% Unburned

rschoensta
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Post Wed. Feb. 14, 2007 6:22 am

I have been weighing both coal in and ashes out for the last 2+ weeks.

I figure I have enough data to get some idea of how well my stove is burning
the coal.

We've had cold weather here for 3 weeks.
The stove has been running at 100% during this time period.
I am guessing this is when it burns most efficiently.

I figure that for every 100lbs of coal I burn, I have 18lbs of ashes left over.
Which I think is not bad for a stoker.

Anybody else weigh their ashes?
And what are the results?


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Yanche
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Post Wed. Feb. 14, 2007 7:47 am

rschoensta wrote: I figure that for every 100lbs of coal I burn, I have 18lbs of ashes left over.
Which I think is not bad for a stoker.

Anybody else weigh their ashes?
And what are the results?
I made my ash measurements last season on my AHS S-130 stoker boiler. 100 lbs of pea coal makes 18.8 lbs of ash.

Yanche

dll
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Post Wed. Mar. 21, 2007 11:17 am

I have been making ash measurements for a week now on my hand fired Harman MKII. Out of 162.49 pounds of nut size Anthracite burned I ended up with 18.63 pounds of ash. This calculates out to 11.46% ash.

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Richard S.
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Post Wed. Mar. 21, 2007 11:29 am

rschoensta wrote: The stove has been running at 100% during this time period.
I am guessing this is when it burns most efficiently.
My experience has been this is not the case at least for my stoker boiler, the ashes are generally burned up quite a bit more when they have time to burn longer. The smaller clinker type ash is almost the consistency of hand-fired ash(see below). You may even want to try doing your weighing for a warm spell where the stoker is running at a minimum. I'd also add that it stands to reason that if it's running full tilt you are also have more heat going out the chimney.
This calculates out to 11.46% ash.
As I've mentioned before a hand-fired unit always burns the coal up better than a stoker. I'm assuming it's because instead of being forced to burn it's just burning. I've used the very same coal from the very same load both in a stoker and hand fired unit. The stoker ash was its normal chunky consistency, the hand-fired ash on the other hand wasn't much more than powder.

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coalkirk
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Post Wed. Mar. 21, 2007 4:19 pm

As I've mentioned before a hand-fired unit always burns the coal up better than a stoker. I'm assuming it's because instead of being forced to burn it's just burning. I've used the very same coal from the very same load both in a stoker and hand fired unit. The stoker ash was its normal chunky consistency, the hand-fired ash on the other hand wasn't much more than powder.[/quote]

I find the same thing with my stoker as compared to my hand fired stove. I consider it the cost of the convenience of the stoker.

Bob
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Post Wed. Mar. 21, 2007 5:32 pm

Richard S. wrote: As I've mentioned before a hand-fired unit always burns the coal up better than a stoker. I'm assuming it's because instead of being forced to burn it's just burning. I've used the very same coal from the very same load both in a stoker and hand fired unit. The stoker ash was its normal chunky consistency, the hand-fired ash on the other hand wasn't much more than powder.
I wonder if the difference in the ash is because hand fired units generally have shaker grates that tend to break up the ash while stokers simply push the ash off. It would seem to me that you would have to have careful measurements of weight of coal in and weight of ash out for the same batch of coal for both the stoker and the hand fired unit to conclude that there is a difference in the completeness of combustion between the stoker and the hand fired unit.

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Richard S.
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Post Wed. Mar. 21, 2007 6:47 pm

Bob I'm sure that has a little to do with it but the chunkiness that I'm referring too could not be broken up that much by grate action alone.

stockingfull
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Post Wed. Mar. 21, 2007 7:21 pm

My stoker's been running in the same ballpark: about 50# out for about 250# in. And I too get a variety of clinker, powder, and chunky, seemingly unburnt coal in my ash mix.

I must say, however, that I haven't really noticed a difference in the mix under varying burn conditions. But I'll try to pay a little more attention to that going forward.


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Richard S.
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Post Wed. Mar. 21, 2007 8:34 pm

Just to add my experience from when it burns up more is in the summer months. Due to the design, remember this stoker has the upside down bell, the coal pushes up from the bottom. The same pieces of coal may be sitting in the fire for the most part of day. This I would assume wouldn't might not give you the same results with the stoves.
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Matthaus
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Post Wed. Mar. 21, 2007 9:59 pm

In addition to the type stove/grate arrangement and size of coal, in my experience the ash content is a major contributor.

I have been running an old style Alaska Triburner and a Harman Magnum all winter with rice size coal. Depending on the source of my coal I get anywhere from 7.5lbs per 100 to 23 lbs per 100 (in other words 7.5% to 23% ash regardless of which stove is burning it). The consistency is a fine powder for the low ash coal and more chunky with klinker looking formations for the higher ash.

I did find that the buckwheat size coal seemed to burn better than the rice if it was from the same breaker. Something about more room for air around the coal with my particular stoker units.

Just my observations for what they're worth (and you know what they say about opinions!). :roll:

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coaledsweat
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Post Thu. Mar. 22, 2007 9:09 am

According to Axeman-Anderson, a ton of anthracite starts with 240# of useless ash (12%). The anthratube will waste 60# of that ton in unburned coal (3%). It also points out that 200# (10%) goes up the chimney as wasted heat. That leaves 1500# actually heating the house (75%). I would think that other stokers would be a little less efficient. That adds up to about 15% or 15 # per hundred in to ash out w/unburned coal as the "best case" scenario.

I will add that the "Yanche Report" (Bureau of mines) shows it to be slightly more efficient than advertised.

So unburned % in the very best case will run 3% or higher, the average stoker may run @ 4-6% (4-6#) unburned coal in the ash.

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Yanche
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Post Thu. Mar. 22, 2007 11:11 am

I'm in the process of scanning the referenced A-A Bureau of Mines Report. There is a very large fold out data summary page that wouldn't scan well enough to be very useful. I'm now converting it to an Excel spreadsheet. I think the report is a significant historical document because it is so comprehensive. A very well instrumented coal boiler installed in a home. The data was collected in 1949 and 1950. Give me a couple of weeks to finish it and I'll post it here or publish a link to my own web site.

Yanche

stockingfull
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Post Thu. Mar. 22, 2007 12:36 pm

So I salute the forum administration for facilitating this. =D>

Even if my brother thinks I'm now responsible for global warming! :roll

Edit: Sorry stockingfull wrong button :oops: I hit the edit button instead of quote and deleted some of what you posted.

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Richard S.
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Post Thu. Mar. 22, 2007 1:37 pm

Sorry about the above.

You're welcome, of course without the members it's just a blank page so thank you.

As for your brother invite him over for dinner on day that it's 5 degrees out and answer the door in shorts and a hawaiian shirt, then show him your heating bill at the end of the year. :lol: You have to heat your house somehow, you might as well do it cheaply.

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Yanche
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Post Thu. Mar. 22, 2007 1:50 pm

stockingfull wrote:Even if my brother thinks I'm now responsible for global warming! :roll
It's not clear to me how much residential coal heating contributes to global warming compared to the other alternatives. For example over half of the US electricity is produced by burning bituminous coal. It's not a very efficient OVERALL process to turn back into heat. I'm trying to understand all the losses in making that electricity and getting it to the user. Looks like 1/3 of the energy in the coal is lost, lost heat at the power plant, transmission losses in the electric power grid, etc. Residential coal heat is a low temperature process. We are not making high pressure steam to drive a turbine. A much greater fraction on the energy in the coal gets used. It may turn out that from a global warming point of view, local residential Anthracite coal burning in an efficient boiler is desirable. I welcome analysis by others. This is an scientific analysis task the Anthracite producers and appliance manufacturers should jump on. Like I say, "Coal, back to the Future"

Yanche


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