Mine Ventilation Network Research Articles

Estimation and use materials of the airily-depressed surveys on the coal mines of Ukraine

Need to improve the methodological and technical means of obtaining, adjusting and updating the results of the airly-depressed surveys (ADS). With this purpose, identified issues that do not respond modern tasks of the ADS concerning the control of the aerological condition of coal mines. Methods of structural and parametric identification of the mine ventilation network are developed. It is proposed to replace obsolete control devices of aerodynamic parameters more modern, developed by Institute of Geotechnical Mechanics named by N. Poljakov of National Academy of Sciences of Ukraine, devices: anemometer portable mine APR-2, micromanometer differential mine MDR-6, the converter difference of pressure PRD-1. It is proposed a new approach to actualization of information, consisting in the joint of measurements by stationary and portable control devices. Methods of structural-parametric identification and measuring instruments of the aerodynamic parameters of a new technical level offered for the first time. Use of the proposed methods and technical means processing the results of the ADS will improve the quality of aerodynamic information received.

Safe and energy-efficient ventilation in mines – application of the golden ratio method in designing forced air distribution for ventilation networks

Mine ventilation networks are often designed with branches with dependent air currents. Among these, branches connecting the subnetworks of main ventilation fans may be distinguished. Their presence in the ventilation network allows to obtain an infinite number of air distribution variants fulfilling the imposed requirements of distribution. The distributions differ not only in terms of air flow rate in branches, but also in terms of main fan parameters, including their effective power. From the point of view of energy savings, it is beneficial to find such air distribution in which the effective power of the fans exhibits the lowest value.The paper presents an algorithm based on the golden ratio method, allowing to find the optimal air distribution with a certain degree of precision. The presented algorithm is applicable in all ventilation networks with two main fans with interconnected subnetworks.The paper includes an example of a ventilation network in which the method in concern was applied. The effective power of the fans in the network referred to above in the less advantageous scenario amounted to 379.5 kW, while after the optimization, an air distribution variant was found in which the power was limited to 149 kW.

Searching for dependent air currents in a mine ventilation network using the connected graph disconnection method

Ventilation networks in underground hard coal and copper ore mines are usually designed with branches with dependent air currents. Among these, branches connecting sub-networks of main fans may be distinguished. In view of ventilation hazards: fire hazard, gas hazard, thermal hazard and coal dust explosion hazard, the presence of dependent air-currents may be both desirable and adverse. Information regarding the possible presence and character of the dependent air currents in the mining plant’s ventilation network is thus significant.The paper presents a method, based on graph theory, allowing to determine the presence of dependent air currents and their affiliation with the supplied (fresh) air or the removed (used) air. This allows to obtain information whether air currents connecting the main fan sub-networks exist in a ventilation network. The method is applicable in all ventilation networks under the condition of the previous reduction of parallel connections.The paper presents an example of a ventilation network with three main fans, where the method in concern was applied. The algorithm presented in the article allowed to determine the existence of dependent currents in each of the air zones. Additionally, it allowed to identify the main ventilator sub-networks that are interconnected.

Application of VENTSIM 3D and mathematical programming to optimize underground mine ventilation network: A case study

Ventilation is a vital component of an underground mining operation, used to guarantee a safe atmosphere for workers and survive them from the hazardous and toxic gases. In the recent years, engineers have begun to apply new operation research techniques in order to optimize the ventilation systems to assist in achieving a regulatory compliance, reduce ventilation costs, and improve its efficiency. Airflow regulation optimization in mine ventilation networks is described as a minimization model whose objective function is a minimum number of regulators and energy consumption. In this work, all the previously accomplished works were first reviewed. Then a ventilation system was designed for the Western-Razmja coal mine by a manual method, and an axial fan was proposed. Subsequently, the same ventilation system was simulated using the VENTSIM 3D software. The results obtained by computer simulation showed that there was a reliable relation between the manual method and the simulation approach. In the final step, the GAMS software was used to solve a Mathematical Programming (MP) problem to minimize the overall cost of ventilation by determination of the optimum location for the fan and regulators. The final results of this work illustrated that not only the number of regulators were reduced through solving the MP model but also the total resistance of the Western-Razmja coal mine was reduced by 14% from 1.6 to 1.3. Furthermore, it was observed that the total efficiency of the proposed fan was increased.

Automation in detection of recirculation in a booster fan ventilation network

Recirculation is prohibited in many coal mining countries because of the fear that the re-use of return air would allow the build-up of air contaminants at the workings. The incorrect design and location of a booster fan in any ventilation network can create unsafe condition due to recirculation. The current approach to investigating recirculation using simulation software requires manual effort which becomes tedious in a complex and a large network. An algorithm-based C++ program was designed to detect the recirculation in a booster fan ventilation networks. This program needed an input file prepared from output file generated by any ventilation simulator. This program created an output file for recirculation. This program demonstrated the strong capability to detect the recirculation in a sample network and a coal mine ventilation network. The outcomes of this program were documented in this paper.

Evaluating complex mine ventilation operational changes through simulations

Increasing the profitability of the mining industry is contingent on its ability to improve operational efficiency. Mine ventilation networks typically represent 25-50% of a mine’s energy consumption and, therefore, exhibits scope for optimisation. Ventilation networks comprise numerous complex integrated airways, branches and ventilation fans. The most effective way to optimise and evaluate them is computer-aided simulations. However, no framework exists to clarify exactly how operational changes in ventilation networks should be evaluated. In this study, a scalable method was developed, implemented and analysed. The case study validation resulted in satisfying key performance indicators of both service delivery and operational energy costs, thereby increasing operational efficiency. The significance of the novel method is that it allows for improved operational decisions on mine ventilation networks. The value of the method was illustrated by the adoption of the method by the case study mining personnel to form the new norm of their procedures and standards.

Mine Ventilation Network Optimization Based on Airflow Asymptotic Calculation Method

The main objective of mine ventilation network optimization studies is to develop a reasonable method for ventilation system control that minimizes the total cost of mine ventilation. The fundamental principles for ventilation network optimization are discussed, and a multi-objective optimization model is established from the viewpoint of total cost. Furthermore, an optimization algorithm based on the airflow asymptotic calculation is presented by the hierarchical analysis of objective functions and analysis of the structure characteristics of a ventilation network. In the proposed approach, the regulated branches are determined by the directed path matrix; the optimal solution is obtained by airflow asymptotic calculation using the existing software for ventilation network analysis, and it does not need to solve the large-scale nonlinear programming problem. The results of example analysis validated the reliability of this approach.

Research on the HPACA Algorithm to Solve Alternative Covering Location Model for Methane Sensors

The current safety regulations and its correlative specifications of the coal industry ignore the problem of malfunction. To solve the issue completely, an optimized location model based on the methane sensor is proposed in this paper. The proposed model is not only economic but also reliable for a sensor of methane. In the procedure of establishing the optimized model, this paper selects the nodes of mine ventilation network as candidates, and the points specified by Mine regulations and specifications. A three-stage hybrid Pareto ant colony algorithm (HPACA) based on the column reduction, tabu search (TS) and Pareto ant colony algorithm (HPACA) is also designed. Finally, practical application of the proposed model is displayed with an example of the mine ventilation network.The computation results show that the HPACA algorithm can achieve the optimal solution or the approximate optimal solution of the location model quickly and effectively.

Calibration of Mine Ventilation Network Models Using the Non-Linear Optimization Algorithm

Effective ventilation planning is vital to underground mining. To ensure stable operation of the ventilation system and to avoid airflow disorder, mine ventilation network (MVN) models have been widely used in simulating and optimizing the mine ventilation system. However, one of the challenges for MVN model simulation is that the simulated airflow distribution results do not match the measured data. To solve this problem, a simple and effective calibration method is proposed based on the non-linear optimization algorithm. The calibrated model not only makes simulated airflow distribution results in accordance with the on-site measured data, but also controls the errors of other parameters within a minimum range. The proposed method was then applied to calibrate an MVN model in a real case, which is built based on ventilation survey results and Ventsim software. Finally, airflow simulation experiments are carried out respectively using data before and after calibration, whose results were compared and analyzed. This showed that the simulated airflows in the calibrated model agreed much better to the ventilation survey data, which verifies the effectiveness of calibrating method.

Airflow Sensitivity Assessment Based on Underground Mine Ventilation Systems Modeling

This paper presents a method for determining the sensitivity of the main air flow directions in ventilation subnetworks to changes in aerodynamic resistance and air density in mine workings. The authors have developed formulae for determining the sensitivity of the main subnetwork air flows by establishing the degree of dependency of the air volume stream in a given working on the variations in resistance or air density of other workings of the network. They have been implemented in the Ventgraph mine ventilation network simulator. This software, widely used in Polish collieries, provides an extended possibility to predict the process of ventilation, air distribution and, in the case of underground fire, the spread of combustion gasses. The new method facilitates an assessment by mine ventilation services of the stability of ventilation systems in exploitation areas and determines the sensitivity of the main subnetwork air flow directions to changes in aerodynamic resistance and air density. Recently in some Polish collieries new longwalls are developed in seams located deeper than the bottom of the intake shaft. Such a solution is called “exploitation below the level of access” or “sublevel”. The new approach may be applied to such developments to assess the potential of changes in direction and air flow rates. In addition, an interpretation of the developed sensitivity indicator is presented. While analyzing air distributions for sublevel exploitation, the application of current numerical models for calculations of the distribution results in tangible benefits, such as the evaluation of the safety or risk levels for such exploitation. Application of the Ventgraph computer program, and particularly the module POŻAR (fire) with the newly developed options, allows for an additional approach to the sensitivity indicator in evaluating air flow safety levels for the risks present during exploitation below the level of the intake shaft. The analyses performed and examples presented enabled useful conclusions for mining practice to be drawn.

A transient model for airflow stabilization induced by gas accumulations in a mine ventilation network

To analyze the airflow stabilization induced by gas accumulations in a mine ventilation network, a transient model for airflow caused by gas accumulations is presented. The Runge Kutta method is selected to solve this model. To quantify the average gas density in the transient model, a solution to the gas diffusion equation in airways is interpreted. The Crank-Nicholson difference method is applied to calculate the gas diffusion equation, and the chase method is selected to calculate the gas concentration distribution in airways. Furthermore, a coupled solution between the transient model and the gas diffusion equation is proposed, and a transient airflow ventilation network program for this coupled solution is developed. According to the simulations conducted in this work, it is concluded that the results agree well with the field test. Finally, it was found that gas accumulation in inclined airways can generate gas ventilation pressure, which can lead to airflow disorder.

Experimental study on f-ω regulation model under abnormal methane emission

In view of the difficulty of automatic adjustment, the recovery lag and the major accident potential of the mine ventilation system, an experimental model of the pipe net was established according to the typical one mine and one working face ventilation system of Daliuta coal mine. Using the best uniform approximation method of Chebyshev interpolation to fit the fan performance curve, we experimentally determined fan characteristics with different frequencies and establish the data base for the curves. Based on ventilation network monitoring theory, we designed a monitoring system for ventilation network parameter monitoring and fan operating frequency automatic control. Using the absolute methane emission quantity to predict the air quantity requirement of branch and fan frequency, we established a f-ω regulation model based on fan frequency and absolute methane emission quantity. After analysing methane emission and distribution characteristics, using CO2 to simulate the methane emission characteristics from a working face, we verified the correctness and rationality of the f-ω regulation model. The fan operation frequency is adjusted by the method of air adjustment change with methane emission quantity and the curve searching method after determining air quantity requirements. The results show that the air quantity in a branch strictly changes according to the f-ω regulation model, in the air-increasing dilution by fan frequency regulation, the CO2 concentration is limited to the set threshold value. The paper verifies the practicability of a frequency regulation system and the feasibility of the frequency adjustment scheme and provides guidance for the construction of automatic frequency conversion control system in coal mine ventilation networks.

New improvements to MFIRE to enhance fire-modeling capabilities

NIOSH's mine fire simulation program, MFIRE, is widely accepted as a standard for assessing and predicting the impact of a fire on the mine ventilation system and the spread of fire contaminants in coal and metal/nonmetal mines, which has been used by U.S. and international companies to simulate fires for planning and response purposes. MFIRE is a dynamic, transient-state, mine ventilation network simulation program that performs normal planning calculations. It can also be used to analyze ventilation networks under thermal and mechanical influence such as changes in ventilation parameters, external influences such as changes in temperature, and internal influences such as a fire. The program output can be used to analyze the effects of these influences on the ventilation system. Since its original development by Michigan Technological University for the Bureau of Mines in the 1970s, several updates have been released over the years. In 2012, NIOSH completed a major redesign and restructuring of the program with the release of MFIRE 3.0. MFIRE's outdated FORTRAN programming language was replaced with an object-oriented C++ language and packaged into a dynamic link library (DLL). However, the MFIRE 3.0 release made no attempt to change or improve the fire modeling algorithms inherited from its previous version, MFIRE 2.20. This paper reports on improvements that have been made to the fire modeling capabilities of MFIRE 3.0 since its release. These improvements include the addition of fire source models of the t-squared fire and heat release rate curve data file, the addition of a moving fire source for conveyor belt fire simulations, improvement of the fire location algorithm, and the identification and prediction of smoke rollback phenomena. All the improvements discussed in this paper will be termed as MFIRE 3.1 and released by NIOSH in the near future.

Modeling carbon monoxide spread in underground mine fires

Carbon monoxide (CO) poisoning is a leading cause of mine fire fatalities in underground mines. To reduce the hazard of CO poisoning in underground mines, it is important to accurately predict the spread of CO in underground mine entries when a fire occurs. This paper presents a study on modeling CO spread in underground mine fires using both the Fire Dynamics Simulator (FDS) and the MFIRE programs. The FDS model simulating part of the mine ventilation network was calibrated using CO concentration data from full-scale mine fire tests. The model was then used to investigate the effect of airflow leakage on CO concentration reduction in the mine entries. The inflow of fresh air at the leakage location was found to cause significant CO reduction. MFIRE simulation was conducted to predict the CO spread in the entire mine ventilation network using both a constant heat release rate and a dynamic fire source created from FDS. The results from both FDS and MFIRE simulations are compared and the implications of the improved MFIRE capability are discussed.

A Comparative Study of the Iterative Numerical Methods Used in Mine Ventilation Networks

Ventilation is one of the key safety tasks in underground mines. Determination of the airflow through mine openings and ducts is complex and often requires the application of numerical analysis. The governing equations used in the computation of mine ventilation are discussed in matrix forms. The aim of this paper is to compare the most frequently used numerical analysis methods, which includes Newton-Raphson and the Linear Theory. It is the challenge of this study to investigate the influence of the initial flow rates and the fans in the network. A simulated mine ventilation network is represented in order to examine the two numerical methods. The numerical results acquired from Newton-Raphson method exhibited faster rate of convergence in comparison to those of the Linear Theory method. The mine ventilation networks are less expanded, therefore, the Newton-Raphson method converges faster. On the other hand, when using computational tools and software the advantage of faster convergence becomes less important, and therefore the Linear Theory method will be more preferred

ASSESSMENT OF MINE VENTILATION SYSTEM RELIABILITY USING RANDOM SIMULATION METHOD

A mine ventilation system provides a fresh air flow to the underground workings in a coal mine. Such sufficient air volume can dilute and remove noxious gases (typically NOx, SO2, CH4, CO2 and CO) and maintain a suitable working environment for coal miners. On the other hand, a poor ventilation system often leads to serious consequences such as mine gas explosions, production loss or higher operational costs. Hence, the functions of mine ventilation system are very important for an underground mining system. This paper presents a reliability assessment approach for evaluating the mine ventilation system based on a random simulation method, Monte-Carlo Simulation (MCS). In detail, the first step of this method is to finish probabilistic descriptions of the mine ventilation network. Then, the criteria of successful conditions are defined. Finally, the Monte-Carlo Simulation (MCS) method is used for performing the reliability assessment. By using this assessment approach, the random characteristics in the system can be well considered. Hence, the results are more accurate and reliable. In addition, the risk evaluation for the mine main fan is also approached by the Monte-Carlo Simulation (MCS) method. Two important problems, the yearly percentage of loss time due to fan repairing and yearly breakdown times, are answered. Through the paper, a case study has been shown and investigated to demonstrate the assessment procedure for a mine ventilation system with using the MCS method.

Alternate solutions for mine ventilation network to keep a pre-assigned fixed quantity in a working place

In underground constructions, a good ventilation design not only delivers fresh air to establish good working environment, but also provides a scientific and reliable basis to prevent disasters. In emergency cases, unexpected closure of the main airways may occur, providing the workers with alternative airways is substantial. This is important not only to sustain personnel lives, but also to prevent the mine ventilation system from damage. In this research, alternate solutions were introduced in case of failure in the underground construction to keep a pre-assigned fixed quantity in a working place for mine ventilation network. Eight different collapse scenarios were proposed to study their effect on the air quantity distribution among the branches in the ventilation circuit. From these scenarios, it is found that providing a sufficient air quantity in the working places could be achieved through modification of the network topology and adjusting the values of the regulators pressure. It is also indicated that the distance between the collapse and working places has a great effect on the amount of air delivered to it. A reduction in the power consumption could be done by re-arrange the installed regulators and decreasing the number of nodes and branches inside the network. A relationship representing the effect of changing the network topology on the total network power consumption was deduced through regression analysis. It is found that the total network power is quadratic dependent on the number of regulators and number of branches while it is directly dependent on the regulator power.

Effective utilization of tracer gas in characterization of underground mine ventilation networks

Tracer gases are an effective method for assessing mine ventilation systems, especially when other techniques are impractical. Based on previously completed laboratory and field experiments, this paper discusses some common and challenging issues encountered when using tracer gases in underground mines. The discussion includes tracer release methods, sampling and analysis techniques. Additionally, the use of CFD to optimize the design of tracer gas experiments is also presented. Finally, guidelines and recommendations are provided on the use of tracer gases in the characterization of underground mine ventilation networks. This work has informed the practical use of tracer gases in mines, and this body of knowledge is expected to contribute to more efficient and more common use of tracer gases by mine engineers, which will allow for better characterization of mine ventilation system and improved safety. The findings can also be used when using the tracer gas technique in the evaluation of atmospheric environment and air quality investigation in buildings.

A Study on Preventing Spontaneous Combustion of Residual Coal in a Coal Mine Goaf

The effectiveness of grouting scheme has been simulated to prevent the coal spontaneous combustion at a goaf in Haizi Colliery, China. The colliery has been operated for long period over 27 years and has a complex ventilation network including airflow leakages which could possibly lead to the spontaneous combustion of coal at goafs. Firstly, the mine ventilation simulator MIVENA was used to analyze the mine ventilation network airflows to control airflows in and out of working faces and goafs. As the second approach, numerical simulations were carried by the simulator FLUENT in order to predict spontaneous combustion of residual coal with leakage flow in the #3205 goaf. It was cleared that the goaf can be divided into three zones based on oxygen concentration in the goaf area. Finally, the numerical simulation results show that the slurry grouting method is able to be an effective and economical method by reducing porosity in the goaf area to prevent spontaneous combustion of residual coal.

A Reliable Method of Completing and Compensating the Results of Measurements of Flow Parameters in a Network of Headings / O Pewnej Metodzie Uzupełniania I Wyrównywania Wyników Pomiarów Parametrów Przepływu W Sieci Wyrobisk Górniczych

Abstract Forecasting a ventilation process is based on two factors: using a validated software (Dziurzyński et al., 2011; Pritchard, 2010) and a properly prepared database encompassing the parameters describing the flow of air and gases, compatible with the adopted mathematical model of the VentGraph software (Dziurzyński, 2002). With a body of measurement data and a mathematical model for computer calculations and air flow simulation at our disposal, we proceed to develop a numerical model for a chosen network of mine headings. Preparing a numerical model of a ventilation network of a given mine requires providing a collection of data regarding the structure of the network and the physical properties of its elements, such as headings, fans, or stoppings. In the case of fire simulations, it is also necessary to specify the parameters describing the seat of a fire and the properties of the rocks of which the rock mass is comprised. The methods which are currently applied to this task involve manual ventilation measurements performed in headings; the results obtained in the course of these measurements constitute a basis for determining physical parameters, such as the aerodynamic resistance of a heading, density of the flow of air, or natural depression. Experience shows that - due to difficulties regarding accessibility of headings, as well as the considerable lengths of the latter - there are some nodes and headings in mines where such measurements are not performed. Thus, an attempt was made to develop a new methodology that would provide the missing data on the basis of some other available information concerning - for example - the air density, the geometry of headings and elevations. The adopted methodology suggests that one should start with balancing the air mass fluxes within the structure of a network of headings. The next step is to compile a database concerning the pressure values in the network nodes, based on the measurement results - and provide the missing pressure values on the basis of the available results of measurements carried out in adjacent nodes, as well as the pressure value calculated on the basis of the heading geometry and the given volumetric flow rate. The present paper discusses the methodology of compensating and balancing the volumetric air flow rates within a network of headings (Chapter 2) and the methodology of determining pressure values (Chapter 3) in the nodes of the network. The developed calculation algorithms - verified by means of sample calculations performed for a selected area of a mine ventilation network - were introduced into the VentGraph software system. The calculation results were presented in tabular form. The Summary section discusses the minuses and pluses of the adopted methodology.