Wood Char Research Articles

An Intensification of Biomass and Waste Char Gasification in a Gasifier

Gasification is considered a clean and effective way to convert low quality biomass to higher value gas and solve various waste utilization problems as well. However, only 80% of biomass is converted through thermal processes. The remaining part is char, which requires more time for conversion and in that case reduces the efficiency of gasifier. Seeking to optimize the process of gasification, this work focuses on the intensification of residual char gasification in a gasifier. For this purpose, three different types of char prepared from wood, sewage sludge and tire were examined under different conditions in a lab-scale gasification setup. Results showed that the air flux increase from 0.11 kg/(m2s) to 0.32 kg/(m2s) intensified the gasification process and the gasification rate increased from 0.8 to 2.61 g/min with the decrease of duration of wood char gasification by 72%. An additional introduction of pyrolysis gas into the char gasifier led to decreased bed temperatures, but the gasification rate increased from 0.8 to 1.25 g/min and from 2.61 g/min to 2.83 g/min, respectively, for the wood char and the sewage sludge char. Moreover, the use of pyrolysis gas coupled with air as the gasifying agent enhanced the composition of produced gas from char, and the CO2 concentration decreased by 1.68 vol% while the H2 concentration increased by 2.8 vol%.

Improvements in Fire Resistance, Decay Resistance, Anti-Mold Property and Bonding Performance in Plywood Treated with Manganese Chloride, Phosphoric Acid, Boric Acid and Ammonium Chloride

(1) A compound protectant was prepared using manganese chloride, phosphoric acid, boric acid and ammonium chloride, and then a veneer was immersed in the prepared protectant to prepare plywood in this paper. Great attention was paid to discussing influences of such protectant on fire resistance, decay resistance, anti-mold property and bonding performance of plywood. Results demonstrated that after protectant treatment, the plywood showed not only good fire resistance and smoke inhibition, but also strong char-formation ability, slow flame spreading, long time to ignition, small fire risk and high safety level. (2) The mass loss rates of plywood with protectant treatment after infection and erosion in wood-destroying Coriolus versicolor and Gloeophyllum trabeum were 19.73% and 17.27%, reaching the II-level corrosion grade. (3) There is not a significant difference with Aspergillus niger V.; however, it was possible to observe a strong difference with Trichoderma viride Pers. ex Fr., indicating that the protectant acted as a good anti-mold product for plywood. (4) The protectant influenced the bonding interface of wood and bonding conditions of the adhesive. The bonding strength of plywood was weakened, but it still met the requirements on bonding strength of GB/T 9846-2015. (5) The protectant changed the thermal decomposition and thermal degradation of plywood, inhibiting the generation of inflammable goods, blocking transmission of heats and lowering the thermal decomposition temperature of plywood. These promoted dehydrations and charring of wood and the generated carbon had a high thermal stability. (6) Compared with untreated plywood, the prepared protectant treatment significantly enhanced the fire resistance of plywood, reduced its biodegradability by wood-decaying fungi and showed good mold resistance.

Development of a small-scale reactor for upgraded biofuel pellets

The comprehensive investigation of a pyrolysis reactor has been conducted on the basis of thermal engineering design. The gas dynamics, thermodynamic, and psychrometric behaviour of the producer gas have been thoroughly assessed. The pilot-scale reactor has been programmed to operate at the temperature 973 K in the absence of an inert medium. The concentric casing of the heating filament has been used as an external source of energy. The experimental task is divided into two parts: upgradation of biomass and the decomposition of pellets in a developed small-scale pyrolysis unit for the possible gas, char, and pyrolysis oil generation. The fuel upgradation is performed via quasi-static torrefaction of pine pellets using Joule heating in the presence of nitrogen gas. The volumetric gas of nitrogen flowing across the improvised furnace is 0.70 L·min−1. The obtained results are compared with the wood pellets. The unsaturated producer gas has been found to vary accordingly to the following gas equation pv0.25=C and pv−0.69=C for the processed pine pellets and wood pellets, respectively. A relative increase of 21.00% has been seen while running the reactor with the processed pine pellets. The percentage yield of the pyrolytic oil for the processed pine and wood pellets is 10.48% and 30.00% respectively. The flame temperature and adiabatic flame temperature of the producer gas (processed pine) is lowered by 8.10% and 17.00% respectively. The energy yield of processed pinechar is found to be 122.58% higher than that of wood char.

Biomass‐derived Graphene‐like Catalyst Material for Oxygen Reduction Reaction

AbstractA novel and sustainable method was established to prepare a nitrogen doped graphene‐like material from a renewable, secondary raw material with potential application in the catalysis of oxygen reduction reaction (ORR). Alder wood char was used as a precursor material for producing a sustainable graphene‐like carbon catalyst for the ORR. Alder wood char was first activated (AWC) and then doped with nitrogen (N−AWC). The graphene‐like structure was confirmed using transmission electron microscopy (TEM) and Raman spectroscopy. Electrochemical characterization was carried out in 0.1 M KOH, showing that in alkaline media the ORR activity of the N‐doped wood char‐based graphene‐like material is superior compared to non‐sustainable commercial N‐doped graphene. The onset potential of the ORR on N‐AWC was shifted to positive direction by 75 mV in comparison to the commercially available nitrogen‐doped graphene and the half‐wave potential was shifted even by 239 mV. This renewable biomass‐derived graphene‐like carbon catalyst shows a great potential alternative to current synthetic graphite, graphene nanoplatelets and graphene materials in areas such as fuel cells and batteries.

Athmospheric Hydrocracking of Jatropha Oil Using Woodchar Catalyst

Jatropha oil which is non-edible oil were hydro-crack at atmospheric pressure using an activated wood char catalyst in a fixed bed reactor. The hydro-cracking process was carried out at three temperature variations of 400, 450 and 500oC, and three variations of the oil feed injection rate of 2/2, 2/5 and 2 mL/10 minutes. The catalysts were characterized using SEM and BET. The composition of the liquid product obtained from the hydro-cracking process was analyzed using GC-MS. The effects of operating temperature and oil feed injection rate on oil recovery and conversion have been discussed. The results showed that the feed injection temperature and rate had an effect on the yield and conversion. The highest yield of 59.8% oil liquid products was achieved at a temperature of 450oC with injection rate of 2 mL/10 min. The composition of the oil-liquid product was dominated by heptanal at 32.9% -mass. Alkanes group contain C5 to C20 and alkene compounds consist of C8 until C18.

Biomass-Derived Graphene-like Catalyst Material for Oxygen Reduction Reaction

Fuel cell (FC) is considered to be one of the most promising energy conversion devices that could possibly be a good alternative replacing the fossil-fuel based technologies in the future. One of the greatest shortcomings of the low-temperature FCs is the poor kinetics of the oxygen reduction reaction (ORR) happening at the cathode side. As it is widely known, the most extensively used cathode catalyst for FCs is Pt or its alloys. But many research groups all over the world study nitrogen-doped metal-free catalyst materials that could possibly be used in FCs as well [1].In recent years, the conversion of biomass into more valuable carbon nanomaterials has been a topic of great interest [2]. The conversion of biomass to carbon nanostructures paves the way for a new avenue of nanomaterial synthesis and could potentially solve scale-up issues with traditional methods of graphene production. Biomass is abundant, the global production of agricultural lignocellulosic wastes is around ~200 billion per year [3].In this research we demonstrate a two-step synthesis method of producing nitrogen-doped graphene-like material from biomass that shows better electrochemical activity towards the ORR than commercially produced nitrogen-doped graphene oxide. A novel and sustainable method was established to prepare nitrogen doped graphene from the renewable, secondary raw material with potential application in the catalysis of ORR. Current research is also proposing a good alternative solution to the increasing need of synthetic graphite, graphene nanoplatelets and graphene by the various industries, including fuel cells and batteries.In this work, alder wood char was used as a precursor material for producing a graphene-like carbon catalyst for the ORR. In the first step, activated carbon (AC) was prepared using chemical activation with NaOH, the ratio of activator vs wood char was 3:1 and the process was carried out in the flowing argon atmosphere. The activation process is important to achieve higher specific surface area. The second step was the doping of AC with nitrogen using dicyandiamide (DCDA) as a nitrogen source, the mass ratio of carbon material/DCDA was 1:20. The graphene-like structure was determined using transmission electron microscopy and Raman spectroscopy. The successful doping of nitrogen was confirmed with using X-ray photoelectron spectroscopy. The most abundant nitrogen component was pyridinic-N (42%), followed by amine (37%) and pyrrolic-N (21%). Electrochemical characterisation was carried out in 0.1 M KOH using rotating disc electrode (RDE) method. Glassy carbon (GC) electrodes were modified with the catalyst ink (4 mg ml−1). The initial loading of the catalyst material on the GC electrode was 400 μg cm−2. Electrochemical measurements showed that the ORR activity of the N-doped wood-based graphene-like catalyst (N-AWC) is superior compared to commercial N-doped graphene (N-GO) in the alkaline media (Figure 1a). Onset potential of the ORR was shifted to positive direction by 75 mV in comparison to the commercially available nitrogen-doped graphene and half-wave potential was shifted even by the magnitude of 1.5. For comparison the graphene oxide (GO) polarisation curve can also be seen (Figure 1). In the studied range, the number of electrons transferred per O2 molecule was 4, indicating that the process proceeds via 4-electron pathway.Usually the conversion of biomass may include many steps, including an additional pre-treatment step, but our two-step approach has a potential to also be integrated in the larger scale synthesis processes.[1] Q. Wei, X. Tong, G. Zhang, J. Qiao, Q. Gong, S. Sun, Catalysts 2015, 5, 1574.[2] M. Borghei, J. Lehtonen, L. Liu, O. J. Rojas, Adv. Mater. 2017, 1703691.[3] J. K. Saini, R. Saini, L. Tewari, 3 Biotech 2015, 5, 337. Figure 1

Reforming of tar model compounds over sustainable and low-cost biochar: Special focus on spontaneous gasification reactivity and tar reforming kinetics for reformer design

In this study, the spontaneous gasification and catalytic activity of wood char were experimentally evaluated in simulated sorption enhanced gasification (SEG) environments with toluene and naphthalene as tar model compounds. Besides, CaO was used as a reference catalyst for the comparison purpose since CaO is a commonly used sorbent in the SEG process. A model of gasification reactivity during reforming of tar model compounds over wood char was developed in this work based on the reactivity at 20% carbon conversion adopting the Extended Random Pore Model, where the pre-exponential factor, activation energy, and structural parameter were calculated to be 1.65·1010 min−1, 265.8 kJ mol−1, and 127, respectively. During the catalytic activity investigation, hydrogen was found to inhibit tar-reforming performance over CaO while the impact of hydrogen was insignificant over wood char. The results showed that spontaneous gasification during tar surrogates reforming led to mass loss, pore collapse, and inorganics agglomeration, which contributed to the catalytic deactivation of wood char. By considering gasification-caused deactivation, the carbon conversion was then used as a variable to modify the kinetic equations of the tar surrogates reforming. The activation energy and pre-exponential factor of naphthalene reforming (and toluene reforming) over wood char were calculated with the values of 422.5 kJ mol−1 and 2.92·1022 m3 kg−1 h−1 (284.8 kJ mol−1 and 1.90·1015 m3 kg−1 h−1), respectively, whereas the values for CaO were 126.9 kJ mol−1 and 6.79·104 m3 kg−1 h−1 (254.5 kJ mol−1 and 6.73·1011 m3 kg−1 h−1), respectively. The kinetic models developed in this study were later used for designing a tar reformer integrated with the SEG process.

Effect of calcium ferrites on carbon dioxide gasification reactivity and kinetics of pine wood derived char

Biochar gasification is an essential stage of chemical looping biomass gasification, a promising sustainable source of energy that may limit anthropogenic carbon dioxide emissions. Here, the performance of calcium ferrite oxygen carriers (CaFe2O4, and Ca2Fe2O5) on the CO2 gasification reactivity and kinetics of pine wood char is investigated by a thermogravimetric analyzer. The morphology and graphitization degree of the pine wood derived biochar were characterized by using high-resolution transmission electron microscope (HRTEM) and Raman spectroscopy. A random pore model is established and the best matching structural parameter, Ψ, is used to indicate the pore structure of the initial char samples. Results indicate that the activation energy under biochar with no oxygen carrier, biochar loaded with 10 wt% Fe2O3, 10 wt% Ca2Fe2O5, and 10 wt% CaFe2O4 are 169.76 kJ/mol, 176.03 kJ/mol, 173.81 kJ/mol, and 178.83 kJ/mol, respectively. The introduction of oxygen carriers increases the activation energy for CO2 gasification, potentially due to competition with calcium ferrite reduction, resulting in decreased CO2 partial pressure.

De-dusting in biomass gasification process using a coated bag filter

The gasification process of solid refuse fuel (SRF) releases tar and particulate pollutants in addition to many gaseous pollutants. This study investigated the effectiveness of pre-coating on a fabric filter for dust collection instead of a combined control process involving a wet scrubber and a bag filter. The powder layer composed of hydrated lime, wood char, or activated carbon contributed to reduce the blocking of the open pores of the fabric filter by tar and particulate matter. Among the three materials, hydrated lime was accumulated the most, resulting in a 0.7-mm coating thickness. The filter made of polyphenylene sulfide was the most effective in collection efficiency (86%) for the allowable pressure drop (60 mmH2O). Since a single filter with pre-coating is highly efficient, an oil scrubber with a removal efficiency of 2% to 3% is not essential.

A novel approach to determine charring of wood in natural fire implemented in a coupled heat-mass-pyrolysis model

Abstract The paper presents a novel approach to determine charring of wood exposed to standard and natural fire that is based on a new numerical model named PyCiF. The new model couples an advanced 2D heat-mass model with a pyrolysis model. A new charring criterion based on a physical phenomenon is implemented in the PyCiF model to determine charring of wood. This presents the main advantage of the new PyCiF model in comparison to common modelling approaches, which require an empirical value of the charring temperature that is often called the char front temperature. The fact that the char front temperature is not an explicit value as assumed by the isotherm 300 °C is advantageously considered in the presented approach where an assumed empirical value of the char front temperature is not directly required to determine the thickness of char layer. The validation of the PyCiF model against experimental results showed great model accuracy, meaning that the model is appropriate for the evaluation of charring depths of timber elements exposed to the standard fire as well as the natural fires. Additionally, as shown in the case study, the presented approach also enables to determine the char front temperature for various natural fire exposures. This will be especially important for the upgrade of the new design methods for fire safety of timber elements exposed to natural fire given in the various design codes such as Eurocode 5.

Optimized production of single-use plastic-Eucalyptus wood char composite for application in soil

Co-pyrolysis of Eucalyptus wood (EW) and Single-use plastic (SUP) can be a sustainable and green technological option ensuring optimum resource recovery and plastic waste management in a circular economy. This study aims to optimize the variables of pyrolysis [temperature (300, 400, 500, 600 °C), residence time (90, 120, 150 min), and proportion of plastic (w/w - 0.25, 0.33)] for application of SUP - EW char composite in soil. Statistical analysis showed that all three process variables had significant influence on properties of the char. With temperature and residence time, the char became dense, carbonaceous, ash-rich, aromatic, and alkaline for both the proportions of SUP in the feed. Further characterization also revealed that the highest plant extractable concentrations of major nutrients, cation exchange capacity, and electrical conductivity of char composite were recorded with temperatures of 400–500 °C, residence time of 120 min, and 33% (w/w) of SUP. The surface morphology analysis revealed the char to have a porous structure with a coating of plastic at lower temperatures of 300 °C and an increase in microporosity at higher temperatures of 500, 600 °C. Significant positive correlations between radicle root growth and prominent plant growth parameters observed through seed germination test indicate the char’s potential applicability in soil. The optimized process parameters of char obtained through regression modeling for application in soil were 415.2 °C, 125.2 min, and 0.325 (w/w) proportion of SUP. The highest mean seed length of ≈17.5 cm observed at 400 °C, 120 min, and 0.33 (w/w) proportion of SUP was consistent with these optimized parameters. Soil incubation test further showed that amendment with optimized char composite significantly improved its properties with a 3.7-fold increase in soil fertility index at 5% rate of application. So, the application of optimized SUP - EW char composite could significantly improve the properties of soil while promoting greener sustainable development through ideal utilization of the so far mismanaged waste resources.

The effects of activation conditions on physical properties of activated carbon

Porous carbons with a high porosity were successfully produced from fast pyrolysis pine wood char via a thermochemical method in which KOH was used as chemical activator. The effects of various weight ratios of KOH to pyrolysis char (0.65:1, 0.7:1, 1.0:1, 1.35:1, and 1.7:1) on the physical properties of activated carbons were investigated. When the weight ratio of KOH to pyrolysis char was 1.35:1, the prepared activated carbon had the highest surface area of 1140 m2/g with a total pore volume of 0.71 cm3/g, a microporous surface area of 957 m2/g, and a microporous specific volume of 0.51 cm3/g. As the weight ratio of KOH to pyrolysis char increased from 0.65 to 1.35, the prepared activated carbon had increases in total surface area, total pore volume, microporous surface area, and specific volume of micropores. However, there was a reverse trend when the weight ratio of KOH to pyrolysis char was higher than 1.35. The use of nitrogen as a flow gas resulted in much more developed activated carbon than without nitrogen. The experiment results suggested that activated carbon with high surface area could be prepared from pyrolysis char by adjusting the activation conditions.

Effect of calcium dispersion and graphitization during high-temperature pyrolysis of beech wood char on the gasification rate with CO2

This paper presents thermal deactivation of beech wood chars during secondary pyrolysis in a drop-tube reactor. Pyrolysis temperature was varied between 1000 °C and 1600 °C at a constant residence time of 200 ms. The effect of pyrolysis conditions on initial conversion rate R0 during gasification, graphitization of the carbon matrix and ash morphology was investigated. Gasification experiments for the determination of R0 were conducted in a thermogravimetric analyzer using pure CO2 at 750 °C and isothermal conditions. A linear decrease in initial conversion rate R0 was observed between 1000 °C and 1400 °C. However, a strong increase of R0 at 1600 °C was encountered. Micropore surface area of the secondary chars showed no correlation with the initial conversion rate R0 during gasification with CO2. Graphitization of the carbon matrix was determined using X-ray diffraction and Raman spectroscopy suggesting the growth of aromatic clusters and graphite-like structures for increasing pyrolysis temperatures up to 1600 °C. Furthermore, CaO dispersion was analyzed quantitatively and qualitatively using temperature-programmed reaction at 300 °C as well as SEM/TEM. CaO dispersion DCaO decreases steadily between 1000 °C and 1400 °C whereas a strong increase can be observed at 1600 °C, which is in good accordance with the development of the initial conversion rate R0 as a function of pyrolysis temperature. SEM/TEM images indicate the formation of a thin CaO layer at 1600 °C that is presumably responsible for the strong increase in initial conversion rate R0 at this temperature. When excluding the catalytic activity of CaO via formation of the ratio R0DCaO−1, increasing graphitization degree has a linear negative influence on char reactivity at pyrolysis temperatures between 1000 °C and 1400 °C.

Effect of gasification reactions on biomass char conversion under pulverized fuel combustion conditions

The effect of gasification reactions on biomass char conversion under pulverized fuel combustion conditions was studied by single particle experiments and modelling. Experiments of pine and beech wood char conversion were carried out in a single particle combustor under conditions of 1473-1723 K, 0.0-10.5% O2, and 25-42% H2O. A comprehensive progressive char conversion model, including heterogeneous reactions (char oxidation and char gasification with CO2 and H2O), homogeneous reactions (CO oxidation, water-gas shift reaction, and H2 oxidation) in the particle boundary layer, particle shrinkage, and external and internal heat and mass transfer, was developed. The modelling results are in good agreement with both experimental char conversion time and particle size evolution in the presence of oxygen, while larger deviations are found for the gasification experiments. The modelling results show that the char oxidation is limited by mass transfer, while the char gasification is controlled by both mass transfer and gasification kinetics at the investigated conditions. A sensitivity analysis shows that the CO oxidation in the boundary layer and the gasification kinetics influence significantly the char conversion time, while the water-gas shift reaction and H2 oxidation have only a small effect. Analysis of the sensitive parameters on the char conversion process under a typical pulverized biomass combustion condition (4% O2, 13% CO2, 13% H2O), shows that the char gasification reactions contribute significantly to char conversion, especially for millimeter-sized biomass char particles at high temperatures.

Degradation Behavior of Polypropylene during Reprocessing and Its Biocomposites: Thermal and Oxidative Degradation Kinetics.

Non-isothermal thermogravimetric analysis (TGA) was employed to investigate the degradation of polypropylene (PP) during simulated product manufacturing in a secondary process and wood–plastic composites. Multiple batch mixing cycles were carried out to mimic the actual recycling. Kissinger–Akahira–Sunose (KAS), Ozawa–Flynn–Wall (OFW), Friedman, Kissinger and Augis models were employed to calculate the apparent activation energy (Ea). Experimental investigation using TGA indicated that the thermograms of PP recyclates shifted to lower temperatures, revealing the presence of an accelerated degradation process induced by the formation of radicals during chain scission. Reprocessing for five cycles led to roughly a 35% reduction in ultimate mixing torque, and a more than 400% increase in the melt flow rate of PP. Ea increased with the extent of degradation (α), and the dependency intensified with the reprocessing cycles. In biocomposites, despite the detectable degradation steps of wood and PP in thermal degradation, a partial coincidence of degradation was observed under air. Deconvolution was employed to separate the overlapped cellulose and PP peaks. Under nitrogen, OFW estimations for the deconvoluted PP exposed an upward shift of Ea at the whole range of α due to the high thermal absorbance of the wood chars. Under air, the Ea of deconvoluted PP showed an irregular rise in the initial steps, which could be related to the high volume of evolved volatiles from the wood reducing the oxygen diffusion.

Self-heating effects in the thermogravimetric analysis of wood char oxidation

Thermogravimetric curves are measured, by means of a flexible home-made (HM) system, of the oxidation of wood chars generated from packed-bed pyrolysis at 800 K. A careful control of the sample temperature and a small mass/size (4 mg mass corresponding to 140micron thick particle layer) allow a kinetic regime to be established for heating rates between 5 and 10 K/min. Good quantitative predictions are obtained based on a two-step mechanism, with activation energies affected by the hardwood or softwood origin of chars (125–143 kJ/mol and 186–207 kJ/mol for the devolatilization and oxidation reaction, respectively). The same conditions applied for a standard commercial (SC) thermogravimetric system result into remarkable self-heating leading to uncontrolled ignition and too slow oxygen diffusion rates. Only extremely small sample masses (≤1mg) and slow heating rates (≤5K/min) permit to completely eliminate heat and mass transfer intrusions but the actual limits are strictly related to the specific char reactivity.

Lab-Scale Investigation of Palm Shell Char as Tar Reforming Catalyst

This research investigated the application of palm shell char as a catalyst for the catalytic steam reforming of tar after the sorption enhanced gasification (SEG) process. The catalytic activities of palm shell char and metal-supported palm shell char were tested in a simulated SEG derived syngas with tar model compounds (i.e., toluene and naphthalene) at a concentration of 10 g m−3 NTP. The results indicated that palm shell char had an experimentally excellent catalytic activity for tar reforming with toluene and naphthalene conversions of 0.8 in a short residence time of 0.17 s at 900 °C. A theoretical residence time to reach the complete naphthalene conversion was 1.2 s at 900 °C for palm shell char, demonstrating a promising activity similar to wood char and straw char, but better than CaO. It was also found that potassium and iron-loaded palm shell chars exhibited much better catalytic activity than palm shell char, while the parallel reaction of gasification of K-loaded palm shell char influenced the conversion with its drastic mass loss. Moreover, contrary to CaO, palm shell char presented relatively low selectivity to benzene, and its spontaneous gasification generated extra syngas. In summary, the present study demonstrated that the low-cost material, palm shell char, can successfully be used as the tar-reforming catalyst after SEG process.

Waste chars from wood gasification and wastewater sludge pyrolysis compared to commercial activated carbon for the removal of cationic and anionic dyes from aqueous solution

This study compared the properties of waste chars from gasification of wood chips and pyrolysis of wastewater sludge with a commercial activated carbon for the adsorption of dyes. Before the adsorption tests, sludge char was steam-activated at various temperatures between 650 and 900 °C. The activated sample with the largest porosity was chosen for further testing alongside the original sludge char. Results from adsorption tests with methylene blue (cationic dye) and amaranth (anionic dye) were analysed with equilibrium and kinetic models. Wood char showed the highest dye removal efficiency, followed by commercial activated carbon. Monolayer completion was not achieved for these materials in the tested conditions. Sludge char showed maximum adsorption capacities of 13.4 and 8.4 mg/g for the anionic and cationic dye, respectively. Steam activation improved these values to 19.6 and 12.3 mg/g. The cationic dye uptake was in all cases higher compared with the anionic dye.

Effects of pyrolysis temperature and feedstock type on particulate matter emission characteristics during biochar combustion

Aiming to reduce the emission of particulate matter (PM) during biomass combustion, we investigated the effects of pyrolysis temperature and feedstock type on the chemical properties of biochar and PM emission characteristics during subsequent combustion. Wood- and manure-based char samples were prepared at pyrolysis temperatures ranging from 200 to 500 °C and combusted in a laboratory-scale tube furnace at 850 °C. Due to the removal of volatile matter (VM), the total PM emission factor (EF) of the wood char decreased with increasing pyrolysis temperature, becoming negligible with pyrolysis at temperatures over 400 °C. For manure char, although pyrolysis removed VM and reduced the total PM EF from 12.5 ± 2.7 to 5.8 ± 2.9 mg/g-fuel, the high ash content precluded any effect on the emission of ash-derived PM. The occurrence of ash-derived PM resulted from release of Na, Mg, K, and Ca and was enhanced at higher combustion temperatures. We demonstrated that the pyrolysis of low-ash biomass effectively reduces the risk of PM emission. However, the efficacy of thermal treatment of high-ash biomass is limited but might be improved with further treatment, such as ash removal.

Gasification performance of torrefied Timothy hay and spruce wood chars in a CO2 environment

AbstractTimothy hay abundantly available in New Brunswick, Canada, is mostly used for animal feed and bedding. Upgrading biomass using Torrefaction method can offer benefits in its waste management, energy density and energy conversion efficiency. Temperature and residence time play an important role in the torrefaction process. Meanwhile, CO2 gasification is also a promising thermochemical conversion process due to its potential to reduce net GHG emissions and tune syngas composition. This study investigates the impact of torrefaction parameters on isothermal and non‐isothermal CO2 gasification of Timothy hay and spruce chars. Timothy hay chars exhibited higher CO2 gasification reactivity than chars from spruce. The physicochemical properties analysis indicated that higher reactivity of Timothy hay char was mainly attributed to the high amount of alkali and alkaline earth metal (AAEM) content, relatively large BET surface area, a high number ofactive sites, and a low crystalline index. Moreover, in both experimental cases, char derived through a high heating rate and high residence time conditions exhibited improved gasification performance, which was attributed to the generation of large amounts of AAEM (Ca and K) and high specific surface area. Co‐gasification results during non‐isothermal processes under CO2 showed the presence of larger interactions in coal char/Timothy hay char blends than that of coal char/spruce char blends. For both experimental conditions, interactions were enhanced once the char prepared from high heating rate and high residence time was gasified with coal char. Thus, the proposed approach is a sustainable way of conversion of Timothy hay under CO2 environment.