In his articles John R. Crosby refers to "gas coal". What is it?
Simply a guess, but I believe that gas coal is an informal term for coal that includes a lot of volatile material. It may have a higher heat value.
I don't know the articles you refer to, but as long as we are guessing -- my guess is that gas coal would be coal particularly well suited to making "coal gas" which was the gas used for lighting and cooking before the widespread use of "natural gas." I believe the process involved heating coal in an oxygen free environment, which would release the gases contained in coal. Those gasses would be captured and retained in the large cylindrical structures you used to see in large cities (I can recall seeing them as a boy). They were actually two part structures and as more gas was added the top part would rise so in photos of the same structures they are often of different heights. Water was used to keep the gas from escaping. The remains of the heated coal was then coke which had (and still has) its own uses.
If my guess is correct then gas coal would be coal rich in gas and thus desired by the processing plants that manufactured coal gas.
Or I may be all wet. Wouldn't be the first (or last) time.
Dave Nelson
CSSHEGEWISCH is, I think, correct in this context - in fact, I believe the PRR term is 'passenger gas coal' (as opposed to the glorified slack that PRR often used for freight, and that produced the profuse soot that the T1's deflicted aerodynamics carried down into the cab for the minstrel show.
It may have a somewhat higher heat value (even though more carbon = more overall heat content in most solid fuels) but the real 'key' is more in how quickly the heat could be liberated from a given mass of it. At high firing rates, there was insufficient time of flight for carbon particulates to reach reaction temperature, even with relatively high flame temperature (the waterwalls are fairly effective absorbers of IR with relatively cold water behind them), and then react completely to either CO (as in some forms of GPCS) or CO2, given the near-reducing atmosphere toward the front of a conventional firebox without effective secondary-air circulation or 'jets'. If you evolve volatiles, ignite them, first to get the hydrogens off and then react with relatively small and exposed amounts of carbon 'backbone', and thereby go to completion quickly, you might also provide extra energy to get the larger carbon particles 'lit off' faster. Or so I understand it, simplistically.
"+ 1" as to "passenger gas coal" & the first paragraph; I don't know enough about the technical part to comment on the second para., but it seems reasonable to me.
I'm not sure where I learned or figured this out. If not from one of Crosby's articles, then it likely was from one of Lloyd Arkinstall's articles which appeared in Trains in about the same time frame, though the events were a few years before Crosby's. Whichever it was, I recall the description was something like "hot enough to melt Hell's hinges"; it was kind of like premium gasoline vs. regular.
- Paul North.
In Rev. W. Audrey's original "Thomas the Tank Engine" books, Henry the Green Engine was cured by getting a Belpaire firebox and better coal. Maybe the PRR knew something...
Thanks for your help!!
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