Page 47 - Boiler Operator’s Handbook

32 Boiler Operator’s Handbook

more efficiently than a low pressure boiler when the station. Usually 80% of the energy in the fuel a simple
feedwater temperature is less than the saturation pres- boiler plant uses is converted to useful energy in the
sure of the heating boiler. A typical central plant in an facility; less than 40% of the energy in a conventional
institution will have 227°F feedwater to cool the flue utility steam plant gets converted to electricity. All facili-
gases but local heating boilers will be about 238°F. Since ties that dumped their central plants for a multitude of
the flue gases can be cooled more by the high pressure little boilers also dumped their ability to make power
plant the central plant boiler efficiency will be higher. economically.
Add to the higher efficiency of a central plant the Distributed generation is a new buzzword that ba-
ability to burn oil as well as gas and the purchasing price sically means electricity is generated in many locations
advantage for the fuel, the most expensive cost when (instead of large centrally located power plants that are
operating a plant, is also lower. Today’s time of use usually long distances from the users of the power). By
pricing has almost eliminated the deals we got for inter- having several small plants distributed throughout an
ruptible gas. In the 1990’s when firm gas was about $5 a area transmission lines lose less power and don’t have
decatherm interruptible gas was about $3.50. You could to be so big.
save 30% on the price of gas by allowing the supplier to
call for you to stop burning that fuel at any time. The
ability to burn fuel oil allowed you to take advantage ELECTRICITY
of an interruptible gas contract. Today it’s not interrupt-
ible, but you pay a much higher price than oil when gas If there’s anything that boiler operators pretend to
is in short supply. know nothing about it’s electricity. I have met several
Running fuel oil supply and return piping to a boiler operators that would send for an electrician to
lot of local boilers is usually abandoned as a first cost change a light bulb. To choose to know nothing about
savings. Besides, who will be around to switch them? it is to doom yourself to becoming a janitor, with pay to
There are automatic controls for switching fuels but the match. Not only are we in an age where electricity pow-
geniuses that decide to abandon a central plant must be ers our controls but we’re coming into the age of distrib-
afraid of them. With time of use prices someone needs uted generation where every decent sized boiler plant
to compare them for oil and gas to decide when to fire will be generating electricity. It’s essential that the boiler
oil. In the winter of 2001 I had a customer capable of fir- operators of tomorrow know enough about electricity
ing oil that fired gas at prices of $10 to $11 a therm when to use it, generate it, and occasionally troubleshoot a
oil cost only about $7.50; they burned up a difference circuit.
in less than two months that would have paid a boiler The current trend is toward engine and gas tur-
operator’s salary for a year. The only way a central plant bine cogeneration. That’s where the fuel that’s normally
can cost more to operate than a lot of local boilers is if burned in the boiler is fired in the engine or gas turbine
the heat loss from the distribution piping is excessively instead. The engine or turbine generates electric power
high. However, it takes a lot of quality installed distri- and the steam or hot water is generated by the heat from
bution piping to produce enough heat loss to justify a the exhaust of the engine or turbine.
lot of local boilers. If your management is considering Some visionaries like to think we’ll all be running
shutting down your central plant lend them this book so with fuel cells in the future. Fuel cells generate electric-
they can ask the right questions of whoever is pushing ity by reversing the electrolysis process. I trust you’ll
for it. remember that day in chemistry lab in high school
I was always encouraging customers to install boil- when you put two wires into water with an inverted
ers in their central plants with higher pressure ratings. test tube over each and watched gases form at the ends
The cost differential for a boiler capable of operating at of the wires with the bubbles rising to collect in the test
600 psig instead of 150 psig is not that great compared tubes? That was electrolysis, breaking water down into
to the value of the potential for adding a superheater its two elements, hydrogen and oxygen. A fuel cell com-
and converting the boiler for generating electricity later. bines hydrogen and oxygen to form water and generate
Very few chose to heed those suggestions and today electricity. Heat is also generated in the process and
they’re regretting it because distributed generation is that’s what would be used to generate our steam and
the big thing. A plant that generates power with the hot water. Fuel cells have advantages like no moving
same steam that’s used in the facility produces that elec- parts, other than fuel and cooling fluid pumps, so they
tricity at a fraction of the cost of an electric generating are very reliable. We might all be using them today if