International Journal of Coal Science & Technology最新文献

{"title":"Time-shift effect of spontaneous combustion characteristics and microstructure difference of dry-soaked coal","authors":"Yikang Liu, Haiyan Wang, Huiyong Niu, Tao Wang, Zhiwen Chen, Yuqi Chen, Qingjie Qi","doi":"10.1007/s40789-023-00616-2","DOIUrl":"https://doi.org/10.1007/s40789-023-00616-2","url":null,"abstract":"Abstract The physical and chemical properties of the air-dried residual coal after soaking in the goaf will change, resulting in an increase in its spontaneous combustion tendency. This study aimed to look into the features and mechanism of soaked-dried coal's spontaneous combustion. Five samples of coal were dried to various degrees, and the weight loss features during thermal processing were examined. Based on this, the pore structure and chemical structure characteristics of the coal samples with the highest tendency to spontaneous combustion were quantitatively examined, and the mechanism by which soaking-drying affected the spontaneous combustion heating process of the remaining coal in goaf was investigated in turn. The results show that T 1 decreases with the increase of drying time, T 2 –T 6 shows a fluctuating change, and the ignition activation energy of 36-S-Coal is smaller than that of other coal samples. The pore type of 36-S-Coal changes from a one-end closed impermeable pore to an open pore, and the pore group area is large. During the 36 h drying process, the internal channels of the coal were dredged, and a large number of gravels and minerals were precipitated from the pores with the air flow. A large number of gravels were around the pores to form a surface structure that was easy to adsorb various gases. Furthermore, infrared spectroscopy was used to analyze the two coal samples. It was found that soaking and drying did not change the functional group types of coal samples, but the fatty chain degree of 36-S-Coal was reduced to 1.56. It shows that the aliphatic chain structure of coal is changed after 36 h of drying after 30 days of soaking, which leads to the continuous shedding of aliphatic chain branches of residual coal, and the skeleton of coal is looser, which makes the low-temperature oxidation reaction of 36-S-Coal easier. Based on the above results, the coal-oxygen composite mechanism of water-immersed-dried coal is obtained, and it is considered that the key to the spontaneous combustion oxidation process of coal is to provide oxygen atoms and accelerate the formation of peroxides.","PeriodicalId":53469,"journal":{"name":"International Journal of Coal Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136264059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of nanosized magnesia on the hydration of borehole-sealing cements prepared using different methods","authors":"Quanle Zou, Jinfei Zhan, Xin Wang, Zhen Huang","doi":"10.1007/s40789-023-00605-5","DOIUrl":"https://doi.org/10.1007/s40789-023-00605-5","url":null,"abstract":"Abstract Gas drainage is an effective technology for gas control in coal mines. A high borehole-sealing quality is the fundamental precondition for efficient gas drainage. The expansibilities of cement pastes used in borehole-sealing processes are critical for the borehole-sealing effect. Nanosized magnesia expansive agents are used to improve the expansibilities of cement pastes and improve the borehole-sealing effect. Nuclear magnetic resonance spectrometry and scanning electron microscopy were adopted to study the effects of nanosized magnesia on the hydration of borehole-sealing cements used with different preparation methods. The results showed that an increase in the mass fraction of the nanosized magnesia promoted cement hydration, and the mass fraction was positively correlated with the promotion effect. The use of different preparation methods did not change the water-phase distribution in the cement. When using the wet-mixing preparation method, nanosized magnesia promoted the induction, acceleration, and deceleration periods of hydration; when using the dry-mixing preparation method, the nanosized magnesia promoted the induction period of cement hydration, and the promotion effect was less obvious than that seen when using the wet-mixing method. When using the wet-mixing preparation method, the nanosized magnesia was uniformly dispersed, thus enlarging the surface area of the reaction, which provided more nucleation sites for the hydration products of the cement and therefore accelerated the hydration reaction. When using the dry-mixing preparation method, the nanosized magnesia powders were dispersed nonuniformly and aggregated. Under these conditions, only a few nanosized magnesia particles on the surfaces of the aggregated clusters took part in hydration, so only a small number of nucleation sites were provided for the hydration products of cement. This led to inconsistent hydration of cement pastes prepared using the dry-mixing method. The surface porosity of the cement prepared with the wet-mixing preparation method first decreased and then increased with increases in the mass fraction of the nanosized magnesia. The cement surface exhibited compact hydration products and few pores, and the surface was relatively smooth. In comparison, the surface porosity of the cement prepared using the dry-mixing method fluctuated with increasing mass fraction of the nanosized magnesia, resulting in a rough cement surface and microfractures on some surfaces. The two preparation methods both reduced the surface porosity of the cement. The wet-mixing preparation was more effective and consistent in improving the compactness of the cement than the dry-mixing preparation. These results provide important guidance on the addition of nanosized magnesia in borehole-sealing engineering and the selection of cement preparation methods, and they also lay a solid foundation for realizing safe and efficient gas drainage.","PeriodicalId":53469,"journal":{"name":"International Journal of Coal Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134909685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spoil characterisation using UAV-based optical remote sensing in coal mine dumps","authors":"Sureka Thiruchittampalam, Sarvesh Kumar Singh, Bikram Pratap Banerjee, Nancy F. Glenn, Simit Raval","doi":"10.1007/s40789-023-00622-4","DOIUrl":"https://doi.org/10.1007/s40789-023-00622-4","url":null,"abstract":"Abstract The structural integrity of mine dumps is crucial for mining operations to avoid adverse impacts on the triple bottom-line. Routine temporal assessments of coal mine dumps are a compliant requirement to ensure design reconciliation as spoil offloading continues over time. Generally, the conventional in-situ coal spoil characterisation is inefficient, laborious, hazardous, and prone to experts' observation biases. To this end, this study explores a novel approach to develop automated coal spoil characterisation using unmanned aerial vehicle (UAV) based optical remote sensing. The textural and spectral properties of the high-resolution UAV images were utilised to derive lithology and geotechnical parameters (i.e., fabric structure and relative density/consistency) in the proposed workflow. The raw images were converted to an orthomosaic using structure from motion aided processing. Then, structural descriptors were computed per pixel to enhance feature modalities of the spoil materials. Finally, machine learning algorithms were employed with ground truth from experts as training and testing data to characterise spoil rapidly with minimal human intervention. The characterisation accuracies achieved from the proposed approach manifest a digital solution to address the limitations in the conventional characterisation approach.","PeriodicalId":53469,"journal":{"name":"International Journal of Coal Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134908604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stability analysis of a slope containing water-sensitive mudstone considering different rainfall conditions at an open-pit mine","authors":"Guoyu Yang, Yanlong Chen, Xuanyu Liu, Ri Yang, Yafei Zhang, Jialong Zhang","doi":"10.1007/s40789-023-00619-z","DOIUrl":"https://doi.org/10.1007/s40789-023-00619-z","url":null,"abstract":"Abstract Mudstone, as a typical soft rock with wide distribution, has been endangering the slopes containing mudstone by its water-sensitivity of swelling and weakening strength when encountering water. To comprehensively understand the water-sensitivity of mudstone and reveal its influence on slope stability, we took the working slope containing water-sensitive mudstone of Shengli No.1 open-pit coal mine in Xilinhot, Inner Mongolia, China, as an example. Mudstone samples taken from the working slope were remodeled and saturated, and then triaxial tested to obtain the effective cohesion and effective internal friction angle. The filter paper method was used to obtain the soil–water characteristic curve of unsaturated mudstone. The pore structure of mudstone samples with different water contents were analyzed using the mercury intrusion porosimetry tests combined with the fractal dimension. The total pore content of the mudstone sample with lower water content is greater than that of the mudstone sample with higher water content. The mesopores are more in the mudstone sample with lower water content, while the small pores are more in the mudstone sample with higher water content. The variation of water content will change the complexity of mudstone pore structure. The higher the water content, the simpler the mudstone pore structure and the smoother the pore surface. Numerical calculations were conducted on the stability of the working slope under different rainfall conditions. The effective saturation on the mudstone layer surface changed and the plastic strain all occurred on the mudstone steps under different rainfall conditions. The key to preventing landslide of the slope containing water-sensitive mudstone in Shengli No.1 open-pit coal mine is to control the deformation and sliding of the mudstone layer.","PeriodicalId":53469,"journal":{"name":"International Journal of Coal Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135351947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Environmental performance assessments of different methods of coal preparation for use in small-capacity boilers: experiment and theory","authors":"A. N. Kozlov, E. P. Maysyuk, I. Yu. Ivanova","doi":"10.1007/s40789-023-00623-3","DOIUrl":"https://doi.org/10.1007/s40789-023-00623-3","url":null,"abstract":"Abstract The purpose of this article is to receive environmental assessments of combustion of different types of coal fuel depending on the preparation (unscreened, size-graded, briquetted and heat-treated) in automated boilers and boilers with manual loading. The assessments were made on the basis of data obtained from experimental methods of coal preparation and calculated methods of determining the amount of pollutant and greenhouse gas emissions, as well as the mass of ash and slag waste. The main pollutants from coal combustion are calculated: particulate matter, benz(a)pyrene, nitrogen oxides, sulfur dioxide, carbon monoxide. Of the greenhouse gases carbon dioxide is calculated. As a result of conducted research it is shown that the simplest preliminary preparation (size-graded) of coal significantly improves combustion efficiency and environmental performance: emissions are reduced by 13% for hard coal and up to 20% for brown coal. The introduction of automated boilers with heat-treated coal in small boiler facilities allows to reduce emissions and ash and slag waste by 2–3 times. The best environmental indicators correspond to heat-treated lignite, which is characterized by the absence of sulfur dioxide emissions.","PeriodicalId":53469,"journal":{"name":"International Journal of Coal Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134976235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In-situ gas contents of a multi-section coal seam in Sydney basin for coal and gas outburst management","authors":"Zhongbei Li, Ting Ren, Dennis Black, Ming Qiao, Itmam Abedin, Jessica Juric, Mike Wang","doi":"10.1007/s40789-023-00614-4","DOIUrl":"https://doi.org/10.1007/s40789-023-00614-4","url":null,"abstract":"Abstract The gas content is crucial for evaluating coal and gas outburst potential in underground coal mining. This study focuses on investigating the in-situ coal seam gas content and gas sorption capacity in a representative coal seam with multiple sections (A1, A2, and A3) in the Sydney basin, where the CO 2 composition exceeds 90%. The fast direct desorption method and associated devices were described in detail and employed to measure the in-situ gas components ( Q 1 , Q 2 , and Q 3 ) of the coal seam. The results show that in-situ total gas content ( Q T ) ranges from 9.48 m 3 /t for the A2 section to 14.80 m 3 /t for the A3 section, surpassing the Level 2 outburst threshold limit value, thereby necessitating gas drainage measures. Among the gas components, Q 2 demonstrates the highest contribution to Q T , ranging between 55% and 70%. Furthermore, high-pressure isothermal gas sorption experiments were conducted on coal samples from each seam section to explore their gas sorption capacity. The Langmuir model accurately characterizes CO 2 sorption behavior, with fit coefficients ( R 2 ) greater than 0.99. Strong positive correlations are observed between in-situ gas content and Langmuir volume, as well as between residual gas content ( Q 3 ) and sorption hysteresis. Notably, the A3 seam section is proved to have a higher outburst propensity due to its higher Q 1 and Q 2 gas contents, lower sorption hysteresis, and reduced coal toughness f value. The insights derived from the study can contribute to the development of effective gas management strategies and enhance the safety and efficiency of coal mining operations.","PeriodicalId":53469,"journal":{"name":"International Journal of Coal Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135407011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Online coal dust suppression system for opencast coal mines","authors":"Senju Panicker, S. S. Shankar, S. Jithin, S. Sandeep, Muhammed Irshad, Jerry Daniel, Tarique Sajjad","doi":"10.1007/s40789-023-00624-2","DOIUrl":"https://doi.org/10.1007/s40789-023-00624-2","url":null,"abstract":"Abstract Coal is the major source of power in India and world over. Coal mining is an essential industry which has a major role in the economic development of the country. Most major mining activities contribute directly or indirectly to air pollution. Coal dust is a major air pollutant which affects the personal working in the mines and also people residing in villages near the mines. Air pollution due to coal particulates can affect human health and cause damages to the environment. Hence effective pollution control mechanisms are needed to keep the pollution levels within permissible levels. The easiest and most common method employed for dust suppression worldwide is sprinkling of water. In majority of mines, water sprinklers are operated manually and can lead to wastage of water due to over sprinkling. It can also prove to be ineffective in dust suppression if sprinkling is not done properly. The paper proposes a system which can be deployed to automate the dust suppressions sprinklers. The system will monitor the concentration of PM 10 and PM 2.5 in the air and initiate sprinkling operation when the particulate matter content exceeds preconfigured limits.","PeriodicalId":53469,"journal":{"name":"International Journal of Coal Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135406827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling and petrophysical properties of digital rock models with various pore structure types: An improved workflow","authors":"Xiaobin Li, Wei Wei, Yuxuan Xia, Lei Wang, Jianchao Cai","doi":"10.1007/s40789-023-00627-z","DOIUrl":"https://doi.org/10.1007/s40789-023-00627-z","url":null,"abstract":"Abstract Pore structure is a crucial factor affecting the physical properties of porous materials, and understanding the mechanisms and laws of these effects is of great significance in the fields of geosciences and petroleum engineering. However, it remains a challenge to accurately understand and quantify the relationship between pore structures and effective properties. This paper improves a workflow to focus on investigating the effect of pore structure on physical properties. First, a hybrid modeling approach combining process-based and morphology-based methods is proposed to reconstruct 3D models with diverse pore structure types. Then, the characteristics and differences in pore structure in these models are compared. Finally, the variation laws and pore-scale mechanisms of the influence of pore structure on physical properties (permeability and elasticity) are discussed based on the reconstructed models. The relationship models between pore structure parameters and permeability/elastic parameters in the grain packing model are established. The effect of pore structure evolution on permeability/elasticity and the microscopic mechanism in three types of morphology-based reconstruction models are explored. The influence degree of pore structure on elastic parameters (bulk modulus, shear modulus, P-wave velocity, and S-wave velocity) is quantified, reaching 29.54%, 51.40%, 18.94%, and 23.18%, respectively. This work forms a workflow for exploring the relationship between pore structures and petrophysical properties at the microscopic scale, providing more ideas and references for understanding the complex physical properties in porous media.","PeriodicalId":53469,"journal":{"name":"International Journal of Coal Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135408314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A developed dual-site Langmuir model to represent the high-pressure methane adsorption and thermodynamic parameters in shale","authors":"Ke Hu, Qian Zhang, Yufei Liu, Muhammad Abdurrahman Thaika","doi":"10.1007/s40789-023-00629-x","DOIUrl":"https://doi.org/10.1007/s40789-023-00629-x","url":null,"abstract":"Abstract Comprehending the mechanism of methane adsorption in shales is a crucial step towards optimizing the development of deep-buried shale gas. This is because the methane adsorbed in shale represents a significant proportion of the subsurface shale gas resource. To properly characterize the methane adsorption on shale, which exhibits diverse mineral compositions and multi-scale pore sizes, it is crucial to capture the energy heterogeneity of the adsorption sites. In this paper, a dual-site Langmuir model is proposed, which accounts for the temperature and pressure dependence of the density of the adsorbed phase. The model is applied to the isothermals of methane adsorption on shale, at pressures of up to 30 MPa and temperatures ranging from 40 to 100 °C. The results show that the proposed model can describe the adsorption behavior of methane on shale more accurately than conventional models, which assume a constant value for the density of adsorbed phase. Furthermore, the proposed model can be extrapolated to higher temperatures and pressures. Thermodynamic parameters were analyzed using correctly derived equations. The results indicate that the widely used, but incorrect, equation would underestimate the isosteric heat of adsorption. Neglecting the real gas behavior, volume of the adsorbed phase, and energy heterogeneity of the adsorption sites can lead to overestimation of the isosteric heat of adsorption. Furthermore, the isosteric heat evaluated from excess adsorption data can only be used to make a rough estimate of the real isosteric heat at very low pressure.","PeriodicalId":53469,"journal":{"name":"International Journal of Coal Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135407197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural characterization of char during co-gasification from torrefied sludge and Yangchangwan bituminous coal","authors":"Xinsha Zhang, Yonghui Bai, Jie Qin, Shengli Shi, Jiazhong Liu, Shuaibing Wang, Minhui Zhao, Guiming Shi, Changbing Ye, Guangsuo Yu","doi":"10.1007/s40789-023-00638-w","DOIUrl":"https://doi.org/10.1007/s40789-023-00638-w","url":null,"abstract":"Abstract The present study aims to investigate the physico-chemical structural evolution characteristics of char structure of CO 2 atmosphere torrefaction pretreated sludge with Yangchangwan bituminous coal (YC) during co-gasification. The co-gasification reactivity of torrefied sludge and YC was measured using a thermogravimetric analyzer. The co-gasification reactivity of torrefied sludge with YC was thoroughly explored in depth by in situ heating stage microscope coupled with traditional characterization means of char sample (Scanning electron microscope, nitrogen adsorption analyzer, laser Raman spectroscopy). The results show that the gasification reaction rate of sludge treated under CO 2 atmosphere and coal blended char was better than other char samples at 1100–1200 °C. The torrefied sludge under CO 2 atmosphere promoted its thermal decomposition to the maximum extent, so that it eventually was transformed into a large number of small broken particles. The specific surface area and I D1 /I G ratio of blended char of torrefied sludge under CO 2 atmosphere and YC were 1.70 and 1.07 times higher than that of YC, respectively. The in situ technique revealed that YC char with the addition of torrefied sludge undergo gasification by shrinking core modes and the presence of obvious ash melting flow phenomenon. It was more obvious than that of YC.","PeriodicalId":53469,"journal":{"name":"International Journal of Coal Science & Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135388826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}