1、Journal of Mining Science, Vol. 47, No. 4, 2011MINERAL MINING TECHNOLOGYCHARACTERISTICS OF METHANE RELEASEIN HIGHLY PRODUCTIVE COAL MINESK. N. Trubetskoy, A. D. Ruban, and V. S. Zaburdyaev UDC 622.817The article discusses the research of methane release intensity versus average daily output in coal
2、mines featuring different geological and mining conditions in Vorkuta and Kuznetsk Coal Basins. The authors describe degassing of producing and superimposed methane-bearing coal beds in highly productive longwalls, at the stages of coal face output of 26 thousand tonnes per day and in the first mont
3、hs of operation.Coal bed, mine, working site, longwall, methane content of coal bed, coal production, methane release The volume of methane release, given the present-day depth reached in underground coal mines, is de facto 1820 m3/t or 4 13-14 kg/t 1, which appreciably affects production rates and
4、profitability of underground extraction of high methane coal. It is extremely important to promptly prepare coal beds for extraction, ensure sufficient airing of headings and entries, plot efficient degassing measures to reduce methane flow in headings and entries as well as to recover standard qual
5、ity methane from utilizable gas-air mixtures. Without implementation of the above listed measures in, it would be impossible to efficiently take advantage of high-production coal-winning machines in fully mechanized headings during high methane coal extraction, while the share of the fully mechanize
6、d mine workings is 89% in Russia. Apart from standard ventilation, gas-saturated fully mechanized headings must involve a package of special methods and schemes for degassing of producing and superimposed coal beds, at maximum possible efficiency in the specific mine conditions: not less than 30% de
7、gassing efficiency in producing coal beds, 7080% degassing efficiency in superimposed coal beds and mined-out spaces. The coal mine ventilation analysis shows often negative stability of airing in working areas, and instances when working areas become gassy in Russian mines total 840980 per year on
8、average 2. Effective degassing measures reduce over-gaseousness in mines and enhance safety of high methane coal extraction. Effective degassing must be in the limelight when planning abatement of methane emanation from producing and superimposed coal beds into face areas, according to recommendatio
9、ns RD-15-09-2006 3 Actual gas testing data on core materials extracted in mines of the Kuznetsk Coal Basin (Kuzbass) show that coals of different ranks, occurring within depth range 100750 m have considerable discrepancy in methane content limits (see Table 1). Average relationship between coal meth
10、ane content (m3/t, dry ash-free basis) and coal occurrence depth (m) may be presented empirically as follows: X = 0.05H - 2.5 , (1)which implies that methane content in coal beds expands by 5 m3/t, dry ash-free basis, per every 100 m of depth and upper methane limit is averagely at a depth H0 of 50
11、m from daylight surface. The present research authors have calculated X = f (H) for the largest mines in Kuzbass, based on the actual data obtained in methane content tests of core material 4. Methane content of a coal series influences the intensity of methane release into headings 4, which is also
12、 governed by the coal production rate in a mine as is illustrated by the curves of the actual average daily coal output versus methane emanation in a number of the Kuzbass mines in Fig. 1. Let us take, for example, coal bed Boldyrevskii (coal bed 24): its methane content = 15.2 m3/t, dry ash-free ba
13、sis (this indication is omitted henceforth while is implied without saying), average preliminary degassing factor is 0.2 in the depth range 350400 m from the ground surface. After borehole degassing, the same coal bed had methane content X = 12.2 m3/t. Natural degassing factor in this bed was estima
14、ted as 0.69 5. Methane content in the coal cutting area was Xc = 4.2 m3/t. Volatile content at the face was Vdaf = 40%. At the coal cutter output j = 7.4 t/min, the methane emanation intensity in the cutting area was Ic = 8.9 m3/min. The data on coal outputs in mines and breakage headings, as well a
15、s methane release intensity and proportionality factors 4 show that their numerical values decrease as the daily coal output grows, both in mines and at headings. To reveal the physical meaning of this phenomenon observed in enhanced coal extraction, we need to justify it theoretically.Preliminary d
16、egassing of producing coal beds via boreholes and natural degassing of the faceadjacent coal owing to ground pressure relief substantially decrease gas content in the coal cutting area.Table 1. Gas content limits in coal beds in Kuzbass by methane content tests of core material.Coal mineCoal ranking(in Russia)Coal bed (limits)Depth fromsurfa
