I don't think anthracite will burn in the system you describe. If you put coal on your grate, the air coming in from the bottom will just go around the coal and it will not burn. Anthracite stoves require shaker grates, flush with the bottom, that will allow the coal to cover the entire bottom of the firebox. Then the only way for the air to go is through the coal. Anthracite is much harder than bituminous coal, it will not burn if the air is not "rushing through" it. You might get bituminous coal to burn in your stove, but I wouldn't, too stinky & dirty. If you want to burn anthracite, you are going to need to purchase a new boiler, specifically designed to burn it. Harman Stoves make a very nice one.