With Respect to Mositure How Are Anthracite Btus Calculated?

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lsayre
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Post Sun. May. 08, 2011 12:07 pm

I wonder if anyone ever experimented with bituminous (or perhaps a blend of anthracite with bituminous) in their AHS Coal Gun boiler? I know of some experimentation (apparently successful) with bit in the EFM boilers, but that appears to be a special case due to the design.

The only bit I've eve seen in person was in gigantic lumps.


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dlj
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Post Sun. May. 08, 2011 12:18 pm

lsayre wrote: Mike, that is what I was afraid of. Then if you assume roughly 82% for stove or boiler efficiency, the final figure is about 10,000 usable (recoverable) BTU's per pound of anthracite.
Not sure why that is bad??? My stove holds roughly 70 pounds of anthracite - that's 700,000 BTUs sitting in my stove that I can somewhat control the burn rate on. If I burn that in 7 hours, that's 100,000 BTUs per hour - pretty good I'd think... I usually burn much less, but I think I've burned 120 pounds in a 24 hour day when running quite hot. That's 50,000 BTUs per hour. That's a lot of heat...

dj

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lsayre
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Post Sun. May. 08, 2011 12:21 pm

Agreed! The most economical heat for anyone (like me) who has no access to natural gas.

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Berlin
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Post Sun. May. 08, 2011 2:17 pm

well, your most economical heat would have been a bituminous stoker boiler fueled with local bit stoker @100/ton, but anthracite works as well... :D

13,000+ BTU is a little high even dry basis for penn anthracite. most of the anthracite coal mined will average around 12,000 btu. you're not going to be above 12,000btu wet without single digit ash percentage in general. A good penn bituminous coal will average higher BTU's as recieved than anthracite; West virginia, southwest pa, and Kentucky coals will often be a few thousand more BTU's as received per lb than anthracite.

http://datamine.ei.psu.edu/sample_find.php?page=1

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lsayre
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Post Sun. May. 08, 2011 2:34 pm

Berlin wrote:well, your most economical heat would have been a bituminous stoker boiler fueled with local bit stoker @100/ton, but anthracite works as well... :D
Probably so, but I'm pretty close to the neighbors on either side (as well as across the street) and they just might complain loud enough to run me out of the coal burning business if I was to burn bituminous. On that subject, I'm not sure how well they are going to take to anthracite. None of them know about it yet.

$100 is mighty tempting though.

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Post Sun. May. 08, 2011 2:35 pm

they wouldn't know you were burning bituminous if you used a stoker. In a stoker, it burns almost as clean as anthracite. It is best not to let ANYONE living next to you know that you heat with coal, it tends to bring the nut's out of the closet, and you won't know who they are until they start whining. One of my neighbors asked what I had in the trailer, I told him topsoil for the garden :roll: and that was that (I live in the city of buffalo with neighbors less than 15 feet on either side).

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Post Sun. May. 08, 2011 2:53 pm

Berlin wrote:well, your most economical heat would have been a bituminous stoker boiler fueled with local bit stoker @100/ton, but anthracite works as well... :D

13,000+ BTU is a little high even dry basis for penn anthracite. most of the anthracite coal mined will average around 12,000 btu. you're not going to be above 12,000btu wet without single digit ash percentage in general. A good penn bituminous coal will average higher BTU's as recieved than anthracite; West virginia, southwest pa, and Kentucky coals will often be a few thousand more BTU's as received per lb than anthracite.

http://datamine.ei.psu.edu/sample_find.php?page=1
On the list I posted in this discussion (see previous page), it's listing BTU's for anthracite in the 14,000 range generally and the bit coals in the 15,000 range generally. You don't see drops in the 12,000 range until you get down into sub-bituminous... Something doesn't add up here ...

dj

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Berlin
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Post Sun. May. 08, 2011 3:28 pm

There are three ways to evaluate a coal's btu's, "moisture ash free", "moisture free" and "as received". if you're looking at anthracite in the 14,000btu range, it's moisture ash free. as received anthracite will average 12,000btu/lb

This is why the as received for subbit will generally be around 7-10000btu's/lb, there's more moisture in sub bit.


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AA130FIREMAN
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Post Sun. May. 08, 2011 3:33 pm

Could bit coal have a problem with burning up into the coal hopper on an ahs130 ??? Being an efm is underfed, not a concern.

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Post Sun. May. 08, 2011 3:36 pm

It would depend of the qualities of whatever bit coal you were planning on using, but in general, the lower ignition temp and propensity to produce gas even below this temp would render bituminous coal an unsuitable fuel for the hopper-fed boiler such as the ahs 130

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Post Sun. May. 08, 2011 4:08 pm

Berlin wrote:There are three ways to evaluate a coal's btu's, "moisture ash free", "moisture free" and "as received". if you're looking at anthracite in the 14,000btu range, it's moisture ash free. as received anthracite will average 12,000btu/lb

This is why the as received for subbit will generally be around 7-10000btu's/lb, there's more moisture in sub bit.
If you look in Table 17 I posted on the previous page, there are two columns that list BTUs. The one on the far right states Rank Btu. Two columns to the left, there is a sub heading BTU with "Coal Analysis, Bed Moisture Basis" over it. You are saying there are three ways, with this table showing two. Do you know which two of the ones you are saying are which column in this table? Are you using ASTM D407 for your definition of terms? Or something else?

I've been trying to get my hands around several aspects of coal rankings, combustion and some other things for awhile. Don't know anyone that really knows the subject...

dj

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Post Sun. May. 08, 2011 4:39 pm

I'm saying there are three common ways to measure the calorific value of coal. I don't know off-hand what the astm standards are that govern this, but I do believe that d407 is defunct. I've seen these different ways of rating a coals BTU's many times. I grew up reading coal assays before I understood what they even meant; I am no expert, but MAF, DAF, MF, and AR are four common headings in various coal analysis that I've looked at. To further complicate matters you will sometimes see MMMF which removes ash and other mineral matter. for todays purposes, just concentrate on the most common: moisture ash free MAF, moisture free MF, and As Recieved AR.

I'm not sure what that column on the right "rank btu" means, but perhaps it's a MMMF or MAF vs. the central column which is likely MF. either way, it's outdated.

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Yanche
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Post Sun. May. 08, 2011 6:36 pm

There are various calculation methods to determine the heating value in coal. They are known as the Dulong, Boie, Grummel and Davis,
and Matt and Spooner formulas each named after the author who proposed the formula. Each use the ultimate analysis of the coal, i.e. the elements of carbon, hydrogen, nitrogen, oxygen and sulphur in the coal. For example using the Dulong formula:

Heating value = 14,540 C + 61,500 (H - O/8) + 4500 S

Do some Web searches on the various formula names and you fill find lots of information.

One reference that compares the various formulas is:
Coal_Heating_Value_Formulas.pdf
(191.05 KiB) Downloaded 27 times
It's the result of DoE supported work. There are lots of references at the end for further research.

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Post Wed. May. 11, 2011 5:23 am

I think the word we are looking for is "nominal" Btu's

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Post Mon. Feb. 20, 2012 8:31 pm

Anthracite cannot be over 14500 btus if it was pure carbon. It usually has about

10% ash and 6-8% water, which equals about 12180-11890 BTU /#, then if a stove

is 80% efficient you get about 9744 BTU /#, delivered to your home.

In bituminous coal it is more complicated because some of the long chain

carbon compounds can have upward 20000 BTU /#.

The amount of gases in the coal also affect the BTU values, oxygen and nitrogen

lower the heat value.The fuel type gases like butane propane, hexane and

methane imbeded in the coal add to the heat value,as all have over 20000 btu/#.

The chemical composition of any coal can greatly increase the heat value, that's

why some bituminous have over 15000 BTU /#.

BigBarney


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