Torrefied Wood Research Articles

Characterization of the effect of pyrolysis in torrefied wood chips

The pyrolysis behavior of torrefied wood produced in Portugal was investigated. Torrefaction is the thermochemical upgrading of biomass at approximately 300ºC in an atmosphere free of oxidizing agents to increase fuel density and to improve fuel quality, decreasing moisture and increasing heating value. Torrefied woodchips were pyrolysed at pressurized conditions in an inert atmosphere at 600ºC. All the condensable liquids were sampled for analyses. All pyrolysis hydrocarbon liquids were analysed using simulated distillation (simdis) and gas chromatography mass spectrometry (GCMS). Torrefied wood hydrocarbon liquid showed higher concentrations of aliphatic aldehydes liquid. A decrease in all the other molecular components was observed for the torrefied wood hydrocarbon liquid. The main organic components in the torrefied wood pyrolysis water fractions were acids, alcohols and aliphatic oxygenates. Torrefied wood pyrolysis water exhibited a significantly lower acid concentration when compared to non torrefied wood pyrolysis water. The biomass chars (prepared at 600ºC) were analysed using proximate analyses and carbon dioxide char reactivity. Proximate analyses showed that volatile matter was still present in the torrefied wood, but was almost completely devolatilized after pyrolysis.

A Study on the Possibility of Using Torrefied Wood Flour Mixed Coagulant to Improve the Water Quality of a Muddy Water Occurrence Stream during Rainfall

A Study on the Possibility of Using Torrefied Wood Flour Mixed Coagulant to Improve the Water Quality of a Muddy Water Occurrence Stream during Rainfall

Utilization of Torrefied and Non-Torrefied Short Rotation Willow in Wood-Plastic Composites.

The torrefaction process is widely used in the energy field, but the characteristics of the torrefied wood also have positive effects on the production of wood plastic composites. In this study, short-rotation shrub willow was torrefied at 225 and 300 °C and incorporated into polypropylene composites filled with changing levels of weight percent (wt%) of non-torrefied and torrefied (5, 15, 25, and 40 wt%) wood. Nine different formulations were extruded for mechanical, thermal, and water absorption properties. The tensile properties of composites were not affected by any level of torrefaction, while higher flexure properties were in favor of lower wt% of torrefied wood. The slowest rate of thermal degradation was confirmed for the highest wt% of torrefied wood with a torrefaction temperature of 300 °C. In contrast, the presence of torrefied wood in composites did not show a difference in crystallization or melting temperatures. The most noticeable contribution of torrefaction temperature and wt% was found for water-absorbing properties, where the higher torrefaction temperature and largest wt% of torrefied wood in the composite resulted in decreased water uptake.

Ash formation and deposition during combustion of pulverized torrefied wood and coal in a 100 kW downflow combustor

Torrefied wood originating from beetle-killed trees is an abundant biomass fuel that can be co-fired with coal for power generation. In this work, pulverized torrefied wood, a bituminous coal (Sufco coal) and their blended fuel with a mixing ratio of 50/50 wt.%, are burned in a 100-kW rated laboratory combustor under similar conditions. Ash aerosols in the flue gas and ash deposits on a temperature-controlled surface are sampled during combustion of the three fuels. Results show that ash formation and deposition for wood combustion are notably different from those for coal combustion, revealing different mechanisms. Compared to the coal, the low-ash torrefied wood produces low concentrations of fly ash in the flue gas but significantly increased yields (per input ash) of ash that has been vaporized. All the mineral elements including the semi- or non-volatile metals in the wood are found to be more readily partitioned into the PM10 ash than those in the coal. The inside layer deposits sticking to the surface and the loosely bound outside deposits exposed to the gas both show a linear growth in weight during torrefied wood test. Unlike coal combustion, in which the concentration of (vaporized) ash PM1 controls the inside deposition rate, wood combustion shows that the formation of porous bulky deposits by the condensed residual ash dominates the inside deposition process. Co-firing removes these differences between the wood and coal, making the blended fuel to have more similar fly ash characteristics and ash deposition behavior to those of the bituminous coal. In addition, results also show some beneficial effects of co-firing coal with torrefied wood, including reduction of the total deposition rate and the minimization of corrosive alkali species produced by wood.

The role of torrefied wood pellets in the bio-economy: A case study from Western Canada

This work aims to provide a comprehensive in-depth analysis of the life cycle environmental and economic performance of some key global supply chains for torrefied wood pellets (TWP) used as bulk fuel, including their contribution to the bio-economy of the region where they are produced, and the effects of carbon accounting and carbon tax policies on the TWP trade. TWPs produced in British Columbia (BC), the western-most province of Canada, are taken as a specific example, with the results compared with pellets produced in other Canadian provinces, Southeast US and Vietnam. It is found that BC has comparative advantages in TWP production, benefiting from abundant biomass resources, availability of low-carbon electricity, existence of a well-developed forest product industry, and accessibility to international markets. The suitability of different domestic and overseas markets is assessed. In Canada, there is great potential demand for BC TWPs in the provinces of Alberta and Saskatchewan. In the Asia-Pacific region and Europe, BC pellets are not cost-competitive compared with pellets from Vietnam and Southeast US, due to higher production costs arising in part from BC's high carbon tax. However, BC producers have supply advantages over producers in Vietnam and the Southeast US in the province's abundant biomass and clean electricity supply. Transforming production from conventional to torrefied pellets can increase the contribution of the industry to the regional economy. The carbon accounting and carbon tax policies in different countries/regions will impact the TWP trade, and merit further study.

A Metallurgical Coke Replacement Derived from Torrefied Wood Chips Pre-Treated by Wet Oxidation

A Metallurgical Coke Replacement Derived from Torrefied Wood Chips Pre-Treated by Wet Oxidation

Influence of torrefaction on yields and characteristics of densified solid biofuel

Torrefaction is a mild thermal pretreatment for enhancing the combustion property of biomass to be properly applied to biomass or co-firing power plants. The present research investigated mass yields, fuel characteristics and hydrophobicity of rubber wood pellet torrefied at different temperatures and residence times. Proximate and ultimate analyses, the enhancement factor of higher heating value, energy yield, lignocellulosic components and Fourier transform infrared spectroscopy (FT-IR) of torrefied samples were performed to evaluate the influence of the process parameters and compared to those of the untreated ones. The non-condensable and condensable products were analyzed by GC and GC-MS. The results showed that the torrefaction severity index (TSI) correlated sufficiently with the properties of torrefied biomass and was more sensitive to torrefaction temperature than residence time. The increase in the TSI value resulted in an increase in heating value but a decrease in energy yield. The energy density increased by 14% at 260 °C and reached up to 35% at torrefaction temperature of 300 °C. FT-IR analysis revealed that the contents of hydroxyl and carbonyl groups appeared in torrefied wood pellets were decreased and increased, respectively, due to the torrefaction process. Furthermore, the hydrophobicity of torrefied pellets can be significantly improved as torrefaction temperature increases. The non-condensable gaseous products were mostly composed of CO2, CO, and traces of CH4. While the organic compounds found in condensable liquid products were acids, ketones, furans and phenols.

Milling Characteristics of Coal and Torrefied Biomass Blends in a Roller Mill.

CO2 emissions from coal power generation could be reduced by maximizing the amount of torrefied biomass that can be used in pulverized-coal-fired power plants. In this study, to evaluate the milling performance of coal and torrefied wood pellets (TPs), various blend ratios were tested using a bench-scale roller mill. Neutral sugar analysis was performed to evaluate the biomass-derived part of the milled products. Under the test conditions, mill power consumption and differential pressure increased with the TP content. As the TP content increased, the particle size of the milled products also increased. Furthermore, the biomass-derived neutral sugar content and the xylose/glucose (X/G) ratio were higher in the larger particles of the milled product and in the samples collected inside the roller mill than those in the input feedstock. The biomass-derived part with the highest X/G ratio accumulated inside the roller mill, which is probably why the mill power and differential pressure increased with the TP content. The TP, with poor grindability, was discharged from the mill with a larger particle size than that of coal. Although torrefaction treatment pyrolyzed the biomass, the degree of torrefaction can vary within the pellets depending on the torrefaction conditions. To ensure stable operation of the roller mill and an effective reduction in the size of the coal–TP blend, the selection and use of uniformly and sufficiently torrefied wood pellets are important.

Energy requirements to produce fine powders of raw and torrefied wood at pilot scale, and characterization of their flowability

This work aims at comparing different preparation chains to produce wood powders suitable for further gasification in an entrained flow reactor. Three wood powders, with particle size below 1 mm, have been produced at pilot scale from resinous wood chips: a powder of raw wood and a powder of torrefied wood both ground in a knife mill, and a powder of raw wood ground in a vibration mill. The respective requirements both in energy and in feedstock material resource have been determined for each chain of production. The production of the raw wood powder requires 0.83 MWh per ton of dry powder (tdp). The additional grinding step with the vibrating mill adds 0.63 MWhel.tdp−1. The production of the torrefied wood powder requires 3.56 MWh.tdp−1. Moreover, the wet wood chips requirements vary from 2.5 tons for the chains of production without torrefaction to 4.4 tons for the chain including a torrefaction step. In the latter, the step with the highest energy demand is the gas-cleaning step in an instrumented post-combustion reactor. Heat recovery from the combustion gases could supply energy to both the drying and torrefaction steps. It would reduce by half the total energy cost of the chain, down to 1.66 MWh.tdp−1. The resource requirements would be reduced down to 3.2 tons. The morphology and flowability of the powders have been investigated and compared. Torrefaction or vibration milling significantly improve the ability of the wood powder to flow both without any stress or when consolidated by a vertical stress.

The Evaluation of Torrefied Wood Using a Cone Calorimeter.

This study focuses on the energy potential and combustion process of torrefied wood. Samples were prepared through the torrefaction of five types of wood: Ash, beech, oak, pine and spruce. These were heated for 2 h at a temperature of 300 °C under a nitrogen atmosphere. Torrefied wood was prepared from wood samples with dimensions of 100 × 100 × 20 mm3. These dimensions have enabled investigation of torrefied wood combustion in compact form. The effect of the external heat flux on the combustion of the samples was measured using a cone calorimeter. The observed parameters, include initiation times, heat release rate and combustion efficiency. The results show that increasing the external heat flux decreases the evenness of combustion of torrefied wood. At the same time, it increases the combustion efficiency, which reached an average value of approximately 72% at 20 kW m−2, 81% at 30 kW m−2 and 90% at 40 kW m−2. The calculated values of critical heat flux of the individual samples ranged from 4.67 kW m−2 to 15.2 kW m−2, the thermal response parameter ranged from 134 kW s0.5 m−2 to 297 kW s0.5 m−2 and calculated ignition temperature ranged from 277 °C to 452 °C. Obtained results are useful both for energy production field and for fire safety risk assessment of stored torrefied wood.

Interpreting biomass gasification histories with CBK/G. Part 2. Extrapolations to entrained-flow gasification conditions

This study characterizes how biochars’ distinctive kinetics affect the predicted performance of a pilot-scale oxygen-blown, entrained-flow biomass gasifier, where temperatures and pressures are much greater than those in the laboratory database used to assign kinetic parameters in Part 1. The gasifier operates at pressures of 0.2 and 0.7 MPa, temperatures from 1050 to 1550 °C, stoichiometric ratios from 0.25 to 0.50, and firing rates from 200 to 600 kW. Predicted product gas compositions are generally accurate to within 2% for CO and 4% for H2 across the testing domain with various raw and torrefied wood products. Fifty to 70% of the CO and 65 to 90% of the H2 in the syngas form during the reforming of volatiles along with the combustion of small amounts of char and soot during the early stages while O2 is still present. Among diverse biomass forms, the crucial kinetic parameter assignment is the activation energy for oxide desorption. High energies extrapolate to nearly complete carbon conversion and nearly uniform CO levels across a broad range of SR. Low energies extrapolate to much lower carbon conversions and a corresponding fall-off in CO levels for progressively greater SR. Only biochars with the highest energies for oxide desorption have the potential to give more soot than char in their unconverted carbon emissions. This paper also presents a quantitative evaluation of extrapolated CBK/G kinetics with measured temperatures of individual particles for two gasification conditions in a lab-scale burner at 1600 °C.

Development and Assessment of Harmful Gases Reducing Molded Fuel Using Torrefied Wood

In this study, a torrefaction of Quercus serrata to manufacture a molded charcoal was performed, investigated material properties, fuel characteristics, and performed a quantitative analysis of hazardous gases which occur during a combustion process. In addition, a molded charcoal in market was selected as a control group, and a comparative analysis was performed. As a result, the higher heating value (HHV) of the torrefied specimen was about 14% higher than that of molded charcoal, and its ash content was about 51 times lower. Moreover, after performing a quantitative assessment of hazardous gases (carbon monoxide, nitrogen oxide, and sulfur dioxide) which were produced when each specimen was combusted for 900 seconds in an enclosed chamber, it was confirmed that the maximum value of generated amount of carbon monoxide on the torrefied specimen was about 50 times lower than that of the existing molded charcoal. Therefore, it was shown that the torrefied specimen produced in this study had a higher heating value than the molded charcoal in the market, and a very low amount of carbon monoxide generated during the combustion process.

Development of a torrefied wood pellet binder from the cross-linking between specified risk materials-derived peptides and epoxidized poly (vinyl alcohol)

Abstract Torrefied wood pellets are being developed as a renewable energy to handle green-house gas issues. To improve their competitiveness, binders have been studied and utilized to increase the energy density, durability, and storage life. Recent studies indicated several potential binders can be used to increase the density and strength of pellets. However, all of them required a more than 10 wt% binder level which doesn’t meet the ISO standard (

Influence of Torrefaction and Pelletizing of Sawdust on the Design Parameters of a Fixed Bed Gasifier

Gasification of biomass in fixed bed gasifiers is a well-known technology, with its origins dating back to the beginning of 20th century. It is a technology with good prospects, in terms of small scale, decentralized power co-generation. However, the understanding of the process is still not fully developed. Therefore, assessment of the changes in the design of a gasifier is typically performed with extensive prototyping stage, thus introducing significant cost. This study presents experimental results of gasification of a single pellet and bed of particles of raw and torrefied wood. The procedure can be used for obtaining design parameters of a fixed bed gasifier. Results of two suits of experiments, namely pyrolysis and CO2 gasification are presented. Moreover, results of pyrolysis of pellets are compared against a numerical model, developed for thermally thick particles. Pyrolysis time, predicted by model, was in good agreement with experimental results, despite some differences in the time when half of the initial mass was converted. Conversion times for CO2 gasification were much longer, despite higher temperature of the process, indicating importance of the reduction reactions. Overall, the obtained results could be helpful in developing a complete model of gasification of thermally thick particles in a fixed bed.

Process simulation, techno-economic evaluation and market analysis of supply chains for torrefied wood pellets from British Columbia: Impacts of plant configuration and distance to market

Improving economic competitiveness is the key for sustainable development of the wood pellet industry. To support this development, we have carried out a comprehensive techno-economic evaluation of five possible process configurations for production of conventional (CWP) and torrefied (TWP) wood pellets in the Canadian province of British Columbia (BC), based on process simulation with multi-scale models involved as illustrated in the graphical abstract. A novel heat integration strategy is proposed for the TWP production process to avoid the use of N2 and achieve auto-thermal operation. In comparison with CWPs, producing TWPs in the operating sequence drying, torrefaction, grinding, pelletization can reduce production costs by about 10% and reduce delivered costs to both domestic and overseas markets by about 20%. It is essential that the TWP plant is located in a region with abundant and low-cost feedstock, low electricity price, low labor cost, and efficient distribution logistics. Due to the low capital cost contribution (10%), torrefaction could be implemented by either building a new plant or upgrading an existing conventional pellet plant. The market analysis reveals that the future market for TWPs from BC is expected to lie outside Canada, in the Asia Pacific region, and Europe, unless significant domestic policy measures are introduced to promote Canadian use of TWPs.

A modelling based study on the integration of 10 MWth indirect torrefied biomass gasification, methanol and power production

This work is focused on the process system modelling of an indirectly heated gasifier (10 MWth) using torrefied wood as feedstock and its integration with methanol and power production using Aspen Plus®. The modelling of the gasification process along with the obtained reaction kinetics were validated with experimental data found in literature. Different processing steps such as gasification, gas cleaning and upgrading, methanol synthesis and energy conversion, were modelled and their performance was optimized through a series of sensitivity studies. The results obtained were then used to investigate the effect of different technologies and the variation of operational parameters on the overall process performance. Three cases were examined: “syngas production” (case 1), “methanol production” (case 2), and “power production” (IGCC) (case 3). Case 1 and case 2 were simulated using sand and dolomite as bed materials respectively, in order to study the incorporation of Absorption Enhanced Reforming (AER) on the syngas and methanol production efficiency. For case 3 the simulation was performed for two different configurations: a conventional Integrated Gasification Combined Cycle (IGCC) and an innovative Inverted Brayton Cycle (IBC) turbine system. Dolomite was used as the bed material for both configurations. For case 1, an increase of 5% in hydrogen yield in the product gas when AER is applied was observed. For case 2, higer values of Cold Gas Efficiency and Net Efficiency (34% and 60% instead of 33% and 55%, respectively) and a slightly lower value of Carbon Conversion (96% instead of 100%) were obtained when AER was employed. Gasification temperature was lowered by 110 °C in this scenario. For case 3, a lower value of Net Efficiency was obtained when IBC was considered (43% instead of 47%), while a value of 60% was obtained for methanol production with AE. Moreover, the results of case 3, showed that the latent heat in the hot syngas is best utilised when IBC is considered. The developed model accurately predicted the composition of the produced gas and the operational conditions of all the identified blocks within the methanol synthesis and power production processes. This way the use of this model as a generic tool to compare the utilization of different technologies on the performance of the overall process was validated.

Bio-FLASHCHAIN® theory for rapid devolatilization of biomass 2. Predicting total yields for torrefied woods

Apparently, no detailed reaction mechanisms for any torrefied biomass have yet been put forward. This study expands bio-FLASHCHAIN® to accurately predict the total volatiles yields from any torrefied wood. Whereas the original reaction mechanism and depolymerization kinetics are retained, the analysis introduces a fuel constitution submodel that uses the carbon aromaticity added during torrefaction to estimate the changes in torrefied woods that are responsible for the impacts on primary devolatilization behavior. Torrefaction replaces bridges with char links within wood macromolecules of both cellulose and lignin and these added char links are entirely responsible for the reductions in volatiles yields. The added char links are estimated without any adjustable parameters, given only an ultimate analysis for the torrefied wood. The primary devolatilization of torrefied woods abides by the same reaction kinetics as the parent raw woods, except that the energy distribution for bridge scission narrows for progressively more severe torrefaction conditions to coarsely represent the elimination of the most reactive components during torrefaction. The predictions are validated with volatiles yields from 13 woods and 22 torrefied woods for heating rates from several hundred to more than 104 °C/s to temperatures from 500 to 1000 °C with contact times from tens of milliseconds through several minutes. According to this interpretation, the most important chemistry to unravel in raw and torrefied woods is the accumulation of furans and benzenoid and condensed aromatics in cellulose throughout all stages of both torrefaction and primary devolatilization.

Modeling and prediction of devolatilization and elemental composition of wood during mild pyrolysis in a pilot-scale reactor

Mild pyrolysis, operated at 200–300 °C in an inert atmosphere, is a promising technology to produce sustainable materials (i.e., heat treated woods for construction and building) and solid fuels (i.e., torrefied woods or biochars for combustion and gasification). To aid in process and reactor design, the aim of this work is to conduct thermal degradation kinetics of wood. A two-step kinetics model is developed to predict the elemental composition (C, H, and O) and devolatilization dynamics of wood materials during heat treatment in a pilot-scale reactor by kinetic analysis. A hardwood poplar (Populus nigra) and a softwood fir (Abies pectinata) sever as feedstock, and the experiments are carried out at 200–230 °C with a heating rate of 0.2 °C min−1 in a low-pressure environment (200 hPa). The predictions in the weight losses of the woods are in a good agreement with the experimental data. The evolutions of solids, volatiles, elements (C, H, and O), and the heating values of treated woods are further analyzed. The predictions suggest that the intermediate solid is the main product, and almost all the woods are converted when the treatment temperature is as high as 230 °C. The devolatilization process, which is responsible for the mass loss of wood, can be clearly identified, and the volatile liberation amounts from poplar and fir at 230 °C are 17.05 and 12.44 wt%, respectively. The predicted HHVs of treated woods from the empirical formula are between 19.62 and 20.55 MJ kg−1, and the enhancement factors at the end of treatment are between 1.01 and 1.07 which is close to torrefied wood after light torrefaction. During the treatment, the extents of decarbonization, dehydrogenation, and deoxygenation in fir are all smaller than those in poplar, resulting from the lower intensity of devolatilization in the former.

A study of hygroscopic property of biomass pretreated by torrefaction

Abstract Torrefaction is a thermochemical conversion process, and it is adopted to improve the drawbacks of raw biomass (such as high hygroscopicity, low calorific values and energy density). During this process, biomass is thermally degraded in an inert or nitrogen environment at temperature range of 200-300 °C for several minutes to several hours. In this study, high homogeneous torrefied wood samples were produced by torrefaction at 200, 210, 220, and 230 °C. The equilibrium moisture content (EMC) of raw and torrefied wood and the contact angle of sample surface are examined to evaluate the hygroscopicity changes of torrefied wood. The results indicate that the EMC of the torrefied wood decreased by 35% or more compared to the EMC of raw material. An increasing of contact angle of torrefied wood surface is observed with increasing torrefaction temperature, and it is in the range of 103-113 ° which is correspond to hydrophobic surface (>90°). Meanwhile, the detailed mechanisms about the changes of biomass hygroscopicity after torrefacion are also illustrated in the present work.

Coagulation Treatment of Wastewater Using Torrefied Wood Powder

Coagulation Treatment of Wastewater Using Torrefied Wood Powder