A Method to Accurately Determine the Methane Enrichment Zone of a Longwall Coal Mine

Large numbers of gobs are produced as a result of underground longwall mining, and a large amount of these gobs is known to contain methane gas reserves. The efficient drainage of these methane resources is directly dependent on accurately determining the methane enrichment zone (MEZ) in longwall mining gobs. In this study, a method for accurately determining the MEZ within the zone of interconnected fractures, which utilized a surface directional borehole (SDB) technique, was proposed. The SDB was designed and implemented in a longwall gob located in the Sihe Coal Mine in China’s Shanxi Province. The trajectory of the SDB constantly varied in the different overlying stratum layers and locations above the gob. The methane flow rate and concentration from the SDB, along with the methane concentration in the upper corner of the longwall face, were monitored and obtained as the longwall face advanced. Then, by analyzing the acquired data of the different horizontal and vertical positions of the SDB, the accurate locations of the MEZ within the zone of interconnected fractures were determined. There were the methane decrease zone (MDZ) and methane shortage zone (MSZ) below and above the MEZ, respectively. The results showed that in the MEZ, both the methane flow rate and concentration displayed slight decreasing trends and maintained high levels as the distance from the roof of the coal seam increased. In the MDZ, a sharp decline was observed in the methane flow rate. However, a relatively high methane concentration had still been maintained. In the MSZ, both the methane flow rate and concentration displayed dramatic fluctuation and relatively low levels. The average methane flow rates in the MEZ were determined to be 1.3 and 1.6 times higher than those in the MDZ and MSZ, respectively.

About trends of improvement of technological schemes for methane recovery from the rock-coal massif

Purpose of the research was to improve efficiency of underground gas drainage from the rock-coal massif. It is substantiated that most promising solution of the problem of increasing efficiency of gas drainage from the massif is to mine additional gas-drainage road. This approach allows separating processes of coal mining and methane recovery in space and time. The Ukrainian normative documents is recommended to mine the road behind zones with high rock pressure. We found that in difficult conditions of coal seam mining, distance from road to working long wall would be more than 100 m. This distance reduces efficiency of gas drainage and is not economically feasible due to significant length of gas-drainage boreholes and air breakthroughs. Therefore, gas-drainage road should be located as close to the working long wall as possible, but with possibility to ensure its stability during its entire service life. Experimental studies were conducted in Zasyadko Mine and Krasnolymanska Mine. It is established that with increasing distance from working wall to the gas-drainage road location in the massif, unloaded by the under working displacement, the road contour decreases, and methane flow rate increases in power dependencies. Use of these results will make calculation of the gas-drainage road rational location more accurate.

The results of experimental research of the parameters of methane capturing by local degassing wells in the undermining area

The article is devoted to the analysis of the results of the mine instrumental measurements of the local degassing system of the m3 seam on the horizon of 1100 m of the mine named. V.M. Bazhanov to establish the basic rational parameters with the subsequent application of the biotechnological method of reducing the concentration of methane. As a result of mine instrumental measurements (vacuum-gas surveys at the borehole heads), the parameters of the degassing process (methane flow rate at the borehole heads and the average vacuum on them), technological parameters (angle of turn and tilt of wells, their length), well flow rate efficiency from the distance to the bottom of the longwall and the displacement of the undermined rocks. Establishing the basic parameters of degassing will allow you to quickly manage the flow rate of wells and underpressure at their mouths, taking into account the specific mining and geological and mining conditions. The use of biofilters allows controlling the concentration of methane in the atmosphere of mine roadway by methanotrophic bacteria.

Luminescent Properties of SiC Thin Film Deposited by VHF-PECVD: Effect of Methane Flow Rate

Bulk silicon carbide (SiC) as light emitter is less efficient due to its indirect bandgap. Therefore, nanosized SiC thin film fabrication approach enable emission wavelength shifts due to spatial confinement. The result of luminescent study of SiC thin film deposited via very high frequency plasma-enhanced chemical vapour deposition (VHF-PECVD) are presented. Precursor gasses used were silane and methane. Methane flow rate was varied from 8 sccm to 20 sccm while other parameters were maintained. Raman spectral analysis denotes the quantum confinement effect occurrence in proportion to the methane flow rate increment. The luminescence properties of the deposited SiC thin film ranging from highly green emission (~518 nm) to highly UVB emission (~294 nm) dominant luminescence. Broad blue emission band shifted toward higher wavelength with smaller FWHM as methane flow rate is increased. This results enable the possibility of luminescent SiC thin film applications in photonics and electronic integration as blue light sources.

Preparation and Microstructure, Mechanical, Tribological Properties of Niobium Carbide Films

Niobium carbide films was deposited by direct current reactive magnetron sputtering on Si (001) substrates in discharging a mixture of CH4/Ar gas. The effects of growth temperature (Ts) and methane flow rate (FCH4) on the phase structure, composition, mechanical and tribological properties for NbCx films were explored. For the film grown at FCH4=6 sccm, a phase transition from cubic-NbC phase to hexagonal-Nb2C phases occurred with increasing the Ts; In contrast, when the film deposited at FCH4=16 sccm, only the cubic-NbC phase was observed at different Ts. The surface of all the films became rough with increasing the Ts. In addition, when the Ts increased from RT to 600 °C, the films exhibited the compressive stress and kept rising. While as the Ts > 600 °C, the stress partially relaxed both at FCH4=6 sccm and FCH4=16 sccm. The hardness (H) for sample grown at FCH4=6 sccm first increased up to a maximum value, and then decreased with increasing the Ts. And the films grown at FCH4=16 sccm kept decreasing with the maximum super-hard value of the filmsof 40.5 GPa at FCH4=6 sccm and 600 °C. The friction coefficient for the film obtained at FCH4=16 sccm was lower than that at FCH4=6 sccm, which might be due to the presence more carbon in the film grown at FCH4=16 sccm.

Methane Leak and Loss Audits of Natural Gas Fueled Compressor

Natural gas reserves within the United States continue to rise. According to the Energy Information Administration, dry natural gas reserves increased by ten percent from 2010 to 2011, while wet natural gas reserves increased by 38% in 2011. Natural gas consumption also increased from 24.09 trillion cubic feet (TCF) to 24.48 TCF over the same period. As the natural gas supply, demand, and industry continue to grow methane losses across the supply chain will be inevitable. Since methane is a potent greenhouse gas, many studies are currently analyzing the loss of methane from the wells to the end user. As natural gas transmission systems grow there must be an increase in natural gas compressor and storage facilities. Currently, there is not a detailed inventory describing the emissions associated with natural gas compressor system engines in terms of the emissions resulting from engine unit losses and leaks. Researchers from West Virginia University’s Center for Alternative Fuels, Engines, and Emissions (CAFEE) recently conducted methane leak and loss audits at five compressor stations with a special focus placed on the engine and compressor units. These audits focused on identifying and quantifying the leaks and losses associated with the engines and compressor units of a typically operating site. A micro dilution high volume sampling system was used in conjunction with a portable methane analyzer to quantify leaks and losses. Bag samples of exhaust gas and engine operating parameters were used to calculate the methane flow rate from the reciprocating engines and turbines used to operate compressors at these sites. Leaks are defined as unintended methane releases from components not designed to emit methane. Losses are defined as methane releases that are known to exist or exist by design.