Coal Drying at the Mine Rather Than the Power Plant – Does It Make Sense

With India importing large amounts of high moisture low rank coal, there is growing interest in the potential benefits of drying the fuel prior to combustion. But what is the best way of doing this? Are there advantages in drying the coal at the mine before transportation to the powerplant site? The analysis presented here looks at the add-on benefits of coal drying at the mine end relative to drying at plant sites, but is agnostic as to the particular coal drying technology employed.

It is well known that moisture is a major cause of thermal losses in coal fired boilers. Therefore reduction of the moisture content in coal improves boiler efficiency. Reduction of coal moisture also facilitates coal handling and coal preparation. Drying of high moisture coal to reduce its moisture content and thereby improve boiler performance is a well established concept in principle but when it comes to the practicalities there are uncertainties about the most suitable drying processes and the economics, currently topics receiving attention. Few powerplants around the world using one or other of the available drying methods to reduce the coal moisture, there are also trials underway at power plant sites and at laboratories to find the most appropriate technologies for coal drying. In India, at present high moisture coal is fired mostly in ‘as received’ condition without drying. Nearly all studies of coal drying conducted to date assume that the coal will be dried at the plant site. It means high moisture imported coal would be transported all the way to the plant site and then dried using fuel or waste heat, if available. In other words, enormous quantities of water are transported to the plant and then energy is consumed to evaporate the water. Considering the quantity of water that is transported as coal moisture, and taking into account shipping distances, transportation costs and fuel consumption, it may be worth looking at another scenario: what if the coal is dried at the mine mouth and then transported? Would this make sense? The issue is examined in the Indian context, but the findings are applicable elsewhere as well.

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