One of the 'issues' with bitum coal is the wide variety of burning characteristics. I think the Wyoming Bitum coal will burn pretty well in and EFM stoker. It doesn't stick together and bridge, and it also won't grow 'coke trees' as easily.. The wyoming coal has similar burning characteristics to anthracite, but with lots of volitiles and soot.. The soot can be greatly reduced by adding extra fresh air over the top of the fire pot to burn off the volitiles..
By the way, the Tuyers are the perforated air grates surrounding the firepot. The Bituminous stokers did not have an ashpan. There was a wide [several inches at least] surrounding 'shelf' around the firepot, [usually made of refractory cement]. This is where the ash continued to burn and fuse together into clinkers,, then through an access door, clinker rakes and tongs were used to remove the clinkers. There was little loose ash.
This is very unlike anthracite where the loose ash just falls off the edge into the ashpan below.
What I think you will find with the first few tries at burning Bituminous, especially WestVirgina Bitum, and Western Penn. Bitum, is that the coal will create a lot of smoke and soot at first,, untill the water gets hot, which raises the temperature in the combustion chamber.
The coal will probably stick together, and make clumps of coke or partially burnt coal that will get tall and fall over.. As berlin suggested, a wider lip to let the chunks rest on to burn more completely would be helpful. I'm not sure that the rotating pot will be an asset or not, You may end up leaving the chain off the rotating drive.
Stoker man, what you really need to make an EFM for the Wyoming market is to get the Wyoming dealers to ship you a ton or so of Wyoming Bitumious coal,, Read the threads by 'steinkebunch' on the Bitum forum, his description of the wyoming coal may be helpfull I think you may be able to make a very good EFM boiler for Wyoming Bitum, but the various eastern Bitum coals... Illinois, both northern and southern,, West Virginia, and Western penn... all have different characteristics.. so this may take more time to develope.
I'd suggest getting a 1" tube set up with high pressure air, put something like a 'shower head' on the 1" pipe, and have this over the firepot.. when the fire is hot, but smoking a lot,, add extra air over the fire,, it should look like a blowtorch in the combustion chamber..
In many of the Bituminous-Stoker newspapers I have from the late 30's and early 40's, there were heat reflectors sold that were basicly a disc suspended over the firepot, maybe 8-12" above the fire. These reflectors were either steel or ceramic, and reflected the heat back down on the firepot,, increasing burn temps and helping create the fused clinkers to facilitate keeping the firechamber clean.. EFM may want to experiment with a plate of steel or ceramic suspended horizontally over the fire to keep the firepot temps higher..