Search

Ultra-wide band (UWB) radar can penetrate non-magnetic media such as coal and rock to detect life information of personnel after collapse. Due to the complex mining environment, UWB radar loaded with vital sign signals is prone to interference from environmental noise and clutter signals. It is difficult to recognize human subject information. This paper introduces the principle of UWB radar life detection system and its application in mine rescue. This paper summarizes the current research status of UWB radar life information recognition from three aspects: UWB radar life information extraction, dynamic and static human object recognition, and life quantification. This paper points out the current issues with the application of UWB radar life detection technology in the field of mine rescue. ① There is limited research on filtering methods for non-stationary signals and environmental noise in underground collapse environments. ② The extraction and representation methods for posture, behavior, life status, and other information of moving (or micro moving) objects need to be improved. The human life information recognition model is not yet perfect and the feature correlation between models is low. ③ There is a lack of solutions to the 'overlapping' problem caused by multiple objects. This paper proposes the prospects for the research direction of UWB radar life information recognition for mine rescue. ① It is suggested to continuously optimize noise and clutter adaptive filtering methods for multiple types of mine disaster environments. ② It is suggested to construct a human life information recognition model suitable for the field of mine rescue. ③ It is suggested to further improve the quantification capability of multi-object after mine shelter. ④ It is suggested to conduct depth exploration of the method for determining the optimal detection frequency band for UWB radar.

Deep well rescue technology refers to the key technologies involved in various aspects of rescuing trapped personnel during the process of deep well accident rescue. It mainly includes environmental detection technology, life detection technology, deep well rapid demolition technology, emergency communication network construction technology, and other auxiliary technologies to ensure the smooth progress of deep well accident rescue. Deep well rescue equipment refers to necessary hardware equipment and software platforms during the implementation of deep well rescue technology. Studying deep well rescue technology and equipment is crucial for ensuring the safety of trapped personnel and reducing accident losses. The current research status of deep well rescue equipment and key technologies is analyzed. It is pointed out that existing rescue technologies and equipment cannot fully meet the complex and changing environmental requirements. There are problems such as insufficient research on the universality and specificity of rescue equipment, the need to improve the intelligence level of rescue equipment, difficulty in meeting the needs of complex rescue environments with network collaboration capabilities, and insufficient innovation research on rescue equipment. In order to solve the above issues, the development trend of deep well rescue equipment and technology is discussed. ① Deep well rescue equipment should be divided into specialized and universal categories based on different rescue scenarios. A single equipment should develop towards multifunctionality, high reliability, and high mobility. ② Rescue equipment is intelligent, precise, and self decision-making, achieving a rescue mode of intelligent equipment as the main focus and personnel as the auxiliary. ③ It is suggested to build a rapid networking, multi-mode networking, and integrated rescue network platform. ④ Although TDLAS integration does not currently meet rescue standards, its high resolution, high sensitivity, and integrability will play an important role in the future, achieving high integration, lightweight, and efficiency of environmental monitoring equipment.

The oxidation characteristic parameters of residual coal in working face change with the advance of coal seam. To explore the influence of dynamic oxygen-consuming environments, we examined the influence of reducing the oxygen concentration on the formation characteristics and characteristic parameters of coal oxidation products, conducted with temperature-programmed experiments under staged oxygen consumption. The correlation between the characteristic oxidation parameters was determined, and the critical oxygen concentration that determined the gas yield was obtained. The results show that after staged oxygen-consumption, the oxidation of coal is stronger than that under constant low oxygen, the oxidation products are greatly affected, and the influence of pyrolysis gas is small. The oxidation characteristic parameters such as gas product volume fraction, production rate, and heat release intensity are positively correlated with the oxygen-consumed temperature. We found that the oxidation reaction heat of coal is 180~330 kJ·mol−1, and the maximum and minimum exothermic intensities are significantly linearly correlated with the oxygen consumption rate. Finally, the critical oxygen concentrations for gas production rate under oxygen-consumed conditions were 17, 9, and 5%. These results have practical significance for strengthening the prevention and control of spontaneous combustion disasters in goafs. [ABSTRACT FROM AUTHOR]

Spontaneous coal combustion adversely affects coal mine safety and restricts safe, efficient, and green coal mining. Inert gas fire prevention and extinguishing technology is a widely used fire prevention and extinguishing method in coal mines. CO2 is often used as the primary raw material for inert gas fire prevention and extinguishing, owing to its good inerting and cooling characteristics. However, the lack of data on the physical and chemical properties and fire extinguishing mechanism of CO2 by field personnel has limited the efficient application of CO2 in coal mine fire prevention and extinguishing. To explore the practical application effects of CO2 fire prevention and extinguishing technology on coal mine sites, this paper summarised and analysed the research and development status of CO2 fire prevention and extinguishing technology and expounded the physical and chemical properties, phase characteristics, and fire prevention and extinguishing mechanisms of CO2. The CO2 pipeline, CO2 pipeline intelligent monitoring and control system, CO2 inerting mechanism, and comprehensive gas fire prevention and extinguishing technology are summarised and discussed. This study provides a systematic theoretical basis for the field application of CO2 fire prevention and extinguishing technology. [ABSTRACT FROM AUTHOR]

The molecular structure of coal is complex, and the existing research methods are limited, so it is difficult to clarify its influence mechanism on the spontaneous-combustion characteristics of coal. In this paper, the previous extraction, FTIR, TPR, TG-DSC and other experimental results are combined to analyze the extraction weakening effect and the correlation analysis of the spontaneous-combustion characteristic parameters of raffinate coal. The results show that extraction can destroy the connection bond of coal molecules, change the content of dominant active groups in the coal spontaneous-combustion reaction, increase the lower limit of the key temperature nodes of coal spontaneous-combustion or extend the temperature range, resulting in an increase in the ignition-point temperature of coal and a decrease in coal quality. This paper will provide a theoretical basis for the study of the microscopic mechanism of coal spontaneous-combustion and then provide new ideas for the development of an active prevention and control technology for coal spontaneous-combustion. [ABSTRACT FROM AUTHOR]

The acoustic temperature measurement method has a broad application prospect due to its advantages of high precision, non-contact, etc. It is expected to become a new method for hidden fire source detection in mines. The acoustic time of flight (TOF) can directly affect the accuracy of acoustic temperature measurement. We proposed a quadratic correlation-based phase transform weighting (PHAT-β) algorithm for estimating the time delay of the acoustic temperature measurement of a loose coal. Validation was performed using an independently built experimental system for acoustic temperature measurement of loose coals under multi-factor coupling. The results show that the PHAT-β algorithm estimated acoustic TOF values closest to the reference line as the sound travelling distance increased. The results of coal temperature inversion experiments show that the absolute error of the PHAT-β algorithm never exceeds 1 °C, with a maximum value of 0.862 °C. Using the ROTH weighted error maximum, when the particle of the coal samples is 3.0–5.0 cm, the absolute error maximum is 4.896 °C, which is a difference of 3.693 °C from the error minimum of 1.203 °C in this particle size interval. The accuracy of six algorithms was ranked as PHAT-β > GCC > PHAT > SCOT > HB > ROTH, further validating the accuracy and reliability of the PHAT-β algorithm. [ABSTRACT FROM AUTHOR]

A gas explosion experimental system based on a piece of 15 m-long and 9I8O semi-closed wide open steel pipe was constructed. An explosion experimental study on straight pipelines and pipeline structures with different angles (45°, 90°, and 135°) was conducted. Research results demonstrated that before the turn, flame propagation speed and flame sustaining time in different pipeline structures were consistent. With the increase of the distance away from the ignition source, the flame propagation velocity increases and the flame sustaining time decreases; at the turning point, the flame velocity suddenly decreases and the flame duration increases obviously. Meanwhile, the peak value of overpressure on the lateral wall of the turning corner is greater than that on the inner wall. Among the three different angles, the peak value of overpressure on the lateral wall of 135° bend is the highest. Different pipeline structures have great influence on gas explosion overpressure and flame propagation speed. These research conclusions provide theoretical references for gas explosion resistance in coal mines. [ABSTRACT FROM AUTHOR]

To address the challenges associated with the high gas content, high pressure, and low permeability coefficient in deep coal seams, strategies such as infilling boreholes and increasing the negative pressure of extraction are commonly implemented to alleviate issues related to coalbed methane extraction. However, long-term mining pressure can lead to the development of cracks in the coal seam near the borehole, thereby creating air leakage channels, which could potentially impact the oxygen supply during the extraction process. This leads to secondary disasters such as the spontaneous combustion of coal and gas explosions, considerably impacting the life and health of underground workers. To solve this issue, a thermal-fluid-solid coupling model for the working surface was constructed based on numerical simulation software, taking into account the multimechanism coupling effect of coal seam gas. The laws of coal oxidation and spontaneous combustion induced by coalbed methane extraction around boreholes were studied. The variation laws of the oxygen concentration, coal temperature, and oxidation heating zone around the borehole under different extraction conditions were simulated and analyzed. The findings demonstrate that the negative extraction pressure enables the gas to penetrate the fracture zone of the borehole, leading to an increase in the oxygen consumption rate and coal temperature around the borehole with an increase in negative extraction pressure. The coal gas leakage surrounding the borehole reduces as the sealing depth increases, and both the heating rate of coal and oxygen volume fraction show a downward trend. The fitting relationship between the negative pressure of drainage, depth of sealing, and temperature change in the coal body surrounding the boreholes was identified. It was determined that the negative pressure of 13 kPa for borehole drainage and a sealing depth >18 m are the optimal extraction parameters. The range of the oxidation zone and the position of the boundary line under this parameter were predicted, and the position function of the dangerous area of oxidation heating was defined. The research results have remarkable implications for the coordinated prevention and control of gas and coal spontaneous combustion in coalbed methane predrainage boreholes, as well as for efficient prevention and control of CO in on-site gas extraction boreholes, thus ensuring efficient and safe gas extraction., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)