1423 possibility of obtaining methane from the post-mining workings of an active mine by implementing a parallel methane drainage system for low concentration methane. This also required the consent of the Higher Mining Authority President to waive the applicable regulations on the minimum methane concentration in the gas captured at the methane drainage station. In Polish regulations, it is 30%, while in the planned installation, the minimum concentration will be 20%. Such a solution obviously requires the use of additional technical requirements to increase safety. Prototype installation will be built in the ‘Pniówek’ mine, owned by Jastrzębska Spółka Węglowa. Figure 92 - Reduced concentration methane drainage system diagram at Pniówek coal mine The methane obtained from post-mining goafs will be used to produce electricity in dedicated gas engines connected to electricity generators enabling the production of electricity from gas with a methane concentration of 20÷40%. The solutions tested in this project will ultimately be implemented in all JSW mines. They can also be successfully used in any methane-bearing hard coal mine in the world with a multiseam deposit. Figure 2 presents a diagram of a methane drainage network with reduced methane concentration, which is being developed at the Pniówek coal mine. The project identifies possible methane intake points, where drainage boreholes will be made and, after confirming the appropriate gas parameters, connected to the methane drainage network. An essential element are the dams isolating the post-mining goafs. They will be sealed and connected to the system. For this purpose, tests of rock mass fractures around the dams were carried out and a design for their sealing was developed. The gas captured by the methane drainage station at shaft #V of the Pniówek coal mine will be delivered to energy generation modules. This solution allows methane, which was previously released into the atmosphere with ventilation air, to be used for electricity production. The benefits in terms of safety and environmental protection are obvious, as are the financial benefits resulting from savings in electricity purchases. 3. METHANE FROM VENTILATION AIR VAM – DISPOSAL OR UTILISATION? The purpose of ventilation in mines is to ensure a supply of fresh air and remove harmful substances in order to create safe working conditions. As mentioned earlier, a significant amount of methane is released during mining, some of which is captured through methane drainage, while the rest mixes with the air and is discharged into the atmosphere through exhaust shafts. For safety reasons, Polish mining regulations allow a maximum methane concentration of 0.75% in ventilation shafts. These values are much lower in shafts, averaging between 0.2% and 0.4%.
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