Coal Technology Research Articles

Prevention and Control of Spontaneous Combustion of Coal in the Goaf Under Z+I Ventilation Based on 2GN00 mining Process

ABSTRACT Traditional coal pillar mining technology will cause the waste of resources, and the roadway excavation. The N00 process eliminates the need for roadway excavation and coal pillar storage. The ventilation mode under the N00 construction method differs from conventional U-shaped ventilation. It is difficult to determine the danger area of spontaneous combustion. Therefore, this paper takes 21607 goaf with Z+I ventilation under the 2GN00 construction method in a mine in Guizhou province as the engineering background and adopts experimental research and numerical simulation methods to prevent and control coal spontaneous combustion hazards. Firstly, the spontaneous combustion tendency experiment determines the grade of spontaneous combustion tendency of coal samples. Secondly, the Fluent numerical simulation method is used to screen the optimal wind speed ratio of the two air inlets. Finally, numerical simulation is used to select the optimal spraying distance. The results show that the spontaneous combustion grade of coal samples makes it easy to produce spontaneous combustion. By analyzing the numerical simulation results of 6 groups of wind speed ratios, the best wind speed ratio of the two inlets is 1:1. Currently, the risk area of spontaneous combustion in the goaf is 5440.8 m2. Then the numerical simulation of the best slurry spraying distance is carried out with the wind speed ratio 1:1. The optimum distance of 90 m was finally determined. The area of the spontaneous combustion hazards area was reduced to 2223.8 m2. The results provide theoretical guidance and technical support for engineering applications.

Combustion Characterization and Kinetic Analysis of Coupled Combustion of Bio-Syngas and Bituminous Coal

The coupled combustion of bio-syngas and bituminous coal is an effective technology to reduce pollutant emissions from coal-fired power plants and improve the utilization rate of biomass energy. However, the effects of bio-syngas blending on bituminous coal combustion characteristics and reaction kinetics remain unclear, restricting the development of bio-syngas and bituminous coal combustion technology. In this study, the experimental studies on the coupled combustion of bio-syngas and bituminous coal under different bio-syngas lower-heating-value-based blending ratio (BLBR) were carried out by Micro-Fluidized Bed Reaction Analyzer (MFBRA), the coupled combustion characteristics and kinetic reaction mechanism of coupled combustion of bio-syngas and bituminous coal were analyzed. The results indicated that the nucleation and growth model (F1 Model) provided a reasonable description of the bituminous coal combustion process on the coupled combustion of bio-syngas and bituminous coal in MFBRA. The blending of bio-syngas significantly reduces the apparent activation energy and pre-exponential factor of bituminous coal combustion reaction. In particular, when the BLBR is 5, 10, 20, and 30%, the apparent activation energy is 48.70, 45.45, 46.75, and 42.35 kJ·mol−1, and the pre-exponential factor is 9.26, 7.10, 8.95, and 6.70 s−1, respectively. This research is helpful for improving the coupled combustion efficiency and ensuring the efficient operation of the coupled combustion system.

An Analysis of The Relationship Between ESG Performance and Corporate Value Across Industries

High-quality economic development requires sustainable green development of enterprises. This paper analyses the impact and path of Environmental, Social and Corporate Governance (ESG) practices on enterprise value under the pharmaceutical, coal, and information technology industries. It is found that: (1) ESG performance in the above three industries has a positive impact on enterprise value. (2) Due to the characteristics of the industries themselves, the paths of ESG on corporate value are different: information technology companies focus more on green technological innovation, the coal industry focuses more on internal stakeholder-centered ESG enhancement, and the path of ESG practices in the pharmaceutical industry is more diversified than that in the pharmaceutical industry, which is conducive to the realization of corporate value through a combination of the three major aspects of environmental, social, and corporate governance. This paper points out the shortcomings of the existing ESG practices through the universal experience of the three industries, which is of great significance for the major industries in the development and implementation of ESG activities.

Temperature-sensitive intelligent gel to prevent coal spontaneous combustion: Large-scale simulation fire extinguishing experimental study

Coal spontaneous combustion seriously endangers mine safety production. In this study, a temperature-sensitive intelligent gel was synthesised from methylcellulose (MC), polyethene glycol (PEG) and sodium chloride (NaCl). The flow characteristics of temperature-sensitive intelligent gel (abbreviated as TSIG) under different conditions were analyzed by viscosity test. An infrared spectrometer also analyzed the microscopic flame retardant mechanism of temperature-sensitive intelligent gel. A large-scale simulation fire extinguishing test bench was designed at the coal mine site to analyze the flame retardant effect of the temperature-sensitive intelligent gel on coal oxidation reaction at different injection temperatures. The results show that the temperature-sensitive intelligent gel undergoes a liquid–solid phase transition at a temperature higher than 60 °C. When MC: PEG: NaCl = 1: 6: 5, the temperature-sensitive intelligent gel showed the best flow characteristics. The large-scale simulation fire extinguishing experiments show that the CO concentration is significantly reduced after the temperature-sensitive intelligent gel is injected at the coal temperature of 300–900 ℃, and both show excellent fire extinguishing effects. The addition of temperature-sensitive intelligent gel can inhibit the number of free radicals in the process of coal oxidation, block the chain reaction of coal spontaneous combustion, and comprehensively inhibit the process of coal spontaneous combustion. The research results provided theoretical support for the application of temperature-sensitive intelligent gel in coal spontaneous combustion areas. Additionally, they guided the design of temperature-sensitive intelligent gel to prevent coal spontaneous combustion technology.

Co-firing characteristic prediction of solid waste and coal for supercritical CO2 power cycle based on CFD simulation and machine learning algorithm

The co-firing technology of combustible solid waste (CSW) and coal in the supercritical CO2 (S-CO2) circulating fluidized bed (CFB) can effectively deal with domestic waste, promote social and environmental benefits, improve the coal conversion rate, and reduce pollutant emission. This study focuses on the co-firing characteristics of CSW and coal under S-CO2 power cycle, and simulations are conducted by employing Multiphase Particle-in-cell (MP-PIC) method integrated with the comprehensive chemical reaction models in a 300 MW S-CO2 CFB boiler. Effects of operating parameters including fuel mixture proportion and first stage stoichiometry on the gas emission characteristics are further analyzed. Based on training and testing database based on the simulation results, a novel Improved Whale Optimization Algorithm and Bi-dictionary Long Short-Term Memory (IWOA-BiLSTM) algorithm model is established to predict CFB temperature, NOx emission concentration, and SO2 emission concentration, respectively. Results show that CO and SO2 decrease with the coal mass ratio of the fuel mixture increasing, while NOx increases. With the increase of first stage stoichiometry, CO increases, NOx declines, and the change of SO2 is not obvious. Compared with two other basic algorithm models, the prediction error of the proposed algorithm model for the three targets is minimal with the average relative error of 0.032 %, 0.231 %, and 0.157 %, respectively, which can meet the prediction requirements with acceptable accuracy.

Machine learning-based techno-econo-environmental analysis of CO2-to-olefins process for screening the optimal catalyst and hydrogen color

CO2 to light olefins (CTLO) is an attractive strategy for CO2 fixation to obtain high-value-added chemical products. Selecting the optimal catalyst and hydrogen source for the process has become increasingly challenging due to the wide range of developed catalysts and diverse hydrogen sources available. Herein, this study proposes a machine learning-based techno-econo-environmental analysis framework for screening catalysts and hydrogen colors for the CTLO process. The preferred machine learning model is employed to screen the most promising catalyst for the CTLO process, which is then applied to accomplish the conceptual design of the entire process to obtain essential material and energy balance results by process modeling and simulation. Finally, the techno-econo-environmental performance of the CTLO processes using various colored hydrogen are compared to provide more informed choices. The results indicate the extreme gradient boosting model exhibits superior predictive accuracy, making it suitable for integrating with the genetic algorithm to screen the optimal catalyst for the CTLO process. After multi-objective optimization, an optimal Fe-based catalyst is screened and used for the modeling and simulation of the CTLO process due to its highest light olefins yield (36.43%). The carbon, hydrogen, and exergy utilization efficiencies of the CTLO process considering solely the target light olefins are 59.58%, 21.71%, and 40.41%, respectively. After evaluating the impact of different H2 colors on the total operating cost, unit production cost, and minimum selling price of the CTLO process, it was found the CTLO process using gray H2 generated by coke oven gas and coal gasification technologies exhibits the most favorable cost-effectiveness and optimal market price compared to alternative production scenarios. However, using green H2 proves highly advantageous for the CTLO process in attaining comprehensive negative carbon emissions throughout its lifecycle. Moreover, it anticipates the influence of technological advancements and market fluctuations on the market competitiveness of CTLO processes with diverse hydrogen colors.

Evolutionary game study and empirical analysis of the adoption of green coal mining technology: A case study of ITMDB

The world is facing the challenge of energy transformation, and the integrated technology of mining, dressing, and backfilling (ITMDB) is a green mining technology that can effectively reduce resource waste and environmental pollution, thereby promoting sustainable development in the traditional energy sector. However, widespread adoption of ITMDB remains limited due to various factors. To address this, we construct an evolutionary game model between the government and coal enterprises. With system dynamics simulations, we analyze the impacts of subsidy, punishment, information sharing policy and their combinations on ITMDB adoption. Then, Empirical research was conducted to validate the simulation results and analyze the mechanism and heterogeneity effects using data from A-share listed coal companies in China. The results show that (1) A combined strategy of punishment and information sharing is most effective in encouraging ITMDB adoption. (2) The subsidy policy can have a negative effect in certain situations. (3) The optimal adoption strategy promotes technology adoption through executives green cognition (4) The optimal adoption strategy has the most significant effects on enterprises located in the central and eastern regions, areas with a lower proportion of secondary industry, and mature companies. Finally, this study provides policy recommendations for ITMDB adoption.

Retrofitting Coal Power Units with Biomass and Coal Cofiring Intensifies Air Pollution and Health Risks.

Retrofitting coal power units with biomass and coal cofiring technology provides a promising pathway toward low-carbon transition. However, such a retrofitting approach may also pose potential environmental and health risks, even aggravating regional disparities. Here, we propose a comprehensive framework to evaluate the associated risks of Biomass and Coal Cofiring Retrofit (BCCR) in China. We find that air pollutants such as SO2, PM2.5, and NOx will increase by an average of 27.9, 38.04, and 42.79% respectively compared to the scenario with no BCCR. The national-wide PM2.5 concentration-related premature mortalities in scenarios with BCCR are projected to increase by 23.53% on average in 2030. Moreover, the Highest-20% of provinces with higher health risks (also health vulnerable groups such as the elderly and children concentrated area) are 19 times greater than that in the Lowest-20% group. Results suggest that implementing a Targeted Pollution Control strategy for areas with higher health risks would be an economical and effective way to reduce the total pollutants emissions and mitigate the regional disparities in health risks. Our research proposes stringent pollution control measures on biomass and coal cofiring retrofit in advance in regions with the utmost necessity to facilitate a fair transition toward clean energy.

Analysis of the Existing Air Emissions Detection Methods for Stationary Pollution Sources Monitoring

The application of coal technologies for energy generation leads to high pollutant emissions. Thus, governmental and international organizations have created new programs and laws for monitoring emissions. Recently, the government of Kazakhstan has introduced regulations for the measurement of emissions produced by factories and power plants. However, the requirements and Corecommendations for the monitoring methods have not been defined. Therefore, this article addresses the problem and focuses on determining the measurement errors made by optical SGK510 and electrochemical POLAR devices used for coal power plants. The hypothesis is based on the fact that there are currently no systems for monitoring probe drying, and its implementation is expensive. The main methods are analyzed, namely their operation, taking into account the presence of water particles in samples, and the possibility of using adjustment coefficients is considered. The main pollutants chosen for analysis are CO, NO, NO2, NOx, SO2, and O2. Using the Broich–Pagan test, homoscedasticity was determined, and the Fisher test showed the possibility of using tuning coefficients. The data for the optical method were compared to measurements taken using Inspector 500. The error for SO2 determination was 7.19% for NO, 44.0985% for NO2, 733.26% for NOx, 7.39% for O2, 2.75% for CO, 60.81%. The comparison between SGK510 and POLAR demonstrated the following errors: for CO—1.5%, for NOx—82.4405%, for SO2—41.17%, for O2—11.61%. According to the Fisher criteria analysis of the optical method, only SO2 and CO values measured by SGK510 in comparison to Inspector 500 had close similarity, while others demonstrated high deviations. The significance tests were carried out by Fisher’s, t-test, and ANOVA methods. For the electrochemical measurement, only CO values had close similarity. In the future, methods will be proposed to improve the accuracy of the system while reducing maintenance costs, as well as cleaning sampling systems. The multicomponent analysis application for accuracy improvement with the exhaust gas humidity, temperature, and flow consideration was recommended as a possible solution.

Non-Pillar Coal Mining by Driving Roadway During Mining Period in High-Gas Top-Coal-Caving Working Face

To solve the problem of the inability to achieve Y-shaped ventilation in the boundary coal mining of high-gas mines and the problem of gas accumulation in the upper corner of a fully mechanized mining face, non-pillar coal mining technology is proposed by a driving roadway during the mining period. A high-gas working face requires Y-shaped ventilation to achieve upper corner gas control, but Y-shaped ventilation conditions are not available at the boundary coal body. In order to handle this challenge, studies have suggested non-pillar coal mining technology, which involves excavating roadways while mining in order to achieve non-pillar coal extraction and use recoverable wide coal pillars. During the simultaneous excavation of a working face and roadway, studies analyzed the distribution characteristics of the complicated stress environment. Following an evaluation of the impact of coal pillar width on the quality of an excavation roadway, this study’s development is in terms of an effective technique for retaining coal pillars as established. During the mining period of a working face, in the goaf of the working face, the research analyzed the distribution properties of the gas flow field, and findings from the study indicate that the width of the recovered coal pillar influences the distribution of gas. Finally, the width of the coal pillar was comprehensively determined, forming non-pillar coal mining technology by a driving roadway during the mining period. The on-site practice has shown that using a wide coal pillar with a width of 70 m to protect the roadway significantly reduces the deformation of the surrounding rock in the mining roadway, the gas concentration at the return airway is lower than the safety production standard, and by decreasing the mining succession time by 15 months, studies achieved improving the working face’s coal extraction rate by 12.6%.

Applicability of blue algae as an activator for microbial enhanced coal bed methane technologies

The blue algae can be used as a nitrogen agent for promoting biological coalbed methane, but its applicability and microbial mechanism in different microbial enhanced coalbed methane technologies kept unknown. This study evaluated the methanogenic efficiency of blue algae addition with a mass ratio of 10% under fermentative degradation and microbial electrolytic cell technologies, and studied the changes of coal microstructure, surface functional groups, organic components and microbiome. The results showed that the algae addition affected the micro-concave-convex structure, non-uniform distribution of micro-particles and micro-cracks of coals, and finally increased the methanogenic rate by 1.74–2.66 times. The algae addition mainly affected the coal organic components including hydroxyl structure, hydrocarbon structure, aliphatic oxygen-containing functional groups and aromatic structure, as well increased the humus acids and microbial metabolites in fermentation broth; among them, the increased metabolites showed great differences between different technologies. The algae addition mainly increased the genera belonging to phylum Bacillota (such as Bacillus and Clostridium) and methanogens (Methanosarcina and Methanoculleus). These Bacillota groups could degrade organic matter into acetate and methanol via pathways of glycolysis and benzoate degradation, which provided substrates for such methanogens. This study strengthened the effectiveness of blue algae in enhancing technologies for biological coalbed methane.

Reconfiguration of acid gas removal process matching the integration of coal chemical industry with green hydrogen

The focus of the acid gas removal process has shifted from decarbonization and desulfurization to desulfurization in the context of integrating coal chemical technology with green H2 without a water gas shift unit. The conventional Rectisol process, Selexol process, organic amine process, and sulfone-amine process have been reconfigured to form the R-Rectisol process, R-Selexol process, R-MDEA process, and R-Sulfolane-MDEA process to adapt to the shift of acid gas removal target. The removal efficiency of H2S and CO2, process energy consumption, and process cost are investigated to evaluate the technical and economic performance of the above four reconfigured acid gas removal processes. The results indicate that for the R-Recitsol process and R-Selexol process, both high pressure and low temperature increase the relative selectivity of H2S to CO2, thereby enhancing the selective removal of H2S. In contrast, for the R-MDEA process and R-Sulfolane-MDEA process, low pressure and low temperature improve the relative selectivity of H2S to CO2, thereby facilitating the selective removal of H2S. Under optimal operating conditions, the value of relative selectivity of H2S to CO2 of the R-Sulfolane-MDEA process is the largest, and the relative selectivity of H2S to CO2 of the R-Rectisol process, R-Selexol process and R-MDEA process are only 7.64 %, 12.85 %, and 68.40 % of the relative selectivity of H2S to CO2 of the R-Sulfolane-MDEA process, respectively. Compared to the other three reconfigured acid gas removal processes, the R-Sulfolane-MDEA process demonstrates superior advantages in both energy consumption and economic feasibility, provided that the H2S levels remain below 0.1 ppm in purified syngas. This study aims to enhance the decision-making process for gas purification methods in the coal chemical industry by considering integrated green H2 as an alternative to the water gas shift unit.

Innovative solid waste backfilling technology for top coal caving mining: analysing top coal movement and recovery optimisation

ABSTRACT The study introduces a novel solid backfilling technology, aiming to address gangue accumulation problem in top coal caving mining. To reveal its top coal drawing mechanism, discrete physical and numerical models were established. During the initial drawing stage, considerable amounts of low-position top coal are extracted, with yields fluctuating. As the working face advances, the drawing body shape shifts from knife-handle to semi-arch, and coal-gangue boundary curvature varies periodically. At low backfilling ratios, premature gangue exposure causes the loss of high-position top coal. Conversely, higher backfilling ratios facilitate the creation of a reconstructed floor, thereby enhancing top coal recovery.

Physical properties and hydration behaviors of paste casting brick containing coal gasification slag (CGS): Effect of curing condition and CGS dosage

In the process of developing coal chemical technologies, it is necessary to address environmental pollution and resource waste caused by the associated solid waste coal gasification slag (CGS). This study investigated the feasibility of using CGS as a substitute for fly ash (FA) in the preparation of paste casting bricks. The effects of curing conditions and CGS dosages on the physical properties of the specimens were investigated and related to the hydration behaviors through various microscopic techniques. The results showed that the occurrence of electrostatic flocculation and the enrichment of active substances increased the yield stress of the slurry as the CGS replacement rose, which manifested as decreased fluidity at the macroscopic level. The secondary hydration reaction was facilitated with the increased CGS replacement rate due to the desirable hydraulic activity of CGS. XRD, FTIR and TG results corroborated that the content of hydration products which contributed to strength development were enhanced with the addition of CGS under different curing conditions. XRD and SEM-EDS results indicated that the doping of elements such as Mg and Al under autoclaved condition led to a reduction in the grain size of tobermorite, and the micro-morphology tended to concentrate stresses under pressure. The results of this study promote the resourceful utilization of CGS in building materials and lay the foundation for further scale-up industrial application.

Characteristic and mechanistic study of enhanced carbon-based synfuel from biomass and coal by magnetite additive for synergistic co-carbonization technology

Biomass is a renewable and potentially carbon-neutral energy source and can be a promising alternative to fossil fuels in the ironmaking industry. The co-carbonization technology of biomass and coal for high-quality biofuel production has great potential. This study investigated the effects of the addition of magnetite (Fe3O4) on the physicochemical properties and combustion performance of wood shavings (WS) and bituminous coal (BC) (WS/BC = 4/6) sintered with a carbon-based synfuel. The results indicate that increasing the proportion of 2 wt% Fe3O4 can increase the high calorific value to 34.60 MJ kg−1 and the maximum combustion rate temperature reaches 469 °C, however, increasing the proportion decreases the burnout temperature to 575 °C, and the activation energy of the rapid pyrolysis stage decreases to 43.54 kJ mol−1. In addition, the activation energies of WS/BC char in the fast co-pyrolysis stage and the combustion reaction decrease significantly to 43.54 kJ mol−1 and 92.96 kJ mol−1, respectively, with the addition of 2 wt% Fe3O4. The area ratio of the fitted aromatic C−O reaches 79.91 %. Fe3O4 can form active centers on the surface of a carbon-based synfuel, improving the stability and orderliness of the fuel. The catalysis of the Fe3O4 additive with macromolecular organic compounds involves mainly oxygen-containing functional groups, promoting the cleavage of C−C bonds connected to oxygen-containing functional groups. In general, these results provide certain theoretical guidance for the preparation and application of sintered carbon-based synfuels.

Analysis of difficult flotation mechanisms for coarse low-rank coal: Comparing fluidized-bed and mechanical flotation technologies

Efficient flotation of coarse low-rank coal is essential for enhancing energy utilization in the mineral processing industry. As the beneficiation equipment scales up, the precision of particle size classification before flotation decreases, leading to a higher coarse particle content in the feed, which poses significant challenges to traditional flotation processes. Recent advancements in fluidized bed flotation technology have demonstrated considerable advantages in the flotation of coarse-grained metallic minerals; however, its application to coarse low-rank coal remains relatively unexplored. This study investigates the potential of fluidized bed flotation technology for coarse low-rank coal, employing various analytical methods to elucidate difficult flotation mechanisms. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were utilized to comprehensively characterize the surface morphology and chemical composition of coal samples. The influence of increasing particle size on flotation performance was systematically assessed through measurements of induction time and critical detachment amplitude. Comparative flotation experiments were conducted to evaluate the efficacy of traditional mechanical flotation against fluidized bed flotation technologies. Results indicate that the presence of cracks and oxygen-containing functional groups on the coal surface significantly enhances hydrophilicity, hindering flotation recovery rates. With increasing particle size, the induction time between particles and bubbles lengthens, while the critical detachment amplitude decreases, weakening the attachment and increasing detachment likelihood. Although high-efficiency collectors enhance coal particle hydrophobicity, they cannot fully mitigate the turbulence disrupting bubble-particle interactions in mechanical flotation. Conversely, fluidized bed flotation effectively minimizes turbulence interference, leading to an approximate 40 % increase in the recovery rate of coarse low-rank coal (0.25–1.00 mm) compared to traditional mechanical flotation. This study presents a novel technological approach for the efficient recovery of coarse low-rank coal, contributing to the clean utilization of low-rank coal resources.

TO THE ISSUE OF NON-PROJECT FUEL COMBUSTION

Nowadays, the issues of ecology and sustainable development are becoming more and more urgent, and the scientific community is actively looking for ways to more efficient and environmentally friendly use of renewable energy sources. One of such directions is the development and improvement of coal combustion technologies in aerodynamic furnaces. This paper offers a detailed analysis of this topic, looking at both theoretical aspects and practical applications. Aerodynamic furnaces are specialised devices designed to burn solid fuels such as coal with maximum efficiency and minimum environmental impact. The basic principle of operation of such furnaces is to create optimum conditions for complete combustion of the fuel, which is achieved through carefully designed aerodynamics and process control. The operation of the boiler on the coal of Karazhyra deposit is considered. This coal belongs to non-project fuel and improvement of its combustion processes is required to reduce harmful emissions and increase combustion efficiency. For the energy sector of the Republic of Kazakhstan, the conducted research is important, and the results obtained can be used to regulate and improve the operation of similar equipment, which contributes to improving environmental performance and overall efficiency of the country's energy systems.

Rapid multispectral image identification of coal and gangue based on super-resolution reconstruction

Accurate coal and gangue separation is crucial for efficient coal utilization. Multispectral imaging (MSI) offers a promising approach but often suffers from limited resolution, hindering accurate identification. This study proposes, a novel method, to our knowledge, combining super-resolution (SR) reconstruction and machine learning to enhance coal and gangue identification in MSI. A spectral attention mechanism and an enhanced multi-scale residual network with GAN (SAM-EMSR-GAN) were developed and evaluated alongside four established SR methods: SRCNN, VDSR, ESRGAN, and DRMSFFN. MSI images of 300 coal and 300 gangue samples were reconstructed, using each method to compare their performance. SAM-EMSR-GAN achieved superior reconstruction, attaining the highest structural similarity index (SSIM) of 0.906 and peak signal-to-noise ratio (PSNR) of 32.97 at 4× magnification. The study further investigated the combination of the SR method with seven widely used classification models: CatBoost, random forest (RF), support vector machine (SVM), least squares support vector machines (LSSVMs), eXtreme gradient boosting (XGBoost), ResNet50, and ResNet101. CatBoost consistently delivered the highest classification accuracy across all SR methods, reaching 97.32% accuracy at 959.37 nm when paired with SAM-EMSR-GAN. Independent validation using a separate dataset confirmed the robustness of this approach, achieving a 92.49% accuracy. These findings demonstrate the potential of combining SAM-EMSR-GAN and CatBoost for accurate and efficient coal and gangue identification, paving the way for intelligent and automated coal sorting technologies.

Effect of the main components in gasification wastewater on the surface properties of coal water slurry

AbstractCoal water slurry is an advanced and efficient clean coal technology; using gasification wastewater to prepare coal water slurry can recycle wastewater and improve energy utilization efficiency. As the complex substances in wastewater have a great influence on the slurry properties, the effects of organic matter, metal ions, and ammonia nitrogen in gasification wastewater on the surface properties of coal water slurry are studied in this paper in order to provide new ideas for slurry mechanism of coal water slurry prepared from wastewater. Results show the following: (a) Compared with ordinary coal water slurry, the concentration of coal water slurry prepared from wastewater with high organic content increased by 2.9%, while the concentration of coal water slurry prepared from wastewater with high ammonia nitrogen content decreased by 2.1%. (b) The contact angles of coal water slurry prepared with phenols, alcohols, and urethane are reduced by 2.8°, 6.3°, and 1.5°, respectively, so organic matter can change the hydrophilicity of coal particles and affect slurryability. (c) Mg2+ and Ca2+ have basically no effect on slurry. Fe3+ reduces the absolute value of Zeta potential by 33.1, and Cu3+ increases that by 22.8, as they affect the slurryability by changing the surface potential of coal particles and the absorption of additives. (d) Ammonia nitrogen influences the slurryability by changing the pH value of the slurry. The conclusion of the influence mechanism of organic matter, metal ions, and ammonia nitrogen in wastewater on slurryability can provide a technical reference for the selection of suitable wastewater to prepare coal water slurry.

The Effect of CO on the Exothermic Characteristics of Low-Temperature Oxidation in Coal

ABSTRACT In recent years, abnormally high concentrations of CO gas have often been detected in goaf areas of coal mines in China, which have posed a serious threat to safe production in coal mines and the life and safety of underground personnel. The effect of CO on the exothermic characteristics of low-temperature oxidation in coal was studied by analyzing the exothermic characteristics, heat release, oxidation stages, and activation energy of coal at different CO concentrations using a C600 microcalorimeter. The experimental results indicated that CO promoted the coal oxidation at low temperature, but inhibited it after reaching 144°C. When the CO concentration is 30%, the exothermic characteristics of coal in low-temperature oxidation adsorption stage were significantly affected, with the heat flow value decreased by 27.0% and the initial exothermic temperature point moved forward by 3.9 K. In the later stage of the oxidation reaction, the heat release of coal was linearly negatively correlated with CO concentration. The higher the concentration, the lower the heat release. These findings contribute to understanding the combustion mechanism of coal in high-concentration CO atmosphere and provide valuable insights for designing and optimizing coal utilization technologies.