Pre heat coal before burning
The update of your question changes everything!

In Germany, around 25% of the base load is generated in lignite-fired power plants.
Lignite (brown coal) is awfully wet (50% water) and it is definitely a good idea to apply drying. 

In the power plants, powdered lignite is used. Traditionally, the milled lignite is dried using the hot exhaust gas at temperatures up to 1000 °C, but modern plant like the one in Niederaußem operated the fluid bed drying at temperatures as low as 110 °C.

In summary, pre-drying of lignite is a good idea, if not essential, but it open to question how efficient the drying process of stacked lignite is.