Elevated Pyrolysis Temperature Research Articles

Boosting acetaminophen degradation in water by peracetic acid activation: A novel approach using chestnut shell-derived biochar at varied pyrolysis temperatures

In this study, biochar derived from chestnut shells was synthesized through pyrolysis at varying temperatures from 300 °C to 900 °C. The study unveiled that the pyrolysis temperature is pivotal in defining the physical and chemical attributes of biochar, notably its adsorption capabilities and its role in activating peracetic acid (PAA) for the efficient removal of acetaminophen (APAP) from aquatic environments. Notably, the biochar processed at 900 °C, referred to as CN900, demonstrated an exceptional adsorption efficiency of 55.8 mg g−1, significantly outperforming its counterparts produced at lower temperatures (CN300, CN500, and CN700). This enhanced performance of CN900 is attributed to its increased surface area, improved micro-porosity, and a greater abundance of oxygen-containing functional groups, which are a consequence of the elevated pyrolysis temperature. These oxygen-rich functional groups, such as carbonyls, play a crucial role in facilitating the decomposition of the O–O bond in PAA, leading to the generation of reactive oxygen species (ROS) through electron transfer mechanisms. This investigation contributes to the development of sustainable and cost-effective materials for water purification, underscoring the potential of chestnut shell-derived biochar as an efficient adsorbent and catalyst for PAA activation, thereby offering a viable solution for environmental cleanup efforts.

Effects of various pyrolysis temperatures on the physicochemical characteristics of crop straw-derived biochars and their application in tar reforming

As a by-product of the rapid pyrolysis of biomass, biochar not only plays an important role in the biomass conversion process but also holds significant potential value in the catalytic conversion field. This study aimed to evaluate the physicochemical properties changes of biochars at different pyrolysis temperatures and their potential application in tar reforming. Biochars derived from three feedstocks of maize straw (MS), rice husk (RH), and cotton straw (CS) were achieved by fast pyrolysis within a broad temperature range of 300–900 °C, respectively. The results showed that the pyrolysis temperature exerted a pronounced influence on the structural characteristics of biochar. With increasing temperature, the H/C and O/C ratios progressively decreased, accompanied by a significant reduction in oxygen-containing structures. In addition, elevated pyrolysis temperatures contributed favorably to the formation of the crystalline structure of biochar. Raman analysis unveiled a correlation between the fused aromatic ring system and H/C ratios, validating the aromatization progress of biochar. In the tar catalytic reforming process, the three representative biochars, under the effect of MS-600 (standing for MS biochar derived at 600 °C), RH-600, and CS-600 catalysts, exhibited outstanding catalytic performance with tar conversion efficiencies of 73.26%, 68.51%, and 71.43%, respectively. This study provided systematic support for the high-value use of biochar from crop straw.

Comparison of PAHs behaviors in the pyrolysis products of oily sludge with different ash contents

Due to the presence of petroleum hydrocarbons, the production of polycyclic aromatic hydrocarbons (PAHs) is inevitable after oily sludge pyrolysis. The dispensation of PAHs in pyrolysis products was studied. The results indicated that PAHs were mainly enriched in liquid products, accounting for 97.97–99.88 %. Besides, the percentage of low-ring PAHs in products was the largest, subsequent to middle-ring PAHs. In the pyrolysis products of oily sludge with distinguishing ash contents, the impressions of pyrolysis temperature and residence time on the behaviors of PAHs were also compared. When pyrolysis temperature or residence time were variables, there were some similar characteristics in PAHs behaviors of oily sludge with different ash contents. The total concentration of PAHs in liquid products was positively correlated with pyrolysis temperature and residence time. The equal alteration was also exhibited in the concentration of high-ring PAHs in gas products with an increase in pyrolysis temperature. The formation of low-ring PAHs in liquid and gas products was improved by extended residence time. However, there were also differences in the evolution of PAHs in products of low-ash oily sludge (LOS) and high-ash oily sludge (HOS). The concentrations of low-ring and middle-ring PAHs in LOS gas products were positively correlated with pyrolysis temperature. Antithetically, the formation of low-ring and middle-ring PAHs in HOS gas products was inhibited by elevated pyrolysis temperature. Interestingly, the low-ring PAHs were converted into high-ring PAHs in HOS gas products with increasing pyrolysis temperature. As the residence time prolonged, the total concentrations of PAHs in LOS solid and gas products enlarged first and then reduced. Nevertheless, those of HOS were improved by continued residence time.

Revisiting the reaction scheme of slow pyrolysis of woody biomass

Existing lumped kinetic models have limited accuracy in predicting the pyrolysis behavior of different materials. There is currently no universally accepted model capable of accurately predicting pyrolysis rates and final product yields for various materials under different experimental conditions. This study aims to address this limitation by assessing the sensitivity of a widely used wood pyrolysis kinetic model across multiple sets of experimental data. The analysis reveals that the existing model falls short in accurately predicting the yields of woody biomass at higher temperatures. To overcome this, two new kinetic models were proposed that incorporate additional reactions not accounted for in conventional models. These additional reactions have impact on the formation of secondary pyrolysis phases. The first proposed model introduces a term for secondary tar formation, which takes into account the production of more stable cracked, dehydrogenated, and deoxygenated tars that typically occur at elevated pyrolysis temperatures, possibly influenced by catalysts. The second proposed model expands on this concept by incorporating terms that represent the formation of secondary gases and chars arising from the primary chars. By including these additional reactions, the model enhances its accuracy and predictive capacity for determining the pyrolytic products of various types of woody biomass.

Preparation and Characterization of Porous Materials from Pineapple Peel at Elevated Pyrolysis Temperatures.

In this work, pineapple peel (PP) was reused as a precursor in biochar (BC) production at elevated temperatures (i.e., 500–900 °C) for residence times of 0–60 min. The findings showed that pyrolysis temperature and residence time played a vital role in pore development. As pyrolysis temperature increased from 800 to 900 °C for residence times of 20 and 60 min, the data on the Brunauer–Emmett–Teller (BET) surface area of the resulting biochar products significantly jumped from 11.98–32.34 to 119.43–133.40 m2/g. In addition, there was a significant increase in the BET surface area from 1.02 to 133.40 m2/g with the residence time of 0 to 20 min at 900 °C. From the data of the nitrogen adsorption–desorption isotherms and the pore size distribution, both micropores (pore diameters of <2.0 nm) and mesopores (pore diameters of 2.0–50.0 nm) are present in the PP-based biochar products. Due to its good fittings in the pseudo-second-order model and its hydrophilic nature, as seen in the Fourier transform infrared spectroscopy (FTIR), the resulting biochar could be a porous material to be used for the effective removal of cationic compounds (i.e., methylene blue (MB)) from liquid phases.

Optimized production conditions and activation of biochar for effective promotion of long-chain fatty acid degradation in anaerobic digestion

Engineered biochar production and utilization in anaerobic digestion (AD) potentially overcome its limited application to the treatment of slowly degradable or inhibitory substrates. Here an attempt was made to develop an optimized biochar production procedure for use in AD to stimulate palmitic acid biodegradation via direct interspecies electron transfer (DIET). The electrical conductivity of biochar was greatly increased with an elevated pyrolysis temperature and K2CO3 activation, and the conductivity reached a comparable level (0.6–1.4 S/cm) to that of carbon black at 800 °C. In addition, the K2CO3 activation greatly improved biochar wettability. When using K2CO3-activated biochar produced at 800 °C, the maximum methane production rate from palmitic acid was 1.3 times that of a control without biochar addition.

Permeability variations of lignite and bituminous coals under elevated pyrolysis temperatures (35–600 °C): An experimental study

Studies on permeability under pyrolysis temperatures (PTs) can provide instructions for syngas production of underground coal gasification (UCG). Permeability variations of lignite, high volatile bituminous coal (HVBC) and medium volatile bituminous coal (MVBC) under elevated PTs (35°C–600 °C) were studied. Structure and weightlessness as well as maturity of coal detected by methods of micro structure observation, nuclear magnetic resonance, thermogravimetric analysis, and liquid yield measurement, were investigated and clarified to probe the factors influencing permeability variation. The results showed: (1) permeability of lignite and HVBC as well as MVBC increased during 35–200 °C. Lignite permeability decreased during 200–600 °C while HVBC and MVBC permeability decreased during 200–400 °C and then increased during 400–600 °C; (2) for coals with different maturities, pyrolysis reactive strength controlled the permeability. Lignite permeability were always the greatest followed by HVBC, and MVBC permeability were always the lowest, at PTs of 125–500 °C; (3) for an individual coal, permeability variation was controlled by the relative strength between positive factors (water and volatiles’ discharge, stable char framework, increased inertoid content, and high porosity of char) and negative factors (blocking of penetration channels by tars or char fines or a mix of these two, closure of macro-pores and fractures, and unstable char framework).

The rapid pyrolysis feature and evolution of heteroatoms of Indonesian oil sand

The rapid pyrolysis behavior of a kind of Indonesian oil sand was studied by a fixed-bed reactor. According to X-ray photoelectron spectroscopy (XPS), 1H nuclear magnetic resonance spectra (1H NMR) analysis, the organic structure model of oil sand and the occurrence of heteroatoms were proposed. Liquid products were characterized by gas chromatograph with mass spectrometer (GC-MS) and atomic emission detector for gas chromatography (GC-AED). In addition, the distribution of the gaseous product was analyzed using gas chromatograph (GC). During the rapid pyrolysis process, the tar yield reached its maximum at 450 °C, and the gas yield increased rapidly with the increasing temperature, while the residual sand yield displayed the opposite trend. Aromatic esters and aliphatic hydrocarbons were the predominant components of liquid products after rapid pyrolysis treatment. More stable heteroatom compounds, such as thiophene and furan, would be released into liquid product with an elevated pyrolysis temperature. Atoms like sulphur and oxygen on the aliphatic side chain were easily transformed into gaseous products such as H2S, CO2 and CO. Sulfur-containing compounds in oil sand minerals converted from sulfate to metal sulfide during the pyrolysis process. After thermal decomposition, heteroatoms compounds in organic matter transferred to gaseous product or liquid product along with the volatiles. However, heteroatom compounds in inorganic substances presented in residual sand in a more stable form.

B(N) redor and B spin echo studies for structural charactreization of Si-B-N precursor ceramics

A Solid-state NMR spectroscopy is employed for the structural characterization oj precursorderived Si-B-C-N ceramics. Particular emphasis is given to the structural composition of the BNCx phase which plays a key role for the unusual high temperature stability of these materials. In the present work nB('5N) REDOR and B spin echo experiments are presented for two /SN enriched precursor systems, made from substituted polysilazanes and polvsilvlcarbodiimides. which provide interatomic boron-boron and boron-nitrogen distances. The obtained results are compatible with the presence of layered structures as reported for hexagonal boron nitride [h-BJ. The derived boron-nitrogen and boron-boron distances, however, are larger than in h-BN, reflecting some layer distortions. The boron-boron distances are found to decrease with increasing pyrolysis temperature, whereas the boron-nitrogen distances remain practically unaltered at elevated pyrolysis temperatures. On the basis of the present results it is concluded that intercalated BN.and sp2-carbon layers most likely constitute the BNCX. phase. The graphite-like carbon layers are assumed to create some internal pressure, which in turn is responsible for the observed interatomic distance increase in the BN layers. However, other scenarios, like the direct incorporation of small sp1-carbon domains into the BN-sheets, cannot be ruled out completely. Further work along this line appears to be necessary to develop a comprehensive structural model for the BNCxphase in such quarternarv ceramic systems.&#x0D;

Characterization of nitrogen and sulfur migration during pressurized coal pyrolysis and oxy-fuel combustion

In the present work, pressurized coal pyrolysis and oxy-fuel combustion experiments were carried out in a pressurized drop tube furnace to investigate the migration and transformation characteristics of nitrogen and sulfur. The pyrolysis experiments showed that high pyrolysis pressure inhibited the release of nitrogen and sulfur. The content of oxidized nitrogen (N-X), pyrite, sulfide, sulfoxide and sulfate in char decreased, while the content of pyridine nitrogen (N-6), pyrrole nitrogen (N-5), quaternary nitrogen (N-Q), thiophene and sulfone in char increased with the increase of pyrolysis pressure. The elevated pyrolysis temperature was conducive to the decomposition of nitrogen and sulfur-containing functional groups, and it also promoted the conversion of nitrogen and sulfur to functional groups with high stability such as N-Q and thiophene. The release of volatiles and the decomposition of nitrogen and sulfur-containing functional groups in coal were promoted by CO2 gasification. The increase of the total CO2 gasification pressure led to more nitrogen and sulfur remaining in char. During pressurized oxy-fuel combustion in O2/CO2 atmosphere, the emissions of NO, NO2 and SO2 were lower than those in air combustion. The emissions of NO, NO2 and SO2 gradually decreased with the increase of pressure at air and oxy-fuel atmospheres. The increase of temperature increased the emissions of NO and SO2 at different pressures, but the NO2 emission decreased at elevated temperature. In addition, the emissions of NO and NO2 increased, but the emission of SO2 decreased with the increase of oxygen concentration.

Aging features of metal(loid)s in biochar-amended soil: Effects of biochar type and aging method

Soil contamination with toxic metals and metalloids has become a major threat to global food security. Among various immobilization agents that can stabilize toxic metal(loid)s effectively, biochar is promising due to its ability to restore soil health. Yet the aging characteristics of biochar following its amendment in soil remain poorly explored. Therefore, this study used standard biochars to depict their aging effects on remediation of metal(loid)-contaminated soil. A total of 2304 observations were made, including 6 biochar feedstocks (rice husk, soft wood, oilseed rape straw, miscanthus straw, sewage sludge and wheat straw), 2 pyrolysis temperatures (550 °C, 700 °C), 8 metal(loid)s (Mn, Ni, Cu, Zn, As, Cd, Sb, Pb), 4 aging methods (natural aging, freeze-thaw cycling, wet-dry cycling, chemical oxidation with H2O2), and 6 sampling intervals. Sewage sludge biochars exhibited the highest resistance to both artificial and natural aging, which may be related to the abundant oxygen-containing functional groups that favor metal complexation, and poorly-developed pore structures that limit the access of natural aging forces. A distinct relationship between ash and temperature was observed, where for high-ash biochars, an increase in pyrolysis temperature indicated lower resistance to aging, while for low-ash biochars, elevated pyrolysis temperature led to higher resistance. The aging behaviors of Cu and Sb were quite similar, which were both highly susceptible to chemical oxidation-induced dissolved organic carbon (DOC) release. Wet-dry cycling and freeze-thaw cycling revealed aging patterns that were similar to those of naturally aged soils as confirmed by cluster analysis. Lab aging data were then compared with existing biochar field aging results. Contrasting long-term immobilization performances were found in different studies, which were attributed to various causes associated with both biochar property and climate. The results of this study provide fresh insights into the long-term risks in the management of metal(loid)-contaminated agricultural soils.

Iron-crosslinked alginate derived Fe/C composites for atrazine removal from water

Fe/C composite is emerging as a promising nanoscale zero-valent iron (nZVI) based material for wastewater treatment to counteract the limitations of nZVI, while its preparation method, structure-activity relationship, and working mechanisms and conditions still need to be studied. In this study, Fe/C composites derived from iron-crosslinked alginate was successfully achieved via high temperature pyrolysis. Ferric ions were only transformed into Fe3O4/γ-Fe2O3 at low pyrolysis temperature (≤500 °C), whereas Fe0/Fe3C became the primary Fe species with the formation of graphitic carbon at elevated pyrolysis temperature (≥700 °C). Fe/C composites from higher pyrolysis temperature presented better performance in atrazine (ATZ) removal, and the optimal pyrolysis temperature was 800 °C (Fe/C-800). Batch experiments showed that the removal kinetics of ATZ (10 mg L−1) by Fe/C-800 (0.2 g L−1) followed pseudo-second-order model, and 24-h ATZ removal efficiency maintained at 93.5 ± 1.0% within pH 3–9. The adsorption by the graphitic carbon phase of Fe/C-800 was the principal contributor to the pH-independent superior performance in ATZ removal, and the Langmuir model fitted adsorption capacity was 64.8 mg g−1 at pH 6. Although the carbon-phase adsorbed ATZ was basically unavailable for degradation, Fe0/Fe3C-mediated ATZ degradation contributed to the great reactivity of Fe/C-800 at pH 3. Fe0/Fe3C in Fe/C-800 was more efficient for ATZ degradation than commercial nZVI, and oxidative dealkylation by Fe0/Fe3C mediated Fenton reaction was the predominant ATZ degradation pathway rather than reductive dechlorination. Moreover, the produced ATZ degradation intermediates could be further adsorbed by Fe/C-800, mitigating potential secondary pollution. Thus, iron-crosslinked alginate derived Fe/C composites can be an excellent alternative for nZVI in organics-polluted water treatment with great reactivity and wide pH applicability.

Effect of Pyrolysis Temperature on PhysicoChemical Properties and Acoustic-Based Amination of Biochar for Efficient CO2 Adsorption

The present study examined the effect of pyrolysis temperature on the physicochemical properties of biochar, activation process and carbon capture. Two different categories of biochars were synthesized from herbaceous (miscanthus and switchgrass) or agro-industrial (corn stover and sugarcane bagasse) feedstock under four different pyrolysis temperatures- 500, 600, 700 and 800 oC. The synthesized biochars underwent sono-amination activation comprising low-frequency acoustic treatment followed by amine functionalization to prepare adsorbents for CO2 capture. As per the elemental analysis, the elevated pyrolysis temperature resulted in increased %C and %ash contents and reduced %N contents of biochar. The textural analysis exhibited almost 3-times enhancement of micro surface area and pore volume upon increasing the pyrolysis temperature from 500 to 700 oC, though further increase to 800 oC reduced the micro-porosity and the surface area. The intermediate temperatures of 600 and 700 oC revealed the highest interactions with ultrasound-amination, which significantly intensified CO2 adsorption. Accordingly, the CO2 capture capacity of sono-aminated biochars synthesized at 600 and 700 oC were almost 200% greater than that of raw biochars. There were 127-159% and 115-151% increases in adsorption capacity of biochars synthesized at 800 and 500 oC upon ultrasono-amine functionalization. Miscanthus biochar synthesized at 700 oC and treated sono-chemically demonstrated the highest adsorption ability of 2.89 mmol/g at 70 oC and 0.10 atm partial pressure, which is 211% higher than its pristine condition. The superior adsorption capacity of miscanthus (at 700 oC) can be attributed to its large surface area (324.35 m2/g), high carbon content (84%), and low ash content (4.9%), as well as its %N content after sono-amination that was twice that of raw char.

Pressurized entrained-flow pyrolysis of lignite for enhanced production of hydrogen-rich gas and chemical raw materials

This paper reports the enhanced production of H2 and polyaromatics during lignite pyrolysis under pressurized entrained-flow conditions. The pyrolysis temperature and pressure ranged between 600−900 °C and 0.1–4.0 MPa, respectively, and were found to greatly influence the yield and composition of pyrolysis products. The results showed that the concentration of H2 in the light gas fraction increased drastically with pyrolysis temperature and pressure, reaching 91.69 vol% at 900 °C and 4.0 MPa, which corresponded to H2 generation of 0.27 m3/kg coal. The yield of polycyclic aromatic hydrocarbons (PAHs) such as naphthalene, biphenylene, fluorene, phenanthrene, pyrene, and fluoranthene was also promoted at elevated pyrolysis temperatures and pressures. The highest PAHs concentration of 90.4 area% in the pyrolysis oil was obtained at 900 °C and 4.0 MPa. It was also found that the changes in the hydrogen distribution under pressurized entrained-flow conditions mainly took place during the secondary pyrolysis reactions. It was postulated that hydrogen was formed via aromatization, condensation, aromatic ring growth mechanism, and direct cleavage reactions. The findings of this study showed that lignite could be efficiently converted to H2-rich gas, PAHs as chemical raw materials, and energy-dense lignite char via a novel poly-generation system based on pressurized entrained-flow pyrolysis.

Influence of the Addition of Cotton Stalk during Co-pyrolysis with Sewage Sludge on the Properties, Surface Characteristics, and Ecological Risks of Biochars

Sewage sludge produced by municipal sewage treatment plants can potentially be used as a biomass energy source because of its high organic content. Presently, the conversion and utilization of rapidly growing amounts of sewage sludge represent an urgent challenge in China. Thermal conversion of sewage sludge to biochar through pyrolysis is a promising solution to this problem. However, biochar produced by pyrolysis of sewage sludge alone has a poor pore structure as a result of its low C content and high ash content. Furthermore, it is enriched in heavy metals that may pose high ecological risks. In this study, we addressed these issues through co-pyrolysis of sewage sludge and cotton stalks (1:1, wt./wt.) at different pyrolysis temperatures ranging from 350°C to 750°C. The properties and surface characteristics of the biochars were investigated. Meanwhile, the transformation behavior of heavy metals during the co-pyrolysis process was studied, and the potential ecological risks of heavy metals in biochars were assessed. The results showed that elevated pyrolysis temperatures reduced the biochar yield and C content of the biochars, whereas such temperatures increased the pH value and ash content of the biochars. The biochars prepared at different pyrolysis temperatures were all mesoporous materials. The elevated temperatures promoted the transformation of heavy metals from mobile fractions to stable ones, thus resulting in a significant decrease in the ecological risks. In summary, co-pyrolysis of sewage sludge with cotton stalks proved to be a feasible method for the conversion and utilization of sewage sludge.

Research on thermal disposal of phytoremediation plant waste: Stability of potentially toxic metals (PTMs) and oxidation resistance of biochars

Thermal conversion of phytoremediation plant waste into biochar was performed as a safe approach for organic waste management. In this work, a promising phytoremediation plant―Silphium perfoliatum L. was pyrolyzed for biochar production at 350, 550 and 750 °C. The long-term leaching risk of potentially toxic metals (PTMs) in the derived biochars and the oxidation resistance of the biochars were investigated. The results showed that PTMs in the biochar could transform into more stable and less toxic forms with the elevated pyrolysis temperature. PTMs leaching behavior in the 350 °C biochar was considerably sensitive to the leaching while that in the 750 °C biochar was not affected. The biochar produced at a higher temperature possessed a greater oxidation resistance with little amount of C loss, and the stronger oxidation resistance would prevent the release of metals bound to the organic matter. The findings of this study demonstrated that high-temperature pyrolysis was able to reduce the potential risk of PTMs and ensure carbon stability.

Effects of thermal conditions on char yield and char reactivity of woody biomass in stepwise pyrolysis

Stepwise pyrolysis with one low-temperature thermal pretreatment (torrefaction or carbonization) and one high-temperature pyrolysis is an important utilization of biomass. This study aims to investigate the effects of thermal conditions on char yield and char reactivity in the stepwise pyrolysis with woody biomass used as feedstock. The accumulated char yield (on original mass basis) and char reactivity were determined. Pyrolysis products were analyzed by Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectrum. The results show that thermal pretreatment increases the aromaticity of feedstock as well as char yield, and reduces the char reactivity and degree of order, which indicate probable intrinsic correlation among them. The effect of thermal pretreatment on char yield is more pronounced at elevated pyrolysis temperature, but indiscernible at low heating rate. The influences of particle size and residence time of thermal pretreatment are relatively small.

Factors affecting the sorption of halogenated phenols onto polymer/biomass-derived biochar: Effects of pH, hydrophobicity, and deprotonation

High-performance biochar synthesized via co-pyrolysis of a polymer and rice straw (RS) was evaluated as a sorbent for ionizable halogenated phenols. Compared with RS-derived biochar, the sorption of 2,4-dichlorophenol (DCP), 2,4-dibromophenol (DBP), and 2,4-difluorophenol (DFP) onto polymer/RS-derived biochar was significantly enhanced by the properties of biochar changing due to polymer residues. According to Langmuir sorption isotherm model maximum sorption capacities for DCP, DBP, and DFP were 25.5–27.8, 22.1–26.5, and 11.5–13.3 mg/g, respectively, 3–5 times higher than those of RS-derived biochar. The removal of the polymer residues and increasing aromaticity of polymer/RS-derived biochar at elevated pyrolysis temperatures affected the sorption capacity of halogenated phenols. The surface charge of biochar and deprotonation of the halogenated phenols according to the solution pH were other factors responsible for sorption onto polymer/RS-derived biochar. Competition with other halogenated phenols, Zn2+, and Cu2+ implied that similar sorption mechanisms existed and that surface complexation and electron donor-acceptor interactions were involved in sorption onto polymer/RS-derived biochar. Our results suggest that co-disposal of thermoplastic and biomass wastes through pyrolysis may be an effective option to produce high-performance upgraded biochar as a sorbent for various types of contaminants.

Effect of Char Structure Evolution During Pyrolysis on Combustion Characteristics and Kinetics of Waste Biomass

Two waste biomass materials, pine needle (PN) and corn stalk (CS), were pyrolyzed at different temperatures (200–900 °C). The organic functional groups and carbonaceous structure of the biomass chars were characterized by Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, respectively. The combustion characteristics and kinetics of biomass chars were investigated by thermogravimetric analysis (TGA). The content of carbon-, hydrogen-, and oxygen-containing functional groups in the biomass samples decreases with an increase in preparation temperature, leading to more aromatic macromolecular structure at elevated pyrolysis temperatures. With increasing pyrolysis temperature, the comprehensive combustibility index (S) of both chars related to combustion reactivity generally decreases especially for CS char because of the loss of active groups. However, the Raman spectra show that the degree of order decreases with increasing pyrolysis temperature from 400 to 700 °C because of the generation of isolated sp2 carbon.

Polycyclic aromatic hydrocarbons on particulate matter emitted during the co-generation of bioenergy and biochar from rice husk

The aim of this study was to evaluate the emissions of polycyclic aromatic hydrocarbons (PAHs) bound to the particulate matter (PM) during the combustion of raw pyrolysis volatiles (bio-oil and pyrogas mixture) generated from the pyrolysis of rice husk. Five different raw pyrolysis volatiles were produced at varying pyrolysis temperatures (400–800°C) and subsequently combusted in a laboratory-scale, continuous pyrolysis-combustion facility at 850°C. 15 priority pollutant PAH levels in the resulting biochar, bio-oil, and PM were evaluated. Results showed that combustion of the raw pyrolysis volatiles produced at elevated pyrolysis temperatures resulted in greater concentrations of PM-bound PAHs (119% increase between 400 and 800°C) due to the increased PAH and oxy-aromatic content of the bio-oil fraction. Significantly increased benzo(a)pyrene (BaP) – equivalent toxicity of the biochar and PM was observed at elevated pyrolysis temperatures.