Determination of methane content and methane released when exploiting longwall at different levels at 13.2 seams, Khe Cham coal mine, Vietnam

Khe Cham coal mine is managed by Ha Long Coal Company TKV. Currently, Khe Cham coal mine is exploited from the ground up to 350 and is ranked III for methane. In 2008, a methane explosion at -168 level of the 13.2 coal seam of Khe Cham coal mine occurred, injuring 16 people and killing 8. In order to avoid gas explosions at mines like 2008, it is necessary to have appropriate solutions to eliminate methane accumulation in the pit paths. We have studied to determine the relationship between the level of methane emissions with the methane content in the coal seam and the bazaar's mining output because of the methane content in the coal seam and coal mining output. These are the two factors that greatly affect the release of methane from the longwall. The paper used practical measurement, sampling, and analysis methods to determine the level of methane emissions from longwalls at different extraction levels of the 13.2 coal seam and determine the relationship between the methane drainage and the methane content in the coal seam and the exploitation output of the longwall. This relationship is expressed by the equation y = a.x + b.x + c (Fig. 2 and Fig. 3). The results will help with planning for mining and have specific solutions for diluting methane in the mine's pit lines


Introduction
Khe cham underground coal mine is located in MongDuong town, CamPha city, Quang Ninh province, Vietnam. The North, it borders on Duong Huy commune; The East, it borders on Quang Loai, Mong Duong commune; + The South, it borders on KheSim, Coc Sau, Deo Nai, Lo Tri; The West, it borders on KheTam coal mine Do not add any page numbers. The Nitrogen-Methane Zone: mainly distributed from the surface up to + 40m; The methanenitrogen zone: mainly distributed from + 40m to -150m. The Methane zone: mainly distributed from -150 and below. In some places like Cao Son, the surface of the floating methane zone is up to + 50m, in the South of Da mai subdivision at -50m and gradually raised to + 50m in the southwestern part of the mine. In the part of Khe Cham, the methane zone is at -100m and sinks up to the Northwest.

Characteristics of the methane content of Khe Cham coal mine
Survey measurement data on the gas content of coal seams at different levels, the monthly coal mining output, and the ventilation of the longwall at coal seam 13.2 of Khe Cham coal mine 1 are presented at The following tables: 13. At the coal seam 13.2, there are 7 longwalls with different levels from -25 to -210 during 10 years. We have synthesized the measurement data of methane release at the times of each longwall when the extraction took place.
The methane concentrations in coal seams were sampled at seam 13.2 and brought back to the lab for VARIAN gas chromatography analysis. The methane content results at different levels of coal seams 13.2 are presented in tables 2, 4, 6, 8, and 10.
The wind flow in the tunnels of mine (Q) and methane concentrations in the airflow (C) were measured directly at the mine's tunnels. The absolute methane release (I) is determined by the following formula: [2] I=  To determine the relationship between the emitted methane concentration and the methane content in the coal seam and the mining output of the 13.2 coal seam at Khe Cham 1 coal mine, we used Microsoft Excel software to build the chart variation in production and methane emissions according to each mining month of each long wall. [4] From there, determine the regression function showing the variation in yield and methane release, and at the same time build a chart showing the relationship between methane content and methane emissions [5]

Conclusion
Analyzing the effect of the methane content of coal seams on the absolute and relative methane gas release, we can confirm that: 1. The absolute methane clearance increases and decreases in accordance with the tendency of the increase and decrease of the storage capacity methane gas in coal seams. 2. Relative methane emissions also increased or decreased proportionally with an increase or decrease in coal seams' methane concentrations. In the same long wall, when production increases, absolute methane release increases, and when production decreases, absolute methane release decreases. Thus, the absolute methane emissions increase and decrease in the same direction as the longwalls' output.
In the same long wall, when the output of a longwall is increased, the relative methane release decreases, and when the output of the longwall is reduced, the relative methane release increases. Thus, the relative increase in methane emissions in the opposite direction of the increase and decrease of longwalls output.