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In this paper, the synthesis of 2,4,6-trinitrophenol from phenol was improved in the range of 0–65°C, and the yield was 79.4%. The effectiveness of the synthesis process was confirmed by Nuclear Ma...

Coal-based activated carbon (CBAC) is widely used in several industrial processes and daily life, however, it is susceptible to spontaneous combustion during storage and transportation. Therefore, ...

Thermal power is the main source of electricity in Taiwan, where coal is the primary fuel. However, concerns for potential fire and explosion hazards caused by coal dust are increasing. The problem regarding the storage or transportation process of coal cannot be neglected. This study explored four coal dust samples obtained from the three regions of South Africa, Russia, and Australia; the particle size D50 of all the samples was

A two-phase closed thermosyphon (TPCT) with a CuO–H2O nanofluid was used to effectively harness the internal accumulation of thermal energy from a coal pile, formerly subject to the risk of spontaneous combustion. The heat transfer effect of different insertion ratios of the TPCT (evaporation section:condensation section = 1:3, 1:2, and 2:3) and inclination angles (30°, 45°, 60°, and 90°) was investigated for bituminous coal. The results indicated that the heat transfer effect of the insertion ratio, in descending order of preference, was 2:3 > 1:2 > 1:3. When the TPCT insertion ratio was 2:3, the maximum temperature difference was up to 37.7 °C. The heat transfer effects of the TPCT were strengthened when it was inserted at a given angle. In decreasing order of effectiveness, the tested inclination angles showed the following order of preference: 60° > 30° > 45° > 90°. Therefore, 60° was the optimal insertion angle. In general, TPCT has the optimal transfer effects when the insertion ratio is 2:3 and the inclination angle is 60°.

The thermokinetics and gaseous products of Jurassic coals collected from northern Shaanxi, China at four different heating rates were determined via thermogravimetry-Fourier transform infrared spectroscopy experiments. The results showed that the trends of thermogravimetric pyrolysis and oxidation curves were divided into three stages and five stages, respectively, and presented the same variations. As the heating rate increased, their curves moved the high temperature. In addition, the characteristic temperatures indicated that the coal samples had a relatively significant spontaneous combustion tendency. In the stage of water evaporation and gas desorption, the rates of formation of CO and CO2 went up promptly, and gaseous water produced during the oxidation reaction began to increase, but its generation rate was lower than that in the stage of oxygen absorption and mass increase. The apparent activation energy (Ea) showed a characteristic jump with increasing temperature, and the optimal mechanism function was chosen by integration and differentiation. Moreover, the relationship between Ea and lnA was linear, which indicated that there was a kinetic compensation effect.

To explore the micromechanism of the structural changes of anthracite due to heat accumulation by water and pyrite, during oxidation, anthracite with coal samples was selected in this work from Baijiao Coalmine, Sichuan, China. The samples were added with water of 1, 5, 10, 15, and 20 mass % and pyrite of 1, 2, 4, and 6 mass % and were conducted to experimented torts. As compared with the raw coal sample, the effects of water and pyrite on the microstructure of anthracite were studied. The results indicate that the oxygen-containing functional group of coal increases with the addition of water. The content of the aromatic structure in coal was thought to be due to water and pyrite synergistic effects. The synergistic effect of water and pyrite accelerates the oxidation process of seven types of active groups in coal samples. The water content was 10-15 mass %, and the associated pyrite content was 2-4 mass %; the contribution to the oxidation activity of the main active groups of coal was the largest under oxidizing conditions.

Spontaneous combustion of coal has become an important disaster that threatens the safety of coal mines. FeS2 is the main component of pyrite, which is suspected to be a major contributor to coal spontaneous combustion (CSC). So, it has important significance to FeS2 on the characteristics of coal oxidation for prevention and treatment. This study used coal samples mixed with different proportions of FeS2 (2.0 mass%, 4.0 mass%, and 6.0 mass% mass percentage) were tested to investigate the characteristics of spontaneous combustion, as compared with the fresh sample. The CO and CO2 production rates, critical temperature, and dry cracking temperature during oxidation were analyzed. The temperature-programmed experiments was conducted to simulate low-temperature oxidation processes realistically. In-situ infrared spectroscopy was used to appraise the evolution of low-temperature (

Coal spontaneous combustion (CSC) has become a safety topic and has been widely debated. This study investigated the inhibiting effect on CSC by using a series of novel ionic liquids (ILs) as chemical inhibitors. The microstructure and thermokinetic characters were observed and evaluated by Fourier transform infrared spectroscopy and synchronous thermal analyser. The results indicated that ILs could destroy reactive groups on relatively active coal surfaces, such as OH, aliphatic C H, and O-containing groups. However, as aromatic CH is the main chain of coal molecule, damaging it is difficult. Different anions and cations found in ILs exhibited different abilities for destroying the groups on the surface of coal molecules. The damage was caused by the properties of anions and cations by affecting the chain length, number of chains of the anion and cations, and electronegativity strength. The changes in microstructure increased the physical adsorption capacity of inhibitive coal samples during low-temperature oxidation, which changed the characteristic temperature points. In stages of water evaporation and desorption mass loss (stage 2) and the thermal decomposition (stage 3), the apparent activation energy of coal samples increased. The kinetic characteristics of the obstructed coal sample were predicted using the Flynn–Wall–Ozawa method. The development ability was delayed and the risk level was reduced of CSC in stages 2 and 3. Therefore, ILs should be utilised at relatively low-temperatures (

To prevent coal fire disaster, a precision grading warning method was previously proposed for coal seams that are susceptible to spontaneous combustion. The uncertainty in the reaction mechanism of...

Jurassic coal samples from Liuhuanggou (LHG) and Wudong (WD) coal mines, Xinjiang Province, China, were selected for oxidative thermal energy experiments. A temperature-programmed experimental system measured the variation of gaseous products and the changes in thermal energy release with temperature. Thermokinetic parameters, namely the apparent activation energy (Ea) and pre-exponential factor (A), of the coal samples for four heating rates were determined using a thermogravimetric analyser. During the low-temperature oxidation stage, two samples had temperature curves characterised by their production levels of the index gas (CO); the temperature changes were approximately equal, but the critical temperatures differed. The WD sample produced less CO gas. However, the maximum and minimum exothermic strengths of the two samples had some similarities to the temperature change curves. The characteristic temperatures for the coal samples were discovered using different heating rates. For the WD sample, the characteristic temperature varied according to the heating rate, and the thermogravimetry (TG) and derivative TG curves of the samples lagged with an increase in the heating rate. The characteristic temperatures of the sample increased with the increase in the heating rate. Isokinetic analysis (the Flynn–Wall–Ozawa and the Kissinger–Akahira–Sunose models) was used to calculate the thermokinetic parameters of the sample. The range of the heating rates was 2 to 15 °C min−1 for oxygen concentration of 21 vol%, and the Ea of the samples decreased with the increase in the heating rate.

To clarify the effect and mechanism of oxygen supply, particle size, and dust concentration on the flame propagation behaviours and explosion characteristics of cornstarch dust cloud, a 3D numerical simulation for simulating the explosion process of cornstarch dust cloud were conducted and verified with experimental data using a 20-L sphere. Next, flame behaviours and explosion parameters under different conditions were investigated using numerical calculation and experimental observation. Results revealed that: flame propagation during the whole explosion process can be divided into four various stages according to the CFD simulation. Temperature fluctuation, dust agglomeration, and three different zones can be distinguished from the flame configuration. Oxygen supply, particle size, and dust concentration pose different impact trends to the initial flame behaviours and explosion parameters. The flame length varied linearly over time while oscillation phenomenon can be found in flame velocity at both the horizontal and vertical directions.

Coal spontaneous combustion (CSC) characteristics were identified by their different types of coal. In this study, the samples of lignite, non-caking coal, lean coal, and anthracite were chosen to ...

This work investigated the influence of particle-injection pressure and ignition delay on explosion parameters of methane–coal particle mixture using a 20-L sphere. Results indicated that the maximal explosion pressure Pmax and the maximal pressure rise rate (dP/dt)max tended to first increase and then decrease, with ignition delay increasing as the particle-injection pressure ranged from 1.2 to 2.4 MPa, attaining their maximum values at different moments. However, as the particle-injection pressure reached 3 MPa, Pmax and (dP/dt)max displayed a downtrend with an increase in ignition delay. Furthermore, a 3D CFD model was developed to evaluate the turbulent flow field and the gas-solid particle interaction within the tank. Results demonstrated four continuous stages for transient movement of coal particles. Under various particle-injection pressures, the time for particle dispersion stabilization differed significantly. These results can potentially contribute to the prevention of methane–coal particle explosions.

Pulverized coal cloud deflagration in a methane–oxygen atmosphere is a fairly intricate process owing to transient turbulent combustion accompanied by gas–particle premix flow. We developed a comprehensive computational fluid dynamics model that considers gas–solid two-phase flow, interaction between gaseous and discrete coal particles, and homogeneous–heterogeneous reactions. Numerical results revealed nonconforming and random particle temperature at different instants. The temperature threshold and distribution of high-temperature particles were quantitatively and qualitatively analyzed using the simulation results. Particle accumulation and agglomeration reported for previous experiments was verified and interpreted using turbulence theory. In addition, we analyzed the coupling and heat-mass transfer between coal particles and gas. This investigation has yielded the detailed mechanism of heat transfer for a dust explosion and provided valuable information for prediction, precaution, and control of an explosion involving discrete particles.

To investigate the impact of oxygen for the feature parameters of the coal oxidation process, the coal samples were selected from mines of Liuhuanggou and Ewirgol in Xinjiang Province, China. TGA/DSC–FTIR was employed to conduct the coal mass, heat, and functional groups under oxygen concentrations of 3, 6, 9, 15, and 21 vol% from 30 to 950 °C. In the entire coal–oxygen reaction, the characteristic temperatures were divided into T1 (adsorption temperature), T2 (oxygen-adsorption mass-gain starting temperature), T3 (oxygen-adsorption mass-gain maximum temperature), T4 (ignition temperature), T5 (max mass loss rate temperature), and T6 (burnout temperature). The results indicated that with the decrease in oxygen concentration, the feature temperature point gradually transferred to the high-temperature area. The coal samples maximum exothermic temperature rose, the maximum exothermic power decreased, and the net thermal release decreased along the entire reaction process of coal sample. The feature temperature excursion of the coal–oxygen composite reactive incurred the hysteresis effect, which was obvious when the oxygen concentration was 3 vol%. Furthermore, the content of main functional groups of coal microstructure was the highest at T2, and the content gradually decreased with the temperature increase continuously. As the increase in oxygen concentration, the content of main functional groups increased. Among them, there was no considerable change in the hydroxyl content in the coal microstructure on the characteristic temperatures of 75, 140, and 350 °C. As the temperature rose to 140 °C, the content of main functional groups with a varying degree grew. When the temperature reached 350 °C, the oxygen-containing functional group began to decrease.

External short circuit has a severe influence on lithium battery’s performance. Currently, a huge study has focused on the single battery’s short circuit. However, cells are often interconnected into a module in real applications. There are many possibilities that external short circuit of a single cell has huge impact on the other cells in a battery module. In this research, experiments were conducted under different conditions (single lithium-ion battery, 3 lithium-ion battery modules, 9 lithium-ion battery modules) at different ambient temperatures (30, 40, and 50 °C) and different state of charge [SOCs (80%, 90%, 100%)] The temperature of the battery surface (positive electrode, middle) rose during external short circuit. The variation of the battery temperature was analyzed. Then, the variation of battery performance parameters under external short circuit conditions was studied. All lithium-ion batteries were divided into two groups, one being an external short circuit and the other being not short-circuited externally. As a result, when the lithium-ion battery was short-circuited externally, the battery temperature rose rapidly to the maximum temperature that the battery can rise. The highest temperature caused by external short circuit appeared in the case of a single battery. The higher the SOC, the faster the battery temperature rose. In the cycle charge and discharge, the rate of decay of the battery after an external short circuit was twice faster than that of a normal battery. As the temperature increased, the rate of battery capacity decayed further. Under normal circumstances, the attenuation of the battery to 80% required about 350 cycles. The life of the battery after the external short circuit was shortened by more than half, and when the temperature rises, even only about 100 cycles were required.

To study the similarities and differences in the macrocharacteristics of a coal seam during low-temperature oxidation at different regions of the same coal mine, six coal samples from the 13-1 seam were selected from Huainan, Anhui, China. The macroscopic spontaneous combustion characteristics, including the gaseous products and characteristic temperatures, during the low-temperature oxidation of samples from different regions of the same coal seam, were studied using a temperature-programmed test. The results revealed that the characteristic temperatures of the samples from the coal seam were close to each other, the critical temperature range was 70–80 °C, and the crack temperature range was 90–100 °C. The CO/O2 ratio varied considerably. Thus, the degree of incomplete oxidation reaction to release CO was different at different regions in the coal seam. Moreover, the variation in the CO/CO2 ratio of the samples from the coal seam was similar. A calorimeter (C80 Calvet, SETARAM, France) was adopted to explore the exothermic characteristics of the coal seam during low-temperature oxidation. The exothermic onset temperature of the samples from the coal seam was similar, with a range of 50.1–54.3 °C. Differences were observed in the total thermal energy released by oxidation at low temperature in the samples from the coal seam; however, the percentage of thermal energy release at low temperature and that during the entire oxidation process was similar. The changes in the apparent activation energy of coal specimens from the seam were similar. It was, and is, important to investigate the prediction and prevention technique of spontaneous combustion in regional coal seams.

Coal spontaneous combustion (CSC) is a major problem in coal mining. In the vicinity of underground goaf, secondary or repeated oxidation processes of the residual coal inevitably occur, increasing the risk of coal fires. In this study, the thermal reaction behaviour of two types of raw coal samples and three preoxidised coal samples with different oxidation temperatures (80, 130, and 180 °C) were investigated. The physical and chemical properties of the samples were measured using thermogravimetric analyser-Fourier transform infrared spectroscopy (TGA-FTIR) with heating rates of 1.0, 2.0, 5.0, and 10.0 °C min−1. According to the characteristic temperatures in the heating processes, the entire CSC procedure can be divided into three stages: oxidation, combustion, and burnout. The results indicated that the aliphatic side chain lengths of preoxidised coal were shorter, and the number of branched aliphatic side chains was lower than that of raw coal. Furthermore, the model for the mechanism of preoxidised coal differed from that of raw coal. Average values of the apparent activation energy of the preoxidised coal samples were lower than those of the raw coal samples. Therefore, compared with raw coal, preoxidised coal requires less energy to react and more readily undergoes spontaneous combustion.

In view of the coal and gas outburst accidents occur frequently caused by blasting in geological structural belt, in order to study the mechanical characteristics of coal rock in tectonic belt disturbance by blasting and blasting vibration effect influenced on the stability of surrounding rock, coal–rock damage and failure characteristics within a reverse fault caused by a blasting stress wave were investigated using numerical analyses and experiments. According to the experimental results, the causes of coal and gas outburst dynamic disasters within a reverse fault during blasting are analyzed. The outcomes indicated that the crushing circle created by the crack propagation near the blasting hole severely damaged the fault plane and floor rocks adjacent to the footwall of the reverse fault. Fractures also extended to the upper and lower coal seams of the reverse fault; this caused the surface of the coal seam to fall off and severe internal damage. According to theoretical analysis, the reflection of the blasting stress wave propagating to the reverse fault intensified the damage to coal and rock. Elastic strain energy accumulation within the reverse fault structural zone was accompanied by high-stress concentration. The reverse fault tectonic region was destroyed by blasting vibration. It increased gas pressure and caused a weak surface, which provided a channel for gas flow and a dynamic basis for the occurrence of coal and gas outburst. The research results have important theoretical value to reveal the mechanism of coal and gas outburst in tectonic belt induced by blasting.

Coal, a flammable substance, is affected by spontaneous weathering and can be hazardous when exposed to thermally unstable conditions. Over the past few decades, numerous chemical disasters involving coal have occurred, resulting in many deaths. Therefore, strategies for the prevention of such disasters must be implemented to ensure human safety, avoid financial losses, and minimise adverse environmental effects. This study determined the thermal safety parameters and thermal hazards of lignitous and long flame coal by using thermogravimetry and differential scanning calorimetry. The characteristics of the functional groups in coal and treated coal were observed through Fourier transform infrared spectrometry. The structures of coal and coal treated with an ionic liquid, namely 1-butyl-3-methylimidazolium, were observed through scanning electron microscopy. Finally, theoretical kinetic models were applied to calculate thermokinetic parameters and identify the degree of thermal hazard present during periods of thermal instability. The results revealed that 1-butyl-3-methylimidazolium nitrate considerably reduced the probability of coal spontaneous combustion and the degree of hazard for long flame coal. Therefore, this ionic liquid could serve as an effective inhibitor of spontaneous combustion in long flame coal.

Coal spontaneous combustion (CSC) is a global, long-standing thermal hazard in coal mining that causes serious environmental damage, particularly in developing countries. Ionic liquids (ILs) are environmentally friendly, green, economical, and a new type of fire-preventing material that inhibits coal oxidation and alleviates thermal production. In this study, 1-butyl-3-methyl imidazole tetrafluoroborate ([BMIM][BF4]) and 1-butyl-3-methyl imidazole ([BMIM][I]) at various mass ratios (0.0, 0.5, 2.0, 5.0, and 10.0 mass%) were used to treat three types of coal (lignite, 1/3 coking coal, and anthracite) for CSC. The combustion-mass loss and thermal release rate of ILs treated relative to untreated coal samples were investigated using a synchronous thermal analyzer, and the optimal addition mass ratio of ILs was predicted. Not only do ILs have the most efficient inhibiting effect, but they also consider the economic benefit. Per thermogravimetric-differential scanning calorimetry, for the content of 5.0 mass% [BMIM][BF4], the inhibiting effect is favorable for universal applications. In addition, coal samples treated with 5.0 mass% [BMIM][BF4] were subjected to programmed-temperature heating experiment testing. The oxygen consumption rate, inhibiting effect, as well as apparent activation energy, were determined. The inhibiting effect at 120.0–150.0 °C was the most obvious, which provided the basis of the application for CSC prevention.

To investigate the spontaneous combustion risk of pulverised coal, the low-temperature oxidation heat flow of three metamorphic pulverised coals was measured using a C80 microcalorimeter system at various oxygen concentrations to investigate the spontaneous combustion risk of pulverised coal. The results indicated that low-temperature exothermic oxidation of pulverised coal occurred in stages that had distinct characteristics. When the temperature increased, the heat flow curve of RNM and QM pulverised coals first decreased, then increased, and finally decreased, but the heat flow curve of the PSM pulverised coal first decreased and then increased. A considerable lag was observed in the heat flow curves with the decrease in the oxygen concentration, and the characteristic temperature increased. Stage 1 released the least heat, whereas stage 3 released the most heat. A decrease in the oxygen concentration considerably reduced the heat release of pulverised coal. A spontaneous combustion risk index was proposed on the basis of low-temperature oxidation heat release of pulverised coal. Decreased oxygen concentration and high metamorphism of pulverised coal considerably reduced the spontaneous combustion risk index.

Although numerous fire accidents in wind turbines had been reported, there were few relevant literatures on the fire hazard of oil system in wind turbine. This study focused on thermal hazards and decomposition characteristics caused by temperature variation for the wind turbine oil system. The thermal decomposition behavior and fire hazard potential of the lubricating oils (hydraulic and gear oils) and transformer oils used in wind turbines were investigated through a simultaneous thermogravimetry analyzer using non-isothermal models. Fourier transform infrared (FTIR) spectroscopy was used to analyze the change in functional groups of three oils. The results demonstrated that the thermal decomposition process of the lubricating and transformer oils could be divided into three stages, with major mass loss in the second stage. The temperature associated with 17.5% mass loss could estimate the flash point of three oils, which facilitated to detect the fire hazard potential well on time. The FTIR results showed that during the oxidation of the transformer oil, a peak appeared at 1736 cm−1, corresponding to the C O of carbonyl compounds. The findings can be used as a reference to monitor the intrinsic safety and to provide a basis for timely replacement of oils in wind turbines.

Coal spontaneous combustion is characterized by high-temperature oxidation and microscopic mechanisms. These are essential aspects to understand when attempting to control or prevent spontaneous combustion. Three fresh bituminous coal samples were collected for experimentation from Huainan, China. X-ray diffraction and Fourier-transform infrared spectrometry were conducted to determine the microscopic characteristics of coal during high-temperature oxidation. The mineral structures and functional groups were ascertained to ensure that the original structural characteristics of the coals were obtained. Thermogravimetry–differential scanning calorimetry was used to divide the high-temperature oxidation into four substages and obtain detailed exothermic characteristics. The heat energy release exhibited a positive correlation with an increase in temperature. Moreover, to investigate the relationship between the functional groups and their exothermic characteristics, correlation analysis was conducted for describing the quantitative phenomena within the four oxidation stages. The results revealed that the oxygen-containing groups were initially the most active and reactive among the 14 types of functional groups. The most rapid stage of spontaneous combustion, in which should be the most cautious and aware of risks, was the oxygen adsorption and mass gain stage because the heat energy output increased rapidly and passed this stage, thus leading to dangerous and possibly unrecoverable situations.

In underground mines, high air temperatures in the summer months lead to an increase in inlet airflow temperatures. This leads to seasonal thermal pollution in the mines. This paper examines the dynamics and effects of seasonal variation in surface air temperatures and surrounding rock temperatures in deep coal mines. It also examines temperature variations in the main ventilation circuit, working face, and surrounding rock. The study results revealed that airflow temperatures were significantly affected by seasonal air temperature variations. The greater the distance was between the inlet and the wellhead of the ventilation shaft, the less the effect was on temperature. Moreover, slight temperature variations (1.0–3.0 °C) were observed between various points on the return route during the summer months. Airflow temperatures along the airflow inlet to the return route of the working face first decreased, but then increased. The temperature field of the surrounding rock increased gradually with increased distance between the mine roadway and inlet, with recorded rock temperatures as high as 40.53 °C. The radius of the heat-adjusting layer was between 28 and 33 m.

The rapid surge in global energy needs has paved way for the development of various alternatives to natural resources every now and then. However, dependence on coal-based energy has not reduced greatly. Thus, massive quantities of coal fly ash (CFA) are generated worldwide, which is a serious threat to ecology owing to constraints associated with its storage and disposal. There exists a pressing and ongoing need to develop new, and green product streams from CFA to reduce the threat to the environment. The present review begins with an emphasis on the generation, physicochemical properties, and potential dangers of CFA. Then, it focuses on impending applications such as synthesis of geopolymers (alternative to cement), silica aerogels (insulating materials), carbon nanotubes (carbon allotropes) for electronic devices, and the separation of radioactive isotopes as well as rare earth elements from CFA. Furthermore, the review analyses factors restraining the motive for effective management strategies that drives utilisation of CFA (either in raw and processed state) for new product streams. Finally, the review elucidates the role of CFA as an emerging input in delivering eco-friendly amenities and future derivatives.

Low-temperature nitrogen and isothermal adsorption experiments were conducted on six typical low-rank coal samples from the Fukang mining area, Xinjiang, PR China. Using different temperatures, the effects of the coal’s pore structure on gas adsorption and other thermodynamic characteristics were analyzed. The Clausius–Clapeyron equation was used to calculate the isosteric heat of adsorption, and the standard adsorption equilibrium constant was derived to calculate the adsorption free-energy and entropy. The relationships between pore structure characteristics and gas adsorption thermodynamic parameters were investigated. The results showed that the adsorption free-energy and enthalpy of the coal samples decreased with an increase in temperature. Adsorption heat and adsorption entropy were affected by an increase in pore volume and specific surface area. The specific surface area and transition pore volume exhibited quadratic relationships with the free-energy and total pore volume, whereas the mesopore volume exhibited a positive linear relationship with the adsorption free-energy. No prominent relationships among average pore diameter, adsorption heat, adsorption free-energy, and adsorption entropy were observed. No correlation was identified between micropore volume and adsorption free-energy. Fractal dimension was linearly and positively related to the adsorption heat and entropy but had no effect on the free-energy.

To explore the macroscopic characteristic indexes for oxidation of coal under high-temperature conditions, an XKGW-1-type high-temperature-programmed heating experimental system was constructed. Tests on high-temperature oxidation of coal under high-temperature conditions at five oxygen concentrations of 21, 17, 13, 8, and 3 vol% were independently conducted. Laws of variation in high-temperature oxidation of coal indices, such as the coal temperature, gas ratios, rate of oxygen consumption, and exothermic strength from indoor temperature to 500 °C, were investigated at those oxygen concentrations. The results showed that the variation tendencies of characteristic indices for high-temperature oxidation of coal at different oxygen concentrations were extremely intricate. At the five oxygen concentrations, the rate of oxygen consumption increased rapidly with an increase in coal temperature and eventually remained at a higher range. The rate of oxygen consumption increased with temperature with an approximate exponential trend at the five oxygen concentrations tested. For the same coal temperature, the rate of oxygen consumption decreased with the oxygen concentration. The variation tendencies of the CO and CO2 production rates were similar, both increased rapidly with an increase in coal temperature in the early stages and reached a maximum at a coal temperature of 380 °C. They decreased slightly with an increase in coal temperature at first and increased promptly thereafter. The concentrations of CH4, C2H4, and C2H6 first increased with an increase in the coal temperature and markedly decreased after the maximal value. The temperatures for the extreme points were 480, 410, and 420 °C for CH4, C2H4, and C2H6, respectively. The trends of the macroscopic characteristic indexes throughout the process of high-temperature oxidation of coal in a certain temperature range at various oxygen concentrations can be used for temperature prediction and fire prevention during coal mining.

In mining, coal is crushed into particles of various sizes. The size of these reactant particles affects the combustion risk profiles in mine safety, thus affecting industrial safety considerations. Therefore, this study explores the influence of particle size on hazardous gas emissions during the high-temperature oxidation of coal. A custom-designed and built high-temperature experimental system was developed and implemented. This practical experiment was conducted with the aforementioned system to analyze three coal samples from Huainan, Anhui Province, China. The gas concentration data were recorded for carbon monoxide, carbon dioxide, alkanes, and alkenes, with six different particle sizes, and covered a temperature range of 30 to 500 °C. As the oxygen consumption rate and normal temperatures are equally strong influential factors of spontaneous combustion, the oxygen consumption rate was simultaneously captured using the indicator gas growth rate method to determine the five characteristic temperatures was captured using the indicator gas growth rate analytical method. The five characteristic temperatures for the six particle sizes were determined as follows: critical, crack, active, speedup, and ignition.

The effects of ionic liquids (ILs) on the macrostructures and characteristic parameters of coal samples during low-temperature oxidation (30.0–200.0 °C) were investigated. The Fourier transform infrared (FTIR) spectroscopy results clearly illustrated that the destruction of functional groups in the coal molecular structure was prominent, and that the benzene rings in the coal molecular structure were barely affected. Therefore, it can be inferred that ILs played a primary role in the destruction of functional groups in the side chain of the coal molecular structure; thus, the aromatic ring was barely affected. Moreover, the inhibition of the functional group at high temperatures by the ILs was also barely effective. The analysis results of the temperature-programmed testing system indicated that the CO concentration and the production rate of CO by coal samples treated with the ILs presented decreasing trends. This result was in sound agreement with the FTIR results for the quantity of carbonyl groups in oxidation stage. The oxygen consumption rate of the sample treated with the ILs gradually decreased beyond the cracking temperature. Moreover, the difference between the thermal release intensity of coal samples treated with the ILs and that of raw coal gradually increased beyond the critical temperature. The inhibiting effect of [Bmim][BF4] appeared to be greater than that of other ILs, and [Bmim][I] and [Emim][BF4] exerted a slight influence on the low-temperature oxidation process of coal samples. Therefore, we conducted a comprehensive comparison of the inhibiting effect of four ILs on bituminous coal during low-temperature oxidation and found that the ILs can be listed in the following order on the basis of their inhibiting effect: [Bmim][BF4] > [Bmim][NO3] > [Emim][BF4] > [Bmim][I].

Thermophysical properties govern the heat transfer during coal spontaneous combustion. Under different oxygen concentrations, the mass and heat intensity of three metamorphic levels of bituminous coal were investigated through synchronous thermal analysis, and their thermophysical parameters were tested using a laser-flash apparatus. The results indicated that as the oxygen concentration increased, the T3 (the temperature at maximum mass) and exothermic initial temperature slowly decreased. The changes in T1 (maximum adsorption temperature) and T2 (initial temperature at the oxygen-absorption and mass-gain stage) were nonsignificant. The effect of oxygen concentration on mass, heat intensity, and thermophysical parameters was primarily concentrated in high-temperature regions. As the temperature increased, the thermal diffusivity first decreased and then increased. The specific heat capacity gradually increased, then plateaued until it began to decrease; meanwhile, the thermal conductivity increased, first slowly and then quickly. A calculation model for different temperatures and oxygen concentrations was established through curve fitting.

Ionic liquids (ILs) are a type of environmentally friendly solvents. Several studies have proven that ILs can inhibit the spontaneous combustion of coal (SCC). In this study, a synchronous thermal analyzer was used to analyze the effects of the imidazolium-based IL [BMIM][BF4] on coal of three metamorphic grades. A coal sample exhibiting the optimal inhibiting result was selected to investigate the effect of the oxygen concentration on IL inhibition. The results revealed that the influence of IL on the mass loss process of the three metamorphic grades of coal varied considerably. High inhibition was observed in lignite. However, the IL promoted the mass loss process in 1/3 coking coal and anthracite. The IL delayed the ignition temperature of lignite by 42 °C, whereas those of 1/3 coking coal and anthracite were advanced by 10 and 8 °C, respectively. Furthermore, the initial exothermic temperature of the three treated coal samples was higher than those of the raw coal samples. Compared with the raw coal samples, the heat released per gram of lignite, 1/3 coking coal, and anthracite was reduced by 1142, 353, and 226 J, respectively. The results indicated that the IL had a prominent inhibiting effect on the exothermic properties of the three coal samples, and the inhibiting effect decreased with an increase in the metamorphic grade of coal. Moreover, the oxygen concentration did not alter the inhibition properties of the IL on the SCC. However, the inhibiting effect weakened as the oxygen concentration decreased.

In order to investigate the spontaneous combustion characteristics of weathered coal, gas generation and thermal behavior of weathered and fresh coal were analyzed. A self-made high-temperature-programmed experimental system was applied to simulate the spontaneous combustion of weathered and fresh coal. The characteristic parameters during oxidation were between 30 and 650 °C. The growth rate obtained through the analysis of an indicator gas was adopted to calculate the characteristic temperatures of high-temperature spontaneous combustion of coal. A C80 Calvet calorimeter was used to capture the thermal behavior during oxidation. At a high temperature and low oxygen concentration, weathered coal continued oxidizing and releasing thermal energy to sustain oxidation. The concentration of gases produced through high-temperature oxidation was lower for weathered coal than for fresh coal. The exothermic onset temperature of weathered coal was 43 °C, which was lower than the exothermic onset temperature of fresh coal. A salient difference was observed in the thermal energy release between weathered coal and fresh coal at different oxidation stages. From the critical temperature to crack temperature, the percentage of thermal energy release of weathered coal was much lower than that of fresh coal.

The accurate prediction of coal temperature plays a vital role in preventing and controlling the spontaneous combustion of coal in coal mines. In this study, a long-term in-situ observation experiment was conducted in a fully mechanized caving face of the Dafosi Coal Mine, where the in-situ data of gases and temperature were obtained. Two machine learning approaches, random forest (RF) and support vector machine (SVM) were introduced and compared for predicting coal spontaneous combustion based on the in-situ monitoring data. The particle swarm optimization (PSO) was employed to optimize the RF and SVM by finding their optimal hyper-parameters. Principal component analysis (PCA) was used to transform the original input data into a new dataset of uncorrelated variables, reducing dimension for input variables. The results indicated that regardless of whether the models with or without PCA, the RF model was more robust than the SVM model and less affected by its own parameters, while the SVM model was highly sensitive to its parameters. Although the PSO could find the optimal hyper-parameters of the RF model, the RF model with default parameters could also accurately predict coal spontaneous combustion and possess satisfactory generalization. However, the predictive performance of the SVM model was dramatically improved in predicting after the PSO optimization. Moreover, the models with PCA also showed the above characteristics. These results suggest that both the RF and SVM methods can be used to predict coal spontaneous combustion, while the RF method can obtain accurate predictions without special parameter settings, it is more suitable for practical applications and can potentially be further employed as a reliable method for the determination of complicated relationships.

This study examined the combustion characteristics and kinetics of coal samples treated with imidazole-based ionic liquids (ILs), namely, [Emim][BF4], [Bmim][BF4], [Bmim][NO3], and [Bmim][I], under oxidation. The oxidation of the coal samples was investigated using thermogravimetry (TG) at heating rates of 4.0, 6.0, 8.0, and 10.0 °C·min−1. The results for the IL-treated samples revealed that the composite index S (representing the ignition, combustion, and burnout properties) decreased and Hf (representing the rate and intensity of the combustion process) increased with high correlation coefficients. The characteristic temperatures of the maximum oxidization mass gain (T2), ignition point (T3), maximum mass loss rate (T4), and burnout point (T5) increased by 13.1 ± 0.5, 9.2 ± 0.5, 21.5 ± 0.5, and 35.9 ± 0.5 °C, respectively. At T3 and the maximum mass loss rate, the release of CO and CO2 was further altered, suggesting that the C O functional groups were damaged or oxidized. The results of the Ozawa-Flynn-Wall kinetic equation used to determine the apparent activation energy (Ea) of coal samples revealed that the Ea of the treated samples increased. The reaction rate constant characterizes the effect of Ea and pre-exponential factors (A), and the results showed that ILs can weaken the reaction process at low temperatures (

As to the continuous consumption of limited high-rank coal resources, low-rank bituminous coal is gradually grabbing more attention to the utilization for power resources and industrial production. However, the high risk of spontaneous combustion of low-rank coal has gradually become one of the most critical hazards worldwide during coal mining, storage, and applications. Thermogravimetry coupled with Fourier transform infrared spectrometry using a nonisothermal program method was employed to investigate the oxidized features of two low-rank coals from Jurassic strata. According to initial, first- and second-derivative thermogravimetric curves, an improved quantitative method for determining the eight characteristic temperatures of the coal oxidation process was proposed. The indexes and implications for the thermal hazard of spontaneous coal combustion during stages I–IV, based on the characteristic temperatures, were analyzed. By examining the functional groups, microcharacterization at each characteristic temperature of the coal was obtained. Three kinetic methods were used to calculate the apparent activation energy ( $$E_{\text{a}}$$ ). The evolution of $$E_{\text{a}}$$ was stage III > stage IV > stage II > stage I. The results demonstrated that the integral mechanism in the four stages described a second-order chemical reaction. Moreover, the pre-exponential factor and $$E_{\text{a}}$$ were positively correlated.

The spontaneous combustion of coal is characterized by high-temperature oxidation. This study used a self-made programmed experimental system to maintain temperature parameters at specified levels to simulate the combustion properties of coal. The oxygen concentration was determined to be inversely proportional to indicator gas concentrations. Five characteristic temperatures were achieved: critical temperature (97.45 ± 7.15 °C), crack temperature (149.28 ± 8.32 °C), active temperature (206.95 ± 15.05 °C), speedup temperature (263.45 ± 6.35 °C), and ignition temperature (390.85 ± 27.05 °C). Thermal characteristics were analyzed by dividing the oxidation into the following temperature stages: the critical temperature stage, crack–active–speedup temperature stage, speedup-ignition temperature stage, and combustion stage. Furthermore, the differential and integral kinetic methods were used to compute the apparent activation energy in the four aforementioned stages. The results indicated that the apparent activation energies decreased through the first three stages and then increased in the fourth stage. Therefore, the crack–active–speedup temperature stage was determined to be potentially dangerous during oxidation because gases increased rapidly at this stage; such gases included CO, which is particularly harmful to human health. The thermal energy release also increased gradually at this stage.

Biofuels produced from biomass are clean, renewable, and eco-friendly alternatives to the conventional fossil fuels in the transportation sector. However, the presence of high-water content, low pH, high viscosity, and oxygenates limits the direct use of biofuel in vehicular engines. The in situ and ex situ catalytic as well as noncatalytic hydrothermal upgradation of bio-oil (converting into hydrocarbons or less oxygenated compounds) are very promising. The recent advances in thermochemical conversion processes, improved strategies in feedstock pretreatment, and optimized use of both homogeneous and heterogeneous catalysts have enhanced the fuel properties of biofuels. The available literature was reviewed extensively to perceive the pros and cons in the selection of the suitable upgrading process to produce the bio-oil based on the end use. In this chapter, the technical developments toward improving the bio-oil properties, both in quality and quantity, the influence of process parameters, reactor configurations, and their primal source were discussed in detail. By comparing the various conversion and upgrading technologies, hydrodeoxygenation is considered as the prominent alternative and the latest technology in contrast to gasification and liquefaction. However, the complexities of the hydrodeoxygenation mechanism, optimal processing conditions, and the choice of the catalysts are yet to be understood. Furthermore, the chapter points out the main barriers for the commercialization of bio-oil upgrading technologies for the future.

Coal spontaneous combustion (CSC) has a devastating effect on the environment and human health. CSC primarily involves oxygen-lean oxidation and combustion states. In this study, to investigate the evolution of the coal microstructure during CSC in an oxygen-lean atmosphere, coal for oxygen-lean combustion was obtained and combusted at characteristic temperatures by using an independently developed electric tube furnace. Through Fourier-transform infrared spectroscopy, the relative contents of the active functional group of the initial-state oxidation coal were explored, and the main active functional groups, namely aromatic hydrocarbon, the oxygen functional group, aliphatic hydrocarbon, and the hydroxyl group, with the characteristic temperature, were determined. The sensitivities of different active functional groups to oxygen concentrations were analysed. In practice, a 10 vol% oxygen concentration was the key factor, inhibiting and promoting various active functional groups and exhibiting distinct dominance at various stages. Finally, the oxygen concentrations affected the gas concentration release characteristics, thereby determining the correlation degree of the key group and the oxygen concentration, as well as verifying the oxygen concentration sensitivity of the microstructure. The groups highly correlated with CSC characteristic parameters were mainly –CH2 and –CH3. The research results suggested remarkable explanatory potential to further elucidate the evolution of microstructures in oxygen-lean CSC.

Thermal extraction from a coal fire by using a two-phase closed thermosyphon (TPCT) is a clean and sustainable approach to govern coal spontaneous combustion (CSC). However, investigations into the elimination of coupling effects and the optimal design of the primary operational variables of TPCTs for effective prevention and control of coal fires are lacking. Through orthogonal experiments, this study examined the influence of the major factors of nanoliquid as liquid working medium, filling percentage, and aspect ratio on TPCT heat transfer. Analysis of variance (ANOVA) was performed to obtain the optimal combination of variables. The results indicated that when the coal temperature was 100 °C, the highest heat transfer performance of TPCTs among all experimental test cases was achieved which utilising CuO–H2O as the liquid working fluid, a 25% filling percentage, and an aspect ratio of 15. The optimal combination of variables obtained using ANOVA constituted a CuO–H2O liquid working medium, a filling percentage of 15%, and an aspect ratio of 15. Subsequent numerical predictions indicated a 74.9% increase in the heat transfer performance of TPCT with the aforementioned combination of ANOVA-based variables compared with the experimental combinations.

The past two decades have seen a rise in university laboratory accidents in China. Although there is a growing awareness due to higher reporting and media coverage, the evaluation and understanding of common hazards and deficiencies in university laboratories remains to be addressed. Aiming to enhance safety in laboratory-related activities, this study analyzed the current status and challenges of university laboratory safety in China and presented future directions to reduce accidents using engineering and administrative controls. A descriptive statistical analysis of 110 publicly reported university laboratory accidents in mainland China since 2000 was performed to investigate the proximate causes of the accidents, and further, to identify potential deficiencies existing in the current safety management of laboratories. It was found that human factors were the most contributing cause and the training element was a vulnerable competency in laboratory safety management. Based on the results, a comparative analysis between the underlying reasons for the poor safety situation and the efforts that have been made has brought the challenges and possible solutions for safety improvements in university laboratories. By suggesting top-down and bottom-up approaches, the present study provides valuable insights and serves as a reference for universities and relevant authorities to enhance safety in university laboratories.

In order to explore the changes during the coal cooling process in a closed fire zone (CFZ), the oxidation characteristics of the heating and cooling processes were thoroughly examined and compared. The heating and cooling processes under various oxygen concentrations of three coals were simulated with temperature-programmed experiment and coal spontaneous combustion experiment. Furthermore, the hottest spot, oxygen consumption, index gases, and oxidation kinetics between the gaseous production rate (f) and coal temperature (T), air supply (Q), oxygen concentration ( C O 2 ), and apparent activation energy ( E a ) were analysed. The results revealed that the movements of the hottest spots did not overlap in the heating and cooling processes. Moreover, the oxygen consumption during the cooling process was higher than that during the heating process, and a lower oxygen concentration was associated with higher oxygen consumption, a condition in which coal strongly captured oxygen actively. The index gases during the heating and cooling processes notably differed, which were related to coal types, and during the forced heating process, the CO2/CO ratios of 1/3 coking coal and anthracite were higher than that of the forced cooling process, even under the oxygen-lean conditions, the CH4/C2H4 ratio of lignite during the forced cooling process was also notable. Moreover, the results in the cooling process of the temperature-programmed experiment in the carrier gases with 7% and 3% O2 were consistent with that of the spontaneous combustion experiment. Finally, the apparent activation energy at different stages of the heating and cooling processes was calculated, exhibiting inconformity, and apparent activation energy is lower in the cooling process, which is related to its higher oxygen consumption, and showing stronger oxidisability in the cooling process. In addition, through the results of coal oxidation kinetics, it is found that coal temperature affected the magnitude of apparent activation energy, the oxygen concentration impacted the oxidation activity of coal. These research results are valuable for informing the process of fire extinguishment and guiding the fire area unsealing in CFZ.

To smoothly deliver crude oil, the crude oil piping system adopted by petrochemical plants must be maintained at a high temperature. This study investigated a fire accident by collecting fire debris and related combustibles as experimental samples and employed calorimetric approaches in fire testing the spontaneous combustion of crude oil sludge. Moreover, thermal analysis experiments were conducted. The results demonstrated that although the clean insulation material was flame resistant, after absorbing a large amount of crude oil sludge, the material underwent an exothermic reaction of enthalpy 247.39 J/g with a weight loss of 33.98% when its temperature reached approximately 170 °C. The heated temperature of the bulk bags widely used in the industry is approximately 204 °C, which has an exothermic reaction of enthalpy 98.60 J/g; at approximately 399 °C, an exothermic reaction of enthalpy 117.74 J/g resulting in a weight loss greater than 96.23% occurs. The results from each experiment conducted in this study are expected to serve as a reference for preventive measures against thermal hazard accidents involving insulation materials.

Thermal analysis was used to investigate the oxidation and heat-release characteristics of four coal samples from the Huainan mining area in China. Temperature and the evolution of heat and gaseous...

Thermal properties of coal are crucial in the heat-transfer process of its spontaneous combustion. Thermophysical properties of four metamorphic-grade coal samples were investigated in air using a laser-flash apparatus. Their crystallinities were analyzed by X-ray diffractometry. The results indicated that the trend in thermal diffusivity was opposite to that of crystallinity. As the temperature increased, thermal diffusivity first decreased and then increased; specific heat first increased and then decreased. With the exception of the meager lean coal sample, the trend of thermal conductivity as a function of temperature agreed with that of specific heat. As the metamorphic grade of the samples increased, the thermal diffusivity minimum and specific heat maximum shifted toward higher temperatures; in contrast, the minimum thermal conductivity shifted toward lower temperatures. From these trends, it was possible to recognize different temperature ranges according to how different properties (thermal conductivity, thermal diffusivity, specific heat, and metamorphism grade) influenced each other.

Three commercial inhibitors were investigated for their suitability in preventing the spontaneous combustion of noncaking coal (NCC) and gas coal (GC), two coals of low metamorphic grades. Simultaneous thermal analysis, Fourier transform infrared spectroscopy, and kinetic analysis demonstrated that Zn/Mg/Al-CO3-layered double hydroxides (LDHs) and diammonum phosphate ([NH4]2HPO4) both exhibited substantial inhibiting effects. Therefore, Zn/Mg/Al-CO3-LDHs and (NH4)2HPO4 may be used for the prevention of spontaneous coal combustion. The reaction mechanisms and kinetic models for NCC and GC mixed with inhibitors were also determined. Na3PO4 demonstrated poor inhibiting ability in NCC and GC and even promoted the combustion of GC. Therefore, Na3PO4 is not recommended as an inhibitor for NCC and GC. Finally, the results indicated that (NH4)2HPO4 and Zn/Mg/Al-CO3-LDHs can be used to decrease CO2 release, limiting the oxidation reaction of coal and attenuating greenhouse gas emissions. This study can serve as a reference for efforts to prevent spontaneous coal combustion and for the development of new inhibitors.