Spontaneous Combustion Research Articles

Feasibility experimental study on plugging leakage in goaf based on two-phase foam

Air leakage in goaf often leads to coal spontaneous combustion (CSC), which not only directly affects the safety production of mines but also causes significant environmental damage. Therefore, effectively sealing the airflow in goaf is crucial for preventing CSC. Feasibility experiments on using two-phase foam to seal air leakage in goaf were conducted, leveraging the advantages of large flow rate, wide diffusion range, and good accumulation characteristics of two-phase foam. The research results indicate that continuous injection of foam into loose media with maintained ventilation can completely seal the air leakage, with the foam capable of withstanding wind pressures of nearly 600 Pa. When the foam is used for one-time sealing with a length of 2 m, it remains effective for 60 min, and the sealing effectiveness improves with longer distances sealed against air leakage. Numerical simulation analysis and field measurements of airflow leakage in mine working faces reveal that effectively sealing the airflow passage in the goaf behind the corner of the return airway is crucial for preventing CSC. Two methods are proposed for sealing external airflow during coal mining: foam injection using a point drilling method near the heading and an incremental buried pipe injection method. Finally, the feasibility of two-phase foam sealing technology for goaf airflow leakage is analyzed from multiple perspectives including sealing effectiveness, practicality, economy, foaming process, and engineering implementation. The research findings provide new insights into goaf sealing technology, aiding in addressing safety and environmental issues caused by spontaneous combustion in goaf areas.

Study on the characteristics and predictive model of autoignition induced by shock wave from high-pressure hydrogen leakage

Faced with climate change and increasing environmental pollution, countries around the world are actively exploring strategies for clean, renewable energy. However, under high-pressure conditions, hydrogen leaks can lead to spontaneous combustion, which significantly raises the safety risk of hydrogen applications. This study employs fluid dynamic simulation methods to investigate the development process of shock waves within tubes. It analyzes the effect of release conditions on the propagation speed and shock wave intensity, revealing the impact of shock wave intensity on the temperature distribution and gas composition variation within the hydrogen-air mixture boundary layer. The results show that the tube length and bends have relatively little impact on the shock waves, while discharge pressure and tube diameter significantly affect the propagation speed and intensity of shock waves. Combined with dimensional analysis and data fitting, a predictive model for autoignition of high-pressure hydrogen leakage is established: (Pr/Pa)((DXrx(H₂)rO₂))/Vs2) = 1505(X/D)−1.329.

Reaction mechanism of catalytic gasification by calcium-based catalysts and oxidized coal residues in coalfield fire zones

Fires originating from coal spontaneous combustion within coalfields result not only in substantial coal resource depletion but also producing residual low-activity pyrolysis coal chars exhibiting varying degrees of oxidation. These chars develop progressively through successive heat penetration at the fire front and post-fire extinguishment phases. This paper focuses on the alkaline earth metal-activated catalytic gasification of residual oxidized coal in fire zones, constructs a carbon-based model of oxidized coal in fire zones. The results show that the reaction active sites of the oxidized coal carbon matrix model are mainly concentrated on the carbon atoms at the end of the aromatic ring. During catalytic gasification, the calcium-based catalyst engages with these active sites, forming a preliminary catalyst. The transformation of oxidized coal into CO primarily occurs through two distinct routes. Calcium attaches to the surface of the oxidized coal’s carbon-based structure, establishing active sites. Acting as a facilitator, it aids the movement of CO2 to the carbon-based surface, leading to its further breakdown into CO. The catalytic species containing calcium persistently amalgamates with active sites on coal coke surface, fostering the release of additional CO. Moreover, these catalytic species with calcium also bind CO2 and unite with active coal coke sites, generating carbon–oxygen complexes on the surface. These complexes are thermally unstable and decompose, yielding CO and initiating the formation of fresh active sites on the coal coke surface. Consequently, they interact further with calcium-based catalytic species, culminating in the creation of catalyst precursors, which drive a recurrent catalytic reaction process.

A Lab-Scale Experiment on the Spontaneous Combustion Behavior of Chronic Naturally–Oxidized Coal in Re-Mining Coal Mine

ABSTRACT Spontaneous combustion of coal in re-mining coal mine is a serious threat to the safety recovery of coal resources. In this paper, six coal samples, including two raw bituminous coal samples from the new mining working face and four oxidized bituminous coal samples from the re-mining working face, are selected. The pore structures, thermogravimetric properties, and spontaneous combustion characteristics of raw coal and oxidized coal are studied. The pore structures show that the surface of oxidized coals has more cracks and higher macropore volume and porosity as compared with raw coal. The thermogravimetric experiments demonstrate that the oxidized coal has a higher combustion rate and turns to the combustion reaction zone in advance. Moreover, the oxidized coals perform a better combustion property by showing a comprehensive combustion index of 6.7 × 10−9 min−2·°C−3 and 8.9 × 10−9 min−2·°C−3, higher than the raw coal of 4.0 × 10−9 min−2·°C−3. The spontaneous combustion characteristics show that the oxidized coal performs a greater rate of oxygen consumption and more oxidation products released than raw coal. The CPT of raw coal is higher than 157°C, while the CPT of oxidized coal is between 132°C and 140°C. The research results can provide a risk assessment method for coal spontaneous combustion in the re-mining coal mine, and provide guidance for avoiding the occurrence of coal fires.

Prediction Model of Spontaneous Combustion of Lignite in Zhalainuoer Mining Area.

A programmed temperature-increase experiment was conducted on coal samples from four coal mines in the Zhalainuoer mining area to improve the accuracy of predicting and forecasting lignite spontaneous combustion. The gases produced during the coal tests were analyzed, and logistic, exponential, Boltzmann, and fourth-degree polynomial functions were selected to develop predictive models for the gas data. Additionally, the Boltzmann function was used to predict the occurrence of fire. The results revealed that the initial appearance temperature of CO was approximately 50 °C, and it exhibited an exponential growth trend with increasing temperature. The initial appearance temperature of C2H4 was approximately 140 °C, which could serve as an indicator of coal entering the accelerated oxidation stage. Applying the selection principle to gas indicators, CO and C2H4 were identified as single gas indicators for lignite spontaneous combustion in the Zhalainuoer mining area, whereas CO/CO2 and C2H4/C2H6 were identified as composite gas indicators. Among the four functions, the Boltzmann function model exhibited the best fitting effect for CO and CO/CO2 within the temperature range of 0-200 °C. The values of the four parameters (A 1, A 2, dx, and x 0) were determined based on their statistical characteristics, and a functional equation describing the relationship between gas concentration and coal temperature was derived. This indicates that the Boltzmann function model can be effectively used to predict the spontaneous combustion of lignite in the Zhalainuoer mining area.

Pore-fracture structures and seepage flow characteristics during spontaneous coal combustion based on CT 3D reconstruction

To study the evolution characteristics of the pore-fracture structures and seepage properties of coal in the process of spontaneous combustion, a high-temperature tube furnace was used to heat the coal samples. The coal samples were scanned using Xray-CT scanning technology, and the CT 3D reconstruction technology was used to extract the 3D pore structure and equivalent pore network model of each group of coal samples. Firstly, the specific surface area and volume of pore cleavage is statistically characterized; the change rules of Ep, Et, Lc, and Cn are quantitatively analyzed. At 200 °C, the coal body produces a large number of pore fractures, the development of coal samples is more significant, and the pore-specific surface area and the number of pore throats reached their maximum value. In addition, the changes of fractal dimension, porosity, connectivity, and permeability of coal with temperature were discussed, and the best permeability of the coal was achieved at 200 °C. The connectivity and permeability were weakened with the further increase of temperature, and the structural changes had a close influence on the gas seepage pressure and seepage flow rate. The results of the study provide important engineering guidance for deepening fire prevention in coalfields.

Study on Safety Mining Technology of Gob in Stopping Face by Replacing Pressure Equalization with Gob Pumping—A Case Study of Sitai Mine

Gas control in the upper corner of the natural coal mining face with high gas is always a difficult problem that troubles the safe production of the working face. Among them, a high gas-prone natural coal mining face with ground air leakage is more likely to cause gas and CO to exceed limits in the corner of the working surface and is difficult to control. The traditional treatment methods often have some problems; for example, it is easy to increase air leakage in the gob with the method of gas extraction in the gob, which is not conducive to the prevention and control of spontaneous combustion of coal in the gob. At present, the more effective method is the pressure-equalization method. However, the pressure-equalization measures need to establish a complex pressure-equalization system, and close cooperation between the systems is required; once the system power fails or equipment failure occurs, the pressure-equalization state changes randomly, and it is easy to cause gas over-limits and other faults. Therefore, this paper presents a new method to control gas in the gob of a coal seam by pumping the gob of the upper-adjacent layer, using the negative pressure of pumping, and balancing the negative pressure of the upper-adjacent layer and the gob of the coal seam to form a new pressure-equalization relationship. This method can prevent the toxic and harmful gases in the goaf of the upper-adjacent layer from escaping into the passageway of the gob of the local coal seam, reduce the air leakage in the goaf, and benefit the gas control and spontaneous coal combustion prevention in the goaf.

Classification of Composite Hazards of Gas and Coal Spontaneous Combustion in Gob

ABSTRACT To prevent the occurrence of gas and coal spontaneous combustion composite disasters in gob areas during coal mining, this study considers the gob area of the Longfeng Coal Mine as the experimental background. By analyzing the pressure values of the hydraulic props in the isolation wall, the composition of gases in the gob area, and the low-temperature oxidation characteristics of coal, it was found that the pressure values of the hydraulic props were correlated with the concentration of gases in the gob area, temperature, and the g-factor and free radical concentration of coal. The absolute values of the correlation coefficients were ranked as T > O2 > CH4 > CO2 > g-values > Ng > N2, and all correlation coefficients were greater than 0.85. When the isolation wall was located in the stress concentration area, the wall deformed and cracked, leading to frequent gas exchange between the gob-side entry retaining (GSER) and the gob area, which increased the risk of gas and coal spontaneous combustion composite disasters in the gob area. According to the safety risk level, the areas adjacent to the gob area were divided into high-risk areas (0 ~ 100 m, 300 ~ 600 m, 700 ~ 900 m, 1050 ~ 1200 m), moderate risk areas (200 ~ 300 m, 900 ~ 1050 m), general risk areas (600 ~ 700 m), and low-risk areas (100 ~ 200 m), the positions at 500 ~ 550 m and 700 ~ 750 m were located in the gas and coal spontaneous combustion composite disaster area. The study suggests that for high-risk areas, the injection amount of fire extinguishing materials should be increased to strengthen safety assurance, whereas for low-risk areas, the injection can be moderately adjusted and reduced to achieve the optimal balance between economic benefits and safety benefits.

Research regarding the influence of size on the compressive strength of spontaneous combustion coal gangue concrete utilizing the diffusion model

This passage employs the U2-Net model to segment images of spontaneous combustion gangue coarse aggregate (SCGCA) concrete cross-section and randomly placed aggregate library. These methods are used to construct the dataset and subsequently establish and train the diffusion model. Based on this model, a two-dimensional micro-mechanical model of SCGCA concrete was constructed, accurately reproducing the distribution, grading, and shape of the aggregate in the concrete. The size effect of SCGCA concrete is analyzed through experimentation and numerical simulation of two-dimensional micro-models. The findings of the study reveal that the dimension conversion factors for the 100 mm and 200 mm cubic specimens are 0.92 and 1.12 respectively, which demonstrates the evident size effect of SCGCA concrete. The remarkable coherence between the empirical results and the computational simulation results serves as a powerful validation of the durability and efficacy of the model delineated in this paper. In accordance with the theory of Bažant's size effect, this paper elucidates the size effect law of uniaxial compressive strength in SCGCA concrete models ignited spontaneously at different dimensions.

Oxidation and spontaneous combustion characteristics of particulate coal under stress–heat–gas interactions

Coal spontaneous combustion (CSC) is disturbed by complex downhole conditions. However, current research by scholars mainly focuses on the impact of single conditional disturbances on CSC, which is difficult to comprehensively characterize the oxidation and spontaneous combustion characteristics of granular coal in a complex environment. For this reason, a temperature-programmed gas chromatographer (TP-GC) hyphenated instrument and a C600 high-precision microcalorimeter was used for analysis. The variation rules of derived gas and oxidizing thermodynamic parameters in the coal oxidizing and heating process under stress-heat-gas interaction were obtained. The intrinsic action mechanism of stress-heat-gas interaction to increase the risk of spontaneous combustion of granular coal is described. The results showed that as the level of air leakage (AL) rate increased, the concentration of derived gases in the coal sample showed a “˄”-shaped trend, and the heat release intensity and heat release varied in stages, both reaching their peak at a leakage rate of 150 mL/min. Under different stress conditions, the heat release intensity and heat release of coal also reach their maximum at 150 mL/min, indicating a higher risk of spontaneous combustion of coal at 150 mL/min. As the stress increases, the coal‑oxygen reaction is inhibited, leading to a decrease in the concentration of derived gases and a reduction in the average heat release of the coal sample. This indicates that particulate coal is prone to spontaneous combustion when subjected to high air leakage rate and low stress conditions. The experimental results provide a theoretical basis for the prevention of CSC under complex conditions.

The prediction of the risks of spontaneous combustion in underground coal mines using a fault tree analysis method

Mining is one of the most risky and dangerous sectors. It is impossible to ignore the losses of life and material experienced by occupational accidents, which take place in the field of mining. Risk analysis begins with a risk assessment to identify the probability and severity of workplace hazards. Hazards must be controlled by precautions according to the risk score levels.In this study, a fault tree analysis method was conducted to analyze spontaneous combustion hazards and to predict future risks in underground coal mines. Three main causes of the top event were defined and for each of these causes, risk scores were computed using a fault tree analysis. Finally, the causes of spontaneous combustion, which is an event that is frequently encountered in coal mines, were discussed, and the spontaneous combustion risk probability was calculated as 0.3012 in cases of air entry into the gob and failure to prevent coal-air contact in development drifts. As a result of the study, the fundamental causes of spontaneous combustion, the greatest hazard in underground coal mining worldwide, have been examined in detail. The innovative approach introduced by the study aims to increase the awareness and recognition of conditions that lead to spontaneous combustion among industry workers and engineers through detailed evaluation. By doing so, it seeks to minimize the occurrence of spontaneous combustion incidents.•This paper introduces a main flowchart and countermeasure algorithm to prevent spontaneous combustion.•This paper also analyzes events which trigger spontaneous combustion and mentioned preventive measures for this events.

Experimental analyses of CO2 sequestration potential in mineralized fly ash and its efficacy in mitigating coal spontaneous ignition risks in underground mine goafs

To effectively utilize fly ash solid waste and realize fly ash resource utilization, carbon sequestration and emission reduction, as well as mine fire prevention and suppression, this paper analyses the components of fly ash by X-ray fluorescence spectrometer (XRF), rheological experiments, the CO2 sequestration experiments by the mineralization of fly ash, thermogravimetric analysis experiments, and flame-retardant property experiments. Additionally, the changes in the physical structure and morphology of fly ash before and after mineralization were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The carbon sequestration capacity and fluidity of fly ash slurry, as well as the ability of mineralized fly ash slurry to inhibit spontaneous coal combustion are comprehensively investigated. The research results indicate that CO2 is sequestered as calcite on the fly ash surface after mineralization. The optimal CO2 sequestration capacity of fly ash is 65.12 kg/t when 0.5 mol/L NaHCO3 is used as an additive. The fluidity of mineralized fly ash slurry is greater than that of fly ash slurry, and the lower the water-cement ratio is, the worse the fluidity. Mineralized fly ash slurry with a water-cement ratio of 3:1 has a strong carbon sequestration capacity and high fluidity, making it suitable for preventing coal spontaneous ignition in mine goafs. Mineralized fly ash slurry exhibits a regular trend where the better the mineralization effect, the lower the CO release during the low-temperature oxidation stage of coal, and the higher the cross-point temperature. Mineralized fly ash slurry has a stronger ability to inhibit spontaneous coal combustion than does ordinary fly ash slurry.

Recent Patents on Closed Coal Storage Systems and Research of Similar Experimental

Background:: Coal storage and conveying are key aspects of the coal industry, including coal stacking management systems and conveying systems. The traditional method of coal storage will easily lead to coal’s spontaneous combustion, which decreases the safety and reliability of storage. Meanwhile, problems are waiting to be solved with current conveying technologies, such as low levels of conveying efficiency. Objective:: To enhance the efficiency of coal conveying while improving safety and reducing environmental pollution, and promote the application of closed coal storage systems and pneumatic conveying technology. Method:: The patents and research proposed by many scholars analyzed the problems in coal transportation. Adopting pneumatic conveying technology and utilizing a similar experimental bench, by controlling the angle of the suction feeder and the height from the bottom, getting the optimal suction angle and position via experiment, which improves the efficiency of coal pneumatic feeding and discharging. Results:: A pneumatic feeding and discharging system and method are proposed for a coal storage silo with a high degree of integration and safety. Through similar experiments, it is concluded that the conveying efficiency is highest when the suction feeder is 30 mm high from the bottom, and the angle of the suction feeder is 45°. This provides theoretical support for the specific application of the device. Conclusion:: By analyzing patents and researching similar experiments, the proposed closed storage system for coal can improve coal conveying efficiency, reduce environmental pollution caused by coal particles during conveying, and decrease the possibility of spontaneous combustion and explosion of coal dust. The system is highly automated, easy to operate, and widely applicable.

Experimental Study on the Inerting Effect of Premixed Inert Gas of CO2 and N2 in Goaf

As the conventional inert gas, it is used for the prevention and control of coal’s spontaneous combustion, mainly N2 and CO2. However, there is limited research focusing on the inerting effect of composite inert gas. This paper studied the impact of using a premixed inert gas (N2 accounted for 50%, 60%, 70%, and 80%) instead of CO2 on the inerting effect of nearly horizontal and gently inclined goaf by building a physical similarity simulation experiment platform. The experimental results showed that the inerting effect of premixed inert gas was better than that of CO2. For instance, in a nearly horizontal goaf, the inerting effect of the premixed inert gas was optimal when the N2 accounted for 70%. The average O2 concentration in the monitored area decreased from 9.7% with CO2 to 6.4%. In addition, in the gently inclined goaf, the premixed inert gas exhibited an accumulation state similar to CO2, primarily occurring in the lower part region adjacent to the working face. Furthermore, the accumulation state of premixed inert gas was inversely proportional to its inerting effect. This study has important reference significance for applying inert gas fire prevention and extinguishing technology in mines.

Коррозионно-электрохимические исследования стали марки Ст3 с различными видами обработки

Fires at the petrochemical industry facilities cause harm to human life and health and significant economic and environmental damage. Accidents associated with ignitions at oil and petrochemical storage facilities in 2018–2022, resulted in injuries of 21 persons, and 10 fatalities; the total economic damage exceeded 1.5 billion rubles. One of the causes of fires is the spontaneous combustion of pyrophoric corrosive deposits (17 %). As a result of the reaction of the interaction of iron disulfide with oxygen in the air, pyrophoric corrosive deposits ignite. Large-scale steel equipment containing sulfurous oil is exposed during operation to corrosive and mechanical wear, risk of fires, and explosions. One of the protection methods of oil and gas equipment against corrosion and pyrophoric formations is surface treatment with paint anticorrosive coating. Modern paint coatings proved to be ineffective in ensuring anticorrosive protection of metal equipment. The main objective of the article is to study various options of metal surface treatment by electrochemical methods with the following comparison of their protective ability. The efficiency (isolating ability) of various treatments of St3 steel has been analyzed. Based on the results of electrochemical corrosive studies, chronogalvanometric curves have been built. Therefore, to determine the efficiency of the protective effect of anticorrosive paint coatings, the accelerated corrosive-electrochemical method is recommended. For the treatment of the oil equipment surface, the anticorrosive paint coating containing the following layers: inhibitor (urotropinу solution); primer (sodium polyacrylate, ethyl alcohol); and two layers of sodium polyacrylate, have been proposed to use. The application of this protective coating will ensure a fault-free mode of operation of oil equipment for more than 10 years without coating replacement. This will guarantee the safe work of employees at the petrochemical industry facilities.

Low-rank coal upgrading to optimize its utilization as fuel

Abstract Indonesia’s coal resources and reserves are mostly categorized as low-rank coal, lignite and sub-bituminous coals. Most of them have a high content of moisture, a low calorific value, and a high tendency to low-temperature oxidation and self-combustion, making them difficult to transport over long distances. To increase the utilization of the low-rank coals, a drying treatment was carried out by heating the coal at a temperature and pressure of 160°C and 3.5 Bar respectively for about 15 minutes. Two low-rank coal samples, from South Sumatra (A coal) and South Kalimantan (B coal) were used in this research. The result indicates that the degree of dewatering of A coal is 89.00% while B coal is 95.5%. B Coal has a higher inherent moisture content which generally has more capillary water which is relatively easier to remove. The higher the degree of dewatering the higher the calorific value degree of improvement. The calorific value of the A coal increased by 27.16% and the B coal increased by 40.65%. The combustion characteristic obtained from the thermogravimetry-differential thermal analysis shows that the A and B upgraded coals have a lower tendency to spontaneous combustion than that of the raw coals.

Simulation of air pipe heat dissipation in civil aircraft water system based on flowmaster

Abstract The water supply method of civil aircraft water system is mainly from the bleed air system to pressurize the water tank. However, the gas temperature from the bleed air system is often too high. The AC-25.863 draft [1] stipulates that the maximum surface temperature of the equipment should be lower than 50°F below the spontaneous combustion point of flammable liquid in the area. Otherwise, it will become the ignition source of flammable materials. In this paper, by establishing the heat transfer model of an air pipeline, a set of air duct heat transfer calculation methods is proposed, and the variation rule of air pipe surface temperature is studied, to verify that the gas temperature from the bleed air system meets the requirements of the system, and the air pipe surface temperature meets the requirements of AC-25.863 draft.

Insight into the formation mechanism of higher-molecular-weight gases during the spontaneous combustion of coal

Higher-molecular-weight gases (HMWGs), which have not received much attention, also contain invaluable information about the coal spontaneous combustion (CSC) development process. In order to investigate the formation mechanism of HMWG, the emission behaviors of HMWG from coal oxidation and pyrolysis experiments were compared, and FTIR and ESR were used to analyze the microstructural evolution of the coal sample. The results show that the volume fractions of most HMWGs increased regularly with increasing temperature. The contribution of the pyrolysis process to the yield of most hydrocarbon HMWGs was close to 100 %, while it was below 89 % for C4 ∼ C6 n-alkanes and benzene and less than 10 % for acetaldehyde and acetone. The decomposition of active structures could produce free radicals, the concentration of which increases with increasing temperature. The formation mechanism of HMWGs was proposed based on the experimental results: HMWGs came from both the thermal reaction and the coal-oxygen reaction process. The thermal reaction process would release the majority of hydrocarbon HMWGs from room temperature. Some active structures began participating in the coal-oxygen reactions to produce oxygen-containing HMWGs at 90 ℃. After reaching 170 ℃, the coal-oxygen reactions were further intensified to release minority n-alkanes, benzene, and small amounts of C4 olefins.

화물차의 제동장치에서 발생하는 과열 예측방안 연구

Recently, due to the increase in domestic and international online e-commerce platforms and the increase in container traffic at domestic ports, the operating ratio of large trucks has increased, and the number of truck fires is continuously increasing. In particular, spontaneous combustion is the most common cause of truck fires. Various academic approaches have been attempted to prevent truck fires, but due to the lack of research on the spontaneous tire ignition phenomenon that occurs during braking, this research directly designed and manufactured an experimental device to establish an environment similar to the braking system of a truck. A non-contact temperature sensor was installed on the brake device of the experimental device to collect temperature data generated from the brake device. Based on the data collected from the temperature sensor of the brake device and the temperature sensor on the tire surface, the ARIMA model among the time series prediction models was used to Appropriate parameters were selected to suit the temperature change trend, and as a result of comparing and analyzing the measured and predicted data, an accuracy of over 90% was obtained. Based on this, a plan was proposed to reduce the rate of fires in trucks by providing real-time warnings and support for truck drivers to respond to overheating phenomena occurring in the braking system.

Study on the preparation and characteristics of thickened slurry to prevent coal spontaneous combustion

In response to the problems of small diffusion area, short solidification time, and poor flowability of existing fire extinguishing materials in preventing coal spontaneous combustion in goaf areas of western mining areas, this paper studies a thickened slurry with good flowability and fast diffusion ability. The optimal ratio of thickened slurry was determined through orthogonal experiments, and the rheological properties, impregnation characteristics, and wall hanging characteristics of the material were studied. The results showed that when the water to soil ratio was 8:1, and the concentrations of sodium alginate (SA) and apigenin were 0.6 % and 0.5 %, the flowability and suspension performance of the thickened slurry were the best. When the soaking time is 14 days, the best soaking degree of the material can be achieved, with a soaking depth of 0.93 mm. Through wall hanging tests, it was found that the thickened slurry can naturally air dry on the surface of vertically placed coal pillars with a small sliding distance, which has good adhesion and retention characteristics. Further on-site experiments have shown that by injecting thickened slurry, the CO concentration at the return air corner is significantly reduced, indicating that thickened slurry can cover a large area of residual coal in the goaf, prevent contact between coal and O2, and effectively prevent the composite reaction between coal and oxygen.