Percent Ash Calculation

See some folks on here have listed the percentage of ash of the coal they have burned and was wondering at how they were arriving at their figures. Are people just burning a bag of coal and then weighing the ash generated from a bag and calculating the coals ash content or is there a better mouse trap for figuring this?

I assume by calculating your ash content you can get an idea of the quality of the coal you have purchased - would this be correct?

The coal mine will usually tell you the % of their coal. I think it's done in a lab & is only a general idea for comparison value. You won't get the same % in actual use.

I don't think the amount of ash tells you the quality.

I think commonly the coal is weighed, burned and then the ash is weighed. It would seem more ash would mean less BTU's per pound, but then I know very little about such things...

usually but not always, more ash is less btu/lb. ash % is done by weight, not volume, so coal that has "low ash" may not always be percieved as so when one views their ash pile, but it's not measured by volume, I've had coals with almost twice the volume of ash, but they're the same % by weight.

I've been surfing for good engineering data on coal composition and one of the things that confuses me is the percentage of ash data. By good engineering data I mean data that comes from an independent engineering testing lab, not just some marketing BS. For example there is a large text file posted on the EPA's web site that gives laboratory testing data submitted for regulatory purposes. There is actual data from Superior Coal! It lists the ash content as 25.79%. Now this is far higher than my experience and J.C.'s postings. The testing laboratory was PP&L System Chemical Laboratory, Hazleton, PA. One can only assume the testing laboratory knows what it's doing.

What's going on? Is the testing method used by testing laboratories different than that used by coal companies? The Bituminous coals listed in the EPA data have much lower ash content. The data was from 2002. I can dig up the direct link if you are interested. It's a huge text file that I imported into Excel. What's listed below is a small portion of the Superior entry. I've merged the column headings and the data so you have a clue as to what the numbers mean.

Anyone have access to the actual ASTM test procedures?

Engineering data from the report (Superior #5) follows:

Amount - The amount of coal that the analysis represents in dry tons.
Data = 491

Sulfur - Total sulfur is the sulfur content of the coal/fuel sample, by percentage (dry basis).
Data = 0.6

BTUlb - The higher heating value of the coal/fuel sample, Btu/lb (dry basis).
Data = 9764

Ash - The ash content of the coal/fuel sample, by percentage (dry basis).
Data = 32.32

Mercury - The mercury content of the coal/fuel sample, in ppm (dry basis).
Data = 0.22

NRMercury - Marks that the analysis results are below the detection limit in the mercury data field.
Data = FALSE

Chlorine - The chlorine content of the coal/fuel sample, in ppm (dry basis).
Data = 456

NRChlorine - Marks that the analysis results are below the detection limit in the chlorine data field.
Data = FALSE

ObtainM - The specific method(s) used by your electric utility company to obtain the coal/fuel sample (e.g., ASTM...).
Data = ASTM D2234

PrepareM - The specific method(s) used by the testing laboratory to prepare the coal/fuel sample for analysis of mercury (e.g., ASTM...).
Data = ASTM D346

AnalysisM - This item is the specific method used by the testing laboratory to analyze the coal/fuel sample for mercury (e.g., EPA Method...).
Data = ASTM D3684

AccPrecHG - Any evidence of accuracy and precision of analysis for mercury.
Data = ASTM 1630a Std.(0.106) - Analysis (0.107)

I haven't been following, but did read the last post.
For your consideration: There is a percentage of ash "by volume" and also a percentage of ash "by weight".

I had some gray ash coal, which was a smaller percentage by volume (fine ash) and I had some red ash coal, which was a higher percentage by volume (ash about the same size as the unburnt coal). The weight of the ash for the same amount of coal, could be about the same for both.??

One other consideration: I believe the red ash coal was lighter in weight, than the gray ash coal for the same volume. (a bucket full of the red ash ash coal weighed less than a bucket full of the gray ash coal). (or pick-up load)

Edit: One more consideration and probably the most important, percentage of ash, as compared to BTU output. I'm guessing, this will be a direct relationship to the density factor of the coal. ??

At work we use a common book called "Boilers Operator's Guide" 4th edition. On pg 417 I see Pennsylvania anthracite coal proximate analysis as 13,000 btus/lb, 2% moisture, 6.3% volatiles, 79.7% carbon and 12% ash.

I've been calculating my % ash by weight and I'm getting consistantly high numbers of 20%. I burn bagged rice coal and here's how I calculate it. I fill my hopper to the top, emptying the ash pan. Next day (24hrs.) later I use a house scale (not the most accurate) to weigh the coal to fill the hopper to the top, then weigh the ash/pan. So, if my math is right
%wt. ash = (wt. ash/pan - wt. ash pan) / (wt. coal)

Can anyone tell me if I'm doing something wrong? Not sure if it's operational error, calcualtion error or the coal, but I'm getting 20% ash consistanly.

Your procedure looks OK to me. I don't believe all PA Anthracite is "created equal", so I don't know how they can come up with general numbers for all PA Anthracite. One of the guys has posted numbers for the different coals of the region.

I burn mostly Bit coal but tried some anthracite in November,and here are my results:

Total coal burned: 1758#

Total ash: 239# ------------- Overall Ash: 13.6 %

1) ** Types of coal: Pittsburgh Bit (930#) & Valier House (nut/pea mix) (548#)

Quantity Burned: 1478#-------------- 84%

Ash: 198#

Ash % : 13.39 %

2) ** Type of coal: Blaschak Nut Anthracite

Quantity Burned: 280#-------------- 16%

Ash: 41#

Ash % : 14.64 %

I weigh all coal in and all coal ash out on the same scale for accuracy,so the ash results are even @ 13.6 %.

At month end all of what ever fell out(when cleaning) were was added to the ash totals by 84/16%.

Any burnable coal was returned to the fire in the next fill.

The heating load in degree days was : 677 (using Erie Pa as basis)

About 2.6# per degree day for heat and hot water.

We heat 2000 sq ft to 70-75* and the basement is at 62-70* about 1000 sq ft.

I heat with a boiler and have a zone valves for each floor.

The Anthracite coal burns to a crispy tan/brown ash and the Bituminous burns to a fine powdery gray/

white ash.

BigBarney

http://www.astm.org/DATABASE.CART/HISTORICAL/D3174-00.htm

looks like the astm procedure for determining ash is D3174-00

Thanks for all the cool info!

The other day my AHS buddy & I compared ashes. We both emptied at the same time & 24 hours later compared. Our ashes were equal by volume, each made 3/4 of a 10 quart pail. His Kimmel pea ashes weighed 5.6 pounds, my Superior pea ashes from the AA weighed 8.4 pounds. We do not know the weight of the coal that was burned, but guessing around 40 pounds.

Dallas- Thanks for the response. I'm not sure how they get those numbers..I guess they take averages for the region. Interesting the book lists different average BTU values for Ohio versus PA Bituminous coal.

Freddy- I'm getting similar ash percentages..about 20%. Except this morning I hit a record high of 24% ash.