1、翻译部分英文原文2007 China (Huainan) International Symposium on Coal Gas Control TechnologyGas Drainage in High Efficiency Workingsin German Coal MinesDr. Joachim Brandt, DMT GmbH, GermanyAbstractIn the course of increasing production in the workings of German hard coal mining, the part of ventilation techn
2、iques as a factor of production has also increasing importance. In view of still increasing production the cooling of the air is critical for the attainable production on the one hand. On the other hand, the increasing gas emissions have to be controlled as well.This is achieved by fans of high capa
3、city as well as by cross-sections in the underground workings, which are as big as possible, especially in the gateways. Furthermore, increasing cooling power is installed.The air volumes cannot be enlarged unlimited, yet, and rapidly reach their limit due to national statutory regulations concernin
4、g the maximal allowed air velocities.Besides that, a methane concentration of 1Vol.-% in the maximum must be maintained in general, which is allowed to be exceeded only with the agreement of the mining authority in defined parts of workings up to a limit of 1,5Vol.%.Due to a dense sequence of coal s
5、eams in the German hard coal deposits, the firedamp is released during the exploitation not only from the worked seam, but essentially from the seams in the roof and in the floor behind the passage of the longwall. A gas drainage on the base of an efficient technique is necessary, firstly in order t
6、o fulfil the safety regulations and secondly to achieve a maximal production in the working.An investigation, recently finished and executed concerning the improvement of the gas drainage indicated that, by means of rock mechanical calculations and interpretations, an increase in the efficiency of g
7、as drainage boreholes is still possible.IntroductionThe methane emissions in mining operation depend principally on geologic conditions. In rock sequences with a small portion of coal in the roof and the floor, only the released gas quantity from the exploited seam also defined as basic gas emission
8、 has to be diluted with the air flow. This methane flow can reduce the exploitation relevantly by an increasing desorbable gas content in the coal. In particular, the coal mass flow quickly exploited with high-capacity production can release very high methane quantities from the accompanying seams.
9、This high methane flow generates an exceeding of the threshold values and leads to switch off of the electrical equipment and to the interruption of production.In a rock sequence with a high portion of coal in the roof and the floor additional gas from the accompanying seams in the area of gas emiss
10、ions is released into the air flow behind the passage of the longwall. In the Ruhr Basin this gas flow, also defined as additional gas emission, is normally many times higher than the basic gas emission.Figure1 illustrates the loosening of layers caused by longwall mining operation in flat layers. T
11、hese loosenings can be according to their degree - flow ways for the released gas from the accompanying seams. The coloured areas mark the degree of loosening with red for intensive, dark blue for light and grey for no loosening.Figure 1: Example for the loosening of the rocks in the roof and the fl
12、oor of a longwall operation (view of the left side only; the right side is symmetric)There can be a high rate of additional gas emissions according to the seam thickness in the area of gas emissions and according to their gas content. Figure 2 shows that the production can decrease dramatically alre
13、ady at low gas contents if there is no gas drainage for the suction of the additional gas emission.This extreme reduction of saleable output and advance of production requires extreme increasing of the air flow and furthermore gas drainage is necessary. Thereby the legal regulations for the German h
14、ard coal mining have to be observed, which are the following:maximum air velocity6m/smaximum methane concentration1Vol.-%exceptional methane concentration1,5Vol.-%minimum negative pressure in the gas drainage100hPaFigure 2: Example for the decline of production in case of (increasing) additional gas
15、 emissionImprovement of the gas drainage for maximising the output After increasing the air flow following the legal regulations, and with the permission by the authorities for maximum methane concentrations of 1,5 Vol.-%, and after commissioning a gas drainage system, the output can be increased to
16、 a quantity, which is again profitable (see figure 3).Normally, the efficiency of the gas drainage system is up to 50% of the total methane flow occurring during exploitation. An additional optimising of the gas drainage above that also increases the face output.A longwall in seam H of the mine Prosper Haniel serves as an example for optimisi
