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To protect the environment and reduce the occurrence of coal mine fire, foam injection in goafs is an effective measure for preventing and extinguishing mine fires. The flow characteristics of foams injected into goafs have a significant impact on the prevention and extinguishment of such fires. To study the flow characteristics of foam injected into a goaf, we first independently constructed a set of experimental platforms for the visualization of goafs. Next, we performed physical experiments on foam injection using similarity theory. Flow characteristics were simulated under different foam concentrations, flow rates, and goaf porosities. The exponential function was found to provide a good fit to the trajectory of the foam's stacking edge in the goaf. According to the foam injection volume, the trend of the fitting equation parameter a could be divided into two stages. The first stage was the rapidly decreasing stage, and the second stage was the stable stage. It was inferred that the stacking height and diffusion radius of the foam under different conditions were related to the speed of liquid film drainage. The results of this study can provide a valuable reference for the use of fire prevention and extinguishment technology in the goaf.

To prevent coal spontaneous combustion and store CO

Goaf filling is an effective method of preventing goaf disasters in mines. If the filling material can mineralize and absorb a large amount of CO

Microcapsules containing isophorone diisocyanate were fabricated in oil-in-water emulsion. The emulsification effect of different emulsifiers during the capsule synthesis was systematically investigated by optical microscope. Three kinds of shell materials were discussed to obtain the high core content, smooth-surfaced, and robust capsule by scanning electronic microscope and Fourier transform infrared spectroscopy. Self-healing performance of corresponding self-healing epoxy composites was fully evaluated by accelerated corrosion test and mechanical test. The results demonstrated that high core content and smooth-surfaced capsules with dense composite shell could be synthesized in polyvinyl alcohol emulsion, and the core content of the optimized capsules was determined as 71.3–84.6 wt% at the capsule size from 35 µm to 154 µm. In addition, the optimized capsules had good processing properties and the corresponding self-healing epoxy composites exhibited excellent core release and self-healing performance.

In order to solve the environmental problems caused by greenhouse gas emissions, cellulosenanofiber (CNF)/polyvinyl alcohol (PVA)/graphene oxide (GO) aerogel was obtained by step-by-step heating, tert-butanol replacement, freeze-drying, and high-temperature activation in this paper. The micromorphology, specific surface area, pore size distribution, and thermal stability of the prepared aerogels were analyzed by scanning electron microscopy, automatic surface area and porosity analysis, and thermo-gravimetric analysis. The interaction state and adsorption mechanism of CO

Smoldering of coal is a considerable source of danger in coal mines because it can lead to a gas explosion, which can cause heavy casualties. This work investigated the apparent smoldering reaction...

Alternating current field measurement (ACFM) and eddy current thermography are two non-destructive testing (NDT) methods widely used in industries. In this study, a combined NDT method based on the...

This study focuses on the mechanism of gas (such as CO and CO2) generation during low-temperature oxidation of coal to provide a better understanding of the progressive phases of coal spontaneous c...

Supplemental Material, Supporting_information_(2) for Optimized synthesis of isocyanate microcapsules for self-healing application in epoxy composites by Yong Sun, Shugang Wang, Xiaosu Dong, Yuntao Liang, Wei Lu, Zhenglong He and Guansheng Qi in High Performance Polymers

In order to solve the environmental problems caused by greenhouse gas emissions, cellulosenanofiber (CNF)/polyvinyl alcohol (PVA)/graphene oxide (GO) aerogel was obtained by step-by-step heating, tert-butanol replacement, freeze-drying, and high-temperature activation in this paper. The micromorphology, specific surface area, pore size distribution, and thermal stability of the prepared aerogels were analyzed by scanning electron microscopy, automatic surface area and porosity analysis, and thermo-gravimetric analysis. The interaction state and adsorption mechanism of CO2 and aerogel physical adsorption were described by Materials Studio simulation. The results showed that the adsorption process conformed to the Langmuir adsorption isotherm. After carbonization, the thermal stability of the aerogel was good (mass loss rate

Coal spontaneous combustion results from a complex reaction between coal and oxygen. Previous studies on coal oxidation spontaneous combustion process provided guidance for fire prevention and control. In this work, we present a novel electromagnetic radiation (EMR) method to detect spontaneous combustion of coal. We established a multi-index experimental system for estimating various factors during coal oxidation (heating) and combustion and analyzed the characteristic temperature, index gases, and EMR signals. With the increase of temperature, the central temperature of coal varies significantly with the temperature around the coal oxidation heating device. Besides, we simultaneously tested the EMR signals generated during coal oxidation and combustion. EMR signals showed a positive correlation with temperature changes (i.e., EMR signal intensity increases with the increase in temperature and vice versa). The change trend of EMR signals with the CO is notable, and there is a good correspondence between the EMR signals and the change rule of CO gas. With the increase of temperature, the dielectric properties of coal change quickly, resulting in the occurrence of thermal deformation and rupture in the coal body, which produces significant EMR signals. The research results are of great significance for applying the EMR technique to directly detect hidden fire hazards in coal mines.

The CO2 storage technology of abandoned coal mines has problems such as high gas separation costs and incomplete CO2 separation in the gas capture stage, which hinders the development of abandoned coal mines for CO2 storage. Regarding the issue above, a new type of carbon dioxide adsorption material has been prepared. Cellulose whiskers/silica composite aerogels were synthesized from skim cotton using tetraethyl orthosilicate (TEOs) and alkaline silica solution as silica precursors through a sol-gel process. The obtained aerogel has a rich porous structure with a specific surface area in the range of 34.7–170.1 m2/g, pore volume in the range of 0.06–1.52 cm3/g, and average pore size in the range of 4.5–11.9 nm. The sample CSA-TEPA-70% showed excellent adsorption performance, with a maximum adsorption capacity of 2.25 mmol/g. The Avrami fractional-order kinetic model can fit the CO2 adsorption process of the adsorbent well. This adsorbent has broad prospects in the CO2 capture process.

Aiming at solving the problem of coal spontaneous combustion during coal mining, a new type of antioxidant gel foam for coal mine fire prevention and control was proposed. The gel was prepared by introducing procyanidins into the gel system (sodium silicate / coagulant / bentonite). By testing the gelling time and water retention rate of the antioxidant gel, the effects of different concentrations of coagulant and crosslinker on the performance of antioxidant gel were analyzed. The results of thermogravimetric analysis disclose that the gel corresponds to just about 13% weight loss, and procyanidins in the gel inhibits coal oxidation, thus delaying the decomposition process of coal. The results of inhibition experiment show that the antioxidant gel foam can effectively slow down the oxidation-induced heat release of coal and suppress the increase in coal temperature. Besides, it effectively inhibits the release of CO during coal spontaneous combustion, the inhibition rate reaching up to 68.7%. The results of fire extinguishing experiment display that the gel can well cover the surface of combusting coal to rapidly reduce the temperature at coal center within 900 s and lower the temperature from 727 °C to room temperature within 1850 s, achieving stable fire extinguishing without reburning.

Fire prevention and extinguishing and CO2 sequestration in coal mine gob require continuous transportation of liquid CO2 in pipelines with large height difference (from ground to underground). However, the temperature and pressure variation of liquid CO2 in pipelines with large height difference is still unclear, which hinders the design of a liquid CO2 pipeline transportation system. The influence of pipe diameter and inlet parameters (temperature and pressure) on the variation of temperature and pressure of liquid CO2 along the 1000 m vertical pipeline was studied in this paper. The study found that for each pipeline diameter considered there existed a range of flowrates where safe flow conditions could be ensured, at which no phase transition occurs throughout the length of the pipeline. When the transporting flow is larger than the maximum limit flow, phase transition occurs dramatically, which will lead to a sudden drop in temperature and pressure. When the transporting flow rate is lower than the minimum limit flow rate, phase transition of CO2 occurs slowly along the pipeline. According to the requirement of underground fire prevention and extinguishing for transporting flow rate and the economic cost of the pipeline system, the optimum diameter is 32 mm, and the corresponding safe transporting flow range is 507&ndash, 13,826 kg/h. In addition, when the inlet pressure is constant, if the inlet temperature is too high, phase transition of CO2 occurs dramatically at the entrance. For a 1000 m vertical pipe with diameter of 32 mm, when the inlet pressure is 14 bar, 16 bar, 18 bar, 20 bar, 22 bar, 24 bar, the corresponding maximum allowable inlet temperatures are &minus, 30 &deg, C, &minus, 26 &deg, 23 &deg, 19 &deg, 16 &deg, C and &minus, 13 &deg, C, respectively. This research has significant guidance for safety transportation scheme of liquid CO2 from coal mine surface to underground.

In order to gain a knowledge of the heat emitted from a variety of sources at the blind heading of an underground gold mine, the present study conducts an in situ measurement study in a blind heading within the load haul dumps (LHDs) that are operating. The measurements can provide a reliable data basis for the setting of numerical simulations. The results demonstrate that the distances between the forcing outlet and the mining face (denoted as Zm), as well as the heat generation from LHDs (denoted as QL), has brought significant impacts on the airflow velocity, relative humidity, and temperature distributions in the blind heading. Setting Zm to 5 m could achieve a relative optimal cooling performance, also indicating that when the LHD is fully operating in the mining face, employing the pure forcing system has a limited effect on the temperature decrease of the blind heading. According to the numerical simulations, a better cooling performance can be achieved based on the near-forcing-far-exhausting (NFFE) ventilation system.

In view of the accidents such as rock mass breakage, roof fall and coal slide in coal mines, polyurethane/mesoscopic fly ash (PU/MFA) reinforcement materials were produced from polymethylene polyphenylene isocyanate (PAPI), the polyether polyol, flame retardant, and MFA using stannous octanate as a catalyst. 3-Glycidoxypropyltrimethoxysilane (GPTMS) was grafted on MFA surface, aiming to improve the mechanical properties of PU/MFA composites. The analyses of infrared spectroscopy and compression resistance reveal that the GPTMS can be successfully attached to the surface of MFA, and the optimum modification dosage of GPTMS to MFA is 2.5 wt % (weight percent). On this basis, the effect of GPTMS on the mechanical properties of PU/MFA reinforcement materials during the curing process was systematically investigated through a compression test, a fracture toughness test, a three-point bending test, a bond property test, and a dynamic mechanics analysis. The results show that the compression property, fracture toughness, maximum flexural strength, and bond strength of PU/MFA composites increase by 21.6%, 10.1%, 8.8%, and 19.3%, respectively, compared with the values before the modification. Furthermore, the analyses of scanning electron microscope and dynamic mechanics suggest that the coupling agent GPTMS can successfully improve the mechanical properties of PU/MFA composites because it eliminates the stress concentration and exerts a positive effect on the crosslink density and hardness of PU/MFA composites.

In the process of coal mining, coal spontaneous combustion in the gob area poses serious threats to the safety of mine production. Besides, coal combustion also produces a large amount of greenhouse gas CO2, which triggers a series of ecological environment problems. In order to solve these two problems, the idea of mineralizing CO2 with the alkaline industrial waste calcium carbide slag and then sending the foams to the gob area for coal spontaneous combustion prevention was proposed in this study. First, the effects of calcium carbide slag foaming under the action of different types of foaming agents, including sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), polyoxyethylene fatty alcohol sodium sulfate (AES), and octyl decyl glucoside (APG0810), were tested and analyzed. Furthermore, the effects of water glass (WG), sodium alginate (SA), polyvinyl alcohol 1799 (PVA), cement, and silica micro-powder on the foam stability were analyzed by investigating the stability coefficient and drainage volume of calcium carbide slag foam. On this basis, the configuration scheme of calcium carbide slag foam with high efficiency and good stability was determined. The experimental results on CO2 mineralization and coal spontaneous combustion inhibition reveal that the prepared calcium carbide slag foam can rapidly absorb CO2. Moreover, after calcium carbide slag foam treatment, the spontaneous combustion tendency of the coal sample is significantly reduced.

Coal can maintain smoldering combustion for a long time in the gob (mined-out) area which is a serious threat to the safety mining of a coal mine. However, few literatures can be obtained to well understand the smoldering phenomena of coal. To obtain the coal smoldering characteristics, vertical forward and reverse smoldering tests under different air flow rate were performed, and the smoldering combustion process, speed, and temperature were analyzed. It is found that although the combustion process of forward and reverse smoldering is significantly different, their smoldering speeds are the same and both increase monotonically with air flow rate as the higher the air flow rate is, the greater the oxygen consumption rate can reach. Even when the air flow rate is 0.074 m/min in that the wind speed belongs to the suffocation zone of the gob, the coal can still undergo smoldering until complete combustion. This indicates that the smoldering fire cannot be effectively extinguished by only accelerating the stoping speed of the working face to create fire in the suffocation zone during the mining process. And for a sealed fire zone, it is also difficult for the smoldering fire to be completely extinguished as the fire zone cannot be absolutely sealed. Meanwhile, the risk of reverse smoldering is greater than forward smoldering due to its larger smoldering temperature.

Organic chemical reactions cause the temperature rising during coal oxidation; however, because of the complex structure of coal, it is difficult to analyze and characterize the reactions involved in coal low-temperature oxidation. To date, a main reaction pathway describing the heating progress during coal oxidation has not been proposed. Here, a series of cyclic chain reactions is presented to describe the oxidation mechanism during coal spontaneous combustion using quantum chemistry calculations. Main active sites and their molecular models were built. Three interactive modes of active orbitals and detailed reaction sequences of coal oxidation are proposed. The structural parameters and thermodynamic data were calculated and the orders of reactions for transformations between functional groups were identified based on their activation energies. The reaction pathway was constructed based on functional transformation relationships and the order of reactions. The results show that main reactions occurring during coal oxidation can be defined as the reactions of oxygen and hydroxide free radicals reacting with coal active sites. Methyne and carbon free radicals reacting with oxygen is the initial reaction during coal oxidation. The decomposition of peroxides linking the reaction pathway form cyclic chain. Hydroxyl and aliphatic hydrocarbon radicals as key of chain reactions consumes coal active sites and oxygen continuously. Aliphatic hydrocarbons appear to contribute more to heat release during coal oxidation due to greater heat release and lower activation energy of their reactions. Limited spontaneous reactions maintain constant apparent activation energy for the oxidation until the chain reactions are generated; the apparent activation energy then increases. Low-ranking coals have higher apparent activation energies during oxidation due to more oxygen-containing groups and side chains contain more reactions with higher activation energy. Results from this study can improve understanding of mechanism of coal oxidation and provide a guide to forecasting and preventing spontaneous combustion of coal in underground coal mines or coal stockpiles.

Disasters from the spontaneous combustion of coal seriously affect safe coal mine production. Halogen salt inhibitors have been widely used as materials specifically to prevent and control the spontaneous combustion of coal. However, at present, such inhibitors are mainly used at room temperature, resulting in problems such as poor inhibitory effects. To solve this problem, the effect of increasing preinhibition temperature on the inhibitory effect of the spontaneous combustion of coal was studied when using an MgCl2 solution as the inhibitor. The raw coal was immersed in the MgCl2 solution with a mass concentration of 20% at 30 °C, 50 °C, 70 °C and 90 °C for different periods of time to prepare the inhibited coal samples. Temperature-programmed tests and infrared spectral experiments were performed to study the macroscopic and microscopic parameters of different inhibited coal samples during spontaneous combustion. It was found that with an increase in the preinhibition temperature, the content of active groups (aliphatic hydrocarbon side chains (–CH3 and –CH2) and oxygen-containing groups (–C O, –COOH and –C–O)) on the coal surface significantly decreased, the activation energy required for the complexation of coal and oxygen increased, the oxygen consumption rate and heat production rate during the spontaneous combustion of coal obviously declined, and the inhibition rate significantly increased. These results indicated that increasing the preinhibition temperature could significantly improve the inhibitory effect. In addition, the results showed that prolonging the preinhibition time and increasing the preinhibition temperature synergistically enhanced the inhibitory effect.

Since the CO2/CO ratio was found to be unaffected by the ventilation flow rate, it is an excellent tool to evaluate the state of coal spontaneous combustion. However, the existing studies generally regard coal-oxygen reaction as a total package reaction, which leads to the mutual interference of CO2/CO produced by pure oxidation, pyrolysis and physical desorption. Besides, the reasons for the change of CO2/CO ratio are not clear. Therefore, a method was designed to obtain the gas production characteristics of pure oxidation pathway. At the same time, the relationship between the change of active groups and CO2/CO during pure oxidation was investigated by means of in-situ FTIR and model compounds. The experimental results show that at lower temperatures, the CO2 produced in coal mainly comes from physical desorption and pyrolysis, which will interfere with the change of CO2/CO. The new method can eliminate the influences of them. It is also concluded that the ratio of CO2/CO produced by pure oxidation pathway exhibits obvious segmentation. With the increase of temperature, it can be divided into four stages, gradual participation of different active groups in coal is the main reason for the segmentation and determines the initial temperature range in each stage. The CO2/CO ratio and equilibrium value are mainly affected by the hydroxyl content in coal. The accuracy of coal spontaneous combustion can be improved based on the segmentation of CO2/CO production by pure oxidation.

The longwall gob (mined-out) area is one of the main places that are prone to coal spontaneous combustion and most of the residual coal in it is in oxygen-depleted air as it is a semi-enclosed space. A DSC (Differential scanning calorimetry) test system was designed to accurately test the heat generation of coal oxidation in different oxygen concentration atmosphere, based on which the kinetics parameters (activation energy and pre-exponential factor) of coal low-temperature oxidation in oxygen-depleted air were solved out. The results show that the kinetics parameters present obvious stage features and the lower the oxygen concentration is, the smaller is the difference of the kinetics parameters that in different oxidation stages. When the oxygen concentration is lower than 5% and 3% for jet coal and meagre coal respectively, the kinetics parameters of slow oxidation start to be greater than that of rapid oxidation. Both in the slow oxidation and rapid oxidation stage, with the decrease of oxygen concentration, kinetics parameters present significant decline on the whole while in different oxygen concentration range, the decline rate is different. It's concluded that when assessing the residual coal's self-heating risk, we need to use the corresponding kinetics parameters of coal oxidation in the oxygen concentration of the location where the residual coal is and the safety factor will be greater to only use the kinetics parameters of coal oxidation in slow oxidation stage. This study is of great significance for the assessment and control of the self-heating risk of coal that in different oxygen concentration atmospheres of the longwall gob areas.

To realize the automatic quantitative control of liquid absorption, a jet pump working under operating limits is proposed and investigated. Experimental results show that the absorption amount keeps constant and is independent of the outlet pressure at the jet pump operating limits. There is an obvious interface wave in the jet pump, and the reason why the upstream pressures have not changed is because the interface wave has not arrived there. The critical pressure ratio is 0.28 at the flow ratio of 0.5%, while it is only 0.2 at the flow ratio of 19.5%. Hence, the low flow ratio produces a high critical pressure ratio, making the jet pump have a much stronger resistibility for dealing with the downstream pressure fluctuation. In addition, the jet pump has a larger bubble region length at a lower flow ratio under operating limits. The bubble diameter decreases from 0.42 mm to 0.06 mm with the flow ratio increasing at the throat cavity, while it keeps unchanged at the suction cavity, which creates a good condition for stable liquid absorption. Based on the above contributions, it is believed that the study will lay an important foundation for the large-scale application of jet pump used for automatic quantitative control.

Coal spontaneous combustion is one of the major natural disasters faced in coal mines. The accurate prediction of the thermal risk of coal is of great importance. However, there isn't a widely accepted approach to get the oxidation process of coal that under adiabatic condition or in a specific environment under mine at present. To demonstrate whether the advanced kinetics simulation method could be employed to obtain the accurate oxidation process of coal for determining the coal's thermal risk in the mine design phase and mining phase, DSC experiments were conducted by C80 micro-calorimeter to get the heat behavior of coal, based on which the kinetic parameters can be solved and the oxidation process of coal can be predicted. The results showed that the kinetics based simulation method was successfully used to predict the adiabatic temperature rise process of coal for risk prediction. The deviation between the predicted curve and tested curve that obtained by adiabatic test is small enough to be accepted. Kinetics based simulation method is a promising candidate, instead of adiabatic test, to assess the propensity of coal to spontaneous combustion, which can play an important role in the design phase of the mine and mining area. Moreover, through establishing the heat balance equation of residual coal and with the aid of kinetics based simulation method, the oxidation process of coal that in the suffocation zone of the gob was also accurately predicted. According to the index t 70 (the time required for coal to reach 70 °C) and v min (the lower limit of the advancing speed of the working face) obtained from the predicted curve, the thermal risk of coal was predicted to guide the further adjustment of the advancing speed of the working face, the amount of the injected mud and the determination that whether to add other fire prevention measures. Kinetics based simulation method, be of great practical importance in risk prediction of coal that in the gob, can be also used as a convenient tool to guide the safe production in the actual mining process.

The remarkable differences between the infrared spectra of oxygen adsorption and nitrogen desorption in coal have been experimentally and theoretically investigated. Density functional theory calculations were performed to better explain the mechanism of oxygen adsorption using six different molecular models of coal. In addition, the remarkable differences of infrared spectra between oxygen adsorption and nitrogen desorption was defined as the index V, which was used to classify the spontaneous combustion tendency of coal. The experimental data indicated that the spectra in the 4000–2000 cm−1 and 1250–1050 cm−1 regions exhibited significant changes. These results suggest that the mechanism of oxygen adsorption is the alteration and transfer of charge density around the activated sites, which leads to the observed changes of the infrared spectra. The V, which is related to the alteration of spectral intensity, is found to decrease with the increase of adiabatic oxidation time and the relative spon...

This study details an in situ Fourier transform infrared spectroscopy analytical system that was employed to follow chemical variations in the functional groups on coal surface during the oxidation process at low temperatures. In the reported in situ Fourier transform infrared spectroscopy system, a special chamber was used to contain the coal powders, and a gas inlet tube and a programmable heater were used to simulate different reaction atmospheres and temperatures. The comparisons between in situ and ex situ Fourier transform infrared spectroscopy spectra indicate that the in situ Fourier transform infrared spectroscopy data offer a more accurate reflection of changes in the functional groups. The real-time changes of aliphatic hydrocarbon groups and oxygen-containing groups in a lignite coal sample were analyzed from 30°C to 220°C using in situ Fourier transform infrared spectroscopy. The experimental results indicate that the chemical variations in the functional groups are affected by their...

The extinction coefficient differs for different functional groups making the quantitative analysis of their infrared spectra problematic. Although the coefficients of some functional groups have been researched previously, they are inaccurate because of deviations in techniques used and linear fitting. The distribution and structural characteristics of functional groups from coal infrared spectra is therefore inaccurate. In this study, quantum chemistry methods are used for the quantification of coal infrared spectra based on the Beer–Lambert law. The effect of the extinction coefficients of different functional groups is eliminated. The experimental infrared intensities, unit absorption intensities and their ratios are obtained to calculate the percentage composition of coal functional groups and molecular structure parameters. Accurate distribution and structural characteristics of coal functional groups are obtained. A linear relationship between the distribution of some functional groups and structural parameters is obtained. Multiple structural parameters are used to determine the grade and maturity of coal samples. The ethylene in coal oxidation experiments below 200 °C is consistent with the hydrocarbon-generating potential parameters. These results will improve the accuracy of the quantitative analysis of infrared spectra for determining coal structural features and provide an index for the utilization and prevention of the spontaneous combustion of coal.

Ultrasonic receiving wave can reflect physical properties and damage degree of coal samples. Therefore, it is of great significance to deeply study the parameters of ultrasonic. In this paper, time-domain characteristics of receiving wave are analyzed systematically, which present good correlation with stress. The frequency spectrum of receiving wave is obtained using Fast Fourier Transform (FFT), and peak frequency and centroid frequency are calculated. During the entire loading process, peak frequency fluctuates around 110[Formula: see text]kHz, but corresponding centroid frequency decreases obviously at the end stage of loading. According to multifractal theory, the multifractal spectrum of wavelet packet energy characteristics is calculated. The results show that wavelet packet energy distribution has obvious multifractal characteristics, and multifractal parameter [Formula: see text] presents downward trend before coal samples buckling failure. Based on damage process of the coal samples, the reason of change in [Formula: see text] value is related to damage degree of coal samples. This research is of great significance for understanding the deformation and failure process of coal samples using ultrasonic technology.

A rapid, simple method was developed for the determination of R70 self-heating rate of coal. The coal samples were tested under adiabatic and programmable temperature conditions, separately. It indicates that it is a linear relationship between the differential value of oxygen concentration at 70 °C under a programmable heating condition ( Δ C O 2 , 70 ) and the adiabatic R70 self-heating rate. This linear relationship can be described by a fitted trendline equation R 70 = 0.68504 Δ C O 2 , 70 + 0.12098 . So the R70 can be determined by testing the value of Δ C O 2 , 70 . For most coals, the testing processes of Δ C O 2 , 70 need a time less than 1.5 h. A new evaluation method for the propensity of coal to spontaneous combustion was also proposed from previous R70 method. Based on the value of Δ C O 2 , 70 , a coal with a Δ C O 2 , 70 value below 0.55% is considered to be low risk, 0.55–1% medium risk, higher than 1% high risk. The study will be helpful for more widely and convenient use of R70 self-heating rate.

The distribution of functional groups in two different rank coal samples and their real-time changes during the oxygen-free reaction of coal were tested. An in situ FTIR system was designed to test...