Mine Fan Research Articles

PREDICTION OF ATMOSPHERE POLLUTION IN CASE OF EMISSIONS FROM MAIN MINE FANS

Purpose. Emissions from mine ventilation system can create intensive atmosphere air pollution. As a rule, a huge amount of dust from mine fan enters atmosphere low layers. An important task is the development of methods to assess levels of the atmosphere pollution near mines and settlements. To solve this problem it is important to have physically proved mathematical models. Nowadays to predict the atmosphere pollution near settlements which are effected by mine fan the empirical model OND–86 is used. This model does not take into account many important physical factors. So, the purpose of this study is the development of quick computing mathematical model to predict the atmosphere pollution in case of dust emissions from mine fan. Methodology. To predict levels of the atmosphere pollution in case of mine fan work 3D equation of dust convective – diffusive flow was used. This equation takes into account gravity fallout, wind velocity, atmosphere turbulent diffusion, location of dust emission source. To sole modeling equation the implicit difference scheme of splitting was used. Findings. Developed mathematical model allows quick prediction of the level of atmosphere pollution in case of dust emissions from mine ventilation fan. The models allow to obtain zones of contamination near settlements which are situated in vicinity of mine. Originality. The developed mathematical model takes into account a number of physical factors, which at the present time are not considered on the days when prediction of the atmosphere pollution in settlements near mine is carried out. Practical value. On the basis of the developed mathematical model program code was created. This code can be used for evaluation of atmosphere pollution in settlements which are effected mine fan emissions.

Radon Exposures of Miners at Small Underground Construction Sites in Old Mining: Recommendations to Improve Radiation Protection Measures by the Saxon Radiation Protection Authority.

The Ore Mountains (Erzgebirge) and Vogtland are low-mountain regions in the East German state of Saxony. Here, silver deposits were found in 1168. Mining began shortly after, continues at varying intensity to this day, and has left numerous galleries and shafts. Today, eight companies with about 250 miners carry out maintenance at more than 40 small and frequently changing underground construction sites throughout the year. Miners are protected against high radon exposure by radiation protection measures such as ventilations, stoppings made of wood, foil, and expanding foam, and staff rotations. However, some of them still show high annual exposure levels; for example, in 2015 up to 14.4 mSv measured by passive radon dosimeters. Reasons for this include the high radon potential in old mining and the natural density driven mine air current through the galleries. Mine air currents can change directions during the day depending on outdoor temperatures. This paper presents the experiences of the Saxon Radiation Protection Authority in monitoring miners in old mining. For this purpose, the paper looks at seven examples of miners’ critical exposures based on measurement curves of radon activity concentration and derives respective radiation protection measures. These encompass, for example, to activate mine fans, erect stoppings, extend ventilation pipes, and change the locations of mine fans. Conclusions are drawn for the operative and strategic radiation protection in old mining.

Fault Diagnosis of Mine Fan Bearing Based on Beetle Antennae Search

Mine fan is the lifeblood of coal mine safety production, which plays an important role in ensuring the safety of the lives of mine workers. Once it fails to operate, it will cause irreparable serious consequences. Therefore, in order to ensure the safe operation of mine fan, this paper takes the common motor bearing faults in fan faults as the object of study, proposes a method of using rough set attribute reduction combined with Beetle antennae search to optimize BP neural network to establish diagnosis model, and compares it with genetic algorithm, particle swarm optimization, imperial competition algorithm and ant lion optimization algorithm. The experimental results show that the method achieves 90% accuracy in fault diagnosis of mine fan bearing, and has faster convergence speed and shorter operation time. Compared with other optimization algorithms, the method has greater advantages. After many tests, the diagnosis results are stable, which proves that the method is feasible and effective in fault diagnosis of mine fan.

Energy efficiency overestimated by classic affinity laws: relation between volumetric flow rate and static pressure of an axial mine fan adjusted by a variable frequency driver

ABSTRACTA significant problem with operating a coal mine fan is finding ways to save energy while still maintaining the required air supply to working faces. The authors developed and tested the performance of a K45-4-№9/18.5 kW axial mine fan adjusted by a variable frequency driver set to different fractions of a typical national electric grid frequency of 50 Hz. Its volumetric flow-rate and static pressure (Q-H) data were fitted with fifth-order polynomial equations using least-squares regression. The extremes of the Q-H curves descend with decreasing frequency and differ significantly from the predictions of classic affinity laws (CAL) in fluid dynamics. The air-flow power predicted by CAL theory deviates from the baseline of the fifth-order polynomial extremes by a maximum of 48%. Interestingly, the deviation between theoretical and experimental values increases with decreasing power frequency. These results are evidence of the theoretical overestimation of energy efficiency of an AMF adjusted by a VFD.

Substantiation of Life Extension Method for Two-Stage Axial Flow Fans for Main Ventilation

The article substantiates the retrofit method for two-stage axial flow fans including an impeller and a flow straightener in each stage. In this method, the two-stage rotor is replaced by a high-rate one-stage rotor within the inlet guide vanes-impeller-flow straightener circuit. As a result, the air flow at the impeller input is uniform per standard, the operational life of the rotor bearing assembly is extended while the rotor mass is largely reduced. The procedure is developed for design and selection of aerodynamic and structural parameters of the remodel axial mine fans. The procedure takes into account the influence of the variable frequency drive and gyroscopic moment of the impeller, as well as the rigidity of the bearing assemblies and ratio of mass-inertia properties of the rotor, which allows determination of critical rotor speeds at early stage of design.

Geothermal Properties of Fan Yaghnab Coal Deposit

The Republic of Tajikistan has a mountainous geography with over than 93% of its territory covered by mountains belonging to the highest mountain ranges - Pamir and Tian Shan. As a result of extensive geological explorations, more than 600 oil and gas fields and over 50 types of mineral raw materials sources such as coal, lead, zinc, copper, bismuth, antimony, mercury, precious and semiprecious metals, iron, tungsten, molybdenum, strontium,fluorspar, borates, ornamental and building materials, thermal and mineral water sources have been explored and surveyed.The coal deposit of Fan Yaghnab is the largest in the Republic of Tajikistan and one of the largest in Central Asia. The area of the deposit is about 102 km2. It spreads northwest in a narrow strip form with a length of 24 km and width of 4.5-6 km, and conventionally is divided into 3 parts: The Western, Central and Eastern fields. Administratively, the area of the coal mine Fan Yaghnab belongs to the Ayni district of Khujand region of Tajikistan. It is located on the southern slope of the Zarafshan and the northern slope of the Hisar Ranges in the confluence of the Yaghnab, Iskandar-darya, and Pasrud-darya rivers [1-3].Tajikistan has more than 4.4 billion tons of potential coal reserves, of which 320.3 million tons are industrial reserves with high-calorie content (Fig. 1). Along with a large reserve of coking coal (259 850 thousand tons) and heat coals (136160 thousand tons) at the Fan Yaghnab deposit, there are geothermal zones formed by the burning of coal stratum for over 500 years. The underground combustion of coal (Figure 2) at the Fan-Yaghnab deposit in Tajikistan is also mentioned by the famous Roman writer-encyclopedist Pliny the Elder, who lived in the first century of our era [2].

Increase of energy efficiency of mine fans work on a mine vent network

The increase of energy efficiency of main fans (MF) work is the basic condition of perfecting the mine ventilation system. During realization of multi-fan ventilation there is the non-productive «overbalancing» of vent flow from a weaker towards more powerful ventilator which causes decline of work efficiency of both. The questions of reducing the MF mutual influence on the outgoing air flow and increasing the aerodynamic quality of vent network have been studied and considered insufficiently. It is proposed to use the method of calculating the effective MF operating conditions taking into account the mutual influence of MF and areas-users of fresh air in mine ventilation network and on the basis of criterion of estimating the MF mutual influence, which will allow to enhance the energy efficiency of mine ventilation and labour safety of subsurface miners.

Creation of the Information System Based on Experimental Data for Control of the MMF Operating Modes to Improve the Efficiency of Ventilation in Mines

The paper presents the results of two experiments conducted using the main mine fan in BKPRU-2 mine (PJSC Uralkali, Russia). The obtained data processing showed that a statistical verification of the measured data on their falsity and independence should be performed to effectively control the ventilation process. The mathematical dependences are provided for calculating the total natural draft during measurements, which significantly affects the ventilation process. This enables the control of ventilation in mines.

Influence of Geometric Characteristics of the Flow Pass of Axial Fan on the Pressure Difference Created by It

This scientific paper describes numerical and experimental investigation of the influence produced by a shape of the flow pass of axial fan on the level of created pressure difference. Conical, cylindrical, cylindrical and conical, sphero-conical and other types of the shape of flow pass were investigated. Ultimate values of the levels of created pressure difference were defined provided that a high efficiency factor was retained for axial mine fans designed for the local ventilation of a full scale production. Recommendations on the use of some types of shapes of the flow pass for big axial fans of a high capacity were given to reduce specific quantity of metal and increase the efficiency in a wide range of operation modes. Investigation of the flow pass of the fan designed for the main local ventilation carried out using the 3D flow simulation and the experimental check showed an apparent advantage of the fan with the taper sleeve (flow pass with the meridional flow acceleration) in comparison with cylindrical meridional by-passes used at the present time. A total maximum pressure increment was 20 to 25 % and the maximum output increment was 20 to 30 %. First of all, this is related to a convergent behavior of the flow stream in the meridional plane, which results in a decrease of the influence of separated flows.

Factors defining value and direction of thermal pressure between the mine shafts and impact of the general mine natural draught on ventilation process of underground mining companies

The article specifies measuring data of air parameters and its volume flow in the shafts and on the surface, collected in BKPRU-2 (Berezniki potash plant and mine 2) («Uralkali» PJSC) in normal operation mode, after shutdown of the main mine fan (GVU) and within several hours. As a result of the test it has been established that thermal pressure between the mine shafts is active continuously regardless of the GVU operation mode or other draught sources. Also it has been discovered that depth of the mine shafts has no impact on thermal pressure value. By the same difference of shaft elevation marks and parameters of outer air between the shafts, by their different depth, thermal pressure of the same value will be active. Value of the general mine natural draught defined as an algebraic sum of thermal pressure values between the shafts depends only on the difference of temperature and pressure of outer air and air in the shaft bottoms on condition of shutdown of the air handling system (unit-heaters, air conditioning systems).

FEATURES OF DRILLING-AND-BLASTING AT CONSTRUCTION OF BESKIDSKIY TUNNEL

Purpose. In this article it is necessary to analyze the possibility of developing technology and increasing its efficiency during the Beskidskiy tunnel construction in difficult engineering and geological conditions. Methodology. The authors have performed analysis of the technological level of mining and construction works, new technique, equipment and production. One of the important issues of blasting operation is to ensure the seismic safety, acting at a distance of 30 m in the axes of single-track tunnel, as the distance to it will be 20 m from the nearest charge in the laying tunnel. This problem was solved by applying the combined blasting of blast-hole charges with delay-action and long-delay ways. Herewith the total mass of charges in the stope was divided into three groups, in which the first group is exploded by short-delay firing with, and the second one is exploded by short-delay firing too with intervals of 200…400 ms, the third is exploded by long-delay blasting at intervals of 500…10000 ms. The combined blasting of short-delay charges and delay action ones let significantly reduce seismic action at a mass explosion of charges when driving of double-track railway tunnel of a large cross-section. Findings. The paper presents the developed technology model, describing dependence of the machines from engineering and geological conditions. The methodology of drilling and blasting works at the construction of the tunnel callote and stross as well as a technique of arrangement determination and intervals of shot-delay and delay blasting of blasthole explosive charges was developed. Maximum permissible concentration of gases and vapours at blasting was presented. The calculations showed that the maximum level of gas contamination of the working area in Beskidskiy tunnel is achieved at blast operations. In accordance with this ventilation of the tunnel when driving is carried out by independent systems with mechanical ventilation by blowing using mine fans of special mining enterprises. Originality. The developed seismically safety charge masses are based on the well-known state about antiseismic blasting regulations. Practical value. The authors proposed and grounded the efficient technology for reduction to practice of drilling and blasting works (with dividing of the tunnel cross-section into the calotte and stross during of the Beskydy high-mountain tunnel construction. The results of technological experiment are presented.

RETRACTED: Reducing ventilation air methane emissions cost-effectively and safely

Greenhouse gas mitigation using traditional methods such as wind farms and solar panels is very expensive, and because of this it is meeting stiff public resistance; however, some mitigation is possible at a far lower cost by targeting ventilation air methane fugitive emissions from collieries. Methane (CH4) has been controlled in collieries in the past only for safety and statutory compliance reasons but possible or actual government regulation of greenhouse gas emissions mean that it is becoming desirable to quantify the amount of ventilation air methane available for mitigation and the associated cost of this. The machinery to mitigate these fugitive emissions once the CH4 exits the mine fans is expensive, has safety concerns and is not widely used at present. One solution would be a method to prevent more CH4 from entering the mine airstream and becoming ventilation air methane in the first place. Recently, at a colliery in the Hunter Valley, Australia, this mitigation method underwent a 12-month tria...

Mitigating Ventilation Air Methane Cost-Effectively from a Colliery in Australia

Abstract Methane has been controlled in collieries in the past only for safety and statutory compliance reasons; however concerns over greenhouse gas emissions mean that this is now changing. About 65% of greenhouse emissions associated with underground coal mining come from ventilation air methane (VAM). The machinery to mitigate these fugitive emissions once the VAM exits the mine fans is expensive, has safety concerns and is not widely used at present. Consider these factors; more collieries are mining lower seams, methane content increases with depth, VAM mitigation plants are not widely used, most mine emissions are VAM, and widespread concern over greenhouse gases mean that it is desirable to lower VAM emissions now. One solution would be a method to prevent more methane from entering the mine airstream and becoming VAM in the first place. Recently, in a colliery in the Hunter Valley, this mitigation method underwent a 12-month trial, and involved six different measures. Measurements were taken to assess the emissions mitigation which was achieved, and the cost of the works; all the results are detailed herein. A reduction in fugitive emissions of 80,307 t/CO2-e below that which was projected for the next 12-month period was quantified, at an average cost of A$1.28c t/CO2-e. The mitigation measure outlined here represent a first attempt to the author’s knowledge, in an operating mine, to lower a collieries’ environmental footprint by preventing methane from entering the mine airstream and becoming VAM gas by the deliberate use of mitigation measures.

Calculating bending vibrations of main axial mine fan rotor shaft

The article presents a calculation procedure for critical rotary speed of an axial main mine fan rotor. The calculations are made for fan model VO-21. The suppositions that make the calculations simpler without considerable errors of the results are evaluated. The calculations use the finite element method and ANSYS software. The critical rotary speeds are determined from the Campbell diagrams plotted for the estimates with and without regard for the stiffness of the bearing assemblies of the rotor. The effect exerted by the rotor bearing assembly stiffness and by the gyroscopic moment of the fan impeller on the frequency of free bending vibrations of the rotor shaft under direct and back precession is illustrated. The estimated critical rotary speeds are compared with the analytical data obtained based on discrete two-mass models. For the preliminary engineering estimation, it is possible to use a discrete two-mass model of the fan rotor without regard for the yielding of the bearing assemblies and for the influence of the gyroscopic model; in the design model, it is required to replace the transmission shaft by the point mass. The calculation error will not exceed 7%.

Fault Diagnosis Research for Mine Fan Based on the CFD

In this paper, a new fault diagnosis method is proposed based on CFD technology in order to research the fault mechanism of mine axial fan. The method combined RANS equation and Realizable k-turbulence model realizes the three dimensional aerodynamic performance analysis of the fan impeller. Three-dimensional impeller model of axial fan was set up in three conditions which including normal, crack and blade loose, and comparing the turbulence characteristic of the three models. The research provides the theoretical basis for the fault mechanism of blade failure, and it has important reference value for fault diagnosis method based on CFD of mine axial fan.

Improving the energy efficiency of mine fan assemblages

Energy associated with ventilating an underground operation comprises a significant portion of a mine operation's base energy demand and is consequently responsible for a large percentage of the total operating costs. Ventilation systems may account from 25 to 40% of the total energy costs and 40–50% of the energy consumption of a mine operation. Fans are the most important mechanical devices used to ventilate underground mines and the total fan power installed in a single mine operation can easily exceed 10,000 kW. Investigations of a number of mine main fan installations have determined their assemblage to be, in general, very energy inefficient. The author has found that 40–80% of the energy consumed by a main fan is used to overcome the resistance of fan assemblage components. This paper presents how engineering design principles can be applied to improve the performance and efficiency of fan installations, resulting in substantial reductions in power consumption, operating cost and greenhouse gas emissions. A detailed case study is presented to demonstrate that, by designing fan assemblages using proper engineering concepts of fluid physics and industrial ventilation design, main fan systems will operate at efficiencies well above 80–90% (compared to common operating efficiencies of between 20 and 65%), resulting in a drastic reduction in a mine's overall costs and base electrical and energy loads.

Natural draft and its direction in a mine at the preset confidence coefficient

The article describes evaluation of natural draft (thermal drop of ventilation pressure) and determination of its direction in a mine. The measurements taken on main mine fan are processed based on the methods of mathematical statistics. The results allow evaluating the natural mine draft at the preset confidence coefficient, and the offered algorithm enables on-line control of mine ventilation.

Motor soft starters in electric drives used in mining machinery

This paper analyzes the selection of the type of a starter for electric drives with high-voltage synchronous motors depending on the nature of the change in the load torque of the mechanism, the amount of driving synchronous motors to be started up (single motor or successive start of several motors), and the technological regime requirements, as well as the parameters of the synchronous motor. Single-line schemes of implementing the soft starters of driving high-voltage synchronous motors of large grinding machines and axial mine fans for main and auxiliary ventilation are given.

Adaptation of main mine fan aerodynamics to vent mode changes

The authors illustrate efficient adaptability of aerodynamic characteristics of main mine fans to changes in mine vent modes in the course of mine’s operating life by using fan impellers with replaceable sheet blades of different aerodynamic configurations.

Energy-saving mine ventilation

The authors show three methods of energy saving in mine ventilation: recirculating airing, minimization of main mine fan pressure by privative adjustment, and two-parameter optimization of fan performance (by rotary velocity and angle of blades). Energy saving using any of the methods is illustrated in the article.