As far as burning Anthracite Rice Coal I will tell you what has been working very well for us.
I have blocked off half the draw point of the hopper with two pieces of 2 inch flat stock reducing the draw point to 2 inches wide and I still have a full width bed of coal entering the fire grates.
With my lower aquastat and hold fire timer settings the boiler will reach 180 degrees Fahrenheit and I have very little coal spilling over the sides of the stoker.
I am sure you can close the draw gate depth to half open or less and still have an adequate fire like I have.
I also have a finer heavy coal ash so I know I am getting a better burn as well.
A good way to help dry out the coal is to use 2 buckets and a brick, the lower bucket has the brick in it with the narrow edge facing up and the upper bucket has a large number of very small holes drilled in the bottom and that lets the water and fine coal dust in the water fall out and eventually dry out and you can either pour it in a corner of the hopper and let the stoker burn it or use it for driveway grit or put it in the garbage but it is a shame to waste it.
You could mix it with corn starch and water or just use molasses and pour it on a baking pan covered in parchment paper and flatten it with a second sheet of parchment paper into a thin layer using a brick or 2 and a second baking sheet and let it dry and break it up and throw it in the hopper.
Buckwheat to Rice settings? Keystone Keystoker KA6
