EFM Coal Uneven in Pot

 
RICHARD2
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Post by RICHARD2 » Tue. Jan. 17, 2023 6:21 pm

In use for 7 years. Fire pot is level.
Blower turning correct direction.
All grate holes are open -- checked with 1/8" drill bit before lighting for the season. Grates correctly positioned and gasketed.
Fines emptied daily.
Auger feeds directly from 5 ton silo.
Draft .02" over fire. Air at 3-1/2.

The problem is the coal is uneven by 1 to 1-1/2 inches in height. Looking through the door, the higher side runs from 10 o'clock to 4 o'clock [where the auger feed is at 9, and the blower air tube is about 2 o'clock].
Counter intuitively the higher/thicker section burns incandescent yellow hot, with tall flames; while the lower/thinner side is dark grey with dull red below and short 2" blue flames. Note the blower air feeds in at the side that is burning poorly.
Last week I emptied the fire pot expecting to find that some foreign material in the coal--plastic?- had melted and blocked the grate holes on that side. Not the case, and for good measure I probed all the holes with an awl -- all clear.
Re-lit the boiler, the fire pot filled normally -level across- and burned well. By the second day the same uneven height had re-appeared.
The coal supply crush this year resulted in my supplier obtaining coal from a different mine. It clearly was not screened for size. Purporting to be 'buck', it actually ranges in size from 'pea' to smaller than 'rice' to 'grain-of-sand' size bits, that burn as incandescent sparklies in the flame.

Until this year, the coal always rose in the pot evenly, forming a volcano-like 'dome'.
Anyone experience a similar uneven feeding issue?
Theoretically, How would coal pushed up from the center bottom not spread evenly in the concentric circular pot?

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Last edited by RICHARD2 on Tue. Jan. 17, 2023 7:08 pm, edited 1 time in total.


 
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Idlorah
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Post by Idlorah » Tue. Jan. 17, 2023 6:55 pm

Did you find any fines in the pot? How are the conditions of the augers and auger tubes? Does it sound like coal is grinding going
down the feed tube? I believe this could be a fines issue.

 
RICHARD2
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Post by RICHARD2 » Tue. Jan. 17, 2023 7:09 pm

Yes, there are a lot of fines. It appears the coal was not screened at all.

 
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Idlorah
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Post by Idlorah » Tue. Jan. 17, 2023 7:25 pm

I would bet that is your culprit. Is it grinding in the auger tube? are the auger tubes butted together in the coupler?

 
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Post by Dave 1234 » Tue. Jan. 17, 2023 7:28 pm

Sounds like time for a new pot bushing and auger .

 
Scott in nwct
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Post by Scott in nwct » Tue. Jan. 17, 2023 7:57 pm

Pull the fines lever, and check under in the openings. Mine was clogged with wet fines. Even though the top holes in the pot appeared clear. Also a large chunk of coal was partially blocking the end of the worm in the feed barrel. I had this last year, now I screen the coal and make sure it is dry. Good luck, Scott.

 
RICHARD2
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Post by RICHARD2 » Tue. Jan. 17, 2023 10:55 pm

Idlorah wrote:
Tue. Jan. 17, 2023 7:25 pm
I would bet that is your culprit. Is it grinding in the auger tube? are the auger tubes butted together in the coupler?
The auger tubes are butted tightly; auger and bushing are good. The fines are visible in the coal as delivered, and those fines are being fed directly from the coal silo through the auger, into the burn pot.
Scott in nwct wrote:
Tue. Jan. 17, 2023 7:57 pm
Pull the fines lever, and check under in the openings.
I do use the lever daily, and last week when I emptied the fire pot to check the grate holes for blockage, I also tied the fines dump lever open and used a hooked wire to probe and remove the fines that accumulate as sloped heaps on the frame between the openings, and also from the top of where the auger pipe connects to the fire pot.

I understand and agree that fines can obstruct the flow of air through the coal in the pot and hence the burning of the coal. But that doesn't explain, Why only half of the pot is affected; or, Why the coal is not rising up evenly in the pot.
I added a sketch to the original post to portray the problem as viewed from inside the fire box looking toward the door. Not apparent from my sketch is the fact that the demarcation line between the halves runs at a diagonal relative to the auger and air tube.


 
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nepacoal
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Post by nepacoal » Wed. Jan. 18, 2023 5:51 am

If this is a 520, 3-1/2 seems very low for the air setting. When I've gotten a load with excessive fines in my flatbed stoker, I've had to crank up the air quite a bit to even out the fire. Luckily I have a 30' interior chimney with plenty of draft so I can get back -.02 draft over the fire.

What was your ash ring looking like with the air at 3-1/2? Our 520 would not have much of an ash ring at that setting. Ours typically requires 4-1/4 air to get a 1-1/2 inch ash ring when running 4 teeth.

If your chimney has the draft to support it, I'd suggest you crank up the air to 4-1/2 to 4-3/4 and readjust the barometric damper to get your draft over fire back to -.02. Hopefully your burn pattern will even out and give you a 2" ash ring.

 
RICHARD2
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Post by RICHARD2 » Thu. Jan. 19, 2023 12:44 am

nepacoal wrote:
Wed. Jan. 18, 2023 5:51 am
What was your ash ring looking like with the air at 3-1/2? Our 520 would not have much of an ash ring at that setting. Ours typically requires 4-1/4 air to get a 1-1/2 inch ash ring when running 4 teeth.Hopefully your burn pattern will even out and give you a 2" ash ring.
The ash ring was good prior to this issue--- 2" wide with a very few pieces of partially burnt coal.
But I run at 3 teeth vs your 4 teeth.

 
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Post by nepacoal » Thu. Jan. 19, 2023 6:51 am

I'm still thinking you need more air to adjust for that extremely dirty load of coal... It may be that that coal is just too full of fines to burn correctly no matter what you try, but giving it more air and readjusting your draft may really help.

 
ben
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Post by ben » Thu. Jan. 19, 2023 7:05 am

I had a similar problem a few years ago. My bin auger pipe was rusted out which allowed more of the auger exposed.
I replaced the bin pipe and have 2.5 flights of the auger exposed. It was an easy fix.

 
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Post by Rob R. » Thu. Jan. 19, 2023 7:30 am

I have had a similar issue in the past when I got down to the bottom of the barrel and got into some fines. In my case it was only for a few days, so I just turned the air up a bit and worked through it.

 
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Post by RICHARD2 » Fri. Jan. 20, 2023 12:35 am

nepacoal wrote:
Thu. Jan. 19, 2023 6:51 am
It may be that that coal is just too full of fines to burn correctly no matter what you try, but giving it more air and readjusting your draft may really help.
The left half has a normal looking, bright incandescence with high flames, at the same time that the right side is dull, with very short blue flames. I agree the right side appears to need more air, but the left side doesn't ---- that's why my first thought was to check whether the grate holes were blocked on the right side. They are not.
What could explain how both conditions can exist while receiving the same air supply?
Rob R. wrote:
Thu. Jan. 19, 2023 7:30 am
I have had a similar issue in the past when I got down to the bottom of the barrel and got into some fines. In my case it was only for a few days, so I just turned the air up a bit and worked through it.
I wish it were only for a few days, but I'm not feeding from a barrel so I'm afraid it will be for the next few months.

 
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Post by Rob R. » Fri. Jan. 20, 2023 6:14 am

What could explain how both conditions can exist while receiving the same air supply?
I think the coal packs into the pot a bit tighter on the side opposite the auger. With clean coal the air is able to come up through the coal as intended, but when you start getting fines the air takes the path of least resistance.

If you are using a steel auger tube I would check the inside of it for pitting. It doesn't take much to cause grinding. In the meantime, turn the air up a bit.

 
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Post by KT2 » Fri. Jan. 20, 2023 9:01 am

I've been having the same issue. I only ever got rice from Direnzo's for 6 years. Had to go to Superior and only could get Buckwheat. It's pretty clean looks good. Problems right away, backside of pot is dead. Only 20 tons since i replaced the auger/pot bushings and made new stainless auger tubes. This boiler only broke a shear pin once in 30 years. I removed auger and checked everything and found nothing wrong. When i cleaned pot out the backside was packed full of fines. The coal sizing I discovered is a good bit bigger than it should be. The nut coal my Dad got last year looked like it had some stove coal in it. This year it looks like everything from rice on up in his nut from Superior. I'm going to just let it burn and rotate my ash pan 180 degrees every couple days because it fills uneven. I turn my air up to 9 when i pull the cleanout lever and then close it and let it run like that for a little. It blows alot of fines out of the fire.


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