Have had a major fail with the underfeed stoker.....i put chip coal in and get 100% coal dust at the tuyre....lol i've built the worlds lowest efficiancy coal grinder.....
i had a talk to a guy that fires a couple of large steam boilers (500hp each) and told him what had happened.....found out they had the same problem a few years back when the mine opened their current pit and closed the old one....they had to completely redesign and rebuilt the feed setup to their boilers because the coal was being ground to dust before it got to the spreader....and when the spreader would throw it into the boiler it was flareing off above the firebed and getting blown into the tubes while still burning.....they had to change all their screw feeds to little belt conveyors all the way from the bunker to were it drops into the spreader/slinger.
so all my work in the underfeed stoker is a dead loss
on the up side the same guy thought that a flatbed stoker would work as long as it had secondary air supplied to the flame.....the sub-bit coal i need to use doesn't swell, melt together or do anything silly.....and it has quite a high clinker temperature so he thought that wouldn't be a problem either.
I got a Mellor 1RPM constant duty pellet stove motor and a dayton 49 CFM blower from the "electric motor warehouse" in the US that turned up today so round 2 will be a flatbed stoker with secondary air added....i will see how things go this time