I don't know the specifics of the coal used by the NKP. However, I would bet that the coal they used "back in the day" had higher ash content than our specification of only 6%. Coal with only 6% ash is much more expensive than coal with 8% or 10% ash. Back then, a coal-fired steam locomotive ran about 100 miles, then came off the train for servicing. In that servicing process, the ashes were dumped and the fire cleaned. High-ash coal would work OK for only 100 miles.
Today, we often have to run the 765 more than 300 miles between dropping the ashes and cleaning the fire. So we have to keep the ash build-up to a minimum in order to have a fire that will work all day for 300+ miles. We have used coal that was 8% to 10% ash and it was always a problem. Even firing the engine lightly and cleanly would result in a full ash pan after about 150 miles. When the ash pan is full, it significantly cuts down on the draft available for the fire because the movement of air coming in and under the gates is severely restricted. We also tried coal that was only 4% ash, and it was wonderful! But it was also very expensive and not worth the extra expense when 6% coal worked fine for our purposes.
The N&W Pocahontas coal has similar ash content, but higher heat values. I've seen that coal go as high as 14,400 btu/lb. We used it every once in a while, depending on where we were operating. Good stuff!
The coal we purchased for the 765 came from mines in Ohio, Indiana, Kentucky, West Virginia and Pennsylvania, depending on what was available at our specs and sizing, and where I could get the best price. None of the mines were served by the WLE. In fact, some of them did not even have rail service.
