[Eric in the Ozarks]

When my family was in the coal mining business we built a 250 ton/hour wash plant to reduce the ash and pyrites in the coal. Heat for inside the plant was furnished by an underfeed stoker furnace that held coal in a hopper and used an auger to move the coal from the bin into the bottom of the unit. It was pushed upward by the force of the coal behind it and splayed out burning on upside down grates called teweers. A modern thermostat kicked on the auger and the bin held about two days' worth of fuel.
The stack reached above the wash plant building which stood about four stories high. The entire system worked very well and only occasionally did anyone get a whiff of burning coal.

[Viking2002]

Pretty sweet. Up here, if you drive up I-68 west in the Frostburg area in the winter months, you can see steam venting from the bedrock along the highway. A seam in an old coal mine caught fire about a century ago, and they tried everything to put it out - including flooding the shaft - but it wouldn't go out. So they just sealed the mine, and it still smoulders to this day.