Pyrolysis Stage Research Articles

An experimental study on monitoring and early warning of spontaneous coal combustion fires using CPM

At present, the conventional indicator gas has a blank temperature interval in the monitoring of coal spontaneous combustion fire area, and the monitoring accuracy is easy to be interfered by wind flow, which leads to the inaccurate grasp of the situation of the fire area. To solve this problem, the characteristics of condensable particulate matter (CPM) released into the air during spontaneous combustion and heating are analyzed in this paper through a particle collection system. The results showed that the CPM captured by the system gradually increased when the coal temperature rose above 250℃, and the diameter was above 1um. After 300℃, the release of CPM increased significantly, which was more than 10 times that below 300℃. Test analysis showed that these CPMs were mainly phenols and polycyclic aromatic hydrocarbons, which accounted for 22 % and 37 % respectively after 300℃. CPM mainly comes from the pyrolysis stage and the early stage of combustion of coal. Aliphatic macromolecules and polycyclic aromatic compounds generated by pyrolysis are the precursors of CPM. Due to the limitation of oxygen diffusion, these compounds are released into the air due to insufficient oxidation and eventually form CPM. It is worth noting that the release amount and composition of CPM have a good correspondence with coal temperature. The research results can fill the temperature gap of monitoring fire situation by conventional gas, and help to improve the accuracy of monitoring, which is of great significance for the protection of coal resources and safe production.

Increase of bridge length by ingenious grafting of ester chains, imparting epoxy resins superb thermal, smoke suppression, gas-phase flame retardancy, and mechanical properties

While bifunctional synergistic flame retardants have demonstrated efficacy in enhancing the fire safety of epoxy resins (EPs), the grafting of specific functional monomers into flame retardant molecules, elucidating their mechanisms of action through comparative analysis, and concurrently achieving a delicate balance among flame retardancy, heat resistance, and mechanical toughness remains a significant challenge. Herein, this research present an innovative strategy to derive a novel sulfur-based bifunctional flame retardant, DSTA, based on the structure of the original flame retardant, DST, by grafting the ester chains to increase the bridge length of the molecular structure. As expected, the addition of flexible ester chains enabled DSTA to have a very high initial decomposition temperature and the heat-resistance index. DSTA can be used in low dosage compared to DST, enabling EP to achieve UL-94 V-0 rating. Combustion behavior showed that DSTA had the best ability to heat and smoke suppression for EP, and had faster response speed and higher fire growth index. Notably, pyrolysis volatiles tested on DSTA revealed that the ester chains can pyrolysis to release large amounts of CO2, which occurs in the early stages of pyrolysis and works together with other N-containing inert gases and P-containing radicals in the gas-phase to efficiently extinguish flames. Meanwhile, DSTA improves all mechanical properties of EP, which was attributed to the presence of ester chains. In summary, this work presents a new strategy for examining the impact of specific functional groups on the flame retardant mechanisms of EP.

Molecular dynamics study of waste tire pyrolysis: Focus on intermediate product evolution and sulfur migration law

With the rapid development of the automotive industry, the large number of waste tires poses significant environmental and health pressures. Pyrolysis technology offers a way to resourcefully utilize waste tires by converting them into pyrolysis oil, pyrolysis gas, and pyrolysis char, which has promising application prospects. However, there are still considerable challenges in the application of this technology, such as unclear reaction mechanisms and the high sulfur content of the products, which limit its practical implementation. Although some research has elucidated the pyrolysis mechanisms, there remain significant gaps in understanding the evolution paths of key intermediate and final products, as well as the detailed migration and transformation patterns of sulfur. This study uses reactive molecular dynamics simulation to investigate the pyrolysis process of tires. A three-dimensional polymer molecular model was constructed to study the pyrolysis process of waste tires at different temperatures, focusing on the evolution of key products, intermediate products, and sulfur-containing components. The results indicate that CH4 and ·CH3 radicals collide with unsaturated hydrocarbons through carbon-hydrogen transfer reactions and radical chain reactions, leading to polymerization. During the initial stage of pyrolysis, sulfur primarily exists in the form of sulfur-containing hydrocarbons (CHS). As pyrolysis progresses, the quantity of CHS decreases. With increasing pyrolysis temperature, the proportion of sulfur in the S form far exceeds that of CHS. At a pyrolysis temperature of 3000 K, the proportion of S is 64 %, while the proportion of CHS is 23 %.

Kinetic research of red mud waste oxidative pyrolysis and comparison under different atmospheres

Red mud, as a solid waste with high alkalinity, had a detrimental impact on the environment and required urgent attention. Currently, the mass processing and consumption of red mud were typically conducted under thermal conditions, so it was essential to gain a comprehensive understanding of the oxidative pyrolysis process. The thermogravimetric experiments were conducted at multiple heating rates in air and exhibited three obvious stages. The activation energy and reaction mechanism of three oxidative pyrolysis stages were explored using model-free and model-fitting methods, revealing the activation energies of 162.2, 265.8, 214.1 kJ/mol and the most suitable reaction mechanisms of g(α)=[-ln(1-α)]³, g(α)=1-(1-α)1/⁴, g(α)=[-ln(1-α)]1/2 for each stage, respectively. Furthermore, the estimated kinetic parameters and reaction mechanisms were applied to extra heating rate to verify the accuracy. More important, the effect of air on the pyrolysis process of red mud was examined by comparing the results with those obtained from pure nitrogen pyrolysis. The obtained oxidative pyrolysis characteristics of red mud could provide valuable insights of its co-pyrolysis or combustion for resources recycling.

Pyrolysis characteristics and kinetic analysis of coating pitch derived from ethylene tar using model-free and model-fitting methods

This work conducted the pyrolysis of coating pitch derived from the ethylene tar through thermogravimetry analysis. The thermogravimetry-mass spectrometry and solid-state 13C nuclear magnetic resonance spectroscopy were performed to correlate the structural characteristics with the pyrolysis behavior. Meanwhile, the pyrolysis kinetics were estimated with model-free and model-fitting methods. The TG-DTG results showed that the pyrolysis process was generally divided into drying, fast pyrolysis, and polycondensation stages, accompanied by the decomposition of active functional groups like the aliphatic carbons bonded to oxygen (falO), the pyrolysis of relatively stable groups like the non-protonated aromatic carbon (faH), and the condensation of high bonding-energy aromatic structure like aromatic bridgehead carbon (faB). The activation energy obtained from model-free analysis ranged from 78.12 to 150.92kJ/mol with the increasing conversion, indicating the pyrolysis process as a multi-step reaction mechanism. Furthermore, the reaction model A1/3 (gα=[−ln(1−α)]3) was identified as the most suitable model for the pyrolysis of coating pitch in the conversion range of 0.25-0.8. The modeling values matched well with the experimental data, indicating the accuracy and feasibility of the results.

Characteristic and mechanistic study of enhanced carbon-based synfuel from biomass and coal by magnetite additive for synergistic co-carbonization technology.

Biomass is a renewable and potentially carbon-neutral energy source and can be a promising alternative to fossil fuels in the ironmaking industry. The co-carbonization technology of biomass and coal for high-quality biofuel production has great potential. This study investigated the effects of the addition of magnetite (Fe3O4) on the physicochemical properties and combustion performance of wood shavings (WS) and bituminous coal (BC) (WS/BC = 4/6) sintered with a carbon-based synfuel. The results indicate that increasing the proportion of 2 wt.% Fe3O4 can increase the high calorific value to 34.60 MJ·kg-1 and the maximum combustion rate temperature reaches 469 °C, however, increasing the proportion decreases the burnout temperature to 575 °C, and the activation energy of the rapid pyrolysis stage decreases to 43.54 kJ·mol-1. In addition, the activation energies of WS/BC char in the fast co-pyrolysis stage and the combustion reaction decrease significantly to 43.54 kJ·mol-1 and 92.96 kJ·mol-1, respectively, with the addition of 2 wt.% Fe3O4. The area ratio of the fitted aromatic C−O reaches 79.91%. Fe3O4 can form active centers on the surface of a carbon-based synfuel, improving the stability and orderliness of the fuel. The catalysis of the Fe3O4 additive with macromolecular organic compounds involves mainly oxygen-containing functional groups, promoting the cleavage of C−C bonds connected to oxygen-containing functional groups. In general, these results provide certain theoretical guidance for the preparation and application of sintered carbon-based synfuels.

Comprehensive thermal properties, kinetic, and thermodynamic analyses of biomass wastes pyrolysis via TGA and Coats-Redfern methodologies

This study comprehensively analyzes the thermal decomposition characteristics as well as the kinetic and thermodynamic parameters of five biomass wastes, including coffee husk, groundnut shell, macadamia nutshell, rice husk, and tea waste, using Thermogravimetric Analysis (TGA) and the Coats-Redfern method. The TGA experiments were conducted on a PerkinElmer STA 6000 instrument under an inert N2 atmosphere with a heating rate of 20 °C/min, spanning a temperature range from 25 °C to 950 °C. The results identified three distinct pyrolysis stages: drying, devolatilization, and char formation, with macadamia nutshell demonstrating the highest thermal reactivity and efficient devolatilization characteristics, reflected by its lowest initial devolatilization temperature (175 °C) and highest peak temperature (380 °C). Kinetic analysis revealed that coffee husk had the highest overall activation energy (Ea) of 60.59 kJ/mol, indicating complex thermal degradation behavior. The thermodynamic evaluation showed that coffee husk also exhibited the highest enthalpy change (ΔH=55.46 kJ/mol) but the lowest Gibbs free energy change (ΔG=148.34 kJ/mol), suggesting high energy requirements for decomposition but relatively more spontaneous reactions compared to other biomass types. Macadamia nutshell demonstrated high ΔG (163.24 kJ/mol) and moderate ΔH (32.44 kJ/mol), reflecting greater resistance to spontaneous decomposition. The comprehensive pyrolysis index (CPI) and devolatilization index (Ddev) confirmed macadamia nutshell as the most reactive biomass, while rice husk exhibited the lowest reactivity. The findings highlight the importance of multi-step kinetic analysis for accurately understanding pyrolysis processes, providing critical insights for optimizing biomass conversion for energy production. Future research should explore co-pyrolysis with varied biomass mixtures and advanced kinetic modeling to enhance energy yields.

Stepwise dechlorination and co-pyrolysis of poplar wood with dechlorinated polyvinyl chloride: Synergistic effect and products distribution

With the combination of stepwise dechlorination and co-pyrolysis techniques, this study conducted polyvinyl chloride (PVC) dechlorination experiments and co-pyrolysis experiments of poplar wood (PW) with dechlorinated polyvinyl chloride (DPVC) by thermogravimetric analysis and a fixed bed reactor. Stepwise pyrolysis effectively removed Cl from PVC with a dechlorination efficiency of 99.84 % at 360 °C for 30 min. Thermogravimetric tests and thermokinetic variables were employed to describe the co-pyrolysis process's thermodynamic behavior, where co-pyrolysis significantly diminished the activation energy of the initial pyrolysis stage (9.65–21.62 kJ/mol) and increased the reaction rate (0.02–0.09 %/°C). The synergistic effect of co-pyrolysis enhanced the yield and quality of liquid oil and reduced the solid residue rate, with the maximum change in solid residue rate (−2.36 wt%) occurring at PW:DPVC = 3:7. The optimal conditions for the synergistic effect are a raw material ratio of 3:7 at 500 °C. Co-pyrolysis efficiently reduced the content of oxygen-containing compounds of phenols, ketones, and acids in oil, and elevated the selectivity of aromatics. The research methods avoid the drawbacks of bio-oil and plastic oil and improve the quality of pyrolysis oil in a concise and efficient manner, which provides some new ideas for the resource and clean utilization of municipal waste.

Recovery and restoration of glass fibers from end‐of‐life composite waste through pyrolysis and partial oxidation processes combined with hot alkaline surface treatments

AbstractEnvironmental hazards caused by the ever‐increasing end‐of‐life (EoL) glass fiber reinforced polymer (GFRPs) composite waste is of major concern for the sustainable development of the industry. Compared to land filling or incineration, pyrolysis is one of the most promising environmentally friendly methods of disposal of EoL GFRPs. Pyrolysis not only results in recovery of clean glass fibers but other valuable products, such as oils. However, long processing time at elevated temperature leads to aggravation of already existed surface flaws along with the structural changes. Therefore, thermal conditioning of glass fibers results in severe deterioration of the strength in recovered fibers and hence limiting the use of recovered fibers to low end‐products. In this study, a new strategy was adopted where instead of complete cleaning of the fibers at pyrolysis stage, the fibers were partially oxidized and the complete removal of char from the surface of glass was done during hot alkaline etching. This strategy was opted to enhance the quality of the required fibers while reducing the processing time. The results showed ~200% increase in strength of fibers after the combined treatment of pyrolysis and post etching compared to the just pyrolyzed samples with etching time of just 1 min.Highlights End‐of‐life panels of GFRPs were pyrolyzed under inert environment of Argon. Residual char was partially removed through post oxidation under flowing air. Hot alkaline etching resulted in complete removal of char and surface defects. Partial oxidation and short etching cycles resulted in improved strength of recovered glass fibers.

One-Stage Synthesis of Microporous Carbon Adsorbents from Walnut Shells—Evolution of Porosity and Structure

One-stage synthesis technology for preparing carbon adsorbents with tailored porosity from agricultural waste is worthwhile due to their extensive application value. Thermal gravimetric analysis, low-temperature N2 adsorption, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and Raman spectroscopy were used to record the structure transformations of carbon materials, namely pore development, proceeding in the course of the step-wise pyrolysis of renewable and low-cost raw materials such as walnut shells (WNSs), which was carried out within a temperature range of 240–950 °C in a CO2 flow. The minimum threshold carbonization temperature for preparing nanoporous carbon materials from WNSs, determined by the examination of the N2 adsorption data, was 500 °C. The maximum specific micropore volume and BET surface achieved in the process without holding a material at a specified temperature were only 0.19 cm3/g and 440 m2/g, respectively. The pyrolysis at 400–600 °C produced amorphous sp2 carbon. At a temperature as high as 750 °C, an increase in the X-ray reflection intensity indicated the ordering of graphite-like crystallites. At high burn-off degrees, the size of coherently scattering domains becomes smaller, and an increased background in X-ray patterns indicates the destruction of cellulose nanofibrils, the disordering of graphene stacks, and an increase in the amount of disordered carbon. At this stage, pores develop in the crystallites. They are tentatively assigned to crystallites with sizes of 15–20 nm and to micropores. According to the Raman spectra combined with the XRD and SAXS data, the structure of all the pyrolysis products is influenced by the complex structure of the walnut shell precursor, which comprises cellulose nanofibrils embedded in lignin. This structure was preserved in the initial stage of pyrolysis, and the graphitization of cellulose fibrils and lignin proceeds at different rates. Most of the pores accessible for gas molecules in the resulting carbon materials are associated with former cellulose fibrils.

Dynamic evolution of particulate and gaseous emissions for typical residential coal combustion

Residential coal combustion still accounts for half of the heating energy consumption in many developing countries. The dynamic variation during the combustion process importantly determines the combustion facility design and appropriate air quality assessment, which was omitted in conventional studies. This study investigated the emissions of particulate and gaseous pollutants during the combustion process for typical coal types using online monitoring. During the first pyrolysis stage with temperature climbing, the organic aerosols (OA) and gases reached peak concentration. The second fierce combustion stage had the highest temperature and produced the highest cumulative emissions, particularly a substantial amount of black carbon for coals with higher volatile content. Using higher-quality coals will undoubtedly reduce PM emissions, by a factor of 10 from bituminous to anthracite coal. However, more ultrafine particles (d < 0.1 μm) from cleaner coal may pose additional health risks. Anthracite and honeycomb coal had approximately twice the energy content and emitted more CO2 per unit mass of fuel and had more persistent SO2 emissions throughout the burnout stage. The oxygenation of OA and organic gases remained increased during combustion, suggesting the pyrolysis products underwent oxidation before being emitted. The investigation of the coal combustion process suggests the importance of reducing volatiles to control PM emissions, but the potential negative synergistic effects between PM reduction and increased carbon emissions should also be considered.

Relating alkali release from a wood pellet with combustion progress: A modified random pore model supportive study

This paper concerns a miniature gasifier fed with a constant ambient-pressure flow of air to study the pyrolysis and subsequent combustion stage of a single wood pellet at T = 800 ℃. The alkali release and the concentration of simple gases were recorded simultaneously using an improved alkali surface ionisation detector and a mass spectrometer in time steps of 1 s and 1.2 s, respectively. It showed alkali release during both stages. During combustion, the MS data showed almost complete oxidation of the charred pellet to CO2. The derived alkali release, “O2 consumed”, and “CO2 produced” conversion rates all indicated very similar temporal growth and coalescence features with respect to the varying char pore surface area underlying the original random pore model of Bhatia and Perlmutter. But, also large, rapid signal accelerations near the end and marked peak-tails with O2 and CO2 after that, but not with the alkali release data. The latter features appear indicative of alkali–deprived char attributable to the preceding pyrolysis with flowing air. Except for the peak-tails, all other features were reproduced well with the modified model equations of Struis et al. and the parameter values resembled closely those reported for fir charcoal gasified with CO2 at T = 800 ℃.

Assessment of sewage sludge as a component for the tire char co-gasification process

The work aimed to assess various sewage sludge (from coking, refinery, and fat-processing plants) as components for tire char co-gasification. The sewage sludge were analysed (basic characteristics, thermal stability, ash characteristics). Then, CO2 gasification and co-gasification measurements of individual materials and their blends (ratio: 70:30, 40:60) were made using the TGA, based on which the process and synergy effect were assessed. Moreover, a detailed analysis of char gasification formed during the pyrolysis was performed (reactivity assessment, kinetic parameters determined using the n-order Coats and Redfern model, and correlation between the individual elements in materials and their reactivity). Co-gasification measurements proved that the addition and increasing sewage sludge share in blends enhanced the process (TG curves were shifted towards lower temperatures, reactivity indicators, and final conversion degrees were improved compared to tire char). The greatest impact on the pyrolysis stage had the sludge from the refinery, while on the gasification stage sewage sludge from coking and fat-processing plants (where the synergy was observed). Moreover, the addition of sewage sludge to tire char reduces the activation energy and, in most cases, the pre-exponential factor. Finally, the correlation between reactivity and the Na, Mg, and P amount in the samples has been proved.

Novel insight into calcium-catalyzed steam gasification behaviors of lignite

Lignite is a low-rank coal with abundant reserves, and direct combustion causes serious environmental pollution. Calcium-catalyzed steam gasification is a cleaner technology that can convert lignite into high-value fuels and chemicals. However, the detailed structural evolution of calcium species during lignite steam gasification remains inadequately understood. The present work addresses this issue by subjecting the calcium-catalyzed steam gasification process of lignite to a detailed analysis, focusing on both the pyrolysis and gasification stages. The transitions in the chemical structures of the lignite and calcium catalysts during the pyrolysis stage were investigated in situ by Fourier Transform Infrared Spectroscopy. The morphological and chemical characterization of chars was performed using SEM-EDS, Raman spectroscopy, XPS, and N2 adsorption/desorption. The catalytic performance and gas composition were investigated by TGA and a fixed-bed reactor during the gasification stage. The results verify that the calcium catalyst reduced the initial gasification temperature of lignite by 150 °C, resulting in a 13.91% increase in the H2 concentration of the synthesis gas and an improvement of the H2/CO ratio to 20.96. The active Ca-C site and intermediate Ca-O-C formed during the co-pyrolysis stage increase the defect density of char, and the transformation of organic calcium species catalyzes the gasification of lignite. The enhanced concentration of H2 in the syngas can be attributed to the catalytic effect of CaO on the water–gas shift reaction during the gasification process. These results are expected to guide efforts in supporting catalytic conversion processes and promoting the efficient utilization of low-rank coal.

Study on microstructure evolution and oxidation kinetics in Coal-Oil Symbiosis

Differences in the spontaneous combustion mechanism characteristics of Coal-Oil Symbiosis (COS) significantly affect coal mines' safety management and ecological environment maintenance. Accordingly, this study aims to investigate COS's macroscopic and microstructural characteristics with different oil mass percentage using simultaneous thermal analysis, low-temperature N2 adsorption, scanning electron microscopy (SEM), and in-situ Fourier transform infrared spectroscopy (FTIR). The results showed that with the increase of oil mass percentage, the COS displayed the weakening of oxygen absorption and the advance of some characteristic temperatures, and 11.5 °C advanced the maximum weight loss temperature on average. For the 25 % oil sample, the ignition temperature was 9.5 °C lower than that of the raw coal. Additionally, the apparent activation energy of the high oil mass percentage sample was significantly reduced in the pyrolysis and combustion stages, and when the oil mass percentage was 25 %, the activation energies of the two stages decreased by 89 % and 60.65 %, respectively. Compared to raw coal, COS exhibits fewer macropores and surface pores covered by oil, which limits oxygen adsorption. Moreover, COS with higher oil mass percentage had an increase in hydroxyl and aliphatic hydrocarbon groups, and the CH3 + CH2 content of COS increased by 69.2 % on average, providing more active groups, thereby promoting spontaneous combustion. This study provides an important reference and theoretical support for further understanding the structural evolution and oxidation kinetic behavior of COS, contributing to disaster prevention and ecological environmental protection in coal-oil coexistence mining areas.

Lipid composition and algaenan structure of Botryococcus braunii race L revealed by sequential stepwise pyrolysis

The dried biomass and isolated algaenan of Botryococcus braunii (B. braunii) race L were analyzed using sequential stepwise pyrolysis at 50 °C intervals from 310 °C to 610 °C to investigate algaenan structure. Initial pyrolysis at 310 °C primarily produced free lipids mirroring the extracted products. At 360 °C, distinct isomers of lycopadiene and C40 isoprenoid ketone (i-C40 ketone), derived from the isolated algaenan, indicated the onset of biopolymer degradation. Intermediate pyrolysis (410–510 °C) yielded various isomers of lycopadiene and i-C40 ketone, along with minor short-chain isoprenoids. The consistent formation of C40 isoprenoid isomers up to 460 °C, followed by a decrease at 510 °C, suggested their presence in the algaenan. At 560 °C, high-temperature pyrolysis showed a bimodal distribution of C8 – C32n-alkane/n-alkene doublets, with a reduction in isoprenoids. This shift from isoprenoids to alkyl groups during pyrolysis reflects the diverse thermal stabilities of algaenan moieties. The consistent distributions of lycopadienes and i-C40 ketones during intermediate pyrolysis stages suggested they both present as side chain. The sustaining 9:1 ratio of lycopadienes to i-C40 ketones during intermediate pyrolysis suggests these components are linked to the main chain via ester groups, with a constant ratio of 9:1 in side chains. Aliphatic polyaldehyde, more resistant to be fractured, with a long linear chain serves as the main chain, capable of fragmentation to produce n-alkanes/n-alkenes. Functional group and alkyl moiety identifications were confirmed by FT-IR and NMR spectra. The results demonstrate that sequential stepwise pyrolysis provides detailed chromatographic profiles and transformation data, proving invaluable for understanding algaenan structures in modern microalgae and offers enhanced insights into functional groups and algaenan composition.

Kinetic, thermodynamic and artificial neural network prediction studies on co-pyrolysis of the agricultural waste and algae

The thermal decomposition behaviors of Maize straw (MS), algae (AL), and their blends were studied in a thermogravimetric analyzer to evaluate the bio-energy potential in this research. The blends neutralized violent reactions of each other at the second pyrolysis stage, and S and CPI respectively achieved the lowest points at 40%MS-60%AL and 60%MS-40%AL. The average Eα calculated by OFW, KAS, Starink and Friedman methods changed from 6.94 to 68.03 kJ/mol, 14.61–85.76 kJ/mol, 14.31–85.12 kJ/mol, respectively. When α was in range of 0.2–0.6, the Coats-Redfern method was calculated within 19.39 kJ/mol. KAS and Starink methods seemed more reliable. Reaction mechanism analyzed by Criado method show that AL was significantly different from that of MS. In addition, thermal degradation input by biomass types, heating rate and temperature were well predicted by artificial neural network (ANN). ANN 19 modal (3-5-15-1) was obtained the best (MSE = 0.0978 and R2 = 0.9999). The modal was utilized to predict the thermogravimetric curve without experiment, DTGmax of 70%MS-30%AL was the highest. While overfitting occurred in the high-temperature ranges (>700 °C). This study proves the potential of ANN modeling for producing derived energy from co-pyrolysis of biomass and other residues.

Pyrolysis characterization and kinetic analysis of typical coals in western China: effects of coal type, particle size and heating rate

ABSTRACT The three typical coals selected in this study (Shuangyi coal (SY), Hengsheng coal (HS) and Ningxia anthracite (NX)) are widely used in western China, but their pyrolysis characteristics have been less studied. In this study, based on the simultaneous thermal analysis-Fourier transform infrared spectroscopy (STA-FTIR) technique, the effects of different coal types, particle sizes and heating rates on the pyrolysis characteristics of coal powder were investigated. The results showed that the weight loss behaviors of different types of coals with different particle sizes varied, as influenced by the type of coal and heat transfer. When the particle size increased from 170 μm to 380 μm, the weight loss rate decreased by 2.95% and 24.45% for SY and NX coals while increased by 4.81% for HS coals; whereas for the maximum decomposition rate, both SY and HS coals showed an increasing tendency (increased by 2.76% and 9.32%), while NX coals decreased by 21.43%. The R2 of the three coal DTG curves fitted by subcurves was all 0.999, which proved that the nature of coal weight loss was the coupling effect of certain types of chemical reactions or covalent bond breakage. Real-time infrared spectroscopy was combined with covalent bonding to explore the major gas products and their influence by particle size. The activation energies at different temperatures were calculated by the Coats-Redfern method, in which the activation energies of the fast pyrolysis stage of HS coal were 1.68 and 2.75 times higher than those of the other two stages, 1.79 and 3.03 times higher than those of SY coal, and 1.99 and 1.11 times higher than those of NX coal, respectively.

Characterization and optimization of waste Cucurbita maxima moschata lashes for biomass composite applications

In this paper, 5 % sodium hydroxide solution, mixed 20 % acetic acid and 5 % sodium chlorite solution, and 5 % silane coupling agent solution were successively used to soak the waste pumpkin (Cucurbita maxima moschata) lashes. Subsequently, FTIR, XRD, thermogravimetric analysis and other experimental methods were used to comprehensively characterize the properties of the discarded pumpkin lashes. On this basis, this work prepared cement mortar specimens with unadulterated pumpkin lashes, adulterated raw pumpkin lashes, and adulterated modified pumpkin lashes, and their residual mechanical properties were investigated after exposure to elevated temperatures. The experimental results indicate that the chemical modification utilized in this paper can increase the cellulose content of pumpkin lashes as well as reduce the proportion of amorphous components, and thus, improve the tensile strength, crystallinity index, grain size, thermal stability, and surface roughness of the samples. Meanwhile, the chemical treatment process can effectively reduce the water absorption and density of pumpkin lashes. The calculation outcomes of our thermal kinetics study showed that the apparent activation energies corresponding to the main pyrolysis stage of the treated pumpkin lashes were significantly enhanced. The one-dimensional diffusion model and the second-order model could better characterize the pyrolytic mechanism of the raw pumpkin lashes, while the mechanism was closer to the third-order model because of the chemical modification. Finally, the addition of chemically modified pumpkin lashes reduced the mass loss rate of cement mortar specimens at elevated temperatures while clearly increasing the residual strength of the specimens at 300 and 400 °C compared to those with referential pumpkin lashes.

Distribution and characterization of products obtained from pyrolysis of cooked food waste- Impact of heating rate

This work offers a comprehensive investigation of the pyrolysis products—liquid, gas, and solid derived from cooked food waste (CFW) at different heating rates (15–100 °C/min). The heating rate significantly influenced the yield of pyrolysis products. The maximum yield of bio-oil (oil + aqueous) was achieved at a heating rate of 50 °C/min, py-gas at 100 °C/min, and biochar at 15 °C/min. The yields were 34 wt% for bio-oil, 30 wt% for py-gas, and 32 wt% for biochar. Analysis of the bio-oil revealed significant proportions of fatty acids (Methyl-methyltetradecanoate) and esters (Oleic acid ethyl ester), constituting 25 %, and 26 % at 15 °C/min but declining with increasing heating rates. Another ester (9-Octadecenoic acid methyl ester) was found across all heating rate with highest concentration of 33 % at 100 °C/min. Aliphatic hydrocarbons (Octane, Dodecene, Heptadecane, Tetradecyne, Undecane, Dimethylhepta-1,3-triene, Tetradecane, Nonadecane), constituted highest concentration of 12 % at 25 °C/min and aromatic hydrocarbons (Toluene) showed maximum presence of 4 % at 50 °C/min. The aqueous phase showcased cyclic nitrogenated compounds (Piperidine), anhydrosugars (DGP), and furanics (Furanmethanol), with the highest concentrations of 46 %, 12 %, and 38 %, respectively observed at 100 °C/min. Instantaneous py-gas analysis indicated an elevated presence of CO2 and CO in the initial pyrolysis stages (up to 70 min) followed by higher H2 in the latter stages (>70 min). While increasing heating rates (15–100 °C/min) boosted cumulative fractions of CO2 and CO, the highest H2 fraction was observed at 50 °C/min. The proximate and ultimate analysis of biochars indicated increased ash, fixed carbon, HHV and H/C compared to raw CFW. The surface area and morphology were positively influenced by an increase in heating rate, resulting in a microporous biochar having maximum surface area of 340.6 m2/g at 50 °C/min.