Low Heating Rates Research Articles

Experimental investigation on mechanical properties and fire performance of innovative wheat straw-gypsum composites as building sheathing panels

An innovative and high-performance wheat straw-gypsum composite (SGC) was developed to solve the problem of cracking and separation caused by water release when exposed to high temperature of gypsum board (GB) on the fire side of a wall. Compatibility between wheat straw and gypsum crystal was improved by combined pretreatment (i.e., sodium hydroxide and coupling agent) and adding magnesite. The mechanical properties of SGC were investigated and its fire performance determined by cone calorimetry and fire tests. The results indicated that the modulus of rupture, modulus of elasticity, and internal bond strength of SGC were 53.7%, 115.9%, and 173.9%, respectively higher than the traditional GB. The improvement in strength was attributed to the fact that alkali-treated wheat straw was well combined with gypsum crystals through magnesite to form a compact structure, as evidenced by scanning electron microscopy. SGC had extremely low heat and smoke release rate, ignition point at > 1200 s, and mass retention increased by 17.1%, compared with the literature results of gypsum-based bio-composites. Under a 60-min duration exposure, the charring depth of the wood studs of light frame walls sheathed with GB was 27 mm higher than that of SGC wall, and the bearing capacity retention rate of SGC wall 65.4%, while that of GB wall was lost. Errors between the calculation of bearing capacity proposed in this study and test values were < 6%. SGC with superior thermal insulation and mechanical properties could beneficially replace GB as fire-resistant panels in buildings.

Biochar gasification: Insights from pyrolysis atmospheres and gasification heating rates

Gasification is a promising technology for the synthesis of syngas and hydrogen, with char reactivity being a pivotal factor in the design of industrial gasifiers. Despite extensive studies on the gasification characteristics of biochar, the influence of the pyrolysis atmospheres on the evolution of biochar pore structure and its reactivity in gasification remains poorly understood. This study aims to bridge this gap by comprehensively investigating the effects of char preparation atmospheres (i.e., CO2, H2O, and N2) on ensuring gasification reactivities at varied heating rates. Biochars were synthesized in a horizontal tube furnace at 700 °C with a low heating rate (10 °C min−1) under three different atmospheres: N2, CO2, and H2O. Subsequent gasification reactivities were investigated using i) a thermogravimetric analyzer (TGA) at a low heating rate (10 °C min−1) and ii) a wire mesh reactor (WMR) at a high heating rate (1000 °C s−1), both under CO2 atmosphere at 950 °C. The results showed that the presence of an active atmosphere (CO2 and H2O) during pyrolysis significantly impacts the biochar’s aromaticity, crystalline structure, and surface morphology. The functional group concentration and surface area trends indicated that CO2 and H2O atmospheres during pyrolysis enhance biochar reactivity compared to the N2 atmosphere, with the highest reactivity observed for biochars produced under H2O. Furthermore, biochar gasification reactivity was markedly higher using the WMR compared to TGA, underscoring the pronounced effects of heating rate on gasification behavior. The high heating rate in WMR preserved the biochar’s porous and amorphous structure, whereas the TGA gasification encountered diffusional limitations and thermal annealing effects. These insights underscore the need to consider pyrolysis atmosphere and heating rate in gasification studies, offering a more comprehensive understanding of biochar’s behavior under practical gasification conditions.

Reactive Molecular Dynamics Simulations of Polystyrene Pyrolysis.

Polymers' controlled pyrolysis is an economical and environmentally friendly solution to prepare activated carbon. However, due to the experimental difficulty in measuring the dependence between microstructure and pyrolysis parameters at high temperatures, the unknown pyrolysis mechanism hinders access to the target products with desirable morphologies and performances. In this study, we investigate the pyrolysis process of polystyrene (PS) under different heating rates and temperatures employing reactive molecular dynamics (ReaxFF-MD) simulations. A clear profile of the generation of pyrolysis products determined by the temperature and heating rate is constructed. It is found that the heating rate affects the type and amount of pyrolysis intermediates and their timing, and that low-rate heating helps yield more diverse pyrolysis intermediates. While the temperature affects the pyrolytic structure of the final equilibrium products, either too low or too high a target temperature is detrimental to generating large areas of the graphitized structure. The reduced time plots (RTPs) with simulation results predict a PS pyrolytic activation energy of 159.74 kJ/mol. The established theoretical evolution process matches experiments well, thus, contributing to preparing target activated carbons by referring to the regulatory mechanism of pyrolytic microstructure.

Dynamic Thermal Treatments in Green Coconut Water Induce Dynamic Stress Adaptation of Listeria innocua That Increases Its Thermal Resistance.

The global coconut water market is projected to grow in the upcoming years, attributed to its numerous health benefits. However, due to its susceptibility to microbial contamination and the limitations of non-thermal decontamination methods, thermal treatments remain the primary approach to ensure the shelf-life stability and the microbiological safety of the product. In this study, the thermal inactivation of Listeria innocua, a Listeria monocytogenes surrogate, was evaluated in coconut water and in tryptone soy broth (TSB) under both isothermal (50-60 °C) and dynamic conditions (from 30 to 60 °C, with temperature increases of 0.5, 1 and 5 °C/min). Mathematical models were used to analyse the inactivation data. The Geeraerd model effectively described the thermal inactivation of L. innocua in both TSB and coconut water under isothermal conditions, with close agreement between experimental data and model fits. Parameter estimates and analysis revealed that acidified TSB is a suitable surrogate medium for studying the thermal inactivation of L. innocua in coconut water, despite minor differences observed in the shoulder length of inactivation curves, likely attributed to the media composition. The models fitted to the data obtained at isothermal conditions fail to predict L. innocua responses under dynamic conditions. This is attributed to the stress acclimation phenomenon that takes place under dynamic conditions, where bacterial cells adapt to initial sub-lethal treatment stages, leading to increased thermal resistance. Fitting the Bigelow model directly to dynamic data with fixed z-values reveals a three-fold increase in D-values with lower heating rates, supporting the role of stress acclimation. The findings of this study aid in designing pasteurization treatments targeting L. innocua in coconut water and enable the establishment of safe, mild heat treatments for refrigerated, high-quality coconut water.

Numerical studies on thermal processing of solid, liquid, and solid–liquid food products: A comprehensive analysis

AbstractThis article uses the computational fluid dynamics approach to analyze the thermal processing of solid, liquid, and solid–liquid food products. To understand the underlying transport phenomena, microbial deactivation, and nutrient degradation, three food products, viz. lamb (solid), grapefruit juice (liquid), and paneer cubes in a brine solution (solid–liquid), are studied. The food products are processed under constant retort temperature for fixed durations of heating and cooling. The numerical models are solved to obtain the velocity and temperature distribution inside the food products. The solid food exhibits a low heating rate at the slowest heating zone due to the absence of convection. The solid–liquid food shows uniform microbial destruction with a standard deviation of 2.27 min in the lethality distribution. The maximum possible average retention of nutrients is 90.36% (at 80°C and 59.81 min) and 60.64% (at 125°C and 21.30 min) for liquid and solid–liquid foods, respectively. However, the average thiamine retention in solid food monotonically decreases in the temperature range of 120–140°C.Practical ApplicationsThe computational fluid dynamics approach offers practical applications in optimizing food processing parameters, improving thermal processing equipment, and preserving nutrient quality in diverse food products. The analysis of the velocity and temperature distribution enables the design of more efficient heating and cooling methods, assisting food processors in determining the ideal duration and temperature to achieve microbial destruction while minimizing nutrient degradation. Furthermore, this approach facilitates the evaluation and enhancement of thermal processing equipment by identifying areas of slow heating or inadequate heat transfer, ultimately leading to improved design and more uniform processing. Understanding nutrient retention during thermal processing is vital for maintaining nutritional quality. The findings of this work could be applied to develop guidelines for preserving nutrients in specific food products. In summary, the computational fluid dynamics approach enhances food safety by optimizing processing parameters, improving equipment design, and preserving nutrients in solid, liquid, and solid–liquid food products.

Experimental Studies on Thermal Oxidation and Laser Ignition Properties of Al-Mg-Li Powders.

Powder ramjets are a kind of vehicle propulsion system with high specific impulse and efficiency. They provide significant benefits in terms of extended propulsion and thrust adjustment. The pursuit of a highly reactive fuel appropriate for powder ramjets is likely to stimulate advancements in innovative propulsion systems, which are crucial for deep space exploration and long-term space missions. This work presents experimental studies on the thermal oxidation and laser ignition performance of aluminum-magnesium-lithium powders at atmospheric pressure. TG-DSC curves of powders in three heating rates were obtained. The ignition processes and ignition delay times were recorded by a CO2 laser ignition experiment system at a laser power of 10~60 W. The results show that at a lower heating rate of 10 K/min, the powder's thermal hysteresis is less, and the powder energy released in stage I is more concentrated. However, the degree of heat release concentration approached a similar level at heating rates of 30 K and 50 K. The ignition delay time decreased as the laser flux density increased. When the laser flux density exceeds 80 W/cm2, the effect of laser power on the ignition delay time decreases. At atmospheric pressure, the mathematical relationship between ignition delay time and laser flux density is given. Finally, the powder ignition processes at different laser powers are represented graphically.

Reduction of phosphogypsum for SO2 production: Insights into the release characteristics of SO2 following the solid–solid reaction of CaS and CaSO4 under different atmospheres

AbstractPhosphogypsum (PG) severely pollutes the environment and is difficult to recycle. PG is primarily composed of CaSO4 · 2H2O. In this study, the characteristics of SO2 released from the solid–solid reaction between calcium sulphide (CaS) and CaSO4 were thoroughly investigated using thermodynamic calculations. Experiments were performed by tuning the molar ratio of CaS to CaSO4, reaction atmosphere (S, CH4, N2, and air), and the heating rate. As shown by the phase diagram, high reaction temperatures favour CaO stability, and the corresponding maximum SO2 equilibrium partial pressure increases. The total SO2 production significantly increased with increasing molar ratio and slightly increased when the ratio exceeded 1:3. The SO2 productions were ranked from highest to lowest as follows: S, CH4, N2, CO, and air. The total SO2 production decreased with increasing heating rate. For the reaction between CaS and CaSO4, a higher molar ratio of CaS to CaSO4 no less than 1:3, both S and CH4 reductive atmospheres, and a lower heating rate (2°C/min) favour the total SO2 emission.

Phase transformation kinetics of high-carbon steel during continuous heating

Effects of heating temperature, heating rate, and holding time on the austenitization process of near-eutectoid high-carbon steel have been investigated. The dilatometric tests were carried out at different heating rates of 1–100 °C/Sec. The Ac1 and Ac3 critical temperatures, the volume fractions of the parent and produced austenite phases, and consequently, the coefficient of the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation were obtained from dilatometric diagrams. The activation energy for the transformation was estimated using the Kissinger equation. The optical microscope was used for the microstructural characterization of samples austenitized at different temperatures and durations. The grain growth kinetics of austenite during processing was also characterized. Cellular Automata simulation was used to investigate the nucleation and growth of austenite from the initial full pearlitic structure. Based on the results, the activation energy of 242.6 kJ/mol at low heating rates (1 °C/Sec to 12 °C/Sec) and 436.94 kJ/mol at high heating rates (25 °C/Sec to 100 °C/Sec) were obtained, which indicated the different phase transformation mechanisms. This was attributed to the presence of boron, which postpones nucleation at grain boundaries and helps to activate the shear mechanism at high heating rates. Finally, a continuous heating transformation (CHT) diagram was drawn, which is an indispensable tool to consider the effect of heating rate on the austenitization process and austenite grain size.

Assessment of biochar developed via torrefaction of food waste as feedstock for steam gasification to produce hydrogen rich gas

In this study, the torrefaction of food waste was carried out using a thermogravimetric analyzer (TGA) to produce biochar and assess its suitability as feedstock for steam gasification. Torrefaction was conducted at temperature from 230 to 290 °C and the heating rate from 10 °C/min to 30 °C/min. Subsequently, the detailed characterization was conducted using proximate, elemental, lignocellulosic, nutrient analysis, and TGA analysis. The proximate and elemental analysis showed that biochar had the highest fixed and elemental carbon at the highest temperature (290 °C) and lowest heating rate (10 °C/min). Similarly, TGA indicated that increase in temperature increased the mass loss, however, increase in heating rate did not yield much change in mass loss. Additionally, lignocellulosic and nutrient analysis showed that lignin fraction increased (up to 80%) with increases in severity of the torrefaction due to significant decomposition of hemicellulose, cellulose, starch, proteins, and lipids. Thereafter, the kinetic parameters (activation energy, pre-exponential factor) of torrefaction of food waste were determined using the two-step decomposition model which showed a good fit with experimental data. Finally, the biochar developed was used for energy production using steam gasification which produced syngas with maximum yield of 3.75 m3/Kg and having hydrogen fraction of around 65% at the optimal conditions (temperature: 290 °C, heating rate: 10 °C/min).Graphical

Effect of heating rate on the kinetics of limestone calcination

This paper reports on the effect of heating rates between 0.1 °C/s and 205.0 °C/s on the thermodynamics and kinetics of limestone calcination in air. These heating rates are orders of magnitude higher than those used in the thermogravimetric analysers that have been reported previously (0.1 °C/s to 0.8 °C/s). It was found that the activation energy, E, is reduced by 59%, from 205.0 kJmol−1 to 84.5 kJmol −1, when the heating rate is increased from a low heating rate regime (<1 °C/s) to a moderate heating rate regime (99.2––205.0 °C/s). Additionally, the average reaction rate constant K¯ increases with an increase in the heating rate. As an example, for 205 °C/s, K¯ is 18.7 times higher than that for 0.2 °C/s, when approaching the same asymptotic temperature. It is also found that a higher heating rate increases the specific surface area (SSA), for the same Tas. This is caused by microfractures which are associated with decreased activation energy, and in turn increases the surface-to-volume ratios and speeds up conversion. The results highlight the importance of accounting for both heating rate and calcination time in the modelling of the calcination of limestone.Specific surface area measurements also revealed that the prolongation of calcination under moderate heating rate reduces the SSA, typically by a factor of 1.6 from 15.8 m2/g to 9.6 m2/g when the residence time tr is increased from 120 s to 240 s. Therefore, to maximize the SSA, the residence time should not be longer than that required for complete conversion.

Study on thermal response characteristics of encased propellants under laser irradiation

The laser safety of small and medium-sized flying units, exemplified by missiles, is crucial for ensuring their operational stability. In this regard, the response process of an encased propellant system comprising PBT propellant, stainless steel shell, and thermal insulation layer (EPDM) was meticulously captured during laser irradiation. The temperature distribution within the shell and insulation layer was determined through high-speed infrared thermography and finite element calculation. Results show that at a laser heat flux density of 2100 W/cm2, when the contact surface of the propellant reaches its ignition temperature, introducing a 1 mm insulation layer allows dissipation of 48.6-60.1% of the heat in the 0.5-1.6 mm shell beyond the laser irradiation range, significantly higher than the 3.1-12.2% observed without thermal insulation. Simultaneously, the ignition delay time increases from 0.45-0.75 s to 1.31-14.46 s. Theoretical calculations and experimental results confirm that replacing a portion of the shell with a thermal insulation layer achieves a lower heating rate of propellant with a thinner overall thickness, resulting in a longer ignition delay time. These findings have practical implications for enhancing the resistance of thin-shell targets, like rocket engines, against laser weapon interception.

Cure path dependency of damage resistance in interlayer toughened composite laminates subjected to quasi-static indentation and low-velocity impact

Cure cycle optimization reduces exotherms, defects and cycle times for thermoset composites, but may change the interlayer microstructure of toughened systems. The question remains, however, how the cure-dependent interlayer microstructure affects laminate mechanical properties. This work studies the effects of cure cycle heating rates on interlayer microstructure and damage resistance of interlayer toughened T800SC/3900-2 laminates, subjected to quasi-static indentation (QSI) and low-velocity impact (LVI). Results show that QSI damage resistance is affected by heating rate and interlaminar microstructure due to the cure-dependent delamination migration. Specifically, a lower heating rate causes separated particles, a thicker interlayer, and more fibre migration into the interlayer, which promotes delamination migration from toughened interlayer to brittle intralayer and consequently weakens the toughening effect. Less delamination migration retains the toughening effect for higher heating rates. In contrast, LVI damage resistance is independent of the cure cycle because delaminations remain in the toughened interlayer for all interlaminar microstructures.

Pyrolysis Kinetic Behavior and Thermodynamic Analysis of PET Nonwoven Fabric.

This research aims to maximize polyethylene terephthalate (PET) nonwoven fabric waste and make it as a new source for benzoic acid extraction using a pyrolysis process. The treatment was performed using a thermogravimetric analyzer (TGA) and released products were characterized using FTIR spectroscopy and gas chromatography-mass spectrometry (GC-MS). The pyrolysis kinetic and thermodynamic behavior of PET fabric was also studied and simulated using different linear and nonlinear models. The results show that the PET fabric is very rich in volatile matter (80 wt.%) and can completely degrade under 490 °C with a weight loss of 84%. Meanwhile, the generated vapor was rich in the carbonylic C=O functional group (FTIR), and the GC-MS analysis concluded that benzoic acid was the major compound with an abundance of 75% that was achieved at the lowest heating rate (5 °C/min). The linear kinetic results showed that PET samples had an activation energy in the ranges of 193-256 kJ/mol (linear models) and ~161 kJ/mol (nonlinear models). The thermodynamic parameters, including enthalpy, Gibbs free energy, and entropy, were estimated in the ranges of 149-250 kJ/mol, 153-232 kJ/mol, and 256-356 J/mol K, respectively. Accordingly, pyrolysis treatment can be used to extract benzoic acid from PET fabric waste with a 134% increase in the benzoic acid abundance that can be recovered from PET bottle plastic waste.

A Facile Aerobic Calcination Synthesis of Porous Oxygen‐Doped g‐C3N4 with High Adsorption Performance and Efficient Photocatalytic Activity

AbstractIn this study, porous oxygen‐doped graphitic carbon nitride (g‐C3N4) was successfully prepared via a facile aerobic calcination method using urea as the precursor. By adjusting the heating rate, the micro structural and the optical properties of this material were investigated. A series of characterizations indicate that the low heating rate is conducive to obtaining the g‐C3N4 possessing layered porous structure and large specific surface area. Meanwhile, it was found that narrower band gap (2.48 eV) and more effective carriers separation efficiency (2.54 ns) can be achieved by introducing oxygen dopants into the g‐C3N4, which is beneficial to the improvement of the photocatalytic performance. Additionally, the methylene blue (MB) wastewater degradation experiment was explored by using the porous oxygen‐doped g‐C3N4. It was demonstrated that the g‐C3N4 synthesized at low heating rate shows superior efficiency (99.1 %) for MB wastewater degradation treatment than the one synthesized at high heating rate (92.6 %). Thus, the porous oxygen‐doped g‐C3N4 obtains at low heating rate by aerobic calcination approach exhibits superior efficiency for dyeing wastewater treatment.

Thermal neuromodulation using pulsed and continuous infrared illumination in a penicillin-induced acute epilepsy model

Infrared neuromodulation (INM) is a promising neuromodulation tool that utilizes pulsed or continuous-wave near-infrared (NIR) laser light to produce an elevation of the background temperature of the neural tissue. The INM-based cortical heating has been proven as an effective modality to induce changes in neuronal activities. In this paper, we investigate the effect of INM-based cortical heating on the characteristics of interictal epileptiform discharges (IEDs) induced by penicillin in anesthetized rats. Cortical heating was conducted using a NIR laser light guided through a needle-like silicon-based waveguide probe. We detected penicillin-induced cortical IEDs from preprocessed micro-electrocorticography (muECoG) recordings, then we assessed changes in various temporal and spectral features of IEDs due to INM. Our findings show that the fast cortical heating phase obtained with continuous-wave NIR light is highly associated with a reduction of IED amplitudes, small but significant changes in the negative amplitude of IEDs compared with the baseline, and a proportional increase in the power of frequency bands related to delta/theta (2–8 Hz) and gamma (28–80 Hz) oscillations. Furthermore, a low rate of cortical heating with pulsed NIR illumination has a more inhibitory impact on the sharp negative polarity of IEDs. Our findings do not indicate a clear reduction in the frequency of IEDs in anesthetized rodents. In contrast, 2–4 min of continuous laser illumination leads to a notable increase in IED frequency. This effect of INM could potentially restrict its use in therapeutic applications related to epilepsy. However, the thermal effect of INM on cortical neurons induces changes in other characteristics of IEDs, which could prove beneficial for future applications.

Modified network kinetic model for coal pyrolysis with high-value products and low carbon emissions

Pyrolysis is a clean and efficient technology for the conversion of low-rank coal. Its key product is tar with high value. The complex composition of tar limits its further effective utilization. Although most kinetic models can provide the final distribution of three-phase products in coal pyrolysis, an effective prediction method for the specific composition of tar and gas has not yet been developed. Most numerical models serve to improve the total yield of volatile matter and cannot provide theoretical guidance for the improvement of tar quality or the reduction of carbon emission. Based on the basic assumptions of the CPD (Chemical Percolation Devolatilization) model for product molecules structure and generation mechanism, this paper proposed a more sophisticated method for dividing tar composition, which can achieve the division of light, medium, and heavy fractions of tar components according to boiling point. Light gas composition could be obtained with the combination of FG(Functional Group) submodel. The influence of pyrolysis final temperature, heating rate, and environmental pressure was explored for the yield and distribution of products of 18 coals. The simulation results showed that the total yield of tar was affected by both coal structure characteristics and operating parameters. Under conditions favorable for evaporation, such as low pressure and high temperature, the total yield of tar was positively correlated with the average aromatic core size in coal. Under other conditions, tar release was limited by its volatility. Coal with larger average aromatic core size corresponded to less tar yield instead. The pressure in the operating parameters had the most significant influence on the total yield of tar. The heavy fractions of tar are more sensitive to changes in operational parameters, making working conditions that increase the total yield of tar reduce tar quality. The overall carbon emission of pyrolysis is <1 kg CO2/kg tar, which is far lower than the 2–4 kg CO2/kg tar and 3–9 kg CO2/kg tar of direct and indirect liquefaction processes. Under the conditions of sufficient insulation time and no consideration of secondary reactions, the carbon emission of pyrolysis only depended on the content of carboxyl groups in the precursor functional groups. Therefore, the carbon emission intensity decreased with the increase of coal rank. For the optimization for total tar yield and tar quality, 1 atm pressure and 723–923 K temperature was optimal for low rank coals, while low temperature and heating rate with 10–20 atm pressure or high temperature and heating rate with 45–50 atm pressure were optimal for medium rank coals. For the optimization of light tar yield and tar quality, 6–9 atm pressure was optimal for low-rank coals, and 1–3 atm pressure was optimal for medium-rank coals.

Preparation of Mo2C by the temperature-programmed reaction between h-MoO3 and CO

In the work, the temperature-programmed reaction (TPR) between hexagonal-shaped h-MoO3 and high-purity CO under different heating rates was investigated in order to prepare Mo2C. Various technologies such as TG-DTA-DTG, XRD, FESEM, FT-IR and Raman spectrum as well as the thermodynamic calculation were adopted to analyze the experimental data. The results showed that the physically adsorbed water on the sample surface, the residual ammonium and coordinated water in the internal structure of h-MoO3 were successively released as the temperature increased, and then α-MoO3 and Mo4O11 were formed when the temperature arrived at around 791 K. Upon further increasing the temperature, the reduction process occurred and MoO2 will be generated. Thereafter, the carburization reaction was taken place and the subsequent reaction pathways were significantly different at lower and higher heating rates: at lower heating rates (8 and 12 K/min), the carburization process of MoO2 to Mo2C followed MoO2→MoO2+Mo2C→Mo2C + Mo→Mo2C; while at higher heating rates (16 and 20 K/min), the reaction pathways followed MoO2→MoO2+Mo2C→MoO2+Mo2C + Mo + MoOxCy→Mo→Mo2C, single-phase metallic Mo can be generated. The work also discovered that the as-prepared Mo2C always kept the same platelet-shaped morphology as that of the newly-formed MoO2; while due to the removal of oxygen and the decrease of molar volume during the transformation process, the as-prepared Mo2C exhibited a rougher and more porous morphological structure.

Promotion of bio-oil production from the microwave pyrolysis of cow dung using pretreated red mud as a bifunctional additive: Parameter optimization, energy efficiency evaluation, and mechanism analysis

To address the issues of high oxygen content and energy consumption in the microwave-assisted pyrolysis of biomass for biofuel production, this study used high-temperature pretreated red mud (RM) as an additive. The pretreated RM exhibited dual functionalities, namely microwave absorption and catalytic properties, during the microwave-assisted pyrolysis of cow dung (CD). This study also evaluated the optimization potential of energy recovery efficiency. The results showed that the addition of pretreated RM significantly increased the oil yield during the microwave-assisted pyrolysis of CD. The highest oil yield (59.63%) was obtained via the microwave-assisted pyrolysis of CD over catalysis with RM pretreated at 750 °C (RM750). Through the optimization of the RM750-to-CD mixing ratio, optimal oil quality and energy recovery efficiency were achieved. At a mixing ratio of 1:1, the pyrolysis oil featured the highest aromatic hydrocarbon content and lowest acid content. The high-temperature pretreatment of RM increased the Fe2O3 content, which enhanced the dielectric properties and magnetic loss ability of the reactants. This resulted in localized high temperatures and the formation of “hot spots,” which can promote the deoxygenation and hydrogenation reactions of oil. Consequently, the lower heating rate of oil increased from 35.12 to 40.11 MJ kg−1. The released oxygen escaped in the form of CO. In addition, pyrolytic char was used as an in situ microwave absorbing material owing to its increased Fe2O3 content and graphitization degree, leading to an increase in energy recovery efficiency from 4.71% to 9.98%. This study provides valuable guidance for the efficient utilization of diversified solid wastes and demonstrates the potential application of microwave-assisted pyrolysis technology in the resource utilization of solid wastes.

Kinetic analysis and pyrolysis behavior of pine needles by TG-FTIR and Py-GC/MS

The pyrolysis performances and reaction kinetics of pine needles (PN) were investigated by integrating thermogravimetric analysis, Fourier transform infrared spectroscopy, and pyrolysis-gas chromatography/mass spectrometry. The average activation energy of PN was estimated to be 183.2 kJ/mol by Kissinger Akahira Sunose (KAS) and 183.8 kJ/mol by Flynn Wall Ozawa (FWO), respectively at heating rates of 10, 20, and 40 °C/min. The pyrolysis of PN was found to be more efficient at the lower heating rates, while increased heating rates promoted the reaction. Using the King-Kai (K-K) method, the activation energies of hemicellulose, cellulose, and lignin were calculated to be 156, 165, and 172 kJ/mol, respectively. The descending order of evolving gases and functional groups from PN was found to be CO2, C=C, C=O, H2O, CH4, and CO. The main pyrolytic by-products identified were hydrocarbons, phenols, alcohols, ketones, and aldehydes. The determination of kinetic parameters provides fundamental information for predicting the rates at which chemical reactions occur. This study demonstrates the potential of PN as a suitable source for bioenergy.

Sodium salt surface interactions affect single particle combustion behavior of biomass, coal, and their chars

Sodium salt additions provide an effective route for tuning the combustion behavior of solid fuels. The salt-fuel surface interactions play a key role in combustion, as demonstrated by low heating rate experiments. High heating rate single particle studies have not investigated the effect of surface interactions and microstructural changes for sodium salt-treated fuels. In this work, the effect of three different sodium salt treatments were investigated on the single particle combustion characteristics of two distinct solid fuels and their corresponding chars. This approach probed the influence of microstructural changes and the formation of oxidation-resistive functional groups during high heating rate combustion. The separate characterization of biomass, coal, and their respective chars aimed at identifying the effect of sodium during different stages of combustion. The investigation encompassed Tunçbilek lignite (TL), olive residue (OR), and their fast pyrolysis chars (TLc and ORc) obtained from a wire mesh reactor at 600 °C. Both pristine and char particles were treated with Na2CO3, NaOH, and NaAlO2 to investigate the catalytic/inhibiting effects at different stages of combustion, namely, ignition, volatile combustion, and char combustion. All samples were burned as single particles at a high heating rate, WMR (1600 °C s−1). Treated OR samples provided earlier ignition reaching ∼ 0.4 s for OR-OH and shorter char combustion times around ∼ 2.8 s mg−1 for OR-CO3. On the contrary, treated TL samples depicted slightly higher ignition delay (3.0 s for TL-OH) and prolonged char combustion (11.2 s mg−1 for TL-OH) compared to TL (2.3 s, 8.2 s mg−1). Treated TLc samples also exhibited higher ignition delay due to the hygroscopic behavior of the sodium salts, which is more pronounced in TLc-OH (5.5 s). All treated chars exhibited shorter char combustion times except TLc-OH. Overall, sodium salt additions improved characteristic combustion times of biomass and chars while inhibiting those of lignites. The inhibitive effect of sodium salts on treated OR and ORc samples was more pronounced for TGA experiments due to the alkali interaction with the lignocellulosic component and a prolonged heating-up period. The findings demonstrate the importance of high heating rate characterization to accurately understand the sodium salt additions on combustion performance.