Comprehensive evaluation on self-ignition risks of coal stockpiles using fuzzy AHP approaches

A safety assessment model of filling mining based on comprehensive weighting-set pair analysis

Filling mining is the main mining method in coal mine, and its safety is the pillar of the overall safety of the mine. Filling mining can effectively protect the surface environment, better solve the problem of ground pressure, and maximize the recovery of underground resources. Therefore, this method has an irreplaceable role in deep mining of coal mines and is highly valued by the mining industry all around the world. In order to evaluate the implementation effect of filling mining, a comprehensive weighting-set pair analysis safety evaluation model is established. This model optimizes the subjectivity of analytic hierarchy process (AHP) and the objectivity of Entropy Weight Method (EWM) in traditional methods. Besides, we add experts' weight to Entropy Weight Method. The combination of the two methods makes the index weight more reasonable and effective, and can more fully reflect the difference and correlation of index. Firstly, the accident causation analysis and taxonomy (ACAT) is used to find out the accident causation factors of filling mining, and then, the AHP and EWM are used to determine the weight of each evaluation index from different perspectives. Then, the evaluation group is established to score the importance of each expert, so as to reduce the subjectivity of expert scoring. Finally, according to the principle of set pair analysis, the safety evaluation model of filling mining is applied to Yuxing Coal Mine in Inner Mongolia. The evaluation result shows that the safety grade of this mine is grade 1 "safety." This paper provides a new way and direction for the comprehensive evaluation of similar mining methods, the establishment of index system, the acquisition of index weights, and the evaluation of safety level, which has promotion and application value.

Modeling the effect of emergency response on domino effects in the coal gasification process by fuzzy hierarchical analysis and Bayesian network

Emergency response has an important impact on the mitigation of the domino effects. However, consequence analysis of the domino effect often ignores emergency response due to its complexity and uncertainty. In this paper, Fuzzy Analytic Hierarchy Process (FAHP) is adopted to evaluate the reliability of emergency response process. On this basis, using Bayesian Network (BN) model, the domino effect under the influence of emergency response is modeled. Based on the total duration of the above-mentioned emergency response process to determine the consequences of domino effect under the action of safety barriers. The application of the approach has been demonstrated by an illustrative case study. The results show that the probability of domino effect is reduced by an order of magnitude when active barriers, passive barriers and emergency response are considered together. This work can provide relevant basis for formulating safety protection measures in chemical process industry.

Prioritizing risk factors of hazardous material road transportation accidents using the fuzzy AHP method

BACKGROUND

Annually, large amounts of hazardous materials (hazmat) are transported through the roads and this movement causes various accidents. Identifying the causes of these accidents is a critical issue for all public governments.

OBJECTIVES

This study aimed to identify the effective risk factors for hazmat road transport accidents and determine their relative weight using the fuzzy analytical hierarchy process (AHP) method.

METHODS

This qualitative study was conducted in 2021 in Iran and included four steps, i.e., the identification (using literature review and semi-structured interview), determination (according to the expert panel opinion), classification, and prioritization of effective factors in hazmat road transportation accidents. To prioritize and determine the relative weight of the effective factors, the fuzzy AHP technique was used.

RESULTS

In total, 159 risk factors were identified, which were classified into six factors (including road, transportation management, vehicle, cargo, driver, and weather conditions) and 24 bub-factors. The main factor (greatest relative weight) with the highest priority was the driver (0.181). The road (0.167), cargo (0.166), vehicle (0.169), transportation management (0.161), and weather conditions (0.159) were the next priorities, in that order.

CONCLUSION

The results demonstrated that the driver is the most important factor in causing accidents when transporting hazmat by road. The findings of this study might have the potential to decrease the frequency and consequence of accidents caused by the road transport of hazmat.

Influence of Mine Environmental Factors on the Liquid CO2 Pipeline Transport System with Great Altitude Difference

To prevent coal spontaneous combustion and store CO₂ in the coal mine, it is necessary to establish a fire-prevention pipeline transport system which continuously injects a large amount of liquid CO₂ from the ground to the underground area directly. At present, few studies are focused on the law of liquid CO₂ transport with great altitude difference. Moreover, the complex transport environment in the coal mine affects the design and application of the pipeline transport system for ground direct injection of liquid CO₂. This study explores the influence of environmental factors at different depths in the coal mine on the liquid CO₂ transport. Excessive altitude difference, ambient temperature and airflow velocity may lead to the boiling of liquid CO₂ during pipeline transport and a sudden drop in CO₂ temperature and pressure, which may cause danger in the pipeline transport system. The critical insulation thickness is determined based on the occurrence of the boiling of CO₂. In addition, the influence law of adding an insulating layer of different thicknesses to the CO₂ pipeline system is obtained. This study is of great significance to the establishment of a pipeline system that safely transports liquid CO₂ from the ground to the underground mine.

Online evaluation method of coal mine comprehensive level based on FCE

An online evaluation method of coal mine comprehensive level based on Fuzzy Comprehensive Evaluation method (FCE) is proposed. Firstly, following the principles of fairness, systematicness and hierarchy, taking research and development, production, sales, finance, safety and management as the first level indicators, a set of multi-level evaluation indicator system of coal mine comprehensive level combining objective and subjective evaluation indicators is established. Secondly, according to the characteristics of the indicator system, the specific process of FCE of coal mine comprehensive level is given. Then, taking SQL Server as the database management system and C#.NET as the development language, a set of B/S structure online evaluation system of coal mine comprehensive level based on FCE is designed and developed. Finally, the proposed method is applied to Coal group PM for test. The application shows that the method proposed can provide an efficient and convenient online evaluation platform to evaluate the comprehensive level of coal mines for the Coal group, and the horizontal and longitudinal comparison of the evaluation results can urge the coal mines to maintain their advantages and avoid their disadvantages, which is of some significance for improving the overall competitiveness of the Coal group.

Prediction of spontaneous coal combustion tendency using multinomial logistic regression

Spontaneous combustion of coal is a complex underground mining disaster, which mainly threats mine safety and efficiency. Several factors usually cause spontaneous combustion of coal, such as gas concentration, ventilation and coal properties. In this study, spontaneous combustion tendencies of coal mines were predicted considering the effective parameters for an underground coal mine in Turkey. Multinomial logistic regression, a multivariate statistical technique, was applied. Gas concentrations (CH₄, CO, O₂) and air velocity were defined as factors affecting spontaneous coal combustion. Fire hazard levels of the coal mines were determined as 'normal situation' and 'potential combustion'. It was observed that CH₄ and CO variables and CH₄ × CO interaction were effective in the formation of clusters. The results indicate that Mine I is more liable to spontaneous combustion than Mine II and Mine III. At the same time, the effects of variations in factors are examined in the study.

PM2.5-bound trace elements in a critically polluted industrial coal belt of India: seasonal patterns, source identification, and human health risk assessment

The concentration of trace elements like Fe, Mn, Cu, Zn, Ni, Pb, Cd, Cr, Co, and As in atmospheric particulate matter (PM2.5) was estimated to investigate their seasonal variation, potential sources, and health risk at Jharia coalfield, India, during May 2018 to April 2019. Measured PM2.5 (170 ± 45 μg/m3) exceeded the National Ambient Air Quality Standards (2009) by a factor of 4.25, the Clean Air Act, National Ambient Air Quality Standards (40 CFR part 50) by a factor of 11, and Air Quality Guidelines of World Health Organization (2005) by a factor of 16. Mean concentration of the trace elements were observed in the order of Fe > Mn > Cu > Zn > Cr > Pb > Co > Ni > Cd > As, highest being perceived at the monitoring sites affected by coal mine fire. The significantly higher HQ values posed by PM2.5-bound Cd, Cr, Cu, Pb, and As and higher HI values (multi-elemental exposure) indicated potential non-carcinogenic risk to the residents of Dhanbad. Higher ECR values in the coal mining areas of JCF indicated higher carcinogenic risk to the population (adults > children) of Dhanbad due to inhalation of PM2.5-bound Cr. Spontaneous combustion of coal in the mines, active mine fire, associated mining activities, heavy vehicular emission, and re-suspended road dust were recognized as the potential sources of the trace elements from the results of PCA and Pearson correlation analysis.

Extended Fuzzy Analytic Hierarchy Process (E-FAHP): A General Approach

Fuzzy analytic hierarchy process (FAHP) methodologies have witnessed a growing development from the late 1980s until now, and countless FAHP based applications have been published in many fields including economics, finance, environment or engineering. In this context, the FAHP methodologies have been generally restricted to fuzzy numbers with linear type of membership functions (triangular numbers—TN—and trapezoidal numbers—TrN). This paper proposes an extended FAHP model (E-FAHP) where pairwise fuzzy comparison matrices are represented by a special type of fuzzy numbers referred to as (m,n)-trapezoidal numbers (TrN (m,n)) with nonlinear membership functions. It is then demonstrated that there are a significant number of FAHP approaches that can be reduced to the proposed E-FAHP structure. A comparative analysis of E-FAHP and Mikhailov’s model is illustrated with a case study showing that E-FAHP includes linear and nonlinear fuzzy numbers.

Spatio-temporal variation of air pollutants around the coal mining areas of Jharia Coalfield, India

Jharia Coalfield (JCF) is one of the oldest coalfields in the eastern part of India and falls under critically polluted areas as per CPCB/MoEFCC Notification. Therefore, a study of air pollution and its management is the demand of the day. This study had been undertaken to know the current status of JCF concerning air quality. Ambient air quality monitoring with reference to particulate matter (PM₁₀ and PM_2.5), SO₂, NO_x and trace elements had been conducted in the coal mining areas of JCF. The study area was divided into two groups, mainly fire and non-fire for the sampling of air. Principal component analysis (PCA) identified coal mine fire as a major source of air pollution in the mining areas of JCF. Air quality index (AQI) was calculated which revealed that the air quality index of coal mine fire-affected areas was nearly 1.5 times higher than that of the non-mine fire areas. Graphical abstract.

Theoretical and numerical study on ignition behaviour of coal dust layers on a hot surface with corrected kinetic parameters

Industrial fires and explosions initiating from self-ignition of combustible porous dust deposits represent a serious hazard for human beings, environment and industry. Understanding the fundamental basis of combustible dust ignition behaviours at different geometries is of importance to prevent and mitigate the accidental risks. A correlation of self-ignition temperatures (SITs) measured by hot-oven tests and minimum ignition temperatures of dust layers (MITLs) determined by hot-plate tests has been established previously. However, this analogy approach based on Frank-Kamenetzkii model is limited by ignoring the influence of oxygen diffusion. In this work, an improved method is developed by implementing a correction factor for the pre-exponential factor caused by the boundary geometry. This method is testified by comparing with experimental data, previous analogy method and numerical simulation. Results show that our proposed method performs a better predictability of MITLs and simplicity. The improved analogy method indicates that the different boundary geometries of a dust deposit significantly impact the apparent pre-exponential factor, while have an ignorable influence on the activation energy, which is also verified by numerical investigations. Furthermore, the numerical model with the corrected kinetic parameters provides a satisfactory explanation compared with experimental observations regarding to temperature and concentration evolutions of dust layers.

Experimental Research into the Evolution of Permeability in a Broken Coal Mass under Cyclic Loading and Unloading Conditions

The permeability characteristics of a broken coal mass under repeated loading and unloading conditions exert significance on spontaneous combustion of coal in goaf during the mining of coal seam groups. Considering this, by using the seepage test system for broken coal-rock mass, seepage tests under cyclic loading and unloading conditions, were carried out on broken coal masses. The test results show that the fitting curves between permeability and effective stress, strain and porosity are a logarithmic function, cubic function and power function, respectively. Besides, the permeability of a broken coal sample under cyclic loading and unloading conditions is determined by its porosity, which conforms to the cubic law. With increased cyclic loading and unloading times, the permeability loss, stress sensitivity and the crushing amount of the broken coal sample were gradually reduced, but the particle size gradation of the broken coal sample gradually became better. During one loading and unloading cycle, the stress sensitivity of the permeability of coal samples in the loading stage was far higher than that in the unloading stage. In the loading stage, the re-arrangement, breakage and compressive deformation of coal particles can lead to a reduction in porosity, consequently resulting in a decreased permeability. In the unloading stage, only the permeability reduction of coal samples due to particle deformation can be recovered.

A study on the prediction method of coal spontaneous combustion development period based on critical temperature

Prediction of the development and evolution process of coal spontaneous combustion is of great significance to its prevention and control. Through the testing of different metamorphic degrees coal programmed heating characteristics and the infrared functional groups, the critical temperatures of the coalification process were analyzed and a method to predict the period of spontaneous combustion was established according to the characteristic of the critical temperature change. What can be inferred from this research is that the critical temperature of activation energy of coal in programmed heating experiments can characterize the nature of coal at low temperature and the macrocritical temperature point can be obtained from the characteristics of the activation energy change during the low-temperature period. The critical point of coal functional groups in terms of its micro changes is similar to its macro changes, the absorption intensity of the characteristic peak shows a general increasing trend, with an initial decline and then increase, followed by a decrease and a subsequent increase. In the high-temperature combustion process, the activation energy is not constant and changes from a negative value to 0, then the activation energy changes to a positive value, and finally goes down to a negative value. Therefore, the prediction of development period of spontaneous combustion can be achieved through the critical temperature of activation energy which acts as the critical temperature in high-temperature combustion process, and the prediction of low-temperature oxidation process is based on the critical temperature of activation energy in programmed heating process and the macro critical temperature of absorption intensity of coal functional groups.

A review on the mechanism, risk evaluation, and prevention of coal spontaneous combustion in China

In recent years, the ecology, security, and sustainable development of modern mines have become the theme of coal mine development worldwide. However, spontaneous combustion of coal under conditions of oxygen supply and automatic exothermic heating during coal mining lead to coalfield fires. Coal spontaneous combustion (CSC) causes huge economic losses and casualties, with the toxic and harmful gases produced during coal combustion not only polluting the working environment, but also causing great damage to the ecological environment. China is the world's largest coal producer and consumer; however, coal production in Chinese mines is seriously threatened by the CSC risk. Because deep underground mining methods are commonly adopted in Chinese coal mines, coupling disasters are frequent in these mines with the coalfield fires becoming increasingly serious. Therefore, in this study, we analyzed the development mechanism of CSC. The CSC risk assessment was performed from the aspects of prediction, detection, and determination of the "dangerous area" in a coal mine (i.e., the area most susceptible to fire hazards). A new geophysical method for CSC determination is proposed and analyzed. Furthermore, the main methods for CSC fire prevention and control and their advantages and disadvantages are analyzed. To eventually construct CSC prevention and control integration system, future developmental direction of CSC was given from five aspects. Our results can present a reference for the development of CSC fire prevention and control technology and promote the protection of ecological environment in China.