Coal Size Options in 520

Good morning, hope everybody has things working in this cold weather and that the coming snow is not huge!
Ii have been running my 520 for 5-6 years now, burning rice from Sherman coal each year. I get alot of clunks of coal that are all clumped up like little rock aggregates. Also seems to be alot of duat and fines, maybe that is why the clumps. Sometimes I get an outfire because somerhing has clogged up in the tube, I have a double length auger.
What if any advantages/disadvantages would there be in going to a larger size coal? How big can I go with that long of an auger tube?

Rice is the recommended size & also the most commonly used size,followed by buck.I do know of one member who is running pea thru his EFM stoker,that is unusual tho.Rice flows thru the auger easiest,with the least grinding & crunching,which should be better for the auger & tube as well as all the mechanical parts of the stoker.Some use buck for less fines & the perception that buck takes less air.It only seems to take less air because the air blows thru the bigger coal more easily & requires the air adjustment to be set back compared to rice. The clumping issue you experience is likely the brand of coal you are using,i have never seen any clumping with any of the coal I have used from Superior,Blashack,Reading & now Gale. I have never experienced any outfires either. Are you using a timer to run the stoker ?

I agree with David that the issue is with your supplier, not with the size. Rice is trouble free in these machines if it meets standard anthracite specs.

Buck works pretty well also if it is standard spec. and your auger is setup correctly. I put 10 tons through mine with a full length bin auger. If you want to try buck, make sure there is no more than 2.5 flights of auger exposed into the coal.

Thanks for your answers guys. I do have a timer on it. Sherman is the only coal I have used, it seems to be very dusty, a lot of real small fines. I am in Winchester, VA, so I try to find the more southern breakers. We have hand Candy's coal deliver a load and have had a couple tractor trailer loads delivered. My neighbor and I split a load. I do about 7-8 tons/ year.
Should it be real dusty? I mean my entire bin and furnace room is black, I can not imagine this being in my house/basement
Brent

Get a load fresh from the sizing plant at the breaker. No fines, no junk, and it will be damp.

Get a sheet of grating with dime size holes in it and put it on top of your barrel. When you pour the coal in it will catch the clumps.

Buck can be burned but the larger size puts more stress on the parts.

My coal hauler who has been hauling coal for 30 plus years says rice in the 520 unit. He also said over the years rice coal has gotten larger. He has a 520 in his own home.
I remember my grandparents had an efm stoker unit with an automatic asher firing a huge Fitzgibbon's steam boiler. They always used BUCK.

The manual says use rice in a 520. Most of the EFM conversion stokers used with other boilers had larger diameter feed augers and tubes, and were better able to burn buck.

Mike

The manual also gives useful guidance regarding the quality of the coal:

"1. The coal should contain not more than 10% oversize and not more than 15% undersize. Oversize or undersize coal, in excess of these
amounts, will result in poor combustion.
2. Excessively wet coal should not be used, as it will retard combustion. Dust treatment of coal is accomplished either through the application of certain chemicals, or oil. Excess quantities of oil on the coal will result in unsatisfactory operation...
3. When securing a supplier for your coal, be sure he is aware of the above conditions and make sure you get clean coal with no foreign
materials and a minimal amount of fines..."

If the same coal has to be used, mm100 might consider screening to eliminate both the clumps/chunks (perhaps with 1/2" mesh hardware cloth) and the fines (1/8" mesh).

Mike

I prefer buck.The manual was changed when they up graded the transmission size to the new foreign one or so I've been told. I would think that since it is only pushing 2 lbs per tooth with buck instead of the 2.5 lbs per tooth with rice that it would be easier on the parts. Of course it makes more noise.