I have a hand fired furnace like yours. Let me tell you if you want heat, you need to fill the furnace with coal. I burned hard coal, and loaded close to 90 pounds. Its a bear to deal with at first, but its constant btus. I havent tried to burn coal yet in 30 to 50 degree weather. I was told to use my forced draft, which when the house calls for heat the coal will burn hotter, then die down when the house is warm. I remember the 1 night I woke up, it was almost 0 out, and I was rolling in sweat. The house was around 80 degrees, and hotter upstairs. It takes some time to get a good coal fire going, at least an hour. Put a thin layer over hot wood coals and open your bottom door a little to ignite the coal, then all another thin layer. Once you get a good coal be, pile it on and close the door. DO NOT OPEN The door to check it, give it about 30 minutes to burn some of the gas off, otherwise you will get a mini explosion, I have done it. Once its burning good, then turn it down where you want it. Close your feed door damper, and just open the draft under the fire. Once its burning, it will be fairly hard to put it out. From there you control the heat. I had probably a 15 to 16 hour burn, then I would add close to 35 pounds on top after shaking it down. I have a barometric damper and a key damper and I burn both wood and coal. The secret is check your chimney and flue pipe. I clean my flue once a month with my chimeny whether I need it or not.
I burned nut coal.