Combustion Of Coal Gangue Research Articles

Study on the secondary oxidation behavior and microscopic characteristics of oxidized coal gangue.

Spontaneous combustion of coal gangue (CG) hills has caused varieties of secondary disasters that seriously endanger the ecological environment of the world. The emission law of index gases and their oxidation kinetics during the secondary oxidation process of CG with different ranks of oxidation were studied by using the temperature programmed device and online mass spectrometer (MS). Fourier transform infrared spectroscopy (FTIR) was used to reveal the changes of the CG internal active functional groups. The results showed that the energy required for the combustion of CG with low rank of pre-oxidation was significantly lower than that of the raw sample. However, as the oxidation rank increased, due to amounts of volatile components were released in the process of oxidation reaction, the CG in the combustion process of the emission of index gases and its oxygen consumption rate gradually reduced; the rapid oxidation stage shifted to the direction of the high temperature. In this study, the risk of spontaneous combustion of CG after oxidation at 80℃ under 3% oxygen concentration was the strongest. The results of this paper are of great guiding significance for exploring the spontaneous combustion characteristics of CG hills and their prevention by traditional covering method.

Experimental Investigation on Gallium and Germanium Migration in Coal Gangue Combustion

Gallium (Ga) and germanium (Ge) critical elements have a wide range of applications and market value. Extracting critical elements from coal gangue and combustion products can alleviate pressures on primary mining resources. Understanding the transformation behavior of Ga and Ge during coal gangue combustion processes is significant for resource utilization and environmental protection. Coal gangue from Xing’an League, Inner Mongolia, was chosen to explore how combustion temperatures (600 °C to 1000 °C) and particle sizes (50, 80, 10, 140, and 200 mesh) influence Ga and Ge migration during combustion. Techniques such as ICP-MS, XRD, XRF, SEM, TG-DSC, and sequential chemical extraction were employed to analyze the transformation of minerals and to quantify the contents and occurrence forms of Ga and Ge. Smaller gangue particle sizes were associated with higher concentrations of Ga and Ge. Approximately 99.19% of Ga and Ge in coal gangue were found in the residual, organic/sulfide-bound, and metal-oxide-bound modes. High temperatures promoted element volatilization and changed the reactions and interactions between elements and minerals. As combustion temperatures rose from 600 °C to 1000 °C, Ga and Ge contents in the products declined progressively. Under high temperatures, minerals like kaolinite, illite, and pyrite in gangue converted to silicate glass phases, mullite, and hematite. Minerals like kaolinite, calcite, and pyrite melted, leading to increased cohesion and agglomeration in the products. Over 90% of Ga and Ge in the combustion products existed in the residual, organic/sulfide-bound, and metal-oxide-bound forms. Moreover, Ga was enriched in combustion products, with its content exceeding critical extraction levels. The results may provide a useful reference for developing critical elements enrichment, extraction, and separation technologies from coal gangue.

Microscopic characteristics and sources of atmospheric dustfall in open-pit mining coal resource-based city in the arid desert area of Northwest China

Atmospheric dustfall is solid air pollutant, has a major impact on the environment and human health. The objective of this study was to investigate the microscopic characteristics and sources of atmospheric dustfall in open-pit mining coal resource-based city in the arid desert area of Northwest China. The characteristics of size and shape factors, variation of shape factors with size distribution, types of individual particles, and sources of atmospheric dustfall, which were collected in the open-pit mining area and surrounding areas, were analyzed by X-ray diffraction (XRD) and scanning electron microscopy coupled with an energy dispersive spectrometer (SEM–EDS) combined with graphical method and shape factors. The results showed that the atmospheric dustfall in all functional areas was dominated by coarse-grained particles. The shape of the atmospheric dustfall deviated from spherical shape, and with decreasing particle size, the difference in shape factors increased in each functional area. The EDS and XRD analyses indicated the presence of 13 types of particles. The sources were mainly local and included soil dust from each functional area; industrial dust, construction dust, biogenic impurities, fossil fuel combustion, wear products of motor vehicle parts, motor vehicle exhaust emissions, and emission and excreta from biological activities in each functional area except the desert area; emissions from a steel plant in the industrial area; coal-associated ore, coal dust, coal gangue emissions, and emissions from the spontaneous combustion of coal gangue in the open-pit mining area; secondary chemical crystallization products in the industrial area and the open-pit mining area; dust generated by vehicles abrading the surface of the off-mine coal road and in the open-pit mining area.

Study on controlling factors and developing a quantitative assessment model for spontaneous combustion hazard of coal gangue

Developing a quantitative hazard assessment model for spontaneous coal gangue combustion is imperative to ensuring the safety of coal mining operations. In this study, eight types of coal gangue from different coalfields were used to determine the controlling factors for spontaneous combustion. A variety of physical and chemical characterization methods were employed to investigate the physical and chemical characteristics of the samples. Based on the experimental results, six key parameters were identified, namely the aliphatic C–H components, pyrite sulfur content, physical oxygen absorption capacity, ash content, ignition point temperature, and activation energy for thermal decomposition. The results show that the spontaneous combustion hazard of coal gangue is positively correlated with the first three of these and is negatively correlated with the rest. Using the entropy-weight method combined with the analytic hierarchy process, appropriate weighting factors for each parameter were obtained and used to establish a quantitative assessment model for the spontaneous combustion hazard of coal gangue. This model is expected to enhance the current industrial best practices for the prevention and control of spontaneous coal gangue combustion.

Detection of Spontaneous Combustion Areas of Coal Gangue Dumps and Comprehensive Governance Technologies: A Case Study.

Spontaneous combustion of coal gangue dumps not only releases toxic and harmful gases, polluting the environment, but also leads to explosion accidents and casualties due to improper handling. This paper focuses on delineating the fire area, constructing a comprehensive fire prevention and extinguishing system, and restoring the ecological environment. Infrared thermal imaging was used to detect the shallow fire area, while intensive drilling was conducted to detect the deep fire area. The stability of the coal gangue dump was enhanced by perfusing three-phase foam for cooling and using a curing material to fill the cracks. Land reclamation was then performed to restore the ecological environment. The results indicate that spontaneous combustion of coal gangue dumps can trigger the spread of the fire area from the outside to the inside, gradually expanding due to the 'stack effect'. The sources of spontaneous combustion in gangue fire areas are mainly located 3-5 m below the flat surface, and the shallow and deep fire areas are interconnected, posing a significant danger. These research findings can serve as a reference for detecting fire areas in coal gangue dumps and controlling environmental pollution.

Study on adsorption-diffusion-seepage behavior of oxygen in coal gangue under the coupling of temperature and pressure

This research delves into the fundamental aspects of oxygen adsorption, diffusion, and seepage within gangue slits, aiming to avert the spontaneous combustion of coal gangue hills. Employing methodologies such as molecular dynamics (MD), Grand Canonical Monte Carlo simulations (GCMC), and the finite element simulation, the intricate behavior of O2 molecules within the coal gangue's slit structure is modeled under varying temperature and pressure conditions. The outcomes evince that augmented pressure facilitates oxygen adsorption while diminishing the diffusion coefficient. Conversely, elevated temperature curtails adsorption but augments the diffusion coefficient. At a pressure of 10 MPa, the system energy of oxygen-coal gangue undergoes the most substantial change (92.18 kcal/mol), and the energy peak exhibits the broadest displacement (0.7 kcal/mol), thus signifying the preeminence of pressure conditions in governing O2 adsorption and diffusion. At temperatures below 423.15 K, O2 molecules and coal gangue primarily undergo physical adsorption, with an amplified exposure of kaolinite (0 0–1) surfaces in coal gangue correlating to intensified adsorption. Within the pressure range of 0.2–10 MPa, the percolation process of oxygen in gangue slits unfolds across four discernible stages, with the structural characteristics of the slit channel, gas diffusion capacity, and oxygen consumption rate of coal gangue exerting a profound influence on the process. Based on these research findings, the reduction of pressure proves to be more efficacious in regulating the spontaneous combustion of coal gangue as compared to temperature control.

Research on the fire extinguishing performance of new gel foam for preventing and controlling the spontaneous combustion of coal gangue.

Coal gangue, as an associated product of coal mining, can cause a large number of piles to undergo slow oxidation and spontaneous combustion, resulting in the production of toxic and harmful gases, leading to casualties, environmental damage, and economic losses. Gel foam has been extensively employed as a fire-retardant material in coal mine fire prevention. The thermal stability and rheological properties of the newly developed gel foam were investigated in this study, as well as its oxygen barrier properties and fire extinguishing effect which were evaluated through programmed temperature rise and field fire extinguishing experiments. The experiment indicated that the temperature endurance of the new gel foam was around twice that of the ordinary gel foam, and this resistance decreased with the increment of foaming times. Moreover, the temperature endurance of the new gel foam with a stabilizer concentration of 0.5% was superior to that of 0.7% and 0.3%. Temperature has a negative effect on the rheological properties of the new gel foam, while the foam stabilizer concentration has a positive effect. The oxygen barrier performance experiment results showed that the CO release rate of coal samples treated with the new gel foam rose relatively slowly with temperature, and the CO concentration of coal samples treated with the new gel foam was only 159 ppm at 100 °C, which was significantly lower than 361.1 ppm after two-phase foam treatment and 715 ppm after water treatment. Through simulating the spontaneous combustion experiment of coal gangue, it was demonstrated that the new gel foam has a much better extinguishing effect than water and traditional two-phase foam. The new gel foam cools gradually and does not re-ignite during the fire extinguishing process, while the other two materials re-ignite after being extinguished.

Temperature Distribution Regularity and Dynamic Evolution of Spontaneous Combustion Coal Gangue Dump: Case Study of Yinying Coal Mine in Shanxi, China

The serious environmental pollution caused by the spontaneous combustion of coal gangue has become a problem which cannot be ignored in the world mining industry. It is urgently necessary to clarify the law of the temperature distribution of spontaneous combustion in gangue dumps and to grasp its future dynamic evolution of spontaneous combustion. In this study, the internal temperature of the second platform of the Yinying coal mine gangue dump was monitored on the basis of the self-developed wireless temperature monitoring system. Its temperature distribution was analysed, and areas of low (<80 °C), medium (80~280 °C), and high temperature (>280 °C) were delimited. The finite element method was also used to simulate its internal temperature development of 1–5 years. The results show that: (1) The high temperature area is mainly distributed on the side close to the slope. In the area 3 m deep, the high temperature started to propagate quickly. At a depth of 4 m, medium and high temperature represented 90% of the platform’s total surface area. At 6 m deep, temperature peaked at 667 °C. (2) The conduction of the internal temperature of the spontaneous combustion of gangue discharge is a non-linear conduction, and the conduction of heat in the horizontal direction is lower than the vertical direction. (3) During the spontaneous combustion of gangue discharge over the next five years, the overall temperature increase is faster at first, then it decreases and eventually stabilises. The high-temperature zones extend 10 m from the slope to the interior in five years, and the high-temperature zones are oval-shaped. This study provides a theoretical reference for the prevention and control of spontaneous combustion of coal gangue dumps.

Experimental study and molecular simulation of spontaneous combustion of coal gangue by oxidation under different water contents

ABSTRACT To determine the effect of water contents on the oxidation spontaneous combustion of coal gangue, the properties and combustion characteristics of coal gangue were studied using industrial and elemental analyses and Thermo Gravimetry-Differential Scanning Calorimetry (TG-DSC). The molecular dynamics simulation (MDS) and giant regular Monte Carlo simulation (GCMC)were used to investigate the adsorption isotherms of oxygen and coal gangue (kaolinite) under different water molecules (400, 500, 600, 700). The results of thermogravimetric showed that with increasing moisture content, the characteristic temperature points T3-T5 of CG4 were much lower than those of the other samples, the combustion conversion rate is the highest and the spontaneous combustion effect is the best at the same temperature. The molecular simulation results show that under 700 water-oxygen system, the adsorption of oxygen molecules and kaolinite (001) surface is the strongest. The interface has the fewest water molecules and the largest diffusion coefficient.

Assessing Potential Spontaneous Combustion of Coal Gangue Dumps after Reclamation by Simulating Alfalfa Heat Stress Based on the Spectral Features of Chlorophyll Fluorescence Parameters

The spontaneous combustion of coal gangue dumps after reclamation causes severe harm to the ecological environment surrounding mining areas. Using remote sensing technology to determine vegetation heat stress levels is an important way to evaluate the probability of a spontaneous combustion disaster. The canopy spectra and chlorophyll fluorescence (ChlF) parameters of alfalfa were collected through pot experiments to simulate different heat stress levels. Time series analyses of three ChlF (chlorophyll fluorescence) parameters showed that the regularity of the quantum efficiency of photosystem II (PSII) in light-adapted conditions (Fv′/Fm′) was stronger during the monitoring period. The correlation coefficients between the three ChlF parameters and the canopy raw spectrum, first derivative spectrum, and vegetation indices were calculated, and the spectral features were found to be more correlated. Lasso regression was used to further screen spectral features, and the optimal spectral features were the raw spectral value at 741 nm (abbreviated as RS (741)) and NDVI (652, 671). To discriminate among heat stress levels accurately and automatically, we built a time convolution neural network. The classification results showed that when the sequence length is 3, the heat stress is divided into three categories, and the model obtains the highest accuracy. In combination with relevant research conclusions on the temperature distribution law of spontaneous combustion in coal gangue dumps, three heat stress levels can be used to assess the potential of spontaneous combustion in coal gangue dumps after reclamation. The research results provide an important theoretical basis and technical support for early warnings regarding spontaneous combustion disasters in reclaimed coal gangue dumps.

Remote Sensing Monitoring of Vegetation Reclamation in the Antaibao Open-Pit Mine

After the regreening of the open-pit mine dump, vegetation usually needs to be managed and protected manually for several years before it reaches stability. Due to the spontaneous combustion of coal gangue, surface collapse, and other reasons, secondary damage may occur at any time. Regreening monitoring plays a vital role in the restoration and reconstruction of the mining ecosystem and can provide support for the timely replenishment of seedlings in the damaged area. In this study, remote sensing images were collected from 1986 to 2020 to obtain the NDVI distribution of dumps in the Antaibao open-pit coal mine. In order to obtain the overall growth law of regreening vegetation over time, the study adopted the unary regression analysis method and tested the correlation between NDVI and time by the Pearson correlation coefficient. However, through the Sen+Mann–Kendall trend analysis, it was found that there were differences in the trends of NDVI within the same dump. Next, by means of the Mann–Kendall mutation test and interactive interpretation, information, such as stable nodes of different regreening vegetation and vegetation growth patterns in degraded areas, were obtained. Through the above methods, the following conclusions were drawn: (1) The earlier the dumps were regreened, the more the areas were covered by significantly improved vegetation. In this study: 97.31% (the proportion of significantly improved vegetation in the south dump) >95.58% (the proportion in the west dump) >86.56% (the proportion in the inner dump) >79.89% (the proportion in the west expansion dump). (2) Different vegetation types have different time nodes for reaching stability. It takes about three years for wood, shrub, and a mix of grass, shrub, and wood to reach stability, but only one year for grass. (3) The destruction in mining areas is expansive and repeatable. Monitoring the growth patterns of regreening vegetation is conducive to understanding the reclamation effect, and provides a scientific basis for land reclamation planning and land management policies in the mining area. At the same time, the trend analysis method in this study can quickly extract problem areas after dump regreening and is applicable in most dumps.

Feasibility investigation of utilizing spontaneous combustion energy of abandoned coal gangue by constructing a novel artificial heat reservoir

In this paper, we present a novel artificial heat reservoir system for extracting spontaneous combustion energy of abandoned coal gangue. The construction process and operation method of the proposed artificial heat reservoir are introduced in detail. A multi-physical fields coupling model of seepage, heat transfer and oxidation of coal gangue is established. The spatio-temporal variation of temperature field, seepage field, oxygen concentration field and residual fuel amount in the oxidation process of coal gangue were numerically investigated. Sensitivity analysis of key parameters was carried out to provide reference for the optimization of artificial heat reservoir. Finally, the heat extraction performance of artificial heat reservoir was studied by using steel U-shaped tube, and its heating potential was evaluated. The results indicates that the process of spontaneous combustion of coal gangue can be divided into two stages: slow heating stage and rapid heating stage. The proposed artificial heat reservoir system presents a “low temperature zone-high temperature zone-low temperature zone” distribution from bottom to top. This alternating and layered temperature zones in vertical direction will form a thermal siphon effect and drive the air to flow upwards. In the rapid heating stage, the temperature increases faster with the increase of ventilation rate. When the porosity is greater than 0.35, it has a great influence on the spatial design of the heat extraction system. The specific heat capacity only affects the changing rate of temperature field and oxygen seepage velocity, but does not affect their final states. The thermal conductivity of coal gangue has little influence on each physical field of reservoir. The heat transfer rate of the middle part of the U-shaped tube is relatively large, the average value of which is about 150 W/m. The heat transfer of U-shaped tube only affects the area within the radius of 2 m. The research can provide a new idea for coal gangue disposal and heat utilization.

The thermal transformation behavior and products of pyrite during coal gangue combustion

Pyrite is a common and important mineral in coal and coal gangue, and its thermal transformation behavior and products during combustion have an essential impact on the environment, coal combustion technology, and recycling utilization of coal ash and coal gangue. Two samples of coal gangue containing high pyrite content were studied using XRD, TG-MS, SEM-EDS, and TEM to reveal pyrite's thermal transformation behavior and products during coal gangue combustion. The results showed that pyrite was transformed into hematite nanospheres during coal gangue combustion in air and released SO2 gas in the process. The transformation proceeds in the sequence of pyrite (0 ∼ 400 °C) – nano-microspheric magnetite and jarosite (400 ∼ 500 °C) – nano-microspheric hematite (500 ∼ 1000 °C). Nano-hematite possessed the morphology of a nanospheric pseudomorph of magnetite. Nano-magnetite and jarosite as intermediates were transitional and unstable and formed in a weakly reducing–weakly oxidizing environment. The formation and thermal decomposition of jarosite was associated with the release of structural water from kaolinite dehydroxylation. During the phase transition reaction, SO2 was released twice: the first release was related to the formation of magnetite and jarosite, while the second release was related to the thermal decomposition of jarosite. Temperature was the main factor affecting the nanocrystallization of hematite, whose crystallinity improved with an increase in temperature. This research portrays a new thermal phase transformation mechanism of pyrite in coal gangue, which can provide a theoretical basis for the recycling of coal gangue.

Enrichment and occurrence form of rare earth elements during coal and coal gangue combustion.

Coal ash has emerged as an important alternative source for rare earth elements (REEs). The enrichment and occurrence form of REEs among coal combustion products are of great significance for both technical design and economic evaluation of recovering REEs from the coal ash. Here, the enrichment and occurrence form of REEs in the ash were investigated. Compared with ashes from muffle furnace, coal fly ash (CFA) from power plants involved higher enrichment ratio of REEs, which was explained by the fractionation of coal ashes to concentrate REEs in finer CFA, higher combustion temperature to vaporize more volatile elements, and longer residence time of fly ash to absorb REEs in the gas. In addition, CFA samples were analyzed by sequence chemical extraction procedure (SCEP) and scanning electron microscope with an energy dispersive spectrometer (SEM-EDX), which revealed the important role of aluminum in the occurrence form of REEs compared with Si in aluminosilicates of CFA. This conclusion was further confirmed by thermodynamic equilibrium calculation, which also agreed qualitatively with the observation that REEs mainly existed in the solid phase. Both experimental and computational results of this work provided insights to understand the distribution of REEs in CFA and optimize their extraction processes.

Influence of biomass on multi-component reaction model and combustion products of coal gangue

The effects of biomass on coal gangue combustion characteristics, combustion products and combustion reaction model are studied in this paper. Based on the thermogravimetric experimental data, a multi-component combustion reaction model for coal gangue and biomass was established. The CG combustion reaction mechanism can be well explained by the two-component combustion reaction model. The participation degree of organic matter and inorganic matter is 90% and 10%, respectively. C3P1, C1P1 and C1P3 can be better explained by the five-component combustion reaction model. The reaction model corresponding to PS is a four-component combustion reaction model. Moreover, it is found that the addition of biomass can promote the combustion reaction of coal gangue and the production of gas products using Fourier transform infrared spectroscopy technology. Through combustion, the proportion of F4 mode of Cr, Cd, Pb, Cu, and Ni for CG sample increased from 92%, 60%, 52%, 28% and 60% to 95%, 90%, 82%, 91% and 94%, respectively. The toxicity reduction effect for Cd, Pb, Cu, and Ni is obvious, and the proportion of F4 mode is increased by more than 30%. Compared with other mixed samples, the ash formed by C1P1 is less harmful.

Preparation, Properties and Application of Gel Materials for Coal Gangue Control

In order to solve the problem of the spontaneous combustion of coal gangue, a coal gangue fire-extinguishing material of gel–foam was developed. The foaming agent was screened by the Waring blender method with varying foam amounts, and the superabsorbent foam stabilizer was synthesized by free radical polymerization. Moreover, the gel–foam was used in a spontaneous combustion of coal gangue mountain field practice. The results showed that when the mass fraction of sodium dodecyl sulfonate and coconut oil amide propyl betaine was 0.6% and 4:6, the foaming amount was as high as 1500 mL. When the mass ratio of chitosan to acrylic acid was 1:6, the neutralization degree was 80%, the cross-linking agent was 0.8%, and the initiator was 0.01%, the water absorption of the synthesized superabsorbent foam stabilizer reached 476 mL/g. The synthesized gel–foam was tested in a spontaneous combustion coal gangue hill in a certain area, and no reburning sign was found within one month.

Using UAV and Field Measurement Technology to Monitor the Impact of Coal Gangue Pile Temperature on Vegetation Ecological Construction

Coal gangue is an inevitable product in coal mining and processing and is the most important source of pollution in mines. Vegetation restoration of coal gangue piles must consider its special site conditions. Therefore, we conducted unmanned air vehicle (UAV) temperature monitoring, field investigation and experimental analysis on spontaneous combustion coal gangue piles in Lu’an mining area. In the vegetation construction of coal gangue piles, high-temperature stress affects plant survival. The spontaneous combustion coal gangue piles have abnormal temperature, high surface temperature and few vegetation types. The plant community species diversity index (Shannon–Wiener index, Pielou’s index and Species abundance index) is small, the plant community is single and the plant diversity is low. Spontaneous combustion of coal gangue leads to soil acidification, reducing soil water content, soil organic carbon (SOM), available nitrogen (AN), available potassium (AK) and available phosphorus (AP). These factors are single or interactive in plants and have an impact on plant survival and growth. The research results are of great significance to the vegetation restoration of spontaneous combustion coal gangue piles, ecological reconstruction and the improvement of the ecological environment of coal mine areas.

The Thermal Transformation Behavior and Products of Pyrite During Coal Gangue Combustion

The Thermal Transformation Behavior and Products of Pyrite During Coal Gangue Combustion

Effect of O2 concentration on combustion behavior and kinetics of coal gangue during oxy‐fuel combustion and oxy‐steam combustion

AbstractIn this work, the effect of O2 concentration on combustion behavior and kinetics of coal gangue during oxy‐fuel combustion and oxy‐steam combustion were studied by non‐isothermal thermogravimetric analysis technology. The results showed that the increase of O2 concentration could improve the combustion performance of coal gangue. The O2/CO2 atmosphere was unfavorable to the combustion of coal gangue compared with the O2/N2 atmosphere. Furthermore, the gasification reaction could accelerate overall carbon consumption in oxy‐steam combustion with 5% O2 concentration; and the presence of H2O could delay the ignition and accelerate burnout at this condition. Kinetic analysis showed that the combustion of coal gangue in O2/N2 and O2/CO2 atmosphere followed the first‐order kinetics under O2 concentrations studied; and the combustion in O2/H2O atmosphere followed the 0.5‐order kinetics at 5% and 10% O2 concentration, while it followed the first‐order kinetics at 21% O2 concentration.

The variations of free radical and index gas CO in spontaneous combustion of coal gangue under different oxygen concentrations

SummaryIn order to study the effect of oxygen concentrations on the change of active groups in the oxidation process of coal gangue, the airflows of different oxygen concentrations were prepared to simulate the oxidation and heating process of coal gangue under oxygen concentrations of 0%, 5%, 10%, 15%, and 21%. During the oxidation and heating process, the free radical parameters were measured at different temperatures in real time. The results show that in the early stage of coal gangue oxidation, the g factor remains at a lower level and do not start to increase until certain temperatures are reached. Besides, the higher the oxygen concentration is, the lower the temperature at which the g factor begins to increase. When the oxygen concentrations are 0%, 5%, 10%, 15%, and 21%, the corresponding temperatures are 225, 200, 150, 150, and 125°C, respectively. Furthermore, with the increase of oxidation temperature, the free radical concentrations experience four stages, namely, the slow increase stage, the rapid increase stage, the stagnant increase stage, and the final increase stage. And the higher the oxygen concentration is, the shorter the free radical stagnant increase stage is. During the oxidation of coal gangue, the line widths decrease slowly before 150°C, and then start to plunge and finally stabilize near the minimum at 350°C. Moreover, the higher the oxygen concentration is, the smaller the minimum values of line widths are. In the oxidation process of coal gangue, the gas product CO amounts are first at a lower level, and then begin to increase rapidly after 150°C. At the same temperature, the increased rates of CO production in coal gangue under the oxygen concentrations of 10%, 15%, and 21% are significantly higher than those under the oxygen concentrations of 0% and 5%. Based on the variation law of free radical parameters in coal gangue under different oxygen concentrations, the actual spontaneous combustion of gangue hills was analyzed and the free radical reaction mechanism of spontaneous combustion of gangue hills was discussed. The research results are of guiding significance for the treatment of spontaneous combustion of coal gangue.