Hello sarge.. you will have to install an adjustable air control that lets some air in all the time to keep the coal burning.. You will keep losing the fire or getting partial fires without some continous air.. Then use an aquastat to control a forced air combustion fan to ramp up the fire.
I built my own wood/coal boiler.. and made plenty of mistakes.. firebox design is one big mistake.. if you want to burn anthracite or Bituminous coal well, you MUST have a deep firebox, with vertical sides, and the entire bottom of the firebox covered with shaker grates..
My firebox is 24" wide, tapering down to 9" at the grate, about 10"deep and it WAS 50" long, for the ability to load plenty of wood, and long logs.. After I found out that feeding this monster was a full time job, and I was looking for a 12 hour loading schedule, I went to coal.. Well a long, narrow, shallow firebox with tapered sides is a lousy coal firebox.. I should have looked at just coal-burning boilers and furnaces, and copied that firebox design.
What I leared is to have a frustration free anthracite burning firebox, whould have made the firebox roughly square,, 22"x22"x 18" deep, with vertical sides, and aggressive shaker grates on the bottom.. with this design I would quite possibly still be using my boiler as a hand feed.
I had to build a firebox reducing back wall and stack firebrick at the door to shorten the firebox and allow for a deep fire. this helped a lot,, but the 'V' shaped walls and narrow grate at the bottom caused the hot coals to be forced together as they burned, this creates clinkers.. the very hot ash from coal will fuse together when agitated when hot, and the 'V' shape acts like a funnel,, so I always had problems with clinkers.. These clogged the grates after about a week, and I had to let the fire go out, clean off the grates, and start over for the next week's burning... not fun.
Go to the various sites of the made-to-burn coal manufacturers.. FORGET everything about wood,, it doesnt apply. look at the good firebox designs..
do a google search for
Harman stoves hand feed boilers and furnaces
Hitzer stoves and furnaces
Copy the flat bottomed, vertical sided, deep firebox as close as you can.. every effort you put toward this goal will be effort well spent.