It was my first visit to China fortunate enough as research internship candidate. It is a very unique place especially because of the language barrier where no one knows English. Even though the younger generation is rapidly getting accustomed to English, they are still very far away from getting use to it in the normal life. The beauty of China lies in the behavior of the people where the people are too friendly. For example, if you ask for a direction, most probably they would accompany you till you reach your destination. I can go on writing about the beautiful aspects of China but I would like to mention a wonderful experience in one of the largest producing coal mines.
China is well known for its coal mining and its technological advances in the last decade. The production in China escalated in last two decades at a rapid rate. The rate can be attributed to the increased efficiency of the coal mine productions such as huge productions from one single coal mine. You may assume what's new in it, there are huge open pit coal mines producing more than 10 MT per annum in other countries. It would be interesting to know that an underground coal mine producing 30 MT of coal per year and surprisingly, it does not stand in the top 10 on the list. It stands fifteenth on the chart according to the annual coal production in China. The highest recorded annual coal production was 55 MT in china from an underground coal mine. So it raises a question how are they managing it?
China has very thick coal seams and very flat dipping upto 3°-5° inclinations. The coal seam and the roof layers are such that it is favorable to longwall mining where the width of the face is about 240m and the length of the panel is about 2km with a height of 3.5m. These specifications looks like a normal longwall mine with just a height of the face higher than usual which is 2 - 2.5m. Then question arises how are they able to produce 15 MT of coal annually. Some may say there may be large number of panels running at the same time. It is not the case, there are only two panels in operation and two panels in development. Then how??
The answer lies in the mining method "Longwall Mining with Top Coal Caving". It was a touch and go topic back in my bachelors where we studied about it but never had a practical aspect of it as we didn't have any mines with that kind of technology in my country. So how does this work?
Remember, the coal seams here are very thick which is about 20m. The coal is excavated in the bottom 3.5m with longwall mining but the remaining coal left in the roof caves in the back of the shields and recovered by conveyor at the back. It is not a magic that it starts to cave automatically, it has certain conditions that are extensively studied before adopting this method. In this mine, all the conditions are in its favor for the application of this method. From the production rate, it is estimated that 85-90% of the coal on the top is recovered which makes a huge difference in the production.
Every mine has its own problems but to tackle it and forward is what makes you successful. It was a learning experience for me. Hope everyone gets to visit these mines to watch the amazing view of the mines. Below is the picture before we entered the coal mine.
