TM 5-810-15
CHAPTER 3
STEAM GENERATORS
3-1. Introduction.
3-2. Boiler design.
a. General. This chapter addresses the design
a. Design. Boilers will be designed and con-
requirements for gas, oil, coal, and waste fuel fired
structed in accordance with Section 1 of the Amer-
steam generating, water-tube boilers and compo-
ican Society of Mechanical Engineers (ASME)
nents with steam capacities between 20,000 and
Boiler and Pressure Vessel Code.
b. Type. The boilers are to be natural circulation
250,000 pph and maximum pressures of 450
pounds per inch gauge (psig)/saturated and 400
and two drum design. Coal fired boilers are
psig/700 degrees F superheated.
balanced draft and gas/oil fired boilers are forced
draft.
development in combustion technology in the past
seventy years has been fluidized bed combustion.
3-3. Boiler construction options.
(1) History.
Earlier
fluidized
bed
a. Construction types. The specific type of boiler
technologies included the bubbling bed boiler.
construction will depend on the boiler size, type of
Bubbling bed boiler efficiency is similar to that of a
firing and life cycle costs. Three boiler construction
stoker boiler (80 to 82 percent). Atmospheric
types are available: shop assembled package units,
circulating fluidized bed (ACFB) boiler efficiency
field assembled modular units and field erected
is comparable to pulverized coal boiler efficiency
units.
(86 to 88 percent). Bubbling bed boilers are not
b. Package units. Package units are completely
included in this manual not only because they are
assembled before leaving the boiler manufacturer*s
less fuel efficient, but also because they are inferior
factory. For this reason, the quality of workman-
to ACFB units in the areas of sorbent utilization,
ship is generally better and the field installation
emissions reductions and fuel flexibility.
costs are considerably lower than for the modular
(2) Advantages. Fluidized bed boilers have
and field erected units. Package units covered by
gained acceptance in the industrial and utility
this manual are limited to stoker fire boilers with
sectors by providing an economical means of using
steam capacities of approximately 50,000 pph and
a wide range of fuels while meeting emissions
below, and gas and/or oil fired units of approxi-
requirements without installing flue gas desulfuri-
mately 200,000 pph and below.
zation systems, such as wet and dry type scrubbers.
c. Modular units. Modular units are too large for
(3) Emission reductions. Sulfur capture is
complete shop assembly. Some of the components,
accomplished by injecting a sorbent, such as lime-
such as the boiler furnace, superheater, boiler tube
stone or dolomite into the furnace along with coal
bank and economizer and air heater are assembled
and other solid fuels. Storage and handling of
in the manufacturer*s shop prior to shipment for
limestone must be included. Optimum sulfur cap-
final erection at the field site. Modular units should
be subject to better quality control due to
emissions are achieved by maintaining a combus-
manufacturing plant conditions. Since component
tion temperature at approximately 1550 degree F
assembly has taken place in the manufacturer*s
which is lower than other coal firing technologies.
shop, the field manhour erection time will be
Sulfur is removed as calcium sulfate in the bag-
reduced. Modular units are limited to stoker fired
house and either landfilled or sold.
boilers ranging in steam capacity from ap-
(4) Unique components. Atmospheric
proximately 50,000 to 150,000 pph.
fluidized bed (ACFB) boilers in addition to having
d. Field erected units. Field erected boilers have
components which are common to other
numerous components, such as the steam drum, the
combustion technologies (superheater, airheater,
lower (mud) drum, furnace wall panels, superheater
steam coil air preheater, economizer, sootblowers,
sections, generating tube banks, economizer and air
etc.), ACFB boilers have unique components. The
heater plus flue gas and air duct sections which are
following list of unique ACFB boiler components
assembled at the job site. Therefore, they take
is described in more detail in individual sections
longer to install than either a package or a modular
later in this chapter: lower combustor, upper
type unit. Field erected units are available from
combustor and transition zone, solids separator,
about 40,000 to 250,000 pph and, if required,
solids reinjection device, and external heat
much larger. Field erected stoker fired boilers are
exchanger (optional).
available in this size range, and pulverized coal
3-1
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