Dear Experts!

Because commerical, sometimes I have other coals with the same parameters, such as calorific, ash, S total, even HGI (volatize is higher than 4%, from 7% to 11%), but we don't know why very hard for grinding and burning, and more "tenacious" for handling in Lab.

Maybe, do I miss an important parameter of fine coal? 

Thanks my Experts!

BRg,

Archi