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Mine ventilation and air conditioning
Abstract
This book presents a comprehensive treatment of mine ventilation in terms of theory and practice. Chapter headings are; control of the mine atmosphere; regulations related to mine ventilation; mine gases; methane drainage; mine dusts; flow of air through mine openings and ducts; basic mine ventilation circuits; instrumentation and air measurements; natural ventilation; mechanical ventilation equipment; ventilation of mines by fans; auxiliary ventilation; economics of airflow; metal mine ventilation; coal mine ventilation; tunnel ventilation; ventilation network theory; application of computers to ventilation; mine fires and explosions; heat in mines; psychrometry, refrigeration, and heat transfer processes; and mine air conditioning systems. Appendices contain reference tables dealing with shock losses, friction losses, and air-water vapor mixtures, a description of the international System of Units, a computer program for mine ventilation network analysis, and answers to the engineering problems found at the end of each chapter. Individual abstracts were prepared for each chapter. 524 references. (CKK)
... Stationary and moving heat sources are also necessary in understanding and modeling the heat and humidity transport. The potential heat sources in an underground mine are [4]: @BULLET Auto-compression @BULLET Strata heat (geothermal gradient) @BULLET Underground water @BULLET Machinery @BULLET Human metabolism @BULLET Oxidation @BULLET Blasting @BULLET Rock movement @BULLET Pipelines It was once understood that this was also the order of importance of the heat sources; however, recent studies have shown that each mine is unique in its heat source distribution [4][5][6]. Table 1shows the heat load distributions for mines in Canada, Australia, and the US. The relative contributions of the major heat sources are affected by several factors including: @BULLET Depth of the mine @BULLET Level of mechanization @BULLET Mine power sources @BULLET Geothermal activity @BULLET Rock thermal properties, etc. ...
... The heat removal capacity of the air can be calculated using psychrometric equations and the heat load is determined as discussed in section 3.1. The ability of ventilation systems to effectively cool the air decreases at a depth of about 3,300 ft (1000 m) [5]. Below this depth, use of localized cooling methods and refrigeration might be necessary for heat removal from the active areas of the mine. ...
... Therefore, a comprehensive strategy of monitoring for field data collection would be critical to employ an accurate climatic model. Furthermore, studies show that hourly, daily and seasonal temperature changes can produce significant 3odeling errors [5, 7]. Kocsis et al [5] highlighted that the difference between simulated and measured climatic parameters is the result of the dynamic time delay of temperature and humidity spikes along the advection pathways of the ventilating air due to the " thermal flywheel effect " (TFE). ...
... Stationary and moving heat sources are also necessary in understanding and modeling the heat and humidity transport. The potential heat sources in an underground mine are [4]: @BULLET Auto-compression @BULLET Strata heat (geothermal gradient) @BULLET Underground water @BULLET Machinery @BULLET Human metabolism @BULLET Oxidation @BULLET Blasting @BULLET Rock movement @BULLET Pipelines It was once understood that this was also the order of importance of the heat sources; however, recent studies have shown that each mine is unique in its heat source distribution [4][5][6]. Table 1shows the heat load distributions for mines in Canada, Australia, and the US. The relative contributions of the major heat sources are affected by several factors including: @BULLET Depth of the mine @BULLET Level of mechanization @BULLET Mine power sources @BULLET Geothermal activity @BULLET Rock thermal properties, etc. ...
... The heat removal capacity of the air can be calculated using psychrometric equations and the heat load is determined as discussed in section 3.1. The ability of ventilation systems to effectively cool the air decreases at a depth of about 3,300 ft (1000 m) [5]. Below this depth, use of localized cooling methods and refrigeration might be necessary for heat removal from the active areas of the mine. ...
... Therefore, a comprehensive strategy of monitoring for field data collection would be critical to employ an accurate climatic model. Furthermore, studies show that hourly, daily and seasonal temperature changes can produce significant 3odeling errors [5, 7]. Kocsis et al [5] highlighted that the difference between simulated and measured climatic parameters is the result of the dynamic time delay of temperature and humidity spikes along the advection pathways of the ventilating air due to the " thermal flywheel effect " (TFE). ...
As the increasingly mechanized underground mines in Northern Nevada become deeper, the issue of heat becomes a significant problem. Hot and humid environments can seriously affect the performance, overall productivity and most importantly the ability of the underground workforce to perform work in a safe manner. When the underground working places become excessively hot, the volume of a mine’s intake air, its temperature and humidity can be altered in order to improve the underground climatic conditions. Power supply modifications may also be exercised. As a last resort, refrigeration of the ventilating air may be required.
To understand and model heat and humidity transport, all major heat sources in an underground mine need to be identified and quantified. There can be a considerable difference in the spectrum of the heat and mine power source distributions between different mines due to many factors such as depth, mechanization, power sources, geothermal activity and rock thermal properties. To assess the atmospheric and underground environmental conditions, multi-channel climatic monitoring units will be installed along vertical and horizontal airways from surface to the lowest production level at various underground mines in Northern Nevada. To identify the mining equipment responsible for increasing temperature and humidity in the production workings, equipment activity surveys will also be conducted in parallel with the climatic monitoring program.
This paper aims to begin discussing best practices and provide recommendations in respect to the design and use of atmospheric and environmental monitoring systems involving heat and humidity in deep and hot US mines. The collected climatic and equipment activity data will be used to validate a dynamic climatic model developed by means of a ventilation/climatic software package. Heat flows will be quantified from the mining equipment, strata, auto-compression and other major heat sources. The validated model will be used to predict the underground climatic conditions of yet undeveloped orebodies and future underground mines. Furthermore, this dynamic model can also be used to assess various cooling strategies used world-wide and identify the most effective cooling and refrigeration methods which can be effectively and economically employed in hot US mines.
... If the shear movement is resisted then the fluid is called real. In reality ideal fluids do not exist, however in some cases the resistance is small enough to be insignificant (Hartman et al.,2005). ...
... The determination of frictional pressure drop (p) in mine airways may be obtained from the Equation 2. This is a form of the Chezy‐Darcy Equation, applicable to circular and non‐circular airways and ducts. The Chezy‐Darcy coefficient of friction (dimensionless) varies with respect to Reynolds Number, the trend of which is plotted on the Moody diagram (Hartman, 2005). The first part of this equation, related to frictional pressure drop and quantity to resistance, known as the Square Law is used to establish resistance from measured pressure and quantity data. ...
The assumption on the design for the mine airflows is that the frictional factor for the entry is 0.0028 Ns 2 /m 4 (for smooth pipe), the entry cross section is 0.899 m 2 , the entry perimeter is 3.36 m, the modelled pillar is maintained at a fixed length and the diameter of the duct 1.07 m while other parameters like the air volume, length of road way and the pillar width are varied. The design for the pre‐ventilation system of the Okaba Coal deposit requires 145 m 3 /s of air with a main fan pressure of 2.73 kPa and four booster fans of air volume; 110 m 3 /s, 125 m 3 /s, 95 m 3 /s, 105 m 3 /s whose fan pressure are 0.63 kPa, 0.87 kPa, 0.47 kPa, 0.50 kPa respectively, with exhaust fan of 70 m 3 /s at fan pressure of 0.38 kPa which is required to ventilate the mine.
... Nesse caso, a velocidade do ar na seção é a média aritmética dos valores de velocidade medidos (Figura 1b). Na seleção de um anemômetro, deve-se optar, preferencialmente, pelos anemômetros de pás, visto que os termo-anemômetros sofrem grande influência das condições de umidade do ar e, por vezes, não registram valores adequados de velocidade do fluxo (Hartman, 1991). Para um controle adequado do balanço da ventilação, devem-se posicionar pontos de medida no circuito principal , dividindo-o em seguimentos. ...
... da da ventilação nos painéis em lavra, verificando-se, assim, a possibilidade de recirculação de ar dentro do painel. A NR-22 estabelece os parâmetros para o dimensionamento das necessidades de vazão, sendo o mesmo raciocínio implementado para o dimensionamento do circuito principal de ventilação utilizado para os ventiladores de frente de serviço.Hartman, 1991). ...
Underground mine atmosphere plays an important role in the health and safety of miners. Fresh air flow is the main parameter to be controlled, due to its influence on the remaining ones, such as air temperature, gas concentration and particulate dispersement (dust). The Brazilian occupational safety and health agency recently established rigid limits for these parameters, forcing companies to adapt to new rules. These studies present an analysis on the main mine atmosphere parameters in an underground coal mine. The atmosphere monitoring included measurements in air flow, temperature and humidity, gases and dust. Entries and rooms with insufficient air flow have high temperature and high gas concentrations. Also, the equipment suggested by the norm for taking temperature readings is inadequate (a tree of thermometers) as it interferes with the mining cycle. Additionally, the reading time interval recommended by the norm is insufficient. It should be monitored simultaneously, as there is a clear interference between their results. An improvement in mining atmosphere impacts positively the health, safety and productivity at the mine face.
... Western countries with well-developed mining industries such as US, Germany, Britain, Australia, Poland, South Africa, have researched on air cooling in deep mines, and worked out diverse forms of mechanical cooling systems that have brought good effects. For instance, in US, centralized cooling systems on ground (both cooling and heat dissipation are completed on ground), in underground mines (they are completed in underground mines) and of hybrid usage (cooling completed in underground mines while heat dissipation on ground) are built respectively according to the difference in positions of cooling and heat dissipation for mechanical cooling systems (Howard, 1997;ASHRAE, 2007). Each cooling system can take several specific forms according to specific conditions. ...
Aiming at heat injuries occurring in the process of deep coal mining in China, a ZL400 mine-cooling unit employing semi-hermetic screw compressor with a cooling capacity of 400 kW is developed. This paper introduced its operating principle, structural characteristics and technical indexes. By using the self-built testing platform, some parameters for indication of its operation conditions were tested on the ground. The results show that the aforementioned cooling unit is stable in operation: cooling capacity of the unit was 420 kW underground-test conditions, while its COP (coefficient of performance) reached 3.4. To address the issue of heat injuries existing in No. 16305 U-shaped long-wall ventilation face of Jining No. 3 coal mine, a local air conditioning system was developed with ZL400 cooling unit as the system’s core. The paper presented an analysis of characteristics of the air current flowing in the air-mixing and cooling mode of ZL400 cooling unit used in air intake way. Through
... The resulting R and K are used to assess the ease of mine ventilation through an airway and are defined by Eqs. (2) and (3) [9]. ...
Convergence of roof and floor in underground mine openings is a common occurrence. This convergence not only adversely affects the ability of workers, equipment and supplies to travel through the mine, it also reduces the effectiveness of the mine ventilation system, which is essential for the dilution of methane gas and airborne respirable dust. While installing secondary standing supports to control floor and roof convergence, such supports, by nature, partially obstruct a portion of the airway. These added obstructions inhibit the ability of the ventilation system to operate as efficiently as it could by increasing the resistance in and reducing the cross-sectional area of the airway. This study introduces and demonstrates the benefits of The Eye CAN™ standing roof support, which controls floor and roof convergence and is less obstructive to air flow than conventional wooden cribs. Laboratory findings show that the normal resistance of a supported lined airway is reduced by using this new product from Burrell Mining Products, Inc., while providing the same roof support characteristics of an established product—The CAN®. Load vs. displacement curves generated from laboratory tests demonstrated that this new product behaves with the same roof support characteristics as others in The CAN product family. Ventilation data gathered from a simulated mine entry was then used for computational fluid dynamics (CFD) modeling. The CFD analysis showed an improvement with The Eye CAN vs. other accepted forms of standing roof support. This proof-of-concept study suggests that, when using this new product made by Burrell Mining Products, Inc., not only will the convergence from the roof and floor be controlled, but airway resistance will also be reduced.
... El buen diseño minero y la eficiencia en los sistemas de ventilación contribuyen a hacer aún más rentable una explotación de este tipo. En ventilación de minas se suele utilizar la ecuación de Atkinson (Hartman, 1982) para estimar las pérdidas de energia por fricción y por choque debido a las singularidades. Las pérdidas por choque suelen ser menores que las pérdidas por fricción, aunque pueden llegar a ser casi tan importantes en minas con diseños mineros que hacen tortuoso el paso del aire. ...
RESUMEN: En este trabajo se muestran los resultados de la caracterización experimental y numérica del sistema de ventilación aplicado a las calles de producción en un sistema de explotación Block Caving. Las calles de producción son las zonas de mayor contaminación del aire de todo el método de explotación. El layout corresponde al método block caving tipo El Teniente. Los resultados se encuentran en términos de las pérdidas de carga por choque. Experimentalmente, los resultados son obtenidos a partir de modelos a escala. En tanto, los resultados numéricos son obtenidos a partir de simulaciones CFD (Computational Fluid Dynamics). Los resultados de los modelos a escala muestran buena coherencia y un comportamiento similar, con diferencias reducidas, lo que permite validar las condiciones aplicadas a la simulación de las geometrías a escala real. Los modelos aquí obtenidos pueden ser utilizados como herramientas para estimar la caída de presión en el sistema, desde que el aire ingresa desde el subnivel de inyección hasta que es evacuado al sub nivel de extracción.
... Due to the electrical system constraints, the parallel fan was equipped with a variable frequency drive (VFD) and a starting protocol was developed to allow for both fans to start with the minimum energy requirement and also to avoid any of the fans entering in a stall condition during the starting process. Because of the high velocity generated in the tunnel with both fans working in parallel, which is considered to be not energy efficient, meaning that is larger than the economical velocity generated by the cross section economical analysis (McPherson, 2009 and Hartman, 1997), a solution is being studied at the moment to use abandoned ventilation infrastructure of the mine to generate a parallel airway to the 58 Adit as close as possible to the location of the fans. This study is work in progress, and aims to reduce the velocity of the airflow and the power requirements for operation. ...
The New Level Mine project (NLMP), the planned underground expansion of the El Teniente mine in Rancagua, Chile, is expected to reach a daily extraction rate of 137 to 180 ktpd upon achieving full capacity. Production is planned to start in the year 2017 and the current plan is to meet that target through two development phases, from the year 2012 to 2014 and from the year 2015 to 2017. To achieve the 2012 to 2014 underground development schedule, the ventilation requirements have been estimated in the range of 189 m 3 /s (400 kcfm), and cannot be made available without significant modifications to the current system of El Teniente. As a result, a certain number of alternatives were explored to find a solution to this shortfall, for example, adding raises to generate parallel airways and installing fans to reinforce the current ventilation system. From the alternatives studied, the installation of a second main fan (system) in parallel to an existing one was identified as the best solution, and selected for implementation, however the location was not ideal and there were concerns as to the operation of both fans once the second fan was installed. This paper presents the study used to estimate the operational points of both the current and the new fan, and to justify the parallel installation of the additional main fan. An additional computational fluid dynamics study was undertaken to validate the operational point, given the particular geometry of the fan's location and placement, to guarantee a stable operation of the fans. Finally, the protocols arising out of this work for starting the fans, and operating them in parallel to avoid generating a stall condition and damaging the investment are discussed.
... In mines, especially deep mines, miners face a hard work environment caused by high humidity levels (that can easily reach 80%) and high ambient temperatures. Among other things, these harsh conditions stem from air self-compression (an approximately 9˚C increase for every 1 km of depth), the heat produced by vehicles and mining equipment and the temperature of the rocks that can reach up to 50˚C [2] [3]. ...
Workers exposed to hot and humid conditions suffer from heat stress that affects their concentration and can potentially lead to an increase in workplace accidents. To minimize heat stress, protective equipment may be worn, such as personal cooling garments. This paper presents and discusses the performances, advantages and disadvantages of existing personal cooling garments, namely air-cooled, liquid-cooled, phase change, hybrid, gas expansion and vacuum desiccant cooling garments, and a thermoelectric cooling technology. The main objective is to identify the cooling technique that would be most suitable for deep mining workers. It appears that no cooling technology currently on the market is perfectly compatible with this type of mining environment.
However, combining two or more cooling technologies into a single hybrid system could be the solution to an optimized cooling garment for deep mines.
... Hence due to the above reason the rise of DBT due to auto compression effect becomes less and on the other hand the WBT rises more than the above rate. There is another derivation [12] for calculation of heat source added in the mine environment due to auto compression of air in the shaft the following procedure is followed; ...
1.0 ABSTRACT The future prospect of underground coal mining in Indian mines is either from extensive mines or at depth (> 300 m). In this situation the intake air is expected to be influenced by various parameters, viz. auto-compression, surface air temperature (seasonal temperature variation), heat due to explosive detonation, heat from mechanized equipments, metabolic heat, heat from broken rock, wall rock heat flow, heat from other sources etc. Many mines in our country are receding towards lower horizon by taking the liability and responsibility of upper seams. In order to address the problem of oppressive climatic conditions at the workings, behavior of various parameters affecting the quality of intake are required to be studied for realistic ventilation planning of deep mines. The effect of auto compression is one of them. The paper deals with realistic estimation of heat addition to the intake air due to auto compression. 2.0 INTRODUCTION Many Indian coal mines have become extensive or receding towards greater depth. As a result in many mines work place environment has become oppressive and affecting the productivity and safety. The importance of ventilation has been realized since beginning of mining operation. It has been established that it has got direct relation with production, productivity and safety of the mines. In a study [1] the relation of wet bulb temperature at workplace environment and efficiency of the workers has been established. On the basis of literature, in US metal mines maximum efficiency is at or below 27 0c and economical efficiency is between 27 0 C to 29 0 C. In addition, the inspectorates of different coal producing countries have also stipulated the value of maximum permissible wet bulb temperature as per their climatic condition considering the miners health. These values are for coal mines India [2] , USA [3] , UK [4] are 33.5 0
... The control of primary ventilation flows or circuits in a mine requires careful planning from the design stage and thereafter throughout the operating life of the mine. It is strongly recommended that as part of the initial design of any mine or a planned upgrade that computer simulation of the ventilation network be done to assist in (Hartman, 1997) ...
Simulating a ventilation network of an underground mine can help in solving complex ventilation systems with many features, selecting proper fan specifications, location and settings. Early computer systems running simple network simulations were able to provide solutions to the most common and immediate problems regarding underground mine airflow. The more advanced systems available today can perform more sophisticated modeling and simulation of a mine's ventilation network and present their results in a more understandable and easy to communicate form. This paper presents a ventilation network case study from an underground mine. All aspects of mine ventilation network modeling and simulation are discussed as well as the results from the simulation process. The algorithms and techniques used are thoroughly explained. Some useful guidelines for the application of ventilation network software are also provided in the text.
... Test #1 was conducted in the actual Goldhunter rock mass, whereas Test #2 was conducted in a rock mass mo re typical of the lower Lucky Friday Mine. The values estimated from published literature (Hartman, 1982) and used in the initial ventilation and refrigeration study were 3.0 W/m°C ( ...
In many hot mines a large portion of the total heat load is asso ciated with the surrounding strata. In order to maintain acceptable underground environmental conditions, the mine heat load must be controlled by the ventilating airstream, and in certain cases by mechanical refrigeration. To compute existing, or future heat additions from the surrounding rock, certain parameters must be determined. These parameters include the rock thermal conductivity, thermal diffusivity, and the geothermal gradient (with relation to a virgin rock datum). These rock thermal parameters are typically estimated from published literature, or evaluated by laboratory or in-situ measurements. Presented in the paper are the results from a series of tests conducted at Hecla Mining Company's Lucky Friday Mine. These tests include in-situ measurements of rock thermal conductivity and geothermal gradient, which were performed in highly active sections of this deep silver mine. The results from the in-situ tests are compared with data obtained from laboratory testing of mine core samples. The methodology, measurement equipment, test data, and main results are described.
... Stoppings, as defined by Hartman et al (1997), are physical barriers erected between intakes, returns or abandoned mine voids to prevent air from mixing. Stoppings are classified according to construction, length of service, and purpose as temporary or permanent. ...
... Generally acceptable practices use various VCDs such as stoppings, seals, overcasts, airlocks and regulators arranged so that air flows in the desired manner at appropriate quantities. A stopping, as defined by Hartman et al (1997), is a physical barrier erected between intakes, returns or abandoned mine voids to prevent air from mixing. A seal is a special stopping used to isolate abandoned workings and goafs or as fire bulkheads. ...
In the Kubang Kicau mining area at PT ANTAM Tbk UBPE Pongkor, Bogor District, West Java Province, there is a change in the quantity of air in the ventilation system. The change is due to a decrease in air flow from the blower fan with flexible duct. Air leakage in the area around the main fan causes air to return. Thus it is necessary to research changes in air quantity. The purpose of this study is to determine the decrease in air flow in the new condition blower fan 37 kW with a flexible duct distance of 100 m and a reconditioned blower fan 15 kW with a flexible duct distance of 30 m, as well as determine air leakage in the area around the main fan. Data processing is carried out to determine the tunnel area, air leakage area, flexible duct area, air flow reduction, and air leakage. The data required are tunnel dimensions, air leakage area dimensions, flexible duct distance, air velocity, and air flow from the blower fan specification (GIA SwedVent). The decrease in air discharge determined by the company is a maximum of 15%. The decrease in air flow in the blower fan 37 kW is 22.96% and the decrease in air flow in the blower fan 15 kW is 37.19%. Thus the two blower fans do not meet the standards set by the company. The amount of air leakage around the main fan is 1.391-10.601% so it still meets the standards set by the company. Abstrak. Pada area penambangan Kubang Kicau di PT ANTAM Tbk UBPE Pongkor, Kabupaten Bogor, Provinsi Jawa Barat, terjadi perubahan kuantitas udara pada sistem ventilasi. Perubahan tersebut karena penurunan debit udara dari blower fan dengan flexible duct. Leakage udara pada area sekitar main fan mengakibatkan udara balik. Dengan demikian perlu dilakukan penelitian perubahan kuantitas udaranya. Tujuan penelitian ini yaitu mengetahui penurunan debit udara pada blower fan 37 kW kondisi baru berjarak flexible duct 100 m dan blower fan 15 kW rekondisi berjarak flexible duct 30 m, serta mengetahui leakage udara pada area sekitar main fan. Pengolahan data dilakukan untuk menentukan luas tunnel, luas area leakage udara, luas flexible duct, penurunan debit udara, dan leakage udara. Data yang diperlukan adalah dimensi tunnel, dimensi area leakage udara, jarak flexible duct, kecepatan udara, serta debit udara dari spesifikasi blower fan (GIA SwedVent). Penurunan debit udara yang ditentukan oleh perusahaan yaitu maksimal 15%. Penurunan debit udara pada blower fan 37 kW yaitu 22,96% dan penurunan debit udara pada blower fan 15 kW yaitu 37,19%. Dengan demikian kedua blower fan tersebut tidak memenuhi standar yang ditentukan oleh perusahaan. Banyaknya leakage udara di sekitar main fan yaitu 1,391-10,601% sehingga masih memenuhi standar yang ditentukan oleh perusahaan.
This paper presents the results regarding the prevention and control of gas hazards in a high-gas tunnel under construction. First, some effective methods were introduced, and the results of the gas pressure and gas content measured with and without the prevention methods were compared. Next, the gas emission amounts were predicted according to the measurements, and the required air volume for preventing a potential gas explosion hazard was determined. Finally, a computational study was carried out to investigate the effects of the transverse and longitudinal outlet locations of the ventilation duct on the gas movement in the tunnel. The results showed that with an increase in the longitudinal distance between the outlet and the heading face, the percentage of dead zones at the heading face of the upper bench increased, while the percentage of dead zones at the heading face of the lower bench observably decreased at first and then increased gradually. Additionally, the maximum methane concentration decreases initially and then increases. The percentages of dead zones were at relatively low levels when the outlet was located at the tunnel vault, whereas some relatively higher percentages of dead zones existed when the outlet was located at the tunnel spandrel or hance. The maximum methane concentration increased gradually when the location of the ventilation outlet moved away from the tunnel axis. In this case, the optimal outlet location for the ventilation duct was suggested to be 20 m away from the heading face of the upper bench and located near the tunnel vault.
Calculation of Friction Factor - Methods, Tools, Data Analysis in Mine Ventilation Ducting and Network.
Heat is emitted into subsurface ventilation systems from a variety of sources. In the majority of the world’s coal mines, the airstream itself is sufficient to remove the heat that is produced. In deep metal mines, heat is usually the dominant environmental problem and may necessitate the use of large-scale refrigeration plant. Conversely, in cold climates, the intake air may require artificial heating in order to create conditions that are tolerable for both personnel and equipment.
At present, local limestone mines with large opening employ auxiliary fans for workplace ventilation which have been used in coal mines with much smaller airways. Considering the low static pressure loss in the large-opening mines, high pressure auxiliary fans face serious economical limitations mainly due to their excessive capacity. The optimal fan selected for the ventilation in large-opening working places should supply air quantity enough for maintaining safe environment and keep its operating cost as low as possible. This study focuses on the development of a low pressure auxiliary fan designed to have smaller range of the static head but to have more potential for higher ventilation and energy efficiency. The flow characteristics of high and low pressure auxiliary fans were theoretical as well as experimentally investigated to assess the ventilation efficiency in term of environmental and economical aspects. Moreover, the low pressure fan was tested in two limestone mine sites with small and large cross-sectional areas for evaluating its ventilation efficiency. Results from this study can be applied to improve the economy and efficiency of auxiliary fan for ensuring better air quality and work environment management.
In this study, the thermal environment in a large scale coal mine located in Taebaek, Gangwondo was assessed by a field survey. In order to estimate the thermal environment, various heat stress indices such as WBGT, HSI, ESI, KATA index and effective temperature were investigated. Correlation analysis was also conducted. It was found that the thermal environment in most workplace was high. In particular, the correlation coefficient between HSI reflected in physiological fatigue characteristic and the maximum sweat evaporation heat was -0.834. This shows that the correlation coefficient have the most influence on HSI index. The factor which has the most influence on the maximum sweat evaporation heat is velocity of air. The thermal environment of high-depth coal mines is likely to be improved by installing a structure that enables the maximum prevention of extended digging, air doors, or the leakage of the inflow of air in the first shaft.
In mine ventilation networks, the reasonable airflow distribution is very important for the production safety and economy. Three basic problems of the natural, full-controlled and semi-controlled splitting were reviewed in the paper. Aiming at the high difficulty semi-controlled splitting problem, the general nonlinear multi-objectives optimization mathematical model with constraints was established based on the theory of mine ventilation networks. A new algorithm, which combined the improved differential evaluation and the critical path method (CPM) based on the multivariable separate solution strategy, was put forward to search for the global optimal solution more efficiently. In each step of evolution, the feasible solutions of air quantity distribution are firstly produced by the improved differential evolution algorithm, and then the optimal solutions of regulator pressure drop are obtained by the CPM. Through finite steps iterations, the optimal solution can be given. In this new algorithm, the population of feasible solutions were sorted and grouped for enhancing the global search ability and the individuals in general group were randomly initialized for keeping diversity. Meanwhile, the individual neighborhood in the fine group which may be closely to the optimal solutions were searched locally and slightly for achieving a balance between global searching and local searching, thus improving the convergence rate. The computer program was developed based on this method. Finally, the two ventilation networks with single-fan and multi-fans were solved. The results show that this algorithm has advantages of high effectiveness, fast convergence, good robustness and flexibility. This computer program could be used to solve large-scale generalized ventilation networks optimization problem in the future.
Recent wellsite disasters have led to an increased emphasis on properly sized mud/gas separators. This paper reviews and analyzes existing mud/gas separator technology and recommends separator configuration, components, design considerations, and a sizing procedure. A simple method of evaluating mud/gas separation within the separator vessel has been developed as a basis for the sizing procedure. A mud/gas separator sizing worksheet will assist drilling personnel with the sizing calculations. The worksheet provides a quick and easy evaluation of most mud/gas separators for a specific well application. A brief discussion of other mud/gas separator considerations is provided, including separator components, testing, materials, and oil-based-mud considerations.
NVP analysis was carried out by the thermodynamic method, which is more accurate than the hydrostatic method. Based on this technique, it was found that the greater the differences are as the height of ventilation shaft, temperature, the larger the natural ventilation pressure generated. It was also found that the NVP with a vertical ventilation shaft was much greater than that without a shaft. The NVP with a vertical ventilation shaft may have benefited from passive ventilation by a cost-efficient contaminant elimination method and even minor emergency control method in a long road tunnel using the longitudinal ventilation system. The airflow caused by the NVP was large enough (up to 29.26 % of mechanical ventilation) to increase the efficiency of the ventilation system.
Field measurements of the natural ventilation of the Diyarbakir Old City Municipality Building located in Southeastern Region of Turkey were conducted throughout a year. Ventilation need is determined from adequate and fresh air requirements to the working area for better working conditions.The objective of the study was to clarify environmental conditions that modify the health of the occupants and their sensations of comfort. In particular, natural ventilation quantity based on CO2 and O2 concentrations and open office planning are considered within this paper. The total airflow requirement and natural airflow rate were determined. The building should be ventilated hourly in order to provide necessary comfort conditions in case of all openings are closed. Finally, necessary recommendations on better working environment were made.
The common approach in matching a fan to a duty is to determine the intersection between the fan curve and a single line system characteristic. The single line characteristic denotes a leak-free duct but it is common knowledge that all ducts leak to some extent. This presentation demonstrates that a leaky duct has dual characteristics. One which compensates for the increases in fan pressure and quantity caused by the leakage (which is detected by the fan), and a ‘shadow’ characteristic which shows the quantity delivered to the discharge end.Atkinson’s equation was used to demonstrate the sensitivity of a leak-free duct to changes in duct diameter, friction factor, length and flow quantity. The concept of ‘duct efficiency’ was introduced to quantify the effect of leakage on the performance of a ventilation duct and demonstrate the sensitivity of a leaky duct to same changes.A spreadsheet method, which has been verified using the National Coal Board (UK) leakage design charts, was used to quantify the leakage coefficients and to establish the dual characteristics for leaky ducts. These characteristics have then been applied to a case study to assess the performance of a fan connected to 500 m of a fabric duct in an operating decline.
Many buildings in warm humid climates, particularly in tropical regions, rely for much of the time on natural ventilation from prevailing breezes for indoor thermal comfort. Much effort in recent years has been directed toward the use of computational fluid dynamics in evaluating airflow through buildings based on the solution of Navier-Stokes equations incorporating a turbulence model. This approach requires extensive data preparation and a reasonably powerful computer to yield results within an acceptable computation time for both numerical solution and simulated flow visualisation. Quantitative evaluation of natural ventilation through many low budget buildings in tropical regions is not evaluated due to a lack of suitable simple computer programs. What is needed are programs that can run on modest personal computers and be used quickly to compare the relative natural ventilation performance of alternative building layouts for prevailing breeze directions during the preliminary design stage. Smaller buildings are often designed for cross ventilation by prevailing breezes with flow entering a windward opening and exhausting through a leeward opening. Such flow through a limited number of openings in series can be calculated very quickly on a personal computer using an orifice flow approach based on estimates of pressure differences and discharge coefficients of openings. When buildings have external ventilating openings in a number of rooms and flow branches within the building, it is no longer possible to calculate directly the airflow in the various branches of the airflow network. Flow in such networks can be analysed iteratively on a personal computer by repetitive solution of simultaneous equations for flow rates in branches at nodes and conservation of mass flow through the network. The procedure described in the paper uses the Hardy Cross method of balancing flows at network nodes until errors throughout the network are acceptably small. Sources of data on wind pressure distributions over building walls and shielding influence of nearby buildings are provided together with a detailed description of a procedure for solving network airflows sufficient for readers to write their own computer code.
This study evaluated the influence of activewear undergarments worn under the standard mining coveralls on whole-body heat exchange and change in body heat content during work in the heat. Each participant performed 60 min of cycling at a constant rate of heat production of 400 W followed by 60 min of recovery in a whole-body calorimeter regulated at 40°C and 15% relative humidity donning one of the four clothing ensembles: (1) cotton underwear and shorts only (Control, CON); (2) Activewear only (ACT); (3) Coveralls+Cotton undergarments (COV+COT); or (4) Coveralls+Activewear undergarments (COV+ACT). In the latter two conditions a hard hat with earmuffs, gloves, and socks with closed toe shoes were worn. We observed that both COV+COT and COV+ACT resulted in a similar mean (±SE) change in body heat content, which was significantly greater compared with the CON and ACT during exercise, suggesting that the rate of thermal strain was elevated to a similar degree in both coverall conditions (CON: 245±32 kJ; ACT: 260±29 kJ; COV+COT: 428±36 kJ; COV+ACT: 466±15 kJ; p<0.001). During recovery, the negative change in body heat content was greater for both COV+COT and COV+ACT compared with the CON and ACT but similar between COV+COT and COV+ACT due to the greater amount of heat stored during exercise (CON: -83±16 kJ; ACT: -104±33 kJ; COV+COT: -198±30 kJ; COV+ACT: -145±12 kJ; p=0.048). Core temperatures and heart rate were also significantly elevated for the COV+COT and COV+ACT compared with the CON and ACT conditions during and following exercise (p<0.05). These results suggest that while activewear undergarments are not detrimental, they provide no thermoregulatory benefit when replacing the cotton undergarment worn under the standard coverall during work in the heat.
This paper describes a new industrial case on automation, for large scale systems with high environmental impact: the \emph{mining ventilation} control systems. Ventilation control is essential for the operation of a mine in terms of safety ($CO$ and $NO_x$ regulation) and energy optimization. We first discuss a novel regulation architecture, highlighting the interest for a model-based control approach and the use of distributed sensing capabilities thanks to a wireless sensor network (WSN). We propose a new model for underground ventilation. The main components of the system dynamics are described with time-delays, transmission errors, energy losses and concentration profiles. Two different model-based control approaches, which can embody the complex dynamics of the system, are proposed. The first one resorts to a nonlinear model predictive control strategy (receding horizon) and aims to energy minimization thanks to a continuous operation of the fans. The second one, based on a hybrid description of the model and fans operation, provides automatic verification of the wireless control thanks to abstraction techniques. These control strategies are compared with simulations, in terms of regulation efficiency, energy consumption and need for computational capabilities. The industrial case description and control strategies open new vistas for the development of global system approaches that allow for the optimization of energy consumption of complex large-scale systems.
One very reliable approach to establishing air quantity through a ventilation branch is through measurement of differential pressure across an opening or regulator. Mathematical relationships are available to relate (with some qualifications) pressure drop and quantity through an orifice placed symmetrically in a round flow conduit. However these can only be used to approximate mine regulator behaviour due to variability in construction, questions of symmetry and leakage Efforts to characterize and/or mathematically model a number of types of operating mine regulators are described. Results can be used in the development of a computerized monitoring and simulation system to provide immediate or real time data on air behaviour within each branch within an underground mine ventilation network through linking of sensors to the ventilation network simulation software. This new approach to ventilation provides improved understanding of airflows through all mine sections.
To examine the incidence, clinical state, personal risk factors, haematology, and biochemistry of heat exhaustion occurring at a deep underground metalliferous mine. To describe the underground thermal conditions associated with the occurrence of heat exhaustion.
A 1 year prospective case series of acute heat exhaustion was undertaken. A history was obtained with a structured questionnaire. Pulse rate, blood pressure, tympanic temperature, and specific gravity of urine were measured before treatment. Venous blood was analysed for haematological and biochemical variables, during the acute presentation and after recovery. Body mass index (BMI) and maximum O2 consumption (VO2 max) were measured after recovery. Psychrometric wet bulb temperature, dry bulb temperature, and air velocity were measured at the underground sites where heat exhaustion had occurred. Air cooling power and psychrometric wet bulb globe temperature were derived from these data.
106 Cases were studied. The incidence of heat exhaustion during the year was 43.0 cases/million man-hours. In February it was 147 cases/million man-hours. The incidence rate ratio for mines operating below 1200 m compared with those operating above 1200 m was 3.17. Mean estimated fluid intake was 0.64 l/h (SD 0.29, range 0.08-1.50). The following data were increased in acute presentation compared with recovery (p value, % of acute cases above the normal clinical range): neutrophils (p < 0.001, 36%), anion gap (p < 0.001, 63%), urea (p < 0.001, 21%), creatinine (p < 0.001, 30%), glucose (p < 0.001, 15%), serum osmolality (p = 0.030, 71%), creatine kinase (p = 0.002, 45%), aspartate transaminase (p < 0.001, 14%), lactate dehydrogenase (p < 0.001, 9.5%), and ferritin (p < 0.001, 26%). The following data were depressed in acute presentation compared with recovery (p value, % of acute cases below the normal clinical range): eosinophils (p = 0.003, 38%) and bicarbonate (p = 0.011, 32%). Urea and creatinine were significantly increased in miners with heat cramps compared with miners without this symptom (p < 0.001), but there was no significant difference in sodium concentration (p = 0.384). Mean psychrometric wet bulb temperature was 29.0 degrees C (SD 2.2, range 21.0-34.0). Mean dry bulb temperature was 37.4 degrees C (SD 2.4, range 31.0-43.0). Mean air velocity was 0.54 m/s (SD 0.57, range 0.00-4.00). Mean air cooling power was 148 W/m2 (SD 49, range 33-290) Mean psychrometric wet bulb globe temperature was 31.5 degrees C (SD 2.0, range 25.2-35.3). Few cases (< 5%) occurred at psychrometric wet bulb temperature < 25.0 degrees C, dry bulb temperature < 33.8 degrees C, air velocity > 1.56 m/s, air cooling power > 248 W/m2, or psychrometric wet bulb globe temperature < 28.5 degrees C.
Heat exhaustion in underground miners is associated with dehydration, neutrophil leukocytosis, eosinopenia, metabolic acidosis, increased glucose and ferritin, and a mild rise in creatine kinase, aspartate transaminase, and lactate dehydrogenase. Heat cramps are associated with dehydration but not hyponatraemia. The incidence of heat exhaustion increases during summer and at depth. An increased fluid intake is required. Heat exhaustion would be unlikely to occur if ventilation and refrigeration achieved air cooling power > 250 W/m2 at all underground work sites.
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