nwaelder wrote:2) I have heard that "Banked" coal also will not burn. (I haven't personally seen it though, so I can't confirm). Years ago I'm told, the smaller fines (rice and pea) were not of use, so they were "Banked", piled up and left on the side. So the story goes, the banked coal is now being mixed in with freshly mined coal. After being banked for 75 years or so, all the volitiles in it have evaporated.
The rrice,buck&barley... was used for fill, commonly on railways so it was covered the entire time. Right up until someone realized you could burn it with a forced draft. Now it's the exact opposite and it's the rice which is in demand. As for how well it burns I really don't know, AFAIK all the coal I'm getting is freshly mined. They do test on site daily and have it tested off site periodically. It has to meet the specs or they can't sell it...
For what it's worth, I'm not sure I buy the banked coal explanation for unburned coal. I think that the grate design of all stokers I've seen are capable of burning pure carbon.
My guess is that it's the stoker factor, essentially you're forcing it to burn and it isn't given sufficient amount of time. As I've mentioned before the same coal burned in a hand-fired unit will burn up to nothing but dust...and I do mean dust... yet will have a chunky ash from the stoker. Same load of coal from the very same bin. Wish I had taken pictures when we had the hand fired unit running because you would not believe the difference, it was like night and day. The ash can even differ for us according to the season, the summer ash is without a doubt more fully burned than the winter... again it has more time to burn because there is little demand.