Page 42 - Boiler Operator’s Handbook

Operating Wisely 27

C + O => CO the formulas that one oxygen molecule produces only
2 2
+ 14,096 Btu for each pound of carbon burned. one molecule of CO and two of CO. There’s another
2
natural rule that says all molecules at any particular
2H + O => 2 H O pressure and temperature take up the same amount
2 2 2
+ 61,031 Btu for each pound of hydrogen burned of space. Since we double the number of flue gas mol-
ecules when we make CO the gas volume increases.
S + O => SO The increased gas volume produces more pressure drop
2 2
+ 3,894 Btu for each pound of sulfur burned through the boiler which restricts flue gas flow out.
Since the gas can’t get out as fast, less air can get in and
2C + O => 2CO there’s less oxygen so we make more CO. The result is
2
+ 3,960 Btu for each pound of carbon burned a generous generation of CO until the heat input has
dropped to where there’s a balance between the pres-
C is Carbon, one atom sure drop from more CO and the reduced generation
CO is a molecule of carbon monoxide, containing two atoms of CO as the air input is decreased. Try it some time…
CO is carbon dioxide, one molecule containing three atoms carefully. Just decrease your air or increase your fuel at
2
H is a molecule of hydrogen, consisting of two atoms a constant firing rate and watch the steam flow meter.
2
H O is a molecule of water, consisting of three atoms When the CO starts forming you’ll see the steam flow
2
O is a molecule of oxygen, consisting of two atoms drop off.
2
S is an atom of sulfur Maybe it’s a little late, but I think this is a great
SO is a molecule of sulfur dioxide, three atoms time to discuss how fuels are produced. It’s because the
2
methods used in creating those fuels are partially occur-
The rules of the equations are rather simple. You ring in our fire in our boiler and by talking about both
have to have the same number of atoms on both sides of at the same time it may make more sense why I would
the equation. Try counting and you’ll see that’s the case. insist you know how some fuels are made. Coal is not
You see, we don’t destroy anything when we burn it. It’s necessarily made but is simply dug up and transported
one of the natural laws of thermodynamics that’s called to the boiler plant right? Not really, some of it is put
the law of conservation of mass. It may appear that the through a water washer, some of it is treated by expo-
wood in the campfire disappeared but the truth is that it sure to superheated steam, and a small amount of it is
combined with the oxygen in the air to form gases that ground up fine and mixed with fuel oil to create another
disappeared into the atmosphere along with the smoke. fuel. Natural gas and fuel oil also go through prepara-
Every pound of carbon is still there. It’s just combined tion processes. Natural gas is normally put through a
with oxygen in the CO and CO . I know it doesn’t make scrubber after it’s extracted from the ground to remove
2
sense that we get energy without converting any of that excess carbon dioxide and sulfur compounds.
matter to the energy but that’s the case. At least nobody For all practical purposes the gas flowing up
has been able to find a difference in weight to prove it. the large pipelines from Louisiana and Texas to all us
You’ll also notice that we don’t get much heat from consumers on the east coast doesn’t have any sulfur in
the carbon when we make CO. That’s one sure way to it to speak of. If it did the sulfur might react with the
know you’re making any significant amount of it. When oils in the big compressors the pipeline companies use
I was sailing, we sort of used that fact to tune the boilers. to pump the gas north and make those oils acid. Once
Once we were at sea we pushed the boilers to generate the gas arrives at a gas supplier in the northeast sulfur
as much steam as possible to turn that propeller with the is added back into the gas in the form of mercaptans,
turbines. Every rotation of that big screw got us 21 feet chemical compounds that give gas its odor so we can
closer to Europe or 21 feet closer to home, depending detect leaks. Those mercaptans contain sulfur.
on which way we were going, and the more rotations Fuel oil whether it’s number 1 (kerosene), 2 (die-
we got the faster we got there. We would push the fans sel), or any of the heavier grades (4, 5 & 6) all come from
wide open then increase fuel until we noticed our speed crude oil, the oil that’s pumped from the earth or gushes
wasn’t increasing. Usually what happened is the speed when it’s under pressure. The crude oil is “refined” in a
would drop off. That was a sure indication we were refinery to separate the different fuels, and a lot more,
making CO so we would back off on the fuel a little and from the material that comes out of the ground. One big
that was the optimum point for firing. fraction of crude oil is gasoline. In fact there is such a big
Why did the speed suddenly drop off? Notice in demand for gasoline that some of the other products are