Application of mechanization in coal mining

0 Introduction
In the production process of a mine, the sophistication of the coal mining technology directly affects the overall production capacity of the mine. Therefore, it is essential to select advanced coal mining technologies to achieve high production and efficiency. With the development of industrial control automation technology in my country, the application of electromechanical automation in coal mines is increasing. Because coal mining is a high-risk industry, improving the safety, reliability, and automation level of electromechanical equipment, and minimizing manpower, is key to achieving long-term stability and safety in mines. Therefore, the automation of coal mine electromechanical systems has powerfully promoted the safe, efficient, and rapid development of enterprises.
1. Application of Integrated Mechanized Coal Mining Technology
The most advanced coal mining technology in the world is fully mechanized coal mining, or "comprehensive mining" for short. The reason why comprehensive mining is advanced is that all five major production links, namely breaking, loading, transportation, support and disposal, have been mechanized, reducing the intermediate human involvement and improving labor efficiency.
1.1 Equipment Characteristics The development direction of underground coal mining is to achieve high-yield, high-efficiency, and centralized production in mines. The prerequisite for achieving high yield and efficiency is to increase the output of fully mechanized mining faces, achieving high yield and efficiency at each face, and reaching a high degree of centralized production with one or two faces per mine. Achieving high yield and efficiency in fully mechanized mining faces aims to increase the mining intensity and the effective operating rate of the coal mining machine. Technical approaches include increasing the hourly production capacity of the supporting equipment at the fully mechanized mining face; increasing the number of coal extraction points at the face; improving the reliability of fully mechanized mining equipment and the mine production system; and reducing the impact time of auxiliary processes at the face. Achieving high yield and efficiency in fully mechanized mining faces mainly involves achieving high yield and efficiency in single longwall fully mechanized mining faces and achieving high yield and efficiency in fully mechanized top-coal caving faces.
The adoption of high-capacity new fully mechanized mining equipment to achieve high production and efficiency in long-term fully mechanized mining faces is also the future development direction of coal mining mechanization. The main characteristics of this equipment are: large capacity. High-power (>800kW) electric traction coal mining machines have an hourly production capacity of over 1000-1200 tons, while conveyors, transfer conveyors, and crushers have an hourly production capacity of over 500-2000 tons; high degree of automation, achieving mechatronics integration; to meet the requirements of rapid coal cutting, the coal mining machines have automatic height adjustment functions; the hydraulic supports adopt electro-hydraulic control, enabling automatic control of the coal mining machine, scraper conveyor, and hydraulic supports; and good equipment performance and high reliability.
1.2 Fully mechanized coal mining technology: Longwall mining is a coal mining method that the Balanbu Mine has achieved good economic benefits in the past 10 years by utilizing complete sets of fully mechanized mining equipment from China. Its working face roadway layout only includes return airway, transport airway, and cutting face, with a well-developed and efficient ventilation system. Generally speaking, increasing the length of the fully mechanized mining face increases the amount of coal cut per pass by the coal mining machine, correspondingly reducing the time spent on production due to processes such as face sloping and end-face operations, thus achieving higher output. Determining the reasonable length of the fully mechanized mining face is generally based on maximizing daily output or minimizing cost per ton of coal. The main factors limiting the length of the working face are the geological conditions of the working face and the length of the scraper conveyor. Increasing the advance length of the working face is the most effective way to reduce the number of times the working face needs to be moved. The main factors limiting the increase in the length of the working face are the excavation and support of the return roadway, the length of the extendable belt conveyor, and the geological structure of the mining area.
The application of shortwall fully mechanized coal mining technology is mainly based on two conditions: the realization of mechanized and rapid excavation of the mining roadway and the realization of rapid operation at the upper and lower ends of the fully mechanized mining face. This coal mining technology is suitable for small and medium-sized mines mining gently dipping medium-thick and thick coal seams, as well as large mines mining coal seams with small mining blocks that are not suitable for longwall mining faces.
Short-longwall fully mechanized mining is a new type of coal mining method that involves setting up longwall faces within existing roadway pillar-type development areas and using fully mechanized mining equipment to recover coal pillars. The Balambu Mine in India purchased fully mechanized mining equipment from China and conducted trials on the 63L short-longwall fully mechanized mining face. During the trial, 102,415 tons of coal were extracted in 65 days, with an average daily output of 1,300 tons and a peak daily output of 2,000 tons, showing significant improvements in efficiency and extraction rate. Practice has proven that short-longwall fully mechanized mining has broad prospects for promotion in India and also has reference value for small and medium-sized coal mines in China transitioning from pillar-type mining to longwall fully mechanized mining. The production process of top coal caving mining in a fully mechanized mining face is as follows: the coal mining machine first cuts, moves, and pushes the conveyor; after 2-3 cuts, coal cutting is paused, and the top coal is released section by section through the opening of the coal caving windows on the supports. When gangue appears, the coal caving windows are immediately closed; this process continues until all the top coal along the entire length of the working face has been released, thus completing one coal caving cycle. After the top coal is released, the longwall mining face can continue to advance.
With the significant increase in the level of comprehensive mechanization and intensive mining in coal mines in recent years, coal seams with better mining conditions in original coalfields are gradually being depleted. The mining of thin coal seams, which account for a large proportion of total recoverable reserves, has been put on the agenda, and the issue of comprehensive mechanized mining of thin coal seams is also facing challenges. In my country's coal mines, thin coal seams account for a large proportion of recoverable coal reserves. In proven mining areas, 84% of the mining areas have thin coal seams, with reserves of approximately 62 billion tons, accounting for 17.5% of the total reserves. Because thin coal seams are difficult to mine, the level of mechanization has always been relatively low, resulting in a small proportion of output from mined coal seams. In thin coal seams, the selection of mining methods is a challenge due to the thinness of the seam and the limited space for personnel movement. Traditional mining techniques typically use drilling and blasting at the working face, which results in low output and poor safety. To improve the output per unit area and the efficiency of the working face, and to achieve safe and efficient mining, comprehensive mechanized mining must be adopted. Expanding the application scope of fully mechanized mining, improving its economic benefits, and achieving high-yield and high-efficiency coal production are important goals of the coal industry's technological development, and play a crucial role in the sustainable development of coal mines.
2. Application of Electrical Automation in Mechanical Equipment
Coal mining machines have evolved from those used in medium-thick coal seams to high-power, high-extraction drum mining machines for thin coal seams. From chain-driven and chainless hydraulic traction methods, they have gradually developed into electromagnetic slip chainless electric traction and variable frequency speed-controlled chainless electric traction. The height of hydraulic supports has varied from thin, medium-thick to thick coal seams, and the support types have evolved from the dominant shield type to various types, including four-pillar support for low-level top coal caving, two-pillar support for high-level top coal caving (single conveyor), and two-pillar shield type for low-level top coal caving. Electro-hydraulic control systems for hydraulic supports are widely used in developed coal-producing countries such as the United States, Australia, and Germany. These systems are key technologies for achieving high production and efficiency in fully mechanized mining faces and represent the inevitable direction for future development, fully leveraging the role of mechatronics technology in coal mining. Currently, considering the technical, economic conditions, and benefits of domestic coal mines, electro-hydraulic controlled hydraulic supports are mainly used in longwall mining faces with an annual output of over 4 million tons, top coal caving faces with an annual output of over 6 million tons, and high-efficiency mining faces in thin coal seams. Within two years, we will try out the first set of electro-hydraulic control system for hydraulic supports, taking into account the characteristics of each mine.
The application of electrical automation makes the coal mining process more humane. The reliability of remote monitoring and expert diagnostic systems for fully mechanized mining face equipment is a major focus of research on domestically produced coal mining machines. This system enables remote monitoring of the hydraulic supports and coal mining machines, allowing the machines to automatically cut coal based on changes in the coal seam, automatically adjust the mining speed according to the seam's hardness, verify and improve dynamic monitoring of the hydraulic system pressure and stress points of the fully mechanized mining supports, and automatically adjust the movement of the support-pushing conveyor. Recent project research and selection work is underway, in collaboration with research institutions, at the Dongpang Mine. The focus is on resolving issues related to online monitoring, fault diagnosis and prediction, display and transmission systems, and automatic operation control systems for the coal mining machines. This will elevate the overall level of mechanization to a new level.
3. Conclusion
Building high-yield and efficient mines is the only way for coal enterprises to survive and develop, and a fundamental approach to enhancing their overall competitiveness and sustainable development. The application of integrated mechanization in coal mining has yielded significant economic and social benefits, while simultaneously realizing high-yield, high-efficiency, and modernized coal mines.