For the last 2-3 years entire bags of dry rice (yes,coal) has been dumped into the Poke's hopper. Worked well. Lazy way...Easy....
This past day the light from the window seemed not as bright with one side of the coal not burning. Further investigation showed that a couple 1.5-2" dia clumps of powder had adhered together somehow (likely when wet within the bag or more likely within the factory loading process) and were now clogging the feed shoot chute preferential to the side not burning. After pulling them out the entire system was happy again till later in the day when the same thing happen. Looked like a bad bag.
No significant lesson here except if this happens check the coal feed area first before looking any further into the mechanicals.