Thursday, March 20, 2014

Coal, Coke, Clinker & More

I think most persons who are doing blacksmithing feel an obligation to better inform the public about it.  Some of the most frequent questions from my visitors relate to coal.  We heated with coal in my early childhood so it always strikes me as a bit strange when some people seem so unfamiliar with it.  I answer questions about coal with essentially the same information as given in this Wikipedia clipping.

“Coal (from the Old English term col, which has meant "mineral of fossilized carbon" since the 13th century) is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon along with variable quantities of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.

Throughout history, coal has been used as an energy resource, primarily burned for the production of electricity and/or heat, and is also used for industrial purposes, such as refining metals. A fossil fuel, coal forms when dead plant matter is converted into peat, which in turn is converted into lignite, then sub-bituminous coal, after that bituminous coal, and lastly anthracite. This involves biological and geological processes that take place over a long period.

Usually, there is some coke on the forge pan left over from the last forging session and by look and feel visitors can discern the difference between the two.  The coal is heavier, shiny and rock-like while the coke is more like a black marshmallow or a piece of lump charcoal, dull and light weight.  It’s a bit hard to imagine that the difference could have come just from driving off entrapped volatile gases.  The coke is composed of the residual carbon and ash.

Often, they are unfamiliar with clinker.  Once again the clinker from the last fire is usually still lying on the forge pan so they can take a look at it too.  Seldom, do they notice the pile of fly ash inside the smoke chamber of the flue unless I point it out to them.

There doesn’t seem to be a lot of information about clinker on the web but I found this reference is how some of the clinker from blast furnaces is used in making concrete.

I rarely clean the fly ash which has accumulated in my side draft forge 

Soft Coal


Fly ash in the smoke collector, clinker in the fire pot and coke on the pan.

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