Coal not burning properly

Hello all, and thank you for info i have obtained from this site. I am new to burning coal, purchased a US stove company wondercoal model 2827. I just feel that the coal is not burning completely. I get some ash, but for the most part whats left looks like big white cinders. I have the barometric dampner set. As well as the manuel dampner in the flue. Brand new clay lined chimney 8inch. Any help on my situation would be appreciated. Thank you all, and enjoy your Holiday

Post a picture, cinders is what you get. Can you easily crumble them up? For example if you got a hammer and lightly hit them would the turn to powder?

If there is no black left the fuel is used up.

Yes, for the most part they crumble easy. I am trying some different coal, to see how it burns. Feel like i may have some lower quality coal. By the way i am burning nut size coal.

Well then it's used up,.... You're going to have some "chunkiness" to the ash unless you have a really premium product and even then it will still have some chunks. A image would provide us with something to judge but it sounds to me like you're getting all you're going to get out of it.