I would first check to see if all the air intakes in the device are able to bring air into the firebox. I think the appliance has primary and secondary air intake. Also with the exhaust as well. To prevent further unburned coal. As well as the feeding of the coal. Job #1 - stop making more.
How well coal that has been exposed to a firebox will burn is a question. Others may chime in.
I would guess recovering unburned coal would be a labor heavy task.
https://www.manualslib.com/manual/1549917/Trianco ... e=5#manual
The device can burn either bean or grains sized coal..."The TRG boiler is designed to burn anthracite grains
and beans."
Perhaps try running the grains size and see if that helps ?
Not knowing what Carlos has done to mitigate the unburnt coal and their effects is limiting our understanding.
As for going through and re-capturing the unburnt coal contained within the ash . Perhaps find a solvent or liquid with the density that is higher than that of coal but lower of that of ash will allow Carlos to strain out the coal from the surface when a batch of ash/unburned coal is dumped into the liquid ?
https://www.uky.edu/KGS/coal/coal-analyses-float-sink.php shows a float/sink test..noting coal density at about 1.2
This leaves the choice of solvents to ones that are likely not suitable. See charts ... the chlorinated products have low viscosity and maybe useful but most will likely kill you too, most are hazardous. The non-hazardous glycols have too high viscosity to be useful. All would likely leave solvents on the coal and would be put into the firebox for burning...this might leave to hazardous oils being created by the system.
So a water system would be best...I would suggest making a NaCl solution or sugar solution and experiment with that to find one that would cause the separation needed. Suggest starting at 20% solids added to water and add 10% of solids if not working. I'd do the test here but I have no ash on hand. And to note, NaCl will only go into water up to 35% content, sugar is infinite..so don't bother with >35% for the salt, it will just precipitate the undissolved salt.
Wow 
