A Richland County Tale

The flames licking just above the ‘live’ or burning coal
brought the temperature of that part of the fire in excess of
two-thousand degrees! Luckily, the crownsheet had water above it;
otherwise, the intense heat concentrating on this firebox
‘ceiling’ might have melted the soft metal of the fusible
plug, allowing the pressurized steam (and water from lower down in
the boiler) to come rushing into the furnace, thereby extinguishing
the fire and possibly doing damage. Were there an
unreliable fusible plug and not water above the
crown-sheet, the entire ceiling could blow down into the firebox
and, perhaps, blast off the fire door or spawn a more menacing
explosion.

Powerful wind currents puffed and whipped through, around, and
above the coal. The five percent of hydrogen in the lump of coal
containing me began to unite with some of my fellow carbon atoms.
The temperature in the vicinity had risen to about two-thousand
degrees. Soon, the hydrogen atoms had bonded with three times their
weight of carbon and were becoming a gas. About one-fifth of my
coal-lump was thus transformed into vapor. The bonding action of
the hydrogen and carbon required a great deal of energy, and heat
in the firebox was converted into this energy. In fact, this change
of heat into energy to form chemical bonds partially cooled the
fire!

The gusts of air contained oxygen, which began to combine with
the hydrogen/carbon gas. This union meant that combustion was now
occurring. Even though the fire had cooled somewhat by the transfer
of heat into energy to form the hydrogen/carbon gas coming off the
new coal, the fire in the live coal was still hot enough to ignite
the gas. Because of this igniting temperature, the oxygen and gas
could combine which is to say that combustion could happen. (At
lower temperatures, a gas can flow along with air [containing
oxygen], and no chemical combination takes place hence, no
combustion.) The air also contained about eighty percent nitrogen,
but nitrogen does not aid in combustion and, indeed, hinders it
somewhat.

The hydrogen in the gas was more combustible than the carbon, so
it burned first. Bluish flames began to leap near me. This bonding
of hydrogen and oxygen formed water and, at the high temperature in
the furnace, this water appeared in the form of steam. As the
hydrogen in the gas was combining with the oxygen in the air, it
was released from its bond with my carbon colleagues. We carbon
atoms never allow ourselves to be in a gaseous state all alone; in
these situations, we always prefer to be gaseously combined with
other substances. As quickly as the hydrogen burned away from my
fellow carbon atoms, they formed a fine soot. At the hot igniting
temperature in the furnace, much of this soot combined with oxygen
and glowed. Each particle radiated light for only an instant; then
the carbon/oxygen combination was perfected, producing a
transparent gas. Comprised of ‘zillions’ of twinkling
carbon soot particles, the yellow flames only appeared continuous
because new carbon particles, in their turn, were released from
more of the burning hydrogen, were heated, were ignited, and glowed
for a moment. Some of the soot did not meet up with oxygen and,
therefore, did not catch fire. It was borne rapidly upward on the
wind, was carried to the front wall of the furnace, and was forced
through tubes which opened into that wall. (Smoke is nothing more
than this unconsumed soot, the ineffectual nitrogen from the air,
and the steam produced by the combination of hydrogen and
oxygen.)

As the engineer but recently had opened the firedoor to scatter
new lumps of coal (including me) on the fire, the inrush of cool
air into the furnace had lowered the temperature somewhat
especially along the edges of the firebox. In a few places, the
temperature was just a little too low for all of the particles of
carbon to ignite. Also, where the temperature was sufficiently
high, the grates, now well covered with new coal, could not
introduce enough oxygen to go around for the gases being released
from all that fresh coal. Quite a high number of my carbon
colleagues blew away as black soot not having met up with oxygen
and, hence, not having undergone combustion or not having reached
igniting temperatures. The smoke, thus, was thick at first.

May I pause in my narrative to say that many authorities ascribe
to the idea that too much smoke is an indication of a poor
engineer. In the extreme case of an engineer constantly opening the
firebox door and dumping far too much coal on a fire far too thick,
the dense smoke and the fact that the engineer can hardly keep up
steam despite his continued efforts would indicate an engineer with
little knowledge of firing a boiler. James H. Maggard put this
matter in definite and memorable terms:

[A] good fireman doesn’t make much smoke. We are now
speaking of firing with coal. If I can see smoke ten miles from a
threshing engine, I can tell what kind of a fireman is running the
engine. If there is a continuous cloud of black smoke being thrown
out of the smokestack, I make up my mind that the engineer is
having all he can do to keep the steam up; and also conclude that
there will not be much coal left by the time he gets through with
the job. While, on the other hand, should I see at regular
intervals a cloud of smoke going up and lasting for a few minutes,
and for the next few minutes see nothing, then I conclude that the
engineer of that engine knows his business. . . .We will first go
to the engine that is making such a big smoke, and we will find
that the engineer has a big coal-shovel just small enough to allow
it to enter the firedoor. You will see the engineer throw in about
two or perhaps three shovels of coal, and as a matter of course we
will see a volume of black smoke issuing from the stack. The
engineer stands leaning on his shovel watching the steam gauge, and
he finds that the steam doesn’t run up very fast, and about the
time the coal gets hot enough to consume the smoke we will see him
drop his shovel, pick up a poker, throw open the firedoor, and
commence a vigorous punching and digging at the fire. This starts
the black smoke again, and about this time we will see him down on
his knees with his poker, punching at the underside of the grate
bars; about the time he is through with this operation the smoke is
coming out less dense, and he thinks it time to throw in more coal,
and he does it. (87-88)

Maggard depicted an extremely incompetent engineer. In more
moderate situations, however, the presence of smoke does not
necessarily condemn the engineer. No matter how black the smoke may
be, it is only between a half to one and a half percent of the
carbon in the coal. To the person who assumes that smoke is
evidence of inefficiency, I would say (from personal experience)
that far greater losses occur which cannot be seen. For example,
radiation of heat not transferred to the water in the boiler is a
large waste. More significantly, much unconsumed hydrogen/carbon
gas passes through the tubes and out the smokestack with the smoke.
And these losses are by no means the only ones all of them
invisible. The careful regulation of the locations and thick nesses
of live coal and of new coal on the grates and the expert admission
of air in the right amounts and at the right time have the most to
do with efficiency.

Where was the air coming from in the firebox in which I found
myself? Front and rear draft doors permitted air to circulate
upward through the grates. In the firedoor, a vent consisting of
over half a dozen small apertures introduced air above the fire,
and this source contributed thirty percent to the total air in the
furnace. As the engine on top of the boiler was running, it was
exhausting steam in rapid bursts through a nozzle pointing upward
inside the smokestack; this action greatly enhanced the draft,
which caused the currents of wind above the fire to be best
described as ‘violent.’ Such strong wind helped to mix the
air and the gases from the coal, and that mixing ensured that more
of the gas would be ignited and consumed all for the purpose of
generating heat to boil the water under pressure in the boiler so
that the steam could power an engine.

Suddenly, the temperature in the lump of coal where I was
located reached the point where I and many other carbon atoms were
caught up with hydrogen in gaseous form. Just as quickly, the
hydrogen dropped us and formed steam with oxygen, and, in virtually
no time, I combined with two atoms of oxygen. Together, the three
of us atoms had now become carbon dioxide. Nearby, a
fellow carbon atom found only one oxygen atom to join; they formed
carbon monoxide. They generated less than one-third as
many heat-units as I and the two oxygen atoms created. In a
firebox, then, carbon monoxide is wasteful. Complete
combustion (like mine) is desired.

Although I had now been burned, I was not destroyed. I simply
existed in a new combination with oxygen. Combustion does not
destroy matter any more than it creates it. Combustion merely
transforms matter! There is a hopeful lesson in that fact!

At the instant that I and a number of my colleagues a number so
high as to be beyond imagination entered into combustion by uniting
with oxygen to form carbon dioxide, we were in a swirl of volatile
matter igniting into a long yellow flame; inside that flame was a
great deal of uninvited hydrogen/carbon gas. Flames, so to speak,
burn only on the outside. To borrow an analogy, I would explain
that a flame is like a clear current of water flowing all around
the outer surface with a muddy current going along within. Even
though terrific gusts of wind were tearing through the furnace,
they could not offer every hydrogen atom and every carbon atom
enough oxygen to burn.

Let me linger at this moment in my story to share a few
fascinating facts. It takes approximately four and a half pounds of
air to furnish one pound of oxygen. It takes 2.66 pounds of oxygen
to bring one pound of carbon into perfect combustion (forming
carbon dioxide). The complete combustion of a pound of carbon
yields 14,500 heat-units, but, when carbon monoxide is formed
(imperfect combustion), only 4,400 heat-units result. The engineer
must admit excess air into the firebox to ensure that perfect
combustion takes place most of the time. This surplus air has to be
heated to the temperature of the furnace, and part of it may not
mix when combined with the hydrogen or carbon; certainly, a portion
is wasted, carrying through the tubes and up the smokestack all
those heat-units which were spent on raising the temperature of the
unused air. Furthermore, the introduction of fresh air at, say,
seventy degrees, lowers the overall temperature in the firebox and
increases the volume of gases in the furnace and, hence, the
velocity at which the gases escape through the tubes, thus giving
the hot gases less time to communicate their heat through the tubes
to the water on the other side. Yes, it is possible to admit too
much air into the furnace. But, if the firebox were to have too
little air, imperfect combustion would occur. It takes about twelve
pounds of air to give enough oxygen for perfect combustion of one
pound of carbon under ideal circumstances, but, as reality always
differs from the ideal situation, much more air than that is
required per pound of carbon in a firebox like the one I was
occupying. A wise engineer balances the potential losses from
unused air and from incomplete combustion. (By the way, the
combustion of hydrogen yields a great heat; one pound of hydrogen
generates approximately 62,000 heat-units. But remember that the
coal with which I was associated contained only five percent
hydrogen.)

Now, to return to my tale because the engineer was talented, he
had the air well regulated. Much of the carbon monoxide which
formed among the embers arose, met more air coming in above the
fire, and became carbon dioxide by uniting with the additional
oxygen higher up. This second combustion above the fire improved
the efficiency.

After much of the gas had been expelled from the coal, the ember
was what is known as ‘coke’ (in a general sense); with the
exceptions of incombustible sand, ashes, slate particles, and
cinders, the coke was almost pure carbon, much of it directly
uniting with oxygen to form carbon dioxide. Many expert firemen
recommend spreading new coal just inside the firebox door, waiting
for the gases to burn off, pushing (with a hoe) the coke toward the
tube wall (called a fluesheet), and permitting the extra heat of
this layer of coke to give more perfect combustion to the gases
escaping overhead from the next scattering of fresh coal inside the
fire-door. This process has scientific merit, but the firedoor must
be left open a little longer to shove the coke to the back; it is
doubtful whether the improved efficiency of combustion compensates
for the air disturbances caused in this way. Also, the thickness of
the coke layer eventually works against the even combustion of the
carbon in that coke. Other authorities suggest spreading fresh coal
on one side of the firebox, allowing it to coke, then adding new
coal to the other side of the furnace; thus, a fair portion of the
gases arising from the fresh coal may enjoy increased opportunity
to burn thoroughly before being pulled through the tubes. Still
others advise keeping a very thin layer of embers throughout the
firebox (especially along the troublesome edges) and adroitly
adding new coal in any spots which are about to burn through to the
grates. This method begs for an engineer having considerable skill
at ‘reading’ a fire and at handling a small scoop in the
brief interval that the firedoor may be left open.

I had no time to ponder the coke and the pros and cons of
various means of firing the boiler, for I was now part of carbon
dioxide gas myself and was rushing toward the tubes. The uppermost
tubes fostered the greatest draft, and my fortune was to be carried
into the centermost tube at the top. Depending on the capriciously
fluctuating and forceful winds in the firebox, I could have been
thrust toward any of the thirty-eight tubes, although the draft
ordinarily pulls powerfully toward the topmost tubes. After diving
into the two-inch-diameter tube, whatever flame I had been in was
extinguished by contact with incombustible gases and by being out
of reach of sufficient air. The temperature within the tubes,
surrounded as they were by water, was too low to sponsor any
further igniting.

Down the 90 inches of tube I flew. As I was entering the
smokestack, the temperature of the stream of smoke, steam, and
gases which carried me along was just over four-hundred degrees.
Where had all the heat gone? The firebox temperature had averaged
about two-thousand degrees despite the facts that the quantity of
air in the furnace was (as it should have been) practically double
the amount theoretically necessary and that air took plenty of
heat-units to get hot. It was a good thing that the engineer had so
carefully controlled the vents admitting air above the fire and had
so quickly opened and closed the firedoor when putting in more
coal, or else the temperature could have dropped below the minimum
levels needed for igniting! (Also, were he to have left the
firedoor open any longer than essential, he could have injured the
sheet of metal into which the tubes opened by allowing such a
relatively cold blast of air to continue to strike against it.)
Anyway, I had been very hot, and now, at the point of exiting the
smokestack, I was much less hot than I had been. I and the other
gases had yielded much heat to the firebox, crownsheet, and tubes,
which had passed on a portion of that heat to the pressurized water
in the boiler. I had done my part to generate steam in that water
beyond the tubes, and that steam would run the engine. Each pound
of coal had evaporated about six pounds of water. The knowledgeable
engineer was using about four and a half pounds of coal per brake
horsepower per hour; in other words, at a load of fifty horsepower,
his engine was consuming 225 pounds in one hour.

As I was jettisoned from the smokestack, I looked down on the
large crowd of people attending the reunion of the Richland County
Steam Threshers Association at Malabar Farm State Park near
Mansfield, Ohio. They were admiring the 1917 50 HP Case which I had
just helped to run. I thought how my having been mined from that
ancient bed of coal had been worthwhile, for I and my colleagues
(my ‘carbon copies,’ you might say) had assisted in
demonstrating the important history of mechanical contributions to
the science of agriculture.

Sources

For factual information, this article relies upon many sources,
notable among them:

Boss, William The Heath Book for Threshermen. Winnipeg:
Heath, 1908. Case catalogues, parts lists, and manuals (all
reprints).

Forney, Matthias N. Catechism of the Locomotive. New
York: Railroad Gazette, 1897.

Holmes, George C. V. The Steam Engine. London:
Longmans, Green, 1900.

Kent, William. The Mechanical Engineers’
Pocket-Book. New York: Wiley, 1895.

Maggard, James H. The Traction Engine: Its Use and
Abuse. Philadelphia: David McKay, 1915.

The Power Catechism. New York: McGraw, 1897.

Rose, P. S. Steam Engine Guide. Madison: American
Thresherman, 1910.

Thurston, Robert H. A Manual of Steam-Boilers. New
York: Wiley, 1904.