As the world's largest coal producer, China's vast coal-producing areas are piled up with gangue, which is becoming a glaring "black scar". The annual increase of more than 700 million tons (calculated based on 4.2 billion tons of raw coal production × 17% gangue content), 7.5 billion tons of historical stockpiles, and 18,000 hectares of land devoured, behind these figures are the dual dilemmas of environment and economy. Among them, Shanxi, Inner Mongolia and Shaanxi account for 63%. The inefficiency and high cost of traditional sorting technology have caused the treatment of gangue to fall into a vicious cycle of "more treatment and more accumulation". However, with the breakthrough of X-ray intelligent sorting technology, a revolution to reshape the logic of the industry from the source is quietly taking place.

"Black resources" stuck by technology

Gangue is not worthless waste. Its composition of 15%-30% residual coal, 40%-70% aluminosilicate and 3%-8% pyrite can theoretically be converted into power generation fuel, building materials raw materials and even rare metal extraction sources. But in the past, backward sorting technology kept these potential values dormant - the average daily processing capacity of manual sorting was only 400 tons, and wet sorting consumed 3 cubic meters of clean water per ton and produced high-salt wastewater. What's worse, the extensive process with a sorting accuracy of less than 65% resulted in a high content of residual coal in the gangue. A building materials company in Shanxi once calculated that the expanded clay produced by traditional gangue sorting had a 37% drop in expansion rate due to excessive coal content, and the product qualification rate was less than 50%, resulting in a loss of 80 yuan for each ton produced.

The heavy hammer of the policy accelerated the reshuffle of the industry. The new version of the "Management Measures for the Comprehensive Utilization of Coal Gangue" in 2023 will increase the landfill disposal tax from 5 yuan/ton to 20 yuan/ton, and at the same time require the completion of ecological restoration of half of the stock gangue mountains by 2025. For coal mining companies with annual profits of less than 1 billion yuan, this means that the cost of handling each ton of gangue has increased by 4 times, and the traditional landfill model has completely lost its living space. The industry is at a crossroads: either find a way to break through the technical situation or be crushed by the environmental burden.

Technology awakening under X-ray penetration

In a modern coal preparation plant in Inner Mongolia, MINGDER Optoelectronics' X-ray intelligent sorting equipment is rewriting the rules of the game. When the gangue enters the detection area, MINGDER Optoelectronics' X-rays combined with high-precision dual-energy acquisition and transmission technology instantly penetrate the material and accurately capture the subtle differences between coal and gangue. With MINGDER's self-developed intelligent sorting technology for identification and sorting, this system is like a "full body check" for each piece of ore.

"In the past, manual sorting relied on experience, and now algorithms rely on data." The technical director showed the sorting map on the control screen: models were generated for high-sulfur gangue, low calorific value coal, and high calorific value clean coal. The deep learning model stabilizes the sorting accuracy at more than 98.3% by continuously learning the coal quality characteristics of different mining areas, and the processing capacity can reach more than 100 tons per hour without consuming a drop of water. More importantly, the lower limit of the sorting particle size is compressed from 25 mm in the traditional process to 10 mm, which means that more fine gangue can be removed in advance.

The economic benefits brought by this technological breakthrough are immediate. After a coal mine in Inner Mongolia introduced the equipment, the clean coal yield jumped from 68% to 73%, and the ash content decreased by 1.7 percentage points. The premium per ton of coal brought by the improvement of the quality of commercial coal alone exceeded 40 yuan. What is even more surprising is that the coal content of the gangue after sorting is less than 2%, and the calorific value drops sharply from 2800kcal/kg to below 1200kcal/kg, which directly meets the production requirements of brick making and paving aggregates.

Transformation from cost center to profit center

If the intelligent sorting equipment is placed in front of the main washing system, it is like installing an "industrial CT" on the production line. The original 25-300 mm raw coal, after the pre-discharge of gangue, the amount of gangue mixed can be reduced by 38%, and the ash content of clean coal can be reduced by 1-2 percentage points. Then enter the heavy medium sorting system. This "double insurance" model not only stabilizes the ash content of clean coal below 8.5%, but also reduces the medium consumption by 40%, saving 280,000 cubic meters of water annually. The more far-reaching impact is that high-purity gangue begins to create new value - the silicate content of gangue after sorting reaches 72%. When it is directly used to produce geopolymer cement, the 28-day compressive strength reaches 42.5MPa, and the cost is 22% lower than that of traditional cement.

Companies with a keen sense of the market have begun to lay out a closed loop of resource utilization. A company in Shanxi, based on the fact that local coal gangue contains a large amount of kaolin resources, introduced MINGDER artificial intelligence sorting machines for sorting, selected high-quality kaolin and sold it directly, with a product gross profit margin of 35%. A mining area in Shandong even explored selecting kaolin from gangue, opening up a new profit growth point. Data shows that when the sorting accuracy exceeds 90%, the cost of gangue resource utilization can be lower than that of natural aggregates, which means that a market worth hundreds of billions is being activated.

Reconstructing the new logic of the coal industry

The impact of this technological revolution has long gone beyond the scope of environmental protection. The application of pre-sorting systems in mining areas can increase the raw coal washing rate from 65% to 90%, and reduce ineffective transportation energy consumption by 18%; the promotion of dry sorting technology has reduced the carbon intensity of coal preparation plants from 8.9kgCO2/ton to 3.2kgCO2/ton; the emergence of professional sorting service providers has spawned a new business model of "charging by ton".

The resonance effect of policy and technology is emerging. The market penetration rate of intelligent sorting equipment was only 12% in 2023, but the industry predicts that it will exceed 35% by 2025. There is greater room for imagination. With the breakthrough of the lower limit of sorting particle size and the improvement of identification accuracy, coal gangue may become an important raw material for the preparation of soil conditioners in the future.

Standing in the gangue accumulation warehouse of Pingshuo Coal Mine in Shanxi, all you can see is gray-black accumulation. But under these "industrial ruins", a value reconstruction driven by technological innovation has already started-the former pollution source is being transformed into a "new rich mine" for green mines. This may confirm the eternal truth: in the script of industrial transformation, there is never real waste, only value that has not yet been discovered.