different bituminous coals will burn differently, it's not necessarily "bad" or "good". It's only "bad" or "good" coal if you like or don't like how it burns for you. It sounds like you may have gotten a load of higher volitile bituminous coal which, aside from obviously flaring more volitiles, often burns hotter in it's coking stage as well because it produces less dense coke, higher volitile bituminous is often (but not always) low coke index coal which means it tends to allow more air spaces between burning coal pieces and thus more air makes it's way through the bed. If the smoke from the chimney doesn't bother you (no close neighbors etc.) than you don't have to change what you're doing, however, if you'd like less smoke try "banking" the fire, filling one end of the stove deep and then after that settles down on the next firing, fill the valley, and so on, thus alternating where you fire the coal rather than "spread-firing" the coal over the entire bed.