Improving mine drainage pumping capacity is one of the important requirements for coal industry units to ensure safe and effective production. In open-pit mines in Quang Ninh, the pumping equipment being used all have large capacity, high discharge height and forced pumping method to drain water from the bottom of the mine. In underground coal mines, the pumping systems are also automated and synchronized with control technology, detecting all risks of water bursting and mine flooding.
At a depth of approximately -300m above sea level, in previous rainy seasons, the Deo Nai coal mine of Deo Nai - Coc Sau - TKV Coal Joint Stock Company had a water reserve of around 6 million m3 . However, this year's rainy season with prolonged heavy rains, rainfall exceeding forecasts, the amount of water accumulated in the mine was at times higher than 6 million m3 .
"To treat this amount of water, Deo Nai mine is currently using 6 pumps with a capacity of 1,250m3 /h from the bottom of the mine to the intermediate level of -50m and up to the centralized wastewater treatment system at +90m above sea level. In terms of technology, Deo Nai Coal's pumping systems all use advanced pumping technology, centralized soft start control and are automated, interlocked in each pump row from lower to upper levels by wifi waves" - Mr. Nguyen Van Minh, Manager of the Electromechanical Equipment Repair Workshop, Deo Nai Coal Joint Stock Company - Coc Sau - TKV said.
The characteristic of open-pit mines in the coal industry is seasonal mining. In the rainy season, the upper layers are mined, and in the dry season, the mine bottom is dug deep to get coal. On the other hand, the mining area of open-pit coal mines is organized below the level of natural drainage. To dig deep into the mine bottom to get coal, the units will deploy the method of forced pumping, pumping out water and cleaning up the mud deposited at the bottom of the mine after each rainy season.
Large-sized mines will have intermediate pumping stations on the mine shore and use 2-stage pumps. Limited-sized mines will use serial pumping technology to pump from the bottom of the mine to above the gravity drainage level. Depending on actual requirements, pumps used for mines have flow rates of 560-800m3 /h and 1,040-1,260m3 /h; some mines also use large-capacity pumps with flow rates of 1,400m3 /h, 2,000m3 /h and mud pumps with flow rates of 400m3 /h.
As for underground coal mines, mine drainage is one of the three important tasks along with preventing mine gas explosions and controlling mine pressure. Therefore, units will proactively identify water sources from water-containing areas on the surface of the terrain such as: Rivers, streams, ponds, open-pit mines, waste dumps that are in operation or have ceased operation; subsidence and cracking areas. Notably, underground water-containing areas such as: Water-containing strata, geological boreholes, exploited areas, old mine systems, faults; overlapping mining areas between mining units.
Currently, the underground mining area of Lo Tri area of Thong Nhat Coal Company is located under the open-pit mine of Khe Sim Coal Company under Dong Bac Coal Corporation. Every year, the two units regularly coordinate in the treatment of Khe Sim mine water, in order to minimize the amount of surface water that seeps into the underground coal mining areas of Thong Nhat Coal Company.
According to Mr. Do Tuan Anh, Deputy Director of Thong Nhat Coal Company - TKV, the recent storm No. 3 caused the water level in the open pit to rise, while the national power grid was interrupted due to the storm's impact, making it very difficult to pump and drain water in this area. To treat Khe Sim pit water and limit the amount of surface water flowing down the mines in Lo Tri area, Thong Nhat Coal Company had to mobilize the Company's pumping systems, coordinate with the pumping system of Khe Sim Coal Company and arrange generators to ensure continuous water pumping. Thanks to that, immediately after storm No. 3 passed, Thong Nhat Coal quickly stabilized production again and produced coal on September 10.
Every year, to ensure the effectiveness of underground water treatment, mines have implemented many measures to explore and identify areas and water storage points to proactively eliminate the risk of water affecting production areas early. However, with the current complex climate change situation, mine drainage plans must be implemented with a higher contingency factor. In fact, the historic rain in 2015 and most recently, storm No. 3 and its circulation after the storm, record-breaking rainfall and serious impacts on production power systems have caused some mines to fail to meet drainage requirements. Therefore, coal mines in Quang Ninh need to further improve their water pumping capacity, ensure the operation of power systems, and effectively implement measures to prevent flooding during production.
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