Everything You Ever Wanted To Know About COAL And More

by Albin Drzewianowski

As blacksmiths many of us use coal as the heat source for our blacksmithing. Most of us are pretty limited in what we know about that coal. We know there is hard coal and soft coal. We know that there are specific types of soft coal that are more "blacksmith friendly" than other coals. But most of us don't know why. Hopefully this short article will shed some light on what coal is, where it comes from , and why it behaves the way it does.

Simply put, coal is a combustible organic rock composed principally of consolidated and chemically altered vegetal remains. Coal comes from the plants that grew in large coastal swamps. Over time that material was compressed at the bottom of the swamps forming a series of fuels we now know as peat, soft and hard coal. In a nutshell, coal is fossilized plant material. It has harnessed the sunlight from hundreds of millions of years ago and concentrated it into the material we can burn to generate heat today.

Coal is broken down into 4 classes and within each class there are a number of groups:

• ANTHRACITE
  • Meta-anthracite
  • Anthracite
  • Semi-anthracite
• BITUMINOUS
  • Low-volatile bituminous
  • Medium-volatile bituminous
  • High-volatile A bituminous
  • High-volatile B bituminous
  • High-volatile C bituminous
• SUB-BITUMINOUS
  • Sub-bituminous A
  • Sub-bituminous B
  • Sub-bituminous C
• LIGNITIC
  • Lignite
  • Brown coal

Off the top end of this chart the coalification process terminates with non-combustible mineral carbon or graphite.

The next question is how does all that decaying plant material at the bottom of swamps millions of years ago, end up in such a wide variety of coal types?? It is the interplay of two geological process: compaction and condensation which gives us the variety of coal types. Compaction is a physical process which results in a loss of pore space, moisture and oxygen. Condensation is a chemical process which results in an increase in residual carbon. These changes increase the density and heat value of the coal. In other words more compactions with less condensation gives one type of coal, less compaction with more condensation gives another, and so on. If I understand the process correctly, maximum compaction and maximum condensation results in meta-anthracite leading to graphite. Then I guess, with enough compaction you eventually end up with diamond.

For comparison purposes, 1 ton of coal with an average of 11,000 BTUs (which is a little low for blacksmithing coal) contains the same energy as 22,000 cubic feet of natural gas, or 158 gallons of fuel oil, or one cord of seasoned hardwood.

Enough geology. What does this all mean to us as blacksmiths. Because of the characteristics we are looking for, high heat value, coking, clean burning, the best blacksmithing coal falls in the low-volatile and medium volatile bituminous coal range.

The next question is how can we identify this optimum coal???

In today's coal industry, there are certain standard analytic tests which are used to differentiate various types of coal. These result in a standard set of numbers which a coal supplier should provide you on request when you go to buy coal.

These are:

• Moisture Content -. Expressed as a percentage. You want as low a number as possible. Since we buy coal by weight, if this number is high, you are just paying for water.
• Ash Content - A reflection of the inorganic content of the coal. Expressed as a percentage. You want as low a number as possible. The higher this number, the more clinker you get.
• Sulfur Content - Expressed as a percentage. You want as low a number as possible.
• BTU - (British Thermal Units) Heat value per pound of coal. You want as high a number as possible.
• Volatiles - Expressed as a percentage . Amounts of gases and tars, again, as low a number as possible. If you have ever used a coal that generated a black tarry "foam" as it was coking up, this coal was high in "volatiles".
• Carbon - Expressed as a percentage. You want as high a number as possible the more carbon, the more heat per unit weight or volume.
• Free Swell Index / Coke Button - This relates to coke formation. The higher the number the better. This indicates the amount of carbon available to generate heat in the forge, as compared to carbon in the gases and tars which just goes up the smoke stack.

Not all coal analysis's always have all of the above listed characteristics. In my research I often ran across coal descriptions that did not include the moisture content or the Free Swell Index.

Here are a set of good numbers to use for comparison purposes. If you run across a coal that has numbers similar to the ones below, you should have a good to great blacksmithing coal.

Name of Coal	Pocahontas No. 3	Pocahontas No. 3	Sewell
Type of Coal	Low volatile bituminous	Low volatile bituminous	Medium volatile bituminous
State where mined	West Virginia	Pennsylvania	Pennsylvania
Moisture	-	-	1.82%
Ash content	7.44%	4.6%	3.66%
Sulfur content	0.64%	0.74%	0.46%
BTU	14,542 BTUs	15,006 BTUs	15,075 BTUs
Volatiles	15.70%	18.31%	27.29%
Carbon content	92.42%	90.61	88.71
Free Swell	-	-	-

Finally, lets take a moment to talk about "POCHANTAS". There is a lot of misinformation about this word circulating in the blacksmith world. Many think it is a particular mine. Others say that the "POCHANTAS" mine has closed down and there is no more "POCHANTAS" coal available etc, etc. In fact, "POCHANTAS" is a river of coal that runs from Kentucky, up through West Virginia and ends in Pennsylvania, near Pittsburgh. In the coal industry that river of coal is broken down into 10 distinct seams: Pocahontas #1 -#9 and Pocahontas #3-rider. According to one source I found, there are something like 30-40 different mines which are tapping into "POCHANTAS" coal. So as you can see by the chart above, there is a lot of Pocahantas No. 3 coal out there and it can differ depending on its source. But in general, it will be good blacksmithing coal.

-- RebStaup - 25 Jan 2008