In order to fully exploit resources in underground coal mining areas, in recent years, Vietnam National Coal - Mineral Industries Group (TKV) has stepped up investment and put into use suitable mechanized systems. Mechanized coal mining longwalls not only provide high productivity, output, and safety factors, but also increase coal recovery rates, reducing resource loss to the lowest level.
Vang Danh Coal Joint Stock Company - Vinacomin is one of the major underground coal production units of TKV, with an average output of over 3 million tons of coal/year, accounting for 10-15% of TKV's total underground coal output. In particular, the coal output exploited from the slope area above 45o of Vang Danh is always maintained at 0.8-1.2 million tons, accounting for 25-35% of the total output of the Company according to the types of mining technology.
To reduce the coal loss rate at the slope seams, since the end of 2017, the Company has applied the technology of exploiting diagonal longwalls, supported by ZRY soft scaffolding. "When applying the ZRY soft scaffolding, the longwall mining output increased from 110,000-120,000 tons of coal/year, and coal loss decreased to 21%. The quality of raw coal from ZRY longwalls is also always guaranteed, meeting the requirements of producing high-quality coal of the mine" - Mr. Tran Van Thuc, Deputy Director of the Company said.
However, with this technology, the amount of resources that must be left behind in the protective pillars is still relatively large, which means a large rate of resource loss. In mid-2021, Than Vang Danh continued to research the solution of extracting coal using the ZRY soft platform without leaving protective pillars, helping to increase the output of ZRY longwall coal mining and thoroughly recover resources.
The results achieved after the trial period have confirmed the success of the application of the coal recovery solution in diagonal longwalls, supported by ZRY soft supports. Since the application, the longwall mining reserves using supports have increased by 16% - from more than 134,000 tons to more than 160,000 tons; the resource loss rate has decreased from 21% to 17%, almost completely recovering coal.
"ZRY is just one of the modern technologies that Vang Danh Coal uses to exploit and recover resources in complex geological seam areas. In addition, the synchronized mechanized longwall furnace with the roof coal recovery structure that this unit is operating also produces high coal output, fully exploiting resources with a recovery rate of 90-98% - Mr. Vuong Minh Thu, Deputy Director of Vang Danh Coal Company added.
As for Mong Duong Coal Joint Stock Company - Vinacomin, the light-weight synchronized mechanized longwall that this unit has put into operation since 2020 is still the "trump card" in the campaign to increase underground coal output of the mine. Not only does it provide a high average output (300,000 tons of coal/year), the structure of lowering the ceiling to recover top coal of this light-weight synchronized mechanized system also helps Mong Duong Coal reduce the rate of resource loss.
According to Mr. Ngo Xuan Thuy, Deputy Director of Mong Duong Coal Joint Stock Company, the efficiency of coal recovery from the unit's light-weight synchronized mechanized longwall furnace is 87%, an increase of about 6% compared to old technologies under the same mining conditions. Coal recovered from these areas is almost completely. The conditions for installing this longwall furnace are seam thickness from 4-6m, slope angle less than or equal to 25 degrees and currently Mong Duong Coal is researching and selecting suitable locations to be able to replicate this technology model in the future.
Currently, underground coal mining units in TKV are using 12 synchronized mechanized lines with an annual coal output accounting for about 17.8% of the total underground coal output of the Group. In 2023, the coal output from these synchronized mechanized systems is planned to be 4.27 million tons.
According to the TKV Mining Technology and Engineering Department, from 2020 to present, the coal recovery coefficient (calculated for both the full-thickness longwall furnace and the pillar-layer longwall furnace, with top coal recovery) of the synchronized mechanized longwall furnaces in the Group has reached 73-98%, mostly reaching 80-95%. In particular, the light synchronized mechanized longwall furnaces (put into use at units including Mong Duong, Duong Huy, Uong Bi, Ha Long) show better coal recovery efficiency, reaching 80-98%, 3-5% higher than the type of mining technology supported by frames/chains.
To continue increasing productivity and underground coal output, and effectively exploiting resources, from now until 2025, TKV plans to continue evaluating and investing in 5 additional synchronized mechanized lines at a number of units: Nui Beo Coal, Thong Nhat Coal, Hon Gai Coal, Ha Long Coal, Mao Khe Coal and investing in replacing 2 synchronized mechanized lines at Ha Lam Coal and Khe Cham Coal.
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