Ventilation Network Research Articles

Parameterization of a ventilation network model for the analysis of mine working emergency ventilation modes

Digital simulation of mine fires and explosions is an important stage in the process of developing technical solutions and measures aimed at improving the safety of personnel involved in underground mining. Correct simulation results determine the effectiveness of decisions in the event of an actual emergency situation. In this regard, due attention should be paid to each stage of the simulation, and especially to the initial stage of model parameterization. This study formulates a general principle for determining the parameters of mine fire and explosion models, in order to assess their development using the AeroNetwork analytical package. Such parameters in the event of a fire are heat and gas (afterdamp) releases. In the event of an explosion, excessive pressure at the shock front in the explosion origin. It has been established that when simulating a fire, it is advisable to use equivalent heat and gas releases determined by the content of combustible components in the combustion origin. In the event of burning mining equipment, these parameters can be calculated on the basis of the technical characteristics of a machine. Furthermore, when simulating an unauthorized explosion of explosives, the excess pressure determined by the dimensionless length of the active combustion area is calculated taking into account the weight and specific heat of an explosive, as well as the geometric parameters of a mine working. When simulating an explosion of a methane-air mixture (firedamp), the excess pressure is calculated taking into account the gas content of rocks in terms of free combustible gases, the length of a blast cut, the size of the area of increased fracturing, and the lower explosive limit of methane. Based on the proposed principle of the parameterization of emergency models, as an example, a model of fire and explosion development in existing extended dead-end workings (more than 1000 m long) passing coaxially to each other at different heights was developed. The numerical simulation of different emergency situations in workings was carried out, taking into account performing mining in difficult mining conditions.

Application of the longitudinal ventilation system in the underground interconnected infrastructure: Assessment of flow distribution and confluence ratio

Longitudinal ventilation is widely employed in underground interconnected infrastructure, where the characteristic of the ventilated flow is distinctly different from the “normal” tunnels with a single structure. In this paper, the characteristic and the distribution of the ventilated flow in the underground interconnected infrastructure with longitudinal ventilation is studied. A small-scale experiment was carried out, where the effect of pressure rises and the location of the jet fan was taken into account. Results show that the ventilated velocity in a specified tunnel section is affected by the jet fan in the local tunnel section and the interconnected tunnel sections. For two interconnected tunnel sections that confluent at the junction point, with an increasing pressure rise in a specified tunnel section, the ventilated velocity in the local tunnel section increases whereas the ventilated velocity in another tunnel section decreases. The flow direction can even reverse to the opposite direction when the pressure rise of one tunnel section is large enough. To assess the variation of ventilated flow, the parameter of confluence ratio is defined and the prediction is established based on the theory of ventilation network, which can well describe the variation trend of the ventilation flow among different tunnel sections.

Possibilities of 3D laser scanning data utilization for numerical analysis of airflow in mining excavations

Underground mining of deposits is strongly dependent on several key processes enabling its safe operation. One of these processes is mine ventilation aimed at supplying an appropriate amount of air with a specific chemical composition, diluting harmful gases generated in technological processes and emitted from the rock mass, and ensuring appropriate climatic conditions at workplaces. For all that mine ventilation has strategic importance and is responsible for 30-40 % of overall mine operation costs. A very important task is to conduct calculations and simulations to determine the airflow in ventilation networks, both existing and planned in the future, along with the progress of the mine operation. In the era of the development of modern technologies, new perspectives for changing the current approach to the design and optimization of ventilation networks are available. Their utilization may contribute to accuracy improvement, which can drive safety increases and process optimization. In this article, the authors evaluate the possibilities of using laser scanning data, collected with LiDAR / Terrestrial Laser Scanner, to generate 3D models of underground structures geometry, and its further utilization to conduct numerical simulations of airflow in mining excavations with Computational Fluid Dynamics. The performed analysis shows that the proposed approach may be a useful instrument for analyzing local airflow phenomena, particularly in complex ventilation networks, where disturbances in air velocity vectors are caused by sudden changes in geometry.

Закономерности аэрогазодинамических процессов при подземных пожарах

The issue was studied related to increasing occupational safety in underground mining of the mineral raw materials. The forms of the goaf are classified. An algorithm was developed for air distribution in emergency ventilation mode, including when the main ventilation fan is turned on after an emergency stop. The possibilities and mechanism of the fan influence at the stages of ventilation in emergency conditions was clarified. An algorithm is proposed for calculating ventilation parameters in case of emergency reversion of the ventilation jet. The methods for calculating the amount of air and the inertia of the ventilation system are presented at normal ventilation and during the transition from normal ventilation to emergency. The problem of air distribution during the transition period is solved with the representation of the air branch in the form of a node with multidirectional and limited movement of air jets. The methodology for predicting hazardous working situations is detailed based on the laws of diffusion transfer of gas components of the mine atmosphere. A new method of experimental determination of elements of the transitional period of ventilation was developed. The results are given concerning the study of the influence of the goaf on the efficiency of the fans operation and the duration of the transition process after reversing the fan in an emergency. A new idea is substantiated related to the gas situation as a fragment of a ventilation network with distributed sources of oxygen absorption and gas release. The structure of the matrix of the state of mine workings in an emergency was proposed. An algorithm for calculating ventilation modes for optimizing emergency response plans is formulated. It is shown that the establishment of the regularity of the processes of gas transfer during emergency ventilation mode allows to increase the efficiency of measures to ensure occupational safety in underground mining.

OPTIMISATION OF ROOM VENTILATION IN MINES WITH DIFFICULT MINING CONDITIONS

The article reviews the use of air flow barriers, air ejectors and air valves for reducing air volume losses and aerodynamic drag. Increased of scope of underground works causes proportional increase of the amount of air in the ventilation network of solders along with complication of mountain conditions. It also describes ventilation methods in difficult mining and technological conditions when ventilating mine solders, the distribution of air flows in the ventilation network by achieving optimal values of such indicators as air flow rate, pressure, change in air speed and pressure depending on the sectional surface of the solder.

Study of gas hazard pattern in underground workings after blasting

Determining the sources of hazardous and toxic substances released into mine air, their gas composition, as well as providing each such source of pollution with the required amount of fresh air are important issues in terms of ensuring normal healthy and safe working conditions for miners. This paper studies blasting as one of the most dangerous sources of mine air pollution. The study was carried out for a long dead-end exploration working, and a development (preparatory) working of a copper-nickel mine. In accordance with the federal rules and regulations (FNiP), a number of requirements, including monitoring of gas hazard at a face, is applied to blasting operations.The study examined the behavior of gas-air mixture in dead-end mine workings after blasting. The findings are based on the experimental data obtained in the conditions of two dead-end workings at an operating coppernickel mine. A technique for the experimental studies of gas release after blasting in a dead-end working was developed. The main technical characteristics of the instruments involved in the in-situ measurements are given. Time dependences of the concentrations of toxic gases after blasting at the blasted working mouth, at the return ventilation current, and near a booster were established. In order to assess the reliability of the data obtained, the volume of released carbon oxides was calculated based on the data of gas analyzers and chemical reactions of explosives decomposition during detonation, depending on the types and weights of the explosives. A model of gas-air mixture transfer was described, constructed, and calibrated allowing for longitudinal dispersion. The Voronin model was used to simulate the gradual removal of toxic gases from the working face and solving the problem of boundary conditions. Based on experimental data, the coefficients of longitudinal dispersion, ventilation efficiency, and volume concentration of the considered gas admixture in the mixing zone at initial time were determined for a long dead-end mine working.The constructed gas-dynamic model and longitudinal dispersion coefficients obtained as a result of the analysis enabled the time required for long dead-end mine workings ventilation to be analysed and estimated. Based on the model, the algorithm for calculating the velocity of spreading the combustion products in a mine ventilation network in emergency situations is being improved. The value of longitudinal dispersion coefficient for different operating conditions is also being refined.Based on the gas distribution simulation within the interval of 1,500 m from a working face, the time required for the ventilation of a dead-end mine working was determined.

A supervised diagnostic experiment of resistance variable multifault locations in a mine ventilation system

The diagnosis of resistance variable multifault location (RVMFL) in a mine ventilation system is an essential function of the mine intelligent ventilation system, which is of great significance to mine-safe production. In this paper, a supervised machine learning model based on a decision tree (DT), multilayer perceptron (MLP), and ranking support vector machine (Rank-SVM) is proposed for RVMFL diagnosis in a mine ventilation system. The feasibility of the method and the predictive performance and generalization ability of the model were verified using a tenfold cross-validation of a multifault sample set of a 10-branch T-shaped angle-joint ventilation network and a 54-branch experimental ventilation network. The reliability of the model was further verified by diagnosing the RVMFL of the experimental ventilation system. The results show that the three models, DT, MLP, and Rank-SVM, can be used for the diagnosis of RVMFL in mine ventilation systems, and the prediction performance and generalization ability of the MLP and DT models perform better than the Rank-SVM model. In the diagnosis of multifault locations of the experimental ventilation system, the diagnostic accuracy of the MLP model reached 100% and that of the DT model was 44.44%. The results confirm the MLP model outperforms the three models and can meet engineering needs.

Numerical study on the smoke movement and control in main roadway for mine fires occurred in branch

Mine exogenous fire is the main disaster in coal mines. Owing to the complicated structure and the ventilation network, the smoke movement and control in branched roadway fires of coal mines is more complicated than that in traffic tunnel fires. In this study, the smoke backlayering length and critical velocity in a main roadway for fires that occurred in a branch were studied with varying fire locations. The results suggest that the smoke from the branch does not spread along the width centerline of the main roadway, but forms an early “snake-shaped” structure. The variation of dimensionless backlayering length with the dimensionless variable ln(Q˙*1/3/V*) is divided into two regions with different slopes by the line of L* = 1.6. Besides, branched roadway fires have a lower backlayering length and critical velocity compared to single-hole tunnel fires. These two parameters increase with decreasing the fire-node distance. Combined with dimensionless analysis and simulation results, calculation models considering fire location were proposed to estimate the smoke backlayering length and critical velocity. The credibility of prediction models is validated by comparing them with simulation results. The outcomes of the current study guide smoke control in similar-structured mine roadways and traffic tunnels.

Numerical study on calculation model of airflow temperature and humidity prediction in humid airway

AbstractIn deep coal mining, the high temperature and humidity environment are one of the main disasters threatening workers and equipment. To predict the temperature and humidity of airflow in the airway accurately, this study establishes a numerical calculation model of the surrounding rock temperature, airflow temperature, and humidity under the conditions of considering the moisture evaporation and heat absorption of the airway wall, the condensation and heat release of supersaturated water vapor in the airflow, and the influence of air compression or expansion. Combined with the two‐dimensional (2D) heat conduction model (considering the influence of the axial surrounding rock heat conduction of the airway), the axial strip partial moisture calculation model of the airway is proposed, and then the uniform moist wall model and the axial strip partial moist wall model are established. The influence of different parameters on the temperature and humidity of airflow is discussed by analyzing the results of numerical simulation of the uniform wet surface model (UWSM) and partly wet surface model (PWSM) of the airway wall. The results show that the surrounding rock temperature, especially the temperature distribution of the airway wall, calculated by using the 2D heat conduction model under the local humid airway conditions, is more realistic. The increment of airflow temperature decreases with the increase of wet area ratio, airflow temperature at the entrance and airway radius, and increases with relative humidity at the entrance. The calculation accuracy of temperature and humidity prediction for large ventilation networks can be further improved by using the equivalent humidity of the UWSM to replace the correction coefficient of the wet area ratio of the PWSM.

Modeling and Complex Analysis of the Topology Parameters of Ventilation Networks When Ensuring Fire Safety While Developing Coal and Gas Deposits

Underground mining, including underground coal mining, is accompanied by accidents and fire hazards that pose a threat to the life safety of miners. The fire hazard increases with an increase in the mining depth. Currently, most accidents in coal mines are mine fires. The cost of eliminating mine fires is 80–95% of the cost of eliminating all accidents occurring at mining enterprises. Therefore, the problem of developing a new methodology for modeling the ventilation network parameters of the mine to increase the reliability of controlling the aerogas mode at the excavation site is very relevant. The comprehensive analysis and assessment of gas-dynamic processes in coalmines under study were carried out using the methods of probability theory and mathematical statistics. Spatial data were processed using spline interpolation in “gnuplot”. As a result, a generalized expression for the transfer functions of coalmine objects, taking into account delays, was developed, including the description of dynamic properties of mining sites under various operating modes. The principal possibility of using a graphical method for estimating additional parameters of the sections of the ventilation system branches has been proved due to the alignment of their profiles at an equivalent distance relative to an arbitrary analogue. The improved method of spatial modeling was used to determine the gas-dynamic characteristics through additive gas-dynamic processes. The studies have been carried out and the method for managing the process of changing connections between devices (controllers–switches) of the technical system was developed in order to obtain greater reliability for safe mining. In subsequent studies, there is an issue of more detailed clarification of the peculiarities concerning the interrelations between the studied parameters in several projections of the response space.

Mathematical Modeling of Air Distribution in Mines Considering Different Ventilation Modes

The calculation of air distribution in large mine ventilation networks is usually carried out by numerically solving a system of equations representing Kirchhoff’s circuit laws. This formulation of the problem traditionally only considers the frictional air resistance of straight sections of mine airways. However, when analyzing the changing ventilation modes, it is also important to correctly consider the shock losses, which sufficiently affect the redistribution of airflows. The reason is that the shock loss factor strongly depends on the airflow rates at the junctions of mine airways. This paper presents a mathematical model of a ventilation network that considers shock losses. The model considers steady-state air distribution as well as natural draft. The significance of the shock was confirmed with a practical example; we describe the application of the proposed mathematical model for the analysis of air distribution in the ventilation network of a potash mine during planned airflow reversal.

Research on Control Optimization Method of Mine Ventilation System Based on Intelligent Optimization Algorithm

<p>In view of the complex ventilation network in the mine, many influencing factors, and the complex establishment of the air demand model, this paper establishes an air volume optimization model with the minimum energy consumption of the entire ventilation network as the optimization objective, and adds the air volume balance law conditions, the air pressure balance law conditions, the branch air demand law conditions, the air resistance regulation law conditions, and the fan conditions as constraints to the model. Then, the intelligent algorithm is used to solve the problem. In order to make the intelligent algorithm converge faster and solve the problem optimally, the Grey Wolf algorithm is improved. Finally, the model and the improved intelligent algorithm are used to optimize the ventilation regulation of the actual operating coal mine, and the air volume control scheme is given.</p> <p> </p>

Investigation of airflow through porous zones: Integrating computational fluid dynamics modeling into mine ventilation network simulation

ABSTRACT Using mine ventilation network (MVN) software to model airflow through porous zones in underground mining operations is arduous due to its complex and dynamic nature. However, accurately measuring airflow is essential to control underground mine air quantity and quality. This study integrated the computationally expensive conjugate porous media model into versatile MVN software to efficiently analyze airflow through the porous zone. In MVN software, a novel friction factor coefficient was compiled into the broken rock-filled drawpoint model, which was later verified against the three-dimensional (3D) computational fluid dynamics model. Several simulations were conducted to ensure model reliability by varying the porosity and broken rock diameter of the porous zone. Results demonstrate that the novel friction factor coefficient can accurately predict airflow through porous media using MVN software and reduce computation time by > 99% compared to the 3D solver. In addition, sensitivity analyses were conducted to assess the effects of various factors on the system. This method enables mine ventilation engineers to effectively plan the rapidly changing underground MVN.

Analysis and modification of the ventilation network of an underground tourist mining facility in order to make new workings accessible

The attractiveness of tourist facilities is based, among other things, on the continuous expansion of their offer. In the case of the underground mining facility, this will involve making new workings available for tours. To this end, analyses were carried out on the existing ventilation network, a model of the network was made and adapted to the future situation. In order to ventilate the new excavations, a new fan station, and a large diameter borehole were designed. Phases Ia, Ib, II and III of the changes to the ventilation network with a view to opening up a new chamber are presented.

Reduction of risk of choosing the optimal ventilation mode for the period of elimination of exogenous fire

The time from the occurrence of an exogenous fire in a mine to its complete elimination can be conventionally divided into two periods: the operational time of the emergency elimination plan and the period of intensive fire extinguishing or fire cell isolation. In the first period, there is a significant number of working people in the mine, so the emergency ventilation mode must first of all ensure safe conditions for their evacuation. The issue of choosing an emergency ventilation mode in the mine ventilation network for use during the operational time of the emergency liquidation plan has been studied in sufficient detail. At the second stage of fire development, the ventilation mode should ensure the removal of combustion products by the shortest paths to the exit jet or to the workings where there are no people; to provide fresh air supply, normal temperature and minimal smoke in the areas where mining rescue works are carried out; reduce the intensity of fire development; to prevent overturning of ventilation jets in inclined workings. Among the listed requirements, there are both those that satisfy and those that contradict the criterion of the first period. Therefore, in a number of cases, during the liquidation of developed fires, it is necessary to change the ventilation mode to ensure the fulfillment of the considered conditions. A method of transition from the mode of the first period to the mode of the second is proposed, which consists in determining the list of ventilation modes that are subject to optimization. For each of them, workings are defined, in which it is possible to overturn the ventilation jet. Due to the minimization of their number, it is possible to prevent the spread of a fire zone gassed with gaseous products (that is, its minimization) and to complicate the conditions of conducting mine rescue operations. For this purpose, the theory of interrelationship of aerodynamic parameters of mine workings is used, which simplifies multi-fan ventilation calculations. The described algorithm only seems somewhat cumbersome, since it is known from practice that in the area of action of intense thermal depression of the fire cell, several loosely connected workings cannot be located far from each other, with a possible spreading of the ventilation jet. Thus, by achieving the condition of non- spreading of the ventilation jet for one of the working, it is possible to indirectly solve the problem for a number of other workings, incidental to it, which significantly reduces the complexity of the calculation process. Keywords: exogenous fire, emergency ventilation mode, thermal depression, interrelationship of aerodynamic parameters.

ФИЗИЧЕСКИЕ ПРИНЦИПЫ И МАТЕМАТИЧЕСКОЕ ОПИСАНИЕ ФОРМИРОВАНИЯ ПОЛЕЙ СКОРОСТИ ВОЗДУХА И КОНЦЕНТРАЦИЙ ГАЗОВЫХ ПРИМЕСЕЙ В ГОРНЫХ ВЫРАБОТКАХ УГОЛЬНЫХ ШАХТ

The air composition of the mine atmosphere in coal mines; Safety Rules regulate heat-humidity and speed conditions created by the ventilation system. At the same time, physic-chemical, aero-gas-dynamic and thermos-physical processes occur, which affect the level of aerological safety. A system of equations recommended that allows one to calculate longitudinal air velocity profiles at any point in the mine ventilation network. These recommended describing the transfer of gas impurities in the mine atmosphere by the equation of turbulent-convective diffusion.

EVALUATION OF THE FEASIBILITY OF INSTALLING COLLECTIVE RESPIRATORY PROTECTION EQUIPMENT IN UNDERGROUND FACILITIES

Purpose. This article substantiates the necessity and expediency of installing collective respiratory protection equipment for workers (portable emergency air supply chamber) in underground facilities (mines, mine workings of cyclic-flow technology of open-pit mining), whose activities are related to the extraction, transportation of ore and non-metallic minerals by underground method. Methodology. The study of existing means of collective respiratory protection for workers of underground facilities and a methodology for calculating the air duct capacity in accordance with the normative values of oxygen, carbon monoxide, taking into account the thermal conditions that occur during exogenous fire and operational support Results. The ventilation systems of underground facilities today, whose activities are related to the extraction and transportation of ore and non-metallic minerals underground, have been significantly transformed and represent a very complex branched, interconnected ventilation network of a large number of series, parallel and diagonally connected branches, such as horizontal, inclined, vertical workings and treatment chambers. As a result of the studies, the considered portable means of collective respiratory protection of workers can be recommended for deployment in mine workings of underground facilities, whose activities are related to the extraction, transportation of ore and non-metallic minerals by underground method. Scientific novelty. A new method assessment the air duct capacity for the installation of ex-operational backup in the portable emergency air supply chambers has been proposed. Scientific significance. This article determines the methodology for calculating the air duct capacity to establish operational backup in case of exogenous. Also, this work can be used as a practical material in the development of projects to determine the arrangement and placement of portable emergency air supply chambers in mine workings of underground facilities, as planned in the emergency response plan.

ВЛИЯНИЕ РЕЦИРКУЛЯЦИОННОГО ПРОВЕТРИВАНИЯ НА СНИЖЕНИЕ ВЫБРОСОВ ПАРНИКОВЫХ ГАЗОВ КАЛИЙНОГО РУДНИКА

The paper considers air recirculation as an event to improve energy efficiency and reduce greenhouse gas emissions by reducing the power consumption of the main ventilation fan. The results are presented based on calculations of the required amount of air and modeling of air distribution in the ventilation network of the mine in the AeroSet software package. The methodology of determining the quantitative volume of greenhouse gas emissions, followed by comparison and analysis of the data obtained, has been studied.

An Efficient Method for Optimizing Sensors’ Layout for Accurate Measurement of Underground Ventilation Networks

An Efficient Method for Optimizing Sensors’ Layout for Accurate Measurement of Underground Ventilation Networks

Reduction of the risk of selecting the emergency ventilation mode through local control of ventilation flows

The implementation of measures regarding the organization of emergency ventilation of mine is connected with various types of risks, as in other cases of the operation of high-risk enterprises. In particular, this applies to the emergency risk that arises when there is a need for the emergency evacuation of people from the mine workings, gassed with fire products (that is, the risk of their poisoning or damage due to the thermal factor) and the emergency risk that is provoked by the wrong choice and implementation of the emergency ventilation mode. Both types of risks require to reduce the use of means of ventilation - main and local ventilation fans. Provision should also be made for the use of various passive control devices. The main result of the methodological approach used today is the selection of the emergency ventilation mode, which maximally limits the gassing zone of the mine ventilation network with gaseous combustion products. At the same time, the criterion for the effectiveness of the emergency evacuation of miners should be the maximum use of non-gasified workings, which achieves the goal of managing ventilation in the event of accidents. The proposed control function, which characterizes the degree of risk of distribution of fire gases in mine workings, is the root mean square deviation of the concentration of fire gases in the controlled branches of the network from the required level of stabilization. For two control devices and two controlled areas, it is part of a three-dimensional cone, and the control region is bounded by two hyperbolas. The problem formulation looks similar when the size of the base of the regulating devices is increased . A limitation on the task is formulated, and a conclusion is made regarding the possibility of applying analog methods of dynamic programming for its solution. As such, the multi-step optimization method, the one-step optimization method, and the extreme coordinate optimization method (the last one is the most effective) are considered. The greatest efficiency of their use will be achieved with the introduction of an automated ventilation control system, which provides feedback from the means of regulation and regulatory devices. Keywords: emergency risk, aerological risk, management functionality, regulatory devices, exogenous fire.