting in a bed at 500 °C. Estimations of the conversion time obtained from a Shrinking Unreacted Particle Model (SUPM), assuming a constant density and reducing volume of biomass during conversion, and a Uniform Conversion Model (UCM), considering uniform volume and decreasing density of biomass along the conversion process, were compared to experimental measurements of the conversion time. Qualitative agreement was found between the experimental values and the predictions of the conversion time from the simplified models, obtaining in all cases conversion times proportional to the characteristic length of heat transfer of each particle shape. [ABSTRACT FROM AUTHOR]

Due to the increasing utilization of wood-based raw materials, there is growing interest in the use of alternative biomass raw materials for biomass pellet production. However, the utilization of these new raw materials may significantly increase particle emissions from small boilers, which can cause adverse effects on human health and the environment. In this study, the effects of biomass raw materials on particle and gaseous emissions and ash behavior were studied in a real-world operating 500 kW reciprocating grate boiler. The studied fuels were pellets, which consisted of softwood stem, bark, peat and various mixtures of these materials. The emission factors of the fine particles (PM 1 ) ranged between 11 and 26 mg/MJ, which were primarily determined by alkali metal release from the fuel. The co-firing of peat with wood significantly decreased PM 1 emissions. This decrease was observed because of the high silicate content in peat, which led to alkali silicate formation during co-combustion and, consequently, the retention of alkali metals in the bottom ash. In contrast, the release of trace metals into the fine particle fraction was independent of the fuel ash composition with the exception of Cu. The emissions of As, Cd, Pb, Tl, and Zn were linearly dependent on their concentrations in the fuel. The highest release rates, which were between 40% and 60%, were observed for zinc and lead. Zinc formed the majority of the total PM 1 heavy metal emissions, and zinc emissions were especially high in bark combustion. On the basis of these results, fuel composition based indexes were derived for predicting particle emissions. The results highlight the importance of both the fuel alkali metal content and alkali metal/silicate ratio in the formation of fine particles with fuels that consist of woody biomass and peat. [ABSTRACT FROM AUTHOR]

[Display omitted] • Densified fuel does not significantly degrade environmental performances of the stove. • The cylindrical geometry is preferable to the cubic one. • Briquette compaction is a key parameter for combustion conditions. • Briquette composition has an impact: avoid bark and biomass of "waste" type. A panel of twenty commercial briquettes representative of the French market was set up with the different actors of the French densified log industry. The selected briquettes were characterized via the determination of their water and ash content, their ultimate and elemental composition and their heating value. Pollutant emission factors during the combustion of the briquettes were evaluated in real conditions in a domestic stove with natural draught. Gaseous pollutants like CO, CO 2 , NOx, SO 2 and THC (Total HydroCarbons) were monitored. Particulate emissions in mass (TSP) and number (PM 2.5) were also measured. Briquettes characterizations showed that the majority of the data determined in laboratory are in agreement with the one announced by the producers. Moreover several briquettes are in agreement with limitation established by the EN ISO 17225 standard. Combustion tests showed that the use of densified fuel instead of traditional log does not lead to a significant degradation of the environmental performances of the stove. Some briquettes present emission factors close to the one measured with traditional wood log. Several recommendations concerning briquettes characteristics were drawn from this study. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-pyrolysis polygeneration of heavy bio-oil and pine sawdust is studied. • Light bio-oil is used to leach pine sawdust to remove ash and alkali metals. • Leaching pretreatment of pine sawdust improves the mass yield and quality of bio-oil. • Co-pyrolysis of pine sawdust and heavy bio-oil has obvious synergistic effect. • The sum of energy yield of biochar and bio-oil is more than 80%. The liquid products obtained from pyrolysis of biomass include light bio-oil and heavy bio-oil. The former contains large amounts of water and organic acids, while the latter contains more of pyrolysis lignin and phenolic compounds. Herein, a new method of pine wood co-pyrolysis polygeneration along with bio-oil recycling was proposed for upgradation of pyrolysis products. Light bio-oil was used for leaching of pine sawdust, instead of the traditional acid leaching pretreatment, followed by its co-pyrolysis with heavy bio-oil. The synergistic effect during co-pyrolysis polygeneration was studied. Results showed that leaching pretreatment could effectively remove the alkali metals (95.6 % of K) from pine wood, which improved the quality and energy yield of bio-oil during the subsequent pyrolysis. The maximum increase in mass yield and energy yield of bio-oil were 6.7 % and 7.1 %, respectively. The co-pyrolysis of pine wood and heavy bio-oil had obvious synergistic effect, which increased the mass yield of biochar (maximum increase: 3.3 %) and pyrolysis gas, while reducing the water and relative acids contents of bio-oil and improving the contents of CO and C 2+ gases in the gaseous products. The maximum differences between the experimental and theoretical HHVs of biochar and bio-oil were 1.01 MJ/kg and 1.94 MJ/kg, respectively. Thus, this method provides a potential way to classify and utilize light and heavy components of bio-oil and also provides a basis for biomass pyrolysis polygeneration technology. [ABSTRACT FROM AUTHOR]

• Beech wood torrefaction at different conditions using comprehensive instrumentation. • Heat treatment heterogeneity can be assessed by water vapour sorption measurements. • The data-set allowed a complete computational code to be validated. • Torrefaction schedule should be adapted to the particle size and its initial MC. • Treatment conditions meeting users' expectations found by probabilistic optimization. This paper uses a comprehensive computational model to propose optimal wood torrefaction conditions by probabilistic optimization. Its main outcome is to propose tailor-made heat treatment conditions (temperature levels-duration of mild pyrolysis at temperature levels ranging from 200 to 300 °C) to meet users' expectations in terms of overall mass loss, duration and homogeneity of treatment. To this purpose, beech wood boards were torrefied with a usual 3-steps treatment schedule (drying, heating and cooling) under contrasting configurations in a well-instrumented device. The heterogeneity of the treatment within the wood sample was assessed through X-ray attenuation profile and water vapour sorption isotherm. These results allowed the model to be validated. In particular, it predicts the evolution of the mass loss and internal temperatures with good accuracy, including the temperature overshot. The results highlight the need to adjust the heat treatment schedule to each input parameter such as the wood piece dimensions and its initial moisture content or density, in order to limit the effect of exothermic reactions. The torrefaction model was then embedded in a probabilistic optimization process. A case study demonstrates the ability of the model to propose an alternative 3-steps treatment schedule able to reach the target mass loss while controlling the temperature overshot within the wood piece. [ABSTRACT FROM AUTHOR]

• Effect of HTC on softwood and hardwood was compared. • Model-free kinetic prediction was performed. • Cellulose structure was activated firstly and then decomposed with HTC temperature. • Pyrolysis mechanism changed from diffusion model to reaction order model. • Pore structure changed more significantly for pinewood after HTC. Hydrothermal carbonization (HTC) pretreatment is an effective method to upgrade the low quality biomass properties. In this work, the pinewood (PIW) and poplar wood (POW) were selected to study the effect of HTC (180–240 °C) on woody biomass structure and reactivity. The results showed that the slight and moderate HTC can make the cellulose structure more ordered, while the severe HTC leaded to the decomposition of cellulose structure. The mesoporous specific surface area and pore volume increased with the HTC temperature, and the pore structure of PIW was more developed than that of POW. The slight HTC had little effect on cellulose structure and the diffusion effect played the dominant role. The severe HTC increased the relative content of lignin and the pyrolysis followed the high order reaction model. The model-free method was used to determine the relationship between T - β - X , and the specific temperature T HTC / T raw was calculated. The T HTC / T raw value of PIW and POW located in the range of 0.938–1.340 and 0.924–1.422, indicating the HTC pretreatment had great effect on POW pyrolysis reactivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Different pretreatments were differently affected biogas production. • The maximum methane was obtained from organosolv pretreated spruce leaves. • Phosphoric acid was significantly increased methane yield from the fruits. • Phosphoric acid and organosolv were the most effective processes for lignin removal. • Opened up structure, crystallinity reduction, and delignification were detected. Spruce is the most resistant type of lignocellulosic material to anaerobic digestion. Different parts of spruce tree, i.e., leaves, wood, branches, bark, fruit, and mixtures of these parts, were pretreated using the leading pretreatments, i.e., concentrated phosphoric acid, dilute sulfuric acid, and ethanolic organosolv pretreatment, to improve biogas production. The pretreatment effects on methane yield from both solid and liquid fractions of the pretreatments were evaluated. Different parts of the tree showed different behaviors. The maximum methane yields from the pretreated solids were obtained after phosphoric acid pretreatment, which yielded methane yields of 211.7 and 225.5 mL per g volatile solids (VS) of pretreated spruce leaves and mixture, respectively. The improvements were related to opened-up structure, crystallinity reduction, and delignification. Sulfuric acid pretreatment improved biomethane yield from liquids, but not solids. Moreover, organosolv pretreatment improved the yield from solids, but not wood, bark, and the mixture. The maximum methane production yield was 245.3 NmL CH 4 /gVS which was obtained from the organosolv liquor of spruce leaves. The highest overall methane production (252.9 L per Kg) was gained from the whole solid and liquid fractions from organosolv pretreatment of leaves. This methane yield corresponded to 2.4-fold improvement compared to that of the untreated leaves (107 NmL CH 4 /gVS). Thus, leaves and branches are less recalcitrant parts and do not need severe pretreatment, while bark and wood are the most recalcitrant parts and required severe pretreatment like concentrated phosphoric acid. Moreover, the mixture of all parts also required severe pretreatment for efficient biogas production. [ABSTRACT FROM AUTHOR]

• Combustion of binary mixtures of particles of different sizes and shapes. • Experiments compared with numerical model. • Mean particle size and sphericity make model agree well with experiment. • Model must include particle overlap and wood grain orientation. This paper presents the results of experiments and numerical modelling on the quasi-steady overfeed combustion and gasification of binary mixtures of fuel particles of different sizes and shapes in a fixed bed. The particles used comprised six different parallelepipedal shapes cut from wood, which were combined to give various binary mixtures. Physically appropriate definitions of average quantities for a packed bed are the volume surface or Sauter mean diameter and a related average sphericity, and the main objective of the work was to determine whether these could be used to model bed combustion of a particle mixture. Measured gas concentration and temperature profiles in the burning bed are compared with a one-dimensional numerical model, which is shown to give good predictions using these mean quantity definitions. Samples of bed solids taken after the conclusion of each experiment give insight into the variation of particle mass, size and sphericity during combustion, and the averages of these also agreed with model predictions, with the caveat that the model can only calculate the average particle size, and is not able to reproduce the individual burning histories of different sizes of particles. The effects of different orientations of the wood fibres in the particles are evident from the experimental data. The results show the importance of including these effects as well as the reduction in bed specific surface area due to particle overlap in calculations. [ABSTRACT FROM AUTHOR]

A study about the temporal variation of organic emissions from a modern wood log fired masonry heater was carried out with different gas analysis techniques: single-photon ionisation time-of-flight mass spectrometry (SPI-TOFMS) for real-time analysis of volatile (VOC), intermediate-volatile (IVOC) and semi-volatile organic compounds (SVOC), and a gas analyser system for gaseous components CO 2 , CO, NO x and organic gaseous carbon (OGC, quantified by flame ionisation detector). The emissions of three in Europe common types of firewood (beech, birch and spruce) were investigated by combustion of six consecutive batches of 2.5 kg each over 4 h. Batchwise emissions and temporal variations during combustion were discussed. Emission factors over the whole combustion cycle for OGC, VOC and IVOC were right up to one order of magnitude lower than in many previous studies due to latest improvements of air staging technology in wood log fired masonry heaters, whereas CO and NO x remained comparable. Regarding each combustion experiment, more than 50% of the total intensity of the mass spectra occurred during the combustion of the first two batches. Moreover, the molecular signatures of burning phases (‘ignition’, ‘stable combustion’ and ‘ember’) were examined by using non-negative matrix factorisation (NMF) and principal component analysis (PCA) in sequence. Marker substances for wood or biomass combustion, such as phenolic species or furan derivatives, exhibited highest relative abundance during ‘stable combustion’, whereas ‘ember’ is distinctly characterised by polyunsaturated hydrocarbons, such as benzene or naphthalene, through pyrosynthesis; in ‘ignition’, secondary decomposition products dominated. Nevertheless, highest quantitative emissions always occurred during ‘ignition’ at the beginning of each batch, followed by the phases ‘ember’ and ‘stable combustion’. [ABSTRACT FROM AUTHOR]

Pinus pinaster wood was fractionated by aqueous treatments to yield a solution containing hemicellulose-derived saccharides (mainly of polymeric or oligomeric nature) and a solid phase enriched in cellulose and lignin. The solution containing polymeric or oligomeric hemicellulosic saccharides was acidified with sulfuric acid (up to 4 wt%) and heated (up to 130 °C) to assess the conversion of substrates into sugars. The interpretation of the experimental data was done on the basis of a mechanism involving 10 first-order, kinetic parameters. Almost total saccharification was achieved under a range of operational conditions, and the hydrolyzates presented compositions favorable for their further utilization as fermentation media. The solid phase coming from aqueous processing was mixed with HCl solutions and reacted under microwave irradiation to yield the target products levulinic acid (precursor of valeric biofuels) and formic acid (suitable for fuel cell devices). The effects of the most influential parameters (temperature, reaction time and acid concentration) were assessed by empirical modeling. The highest cellulose conversion into levulinic acid (61.9% of the stoichiometric value as an average) was achieved at 190 °C operating for 15 min in a medium containing 1 wt% HCl. [ABSTRACT FROM AUTHOR]

• This paper points out that the unreliable measurement of the composition and porosity of hydrate sediments is the main reason for the low prediction accuracy of Wood method, and further illustrates that Wood method is not conducive to the application of post-stack seismic data. • A Wood-Imp equation is proposed to clarify the relationship between hydrate saturation and impedance. • A wood-Imp method is proposed to reduce the prediction error of hydrate saturation by using non-hydrate layer. A large amount of suspended natural gas hydrate (NGH) has been found in Shenhu sea area of China. At present, Wood method is considered to be a suitable method for predicting the saturation of suspended NGH. However, there are two problems in the application of this method in Shenhu sea area of China. First, this method is difficult to directly predict NGH saturation based on post-stack seismic data inversion, since it does not clarify the relationship between NGH saturation and P-wave impedance. Second, the prediction results of this method are quite different from the actual values in Shenhu sea area of China, which makes it difficult to obtain reliable resource estimation in this sea area. To clarify the relationship between NGH saturation and P-wave impedance, this paper proposes an improved Wood equation called Wood-Imp equation, which lays a foundation for predicting NGH saturation by using post-stack wave impedance data. For the second problem, the main reason for the large prediction error of Wood method is that the existing measurement technology cannot avoid the measurement errors in sediment composition, pore sizes, etc. Thus, Wood-Imp method is proposed based on non-NGH layer to reduce the of NGH saturation prediction error. Three comparison experiments are used to demonstrate the effectiveness of our proposed Wood-Imp method, including simulation data, well S data in Shenhu sea area, two-dimensional forward modeling of Shenhu sea area data. (1) Wood-Imp method has much higher accuracy in predicting NGH saturation than Wood method; (2) The predicted NGH saturation in Shenhu well S by Wood-Imp method is closer to that calculated by chloride ion method than that of Wood method; (3) Wood-Imp method has obtained better NGH saturation prediction accuracy based on P-wave impedance data obtained by post-stack inversion in two-dimensional forward modeling. Therefore, the Wood-Imp method proposed in this paper is more suitable for predicting suspended NGH saturation than the existing Wood method in Shenhu sea area. [ABSTRACT FROM AUTHOR]

To understand the complex reaction mechanisms involved in biomass pyrolysis, volatile products are characterized on-line by laser-induced fluorescence (LIF), together with on-line measurements of permanent gases by GC-TCD (Gas Chromatograph-Thermal Conductivity Detector) and temperature evolutions in the bed. The focus is to determine the components that emit fluorescence and reactions involved in producing them from wood and from its two main macromolecular components, holocellulose and lignin. A technical-scale fixed-bed reactor is used to identify primary and secondary reactions involved in pyrolysis. The excitation wavelength used for the LIF measurements is 266 nm and the detected species are aromatic compounds (including one-ring phenolics and two-, three- or four-ring polycyclic aromatic hydrocarbons (PAHs)) and species containing carbonyl groups. Holocellulose volatiles show fluorescence that is attributed to the formation of carbonyl compounds and two-ring PAHs during heterogeneous secondary char-forming reactions, which also enhance the production of CO 2 . Volatiles from lignin show first fluorescence typical of one-ring phenolics and small (two–three rings) PAHs. Then, due to the enhancement of heterogeneous secondary reactions, fluorescence signal typical of bigger PAHs (three–four rings) is detected. These aromatic species are produced in parallel to gas species like CH 4 . The fluorescence that can be observed in pyrolysis of wood comes mainly from the lignin fraction, undergoing also heterogeneous secondary reactions resulting in the formation of bigger PAHs, although a contribution from cellulose is also present. [ABSTRACT FROM AUTHOR]

Pressurized, O 2 blown, entrained flow gasification of pulverized forest residues followed by methanol production is an interesting option for synthetic fuels that has been particularly investigated in the Nordic countries. In order to optimize gasification plant efficiency, it is important to understand the influence of different operating conditions. In this work, a pressurized O 2 blown and entrained flow biomass gasification pilot plant was used to study the effect of four important process variables; (i) the O 2 stoichiometric ratio ( λ ), (ii) the load of the gasifier, (iii) the gasifier pressure, and (iv) the fuel particle size. Commercially available stem wood fuels were used and the process was characterized with respect to the resulting process temperature, the syngas yield, the fuel conversion and the gasification process efficiency. It was found that CH 4 constituted a significant fraction of the syngas heating value at process temperatures below 1400 °C. If the syngas is intended for catalytic upgrading to a synthetic motor fuel where CO and H 2 are the only important syngas species, the process should be optimized aiming for a process temperature slightly above 1400 °C in order to reduce the energetic losses to CH 4 and C 6 H 6 . This resulted in a cold gas efficiency (based only on CO and H 2 ) of 70%. The H 2 /CO ratio was experimentally determined within the range 0.45–0.61. Thus, the syngas requires shifting in order to increase the syngas composition of H 2 prior to fuel synthesis. [ABSTRACT FROM AUTHOR]

In this study, the effects of particle aspect ratio (length/diameter) of a wood cylinder on pyrolysis and gasification characteristics were experimentally investigated. X-ray computed tomography was used to visualize the structure of char with different aspect ratios. Small and uniform pores were observed near the surface, whereas the size and shape of majority of the middle pores were large and random. Regardless of the aspect ratio, the pores generally aligned along the axial direction of wood cylinders. In the pyrolysis process, the total tar yield was found to decrease with an increasing aspect ratio. This was due to the tar being transported predominantly through the axial pores; therefore, wood cylinders with a high aspect ratio provided a long residence time for intraparticle tar decomposition, resulting in a lower tar yield. An Arrhenius plot of char reactivity during gasification revealed an aspect ratio effect in the internal-diffusion controlled zone (zone II), which did not appear in the kinetically controlled zone (zone I). Char reactivity increased with a decreasing aspect ratio in zone II. The gasifying agent primarily penetrated into the char through the top and bottom surface of the wood cylinder as a result of the pores aligned along the axial direction. The role of anisotropic structure of woody biomass was relevant to its aspect ratio. [ABSTRACT FROM AUTHOR]

Four different fuel blends have been fired in a 28MWel BFB. Wood pellets (test 0) were not problematic for about ten years, contrary to a mixture of demolition wood, wood cuttings, compost overflow, paper sludge and roadside grass (test 1) which caused excessive fouling at a superheater bundle after already a few weeks. Two week tests with the test 2 blend (wood chips and cuttings, compost overflow and paper sludge) and test 3 blend (wood chips, demolition wood and wood cuttings) showed that, based on air cooled probe tests, fouling was slightly higher with test 3 compared to test 2. The bulk of the deposits consisted of a mixture of CaSO4 and K2SO4 (with minor amounts of Na2SO4). The occurrence of alkali sulfates is explained by a combination of 4 different deposition mechanisms. Gaseous alkali chlorides that condense, either as chlorides or sulfates and form aerosols, that deposit, especially initially, by thermophoresis (1), and, in the more mature deposit, by eddy diffusion and Brownian diffusion (2). The gaseous alkalis can also condense directly on the tube surface or on, or in the deposit (3). Gaseous alkalis can also condense on larger particle surfaces that deposit by inertial impaction (4). Whether gaseous alkalis have sulfatized during transport or after deposition, or both, could not be determined. CaSO4 is formed by sulfation of Ca-containing particles (not being silicates or slag) that cause the deposits to be sintered modestly (tests 2 and 3) or to a large extent (test 1, matured deposit). A molten K-Na-SO4-Cl salt is thermodynamically stable at the temperature range of tube surface +40K to local flue gas temperature, and may also have contributed to sintering when reactive Ca is present locally in only low concentrations. Thermodynamic calculations predict fouling tendency as test 3>test 2>test 1>test 0. The total amount of molten salt seemed a better predictor for fouling than the amount of salt as a percentage of total ash. [ABSTRACT FROM AUTHOR]

• The total pyrolysis yields of M. gigantea ranged from 45% to 65%. • Biochar analyses show that thermal decomposition of M. gigantea occurred at >300 °C. • The E α -α relationship most closely resembled that of some non-woody species. • The average E α of M. gigantea pyrolysis were 65.5–87.7 kJ/mol. • TG-FTIR showed that CO 2 production occurred in a large number of separate stages. Fast-growing wood Macaranga gigantea has been pyrolyzed and its pyrolysis products have been characterized and their formation kinetics studied. Pyrolysis of M. gigantea wood was carried out by varying the temperature and time of pyrolysis to determine the effect of these two parameters on product yields and product characteristics. In general, an increase in pyrolysis temperature and time increased the yield of liquid and gas products, the concentration of cellulose, hemicellulose and lignin-derived compounds, but decreased the biochar yield. The organic phase liquid pyrolysis products mainly contained phenolic compounds and their derivatives, eugenols, furans, aldehydes and ketones. Fourier-transform infrared spectroscopy and pyrolysis–gas chromatography–mass spectrometry analyses of biochar showed that thermal decomposition of M. gigantea required temperatures higher than 300 °C to optimize thermal decomposition and carbonization of lignin, cellulose and hemicellulose. The concentration of phenols and benzenediols in biochar decreased with an increase in pyrolysis temperature. M. gigantea pyrolysis kinetics studies showed that wood pyrolysis occurred through four main stages with activation energy (E α) values, based on calculations by the Friedman and Kissinger-Akahira-Sunose methods, of 28.1–99.0 kJ/mol and 35.6–104.9 kJ/mol, respectively. The spectra produced by thermogravimetric analyzer coupled with a Fourier-transform infrared spectroscopy showed that H 2 O and CO 2 were produced during pyrolysis and the volatile compounds produced were predominantly phenolic compounds, in accord with characterization results of the liquid products by gas chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Macro-TGA wood pyrolysis and wood char gasification shows changes in their structure. [•] Model of thermal conversion is implemented in the ANSYS Fluent. [•] Wood pyrolysis and char gasification are simulated using the same approach. [•] Effects of cracking, shrinkage or swelling prove to be rather unimportant for simulations. [•] Wood char fragmentation is of crucial importance for gasification modelling. [Copyright &y& Elsevier]

Highlights: [•] Sunflower and jatropha seed cakes. [•] CFB gasification. [•] The fate of inorganic constituents contained in ash. [Copyright &y& Elsevier]

Highlights: [•] The method presented allows the measurement of organic sulfur compounds in biomass gasification gas. [•] Many organic sulfur species are found in biomass gasification gas, which are usually not reported. [•] Only measuring thiophene, benzo[b]thiophene and dibenzothiophene can be misleading. [•] The amount of other organic sulfur compounds can be above the limits for catalytic processes. [Copyright &y& Elsevier]

Highlights: [•] Pyrolysis of beech wood particles (0.3 and 14mm). [•] The yield of pyrolytic lignin decreased as particle size increased. [•] Two different pyrolysis regimes were confirmed between 0.3 and 14mm. [•] Secondary reactions and mass transfer limitations lead to more char. [Copyright &y& Elsevier]

Highlights: [•] Laboratory scale ex situ simulation of underground coal gasification (UCG). [•] Identification and characterization of heat-affected zone during UCG. [•] Comprehensive sampling of remnant coal surrounding cavity. [•] Establishment of depth-wise profiles of volatile matter depletion. [•] Testing with coals, lignite and wood. [ABSTRACT FROM AUTHOR]

Highlights: [•] CO2-gasification of biomass-doped metallurgical cokes was assessed by TG analysis. [•] Cokes were more reactive and gasification started at a lower temperature. [•] Different gasification patterns of cokes were identified in the early stages. [•] Effects of adding wood and charcoal were compared to those of woody constituents. [•] Contribution of chemical and physical factors on CO2-reactivity was established. [ABSTRACT FROM AUTHOR]

Highlights: [•] Used X-ray to visualize, quantify thermo-physical behaviour of wood for first time. [•] Visualization of intra-particle conversion during devolatilization for first time. [•] Visualization of propagation of char front and anisotropic effect for first time. [•] Determined “char formation time” and “shrinkage” during devolatilization. [•] 3-D model used to predict the intra-particle propagation of conversion fronts. [Copyright &y& Elsevier]

Highlights: [•] Five storage techniques were tested on SRF poplar chips stored in small (20m3) piles. [•] The storage period lasted 170days, in spring and summer. [•] Piles under plastic cover presented opposite trends compared to all other piles. [•] Dry matter losses were highest for uncovered piles, and lowest for plastic covered piles. [•] These results were closely related to the dry Southern European climate and season. [ABSTRACT FROM AUTHOR]

Many municipal waste combustors use preheated primary air in the first zone to dry the waste. In most cases the preheat temperature does not exceed 140°C. In previous experiments it is found that at temperatures around 200°C, in some circumstances, self- or spontaneous ignition can be achieved. Using preheated air can be a powerful tool to control the ignition and combustion processes in a waste combustion plant. To use this tool effectively, the influence of the preheated air on the fuel bed needs to be well understood. The present work is done to develop a model that predicts the spontaneous ignition temperature of the fuel bed and the critical temperature of the primary air at which the fuel bed ignites. The influence of primary air flow rate and addition of inert are modeled for a packed bed of wood. From the model a dimensionless parameter is derived in which all investigated parameters (fuel type, air flow rate and inert fraction) are combined. This parameter appears to be sufficient to describe both the spontaneous ignition and the critical air temperature. The results from the model are validated with experiments presented in previous work [1]. The model slightly over-predicts the temperatures by 6–7°C, and the trends are predicted well. Besides calculations for the temperatures, the ignition time and location are calculated as well. The ignition time is under-predicted due to the assumption of a uniform temperature distribution inside the particles. The location of ignition is predicted well. For char, a minimum spontaneous ignition temperature is derived from DSC measurements. The temperature at which the interaction of char and oxygen switches from endo- to exothermic seems to coincide with the spontaneous ignition temperature. [ABSTRACT FROM AUTHOR]

Abstract: In Europe biomass is a widely available resource and it would be worthwhile to develop advanced, high-efficiency integrated processes. Advanced processes involve using gasification to produce a clean syngas for fuel synthesis, powering motors, turbines and even Solid Oxide Fuel Cells (SOFCs). In comparison to H2 or natural gas feedstock, one of the challenges is that the syngas is dirty and must be cleaned to remove particles, organic and inorganic minor species, in line with different specifications depending on the various uses. Predictive calculations are valuable when designing the most suitable cleaning process. The present work outlines a dual approach developed at CEA, based on theoretical assessment and experimental validation, focusing in particular on inorganic species. The biomass is wood, which has a very low inorganic-species content. This content has been measured to serve as input data for thermodynamic equilibrium calculations performed with FactSage software. Our two main goals are to evaluate the release of inorganic species in the syngas, depending on the gasification process, and then to assess the condensation behaviour (temperature and speciation) of the condensable gases, which are responsible for corrosion of refractory lining and metallic structures of the reactors, and fouling of pipes, among others. We have investigated several reactor technologies such as fluidized bed or entrained flow reactor under allothermal or autothermal conditions. We have also calculated the total pressure effect and condensation behaviour when gas is cooled. These calculations are compared with experimental results in the literature and obtained from facilities developed at CEA. Agreements with calculations were obtained for elemental mass balance measurements of N, S, Cl classified as volatile and Al, Ca, Mg and Mn as condensed. Speciation of gas is calculated to be N2, H2S, KOH and KCl with trace of HCl in agreement with explicit measurements for H2S but not for N2 (kinetics) and no quantitative conclusions for KOH, KCl and HCl. Cooling calculations predicted K2CO3 followed by KCl as the main condensate compounds without experimental comparison available. [Copyright &y& Elsevier]

Abstract: A detailed mathematical model, comprehensive of the main chemical and physical processes, is proposed for the open-core downdraft gasification of wood pellets, which permits a dual air entry: from the top section (primary air) and at a certain height of the packed bed (secondary air). A transition is simulated from a single, top-stabilized front (zero percentage of secondary air), to a double front stabilization (percentages of secondary air up to 60–70%) and finally to a single, forced center-stabilized front at the position of secondary air injection. For sufficiently high percentages of secondary air, following the complete or partial separation between the zone of primary wood degradation and a high-temperature, oxygen-rich zone and higher temperatures along the char bed, tar and char conversion is highly enhanced. Good agreement is obtained between model predictions and measurements for a pilot-scale plant. [Copyright &y& Elsevier]