Mine Ventilation Gb Mishra.pdf

Mine Ventilation Gb Mishra.pdf

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Abstract Mining is a risky activity, the risk factor increases exponentially when it comes to underground mine. Working conditions in underground coal mines are much more dangerous than in underground metal mines, as it incorporates the risk of roof fall due to soft strata and the hazardous gases that may be present in an influential quantity that can have physiological effects on the human body and can even be lethal. Timely Detection of these hazardous gases is a major challenge and needs to be followed for the safety of the miners present in the mine. In this paper we have discussed about different gases and their effects; we have proposed to create a mine gas detection system that will consist of gas detecting sensors, a wireless network provider and a microcontroller. MQ-4 and MQ-7 will be used for the detection of CH4 and CO respectively. These sensors will be connected to Arduino board which will be connected to an LCD display that will regularly show the percentage of CH4 and CO. The wireless network will be provided by using Zigbee wireless network. In this paper we have also discussed the places in the mine where the sensors will be installed and the steps that has to be taken by the required professional once the gas has been detected.

An underground mining operation proves to be a risky venture as far as the safety and health of workers are concerned. These risks are due to different techniques used for extracting different minerals. The deeper the mine, the greater is the risk. These safety issues are of grave concern especially in case of coal industries. Thus, safety of workers should always be of major consideration in any form of mining, whether it is coal or any other minerals. Underground coal mining involves a higher risk than open pit mining due to the problems of ventilation and potential for collapse. However, the utilization of heavy machinery and the methods performed during excavations result into safety risks in all types of mining. Modern mines often implement several safety procedures, education and training for workers, health and safety standards, which lead to substantial improvements in safety, level both in opencast and underground mining.

A worker in a mine should be able to work under conditions which are safe and healthy for his body. At the same time the environmental conditions should be such as will not impair his working efficiency. This is possible if mine air is nearly the same as on the surface without toxic and inflammable gases.

The gases are the present in the underground mines are flammable gas (CH4), Noxious gases (NO2, NO3, N2O5), Carbon Monoxide (CO), Carbon Dioxide (CO2). Hydrogen Sulphide (H2S), Sulphur Dioxide (SO2). The permissible limit set for these gases are as follows

Different gases that are present in the mine have different effects on the human body and can also cause explosion if reaches above a certain limit. The effects of some of the harmful gases are as follows:-

Methane This is the gas which is responsible for most of the underground mine explosions. It forms a layer just below the roof of the mine. The gas is not poisonous but can suffocate a person due to lack of oxygen[2].

In the earlier days for the gas detection the warm blooded birds like munia were commonly used as they as they are affected much earlier than man by CO. such birds forms essential equipment for the rescue party enterning into the mines after an explosion or fire. With 0.15% of CO present in the air a bird shows distress (ruffing of feathers, pronounced chirping and loss of liveliness) in 3 minutes and fall of the perch in 18 minutes. With 0.3% CO the bird shows almost immediate distress and fall of its perch in 2-3 minutes. Immediate signs of distress are not likely to be observed on birds when exposed to only 0.1% CO.

TABLE-1 (In the above table the sources and the explosives limits of the common gases that are found in the mine are shown)[4]Coal has always been the primary resource of energy in India, which has significantly contributed to the rapid industrial development of the country. About 70% of the power generation is dependent on it. Thus, the importance of coal in energy sector is indispensable. But the production brings with it the other byproducts, which proves to be a potential threat to the environment and the people associated with it. Present work is a sincere attempt in analyzing the graveness and designing a Gas Monitoring system of detection by using the Zigbee technology.

A wired communication system inside underground mines is not effective, efficient, economic and reliable. Due to unexpected roof fall at any moment the entire communication system of the total network may collapse. Effective communication is critical to the success of response and rescue operations; however, unreliable operation of communication systems in high-stress environments is a significant obstacle to achieving this. To improve security, protection and productivity in underground mines, a consistent communication system must be established btween personnel, working in the premises of underground mine, and the control room. A wireless communication system is must for the safety point of view of the personal working inside the underground mines. Therefore a fast, accurate, flexible, and reliable Zigbee Wireless network technology is used in our work[3].

These type of detectors are filled with some chemicals and changes the color according to the concentration of a particular gas present in the atmosphere. Later the color of the tube is matched with the chart and the percentage of the harmful gases can be determined. Eg- P.S detector, Hoolamite detector, Dragermultigas detector.

Many companies have now started producing automatic detectors which tells the exact concentration of the gases present in the mine environment, these devices are able to detect even a very small amount of gas percentage. some of the leading companies that manufactures these kind of devices are EMCOR, M.S.A Ltd. , Uptron etc. these gas detecting devices are also featured with adjustable probe in order to take the readings from the roof. E.g.- Automatic fire damp detector, Interference methanometer, memacs I etc.

These sensors are used in the chemical plants to detect the gas leakages. These sensors have now started to find application in the underground mines for the continous monitoring of the harmful gases. Eg- MQ4, MQ7.

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Abstract:Methane, which is commonly found in hard coal deposits, represents a considerable threat to the safety of mining operations in these deposits. The paper presents the results of tests, aiming to limit the negative impact of methane on hard coal exploitation and improve work safety. The tests encompassed an analysis of methane concentration distributions in the tailgate (in the intersection area with the longwall), with account being taken of auxiliary ventilation equipment. This equipment is responsible for reducing methane concentration levels in the intersection area between the longwall and the tailgate. The analyses presented in the article were conducted for a spatial model of a longwall area, using the Computational Fluid Dynamics (CFD) method. Account was taken of the real-world measurements of the headings as well as the measurement data concerning methane concentration and ventilation parameters. The tests took into account methane emissions from the mined coal and from the goaf with caving. The analyses were performed for the system with and without auxiliary equipment, for different velocities of the additional air stream. This made it possible to compare both systems and determine the impact of auxiliary equipment on the distribution and concentration of methane in the most vulnerable area of exploitation. The distributions of the air and gas mixture were also determined in the analysed headings and goaf with caving. The results obtained clearly demonstrate that using auxiliary equipment has a significant effect on the ventilation parameters of the air stream and leads to reduction in methane concentrations in the most vulnerable section of the longwall. These results also confirmed the advantages of auxiliary ventilation equipment, which should contribute to their wider application in underground hard coal exploitation.Keywords: methane hazard; longwall ventilation; mining exploitation; CFD 2b1af7f3a8