Methane Content Estimation in DuongHuy Coal Mine

Methane hazard has always been considered for underground coal mining as it can lead to methane explosion. In Quang Ninh province, several coal mines such as Mạo Khe coal mine, Khe Cham coal mine, especially Duong Huy mine that have high methane content. Experimental data to examine contents of methane bearing coal seams at different depths are not similar in Duong coal mine. In order to ensure safety, this report has been undertaken to determine a pattern of changing methane contents of coal seams at different exploitation depths in Duong Huy underground coal mine.

1 Introduction to DuongHuy coal mine [1,3] DuongHuy coal mine located in Duong Huy commune, Cam Pha city, Quang Ninh province.Duong Huy coal mine has an area 3,6 km 2 , within the limits of the coordinates (HN72 coordinate system, Vietnam): X: From 27.600 to 30.000 Y: From 421.500 to 423.000 -The North, it borders on Mine Construction Company -The East, it borders with KheCham coal mine -The South, it borders on 86 coal Company -The West, it borders with Khe Tam coal mine The expected output of Duong Huy coal mine in 2017 is 1,400,000 tons/year.
2 Coal sampling and methane gas analysis sequence [2] At the coal seams of Duong Huy coal mine, drill holes into the coal seams.When drilling to a depth of 2.5 m, stop drilling.Take samples of coal from the whitewalls at the bottom of the borehole, with each bore taking two samples.The first specimen was taken at a long of 2.5, with the second sample taken at a long of 4.5 m.Choice of particle size from 1 to 2 mm.Samples of coal are fed to the vibrating mill for grinding, the coal sample is crushed by the marbles in the cylinders as they move up and down.Maximum grinding time is 5 hours.
After grinding, the gas is separated from the coal sample by the MOD-1 gas separator.All the gas in the coal sample jug is separated and transferred to the sample bag.Gas separation parameters are used to calculate exactly the volume of gas to be extracted.
The specimen after being separated by MOD-1 was introduced into an analytical gas analyzer (Fig. 1) to determine the volume of methane contained in the sample.The extracted gas composition was analyzed by VARIAN gas chromatography.Analysis results from the VARIAN machine will determine the volume of methane gas from each sample of coal (Analysis results are presented in Section 3).From the results of the analysis, establish a relationship between the trend of methane density and the depth of the coal seam by using Excel software to construct methane gas prediction graph (the least squares method).Results of methane content forecast are presented in Section 4.

Reasults of analysis of methane content in Duong Huy coal mine
The results of the analysis are shown in Table 1 to Table 4 with the corresponding coal seams.

Table 4 .
Analysis results CH4 at No. 7KN, No. 9KN and No. 12DB coal seamFrom the methane content figures in Tables 1 to Tables 4. We use Excel software to graph the gas variability at different levels of coal seams.
The results of the analysis are shown in table 5 to table 8, and Figure2to Figure13with the corresponding coal seams.