Unburnt coal

Unburnt coal

PostBy: wenchris On: Sun Jan 29, 2006 12:30 pm

Seems I'm getting more unburnt coal than I think I should. As you can see lots of black in with the ashes. Harman Magnum Stoker, pushing
1 1/2 dots. Heating the house good' just I think it could be burning better. Combustion fan restrictor open about 1/2 way. Any more open I get fumes into the house. Any ideas, are any other mag stokers getting the same?
Thanx Jimmy
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Too much unburnt for me
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wenchris
 
Stove/Furnace Make: Harman
Stove/Furnace Model: Magnum stoker with water coil

PostBy: kirk On: Sun Jan 29, 2006 1:25 pm

I've been using a Harmon VF3000 boiler for 3 years which uses the same feeder and burner mechanism. I have also noticed what appears to be unburnt coal. Inquiries I have made indicate that this is normal. As long as you have about 1" of ash before it is dumped off the end of the grate, it is burning as intended. This year, I adjusted my feed rate down to see if that made any difference and it did not. Overall, I could not be happier with the VF3000's perfromance. It heats my entire home and provides endless domestic hot water.
kirk
 

PostBy: lime4x4 On: Sun Jan 29, 2006 2:19 pm

It's hard to tell from your pic.. But having some unburnt coal isn't uncommon.
I've burnt just over 2 tons of rice coal. If i went out to my ash pile i might be able to fill a 5 gallon bucket with coal that didn't completly burn.you also have to remember that as the coal closes to the grates burns up it's gonna reduce the air flow for the very top peices of coal. It's odd thou that u get coal odor in the house if your restrictor plate is open more then 1/2
I've had mine fully open already never a issue with odor. The only thing i can think of is your draft maybe ain't real strong at times? U ever get the draft gauge from the dealer?? I borrowed one from a heating contractor and using the baromteric dampner i set it to maintain .05 draft.. I've found that gives me good heat from the stove and a flue temp of 200 to 250 degrees when the stove is putting out 650 degrees of heat..to me that's pretty good effeceincy.
lime4x4
 


PostBy: AL-53 On: Sun Jan 29, 2006 6:29 pm

Jimmy...yes..you will get unburned coal....I think it should be less than it is...I think the time on the grate is to short...need a longer time on grate...

thats another story...lol...

AL
AL-53
 

PostBy: Richard S. On: Sun Jan 29, 2006 8:17 pm

Stokers will never fully burn the coal, especially if you're running it fast. As I mentioned in another thread we had a old franco-belge hand fired stove in one part of our basement. It would burn the same coal that was going into the stoker to almost a talculm powder like consistency. The satoker on the other hand would not. It was all coming from the same load so that wasn't a factor.

I even have a old Van-Wert manual laying around here that states that. It shouldn't be excessive though.
Richard S.
 
Stoker Coal Boiler: Van Wert VA1200
Coal Size/Type: Buckwheat/Anthracite

PostBy: mjb On: Mon Jan 30, 2006 4:11 pm

From seeing pictures of people's stoves I think our ashes are pretty much the same. I even took a coffee can of ash to my coal dealer and it looks just like his. I think Al is right about the burn time improving the ash content. Can live with what I have but you always like to improve where you can.
mjb
 

PostBy: Oil Region On: Mon Jan 30, 2006 11:41 pm

Has anyone ever tried 'reburning' their unburnt coal from the ash? I know it would be a real pain to collect, but it would be an interesting experiment to see if it is actually coal or perhaps some other type of substance. Whether it burned the second time would give some indication of how much you really lost in terms of BTU's.

Troy
Oil Region
 
Stove/Furnace Model: Harman DVC-500

PostBy: Richard S. On: Tue Jan 31, 2006 12:20 am

I'd imagine it would burn, if you examine it you can uasually break it up and find that the inside is coal. It just hasn't had enough time to burn. At one point last year I had a few customers calling comnplaining about excessive unburned coal thinking it was a bad product but in fact it was the exact opposite. It was an excellent product.

The coal they received was a much denser harder product than they were used to and wasn't given sufficent time to burn. Some were even increasing the feed rste exacerbating the problem. After I explained to them most turned down the feed rate and increased the air where possible and had no trouble after that.
Richard S.
 
Stoker Coal Boiler: Van Wert VA1200
Coal Size/Type: Buckwheat/Anthracite

PostBy: wenchris On: Tue Jan 31, 2006 9:25 pm

Yes I tried putting the ashed thru a 1/4" hardware cloth (screening) and put it back in the hopper. When this unburnt coat reached the grate the fire went out! Tried again but mixed with new coal it burnt just fine. Don't know if its worth the effort and mess though.
Jimmy
wenchris
 
Stove/Furnace Make: Harman
Stove/Furnace Model: Magnum stoker with water coil

PostBy: Richard S. On: Wed Feb 01, 2006 1:00 pm

wenchris wrote: Don't know if its worth the effort and mess though.
Jimmy


Probably not.....
Richard S.
 
Stoker Coal Boiler: Van Wert VA1200
Coal Size/Type: Buckwheat/Anthracite

PostBy: Cap On: Sat Feb 04, 2006 7:55 am

Using a handfired unit, I too see unburnt or partially burnt coal. I think part of it is due to an improper shakedown. ( too long or too often ) Now that I can monitor the temps inside of the firebox, possibly I can shake less, and have a more thorough burn.
Cap
 
Hand Fed Coal Boiler: Harman SF 250, domestic hot water loop, heat accumulator

PostBy: bbarber275 On: Fri Feb 24, 2006 8:36 am

You can pick through all that what looks like unburnt coal you want but it will never light.It is not really the coal that burns but the gases inside of coal.Watch coal and it pops and breaks open.That coal is spent
bbarber275
 

it's not necessarily unburnt coal.

PostBy: nwaelder On: Fri Feb 24, 2006 11:24 am

Assuming one has a complete burn operating setup (no visible fire for about two inches from end of grate), what appears to be unburned coal can be two things:
1) Unburnable slate material. This is dark in color and looks like coal, but it crushes like rock. It's really an indicator of the coal quality.
2) I have heard that "Banked" coal also will not burn. (I haven't personally seen it though, so I can't confirm). Years ago I'm told, the smaller fines (rice and pea) were not of use, so they were "Banked", piled up and left on the side. So the story goes, the banked coal is now being mixed in with freshly mined coal. After being banked for 75 years or so, all the volitiles in it have evaporated.

For what it's worth, I'm not sure I buy the banked coal explanation for unburned coal. I think that the grate design of all stokers I've seen are capable of burning pure carbon.

Maybe the Coalman can shed more light?
nwaelder
 

How to determine unburned coal.

PostBy: nwaelder On: Fri Feb 24, 2006 11:28 am

In my experience, unburned coal is never seen by looking at dark particles in the ash bin. The way to examine for unburned coal is to crush what looks like ash and if the outside is ash and the inside is black, then it is probably unburned coal.
nwaelder
 

PostBy: nwaelder On: Fri Feb 24, 2006 11:32 am

wenchris wrote:Yes I tried putting the ashed thru a 1/4" hardware cloth (screening) and put it back in the hopper. When this unburnt coat reached the grate the fire went out! Tried again but mixed with new coal it burnt just fine. Don't know if its worth the effort and mess though.
Jimmy


I like that you did a real experiment! This is the way to understand how things work. Much better than idle speculation.

I think that your result confirms the fact that dark particles in the ash are not coal at all, but are other non-burnable material.

[Edit: fixed spelling]
nwaelder