Waste gangue represents a headache for all coal mines – it contaminates product, wastes hoisting capacity, and piles up on the surface as an environmental liability.
Yangcheng Coal Mine in Shandong, China, faced an even greater challenge. Raw coal ash content reached 42.08%, and approximately 4 Mt of coal reserves were trapped beneath surface buildings – unrecoverable by conventional methods. The mine produces 350,000-400,000 t of gangue annually, straining the main shaft and creating dust, leachate pollution, and land occupation.
The traditional solution would be to hoist it up and dump it. However, MeiTeng Technology, together with Haina Technology and China University of Mining and Technology, took a completely different approach – one that keeps everything underground in a closed-loop system.
The solution was a fully underground integrated sorting and backfilling system. MeiTeng designed a customised underground intelligent sorting with longwall panel-by-panel cemented backfilling solution for Yangcheng. Construction began in early 2024 and the system entered service in December 2024.
At the core of the system is an underground XRT intelligent dry sorter, which uses X-ray and optical recognition to separate coal from gangue in the 300-400 mm size range. Key performance indicators include a gangue rejection rate of ≥90% and coal loss in reject of ≤3%.
The separated gangue never goes to the surface – it is directly fed into the backfilling process underground. The system consists of a surface slurry preparation station and an underground backfilling system.
At the surface station the mix design has a 78.5% concentration, with 50% gangue solids, 9% cement and 20% fly ash. The capacity is 100 m³/h, with delivery via two slurry boreholes and one material feed borehole (339 m deep).
For the underground system, key equipment includes a high-fineness crusher (gangue to <10 mm), continuous mixer and backfill industrial pump, with a system capacity of 150 m³/h.
Yangcheng Mine applies longwall panel-by-panel cemented backfilling in a 7.8 m thick coal seam. The mining area is divided into strip roadways, with a ‘mine one – backfill one’ cycle. The backfill slurry undergoes three curing stages: initial setting (4–6 hours) when it develops initial strength; curing (approx. 24 hours) when it gains significant compressive strength; then stabilisation (approximately 7 days) when it achieves design strength (>90% compaction).
Since January 2025, about 650,000 t of previously stranded coal has been unlocked and 470,000 t of high-quality coal extracted. The system consumes over 300,000 t of gangue annually, along with fly ash (150 t/d) and slag from the mine’s power plant – eliminating surface stockpiles and their ecological risks.
In terms of economic benefits, Wang Xukui, Deputy General Manager and Chief Engineer of Yangcheng Mine says the system has added annual revenue of US$45 million, with the mine life extended by 11 years. In 2025 alone the value created was US$20.5 million, with a 2026 target of 600,000 t of backfill mining.
In September 2025, the project was selected for the National Coal Mine Backfilling Mining Advanced Technologies and Practical Case Collection, recognised as a replicable benchmark for green and intelligent transformation. It was also featured by China Coal News on July 25, 2026.
Since 2018, MeiTeng Technology has built over 30 underground XRT sorting and backfilling systems across China and Central Asia, covering diverse geological conditions and mining operations.
By – https://im-mining.com/2026/08/08/meiteng-technology-powers-green-transformation-at-yangcheng-coal-mine/